DBV Technologies (DBVT) 20-F 16 Mar 18 2017 FY Annual report (foreign) Financial data

Document and Entity Information

Document and Entity Information	12 Months Ended
	Dec. 31, 2017shares
Document - Document and Entity Information [Abstract]
Document Type	20-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	DBVT
Entity Registrant Name	DBV TECHNOLOGIES S.A.
Entity Central Index Key	1,613,780
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	24,990,822

Consolidated Statements of Fina

Consolidated Statements of Financial Position - EUR (€)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Non-Current assets
Intangible assets	€ 123,000	€ 96,000	€ 94,000
Property, plant, and equipment	17,808,000	12,482,000	5,581,000
Other non-current financial assets	3,012,000	2,745,000	2,711,000
Total non-current assets	20,942,000	15,323,000	8,387,000
Current assets
Inventories	0	0	0
Customer accounts receivable and related receivables	1,265,000	1,250,000
Other current assets	17,721,000	14,454,000	11,512,000
Cash and cash equivalents	137,880,000	256,473,000	323,381,000
Total current assets	156,865,000	272,177,000	334,893,000
TOTAL ASSETS	177,807,000	287,500,000	343,280,000
Shareholders' equity
Share Capital	2,499,082.20	2,465,000	2,421,000
Premiums related to the Share Capital	406,709,000	405,882,000	403,910,000
Reserves	(131,592,000)	(50,968,000)	(39,580,000)
Net (loss)	(147,693,000)	(114,531,000)	(44,674,000)
Total shareholders' equity	129,923,000	242,849,000	322,076,000
Non-current liabilities
Long-term financial debt	1,825,000	4,049,000	4,693,000
Non-current provisions	1,260,000	853,000	490,000
Other non-current liabilities	8,869,000	10,746,000
Total non-current liabilities	11,954,000	15,649,000	5,183,000
Current liabilities
Bank overdrafts	0	0	0
Short-term financial debt	2,325,000	591,000	149,000
Current provisions	913,000
Supplier accounts payable	16,941,000	13,720,000	10,034,000
Other current liabilities	15,751,000	14,692,000	5,838,000
Total current liabilities	35,930,000	29,002,000	16,021,000
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	€ 177,807,000	€ 287,500,000	€ 343,280,000

Consolidated Statements of Inco

Consolidated Statements of Income (Loss) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating income
Revenues			€ 202
Other income	€ 11,909	€ 9,084	5,964
Total income	11,909	9,084	6,166
Operating expenses
Cost of goods sold			(128)
Research and development	(105,232)	(78,828)	(34,234)
Sales and marketing	(15,824)	(11,282)	(491)
General and administrative	(35,837)	(35,005)	(16,859)
Total expenses	(156,892)	(125,115)	(51,712)
Operating (loss)	(144,983)	(116,031)	(45,546)
Financial revenues	616	1,516	1,018
Financial expenses	(3,325)	(16)	(146)
Financial profit (loss)	(2,709)	1,500	871
Income tax	(1)	0
Net (loss)	€ (147,693)	€ (114,531)	€ (44,674)
Basic/diluted (loss) per share (€/share)	€ (5.97)	€ (4.68)	€ (2.08)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of comprehensive income [abstract]
Net (loss)	€ (147,693)	€ (114,531)	€ (44,674)
Actuarial gains and losses on employee benefits, net of corporate tax	(177)	(249)	166
Profit (loss) directly recognized in shareholders' equity	(177)	(249)	166
Other comprehensive (loss) income	3,280	(743)	(90)
Total comprehensive (loss)	€ (144,590)	€ (115,523)	€ (44,598)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of cash flows [abstract]
Net (loss) for the period	€ (147,693)	€ (114,531)	€ (44,674)
Reconciliation of the net (loss) and the cash used for operating activities:
Amortization and provision	2,926	1,349	1,073
Retirement pension obligations	230	115	125
Expenses related to share-based payments	30,781	34,353	10,419
Other elements	130	147	296
Operating cash flows before change in working capital	(113,626)	(78,566)	(32,761)
Inventories			124
Customer accounts receivable	3	(1,250)	136
Other current assets	(3,458)	(2,931)	(4,870)
Supplier accounts payable	3,333	3,645	8,236
Other current and non-current liabilities	(566)	19,564	2,372
Change in working capital requirement	(687)	19,028	5,998
Net cash flow used in operating activities	(114,314)	(59,538)	(26,763)
Cash flows used in investing activities:
Acquisitions of property, plant, and equipment	(7,246)	(7,992)	(4,360)
Acquisitions of intangible assets	(299)	(215)	(148)
Acquisitions of non-current financial assets	(289)	(93)	(839)
Net cash flows used in investing activities	(7,834)	(8,300)	(5,347)
Cash flows provided by financing activities:
Increase in conditional advances			865
(Decrease) in conditional advances	(578)	(275)	(192)
Treasury shares	(25)	(54)	(175)
Capital increases, net of transaction costs	861	2,016	240,538
Other cash flows related to financing activities	28	(21)	(21)
Net cash flows provided by financing activities	286	1,666	241,014
(Decrease) / Increase in cash	(121,863)	(66,172)	208,904
Net Cash and cash equivalents at the beginning of the period	256,473	323,381	114,555
Impact of exchange rate fluctuations	3,269	(735)	(78)
Net cash and cash equivalents at the close of the period	€ 137,880	€ 256,473	€ 323,381

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholder's Equity - EUR (€)	Total	Share capital [Member]	Share premium [Member]	Reserve [Member]	Profit (loss) [Member]
Beginning balance at Dec. 31, 2014	€ 115,445,000	€ 1,916,100	€ 163,876,800	€ (26,336,000)	€ (24,012,000)
Balance as of January 1, 2015 at Dec. 31, 2014		19,160,661
Net (loss)	(44,674,000)				(44,674,000)
Foreign exchange translation	(90,000)			(90,000)
Profit (loss) directly recognized in shareholders' equity	166,000			166,000
Total comprehensive (loss)	(44,598,000)			76,000	(44,674,000)
Allocation of prior (loss)				(24,012,000)	24,012,000
Increase in capital	240,396,000	€ 504,000	239,892,000
Increase in capital, shares		5,044,468
Treasury shares	273,000			273,000
Issue of share warrants	142,000		142,000
Share-based payments	10,419,000			10,419,000
Ending balance at Dec. 31, 2015	322,076,000	€ 2,420,500	403,910,400	(39,580,000)	(44,674,000)
Balance as of December 31, 2015 at Dec. 31, 2015		24,205,129
Net (loss)	(114,531,000)				(114,531,000)
Foreign exchange translation	(743,000)			(743,000)
Profit (loss) directly recognized in shareholders' equity	(249,000)			(249,000)
Total comprehensive (loss)	(115,523,000)			(992,000)	(114,531,000)
Allocation of prior (loss)				(44,674,000)	44,674,000
Increase in capital	1,439,000	€ 44,000	1,395,000
Increase in capital, shares		443,699
Treasury shares	(74,000)			(74,000)
Issue of share warrants	577,000		577,000
Share-based payments	34,353,000			34,353,000
Ending balance at Dec. 31, 2016	242,849,000	€ 2,464,900	405,882,500	(50,968,000)	(114,531,000)
Balance as of December 31, 2015 at Dec. 31, 2016		24,648,828
Net (loss)	(147,693,000)				(147,693,000)
Foreign exchange translation	3,280,000			3,280,000
Profit (loss) directly recognized in shareholders' equity	(177,000)			(177,000)
Total comprehensive (loss)	(144,590,000)			3,103,000	(147,693,000)
Allocation of prior (loss)				(114,531,000)	114,531,000
Increase in capital	571,000	€ 34,000	536,000
Increase in capital, shares		341,994
Treasury shares	23,000			23,000
Issue of share warrants	290,000		290,000
Share-based payments	30,781,000			30,781,000
Ending balance at Dec. 31, 2017	€ 129,923,000	€ 2,499,100	€ 406,709,300	€ (131,592,000)	€ (147,693,000)
Balance as of December 31, 2015 at Dec. 31, 2017	24,990,822	24,990,822

The Company

The Company	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
The Company	Note 1: The Company Incorporated in 2002 under the laws of France, DBV Technologies S.A. (“DBV Technologies,” or the “Company”) is a clinical-stage specialty biopharmaceutical company focused on changing the field of immunotherapy by developing a novel technology platform called Viaskin. The Company’s therapeutic approach is based on epicutaneous immunotherapy, or EPIT, a proprietary method of delivering biologically active compounds to the immune system through intact skin using Viaskin. The Company’s lead product candidate, Viaskin Peanut, has completed a global Phase III program for the treatment of peanut-allergic patients four to 11 years of age. In February 2018, the Company announced that the U.S. Food and Drug Administration, or FDA, agreed that the available efficacy and safety data for Viaskin Peanut supports the submission of a Biologics License Application, or a BLA, for the treatment of peanut allergy in children four to 11 years of age. The FDA provided written responses to the clinical pre-BLA The Company is developing its second product candidate, Viaskin Milk, for the treatment of cow’s milk protein allergy, or CMPA, in children two to 17 years of age, which received fast track designation from the FDA in September 2016. In November 2014, the Company initiated a multi-center, double-blind, placebo-controlled, randomized Phase I/II dose-finding trial to study the safety and efficacy of Viaskin Milk in 198 patients with Immunoglobulin E, or IgE, mediated CMPA, which the Company refers to as the Milk Efficacy and Safety, or MILES, trial. In June 2015, we announced completion of Part A of the MILES study, or Phase I, and we launched Part B, or Phase II, in October 2015. In February 2018, the Company announced preliminary results from Part B of the MILES study. Following analyses of the data, the 300 µg dose was identified as the dose with the greatest observed clinical activity for children (intent-to-treat, In February 2015, the Company announced the development of a third product candidate, Viaskin Egg, for the treatment of patients suffering from hen’s egg allergy. Preclinical development for Viaskin Egg commenced in the first half of 2015 and is currently ongoing. In addition to our development programs in food allergies, we are exploring the use of our Viaskin technology for the treatment of inflammatory and autoimmune diseases with high unmet medical need. Human proof-of-concept Main events in 2017 1. PARTNERSHIPS On March 30, 2017, the Company, BioNet-Asia (BioNet) and Geneva University Hospitals (HUG) announced results from a Phase I trial assessing Viaskin rPT’s ability to boost immunity against pertussis by epicutaneously administering two doses of BioNet’s recombinant pertussis toxin. After further analysis of the data, limitations in study design and protocol were observed. In collaboration with HUG and BioNet, the Company is continuing to review preliminary study data, and is evaluating if further development pathways, including optimization of Viaskin rPT, will be explored. 2. CLINICAL PROGRAMS On February 3, 2017, the Company announced completion of enrollment in SMILEE (Study of Efficacy and Safety of the Viaskin MILk in Milk Induced Eosinophilic Esophagitis in Children), a Phase IIa investigator-initiated clinical trial at the Children’s Hospital of Philadelphia (CHOP), assessing the safety and efficacy of Viaskin Milk for the treatment of milk-induced Eosinophilic Esophagitis (EoE) in approximately 20 patients four to 17 years of age. The Company expects CHOP to release results for the SMILEE study in the first half of 2018. On March 10, 2017, the Company announced completion of enrollment of patients in REALISE, a multicenter, randomized 3:1, double-blind, placebo controlled Phase III trial, which randomized 393 patients in 32 centers across North America. On August 2, 2017, the Company announced the initiation of EPITOPE (EPIT in Toddlers with Peanut Allergy), a Phase III clinical trial assessing the safety and efficacy of Viaskin Peanut for the treatment of peanut-allergic patients one to three years of age. On August 29, 2017, the Company announced the completion of enrollment of patients in PEOPLE (PEPITES OPen Label Extension Study), an open-label extension study of PEPITES. On October 20, 2017, the Company announced topline results from PEPITES (Peanut EPIT Efficacy and Safety), a privotal Phase III trial designed to evaluate the efficacy and safety of Viaskin Peanut in patients four to 11 years of age. In November 20, 2017, the Company announced topline safety results from REALISE and that the trial met its primary objective, observing that Viaskin Peanut was well-tolerated with no new or unexpected adverse events. A favorable safety and tolerability profile was observed, which was comparable with outcomes from previous studies of Viaskin Peanut 250 µg. 3. CHANGE IN THE GROUP’S EXECUTIVE COMMITTEE MEMBERSHIP AND BOARD MEMBERS On March 14, 2017, Laurent Martin was appointed the Responsible Pharmacist by the Board of Directors. On June 15, 2017, the Company announced the appointment of Julie O’Neill to its Board, effective immediately pursuant to her election at the Company’s ordinary shareholders’ general meeting. Ms. Julie O’Neill is expected to serve on the Board for two years. With this addition, the Company’s Board was comprised of eight directors. On November 17, 2017, George Horner III tendered his resignation from his duties as a member of the Board and the Audit Committee and as Chairman of the Compensation Committee. The Board appointed Daniel Soland as a member of the Audit Committee, Torbjörn Bjerke as Chairman of the Compensation Committee and Michael J. Goller as a member of the Compensation Committee. As of December 2017, the Company’s Board was comprised of seven directors.

General Information and Stateme

General Information and Statement of Compliance	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
General Information and Statement of Compliance	Note 2: General Information and Statement of Compliance Preliminary remarks DBV Technologies Inc. was incorporated in Delaware on April 7, 2015 (the “US subsidiary”). The share capital of this US subsidiary is 100% owned by DBV Technologies S.A. (“DBV Technologies”). General principles The accompanying consolidated financial statements and related notes (the “Financial Statements”) present the operations of DBV Technologies S.A. and its US subsidiary (the “Group”) as of December 31, 2017. The Company is a corporate venture under French law ( société anonyme Our Financial Statements as of December 31, 2017 have been prepared under the responsibility of DBV Technologies’ management. The Financial Statements were approved by the Board of Directors of DBV Technologies on March 13, 2018. All amounts are expressed in thousands of euros, unless stated otherwise. For consolidation purposes, both DBV Technologies S.A. and the US subsidiary have prepared individual financial statements for the periods ended December 31, 2016 and December 31, 2017. Statement of Compliance Our Financial Statements have been prepared in accordance with International Financial Reporting Standards (“IFRS”) as issued by the International Accounting Standard Board (“IASB”) and whose application is mandatory for the year ended December 31, 2017. Comparative figures are presented for December 31, 2015 and 2016. Due to the listing of the Company’s ordinary shares on the Euronext Paris and in accordance with the European Union’s regulation No. 1606/2002 of July 19, 2002, the financial statements of the Group are also prepared in accordance with IFRS, as adopted by the European Union (“EU”). The following amendments are mandatorily effective for annual periods beginning on or after January 1 st • Amendments to IAS 7 – Statement of Cash flows; • Amendments to IAS 12 – Recognition of deferred tax assets for unrealized losses; • Annual improvements - 2014-2016 cycle. These amendments have not had any impact on the Financial Statements as of December 31, 2017. As of December 31, 2017, there are no differences in the IFRS published and mandated by the IASB and EU, with the exception of the following specific accounting principles which the EU has not yet adopted at the end of 2017: • Annual improvements - 2014-2016 cycle. This amendment has not had any impact on the Financial Statements as of December 31, 2017. As a result, the Financial Statements comply with IFRS as published by the IASB and as adopted by the EU. IFRS include International Financial Reporting Standards (“IFRS”), International Accounting Standards (the “IAS”), as well as the interpretations issued by the Standing Interpretations Committee (the “SIC”), and the International Financial Reporting Interpretations Committee (“IFRIC”). The main accounting methods used to prepare the Financial Statements are described below. These methods were used for all years presented. There are no new standards, amendments to standards, or interpretations applicable with effect on the period ending December 31, 2017 that have an impact on the Financial Statements or on their presentation. The Company did not elect for early application of the new standards, amendments and interpretations which were adopted but not mandatory as of December 31, 2017: • IFRS 9 – Financial Instruments; • IFRS 15 – Revenue from Contracts with Customers. The Company has adopted these new standards as of January 1 st New and revised standards and amendments that may be relevant to the Company’s operations but are not yet effective: • Amendments to IFRS 15 – Clarifications to IFRS 15 Revenue from contracts with customers; • Amendments to IFRS 2 – Classification and measurement of share-based payment transactions; • Amendments to IFRS 4 – Applying IFRS 9 with IFRS 4; • IFRS 16 – Leases; • IFRS 17 – Insurance contracts; • IFRS 14 – Regulatory deferral accounts; • IFRIC 22 – Foreign Currency Transactions and Advance Consideration; • IFRIC 23 – Uncertainty over Income Tax Treatments. Management is in the process of evaluating the impact of these standards and amendments and is therefore, not currently able to estimate reliably the impact of their adoption on the Company’s results on financial position or cash flows. The accounting policies and measurement principles adopted for the Financial Statements as of and for the year ended December 31, 2017 are the same as those used as of and for the years ended December 31, 2015 and 2016.

Accounting Principles

Accounting Principles	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Accounting Principles	Note 3: Accounting Principles Going concern The Company has primarily funded these losses through equity financings. To date, the Company has no product revenue, and management expects operating losses to continue for the foreseeable future. As the Company continues to actively prepare for the launch of a product in the United States in 2019, if approved, current cash and cash equivalents on hand are not projected to be sufficient to support the Company’s current operating plan for the next 12 months. As such, there are material uncertainties regarding the Company’s ability to continue as a going concern. The Company expects to seek additional funds, most likely from equity or debt financings. To the extent that the Company raises additional funds by issuing equity securities, stockholders may experience significant dilution. However, no assurance can be given at this time as to whether the Company will be able to achieve these financing objective. If the Company does not obtain sufficient funds when needed, the Company could scale back its operating plan, notably by deferring or limiting some or all of its research or development projects. The financial statements have been prepared on a going concern basis assuming that the Company will either be successful in its financing objections or that the Company will modify its operating plans such that the Company’s current cash and cash equivalents will be sufficient to fund the Company’s operations for a period of at least 12 months. As such, no adjustments have been made to the financial statements relating to the recoverability and classification of the asset carrying amounts or classification of liabilities that might be necessary should the Company not be able to continue as a going concern. Refer to the liquidity risk disclosed in Note 23. Methods of consolidation The Financial Statements incorporate the standalone financial statements of DBV Technologies S.A and US subsidiary which is controlled by the Company. Control is achieved when the Company: • has power over the subsidiary; • is exposed, or has rights, to variable returns from its involvement with the subsidiary; and • has the ability to use its power to affect its returns. The Company reassesses whether or not it controls a subsidiary if facts and circumstances indicate that there are changes to one or more of the three elements of control listed above. Consolidation of subsidiaries begins when the Company obtains control over the subsidiary and ceases when the Company loses control over the subsidiary. Profit or loss and each component of other comprehensive income are attributed to the owners of the Company and to the non- non-controlling non-controlling When necessary, adjustments are made to the financial statements of subsidiaries to align their accounting policies with the Group’s accounting policies. All intragroup assets and liabilities, equity, income, expenses and cash flows relating to transactions between members of the Group are neutralized in consolidation. Translation of financial statements in foreign currencies In preparing the financial statements of each individual group entity, transactions in currencies other than the entity’s functional currency are recognized at the rates of exchange prevailing at the dates of the transactions. At the end of each reporting period, monetary items denominated in foreign currencies are retranslated at the rates prevailing at that date. Non-monetary For the purpose of presenting these consolidated financial statements, the assets and liabilities of the Group’s foreign operations are translated into euros using exchange rates prevailing at the end of each reporting period. Income and expense items are translated at the average exchange rates at the dates of the transactions. Exchange differences arising, if any, are recognized in other comprehensive income and accumulated in equity. 3.1 Intangible Assets In application of the provisions in IAS 38 Intangible Assets (“IAS 38”), intangible assets acquired are recorded as assets on the Consolidated Statements of Financial Position at their acquisition cost. Research and Development Expenses Research expenses are recorded in the Financial Statements as expenses. In accordance with IAS 38, development expenses are recorded in the Financial Statements as intangible assets only if all the following criteria are met: (a) technical feasibility necessary for the completion of the development project; (b) intention on the part of the Company to complete the project and to utilize it; (c) capacity to utilize the intangible asset; (d) proof of the probability of future economic benefits associated with the asset; (e) availability of the technical, financial, and other resources for completing the project; and (f) reliable evaluation of the development expenses. Because of the risks and uncertainties related to regulatory authorizations and to the research and development process, the Company believes that the six criteria stipulated by IAS 38 are only fulfilled once the Market Access Authorization has been obtained from the competent authorities. The application of this principle has resulted in all development costs being expensed as incurred. Software The costs related to the acquisition of licenses to software are posted to assets on the basis of the costs incurred to acquire and to implement the software in question. They are amortized using the straight-line method over a period of one to three years depending on the anticipated period of use. 3.2 Property, Plant, and Equipment Property, plant, and equipment are recorded at their acquisition cost or, if applicable, at their production cost. Property, plant, and equipment are depreciated on the basis of the straight-line method over the estimated use period of the property. The fixtures of property rented are depreciated over the term of their own lifetime or of the term of the rental agreement, whichever is shorter. The depreciation periods used are the following: PROPERTY, PLANT, AND EQUIPMENT ITEM DEPRECIATION PERIOD Fixtures and improvements in structures 9 years Research and development / production tools 5 years Research equipment and technical facilities 5 years Computer equipment 3 years Office equipment and furniture 5 years 3.3 Financial Assets In accordance with IAS 39 ( Financial Instruments: Recognition and Measurement Financial Instruments: Presentation non-derivative Non-derivative Classification, presentation and subsequent measurement of non-derivative Assets Owned Until Their Maturity These securities are exclusively fixed income or determinable income and have fixed maturities, other than loans and accounts receivable, that the Company has the intention and the ability to keep until maturity. After their initial posting at their fair value, they are valued and posted to the accounts at the cost amortized on the basis of the effective interest rate (“EIR”) method. The assets owned until their maturity are monitored for any objective indication of impairment. A financial asset is impaired if its book value is greater than its recoverable amount as estimated during impairment tests. The impairment is recorded to the income statement. Loans and Receivables Loans and receivables are non-derivative non-current The loans and receivables are monitored for any objective indication of impairment. A financial asset is impaired if its book value is greater than its recoverable amount as estimated during impairment tests. The impairment is recorded in the Consolidated Statements of (Loss). The loans and receivables also include the deposits and guarantees, which are classified under “Non-current Assets at Fair Value Per the Consolidated Statements of (Loss) These assets are classified on the balance sheet in the following line items: Other non-current Financial assets at fair value through profit or loss comprise assets held for trading (financial assets acquired principally for the purpose of reselling them in the near term, usually within less than 12 months), and financial instruments designated as fair value through profit and loss on initial recognition in accordance with the conditions for application of the fair value option. Realized and unrealized foreign exchange gains and losses on financial assets in currencies other than the euro are recognized in the income statement in Financial income or Financial expenses. Assets Available for Sale The assets available for sale include, primarily, securities that do not meet the criteria of the definition of the other categories of financial assets. They are measured at their fair value, and the changes in value are recorded in the Consolidated Statements of Changes in Shareholders’ Equity. The fair value corresponds to the market price for those securities that are listed on the stock exchange or to an estimate of the use value for unlisted securities, determined on the basis of the financial criteria most appropriate for the specific situation of each security. When there is an objective indication of the impairment of these securities, the accumulated impairment that has been recorded in the Consolidated Statements of Changes in Shareholders’ Equity is recognized in the Consolidated Statement of (Loss). 3.4 Recoverable Amount of the Intangible Assets and Property, Plant, and Equipment The property, plant, and equipment and intangible assets that have an established lifetime are subjected to an impairment test when the recoverability of their book value is called into question by the existence of indications of impairment. An impairment is posted to the accounts up to the amount of the excess of the book value over the recoverable value of the asset. The recoverable value of an asset corresponds to its fair value minus the costs of sale or its use value, whichever is higher. 3.5 Inventories and Work in Progress Inventories are recorded at their cost or at their net liquidation value, if the latter is lower. In the latter case, the impairment is posted to income or loss. The inventories are valued on the basis of the “first-in, first-out” 3.6 Share Capital Common shares are classified under Shareholders’ Equity in the Consolidated Statements of Financial Position. The costs of share capital transactions that are directly attributable to the issue of new shares or options are recorded in the Financial Statements in Shareholders’ Equity as a deduction from the revenue from the issue, net of tax. 3.7 Payments in Shares Since its incorporation, the Company has established several plans for compensation paid in equity instruments in the form of employee warrants (bons de souscription de parts de créateur d’entreprise or “BSPCEs”) granted to employees and/or executives and in the form of “share warrants” (bons de souscription d’actions or “BSAs”) granted to non-employee Pursuant to IFRS 2 Share-based payment (“IFRS 2”), the cost of the transactions paid with equity instruments is posted to the accounts as an operating expense in the Consolidated Statements of (Loss) in exchange for an increase in the Shareholders’ Equity on the Consolidated Statements of Financial Position for the period during which the rights to be benefited from the equity instruments are acquired. The Company has applied IFRS 2 to all equity instruments granted since 2002 to its employees, members of the Board of Directors, other individuals, or to companies. The options are not subject to any market conditions. The characteristics of the options are presented in Note 17. 3.8 Recognition and measurement of Financial Liabilities Financial Liabilities at Amortized Cost Borrowings and other financial liabilities are valued initially at their fair value and then at the amortized cost, calculated on the basis of the effective interest rate (“EIR”) method. The transaction expenses that are directly attributable to the acquisition or to the issue of a financial liability reduce that financial liability. These expenses are then amortized over the lifetime of the liability, on the basis of the EIR. The EIR is the rate that equalizes the anticipated flow of future cash outflows with the current net book value of the financial liability in order to deduct its amortized cost therefrom. Liabilities at Fair Value per the Consolidated Statements of (Loss) The liabilities at fair value per the Consolidated Statements of (Loss) are valued at their fair value. 3.9 Subsidies and Conditional Advances Subsidies The Company receives assistance in the form of subsidies, which are grants that are not repayable by the Company. The subsidies are recognized when there is reasonable assurance that: • the Company will comply with the conditions attached to the subsidies, and • the subsidies will be received. Subsidies that are upfront non-refundable A public subsidy that is to be received (e.g. from OSEO, the French Agency for Innovation) either as compensation for expenses or for losses already incurred, or for immediate financial support of the Company without associated expenses or losses, is recognized as other income ratably over the duration of the funded project. Conditional advances The Company also receives from time to time assistance in the form of conditional advances, which are advances repayable in whole or in part based upon acknowledgment by the funder of a technical or commercial success of the related project by the funding entity. The details concerning the conditional advances are provided in Note 11. The amount resulting from the deemed benefit of the interest-free nature of the award is considered a subsidy for accounting purposes. This deemed benefit is determined by applying a discount rate equal to the rate of fungible treasury bonds over the time period that corresponds to the time period of the repayment of the advances. In the event of a change in payment schedule of the stipulated repayments of the conditional advances, the Company makes a new calculation of the net book value of the debt resulting from the discounting of the expected new future cash flows. The adjustment that results therefrom is recognized in the income statement for the fiscal year during which the modification is recognized. The conditional advances that can be subject to this type of modification are the with Compagnie Française d’Assurance pour le Commerce Extérieur (“COFACE”) advances presented in Note 11. The agreement with COFACE terminated on December 31, 2016. 3.10 Provisions Provisions for Risks and Expenses The provisions for risks and lawsuits correspond to the commitments resulting from lawsuits and various risks whose due dates and amounts are uncertain. A provision is posted to the accounts when the Company has a legal or implicit obligation to a third party resulting from a past event, concerning which it is likely or certain that it will cause an outflow of resources to that third party, without consideration that is anticipated to be at least equivalent to the latter, and that the future outflows of liquid assets can be estimated reliably. The amount recorded in the accounts as a provision is the best estimation of the expenses necessary to extinguish the obligation. Pension Retirement Obligations The employees of the Company receive the retirement benefits stipulated by law in France: • obtaining a compensation paid by the Company to employees upon their retirement (defined-benefit plan); • payment of retirement pensions by the Social Security agencies, which are financed by the contributions made by companies and employees (defined-contribution plans). For the defined-benefit plans, the costs of the retirement benefits are estimated by using the projected credit unit method. According to this method, the cost of the retirement pensions is recognized in the Consolidated Statements of (Loss) so that it is distributed uniformly over the term of the services of the employees. The retirement benefit commitments are valued at the current value of the future payments estimated using, for the discounting, the market rate based on the long-term obligations of the first-category companies with a term that corresponds to that estimated for the payment of the services provided. The Company relies on external actuaries to conduct an annual review of the valuation of these plans. The difference between the amount of the provision at the beginning of a fiscal year and at the close of that year is recognized through profit or loss for the portion representing the costs of services rendered and through other comprehensive income for the portion representing the actual gains and losses. The Company’s payments for the defined-contribution plans are recognized as operating expenses on the Consolidated Statements of (Loss) of the period with which they are associated. 3.11 Revenue The revenue of the Company resulted in previous years mainly from the sale of the product Diallertest, a kit for diagnosing the allergy to proteins in cow’s milk. During the second half of 2015, the Company discontinued its commercial partnership with respect to the product and ceased selling Diallertest Milk. The Company recognizes revenue when the amount can be measured reliably, when it is likely that the future economic advantages will benefit the Company, and when the specific criteria are met for the business activity of the Company. For product sales, the sales revenue is recognized upon delivery. 3.12 Other Income Subsidies Since it was formed, because of its innovative character, the Company has received a certain number of sources of assistance or subsidies from the central government or from local public authorities such as OSEO or the Banque Publique d’Investissement, intended to finance its operations or the recruitment of specific personnel. When the obtention of the subsidy is reasonably certain, these subsidies are recognized as “Other income” during the calendar year over which the corresponding expenses or expenditures were recorded. Research Tax Credit The Research Tax Credit (Crédit d’Impôt Recherche, CIR) is granted to companies by the French tax authorities in order to encourage them to conduct technical and scientific research. Companies that prove that they have expenditures that meet the required criteria (research expenditures located in France or, since January 1, 2005, within the European Community or in another State that is a party to the Agreement on the European Economic Area that has concluded a tax treaty with France that contains an administrative assistance clause) receive a tax credit that can be used for the payment of the corporate tax due for the fiscal year in which the expenditures were made and the next three fiscal years, or, as applicable, can be reimbursed for the excess portion. The expenditures taken into account for the calculation of the research tax credit involve only research expenses. The Company has received the Research Tax Credit annually since it was formed. The Company received the reimbursement of the 2014 Research Tax Credit for an amount of €4.3 million during the year 2015. The Company received the reimbursement of the 2015 Research Tax Credit for an amount of €5.7 million during the year 2016. The Company received the reimbursement of the 2016 Research Tax Credit for an amount of €7.3 million during the year 2017. The Company will request the reimbursement of the 2017 Research Tax Credit for an amount of €9.2 million during the year 2018, under the community tax rules for small and medium firms in compliance with the regulatory texts applicable. Collaboration agreement with Nestlé Health Science On May 31, 2016, the Company announced its entry into an exclusive global collaboration with Nestlé Health Science to develop MAG1C, a ready-to-use non-refundable In accordance with International Accounting Standard 18, upfront payments and milestones received under the Company’s collaboration agreement are deferred and recognized over the service period obligation. Upon entry into the collaboration agreement, the Company’s management estimated the expected service period obligation, as well as the cost involved in the project. Upfront payments and milestones are recognized on a straight line basis or, if the associated costs can be reliably estimated, based on the cost incurred under the project. Periodically, the Company reassesses the estimated time and cost to complete the project and adjusts the time period over which the revenue is deferred accordingly. If the outcome of a contract cannot be estimated reliably, revenue is recognized only to the extent of costs incurred that it is probable will be recoverable, in accordance with International Accounting Standard 11. As of December 31, 2017, we had recorded deferred revenue of €9.5 million related to our collaboration with Nestlé Health Science, which will be deferred and recognized ratably over the service obligation period. We expect the service obligation period to be completed in the second half of 2021. Deferred revenue is included in other current and non-current 3.13 Rental Agreements The rental agreements involving property, plant, and equipment are classified as finance lease agreements when the Company bears a substantial portion of all the benefits and risks inherent in the ownership of the property. The assets that are covered under financing lease agreements are capitalized as of the beginning date of the rental agreement on the basis of the fair value of the rented asset or the discounted values of the future minimum payments, whichever is lower. Each rental payment is distributed between the debt and the financial cost in such a manner as to determine a constant interest rate on the principal that remains due. The corresponding rental obligations, net of the financial expenses, are classified as financial liabilities. The portion of the financial expense that corresponds to the interest is recognized as an expense over the term of the agreement. The property, plant, or equipment acquired within the framework of a finance lease agreement is amortized over the use period or the term of the lease agreement, whichever is shorter. The rental agreements for which a significant portion of the risks and advantages is preserved by the lessor are classified as ordinary rental agreements. The payments made for these ordinary rental agreements, net of any incentive measures, are recognized as operating expenses on the Consolidated Statements of (Loss) in a linear manner over the term of the agreement. 3.14 Taxes Income Tax Deferred taxes are recognized for all the temporary differences arising from the difference between the tax basis and the accounting basis of the assets and liabilities that appear in the financial statements. The primary temporary differences are related to the tax losses that can be carried forward or backward. The tax rates that have been ratified by a legal text as of the closing date are utilized to determine the deferred taxes. The deferred tax assets are recorded in the accounts only to the extent that it is likely that the future profits will be sufficient to absorb the losses that can be carried forward or backward. Considering its stage of development, which does not allow income projections judged to be sufficiently reliable to be made, the Company has not recognized deferred tax assets in relation to tax losses carryforward in the Consolidated Statements of Financial Position. 3.15 Segment Information The Company operates in a single operating segment: the conducting of research and development of epicutaneous immunotherapy products in order to market them in the future. The assets, liabilities, and operating losses recognized are primarily located in France. 3.16 Other Items in the Comprehensive income (loss) The revenue and expense items for the period that are not posted in the Consolidated Statements of (Loss) as stipulated by the applicable standards are presented, as necessary, under the rubric “Other comprehensive income (loss).” 3.17 Use of Estimates The preparation of our Consolidated Financial Statements requires the management to make estimates, assumptions and judgments that affect the reported amounts of assets, liabilities, revenue and expenses. Estimates and assumptions are based on historical experience and other factors that management believes to be reasonable under the circumstances. Estimates and assumptions are measured on an ongoing basis. Actual results may differ from these estimates. These estimates and judgments mainly involve: • a valuation of the fair value of the employee warrants (BSPCEs) granted to employees and/or executives and share warrants (BSAs) granted to non-employee • an estimate of the Research Tax Credit based on internal and external expenses incurred by the Company during the year. Only eligible research expenses are included in the calculation of the research tax credit. 3.18 Presentation of Financial Assets and Financial Liabilities Measured at Fair Value • In accordance with the amendments to IFRS 7, financial instruments are presented in three categories based on a hierarchical method used to determine their fair value: • level 1: fair value calculated using quoted prices in an active market for identical assets and liabilities; • level 2: fair value calculated using valuation techniques based on observable market data such as prices of similar assets and liabilities or parameters quoted in an active market; • level 3: fair value calculated using valuation techniques based wholly or partly on unobservable inputs such as prices in an inactive market or a valuation based on multiples for unlisted securities. 3.19 Subsequent events The Consolidated Financial Statements are adjusted to reflect the subsequent events that alter the amounts related to the situations that exist as of the closing date. The adjustments are made until the date the consolidated financial statements are approved and authorized for issuance by the Board of Directors.

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2017
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Intangible Assets	Note 4: Intangible Assets The intangible assets are broken down as follows: December 31, 2015 2016 2017 (thousands of Euros) Patents, licenses, trademarks 54 196 414 Software 302 376 450 Total, gross 356 572 864 Accumulated amortization of patents, licenses, and trademarks 53 125 340 Accumulated depreciation of software packages 210 351 401 Accumulated amortization and depreciation 262 476 741 Total, net 94 96 123 The increase of the gross value of intangible assets only correspond to acquisitions for a global amount of €292 thousands. There has been no recognition of impairment losses in application of IAS 36 Impairment of Assets

Property, Plant, and Equipment

Property, Plant, and Equipment	12 Months Ended
	Dec. 31, 2017
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Property, Plant, and Equipment	Note 5: Property, Plant, and Equipment 1/1/2015 Increase Decrease 12/31/2015 (thousands of Euros) Laboratory equipment 2,257 467 (368 ) 2,357 Building fixtures 930 8 — 938 Office equipment 215 24 (30 ) 209 Computer equipment 322 244 (95 ) 470 Property, plant, and equipment in progress 51 3,622 — 3,672 Total, gross 3,775 4,365 (493 ) 7,646 Accumulated depreciation of laboratory equipment 916 382 (349 ) 948 Accumulated depreciation of the building fixtures 286 496 — 782 Accumulated depreciation of office equipment 126 35 (30 ) 131 Accumulated depreciation of computer equipment 222 78 (95 ) 205 Total accumulated amortization and depreciation 1,550 990 (475 ) 2,065 Total, net 2,225 3,375 18 5,581 1/1/2016 Increase Decrease 12/31/2016 (thousands of Euros) Laboratory equipment 2,357 740 — 3,097 Building fixtures 938 3,672 — 4,610 Office equipment 209 398 — 607 Computer equipment 470 516 — 986 Property, plant, and equipment in progress 3,672 2,713 — 6,385 Total, gross 7,646 8,039 — 15,685 Accumulated depreciation of laboratory equipment 948 557 — 1,505 Accumulated depreciation of the building fixtures 782 327 — 1,109 Accumulated depreciation of office equipment 131 81 — 212 Accumulated depreciation of computer equipment 205 172 — 377 Total accumulated amortization and depreciation 2,065 1,137 — 3,203 Total, net 5,581 6,901 — 12,482 1/1/2017 Increase Decrease 12/31/2017 (thousands of Euros) Laboratory equipment 3,097 2,806 (83 ) 5,820 Building fixtures 4,610 534 (46 ) 5,098 Office equipment 607 275 (116 ) 766 Computer equipment 986 116 (30 ) 1,073 Property, plant, and equipment in progress 6,385 3,384 (55 ) 9,714 Total, gross 15,685 7,114 (329 ) 22,470 Accumulated depreciation of laboratory equipment 1,505 802 (63 ) 2,244 Accumulated depreciation of the building fixtures 1,109 484 (14 ) 1,580 Accumulated depreciation of office equipment 212 213 (105 ) 320 Accumulated depreciation of computer equipment 377 172 (30 ) 520 Total accumulated amortization and depreciation 3,202 1,671 (211 ) 4,663 Total, net 12,482 5,443 (118 ) 17,808 Over the three years presented, the acquisitions correspond primarily to building fixtures and to laboratory and production equipment and material. The increase in property, plant and equipment in progress item is related to costs incurred for the purchase of materials for the conception and tuning of the industrial machines (Gen 4.0 and Cut Pack, for example).

Non-CurrentFinancial Assets

Non-CurrentFinancial Assets	12 Months Ended
	Dec. 31, 2017
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Non-CurrentFinancial Assets	Note 6: Non-Current December 31, 2015 2016 2017 (thousands of Euros) Deposits 716 824 577 Pledged securities and other non-current 611 611 1,102 Liquidity contract 1,384 1,310 1,333 Total non-current 2,711 2,745 3,012 The non-current sociétés d’investissement à capital variable, Under the liquidity contract, 4,939 treasury shares were allocated as a reduction of Shareholders’ Equity on the Consolidated Statements of Financial Position as at December 31, 2017 with the cash balance being maintained in financial assets. The share capital is divided in 24,990,822 shares including these 4,939 treasury shares.

Inventories and Work in Progres

Inventories and Work in Progress	12 Months Ended
	Dec. 31, 2017
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Inventories and Work in Progress	Note 7: Inventories and Work in Progress December 31, 2015 2016 2017 (thousands of Euros) Inventories of raw materials 69 69 — Depreciation of inventories (69 ) (69 ) — Total net value of the inventories — — — The inventories and work in progress involved the Diallertest Milk product. The Company discontinued its commercial partnership with respect to the product during the second half of 2015. The inventories were discarded during 2017.

Customer Accounts Receivable an

Customer Accounts Receivable and Other Current Assets	12 Months Ended
	Dec. 31, 2017
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Customer Accounts Receivable and Other Current Assets	Note 8: Customer Accounts Receivable and Other Current Assets 8.1 Customer Accounts Receivable and Related Receivables December 31, 2015 2016 2017 (thousands of Euros) Accounts receivable 13 1,263 1,265 Valuation allowance (13 ) (13 ) — Total net value of accounts receivable — 1,250 1,265 All the customer accounts receivable have payment terms of less than one year. As of December 31, 2016, and 2017, the accounts receivable correspond primarily to the amounts due under collaboration agreement with Nestlé Health Science. As of December 31, 2015, accounts receivable correspond primarily to the sales of Diallertest ® 8.2 Other current assets The other current assets are broken down as follows: December 31, 2015 2016 2017 (thousands of Euros) Research tax credit 5,702 7,228 9,217 Other tax claims 2,550 2,618 5,258 Other receivables 1,409 1,883 1,192 Prepaid expenses 1,850 2,725 2,054 Total 11,512 14,454 17,721 The other tax debt claims are primarily related to the deductible VAT as well as the reimbursement of VAT that has been requested. Prepaid expenses are comprised primarily of rental and insurance expenses, as well as legal and scientific consulting fees. As of December 31,2016, and 2017, prepaid expenses also included upfront payments, which are recognized over the term of the ongoing clinical studies. Research Tax Credit The Company benefits from the provisions in Articles 244 quater septies The changes in this Research Tax Credit over the last three years are presented as follows: thousands of Euros Opening Balance Sheet Receivable as of January 1, 2015 4,340 + Other income 5,702 - Payment received (4,322 ) - Adjustment (18 ) Closing Balance Sheet Receivable as of December 31, 2015 5,702 thousands of Euros Opening Balance Sheet Receivable as of January 1, 2016 5,702 + Other income 7,228 - Payment received (5,702 ) - Adjustment — Closing Balance Sheet Receivable as of December 31, 2016 7,228 thousands of Euros Opening Balance Sheet Receivable as of January 1, 2017 7,228 + Other income 9,217 - Payment received (7,341 ) - Adjustment 113 Closing Balance Sheet Receivable as of December 31, 2017 9,217 The adjustments to the amount of the receivable in 2015 reflect the penalties related to the tax inspection of the 2014 Research Tax Credit that occurred in 2015. Following a tax inspection led by the French tax authorities during fiscal years 2012, 2013 and 2014, on July 4, 2016, the Company received a tax reassessment notification primarily affecting the Research Tax Credit. The proposed adjustment amounted to €0.9 million. After examination, the Research Tax Credit Advisory Committee (“Comité consultatif du credit d’impôt pour dépenses de recherche”) confirmed the reassessment in a decision sent to the Company on July 6, 2017. The tax administration therefore maintained the tax reassessment. In December 2017, the Company appealed to a higher tax authority, which is the last resort before potential litigation. However, the probability of obtaining tax relief is considered very low. As a result, a provision has been recorded in the consolidated financial statement as of December 31, 2017.

Cash and Cash Equivalents

Cash and Cash Equivalents	12 Months Ended
	Dec. 31, 2017
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Cash and Cash Equivalents	Note 9: Cash and Cash Equivalents The cash and cash equivalents item is broken down as follows : December 31, 2015 2016 2017 (thousands of Euros) Cash 178,895 146,374 32,054 Cash equivalent term deposits 144,486 110,100 105,826 Total cash and cash equivalent as reported in statement of financial position 323,381 256,473 137,880 Bank overdrafts — — — Total net cash and cash equivalents as reported in the statement of cash flow 323,381 256,473 137,880 Cash equivalents are short-term, highly liquid investments that are readily convertible to known amounts of cash and which are subject to an insignificant risk of changes in value. They are measured using level 1 fair value measurements. As of December 31, 2015, the cash and cash equivalents included the net proceeds received as part of our July 2015 fundraising.

Capital

Capital	12 Months Ended
	Dec. 31, 2017
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Capital	Note 10: Capital 10.1 Share Capital Issued The share capital, as of December 31, 2017, is set at the sum of €2,499,082.20. It is divided into 24,990,822 fully authorized, subscribed and paid-up This number does not include share warrants (“BSA”), employee warrants (“BSPCE”), stock-options (“SO”) and performance shares (“AGA”) granted to certain investors and to certain natural persons, both employees and non-employees All the shares give their owners the right to a proportional share of the income and the net assets of the Company. The table below presents the historical changes in the share capital of the Company as of December 31, 2015, 2016 and 2017: Date Nature of the Transactions Share Share premium Number of Nominal Balance as of January 1, 2015 K € 1,916.1 K € 163,876.8 19,160,661 € 0.10 01/06/2015 Capital increase by issuance of common shares K€ 0.4 K€ 18.9 3,750 € 0.10 01/07/2015 Capital increase by issuance of common shares K€ 1.0 K€ 59.0 10,000 € 0.10 01/22/2015 Capital increase by incorporation of reserve K€ 3.5 K€ (3.5 ) 35,360 € 0.10 01/30/2015 Capital increase by issuance of common shares K€ 9.8 K€ 476.8 97,720 € 0.10 02/03/2015 Capital increase by issuance of common shares K€ 0.8 K€ 37.7 7,500 € 0.10 02/13/2015 Capital increase by issuance of common shares K€ 3.8 K€ 188.6 37,500 € 0.10 02/17/2015 Capital increase by issuance of common shares K€ 2.0 K€ 100.6 19,995 € 0.10 03/04/2015 Capital increase by issuance of common shares K€ 1.0 K€ 59 10,000 € 0.10 03/26/2015 Capital increase by issuance of common shares K€ 5.0 K€ 400 50,000 € 0.10 04/07/2015 Capital increase by issuance of common shares K€ 4.0 K€ 169.2 40,005 € 0.10 04/09/2015 Capital increase by issuance of common shares K€ 15.0 K€ 692.1 150,375 € 0.10 04/28/2015 Capital increase by issuance of common shares K€ 1.4 K€ 77.1 14,290 € 0.10 05/05/2015 Issue of share subscription warrants K€ K€ 43 05/11/2015 Capital increase by issuance of common shares K€ 2.0 K€ 100.7 20,010 € 0.10 06/23/2015 Capital increase by issuance of common shares K€ 59.1 K€ 27,029.4 590,543 € 0.10 06/23/2015 Capital Decrease K€ (58.6 ) K€ (26,823.4 ) (586,048 ) € 0.10 07/20/2015 Capital increase by issuance of common shares K€ 414.0 K€ 254,932.9 4,140,000 € 0.10 07/24/2015 Capital increase by issuance of common shares K€ 1.6 K€ 79.2 15,750 € 0.10 07/25/2015 Capital increase by incorporation of reserve K€ 28.6 K€ (28.6 ) 286,338 € 0.10 07/28/2015 Capital increase by issuance of common shares K€ 1.7 K€ 91.5 17,000 € 0.10 09/18/2015 Capital increase by issuance of common shares K€ 0.3 K€ 46.7 2,500 € 0.10 10/07/2015 Capital increase by issuance of common shares K€ 4.8 K€ 241.2 47,955 € 0.10 12/10/2015 Capital increase by issuance of common shares K€ 1.8 K€ 146.9 17,500 € 0.10 12/10/2015 Issue of share subscription warrants K€ K€ 99.2 12/14/2015 Capital increase by issuance of common shares K€ 1.6 K€ 69.5 16,425 € 0.10 12/31/2015 Fees charged to share premium K€ K€ (18,269.7 ) Balance as of December 31, 2015 K€ 2,420.5 K€ 403,910.4 24,205,129 € 0.10 Date Nature of the Transactions Share Share premium Number of Nominal Balance as of January 1, 2016 K € 2,420.5 K € 403,910.4 24,205,129 € 0.10 01/05/16 Capital increase by issuance of common shares K€ 0.6 K€ 32.7 6,495 02/16/16 Issue of share subscription warrants K€ K€ 471.1 € 0.10 04/06/16 Capital increase by incorporation of reserve K€ 10.2 K€ (10.2 ) 101,829 € 0.10 05/27/16 Capital increase by issuance of common shares K€ 0.2 K€ 7.5 1,500 € 0.10 06/03/16 Capital increase by issuance of common shares K€ 15.6 K€ (15.6 ) 156,000 € 0.10 06/06/16 Capital increase by issuance of common shares K€ 6.0 K€ 301.2 59,890 € 0.10 06/10/16 Capital increase by issuance of common shares K€ 3.5 K€ 176.0 34,985 € 0.10 07/18/16 Capital increase by issuance of common shares K€ 2.0 K€ 100.7 20,010 € 0.10 08/21/16 Issue of share subscription warrants K€ K€ 106 € 08/04/16 Capital increase by issuance of common shares K€ 1.0 K€ 50.4 10,020 € 0.10 08/24/16 Capital increase by issuance of common shares K€ 0.7 K€ 37.1 7,380 € 0.10 08/30/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 08/31/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/01/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/02/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/05/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/06/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/06/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/08/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/09/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/12/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/12/16 Capital increase by issuance of common shares K€ 0.5 K€ 23.1 4,590 € 0.10 11/25/16 Capital increase by issuance of common shares K€ 0.6 K€ 30.2 6,000 € 0.10 Balance as of December 31, 2016 K€ 2,464.9 K€ 405,882.5 24,648,828 € 0.10 Date Nature of the Transactions Share Capital Share premium Number of Nominal Balance as of January 1, 2017 K € 2,464.9 K € 405,882.5 24,648,828 € 0.10 02/03/17 Capital increase by issuance of common shares K€ 2.0 K€ 100.7 20,010 € 0.10 02/09/17 Issue of share subscription warrants K€ K€ 237.4 € 05/16/17 Capital increase by issuance of common shares K€ 4.0 K€ 170.7 40,365 € 0.10 07/12/17 Capital increase by issuance of common shares K€ 0.2 K€ 8.3 1,650 € 0.10 08/04/17 Capital increase by issuance of common shares K€ 0.1 K€ 64.6 1,200 € 0.10 09/14/17 Capital increase by issuance of common shares K€ 3.6 K€ 208.2 35,925 € 0.10 09/14/17 Issue of share subscription warrants K€ K€ 53.1 € 09/29/17 Capital increase by issuance of common shares K€ 0.1 K€ 4.0 500 € 0.10 09/30/17 Capital increase by incorporation of reserve K€ 23.1 K€ (23.1 ) 230,843 € 0.10 10/02/17 Capital increase by issuance of common shares K€ 0.1 K€ 4.0 500 € 0.10 12/15/17 Capital increase by incorporation of reserve K€ 1.1 K€ (1.1 ) 11,001 € 0.10 Balance as of December 31, 2017 K€ 2,499.1 K€ 406,709.3 24,990,822 € 0.10 No fees and banks commissions related to share capital increases in 2016 were posted in deduction of the share premium. In 2015, the fees and banks commissions related to share capital increases were €18.3 million. On July 20, 2015, the Company announced the closing of its underwritten public offering of 4,140,000 ordinary shares in the form of 8,280,000 American Depositary Shares (ADSs) at a price to the public of $34.00 per ADS, before underwriting discounts and commissions, which included an additional 1,080,000 ADSs sold pursuant to the full exercise of the underwriters’ option to purchase additional ADSs. Each ADS represents the right to receive one-half As part of the public offering completed in July 2015, share capital increased by the issuance of 4,140,000 shares (€414 thousands) with a corresponding increase of €236.9 million in share premium (€254.9 million gross, or €236.9 million net after deduction of fees and expenses of €18.0 million). Initial public offering on the NASDAQ Global Market On October 22, 2014, the Company announced the pricing of its global offering of 2,673,641 common shares, of which 2,138,913 ordinary shares represented by 4,277,826 ADSs at the subscription price of $ 21.64 per ADS, as part of a public offering conducted in the United States, Canada and some countries outside of France, and 534,728 common shares at a price of € 34 per share, under a concurrent private placement conducted by leaders banks and international sales agents in France and in some countries outside the United States and Canada. As part of the initial public offering completed in October 2014, share capital increased by the issuance of 3,074,686 shares €(307,468) with a corresponding increase of €93,403,561 in share premium (€104,231,855 gross, or €93,403,561 net after deduction of fees and expenses for €10,828,294.23). 10.2 Share Warrants and Employee Warrants The Company has issued share warrants (BSAs), employee warrants (BSPCEs), performance shares (AGAs) and stock-options (SO) as follows: Date Type Number of Number of Number of Maximum Strike price 12/07/2007 BSA 1,717 572 859 12,885 € 4.33 01/21/2009 BSA/BSPCE 16,380 — 4,041 60,615 € 4.33 01/21/2009 BSPCE 2,296 — — — € 4.33 06/25/2010 BSA 1,825 — 730 10,950 € 4.33 01/28/2011 BSA 10,039 7,529 — — € 5.13 06/24/2011 BSA/BSPCE 32,000 — 13,465 201,975 € 5.13 11/22/2011 BSA/BSPCE 11,377 — 2,509 37,635 € 5.13 01/17/2012 BSA 89,835 — 89,835 89,835 € 5.13 04/02/2012 AGA 669,796 1,860 — — € — 07/25/2012 AGA 134,081 — — — € — 09/25/2012 BSA 30,000 — 10,000 10,000 € 8.59 11/28/2012 AGA 35,360 — — — € — 07/25/2013 BSA 73,000 — 13,000 13,000 € 8.10 09/12/2013 AGA 501,500 113,333 101,829 101,829 € — 09/18/2013 SO 518,000 47,000 471,000 471,000 € 7.57 06/03/2014 BSA 10,000 — 5,000 5,000 € 18.79 06/03/2014 AGA 186,000 30,000 156,000 156,000 € — 06/03/2014 SO 75,000 — 75,000 75,000 € 19.01 03/24/2015 BSA 10,000 — 10,000 10,000 € 43.00 06/23/2015 SO 120,000 — 120,000 120,000 € 48.90 09/30/2015 AGA 708,500 — 708,500 708,500 € — 11/19/2015 SO 195,000 — 195,000 195,000 € 66.06 11/19/2015 BSA 22,500 7,500 15,000 15,000 € 66.06 12/15/2015 AGA 42,000 — 42,000 42,000 € — Total 3,496,206 207,794 2,033,768 2,336,224 Date Type Number of Number of Number of Maximum Strike price 12/07/2007 BSA 1,717 572 859 12,885 € 4.33 01/21/2009 BSA/BSPCE 16,380 — 2,997 44,955 € 4.33 01/21/2009 BSPCE 2,296 — — — € 4.33 06/25/2010 BSA 1,825 — 730 10,950 € 4.33 01/28/2011 BSA 10,039 7,529 — — € 5.13 06/24/2011 BSA/BSPCE 32,000 — 10,440 156,600 € 5.13 11/22/2011 BSA/BSPCE 11,377 — 2,509 37,635 € 5.13 01/17/2012 BSA 89,835 — — — € 5.13 04/02/2012 AGA 669,796 1,860 — — € — 07/25/2012 AGA 134,081 — — — € — 09/25/2012 BSA 30,000 — 10,000 10,000 € 8.59 11/28/2012 AGA 35,360 — — — € — Date Type Number of Number of Number of Maximum Strike price 07/25/2013 BSA 73,000 — 13,000 13,000 € 8.10 09/12/2013 AGA 501,500 113,333 — — € — 09/18/2013 SO 518,000 47,000 471,000 471,000 € 7.57 06/03/2014 BSA 10,000 — 5,000 5,000 € 18.79 06/03/2014 AGA 186,000 30,000 — — € — 06/03/2014 SO 75,000 — 40,000 40,000 € 19.01 03/24/2015 BSA 10,000 — 10,000 10,000 € 43.00 06/23/2015 SO 120,000 — 120,000 120,000 € 48.90 09/30/2015 AGA 708,500 13,000 695,500 695,500 € — 11/19/2015 SO 195,000 25,000 170,000 170,000 € 66.06 11/19/2015 BSA 22,500 7,500 15,000 15,000 € 66.06 12/15/2015 AGA 42,000 6,000 36,000 36,000 € — 12/15/2015 BSA 90,000 16,500 73,500 73,500 € 64.14 01/04/2016 SO 75,000 — 75,000 75,000 € 65.68 04/06/2016 AGA 63.750 5,000 58,750 58,750 € — 04/21/2016 SO 33,000 — 33,000 33,000 € 62.82 05/02/2016 SO 22,000 — 22,000 22,000 € 59.04 06/21/2016 SO 110,000 — 110,000 110,000 € 53.96 06/21/2016 BSA 20,000 — 20,000 20,000 € 52.97 06/21/2016 AGA 208,000 — 208,000 208,000 € — 08/01/2016 SO 10,000 — 10,000 10,000 € 62.24 09/15/2016 SO 9,300 — 9,300 9,300 € 62.80 10/17/2016 SO 16,500 — 16,500 16,500 € 64.39 10/27/2016 AGA 15,000 — 15,000 15,000 € — 11/15/2016 SO 8,300 — 8,300 8,300 € 68.33 12/09/2016 SO 74,960 — 74,960 74,960 € 69,75 12/09/2016 AGA 23,600 — 23,600 23,600 € — Total 4,275,616 273,294 2,360,945 2,606,435 Date Type Number of Number of Number of Maximum Strike price 12/07/2007 BSA 1,717 572 — — € 4.33 01/21/2009 BSA/BSPCE 16,380 — — — € 4.33 01/21/2009 BSPCE 2,296 — — — € 4.33 06/25/2010 BSA 1,825 — — — € 4.33 01/28/2011 BSA 10,039 7,529 — — € 5.13 06/24/2011 BSA/BSPCE 32,000 — 8,996 134,940 € 5.13 11/22/2011 BSA/BSPCE 11,377 — 2,509 37,635 € 5.13 01/17/2012 BSA 89,835 — — — € 5.13 04/02/2012 AGA 669,796 1,860 — — € — 07/25/2012 AGA 134,081 — — — € — 09/25/2012 BSA 30,000 — 7,500 7,500 € 8.59 11/28/2012 AGA 35,360 — — — € — 07/25/2013 BSA 73,000 — 9,500 9,500 € 8.10 09/12/2013 AGA 501,500 113,333 — — € — 09/18/2013 SO 518,000 47,000 471,000 471,000 € 7.57 06/03/2014 BSA 10,000 — 2,500 2,500 € 18.79 06/03/2014 AGA 186,000 30,000 — — € — 06/03/2014 SO 75,000 — 40,000 40,000 € 19.01 03/24/2015 BSA 10,000 — 10,000 10,000 € 43.00 Date Type Number of Number of Number of Maximum Strike price 06/23/2015 SO 120,000 — 120,000 120,000 € 48.90 09/30/2015 AGA 708,500 23,000 454,657 454.657 € — 11/19/2015 SO 195,000 25,000 170,000 170,000 € 66.06 11/19/2015 BSA 22,500 7,500 15,000 15,000 € 66.06 12/15/2015 AGA 42,000 9,000 21,999 21,999 € — 12/15/2015 BSA 90,000 16,500 73,500 73,500 € 64.14 01/04/2016 SO 75,000 — 75,000 75,000 € 65.68 04/06/2016 AGA 63.750 6,250 57,500 57,500 € — 04/21/2016 SO 33,000 — 33,000 33,000 € 62.82 05/02/2016 SO 22,000 — 22,000 22,000 € 59.04 06/21/2016 SO 110,000 7,500 101,300 101,300 € 53.96 06/21/2016 BSA 20,000 — 20,000 20,000 € 52.97 06/21/2016 AGA 208,000 — 208,000 208,000 € — 08/01/2016 SO 10,000 — 10,000 10,000 € 62.24 09/15/2016 SO 9,300 — 9,300 9,300 € 62.80 10/17/2016 SO 16,500 7,200 9,300 9,300 € 64.39 10/27/2016 AGA 15,000 — 15,000 15,000 € — 11/15/2016 SO 8,300 — 8,300 8,300 € 68.33 12/09/2016 SO 74,960 2,000 72,000 72,000 € 69,75 12/09/2016 AGA 23,600 1,900 21,700 21,700 € — 12/09/2016 BSA 59,000 24,992 34,008 34,008 € 69.75 12/15/2016 SO 1,100 — 1,100 1,100 € 69.35 01/16/2017 SO 19,100 — 19,100 19,100 € 66.11 03/14/2017 AGA 22,500 2,500 20,000 20,000 € — 03/15/2017 SO 7,200 — 7,200 7,200 € 66.25 04/18/2017 SO 16,500 — 16,500 16,500 € 60.77 04/20/2017 AGA 24,000 — 24,000 24,000 € — 06/15/2017 SO 126,000 7,500 118,500 118,500 € 59.05 06/15/2017 SO 111,600 — 111,600 111,600 € 60.54 06/15/2017 BSA 9,000 — 9,000 9,000 € 59.05 07/17/2017 SO 30,900 — 30,900 30,900 € 71.61 09/15/2017 SO 52,600 — 52,600 52,600 € 74.22 12/05/2017 SO 625,200 — 625,200 625,200 € 39.00 12/15/2017 SO 8,300 — 8,300 8,300 € 38.08 Total 5,388,616 341,196 3,148,469 3,309,539 The totals presented above do not include the warrants cancelled prior to December 31, 2009. As part of the initial public offering on Euronext, the nominal value of the shares underwent a fifteen-for-one The impact of the share-based payments on the net income (or loss) is presented in Note 17.

Financial and Other Non-Current

Financial and Other Non-Current Liabilities	12 Months Ended
	Dec. 31, 2017
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Financial and Other Non-Current Liabilities	Note 11: Financial and Other Non-Current 11.1 Conditional Advances The conditional advances from public institutions are subject to contracts with OSEO and COFACE. As of December 31, 2017, the Company had two advance contracts with OSEO Innovation. These advances are 100% repayable at their nominal value in the event of technical and/or commercial success and do not bear interest. The Company also benefited from a third grant from BpiFrance Financement in November 2014. The agreement with COFACE terminated on December 31, 2016, generating an exceptional income of €146 thousand corresponding to allowances which could not be reimbursed along with Company takings, and which therefore remain acquitted to the Company. Based on the actual reimbursement schedules, the portion of the conditional advances for terms longer than one year is classified as non-current The table below presents the details of the debts recorded on the Consolidated Statements of Financial Position by the type of conditional advance: 3rd OSEO contract 4th OSEO contract BPI advance COFACE Total Balance sheet debt at start of period 01/01/2015 507 805 2,584 151 4,047 Receipts — 865 — — 865 Repayments (192 ) — — — (192 ) Other transactions 3 (2 ) 82 5 89 Balance sheet debt as at 12/31/2015 318 1,669 2,666 156 4,809 Of which - non-current 4,681 Of which - current portion 128 Stated interest rate No 2,05 % No No Discount rate 0.4%-1.9 % 1.5%-1.8 % 3.20 % 4.25 % Maturity (in years) 0-3 7-9 2-7 0 3rd OSEO contract 4th OSEO contract BPI advance COFACE Total Balance sheet debt at start of period 01/01/2016 318 1,669 2,666 156 4,809 Receipts — — — — — Repayments (128 ) — — (147 ) (275 ) Other transactions 2 16 85 (9 ) 95 Balance sheet debt as at 12/31/2016 192 1,684 2,751 — 4,628 Of which - non-current 4,049 Of which - current portion 578 Stated interest rate No 2,05 % No No Discount rate 0.4%-1.9 % 1.5%-1.8 % 3.20 % 4.25 % Maturity (in years) 0-3 7-9 2-7 0 3rd OSEO contract 4th OSEO contract BPI advance Total Balance sheet debt at start of period 01/01/2017 192 1,684 2,751 4,628 Receipts — — — — Repayments (128 ) — (450 ) (578 ) Other transactions 1 16 84 101 Balance sheet debt as at 12/31/2017 64 1,700 2,386 4,150 Of which - non-current 1,825 Of which - current portion 2,325 Stated interest rate No 2,05 % No Discount rate 0.4%-1.9 % 1.5%-1.8 % 3.2 % Maturity (in years) 0-3 7-9 2-7 The changes appearing in “Other transactions” are comprised of the effect of discounting conditional advances. Third OSEO Advance In 2011, the Company was notified by OSEO Innovation of a new grant in the form of a conditional advance of up to €640,000 to finance the development of its program to treat the allergy to proteins in cow’s milk. The amount of the assistance was paid as follows: • €256,000 after the contract was signed (payment was received in 2011); • €256,000 from June 30, 2012 upon a call for funds (payment was received in 2013); • the balance of €128,000 after confirmation of the end of the program notified on December 31, 2013 (payment was received in 2014). In the event of technical or commercial success of the program, the repayment schedule will be the following: • Four quarterly repayments of €64,000 each starting no later than September 30,2014; • Twelve quarterly repayments of €32,000 each starting no later than September 30,2015. Regardless of the outcome of the development program, a fixed sum of €256,000 must be repaid in four quarterly instalments of €64,000 beginning on September 30, 2014. Fourth OSEO Advance In 2013, OSEO has provided assistance in the form of conditional advances for €3,206,162 to the Company as part of a collaborative research and clinical development in mite allergy in young children. ImmunaVia, the program, will be funded according to the following schedule, subject to the progress of the program: • €903,500 paid in April 2013; • €903,500 in October 2014 (funds which were to be paid in October 2014 were finally received on January 22, 2015 for an amount of €864,989); • €918,000 in October 2015 (not received); • €481,162 in April 2018 (not received). The funds that the Company actually received amounts to €1,768,489. Such conditional advance bears interest at an annual rate of 2.05%. In case of technical or commercial success of the project, the repayment schedule, for a total amount of €3,750,000 (including interest), is as follows: • €400,000 on or before June 30, 2021; • €800,000 on or before June 30, 2022; • €1,100,000 no later than June 30, 2023; • €1,450,000 no later than June 30, 2024. Following the defection of a sponsor, the Immunavia project was interrupted in September 2017. The Company is required to reimburse the remaining amounts of conditional advances. The reimbursment schedule is currently under discussion with BpiFrance (previously named OSEO). As a consequence, the €1.7 million is presented as current financial liabilities. BpiFrance Financement Interest-Free Loan In 2014, BpiFrance Financement granted an interest-free Innovation loan of €3,000,000 to DBV Technologies to help financing the pharmaceutical development of Viaskin Milk. This amount was received in a single disbursement on November 27, 2014. The planned repayment is scheduled in 20 quarterly repayments of €150,000 each, starting on June 30, 2017. COFACE Advance On September 6, 2007, DBV Technologies signed a prospecting insurance contract with Compagnie Française d’Assurance pour le Commerce Extérieur (“COFACE”) in order to promote its Diallertest product internationally. Under the terms of that contract, the Company received conditional advances of up to €147 thousands. DBV Technologies must repay these advances in amounts of up to 7% of its revenue from the export sales of its Diallertest product, until April 30, 2017. The agreement with COFACE was terminated on December 31, 2016, and has generated in 2016 an income of €146 thousand corresponding to the remaining amount of the advance, which will not be refunded. 11.2 Other non-current Other non-current non-current non-current non-current non-current 11.3 Due Dates of the Financial Liabilities and other non-current Due dates of the financial liabilities recognized as of December 31, 2015: Gross Less than One One to Five More than (thousands of Euros) Non-current 4,681 — 2,378 2,302 Non-current 12 — 12 — Current conditional advances 128 128 — — Current financial rent debts 21 21 — — Supplier accounts payable and related payables 10,034 10,034 — — Total financial liabilities 14,876 10,183 2,391 2,302 Due dates of the financial liabilities recognized as of December 31, 2016: Gross Less than One One to Five More than (thousands of Euros) Non-current 4,049 — 2,531 1,518 Non-current — — — — Other non-current 10,746 — 10,370 377 Current conditional advances 578 578 — — Current financial rent debts 12 12 — — Other current liabilities 14,692 14,692 — — Supplier accounts payable and related payables 13,720 13,720 — — Total financial liabilities 43,798 29,003 12,900 1,895 Due dates of the financial liabilities recognized as of December 31, 2017: Gross amount Less than One One to Five More than (thousands of Euros) Non-current 1,825 — 1,825 — Non-current — — — — Other non-current 8,869 — 8,421 448 Current conditional advances 2,325 2,325 — — Current financial rent debts — — — — Other current liabilities 15,751 15,751 — — Supplier accounts payable and related payables 16,941 16,941 — — Total financial, current and non-current 45,711 35,017 10,246 448 As detailed in Note 13, other current liabilities mainly include social security and current part of deferred revenues from the collaboration agreement with Nestlé Healthcare as well as subsidies and conditional advances.

Non-Current Provisions

Non-Current Provisions	12 Months Ended
	Dec. 31, 2017
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Non-Current Provisions	Note 12: Non-Current December 31, 2015 2016 2017 (thousands of euros) Pension retirement obligations 490 853 1,260 Total 490 853 1,260 Commitments for Compensation Payable to Employees Upon Their Retirement thousands of As of January 1, 2015 (531 ) Costs of services rendered (operating expense) (116 ) Interest expense (finance expense) (9 ) Benefit paid Actuarial gains 166 As of December 31, 2015 (490 ) Costs of services rendered (operating expense) (104 ) Interest expense (finance expense) (10 ) Benefit paid — Actuarial losses (249 ) As of December 31, 2016 (853 ) Costs of services rendered (operating expense) (219 ) Interest expense (finance expense) (11 ) Benefit paid — Actuarial losses (177 ) As of December 31, 2017 (1,260 ) As part of the estimation of the retirement commitments, the following assumptions were used for all categories of employees: December 31, 2015 2016 2017 % social security contributions 50.0 % 50.0 % 50.0 % Salary increases 2.0 % 2.0 % 2.0 % Discount rate 2.08 % 1.31 % 1.30 % Assumptions for the years ended December 31, 2015 and 2016: • Retirement age: 65 years old; • Terms of retirement: voluntary retirement; • Life table: INSEE 2010; • Collective agreement: Convention Collective Nationale de l’Industrie Pharmaceutique (National Collective Agreement in the Pharmaceutical Industry); • Turn-over of the personnel declining with age. Assumptions for the years ended December 31, 2017: • Retirement age: 65 years old; • Terms of retirement: voluntary retirement; • Life table: TGH05-TGF05; • Collective agreement: Convention Collective Nationale de l’Industrie Pharmaceutique (National Collective Agreement in the Pharmaceutical Industry); • Turn-over of the personnel declining with age. The discount rates come from the corporate AA zero coupon yield curve. No employee has retired during the last three fiscal years presented.

Supplier Accounts Receivable an

Supplier Accounts Receivable and Other Current Liabilities	12 Months Ended
	Dec. 31, 2017
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Supplier Accounts Receivable and Other Current Liabilities	Note 13: Supplier Accounts Receivable and Other Current Liabilities 13.1 Supplier Accounts Payable and Related Payables No discounting was performed on the supplier accounts payable and related payables to the extent that the amounts did not present payment terms longer than one year at the end of each fiscal year presented. 13.2 Other Current Liabilities December, 31 2015 2016 2017 (thousands of Euros) Social security 4,464 10,794 12,094 Tax liabilities 388 504 428 Other debts 195 146 440 Deferred revenues 791 3,248 2,789 Total 5,838 14,692 15,751 The other liabilities include the short-term debts to employees, as well as social welfare and tax agencies. Deferred revenues include subsidies, conditional advances and current part of deferred revenues from the collaboration agreement with Nestlé Healthcare.

Financial Instruments Recognize

Financial Instruments Recognized in the Consolidated Statements of Financial Position and Related Effect on the Consolidated Statements of (Loss)	12 Months Ended
	Dec. 31, 2017
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Financial Instruments Recognized in the Consolidated Statements of Financial Position and Related Effect on the Consolidated Statements of (Loss)	Note 14: Financial Instruments Recognized in the Consolidated Statements of Financial Position and Related Effect on the Consolidated Statements of (Loss) 2015 Book value in Fair value Loans and (1) Debt At Fair value Financial assets Long-term financial assets 2,711 1,365 1,346 — 2,711 Customer accounts receivables and related receivables — — — — — Other current financial assets 333 — 333 — 333 Cash and cash equivalents 323,381 323,381 — — 323,381 Total financial assets 326,425 324,746 1,679 — 326,425 Financial liabilities Long-term conditional advances 4,681 — — 4,681 4,681 Long term financial rent debt 12 — — 12 12 Short-term conditional advances 128 — — 128 128 Short term financial rent debt 21 — — 21 21 Account payable and other liabilities 15,872 — — 15,872 15,872 Total financial liabilities 20,714 — — 20,714 20,714 2016 Book value in Fair value Loans and (1) Debt At Fair value Financial assets Long-term financial assets 2,745 1,310 1,435 — 2,745 Customer accounts receivables and related receivables 1,250 — 1,250 — 1,250 Other current financial assets 516 — 516 — 516 Cash and cash equivalents 256,473 256,473 — — 256,473 Total financial assets 260,985 257,783 3,202 — 260,985 Financial liabilities Long-term conditional advances 4,049 — — 4,049 4,049 Long term financial rent debt — — — — — Other long-term liabilities 10,746 — — 10,746 10,746 Short-term conditional advances 578 — — 578 578 Short term financial rent debt 12 — — 12 12 Other short-term liabilities 14,692 — — 14,692 14,692 Account payable and other liabilities 13,720 — — 13,720 13,720 Total financial liabilities 43,798 — — 43,798 43,798 2017 Book value in Fair value Loans and (1) Debt At Fair value Financial assets Long-term financial assets 3,012 1,333 1,679 — 3,012 Customer accounts receivables and related receivables 1,265 — 1,265 — 1,265 Other current financial assets 378 — 378 — 378 Cash and cash equivalents 137,880 137,880 — — 137,880 Total financial assets 142,534 139,213 3,321 — 142,534 Financial liabilities Long-term conditional advances 1,825 — — 1,825 1,825 Long term financial rent debt — — — — — Other long-term liabilities 8,869 — — 8,869 8,869 Short-term conditional advances 2,325 — — 2,325 2,325 Short term financial rent debt — — — — — Other short-term liabilities 15,751 — — 15,751 15,751 Account payable and other liabilities 16,941 — — 16,941 16,941 Total financial liabilities 45,711 — — 45,711 45,711 (1) The fair value of “loans and receivables” corresponds to the value reported in the Consolidated Statements of Financial Position (value at the transaction date and then tested for impairment on each reporting date). (2) The book amount of financial liabilities measured at amortized cost was deemed to be a reasonable estimation of fair value. (3) The fair value of financial assets held for trading is determined based on Level 1 fair value measurements and corresponds to the market value of the assets.

Operating Income

Operating Income	12 Months Ended
	Dec. 31, 2017
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Operating Income	Note 15: Operating Income The operating income is broken down in the following manner: December 31, 2015 2016 2017 (thousands of Euros) Revenues 202 — — Research tax credit 5,685 7,228 9,330 Subsidies 279 303 271 Other operating income — 1,554 2,308 Total 6,166 9,084 11,909 The revenues of the Company are composed of the sales of Diallertest ® As of December 31, 2016 and 2017, the Company also recorded as other income a portion of the upfront fee and milestones agreed under the contract with Nestlé which are deferred over the performance obligation. As of December 31, 2017, we had recorded deferred revenue of €9.5 million related to our collaboration with Nestlé Health Science, which will be deferred and recognized ratably over the service obligation period. We expect the service obligation period to be completed in the second half of 2021.

Operating Expenses

Operating Expenses	12 Months Ended
	Dec. 31, 2017
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Operating Expenses	Note 16: Operating Expenses The research and development expenses are broken down as follows: December 31, Research and development expenses 2015 2016 2017 (thousands of Euros) Personnel expenses 13,268 32,777 37,112 Sub-contracting, 15,325 34,413 54,397 Research supplies 911 1,234 1,464 Rental 1,094 1,903 2,018 Conferences, travel expenses 1,233 2,387 2,807 Depreciation and amortization 1,000 1,141 2,424 Small equipments and other supplies 795 2,675 2,646 Others 608 2,298 2,364 Total research and development expenses 34,234 78,828 105,232 The sales and marketing expenses are broken down as follows: December 31, Sales and marketing expenses 2015 2016 2017 (thousands of Euros) Personnel expenses 133 4,954 6,976 Fees 339 4,447 2,480 Marketing, tradeshows and travel expenses 20 1,393 5,984 Others — 487 384 Total sales and marketing expenses 491 11,282 15,824 By nature, the breakdown of general and administrative expenses is as follows: December 31, General and administrative expenses 2015 2016 2017 (thousands of Euros) Personnel expenses 8,768 22,613 19,742 Fees 4,234 7,701 10,347 Rental 305 501 584 Insurance policies 1,239 1,853 1,367 Corporate communication and travel expenses 1,010 1,136 1,599 Depreciation and amortization 74 181 422 Others 1,229 1,020 1,776 Total general and administrative expenses 16,859 35,005 35,837 Personnel Expenses The Company had 242 employees at December 31, 2017, in comparison with 164 employees at December 31, 2016 and 91 employees at December 31, 2015. The personnel expenses are broken down as follows: December 31, 2015 2016 2017 (thousands of Euros) Wages and salaries 7,243 14,651 22,451 Social security contributions 3,193 3,903 7,157 Expenses for pension commitments 116 982 1,583 Employer contribution to bonus shares 1,198 6,456 1,857 Share-based payments 10,419 34,353 30,781 Total 22,168 60,345 63,830 The increase in personnel charges is partly due to the growth of the Company’s employees and the increase of the share-based payments linked to the global plans put in place during the second semester of 2015 and in 2016 (see Note 17).

Share-Based Payments

Share-Based Payments	12 Months Ended
	Dec. 31, 2017
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Share-Based Payments	Note 17: Share-Based Payments The Board of Directors has been authorized by the general meeting of the shareholders to grant employee warrants ( Bons de Souscription de Parts de Créateur d’Entreprise • With the authorization of the General Meeting of Shareholders on January 21, 2009, the Board of Directors issued 2,296 BCEX (“BCEX”); • With the authorization of the General Meeting of Shareholders on June 14, 2007, December 16, 2010 and December 9, 2011, the board of Directors issued 194,552 BSA (“BSA”). • With the authorization of the General Meeting of Shareholders on January 21, 2009, the Board of Directors issued 10,716 BSA (“BSA2”); • With the authorization of the General Meeting of Shareholders on January 21, 2009, the Board of Directors issued 5,358 BCE (“BCE4”); • With the authorization of the General Meeting of Shareholders on December 16, 2010, the Board of Directors issued 19,377 BSA (“BSA2010”); • With the authorization of the General Meeting of Shareholders on January 21, 2009, the Board of Directors issued 2,131 BSA (“BSAX”); • With the authorization of the General Meeting of Shareholders on December 16, 2010, the Board of Directors issued 34,039 BSPCE (“BSPCE2010”); • With the authorization of the General Meeting of Shareholders on December 9, 2011, the Board of Directors issued 518,000 options (“OPTIONS 2013”); • With the authorization of the General Meeting of Shareholders on December 9, 2011, the Board of Directors issued 1,340,737 Free shares (“Free shares”). • With the authorization of the General Meeting of Shareholders on June 4, 2013, the Board of Directors issued 73,000 BSA • With the authorization of the General Meeting of Shareholders on June 3, 2014, the Board of Directors issued 20,000 BSA • With the authorization of the General Meeting of Shareholders on June 3, 2014, the Board of Directors issued 918,960 options; • With the authorization of the General Meeting of Shareholders on June 3, 2014, the Board of Directors issued 186,000 free shares; • With the authorization of the General Meeting of Shareholders on June 23, 2015, the Board of Directors issued 88,500 BSA • With the authorization of the General Meeting of Shareholders on September 21, 2015, the Board of Directors granted 1,107,350 Free shares which 241,844 have been issued as of December 31,2017. • With the authorization of the General Meeting of Shareholders on June 21, 2016, the Board of Directors issued 54,008 BSA • With the authorization of the General Meeting of Shareholders on June 15, 2017, the Board of Directors issued 9,000 BSA • With the authorization of the General Meeting of Shareholders on June 15, 2017, the Board of Directors issued 828,600 options. 17.1 BSA Date of Grant 12/07/2007 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to one fourth (1/4) of the BSA on the first anniversary of the date of grant; • up to one fourth (1/4) of the BSA on the second anniversary of the date of grant; • up to one fourth (1/4) of the BSA on the third anniversary of the date of grant; • up to one fourth (1/4) of the BSA on the fourth anniversary of the date of grant; and • at the latest within ten (10) years from the date of grant. Date of Grant 01/17/2012 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 89,835 BSA (all the BSA) on January 17, 2016; and • at the latest within ten (10) years from the date of grant. Date of Grant 09/25/2012 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 30,000 BSA (all the BSA) on the date of grant; and • at the latest within ten (10) years from the date of grant. Date of Grant 07/25/2013 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 73,000 BSA (all the BSA) on the date of grant; and • at the latest within ten (10) years from the date of grant. Date of Grant 06/03/2014 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 10,000 BSA (all the BSA) on the date of grant; and • at the latest within ten (10) years from the date of grant. Date of Grant 24/03/2015 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 10,000 BSA (all the BSA) on the date of grant; and • at the latest within ten (10) years from the date of grant. Date of Grant 19/11/2015 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 15,000 BSA (all the BSA) on the date of grant; and • at the latest within ten (10) years from the date of grant. Date of Grant 15/12/2015 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 73,500 BSA (all the BSA) on the date of grant; and • at the latest within ten (10) years from the date of grant. Date of Grant 06/21/2016 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 20,000 BSA (all the BSA) on the date of grant; and • at the latest within ten (10) years from the date of grant. Date of Grant 12/09/2016 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 34,008 BSA (all the BSA) on the date of grant; and • at the latest within ten (10) years from the date of grant. Date of Grant 06/15/2017 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 9,000 BSA (all the BSA) on the date of grant; and • at the latest within ten (10) years from the date of grant. Details of BSA Date of grant (Board of 12/07/2007 12/07/2007 12/07/2007 12/07/2007 01/17/2012 01/17/2012 01/17/2012 01/17/2012 Vesting period (years) 1 2 3 4 1 2 3 4 Plan expiration date 12/08/2017 12/08/2017 12/08/2017 12/08/2017 01/17/2022 01/17/2022 01/17/2022 01/17/2022 Number of BSA granted 431 431 428 427 22,459 22,459 22,459 22,458 Share entitlement per BSA(1) 15 15 15 15 1 1 1 1 Exercise price (in euros) 65 65 65 65 5.13 5.13 5.13 5.13 Valuation method used Black - Scholes Grant date share fair value (in euros) 65 65 65 65 5.13 5.13 5.13 5.13 Expected volatility 40 % 40 % 40 % 40 % 40 % 40 % 40 % 40 % Average life of BSA (in years) 4.5 5.0 5.5 6.0 5.5 6.0 6.5 7.0 Discount rate(2) 4.06 % 4.09 % 4.09 % 4.10 % 2.33 % 2.33 % 2.61 % 2.61 % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA NA NA Fair value per BSA (in euros) 22.18 23.62 24.95 26.22 2.05 2.14 2.26 2.34 (1) The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BSA warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BSA plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans. (2) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BSA. Date of grant (Board of Directors) 09/25/2012 09/25/2012 09/25/2012 09/25/2012 07/25/2013 06/03/2014 Vesting period (years) 1 2 3 4 0 0 Plan expiration date 09/25/2022 09/25/2022 09/25/2022 09/25/2022 07/25/2023 06/03/2024 Number of BSA granted 7 500 7 500 7 500 7 500 73 000 10 000 Share entitlement per BSA 1 1 1 1 1 1 Exercise price (in euros) 8.59 8.59 8.59 8.59 8.1 18.79 Valuation method used Black - Scholes Grant date share fair value (in euros) 8.4 8.4 8.4 8.4 8.15 19.01 Expected volatility 40 % 40 % 40 % 40 % 40 % 40 % Average life of BSA (in years) 5.5 6.0 6.5 7.0 5.0 5.0 Discount rate(1) 1.21 % 1.21 % 1.53 % 1.53 % 1.16 % 0.71 % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA Fair value per BSA (in euros) 2.29 2.43 2.61 2.74 2.18 4.98 (1) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BSA. Date of grant (Board of Directors) 03/24/2015 11/19/2015 12/15/2015 06/21/2016 Vesting period (years) Plan expiration date 03/24/2025 11/19/2025 12/15/2015 06/21/2016 Number of BSA granted 10,000 15,000 90,000 (1) 20,000 Share entitlement per BSA 1 1 1 1 Exercise price (in euros) 43.00 66.06 64,14 52.97 Valuation method used Black - Scholes Grant date share fair value (in euros) 43 66.06 42.61 61.25 Expected volatility 36 % 50.91 % 51 % 47 % Average life of BSA (in years) 5.0 5.0 5.0 5.0 Discount rate(1) 0.68 % 0.81 % -0.09 % -0.41 % Expected dividends 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA Fair value per BSA (in euros) 9.90 22.60 7.28 21.59 Date of grant (Board of Directors) 12/09/2016 06/15/2017 Vesting period (years) 0 0 Plan expiration date 12/09/2026 06/15/2027 Number of BSA granted 59,000 9,000 Share entitlement per BSA 1 1 Exercise price (in euros) 69.75 59.05 Valuation method used Black - Scholes Grant date share fair value (in euros) 63.18 73.32 Expected volatility 40 % 39 % Average life of BSA (in years) 5.0 5.0 Discount rate(1) -0.04 % -0.12 % Expected dividends 0 % 0 % Performance conditions NA NA Fair value per BSA (in euros) 12.94 24.02 (1) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BSA. Change in Number of BSA Outstanding Year ended December 31, Number of BSA 2015 2016 2017 Balance at beginning of period 196,480 143,694 147,359 Granted during the period 25,000 93,500 68,000 Forfeited during the period — — 24,902 Exercised during the period 77,786 89,835 9,359 Expired during the period — — — Balance at end of period 143,694 147,359 181,008 Breakdown of the Closing Balance Year ended December 31, 2015 2016 2017 Number of BSA Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable BSA2010 with exercise price of €65 859 859 859 859 — — BSA2010 with exercise price of €5.13 89,835 — — — — — BSA2010 with exercise price of €8.59 10,000 10,000 10,000 10,000 7,500 7,500 BSA2010 with exercise price of €8.10 13,000 13,000 13,000 13,000 9,500 9,500 BSA2010 with exercise price of €18.79 5,000 5,000 5,000 5,000 2,500 2,500 BSA with exercise price of €43.00 10,000 10,000 10,000 10,000 10,000 10,000 BSA with exercise price of €66.06 15,000 15,000 15,000 15,000 15,000 15,000 BSA with exercise price of €64.14 — — 73,500 73,500 73,500 73,500 BSA with exercise price of €52.97 — — 20,000 20,000 20,000 20,000 BSA with exercise price of €69.75 — — — — 34,008 34,008 BSA with exercise price of €59.05 — — — — 9,000 9,000 Total 143,694 53,859 147,359 147,359 181,008 181,008 17.3 BSA 2 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 4,822 BSA on the date of grant; • up to 2,680 BSA on the first anniversary of the date of grant; • up to 1,072 BSA on the second anniversary of the date of grant; • up to 1,072 BSA on the third anniversary of the date of grant; • up to 1,070 BSA on the fourth anniversary of the date of grant; and • at the latest within ten (10) years from the date of grant. By a decision by the Board of Directors meeting held on November 22, 2011, the BSA2 warrants became exercisable beginning on the date of the first quotation of the shares of the Company on the Euronext regulated market in Paris. Details of BSA2 Date of grant (Board of Directors) 01/21/2009 01/21/2009 01/21/2009 01/21/2009 01/21/2009 Vesting period (years) 0 1 2 3 4 Plan expiration date 01/20/2019 01/20/2019 01/20/2019 01/20/2019 01/20/2019 Number of BSA2 granted 4,822 2,680 1,072 1,072 1,070 Share entitlement per BSA2(1) 15 15 15 15 15 Exercise price (in euros) 65 65 65 65 65 Valuation method used Black - Scholes Grant date share fair value (in euros) 70 70 70 70 70 Expected volatility 40 % 40 % 40 % 40 % 40 % Average life of BSA2 (in years) 5.0 5.5 6.0 6.5 7.0 Discount rate(2) 2.71 % 2.71 % 2.98 % 2.98 % 3.11 % Expected dividends 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA Fair value per BSA2 (in euros) 29.05 30.32 31.89 33.05 33.45 (1) The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BSA2 warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BSA2 plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans. (2) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BSA2. Change in Number of BSA 2 Outstanding Year ended December 31 Number of BSA2 2015 2016 2017 Balance at beginning of period 8,049 — — Granted during the period — — — Forfeited during the period — — — Exercised during the period 8,049 — — Expired during the period — — — Balance at end of period — — — Breakdown of the Closing Balance Year ended December 31, 2015 2016 2017 Number of BSA2 Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable BSA2 with exercise price of €65 — — — — — — Total — — — — — — 17.4 BCE 4 The BCE4 may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 2,411 BCE4 on the date of grant; • up to 1,340 BCE4 on the first anniversary of the date of grant; • up to 536 BCE4 on the second anniversary of the date of grant; • up to 536 BCE4 on the third anniversary of the date of grant; • up to 535 BSA on the fourth anniversary of the date of grant; and • at the latest within ten (10) years from the date of grant. By a decision by the Board of Directors meeting held on November 22, 2011, the BCE4 warrants became exercisable beginning on the date of the first quotation of the shares of the Company on the Euronext regulated market in Paris. Details of BCE4 Date of grant (Board of Directors) 01/21/2009 01/21/2009 01/21/2009 01/21/2009 01/21/2009 Vesting period (years) 0 1 2 3 4 Plan expiration date 01/20/2019 01/20/2019 01/20/2019 01/20/2019 01/20/2019 Number of BCE4 granted 2,411 1,340 536 536 535 Share entitlement per BCE4(1) 15 15 15 15 15 Exercise price (in euros) 65 65 65 65 65 Valuation method used Black - Scholes Grant date share fair value (in euros) 70 70 70 70 70 Expected volatility 40 % 40 % 40 % 40 % 40 % Average life of BCE4 (in years) 5.0 5.5 6.0 6.5 7.0 Discount rate(2) 2.71 % 2.71 % 2.98 % 2.98 % 3.11 % Expected dividends 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA Fair value per BCE4 (in euros) 29.06 30.33 31.90 33.06 34.35 (1) The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BCE4 warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BCE4 plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans. (2) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BCE4. Change in Number of BCE4 Outstanding Year ended December 31, Number of BCE4 2015 2015 2016 Balance at beginning of period 5,358 2,691 2,691 Granted during the period — — — Forfeited during the period — — — Exercised during the period 2,667 — 2,691 Expired during the period — — — Balance at end of period 2,691 2,691 — Breakdown of the Closing Balance Year ended December 31, 2015 2016 2017 Number of BCE4 Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable BCE4 with exercise price of €65 2,691 2,691 2,691 2,691 — — Total 2,691 2,691 2,691 2,691 — — 17.5 BSA2010 Date of Grant 01/28/2011 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 2,510 BSA on the 12/23/2011; • up to 2,510 BSA on the 12/23/2012; • up to 2,510 BSA on the 12/23/2013; • up to 2,509 BSA on the 12/23/2014; and • at the latest before the 01/28/2021. Date of Grant 06/24/2011 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to one fourth (1/4) of the BSA on the 12/23/2011; • up to one fourth (1/4) of the BSA on the 12/23/2012; • up to one fourth (1/4) of the BSA on the 12/23/2013; • up to one fourth (1/4) of the BSA on the 12/23/2014; and • at the latest before the 11/22/2021. Date of Grant 11/22/2011 The BSA may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 335 BSA on the 11/22/2012; • up to 335 BSA on the 11/22/2013; • up to 334 BSA on the 11/22/2014; • up to 334 BSA on the 11/22/2015; and • at the latest before the 11/22/2021. Details of BSA2010 Date of grant (Board of Directors) 01/28/2011 01/28/2011 01/28/2011 01/28/2011 06/24/2011 06/24/2011 06/24/2011 06/24/2011 Vesting period (years) 0.9 1.9 2.9 3.9 0.5 1.5 2.5 3.5 Plan expiration date 01/27/2021 01/27/2021 01/27/2021 01/27/2021 11/22/2021 11/22/2021 11/22/2021 11/22/2021 Number of BSA2010 granted 2,510 2,510 2,510 2,509 2,000 2,000 2,000 2,000 Share entitlement per BSA2010(1) 15 15 15 15 15 15 15 15 Exercise price (in euros) 77 77 77 77 77 77 77 77 Valuation method used Black - Scholes Black - Scholes Grant date share fair value (in euros) 77 77 77 77 77 77 77 77 Expected volatility 40 % 40 % 40 % 40 % 40 % 40 % 40 % 40 % Average life of BSA2010 (in years) 5.5 6.0 6.5 7.0 5.5 6.0 6.5 7.0 Discount rate(2) 2.70 % 2.82 % 2.82 % 3.04 % 2.55 % 2.68 % 2.68 % 2.87 % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA NA NA Fair value per BSA2010 (in euros) 31.33 32.90 34.23 35.84 31.15 32.70 34.02 35.57 (1) The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BSA2010 warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BSA2010 plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans. (2) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BSA2010. Date of grant (Board of Directors) 11/22/2011 11/22/2011 11/22/2011 11/22/2011 Vesting period (years) 1.0 2.0 3.0 4.0 Plan expiration date 11/22/2021 11/22/2021 11/22/2021 11/22/2021 Number of BSA2010 granted 335 335 334 334 Share entitlement per BSA(1) 15 15 15 15 Exercise price (in euros) 77 77 77 77 Valuation method used Black - Scholes Grant date share fair value (in euros) 77 77 77 77 Expected volatility 40 % 40 % 40 % 40 % Average life of BSA (in years) 5.5 6.0 6.5 7.0 Discount rate(2) 2.23 % 2.60 % 2.60 % 2.85 % Expected dividends 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA Fair value per BSA (in euros) 30.70 32.58 33.89 35.54 (1) The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BSA2010 warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BSA2010 plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans. (2) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BSA2010. Change in Number of BSA2010 Outstanding Year ended December 31, Number of BSA 2015 2016 2017 Balance at beginning of period 8,334 1,044 610 Granted during the period — — — Forfeited during the period — — — Exercised during the period 7,290 434 110 Expired during the period — — — Balance at end of period 1,044 610 500 Breakdown of the Closing Balance Year ended December 31, 2015 2016 2017 Number of BSA2010 Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable BSA2010 with exercise price of €77 1,044 1,044 610 610 500 500 Total 1,044 1,044 610 610 500 500 17.6 BSAX Date of Grant 01/21/2009 and 06/25/2010 The BSAX may be exercised by the beneficiary on the basis of the following vesting schedule: • up to one fourth (1/4) of the BSAX on the first anniversary of the date of grant; • up to one fourth (1/4) of the BSAX on the second anniversary of the date of grant; • up to one fourth (1/4) of the BSAX on the third anniversary of the date of grant; • up to one fourth (1/4) of the BSAX on the fourth anniversary of the date of grant; and • at the latest within ten (10) years from the date of grant. By a decision by the Board of Directors meeting held on November 22, 2011, the BSAX warrants became exercisable beginning on the date of the first quotation of the shares of the Company on the Euronext regulated market in Paris. Details of BSAX Date of grant (Board of Directors) 01/21/2009 01/21/2009 01/21/2009 01/21/2009 06/25/2010 06/25/2010 06/25/2010 06/25/2010 Vesting period (years) 1 2 3 4 1 2 3 4 Plan expiration date 01/20/2019 01/20/2019 01/20/2019 01/20/2019 06/24/2020 06/24/2020 06/24/2020 06/24/2020 Number of BSAX granted 77 77 77 75 457 457 456 455 Share entitlement per BSAX(1) 15 15 15 15 15 15 15 15 Exercise price (in euros) 65 65 65 65 65 65 65 65 Valuation method used Black - Scholes Grant date share fair value (in euros) 70 70 70 70 70 70 70 70 Expected volatility 40 % 40 % 40 % 40 % 40 % 40 % 40 % 40 % Average life of BSAX (in years) 5.5 6.0 6.5 7.0 5.5 6.0 6.5 7.0 Discount rate(2) 2.71 % 2.98 % 2.98 % 3.11 % 2.04 % 2.23 % 2.23 % 2.50 % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA NA NA Fair value per BSAX (in euros) 30.32 31.89 33.05 33.45 29.47 30.88 31.99 33.44 (1) The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BSAX warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BSAX plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans. (2) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BSAX. Change in Number of BSAX Outstanding Year ended December 31, Number of BSAX 2015 2016 2017 Balance at beginning of period 2,131 1,036 1,036 Granted during the period — — — Forfeited during the period — — — Exercised during the period 1,095 — 1,036 Expired during the period — — — Balance at end of period 1,036 1,036 — Breakdown of the Closing Balance Year ended December 31, 2014 2015 2016 Number of BSAX Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable BSAX with exercise price of €65 1,036 1,036 1,036 1,036 — — Total 1,036 1,036 1,036 1,036 — — 17.7 BCE2010 Date of Grant 06/24/2011 The BCE may be exercised by the beneficiary on the basis of the following vesting schedule: • up to one fourth (1/4) of the BCE on the 12/23/2011; • up to one fourth (1/4) of the BCE on the 12/23/2012; • up to one fourth (1/4) of the BCE on the 12/23/2013; • up to one fourth (1/4) of the BCE on the 12/23/2014; and • at the latest within before the 11/22/2021. Date of Grant 11/22/2011 The BSPCE may be exercised by the beneficiary on the basis of the following vesting schedule: • up to one fourth (1/4) of the BSPCE on the 11/22/2012; • up to one fourth (1/4) of the BSPCE on the 11/22/2013; • up to one fourth (1/4) of the BSPCE on the 11/22/2014; • up to one fourth (1/4) of the BSPCE on the 11/22/2015; and • at the latest within before the 11/22/2021. Details of BCE2010 Date of grant (Board of Directors) 06/24/2011 06/24/2011 06/24/2011 06/24/2011 11/22/2011 11/22/2011 11/22/2011 11/22/2011 Vesting period (years) 0.5 1.5 2.5 3.5 1 2 3 4 Plan expiration date 11/22/2021 11/22/2021 11/22/2021 11/22/2021 11/22/2021 11/22/2021 11/22/2021 11/22/2021 Number of BCE2010 granted 6,000 6,000 6,000 6,000 2,510 2,510 2,510 2,509 Share entitlement per BCE2010(1) 15 15 15 15 15 15 15 15 Exercise price (in euros) 77 77 77 77 77 77 77 77 Valuation method used Black and Scholes Grant date share fair value (in euros) 77 77 77 77 77 77 77 77 Expected volatility 40 % 40 % 40 % 40 % 40 % 40 % 40 % 40 % Average life of BCE2010 (in years) 5.5 6.0 6.5 7.0 5.4 5.9 6.4 6.9 Discount rate(2) 2.55 % 2.68 % 2.68 % 2.87 % 2.05 % 2.42 % 2.42 % 2.66 % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA NA NA Fair value per BCE2010 (in euros) 31.16 32.71 34.03 35.58 30.42 32.29 33.58 35.2 (1) The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BCE2010 warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BCE2010 plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans. (2) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BCE2010. Change in Number of BCE2010 Outstanding Year ended December 31, Number of BCE2010 2015 2016 2017 Balance at beginning of period 29,972 15,974 12,339 Granted during the period — — — Forfeited during the period — — — Exercised during the period 13,998 3,635 1,334 Expired during the period — — — Balance at end of period 15,974 12,339 11,005 Breakdown of the Closing Balance Year ended December 31, 2015 2016 2017 Number of BCE2010 Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable BCE2010 with exercise price of €77.00 15,974 15,974 12,339 12,339 11,005 11,005 Total 15,974 15,974 12,339 12,339 11,005 11,005 17.8 OPTIONS Grant of 09/18/2013 The share options may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 518,000 SO (all the SO) on the fourth anniversary of the date of grant; and • at the latest within ten (10) years from the date of grant. Grant of 06/03/2014 The share options may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 75,000 SO (all the SO) on the 06/04/2016; and • at the latest before the 06/03/2024. Grant of 06/23/2015 The share options may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 30,000 SO on the 06/24/2016; • up to 30,000 additional SO on the 06/24/2017; • up to 30,000 additional SO on the 06/24/2018; • up to 30,000 additional SO on the 06/24/2019; • and at the latest before the 06/24/2025. Grant of 09/30/2015 The 195,000 share options may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 25% of the SO on the 09/30/2016; • up to additional 25% of the SO on the 09/30/2017; • up to additional 25% of the SO on the 09/30/2018; • up to additional 25% of the SO on the 09/30/2019; • and at the latest before the 09/30/2025. Grant of 12/15/2015 The 75,000 share options may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 25% of the SO on the 12/15/2016; • up to additional 25% of the SO on the 12/15/2017; • up to additional 25% of the SO on the 12/15/2018; • up to additional 25% of the SO on the 12/15/2019; • and at the latest before the 12/15/2025. Grant of 04/06/2016 The 55,000 share options may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 8,250 SO on the 04/021//2017; • up to additional 8,250 SO on the 04/21//2018; • up to additional 8,250 SO on the 04/21//2019; • up to additional 8,250 SO on the 04/21//2020; • up to 5,500 SO on the 05/02//2017; • up to additional 5,500 SO on the 05/02//2018; • up to additional 5,500 SO on the 05/02//2019; • up to additional 5,500 SO on the 05/02//2020; • and at the latest before 10 years of the date of the Grant. Grant of 06/21/2016 The 154,100 share options may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 25% of the SO as of one year after the Grant date; • up to additional 12.5% of the SO as of 18 months after the Grant date; • up to additional 12.5% of the SO as of 24 months after the Grant date; • up to additional 12.5% of the SO as of 30 months after the Grant date; • up to additional 12.5% of the SO as of 36 months after the Grant date; • up to additional 12.5% of the SO as of 42 months after the Grant date; • up to additional 12.5% of the SO as of 48 months after the Grant date; • and at the latest before 10 years of the date of the Grant. Grant of 12/09/2016 The 74,960 share options may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 18,740 SO as of one year after the Grant date; • up to additional 9,370 SO as of 18 months after the Grant date; • up to additional 9,370 SO as of 24 months after the Grant date; • up to additional 9,370 SO as of 30 months after the Grant date; • up to additional 9,370 SO as of 36 months after the Grant date; • up to additional 9,370 SO as of 42 months after the Grant date; • up to additional 9,370 48 months after the Grant date; • and at the latest before 10 years of the date of the Grant. Grant of 12/15/2016 The 1,100 share options may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 25% SO as of one year after the Grant date; • up to additional 12.5% SO as of 18 months after the Grant date; • up to additional 12.5 % SO as of 24 months after the Grant date; • up to additional 12.5 % SO as of 30 months after the Grant date; • up to additional 12.5 % SO as of 36 months after the Grant date; • up to additional 12.5 % SO as of 42 months after the Grant date; • up to additional 12.5 % 48 months after the Grant date; • and at the latest before 10 years of the date of the Grant. Grant of 19,100 options as of 01/16/2017, 7,200 options as of 03/15/2017, 16,500 options as of 04/18/2017, 237,600 options as of 06/15/2017, 30,900 options as of 07/17/2017, 52,600 options as of 09/15/2017, 625,200 options as of 12/05/2017 and 8,300 options as of 12/15/2017. All the 2017 options may be exercised by the beneficiary on the basis of the following vesting schedule: • up to 25% SO as of one year after the Grant date; • up to additional 12.5% SO as of 18 months after the Grant date; • up to additional 12.5 % SO as of 24 months after the Grant date; • up to additional 12.5 % SO as of 30 months after the Grant date; • up to additional 12.5 % SO as of 36 months after the Grant date; • up to additional 12.5 % SO as of 42 months after the Grant date; • up to additional 12.5 % 48 months after the Grant date; • and at the latest before 10 years of the date of the Grant. Details of SO Date of grant (Board of Directors) 09/18/2013 06/03/2014 06/23/2015 11/19/2015 01/04/2016 04/21/2016 05/02/2016 Vesting period (years) 4 2 1-4 1-4 1-4 1-4 1-4 Plan expiration date 09/18/2023 06/03/2024 06/23/2025 11/19/2025 01/04/2026 04/21/2026 05/02/2026 Number of SO granted 518,000 75,000 120,000 195,000 75,000 33,000 22,000 Share entitlement per SO 1 1 1 1 1 1 1 Exercise price (in euros) 7.57 19.01 48.9 66.06 65.68 62.82 59.04 Valuation method used Black - Scholes Grant date share fair value (in euros) 7.9 19.01 48.9 66.06 65.68 62.82 58.62 Expected volatility 40 % 40 % 51 % 51 % 49.3%-49.8 % 49.4%-50.7 % 49.3%-50.6 % Average life of SO (in years) 7 6 7 7 5-7 5-7 5-7 Discount rate(1) 1.72 % 0.89 % 0.89 % 0.81 % 0.39 % 0.04 % 0.10 % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA NA Fair value per SO (in euros) 3.57 7.46 25.28 34.05 29.5-32.6 28.3 – 30.9 26.4-28.8 (1) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of SO. Date of grant 06/21/2016 08/01/2016 09/15/2016 10/17/2016 11/15/2016 12/09/2016 12/15/2016 Vesting period (years) 1-4 1-4 1-4 1-4 1-4 1-4 1-4 Plan expiration date 06/21/2026 08/01/2026 09/15/2016 10/17/2026 11/15/2026 12/09/2026 12/15/2026 Number of SO granted 110,000 10,000 9,300 16,500 8,300 74,960 1,100 Share entitlement per SO 1 1 1 1 1 1 1 Exercise price (in euros) 53.96 62.24 62.8 64.39 68.33 69.75 69.35 Valuation method used Black - Scholes Grant date share fair value (in euros) 52.97 62.24 62.8 64.39 68.33 69.75 69.35 Expected volatility 49.1%-50.3 % 48.8%-49.8 % 48.6%-49.4 % 48.0%-48.9 % 47.8%-48.8 % 47.7%-48.5 % 40.44 % Average life of SO (in years) 5-7 5-7 5-7 5-7 5-7 5-7 5-7 Discount rate(1) -0.01 % -0.25 % -0.18 % -0.32 -0.15 % % -0.11 +0.16 % % -0.2 +0.18 % % -0.18 +0.16 % % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA NA Fair val

Financial Revenue and Expenses

Financial Revenue and Expenses	12 Months Ended
	Dec. 31, 2017
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Financial Revenue and Expenses	Note 18: Financial Revenue and Expenses The financial income and expenses are broken down as follows: Year ended December 31, 2015 2016 2017 (thousands of Euros) Financial revenues 1,018 1,646 616 Financial expenses (146 ) (145 ) (3,325 ) Total 871 1,500 (2,709 ) The financial income mainly includes unrealized exchange effect of U.S.-dollar-denominated intercompany advances and capital gains on the disposals of investment securities. The foreign exchange losses and the expenses related to the accretion of the OSEO and BpiFrance advances are classified as financial expenses in the Consolidated Statements of (Loss).

Income Tax Expense

Income Tax Expense	12 Months Ended
	Dec. 31, 2017
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Income Tax Expense	Note 19: Income Tax Expense As mentioned in Note 3.12—Accounting Principles—Other Income, the French Research Tax Credit is not included in the line item “Income taxes” but included in the line item “Other Income.” Reconciliation between the Effective and Nominal Income Tax Expense The following table shows the reconciliation between the effective and nominal tax expense at the nominal standard French rate of 33.33% (excluding additional contributions): Year ended December 31, 2015 2016 2017 (thousands of Euros) (Loss) before taxes (44,674 ) (114,531 ) (147,692 ) Theoretical group tax rate 33.33 % 33.33 % 33.33 % Nominal tax expense 14,890 38,173 49,226 Increase/decrease in tax expense arising from: Permanent differences (1) 6,089 — — Research tax credit 1,895 2,409 3,110 Share-based compensation (3,473 ) (11,451 ) (10,260 ) Non recognition of deferred tax assets related to tax losses and temporary differences (19,211 ) (29,195 ) (41,453 ) Other differences 190 64 622 Effective tax expense — — — Effective tax rate 0 % 0 % 0 % (1) The significant balance of permanent differences is mainly affected by transaction costs on capital increase occurred in 2015. These transaction costs are booked in equity and are subject to a tax deduction. Deferred Tax Assets and Liabilities As mentioned in Note 3.14, the Company has not recognized deferred tax assets in the Consolidated Statements of Financial Position. The amount of the losses carried forward at the end of December 2017 is €369 million including €334 million for DBV Technologies S.A.

Commitments

Commitments	12 Months Ended
	Dec. 31, 2017
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Commitments	Note 20: Commitments Obligations Under the Terms of the Ordinary Rental Agreements The principal offices of the Company occupy a 4,770 square meter facility consisting of office and laboratory space, pursuant to a lease agreement dated March 9, 2015, which expires on March 8, 2024. The Company also two facilities in Bagneux, France. These facilities consist of 2,237 square meters of office and laboratory space and are used primarily by the Company’s industrial and production teams. These facilities are leased under one agreement, which expires on May 31, 2020. The Company has an office in North America to support the U.S. subsidiary as well as future commercialization needs. The Company subleased 3,913 square feet of office space in New York, New York. This sublease expired on June 30, 2017. The Company entered into a similar lease agreement on November 2017. The Company subleases 3,780 square feet of office space in New York, New York. The sublease was signed for an initial period of 5 years. The Company also leases a commercial facility of 8,919 square feet in Summit, New Jersey, which is intended to support the manufacturing needs through the launch and commercialization of Viaskin Peanut in North America, if the appropriate regulatory approvals are received. This lease commenced on September 19, 2016 for a period of eight years and four months. This lease includes extension options of two to five-year periods. The amount of future rents and charges in that capacity breaks down as follows at December 31, 2017: 12/31/2017 2018 2,617 2019 2,623 2020 2,357 2021 2,169 2022 2,119 2023 1,847 2024 1,258 2025 — Total 14,991 The Company has signed various ordinary rental agreements for office equipment and vehicles. The future rental payments as at December 31, 2017 are as follows: • 2018: €116 thousand; • 2019: €77 thousand; • 2020: €70 thousand; • 2021: €16 thousand. Obligations Under the Terms of Other Agreements The Company signed with its bank CIC an acquisition contract of monetary market fund “SICAV CM-CIC” The Company also signed a letter of credit to ensure the sub-lease A letter of credit has also been signed by the Company in April 2016 for $143 thousand to ensure the lease of its premises of its Summit (NJ) subsidiary. This credit note has been extended for an additional year. A letter of credit has also been signed by the Company in May 2017 for $300 thousand to ensure the lease of its premises of its New York subsidiary. In addition, in 2015, the Company took a term deposit for a sum of €227 thousand over 3 years. As it has sub-contracted sub-contracting Within the context of launching its clinical studies for Viaskin Peanuts and Viaskin Milk products, the Company signed agreements with several contract research organizations (CRO). The ongoing studies amount globally to €78.7 million. As of December 31, 2017, the amount remaining to pay as part of these contracts until year end 2021 is €32.6 million. On January 7, 2009, the Company entered into an assignment, development and co-ownership AP-HP, co- AP-HP AP-HP AP-HP AP-HP AP-HP non-exclusive

Relationships with Related Part

Relationships with Related Parties	12 Months Ended
	Dec. 31, 2017
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Relationships with Related Parties	Note 21: Relationships with Related Parties The compensation amounts for 2017 presented below, which were awarded to the members of the Board of Directors and the Executive Committee of the Company totals 15.4 million euros. Following the reorganization of the Company at the beginning of 2015, the Company henceforth considered the members of the Executive Committee to be related parties. December 31, 2015 2016 2017 (thousands of Euros) Members of the Board of Directors 605 714 745 Executive committee 1,768 2,268 2,184 Directors’ fees 195 195 407 Share-based payments to members of the Board of Directors 4,637 13,714 12,018 Total 7,205 16,891 15,353 The methods for the valuation of the benefit related to share-based payments are presented in Note 17. As part of its commercial rollout in the United States, the Company entered into an agreement in December 2016 with one of its Directors for Commercial strategy consulting works. The expenses recorded in 2017 as part of this agreement amounts to €45 thousands. A schedule of amounts payable to related parties as of December 31, 2017: December 31, 2015 2016 2017 (thousands of Euros) Compensation 674 767 689 Directors’ fees 195 195 432 Pension obligations 233 342 402 Total 1,102 1,304 1,523

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2017
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Earnings Per Share	Note 22: Earnings Per Share Taking into account the division of the nominal value of shares of the Company by 15, which was decided by the annual general meeting on December 9, 2011, the amount of shares is adjusted, and multiplying it by 15, for all the outstanding shares presented. The basic earnings per share is calculated by dividing the net income going to the shareholders of the Company by the weighted average number of common shares outstanding during the course of the fiscal year. The weighted average number of shares was 21,522,342 in 2015. The weighted average number of shares was 24,454,850 in 2016. The weighted average number of shares was 24,757,176 in 2017. The instruments that entitle their holders to a portion of the share capital on a deferred basis (BSAs, BSPCEs) are considered to be anti-dilutive (2,033,768 instruments in 2015, 2,360,945 instruments in 2016 and 3,309,539 instruments in 2017). These instruments are presented in detail in Note 17. Therefore, the diluted earnings per share are identical to the basic earnings per share. December 31, 2015 2016 2017 (thousands of Euros) Net income of the reporting period (44,674 ) (114,531 ) (147,693 ) Adjusted weighted average number of outstanding shares 21,522,342 24,454,850 24,757,176 Basic / Diluted earnings per share (€/share) (2.08 ) (4.68 ) (5.97 )

Management of Financial Risks

Management of Financial Risks	12 Months Ended
	Dec. 31, 2017
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Management of Financial Risks	Note 23: Management of Financial Risks The principal financial instruments of the Company are comprised of financial assets, cash, and investment securities. The purpose of managing these instruments is to allow the business activities of the Company to be financed. It is not the Company’s policy to subscribe to financial instruments for speculative purposes. The Company does not utilize derivatives. The principal risks to which the Company is exposed are liquidity risk, interest rate risk and credit risk. Liquidity Risk As of December 31, 2017, the Company had €137.9 million of cash and cash equivalents on hand compared to €256.5 million of cash and cash equivalents as of December 31, 2016. The Company has incurred operating losses and negative cash flows from operations since inception, incurred a net loss of €147.7 million during the year ended December 31, 2017, and has an accumulated deficit and reserves of €279.3 million as of December 31, 2017. Net cash used in operating activities was €114.3 million for the year ended December 31, 2017 and €59.5 million for the year ended December 31, 2016. The Company has primarily funded these losses through equity financings. To date, the Company has no product revenue, and management expects operating losses to continue for the foreseeable future. As the Company continues to actively prepare for the launch of a product in the United States in 2019, if approved, current cash and cash equivalents on hand are not projected to be sufficient to support the Company’s current operating plan for the next 12 months. As such, there are material uncertainties regarding the Company’s ability to continue as a going concern. The Company expects to seek additional funds, most likely from equity or debt financings. To the extent that the Company raises additional funds by issuing equity securities, stockholders may experience significant dilution. However, no assurance can be given at this time as to whether the Company will be able to achieve these financing objective. If the Company does not obtain sufficient funds when needed, the Company could scale back its operating plan, notably by deferring or limiting some or all of its research or development projects. The financial statements have been prepared on a going concern basis assuming that the Company will either be successful in its financing objections or that the Company will modify its operating plans such that the Company’s current cash and cash equivalents will be sufficient to fund the Company’s operations for a period of at least 12 months. As such, no adjustments have been made to the financial statements relating to the recoverability and classification of the asset carrying amounts or classification of liabilities that might be necessary should the Company not be able to continue as a going concern. Interest Rate Risk The Company’s exposure to interest-rate risk primarily involves investment securities. These are composed of money market funds and time deposit accounts. Changes in interest rates have a direct impact on the rate of return on these investments and the cash flows generated. The Company has no variable rate debt. The repayment flows of its debts are not subject to interest rate risk. The repayment of the conditional advances may vary depending on whether or not objectives are attained. The change in the flows of the anticipated repayments is treated in the income statement (Note 3.9). As of this date, the Company has not contracted borrowings from credit institutions and, therefore, has only very low exposure to interest rate risk. Credit Risk The credit risk related to the cash, the cash equivalents, and the current financial instruments is not significant in light of the quality of the co-contracting Fair Value The fair value of financial instruments traded on an active market, such as the securities available for sale, is based on the market rate as of the closing date. The market prices used for the financial assets owned by the Company are the bid prices in effect on the market as of the valuation date. The nominal value, less the provisions for depreciation, of the accounts receivable and current debts, is presumed to approximate the fair value of those items. Foreign Exchange Risk The Company is exposed to a very insignificant foreign exchange risk inherent in some of its supplies obtained in the United States, which have been invoiced in US dollars. As of this date, the company does not make sales revenue in dollars or in any other currency other than the euro; the Company does not receive any full or partial mechanical endorsement. The exposure to currencies other than the U.S. dollar is negligible. For 2015, 2016 and 2017, less than 12%, respectively, of our purchases and other external expenses have been made in U.S. dollars, generating negligible net annual foreign exchange results. In light of these insignificant amounts, the Company has not adopted, at this stage, a hedging mechanism in order to protect its business activity against fluctuations in exchange rates. The Company cannot rule out the possibility that a significant increase in its business, particularly in the United States, may result in greater exposure to exchange rate risk and should thus consider adopting an appropriate policy for hedging against these risks.

Events After the Close of the F

Events After the Close of the Fiscal Year	12 Months Ended
	Dec. 31, 2017
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Events After the Close of the Fiscal Year	Note 24: Events After the Close of the Fiscal Year On February 14, 2018, the Company provided an update on the regulatory progress for Viaskin Peanut and announced that the U.S. Food and Drug Administration (FDA) agreed that the available efficacy and safety data for Viaskin Peanut supported the submission of a Biologics License Application (BLA) for the treatment of peanut allergy in children four to 11 years of age. The FDA provided written responses to the clinical pre-BLA At a meeting held on February 15, 2018, the Board of Directors confirmed that the free shares’ vesting conditions based on the PEPITES trial’s efficacity criteria was achieved. The share-based compensation expense corresponding to the acceleration of the vesting period and related employer’s contribution will be recorded in the first quarter of 2018 for an aggregate amount of approximately €5.4 million. On February 26, 2018, the Company announced preliminary results from Part B, or Phase II, of a Phase I/II study evaluating the efficacy and safety of three dose regimens of Viaskin Milk (150 µg, 300 µg, 500 µg) in 198 patients for the treatment of IgE-mediated Following analyses of the data, the 300 µg dose was identified as the dose with the greatest observed clinical activity for children (intent-to-treat, The Company evaluated all other subsequent events that occurred after December 31, 2017 through the date of issuance of the consolidated financial statements and determined there are no other significant events that require adjustments or disclosure in such consodliated financial statements.

Accounting Principles (Policies

Accounting Principles (Policies)	12 Months Ended
	Dec. 31, 2017
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Going concern	Going concern The Company has primarily funded these losses through equity financings. To date, the Company has no product revenue, and management expects operating losses to continue for the foreseeable future. As the Company continues to actively prepare for the launch of a product in the United States in 2019, if approved, current cash and cash equivalents on hand are not projected to be sufficient to support the Company’s current operating plan for the next 12 months. As such, there are material uncertainties regarding the Company’s ability to continue as a going concern. The Company expects to seek additional funds, most likely from equity or debt financings. To the extent that the Company raises additional funds by issuing equity securities, stockholders may experience significant dilution. However, no assurance can be given at this time as to whether the Company will be able to achieve these financing objective. If the Company does not obtain sufficient funds when needed, the Company could scale back its operating plan, notably by deferring or limiting some or all of its research or development projects. The financial statements have been prepared on a going concern basis assuming that the Company will either be successful in its financing objections or that the Company will modify its operating plans such that the Company’s current cash and cash equivalents will be sufficient to fund the Company’s operations for a period of at least 12 months. As such, no adjustments have been made to the financial statements relating to the recoverability and classification of the asset carrying amounts or classification of liabilities that might be necessary should the Company not be able to continue as a going concern. Refer to the liquidity risk disclosed in Note 23.
Intangible Assets	3.1 Intangible Assets In application of the provisions in IAS 38 Intangible Assets (“IAS 38”), intangible assets acquired are recorded as assets on the Consolidated Statements of Financial Position at their acquisition cost. Research and Development Expenses Research expenses are recorded in the Financial Statements as expenses. In accordance with IAS 38, development expenses are recorded in the Financial Statements as intangible assets only if all the following criteria are met: (a) technical feasibility necessary for the completion of the development project; (b) intention on the part of the Company to complete the project and to utilize it; (c) capacity to utilize the intangible asset; (d) proof of the probability of future economic benefits associated with the asset; (e) availability of the technical, financial, and other resources for completing the project; and (f) reliable evaluation of the development expenses. Because of the risks and uncertainties related to regulatory authorizations and to the research and development process, the Company believes that the six criteria stipulated by IAS 38 are only fulfilled once the Market Access Authorization has been obtained from the competent authorities. The application of this principle has resulted in all development costs being expensed as incurred. Software The costs related to the acquisition of licenses to software are posted to assets on the basis of the costs incurred to acquire and to implement the software in question. They are amortized using the straight-line method over a period of one to three years depending on the anticipated period of use.
Property, Plant, and Equipment	3.2 Property, Plant, and Equipment Property, plant, and equipment are recorded at their acquisition cost or, if applicable, at their production cost. Property, plant, and equipment are depreciated on the basis of the straight-line method over the estimated use period of the property. The fixtures of property rented are depreciated over the term of their own lifetime or of the term of the rental agreement, whichever is shorter. The depreciation periods used are the following: PROPERTY, PLANT, AND EQUIPMENT ITEM DEPRECIATION PERIOD Fixtures and improvements in structures 9 years Research and development / production tools 5 years Research equipment and technical facilities 5 years Computer equipment 3 years Office equipment and furniture 5 years
Financial Assets	3.3 Financial Assets In accordance with IAS 39 ( Financial Instruments: Recognition and Measurement Financial Instruments: Presentation non-derivative Non-derivative Classification, presentation and subsequent measurement of non-derivative Assets Owned Until Their Maturity These securities are exclusively fixed income or determinable income and have fixed maturities, other than loans and accounts receivable, that the Company has the intention and the ability to keep until maturity. After their initial posting at their fair value, they are valued and posted to the accounts at the cost amortized on the basis of the effective interest rate (“EIR”) method. The assets owned until their maturity are monitored for any objective indication of impairment. A financial asset is impaired if its book value is greater than its recoverable amount as estimated during impairment tests. The impairment is recorded to the income statement. Loans and Receivables Loans and receivables are non-derivative non-current The loans and receivables are monitored for any objective indication of impairment. A financial asset is impaired if its book value is greater than its recoverable amount as estimated during impairment tests. The impairment is recorded in the Consolidated Statements of (Loss). The loans and receivables also include the deposits and guarantees, which are classified under “Non-current Assets at Fair Value Per the Consolidated Statements of (Loss) These assets are classified on the balance sheet in the following line items: Other non-current Financial assets at fair value through profit or loss comprise assets held for trading (financial assets acquired principally for the purpose of reselling them in the near term, usually within less than 12 months), and financial instruments designated as fair value through profit and loss on initial recognition in accordance with the conditions for application of the fair value option. Realized and unrealized foreign exchange gains and losses on financial assets in currencies other than the euro are recognized in the income statement in Financial income or Financial expenses. Assets Available for Sale The assets available for sale include, primarily, securities that do not meet the criteria of the definition of the other categories of financial assets. They are measured at their fair value, and the changes in value are recorded in the Consolidated Statements of Changes in Shareholders’ Equity. The fair value corresponds to the market price for those securities that are listed on the stock exchange or to an estimate of the use value for unlisted securities, determined on the basis of the financial criteria most appropriate for the specific situation of each security. When there is an objective indication of the impairment of these securities, the accumulated impairment that has been recorded in the Consolidated Statements of Changes in Shareholders’ Equity is recognized in the Consolidated Statement of (Loss).
Recoverable Amount of the Intangible Assets and Property, Plant, and Equipment	3.4 Recoverable Amount of the Intangible Assets and Property, Plant, and Equipment The property, plant, and equipment and intangible assets that have an established lifetime are subjected to an impairment test when the recoverability of their book value is called into question by the existence of indications of impairment. An impairment is posted to the accounts up to the amount of the excess of the book value over the recoverable value of the asset. The recoverable value of an asset corresponds to its fair value minus the costs of sale or its use value, whichever is higher.
Inventories and Work in Progress	3.5 Inventories and Work in Progress Inventories are recorded at their cost or at their net liquidation value, if the latter is lower. In the latter case, the impairment is posted to income or loss. The inventories are valued on the basis of the “first-in, first-out”
Share Capital	3.6 Share Capital Common shares are classified under Shareholders’ Equity in the Consolidated Statements of Financial Position. The costs of share capital transactions that are directly attributable to the issue of new shares or options are recorded in the Financial Statements in Shareholders’ Equity as a deduction from the revenue from the issue, net of tax.
Payments in Shares	3.7 Payments in Shares Since its incorporation, the Company has established several plans for compensation paid in equity instruments in the form of employee warrants ( bons de souscription de parts de créateur d’entreprise “ bons de souscription d’actions non-employee Pursuant to IFRS 2 Share-based payment The Company has applied IFRS 2 to all equity instruments granted since 2002 to its employees, members of the Board of Directors, other individuals, or to companies. The options are not subject to any market conditions. The characteristics of the options are presented in Note 17.
Recognition and measurement of Financial Liabilities	3.8 Recognition and measurement of Financial Liabilities Financial Liabilities at Amortized Cost Borrowings and other financial liabilities are valued initially at their fair value and then at the amortized cost, calculated on the basis of the effective interest rate (“EIR”) method. The transaction expenses that are directly attributable to the acquisition or to the issue of a financial liability reduce that financial liability. These expenses are then amortized over the lifetime of the liability, on the basis of the EIR. The EIR is the rate that equalizes the anticipated flow of future cash outflows with the current net book value of the financial liability in order to deduct its amortized cost therefrom . Liabilities at Fair Value per the Consolidated Statements of (Loss) The liabilities at fair value per the Consolidated Statements of (Loss) are valued at their fair value.
Subsidies and Conditional Advances	3.9 Subsidies and Conditional Advances Subsidies The Company receives assistance in the form of subsidies, which are grants that are not repayable by the Company. The subsidies are recognized when there is reasonable assurance that: • the Company will comply with the conditions attached to the subsidies, and • the subsidies will be received. Subsidies that are upfront non-refundable the duration of the research program to which the subsidy relates. A public subsidy that is to be received (e.g. from OSEO, the French Agency for Innovation) either as compensation for expenses or for losses already incurred, or for immediate financial support of the Company without associated expenses or losses, is recognized as other income ratably over the duration of the funded project. Conditional advances The Company also receives from time to time assistance in the form of conditional advances, which are advances repayable in whole or in part based upon acknowledgment by the funder of a technical or commercial success of the related project by the funding entity. The details concerning the conditional advances are provided in Note 11. The amount resulting from the deemed benefit of the interest-free nature of the award is considered a subsidy for accounting purposes. This deemed benefit is determined by applying a discount rate equal to the rate of fungible treasury bonds over the time period that corresponds to the time period of the repayment of the advances. In the event of a change in payment schedule of the stipulated repayments of the conditional advances, the Company makes a new calculation of the net book value of the debt resulting from the discounting of the expected new future cash flows. The adjustment that results therefrom is recognized in the income statement for the fiscal year during which the modification is recognized. The conditional advances that can be subject to this type of modification are the with Compagnie Française d’Assurance pour le Commerce Extérieur (“COFACE”) advances presented in Note 11. The agreement with COFACE terminated on December 31, 2016.
Provisions	3.10 Provisions Provisions for Risks and Expenses The provisions for risks and lawsuits correspond to the commitments resulting from lawsuits and various risks whose due dates and amounts are uncertain. A provision is posted to the accounts when the Company has a legal or implicit obligation to a third party resulting from a past event, concerning which it is likely or certain that it will cause an outflow of resources to that third party, without consideration that is anticipated to be at least equivalent to the latter, and that the future outflows of liquid assets can be estimated reliably. The amount recorded in the accounts as a provision is the best estimation of the expenses necessary to extinguish the obligation. Pension Retirement Obligations The employees of the Company receive the retirement benefits stipulated by law in France: • obtaining a compensation paid by the Company to employees upon their retirement (defined-benefit plan); • payment of retirement pensions by the Social Security agencies, which are financed by the contributions made by companies and employees (defined-contribution plans). For the defined-benefit plans, the costs of the retirement benefits are estimated by using the projected credit unit method. According to this method, the cost of the retirement pensions is recognized in the Consolidated Statements of (Loss) so that it is distributed uniformly over the term of the services of the employees. The retirement benefit commitments are valued at the current value of the future payments estimated using, for the discounting, the market rate based on the long-term obligations of the first-category companies with a term that corresponds to that estimated for the payment of the services provided. The Company relies on external actuaries to conduct an annual review of the valuation of these plans. The difference between the amount of the provision at the beginning of a fiscal year and at the close of that year is recognized through profit or loss for the portion representing the costs of services rendered and through other comprehensive income for the portion representing the actual gains and losses. The Company’s payments for the defined-contribution plans are recognized as operating expenses on the Consolidated Statements of (Loss) of the period with which they are associated.
Revenue	3.11 Revenue The revenue of the Company resulted in previous years mainly from the sale of the product Diallertest The Company recognizes revenue when the amount can be measured reliably, when it is likely that the future economic advantages will benefit the Company, and when the specific criteria are met for the business activity of the Company. For product sales, the sales revenue is recognized upon delivery.
Other Income	3.12 Other Income Subsidies Since it was formed, because of its innovative character, the Company has received a certain number of sources of assistance or subsidies from the central government or from local public authorities such as OSEO or the Banque Publique d’Investissement, intended to finance its operations or the recruitment of specific personnel. When the obtention of the subsidy is reasonably certain, these subsidies are recognized as “Other income” during the calendar year over which the corresponding expenses or expenditures were recorded. Research Tax Credit The Research Tax Credit (Crédit d’Impôt Recherche, CIR) is granted to companies by the French tax authorities in order to encourage them to conduct technical and scientific research. Companies that prove that they have expenditures that meet the required criteria (research expenditures located in France or, since January 1, 2005, within the European Community or in another State that is a party to the Agreement on the European Economic Area that has concluded a tax treaty with France that contains an administrative assistance clause) receive a tax credit that can be used for the payment of the corporate tax due for the fiscal year in which the expenditures were made and the next three fiscal years, or, as applicable, can be reimbursed for the excess portion. The expenditures taken into account for the calculation of the research tax credit involve only research expenses. The Company has received the Research Tax Credit annually since it was formed. The Company received the reimbursement of the 2014 Research Tax Credit for an amount of €4.3 million during the year 2015. The Company received the reimbursement of the 2015 Research Tax Credit for an amount of €5.7 million during the year 2016. The Company received the reimbursement of the 2016 Research Tax Credit for an amount of €7.3 million during the year 2017. The Company will request the reimbursement of the 2017 Research Tax Credit for an amount of €9.2 million during the year 2018, under the community tax rules for small and medium firms in compliance with the regulatory texts applicable. Collaboration agreement with Nestlé Health Science On May 31, 2016, the Company announced its entry into an exclusive global collaboration with Nestlé Health Science to develop MAG1C, a ready-to-use non-refundable In accordance with International Accounting Standard 18, upfront payments and milestones received under the Company’s collaboration agreement are deferred and recognized over the service period obligation. Upon entry into the collaboration agreement, the Company’s management estimated the expected service period obligation, as well as the cost involved in the project. Upfront payments and milestones are recognized on a straight line basis or, if the associated costs can be reliably estimated, based on the cost incurred under the project. Periodically, the Company reassesses the estimated time and cost to complete the project and adjusts the time period over which the revenue is deferred accordingly. If the outcome of a contract cannot be estimated reliably, revenue is recognized only to the extent of costs incurred that it is probable will be recoverable, in accordance with International Accounting Standard 11. As of December 31, 2017, we had recorded deferred revenue of €9.5 million related to our collaboration with Nestlé Health Science, which will be deferred and recognized ratably over the service obligation period. We expect the service obligation period to be completed in the second half of 2021. Deferred revenue is included in other current and non-current
Rental Agreements	3.13 Rental Agreements The rental agreements involving property, plant, and equipment are classified as finance lease agreements when the Company bears a substantial portion of all the benefits and risks inherent in the ownership of the property. The assets that are covered under financing lease agreements are capitalized as of the beginning date of the rental agreement on the basis of the fair value of the rented asset or the discounted values of the future minimum payments, whichever is lower. Each rental payment is distributed between the debt and the financial cost in such a manner as to determine a constant interest rate on the principal that remains due. The corresponding rental obligations, net of the financial expenses, are classified as financial liabilities. The portion of the financial expense that corresponds to the interest is recognized as an expense over the term of the agreement. The property, plant, or equipment acquired within the framework of a finance lease agreement is amortized over the use period or the term of the lease agreement, whichever is shorter. The rental agreements for which a significant portion of the risks and advantages is preserved by the lessor are classified as ordinary rental agreements. The payments made for these ordinary rental agreements, net of any incentive measures, are recognized as operating expenses on the Consolidated Statements of (Loss) in a linear manner over the term of the agreement.
Taxes	3.14 Taxes Income Tax Deferred taxes are recognized for all the temporary differences arising from the difference between the tax basis and the accounting basis of the assets and liabilities that appear in the financial statements. The primary temporary differences are related to the tax losses that can be carried forward or backward. The tax rates that have been ratified by a legal text as of the closing date are utilized to determine the deferred taxes. The deferred tax assets are recorded in the accounts only to the extent that it is likely that the future profits will be sufficient to absorb the losses that can be carried forward or backward. Considering its stage of development, which does not allow income projections judged to be sufficiently reliable to be made, the Company has not recognized deferred tax assets in relation to tax losses carryforward in the Consolidated Statements of Financial Position.
Segment Information	3.15 Segment Information The Company operates in a single operating segment: the conducting of research and development of epicutaneous immunotherapy products in order to market them in the future. The assets, liabilities, and operating losses recognized are primarily located in France.
Other Items in the Comprehensive income (loss)	3.16 Other Items in the Comprehensive income (loss) The revenue and expense items for the period that are not posted in the Consolidated Statements of (Loss) as stipulated by the applicable standards are presented, as necessary, under the rubric “Other comprehensive income (loss).”
Use of Estimates	3.17 Use of Estimates The preparation of our Consolidated Financial Statements requires the management to make estimates, assumptions and judgments that affect the reported amounts of assets, liabilities, revenue and expenses. Estimates and assumptions are based on historical experience and other factors that management believes to be reasonable under the circumstances. Estimates and assumptions are measured on an ongoing basis. Actual results may differ from these estimates. These estimates and judgments mainly involve: • a valuation of the fair value of the employee warrants (BSPCEs) granted to employees and/or executives and share warrants (BSAs) granted to non-employee • an estimate of the Research Tax Credit based on internal and external expenses incurred by the Company during the year. Only eligible research expenses are included in the calculation of the research tax credit.
Presentation of Financial Assets and Financial Liabilities Measured at Fair Value	3.18 Presentation of Financial Assets and Financial Liabilities Measured at Fair Value • In accordance with the amendments to IFRS 7, financial instruments are presented in three categories based on a hierarchical method used to determine their fair value: • level 1: fair value calculated using quoted prices in an active market for identical assets and liabilities; • level 2: fair value calculated using valuation techniques based on observable market data such as prices of similar assets and liabilities or parameters quoted in an active market; • level 3: fair value calculated using valuation techniques based wholly or partly on unobservable inputs such as prices in an inactive market or a valuation based on multiples for unlisted securities.
Subsequent events	3.19 Subsequent events The Consolidated Financial Statements are adjusted to reflect the subsequent events that alter the amounts related to the situations that exist as of the closing date. The adjustments are made until the date the consolidated financial statements are approved and authorized for issuance by the Board of Directors.

Accounting Principles (Tables)

Accounting Principles (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Depreciation Periods	The depreciation periods used are the following: PROPERTY, PLANT, AND EQUIPMENT ITEM DEPRECIATION PERIOD Fixtures and improvements in structures 9 years Research and development / production tools 5 years Research equipment and technical facilities 5 years Computer equipment 3 years Office equipment and furniture 5 years

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Intangible Assets	The intangible assets are broken down as follows: December 31, 2015 2016 2017 (thousands of Euros) Patents, licenses, trademarks 54 196 414 Software 302 376 450 Total, gross 356 572 864 Accumulated amortization of patents, licenses, and trademarks 53 125 340 Accumulated depreciation of software packages 210 351 401 Accumulated amortization and depreciation 262 476 741 Total, net 94 96 123

Property, Plant, and Equipment

Property, Plant, and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Property, Plant, and Equipment	1/1/2015 Increase Decrease 12/31/2015 (thousands of Euros) Laboratory equipment 2,257 467 (368 ) 2,357 Building fixtures 930 8 — 938 Office equipment 215 24 (30 ) 209 Computer equipment 322 244 (95 ) 470 Property, plant, and equipment in progress 51 3,622 — 3,672 Total, gross 3,775 4,365 (493 ) 7,646 Accumulated depreciation of laboratory equipment 916 382 (349 ) 948 Accumulated depreciation of the building fixtures 286 496 — 782 Accumulated depreciation of office equipment 126 35 (30 ) 131 Accumulated depreciation of computer equipment 222 78 (95 ) 205 Total accumulated amortization and depreciation 1,550 990 (475 ) 2,065 Total, net 2,225 3,375 18 5,581 1/1/2016 Increase Decrease 12/31/2016 (thousands of Euros) Laboratory equipment 2,357 740 — 3,097 Building fixtures 938 3,672 — 4,610 Office equipment 209 398 — 607 Computer equipment 470 516 — 986 Property, plant, and equipment in progress 3,672 2,713 — 6,385 Total, gross 7,646 8,039 — 15,685 Accumulated depreciation of laboratory equipment 948 557 — 1,505 Accumulated depreciation of the building fixtures 782 327 — 1,109 Accumulated depreciation of office equipment 131 81 — 212 Accumulated depreciation of computer equipment 205 172 — 377 Total accumulated amortization and depreciation 2,065 1,137 — 3,203 Total, net 5,581 6,901 — 12,482 1/1/2017 Increase Decrease 12/31/2017 (thousands of Euros) Laboratory equipment 3,097 2,806 (83 ) 5,820 Building fixtures 4,610 534 (46 ) 5,098 Office equipment 607 275 (116 ) 766 Computer equipment 986 116 (30 ) 1,073 Property, plant, and equipment in progress 6,385 3,384 (55 ) 9,714 Total, gross 15,685 7,114 (329 ) 22,470 Accumulated depreciation of laboratory equipment 1,505 802 (63 ) 2,244 Accumulated depreciation of the building fixtures 1,109 484 (14 ) 1,580 Accumulated depreciation of office equipment 212 213 (105 ) 320 Accumulated depreciation of computer equipment 377 172 (30 ) 520 Total accumulated amortization and depreciation 3,202 1,671 (211 ) 4,663 Total, net 12,482 5,443 (118 ) 17,808

Non-CurrentFinancial Assets (Ta

Non-CurrentFinancial Assets (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Non-Current Financial Assets	December 31, 2015 2016 2017 (thousands of Euros) Deposits 716 824 577 Pledged securities and other non-current 611 611 1,102 Liquidity contract 1,384 1,310 1,333 Total non-current 2,711 2,745 3,012

Inventories and Work in Progr36

Inventories and Work in Progress (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Inventories	December 31, 2015 2016 2017 (thousands of Euros) Inventories of raw materials 69 69 — Depreciation of inventories (69 ) (69 ) — Total net value of the inventories — — —

Customer Accounts Receivable 37

Customer Accounts Receivable and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Customer Accounts Receivable and Related Receivables	Customer Accounts Receivable and Related Receivables December 31, 2015 2016 2017 (thousands of Euros) Accounts receivable 13 1,263 1,265 Valuation allowance (13 ) (13 ) — Total net value of accounts receivable — 1,250 1,265
Summary of Other Current Assets	The other current assets are broken down as follows: December 31, 2015 2016 2017 (thousands of Euros) Research tax credit 5,702 7,228 9,217 Other tax claims 2,550 2,618 5,258 Other receivables 1,409 1,883 1,192 Prepaid expenses 1,850 2,725 2,054 Total 11,512 14,454 17,721
Reconcilliation of Research Tax Credit	The changes in this Research Tax Credit over the last three years are presented as follows: thousands of Euros Opening Balance Sheet Receivable as of January 1, 2015 4,340 + Other income 5,702 - Payment received (4,322 ) - Adjustment (18 ) Closing Balance Sheet Receivable as of December 31, 2015 5,702 thousands of Euros Opening Balance Sheet Receivable as of January 1, 2016 5,702 + Other income 7,228 - Payment received (5,702 ) - Adjustment — Closing Balance Sheet Receivable as of December 31, 2016 7,228 thousands of Euros Opening Balance Sheet Receivable as of January 1, 2017 7,228 + Other income 9,217 - Payment received (7,341 ) - Adjustment 113 Closing Balance Sheet Receivable as of December 31, 2017 9,217

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Cash and Cash Equivalents	The cash and cash equivalents item is broken down as follows : December 31, 2015 2016 2017 (thousands of Euros) Cash 178,895 146,374 32,054 Cash equivalent term deposits 144,486 110,100 105,826 Total cash and cash equivalent as reported in statement of financial position 323,381 256,473 137,880 Bank overdrafts — — — Total net cash and cash equivalents as reported in the statement of cash flow 323,381 256,473 137,880

Capital (Tables)

Capital (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Historical Changes in the Share Capital of the Company	The table below presents the historical changes in the share capital of the Company as of December 31, 2015, 2016 and 2017: Date Nature of the Transactions Share Share premium Number of Nominal Balance as of January 1, 2015 K € 1,916.1 K € 163,876.8 19,160,661 € 0.10 01/06/2015 Capital increase by issuance of common shares K€ 0.4 K€ 18.9 3,750 € 0.10 01/07/2015 Capital increase by issuance of common shares K€ 1.0 K€ 59.0 10,000 € 0.10 01/22/2015 Capital increase by incorporation of reserve K€ 3.5 K€ (3.5 ) 35,360 € 0.10 01/30/2015 Capital increase by issuance of common shares K€ 9.8 K€ 476.8 97,720 € 0.10 02/03/2015 Capital increase by issuance of common shares K€ 0.8 K€ 37.7 7,500 € 0.10 02/13/2015 Capital increase by issuance of common shares K€ 3.8 K€ 188.6 37,500 € 0.10 02/17/2015 Capital increase by issuance of common shares K€ 2.0 K€ 100.6 19,995 € 0.10 03/04/2015 Capital increase by issuance of common shares K€ 1.0 K€ 59 10,000 € 0.10 03/26/2015 Capital increase by issuance of common shares K€ 5.0 K€ 400 50,000 € 0.10 04/07/2015 Capital increase by issuance of common shares K€ 4.0 K€ 169.2 40,005 € 0.10 04/09/2015 Capital increase by issuance of common shares K€ 15.0 K€ 692.1 150,375 € 0.10 04/28/2015 Capital increase by issuance of common shares K€ 1.4 K€ 77.1 14,290 € 0.10 05/05/2015 Issue of share subscription warrants K€ K€ 43 05/11/2015 Capital increase by issuance of common shares K€ 2.0 K€ 100.7 20,010 € 0.10 06/23/2015 Capital increase by issuance of common shares K€ 59.1 K€ 27,029.4 590,543 € 0.10 06/23/2015 Capital Decrease K€ (58.6 ) K€ (26,823.4 ) (586,048 ) € 0.10 07/20/2015 Capital increase by issuance of common shares K€ 414.0 K€ 254,932.9 4,140,000 € 0.10 07/24/2015 Capital increase by issuance of common shares K€ 1.6 K€ 79.2 15,750 € 0.10 07/25/2015 Capital increase by incorporation of reserve K€ 28.6 K€ (28.6 ) 286,338 € 0.10 07/28/2015 Capital increase by issuance of common shares K€ 1.7 K€ 91.5 17,000 € 0.10 09/18/2015 Capital increase by issuance of common shares K€ 0.3 K€ 46.7 2,500 € 0.10 10/07/2015 Capital increase by issuance of common shares K€ 4.8 K€ 241.2 47,955 € 0.10 12/10/2015 Capital increase by issuance of common shares K€ 1.8 K€ 146.9 17,500 € 0.10 12/10/2015 Issue of share subscription warrants K€ K€ 99.2 12/14/2015 Capital increase by issuance of common shares K€ 1.6 K€ 69.5 16,425 € 0.10 12/31/2015 Fees charged to share premium K€ K€ (18,269.7 ) Balance as of December 31, 2015 K€ 2,420.5 K€ 403,910.4 24,205,129 € 0.10 Date Nature of the Transactions Share Share premium Number of Nominal Balance as of January 1, 2016 K € 2,420.5 K € 403,910.4 24,205,129 € 0.10 01/05/16 Capital increase by issuance of common shares K€ 0.6 K€ 32.7 6,495 02/16/16 Issue of share subscription warrants K€ K€ 471.1 € 0.10 04/06/16 Capital increase by incorporation of reserve K€ 10.2 K€ (10.2 ) 101,829 € 0.10 05/27/16 Capital increase by issuance of common shares K€ 0.2 K€ 7.5 1,500 € 0.10 06/03/16 Capital increase by issuance of common shares K€ 15.6 K€ (15.6 ) 156,000 € 0.10 06/06/16 Capital increase by issuance of common shares K€ 6.0 K€ 301.2 59,890 € 0.10 06/10/16 Capital increase by issuance of common shares K€ 3.5 K€ 176.0 34,985 € 0.10 07/18/16 Capital increase by issuance of common shares K€ 2.0 K€ 100.7 20,010 € 0.10 08/21/16 Issue of share subscription warrants K€ K€ 106 € 08/04/16 Capital increase by issuance of common shares K€ 1.0 K€ 50.4 10,020 € 0.10 08/24/16 Capital increase by issuance of common shares K€ 0.7 K€ 37.1 7,380 € 0.10 08/30/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 08/31/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/01/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/02/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/05/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/06/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/06/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/08/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/09/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/12/16 Capital increase by issuance of common shares K€ 0.4 K€ 66.2 3,500 € 0.10 09/12/16 Capital increase by issuance of common shares K€ 0.5 K€ 23.1 4,590 € 0.10 11/25/16 Capital increase by issuance of common shares K€ 0.6 K€ 30.2 6,000 € 0.10 Balance as of December 31, 2016 K€ 2,464.9 K€ 405,882.5 24,648,828 € 0.10 Date Nature of the Transactions Share Capital Share premium Number of Nominal Balance as of January 1, 2017 K € 2,464.9 K € 405,882.5 24,648,828 € 0.10 02/03/17 Capital increase by issuance of common shares K€ 2.0 K€ 100.7 20,010 € 0.10 02/09/17 Issue of share subscription warrants K€ K€ 237.4 € 05/16/17 Capital increase by issuance of common shares K€ 4.0 K€ 170.7 40,365 € 0.10 07/12/17 Capital increase by issuance of common shares K€ 0.2 K€ 8.3 1,650 € 0.10 08/04/17 Capital increase by issuance of common shares K€ 0.1 K€ 64.6 1,200 € 0.10 09/14/17 Capital increase by issuance of common shares K€ 3.6 K€ 208.2 35,925 € 0.10 09/14/17 Issue of share subscription warrants K€ K€ 53.1 € 09/29/17 Capital increase by issuance of common shares K€ 0.1 K€ 4.0 500 € 0.10 09/30/17 Capital increase by incorporation of reserve K€ 23.1 K€ (23.1 ) 230,843 € 0.10 10/02/17 Capital increase by issuance of common shares K€ 0.1 K€ 4.0 500 € 0.10 12/15/17 Capital increase by incorporation of reserve K€ 1.1 K€ (1.1 ) 11,001 € 0.10 Balance as of December 31, 2017 K€ 2,499.1 K€ 406,709.3 24,990,822 € 0.10
Summary of Share Warrants and Employee Warrants	The Company has issued share warrants (BSAs), employee warrants (BSPCEs), performance shares (AGAs) and stock-options (SO) as follows: Date Type Number of Number of Number of Maximum Strike price 12/07/2007 BSA 1,717 572 859 12,885 € 4.33 01/21/2009 BSA/BSPCE 16,380 — 4,041 60,615 € 4.33 01/21/2009 BSPCE 2,296 — — — € 4.33 06/25/2010 BSA 1,825 — 730 10,950 € 4.33 01/28/2011 BSA 10,039 7,529 — — € 5.13 06/24/2011 BSA/BSPCE 32,000 — 13,465 201,975 € 5.13 11/22/2011 BSA/BSPCE 11,377 — 2,509 37,635 € 5.13 01/17/2012 BSA 89,835 — 89,835 89,835 € 5.13 04/02/2012 AGA 669,796 1,860 — — € — 07/25/2012 AGA 134,081 — — — € — 09/25/2012 BSA 30,000 — 10,000 10,000 € 8.59 11/28/2012 AGA 35,360 — — — € — 07/25/2013 BSA 73,000 — 13,000 13,000 € 8.10 09/12/2013 AGA 501,500 113,333 101,829 101,829 € — 09/18/2013 SO 518,000 47,000 471,000 471,000 € 7.57 06/03/2014 BSA 10,000 — 5,000 5,000 € 18.79 06/03/2014 AGA 186,000 30,000 156,000 156,000 € — 06/03/2014 SO 75,000 — 75,000 75,000 € 19.01 03/24/2015 BSA 10,000 — 10,000 10,000 € 43.00 06/23/2015 SO 120,000 — 120,000 120,000 € 48.90 09/30/2015 AGA 708,500 — 708,500 708,500 € — 11/19/2015 SO 195,000 — 195,000 195,000 € 66.06 11/19/2015 BSA 22,500 7,500 15,000 15,000 € 66.06 12/15/2015 AGA 42,000 — 42,000 42,000 € — Total 3,496,206 207,794 2,033,768 2,336,224 Date Type Number of Number of Number of Maximum Strike price 12/07/2007 BSA 1,717 572 859 12,885 € 4.33 01/21/2009 BSA/BSPCE 16,380 — 2,997 44,955 € 4.33 01/21/2009 BSPCE 2,296 — — — € 4.33 06/25/2010 BSA 1,825 — 730 10,950 € 4.33 01/28/2011 BSA 10,039 7,529 — — € 5.13 06/24/2011 BSA/BSPCE 32,000 — 10,440 156,600 € 5.13 11/22/2011 BSA/BSPCE 11,377 — 2,509 37,635 € 5.13 01/17/2012 BSA 89,835 — — — € 5.13 04/02/2012 AGA 669,796 1,860 — — € — 07/25/2012 AGA 134,081 — — — € — 09/25/2012 BSA 30,000 — 10,000 10,000 € 8.59 11/28/2012 AGA 35,360 — — — € — Date Type Number of Number of Number of Maximum Strike price 07/25/2013 BSA 73,000 — 13,000 13,000 € 8.10 09/12/2013 AGA 501,500 113,333 — — € — 09/18/2013 SO 518,000 47,000 471,000 471,000 € 7.57 06/03/2014 BSA 10,000 — 5,000 5,000 € 18.79 06/03/2014 AGA 186,000 30,000 — — € — 06/03/2014 SO 75,000 — 40,000 40,000 € 19.01 03/24/2015 BSA 10,000 — 10,000 10,000 € 43.00 06/23/2015 SO 120,000 — 120,000 120,000 € 48.90 09/30/2015 AGA 708,500 13,000 695,500 695,500 € — 11/19/2015 SO 195,000 25,000 170,000 170,000 € 66.06 11/19/2015 BSA 22,500 7,500 15,000 15,000 € 66.06 12/15/2015 AGA 42,000 6,000 36,000 36,000 € — 12/15/2015 BSA 90,000 16,500 73,500 73,500 € 64.14 01/04/2016 SO 75,000 — 75,000 75,000 € 65.68 04/06/2016 AGA 63.750 5,000 58,750 58,750 € — 04/21/2016 SO 33,000 — 33,000 33,000 € 62.82 05/02/2016 SO 22,000 — 22,000 22,000 € 59.04 06/21/2016 SO 110,000 — 110,000 110,000 € 53.96 06/21/2016 BSA 20,000 — 20,000 20,000 € 52.97 06/21/2016 AGA 208,000 — 208,000 208,000 € — 08/01/2016 SO 10,000 — 10,000 10,000 € 62.24 09/15/2016 SO 9,300 — 9,300 9,300 € 62.80 10/17/2016 SO 16,500 — 16,500 16,500 € 64.39 10/27/2016 AGA 15,000 — 15,000 15,000 € — 11/15/2016 SO 8,300 — 8,300 8,300 € 68.33 12/09/2016 SO 74,960 — 74,960 74,960 € 69,75 12/09/2016 AGA 23,600 — 23,600 23,600 € — Total 4,275,616 273,294 2,360,945 2,606,435 Date Type Number of Number of Number of Maximum Strike price 12/07/2007 BSA 1,717 572 — — € 4.33 01/21/2009 BSA/BSPCE 16,380 — — — € 4.33 01/21/2009 BSPCE 2,296 — — — € 4.33 06/25/2010 BSA 1,825 — — — € 4.33 01/28/2011 BSA 10,039 7,529 — — € 5.13 06/24/2011 BSA/BSPCE 32,000 — 8,996 134,940 € 5.13 11/22/2011 BSA/BSPCE 11,377 — 2,509 37,635 € 5.13 01/17/2012 BSA 89,835 — — — € 5.13 04/02/2012 AGA 669,796 1,860 — — € — 07/25/2012 AGA 134,081 — — — € — 09/25/2012 BSA 30,000 — 7,500 7,500 € 8.59 11/28/2012 AGA 35,360 — — — € — 07/25/2013 BSA 73,000 — 9,500 9,500 € 8.10 09/12/2013 AGA 501,500 113,333 — — € — 09/18/2013 SO 518,000 47,000 471,000 471,000 € 7.57 06/03/2014 BSA 10,000 — 2,500 2,500 € 18.79 06/03/2014 AGA 186,000 30,000 — — € — 06/03/2014 SO 75,000 — 40,000 40,000 € 19.01 03/24/2015 BSA 10,000 — 10,000 10,000 € 43.00 Date Type Number of Number of Number of Maximum Strike price 06/23/2015 SO 120,000 — 120,000 120,000 € 48.90 09/30/2015 AGA 708,500 23,000 454,657 454.657 € — 11/19/2015 SO 195,000 25,000 170,000 170,000 € 66.06 11/19/2015 BSA 22,500 7,500 15,000 15,000 € 66.06 12/15/2015 AGA 42,000 9,000 21,999 21,999 € — 12/15/2015 BSA 90,000 16,500 73,500 73,500 € 64.14 01/04/2016 SO 75,000 — 75,000 75,000 € 65.68 04/06/2016 AGA 63.750 6,250 57,500 57,500 € — 04/21/2016 SO 33,000 — 33,000 33,000 € 62.82 05/02/2016 SO 22,000 — 22,000 22,000 € 59.04 06/21/2016 SO 110,000 7,500 101,300 101,300 € 53.96 06/21/2016 BSA 20,000 — 20,000 20,000 € 52.97 06/21/2016 AGA 208,000 — 208,000 208,000 € — 08/01/2016 SO 10,000 — 10,000 10,000 € 62.24 09/15/2016 SO 9,300 — 9,300 9,300 € 62.80 10/17/2016 SO 16,500 7,200 9,300 9,300 € 64.39 10/27/2016 AGA 15,000 — 15,000 15,000 € — 11/15/2016 SO 8,300 — 8,300 8,300 € 68.33 12/09/2016 SO 74,960 2,000 72,000 72,000 € 69,75 12/09/2016 AGA 23,600 1,900 21,700 21,700 € — 12/09/2016 BSA 59,000 24,992 34,008 34,008 € 69.75 12/15/2016 SO 1,100 — 1,100 1,100 € 69.35 01/16/2017 SO 19,100 — 19,100 19,100 € 66.11 03/14/2017 AGA 22,500 2,500 20,000 20,000 € — 03/15/2017 SO 7,200 — 7,200 7,200 € 66.25 04/18/2017 SO 16,500 — 16,500 16,500 € 60.77 04/20/2017 AGA 24,000 — 24,000 24,000 € — 06/15/2017 SO 126,000 7,500 118,500 118,500 € 59.05 06/15/2017 SO 111,600 — 111,600 111,600 € 60.54 06/15/2017 BSA 9,000 — 9,000 9,000 € 59.05 07/17/2017 SO 30,900 — 30,900 30,900 € 71.61 09/15/2017 SO 52,600 — 52,600 52,600 € 74.22 12/05/2017 SO 625,200 — 625,200 625,200 € 39.00 12/15/2017 SO 8,300 — 8,300 8,300 € 38.08 Total 5,388,616 341,196 3,148,469 3,309,539

Financial and Other Non-Curre40

Financial and Other Non-Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Debt Recorded on Statement of Financial Position	The table below presents the details of the debts recorded on the Consolidated Statements of Financial Position by the type of conditional advance: 3rd OSEO contract 4th OSEO contract BPI advance COFACE Total Balance sheet debt at start of period 01/01/2015 507 805 2,584 151 4,047 Receipts — 865 — — 865 Repayments (192 ) — — — (192 ) Other transactions 3 (2 ) 82 5 89 Balance sheet debt as at 12/31/2015 318 1,669 2,666 156 4,809 Of which - non-current 4,681 Of which - current portion 128 Stated interest rate No 2,05 % No No Discount rate 0.4%-1.9 % 1.5%-1.8 % 3.20 % 4.25 % Maturity (in years) 0-3 7-9 2-7 0 3rd OSEO contract 4th OSEO contract BPI advance COFACE Total Balance sheet debt at start of period 01/01/2016 318 1,669 2,666 156 4,809 Receipts — — — — — Repayments (128 ) — — (147 ) (275 ) Other transactions 2 16 85 (9 ) 95 Balance sheet debt as at 12/31/2016 192 1,684 2,751 — 4,628 Of which - non-current 4,049 Of which - current portion 578 Stated interest rate No 2,05 % No No Discount rate 0.4%-1.9 % 1.5%-1.8 % 3.20 % 4.25 % Maturity (in years) 0-3 7-9 2-7 0 3rd OSEO contract 4th OSEO contract BPI advance Total Balance sheet debt at start of period 01/01/2017 192 1,684 2,751 4,628 Receipts — — — — Repayments (128 ) — (450 ) (578 ) Other transactions 1 16 84 101 Balance sheet debt as at 12/31/2017 64 1,700 2,386 4,150 Of which - non-current 1,825 Of which - current portion 2,325 Stated interest rate No 2,05 % No Discount rate 0.4%-1.9 % 1.5%-1.8 % 3.2 % Maturity (in years) 0-3 7-9 2-7
Summary of Due Dates of the Financial Liabilities	Due dates of the financial liabilities recognized as of December 31, 2015: Gross Less than One One to Five More than (thousands of Euros) Non-current 4,681 — 2,378 2,302 Non-current 12 — 12 — Current conditional advances 128 128 — — Current financial rent debts 21 21 — — Supplier accounts payable and related payables 10,034 10,034 — — Total financial liabilities 14,876 10,183 2,391 2,302 Due dates of the financial liabilities recognized as of December 31, 2016: Gross Less than One One to Five More than (thousands of Euros) Non-current 4,049 — 2,531 1,518 Non-current — — — — Other non-current 10,746 — 10,370 377 Current conditional advances 578 578 — — Current financial rent debts 12 12 — — Other current liabilities 14,692 14,692 — — Supplier accounts payable and related payables 13,720 13,720 — — Total financial liabilities 43,798 29,003 12,900 1,895 Due dates of the financial liabilities recognized as of December 31, 2017: Gross amount Less than One One to Five More than (thousands of Euros) Non-current 1,825 — 1,825 — Non-current — — — — Other non-current 8,869 — 8,421 448 Current conditional advances 2,325 2,325 — — Current financial rent debts — — — — Other current liabilities 15,751 15,751 — — Supplier accounts payable and related payables 16,941 16,941 — — Total financial, current and non-current 45,711 35,017 10,246 448

Non-Current Provisions (Tables)

Non-Current Provisions (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Schedule of Non-Current Provisions	December 31, 2015 2016 2017 (thousands of euros) Pension retirement obligations 490 853 1,260 Total 490 853 1,260
Schedule of Commitments for Compensation Payable to Employees Upon Their Retirement	Commitments for Compensation Payable to Employees Upon Their Retirement thousands of As of January 1, 2015 (531 ) Costs of services rendered (operating expense) (116 ) Interest expense (finance expense) (9 ) Benefit paid Actuarial gains 166 As of December 31, 2015 (490 ) Costs of services rendered (operating expense) (104 ) Interest expense (finance expense) (10 ) Benefit paid — Actuarial losses (249 ) As of December 31, 2016 (853 ) Costs of services rendered (operating expense) (219 ) Interest expense (finance expense) (11 ) Benefit paid — Actuarial losses (177 ) As of December 31, 2017 (1,260 )
Schedule of Retirement Commitments	As part of the estimation of the retirement commitments, the following assumptions were used for all categories of employees: December 31, 2015 2016 2017 % social security contributions 50.0 % 50.0 % 50.0 % Salary increases 2.0 % 2.0 % 2.0 % Discount rate 2.08 % 1.31 % 1.30 %

Supplier Accounts Receivable 42

Supplier Accounts Receivable and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Schedule of Other Current Liabilities	Other Current Liabilities December, 31 2015 2016 2017 (thousands of Euros) Social security 4,464 10,794 12,094 Tax liabilities 388 504 428 Other debts 195 146 440 Deferred revenues 791 3,248 2,789 Total 5,838 14,692 15,751

Financial Instruments Recogni43

Financial Instruments Recognized in the Consolidated Statements of Financial Position and Related Effect on the Consolidated Statements of (Loss) (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Schedule of Financial Instruments Recognized in the Consolidated Statements of Financial Position and Related Effect on the Consolidated Statements of (Loss)	2015 Book value in Fair value Loans and (1) Debt At Fair value Financial assets Long-term financial assets 2,711 1,365 1,346 — 2,711 Customer accounts receivables and related receivables — — — — — Other current financial assets 333 — 333 — 333 Cash and cash equivalents 323,381 323,381 — — 323,381 Total financial assets 326,425 324,746 1,679 — 326,425 Financial liabilities Long-term conditional advances 4,681 — — 4,681 4,681 Long term financial rent debt 12 — — 12 12 Short-term conditional advances 128 — — 128 128 Short term financial rent debt 21 — — 21 21 Account payable and other liabilities 15,872 — — 15,872 15,872 Total financial liabilities 20,714 — — 20,714 20,714 2016 Book value in Fair value Loans and (1) Debt At Fair value Financial assets Long-term financial assets 2,745 1,310 1,435 — 2,745 Customer accounts receivables and related receivables 1,250 — 1,250 — 1,250 Other current financial assets 516 — 516 — 516 Cash and cash equivalents 256,473 256,473 — — 256,473 Total financial assets 260,985 257,783 3,202 — 260,985 Financial liabilities Long-term conditional advances 4,049 — — 4,049 4,049 Long term financial rent debt — — — — — Other long-term liabilities 10,746 — — 10,746 10,746 Short-term conditional advances 578 — — 578 578 Short term financial rent debt 12 — — 12 12 Other short-term liabilities 14,692 — — 14,692 14,692 Account payable and other liabilities 13,720 — — 13,720 13,720 Total financial liabilities 43,798 — — 43,798 43,798 2017 Book value in Fair value Loans and (1) Debt At Fair value Financial assets Long-term financial assets 3,012 1,333 1,679 — 3,012 Customer accounts receivables and related receivables 1,265 — 1,265 — 1,265 Other current financial assets 378 — 378 — 378 Cash and cash equivalents 137,880 137,880 — — 137,880 Total financial assets 142,534 139,213 3,321 — 142,534 Financial liabilities Long-term conditional advances 1,825 — — 1,825 1,825 Long term financial rent debt — — — — — Other long-term liabilities 8,869 — — 8,869 8,869 Short-term conditional advances 2,325 — — 2,325 2,325 Short term financial rent debt — — — — — Other short-term liabilities 15,751 — — 15,751 15,751 Account payable and other liabilities 16,941 — — 16,941 16,941 Total financial liabilities 45,711 — — 45,711 45,711 (1) The fair value of “loans and receivables” corresponds to the value reported in the Consolidated Statements of Financial Position (value at the transaction date and then tested for impairment on each reporting date). (2) The book amount of financial liabilities measured at amortized cost was deemed to be a reasonable estimation of fair value. (3) The fair value of financial assets held for trading is determined based on Level 1 fair value measurements and corresponds to the market value of the assets.

Operating Income (Tables)

Operating Income (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Operating Income	The operating income is broken down in the following manner: December 31, 2015 2016 2017 (thousands of Euros) Revenues 202 — — Research tax credit 5,685 7,228 9,330 Subsidies 279 303 271 Other operating income — 1,554 2,308 Total 6,166 9,084 11,909

Operating Expenses (Tables)

Operating Expenses (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Research and Development Expense	The research and development expenses are broken down as follows: December 31, Research and development expenses 2015 2016 2017 (thousands of Euros) Personnel expenses 13,268 32,777 37,112 Sub-contracting, 15,325 34,413 54,397 Research supplies 911 1,234 1,464 Rental 1,094 1,903 2,018 Conferences, travel expenses 1,233 2,387 2,807 Depreciation and amortization 1,000 1,141 2,424 Small equipments and other supplies 795 2,675 2,646 Others 608 2,298 2,364 Total research and development expenses 34,234 78,828 105,232
Summary of Sales And Marketing Expense	The sales and marketing expenses are broken down as follows: December 31, Sales and marketing expenses 2015 2016 2017 (thousands of Euros) Personnel expenses 133 4,954 6,976 Fees 339 4,447 2,480 Marketing, tradeshows and travel expenses 20 1,393 5,984 Others — 487 384 Total sales and marketing expenses 491 11,282 15,824
Summary of General and Administrative Expense	By nature, the breakdown of general and administrative expenses is as follows: December 31, General and administrative expenses 2015 2016 2017 (thousands of Euros) Personnel expenses 8,768 22,613 19,742 Fees 4,234 7,701 10,347 Rental 305 501 584 Insurance policies 1,239 1,853 1,367 Corporate communication and travel expenses 1,010 1,136 1,599 Depreciation and amortization 74 181 422 Others 1,229 1,020 1,776 Total general and administrative expenses 16,859 35,005 35,837
Summary of Personnel Expense	The personnel expenses are broken down as follows: December 31, 2015 2016 2017 (thousands of Euros) Wages and salaries 7,243 14,651 22,451 Social security contributions 3,193 3,903 7,157 Expenses for pension commitments 116 982 1,583 Employer contribution to bonus shares 1,198 6,456 1,857 Share-based payments 10,419 34,353 30,781 Total 22,168 60,345 63,830

Share-Based Payments (Tables)

Share-Based Payments (Tables)	12 Months Ended
	Dec. 31, 2017
Summary Of Breakdown of the Closing Balance	Breakdown of the Closing Balance Year ended December 31, 2015 2016 2017 Number of BSA2010 Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable BSA2010 with exercise price of €77 1,044 1,044 610 610 500 500 Total 1,044 1,044 610 610 500 500
BSA [Member]
Summary Details of Share Based Payments	Details of BSA Date of grant (Board of 12/07/2007 12/07/2007 12/07/2007 12/07/2007 01/17/2012 01/17/2012 01/17/2012 01/17/2012 Vesting period (years) 1 2 3 4 1 2 3 4 Plan expiration date 12/08/2017 12/08/2017 12/08/2017 12/08/2017 01/17/2022 01/17/2022 01/17/2022 01/17/2022 Number of BSA granted 431 431 428 427 22,459 22,459 22,459 22,458 Share entitlement per BSA(1) 15 15 15 15 1 1 1 1 Exercise price (in euros) 65 65 65 65 5.13 5.13 5.13 5.13 Valuation method used Black - Scholes Grant date share fair value (in euros) 65 65 65 65 5.13 5.13 5.13 5.13 Expected volatility 40 % 40 % 40 % 40 % 40 % 40 % 40 % 40 % Average life of BSA (in years) 4.5 5.0 5.5 6.0 5.5 6.0 6.5 7.0 Discount rate(2) 4.06 % 4.09 % 4.09 % 4.10 % 2.33 % 2.33 % 2.61 % 2.61 % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA NA NA Fair value per BSA (in euros) 22.18 23.62 24.95 26.22 2.05 2.14 2.26 2.34 (1) The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BSA warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BSA plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans. (2) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BSA. Date of grant (Board of Directors) 09/25/2012 09/25/2012 09/25/2012 09/25/2012 07/25/2013 06/03/2014 Vesting period (years) 1 2 3 4 0 0 Plan expiration date 09/25/2022 09/25/2022 09/25/2022 09/25/2022 07/25/2023 06/03/2024 Number of BSA granted 7 500 7 500 7 500 7 500 73 000 10 000 Share entitlement per BSA 1 1 1 1 1 1 Exercise price (in euros) 8.59 8.59 8.59 8.59 8.1 18.79 Valuation method used Black - Scholes Grant date share fair value (in euros) 8.4 8.4 8.4 8.4 8.15 19.01 Expected volatility 40 % 40 % 40 % 40 % 40 % 40 % Average life of BSA (in years) 5.5 6.0 6.5 7.0 5.0 5.0 Discount rate(1) 1.21 % 1.21 % 1.53 % 1.53 % 1.16 % 0.71 % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA Fair value per BSA (in euros) 2.29 2.43 2.61 2.74 2.18 4.98 (1) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BSA. Date of grant (Board of Directors) 03/24/2015 11/19/2015 12/15/2015 06/21/2016 Vesting period (years) Plan expiration date 03/24/2025 11/19/2025 12/15/2015 06/21/2016 Number of BSA granted 10,000 15,000 90,000 (1) 20,000 Share entitlement per BSA 1 1 1 1 Exercise price (in euros) 43.00 66.06 64,14 52.97 Valuation method used Black - Scholes Grant date share fair value (in euros) 43 66.06 42.61 61.25 Expected volatility 36 % 50.91 % 51 % 47 % Average life of BSA (in years) 5.0 5.0 5.0 5.0 Discount rate(1) 0.68 % 0.81 % -0.09 % -0.41 % Expected dividends 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA Fair value per BSA (in euros) 9.90 22.60 7.28 21.59 Date of grant (Board of Directors) 12/09/2016 06/15/2017 Vesting period (years) 0 0 Plan expiration date 12/09/2026 06/15/2027 Number of BSA granted 59,000 9,000 Share entitlement per BSA 1 1 Exercise price (in euros) 69.75 59.05 Valuation method used Black - Scholes Grant date share fair value (in euros) 63.18 73.32 Expected volatility 40 % 39 % Average life of BSA (in years) 5.0 5.0 Discount rate(1) -0.04 % -0.12 % Expected dividends 0 % 0 % Performance conditions NA NA Fair value per BSA (in euros) 12.94 24.02 (1) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BSA.
Summary Of Change in Number of Outstanding shares	Change in Number of BSA Outstanding Year ended December 31, Number of BSA 2015 2016 2017 Balance at beginning of period 196,480 143,694 147,359 Granted during the period 25,000 93,500 68,000 Forfeited during the period — — 24,902 Exercised during the period 77,786 89,835 9,359 Expired during the period — — — Balance at end of period 143,694 147,359 181,008
Summary Breakdown of the Closing Balance	Breakdown of the Closing Balance Year ended December 31, 2015 2016 2017 Number of BSA Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable BSA2010 with exercise price of €65 859 859 859 859 — — BSA2010 with exercise price of €5.13 89,835 — — — — — BSA2010 with exercise price of €8.59 10,000 10,000 10,000 10,000 7,500 7,500 BSA2010 with exercise price of €8.10 13,000 13,000 13,000 13,000 9,500 9,500 BSA2010 with exercise price of €18.79 5,000 5,000 5,000 5,000 2,500 2,500 BSA with exercise price of €43.00 10,000 10,000 10,000 10,000 10,000 10,000 BSA with exercise price of €66.06 15,000 15,000 15,000 15,000 15,000 15,000 BSA with exercise price of €64.14 — — 73,500 73,500 73,500 73,500 BSA with exercise price of €52.97 — — 20,000 20,000 20,000 20,000 BSA with exercise price of €69.75 — — — — 34,008 34,008 BSA with exercise price of €59.05 — — — — 9,000 9,000 Total 143,694 53,859 147,359 147,359 181,008 181,008
BSA 2 [Member]
Summary Of Change in Number of Outstanding shares	Change in Number of BSA 2 Outstanding Year ended December 31 Number of BSA2 2015 2016 2017 Balance at beginning of period 8,049 — — Granted during the period — — — Forfeited during the period — — — Exercised during the period 8,049 — — Expired during the period — — — Balance at end of period — — —
BSA2010 [Member]
Summary Details of Share Based Payments	Details of BSA2010 Date of grant (Board of Directors) 01/28/2011 01/28/2011 01/28/2011 01/28/2011 06/24/2011 06/24/2011 06/24/2011 06/24/2011 Vesting period (years) 0.9 1.9 2.9 3.9 0.5 1.5 2.5 3.5 Plan expiration date 01/27/2021 01/27/2021 01/27/2021 01/27/2021 11/22/2021 11/22/2021 11/22/2021 11/22/2021 Number of BSA2010 granted 2,510 2,510 2,510 2,509 2,000 2,000 2,000 2,000 Share entitlement per BSA2010(1) 15 15 15 15 15 15 15 15 Exercise price (in euros) 77 77 77 77 77 77 77 77 Valuation method used Black - Scholes Black - Scholes Grant date share fair value (in euros) 77 77 77 77 77 77 77 77 Expected volatility 40 % 40 % 40 % 40 % 40 % 40 % 40 % 40 % Average life of BSA2010 (in years) 5.5 6.0 6.5 7.0 5.5 6.0 6.5 7.0 Discount rate(2) 2.70 % 2.82 % 2.82 % 3.04 % 2.55 % 2.68 % 2.68 % 2.87 % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA NA NA Fair value per BSA2010 (in euros) 31.33 32.90 34.23 35.84 31.15 32.70 34.02 35.57 (1) The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BSA2010 warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BSA2010 plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans. (2) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BSA2010. Date of grant (Board of Directors) 11/22/2011 11/22/2011 11/22/2011 11/22/2011 Vesting period (years) 1.0 2.0 3.0 4.0 Plan expiration date 11/22/2021 11/22/2021 11/22/2021 11/22/2021 Number of BSA2010 granted 335 335 334 334 Share entitlement per BSA(1) 15 15 15 15 Exercise price (in euros) 77 77 77 77 Valuation method used Black - Scholes Grant date share fair value (in euros) 77 77 77 77 Expected volatility 40 % 40 % 40 % 40 % Average life of BSA (in years) 5.5 6.0 6.5 7.0 Discount rate(2) 2.23 % 2.60 % 2.60 % 2.85 % Expected dividends 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA Fair value per BSA (in euros) 30.70 32.58 33.89 35.54 (1) The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BSA2010 warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BSA2010 plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans. (2) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BSA2010.
Summary Breakdown of the Closing Balance	Breakdown of the Closing Balance Year ended December 31, 2015 2016 2017 Number of BSA2 Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable BSA2 with exercise price of €65 — — — — — — Total — — — — — —
Summary Of Breakdown of the Closing Balance	Change in Number of BSA2010 Outstanding Year ended December 31, Number of BSA 2015 2016 2017 Balance at beginning of period 8,334 1,044 610 Granted during the period — — — Forfeited during the period — — — Exercised during the period 7,290 434 110 Expired during the period — — — Balance at end of period 1,044 610 500
BCE 4 [Member]
Summary Details of Share Based Payments	Details of BCE4 Date of grant (Board of Directors) 01/21/2009 01/21/2009 01/21/2009 01/21/2009 01/21/2009 Vesting period (years) 0 1 2 3 4 Plan expiration date 01/20/2019 01/20/2019 01/20/2019 01/20/2019 01/20/2019 Number of BCE4 granted 2,411 1,340 536 536 535 Share entitlement per BCE4(1) 15 15 15 15 15 Exercise price (in euros) 65 65 65 65 65 Valuation method used Black - Scholes Grant date share fair value (in euros) 70 70 70 70 70 Expected volatility 40 % 40 % 40 % 40 % 40 % Average life of BCE4 (in years) 5.0 5.5 6.0 6.5 7.0 Discount rate(2) 2.71 % 2.71 % 2.98 % 2.98 % 3.11 % Expected dividends 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA Fair value per BCE4 (in euros) 29.06 30.33 31.90 33.06 34.35 (1) The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BCE4 warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BCE4 plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans. (2) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BCE4.
Summary Of Change in Number of BCE4 Outstanding	Change in Number of BCE4 Outstanding Year ended December 31, Number of BCE4 2015 2015 2016 Balance at beginning of period 5,358 2,691 2,691 Granted during the period — — — Forfeited during the period — — — Exercised during the period 2,667 — 2,691 Expired during the period — — — Balance at end of period 2,691 2,691 —
Summary of Number of Share Options Oustanding and Exercisable	Breakdown of the Closing Balance Year ended December 31, 2015 2016 2017 Number of BCE4 Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable BCE4 with exercise price of €65 2,691 2,691 2,691 2,691 — — Total 2,691 2,691 2,691 2,691 — —
BCE2010 [Member]
Summary Details of Share Based Payments	Details of BCE2010 Date of grant (Board of Directors) 06/24/2011 06/24/2011 06/24/2011 06/24/2011 11/22/2011 11/22/2011 11/22/2011 11/22/2011 Vesting period (years) 0.5 1.5 2.5 3.5 1 2 3 4 Plan expiration date 11/22/2021 11/22/2021 11/22/2021 11/22/2021 11/22/2021 11/22/2021 11/22/2021 11/22/2021 Number of BCE2010 granted 6,000 6,000 6,000 6,000 2,510 2,510 2,510 2,509 Share entitlement per BCE2010(1) 15 15 15 15 15 15 15 15 Exercise price (in euros) 77 77 77 77 77 77 77 77 Valuation method used Black and Scholes Grant date share fair value (in euros) 77 77 77 77 77 77 77 77 Expected volatility 40 % 40 % 40 % 40 % 40 % 40 % 40 % 40 % Average life of BCE2010 (in years) 5.5 6.0 6.5 7.0 5.4 5.9 6.4 6.9 Discount rate(2) 2.55 % 2.68 % 2.68 % 2.87 % 2.05 % 2.42 % 2.42 % 2.66 % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA NA NA Fair value per BCE2010 (in euros) 31.16 32.71 34.03 35.58 30.42 32.29 33.58 35.2 (1) The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BCE2010 warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BCE2010 plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans. (2) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BCE2010.
Summary Of Change in Number of Outstanding shares	Change in Number of BCE2010 Outstanding Year ended December 31, Number of BCE2010 2015 2016 2017 Balance at beginning of period 29,972 15,974 12,339 Granted during the period — — — Forfeited during the period — — — Exercised during the period 13,998 3,635 1,334 Expired during the period — — — Balance at end of period 15,974 12,339 11,005
Summary Breakdown of the Closing Balance	Breakdown of the Closing Balance Year ended December 31, 2015 2016 2017 Number of BCE2010 Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable BCE2010 with exercise price of €77.00 15,974 15,974 12,339 12,339 11,005 11,005 Total 15,974 15,974 12,339 12,339 11,005 11,005
Share Option [Member]
Summary Details of Share Based Payments	Details of SO Date of grant (Board of Directors) 09/18/2013 06/03/2014 06/23/2015 11/19/2015 01/04/2016 04/21/2016 05/02/2016 Vesting period (years) 4 2 1-4 1-4 1-4 1-4 1-4 Plan expiration date 09/18/2023 06/03/2024 06/23/2025 11/19/2025 01/04/2026 04/21/2026 05/02/2026 Number of SO granted 518,000 75,000 120,000 195,000 75,000 33,000 22,000 Share entitlement per SO 1 1 1 1 1 1 1 Exercise price (in euros) 7.57 19.01 48.9 66.06 65.68 62.82 59.04 Valuation method used Black - Scholes Grant date share fair value (in euros) 7.9 19.01 48.9 66.06 65.68 62.82 58.62 Expected volatility 40 % 40 % 51 % 51 % 49.3%-49.8 % 49.4%-50.7 % 49.3%-50.6 % Average life of SO (in years) 7 6 7 7 5-7 5-7 5-7 Discount rate(1) 1.72 % 0.89 % 0.89 % 0.81 % 0.39 % 0.04 % 0.10 % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA NA Fair value per SO (in euros) 3.57 7.46 25.28 34.05 29.5-32.6 28.3 – 30.9 26.4-28.8 (1) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of SO. Date of grant 06/21/2016 08/01/2016 09/15/2016 10/17/2016 11/15/2016 12/09/2016 12/15/2016 Vesting period (years) 1-4 1-4 1-4 1-4 1-4 1-4 1-4 Plan expiration date 06/21/2026 08/01/2026 09/15/2016 10/17/2026 11/15/2026 12/09/2026 12/15/2026 Number of SO granted 110,000 10,000 9,300 16,500 8,300 74,960 1,100 Share entitlement per SO 1 1 1 1 1 1 1 Exercise price (in euros) 53.96 62.24 62.8 64.39 68.33 69.75 69.35 Valuation method used Black - Scholes Grant date share fair value (in euros) 52.97 62.24 62.8 64.39 68.33 69.75 69.35 Expected volatility 49.1%-50.3 % 48.8%-49.8 % 48.6%-49.4 % 48.0%-48.9 % 47.8%-48.8 % 47.7%-48.5 % 40.44 % Average life of SO (in years) 5-7 5-7 5-7 5-7 5-7 5-7 5-7 Discount rate(1) -0.01 % -0.25 % -0.18 % -0.32 -0.15 % % -0.11 +0.16 % % -0.2 +0.18 % % -0.18 +0.16 % % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA NA Fair value per SO (in euros) 23.4-25.5 27.3-29.9 27.4-30.1 27.6-30.6 29.4-32.7 29.7-33.4 25.2-28.7 1) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of SO. Date of grant 01/16/2017 03/15/2017 04/18/2017 06/15/2017 06/15/2017 07/17/2017 09/15/2017 Vesting period (years) 1-4 1-4 1-4 1-4 1-4 1-4 1-4 Plan expiration date 01/16/2027 03/15/2027 04/18/2027 06/15/2027 06/15/2027 07/17/2027 09/15/2027 Number of SO granted 19,100 7,200 16,500 126,000 111.600 30,900 52,600 Share entitlement per SO 1 1 1 1 1 1 1 Exercise price (in euros) 66.11 66.25 60.77 59.05 60.54 71.61 74.22 Valuation method used Black - Scholes Grant date share fair value (in euros) 66.11 65.42 59.73 59.05 59.05 71.61 71.80 Expected volatility 40.21 % 39.82 % 39.63 % 39.23 % 39.23 % 38.84 % 38.57 % Average life of SO (in years) 5-7 5-7 5-7 5-7 5-7 5-7 5-7 Discount rate(1) -0.17 +0.19 % % +0.21 +0.61 % % +0.02 +0.39 % % -0.21 +0.07 % % -0.21 +0.07 % % +0.01 +0.34 % % -0.14 +0.19 % % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA NA Fair value per SO (in euros) 23.9-27.2 23.6-27.1 21.2-24.2 20.8 – 23.6 20.4-23.22 25.3 – 28.2 24.3 – 27.8 (1) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of SO. Date of grant 12/05/2017 12/15/2017 Vesting period (years) 1-4 1-4 Plan expiration date 12/05/2027 12/15/2027 Number of SO granted 625,200 8,300 Share entitlement per SO 1 1 Exercise price (in euros) 39.00 38.18 Valuation method used Black - Scholes Grant date share fair value (in euros) 35.73 36.43 Expected volatility 43.23 % 43.13 % Average life of SO (in years) 5-7 5-7 Discount rate(1) -0.23 +0.07 % % -0.23 +0.07 % % Expected dividends 0 % 0 % Performance conditions NA NA Fair value per SO (in euros) 12.9 – 14.7 13.5 – 15.4 (1) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of SO.
Disclosure of Change in Number of Share Options Outstanding	Change in Number of SO Outstanding December 31, Number of SO 2015 2016 2017 Balance at beginning of period 546,000 861,000 1,160,060 Granted during the period 315,000 359,060 998,500 Forfeited during the period — 25,000 24,260 Exercised during the period — 35,000 1,200 Expired during the period — — — Balance at end of period 861,000 1,160,060 2,133,100
SO [Member]
Summary Of Change in Number of Outstanding shares	Breakdown of the Closing Balance Year ended December 31, 2015 2016 2017 Number of SO Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable SO with exercise price of €7.57 471,000 — 471,000 — 471,000 471,000 SO with exercise price of €19.01 75,000 — 40,000 40,000 40,000 40,000 SO with exercise price of €48.90 120,000 — 120,000 45,000 120,000 75,000 SO with exercise price of €66.06 195,000 — 170,000 — 170,000 85,000 SO with exercise price of €65.68 — — 75,000 — 75,000 18,750 SO with exercise price of €62.82 — — 33,000 — 33,000 8,250 SO with exercise price of €59.04 — — 22,000 — 22,000 5,500 SO with exercise price of €53.96 — — 110,000 — 101,300 24,425 SO with exercise price of €62.24 — — 10,000 — 10,000 2,500 SO with exercise price of €62.80 — — 9,300 — 9,300 2,325 SO with exercise price of €64.39 — — 16,500 — 9,300 2,325 SO with exercise price of €68.33 — — 8,300 — 8,300 2,075 SO with exercise price of €69.75 — — 74,960 — 72,900 18,225 SO with exercise price of €66.35 — — — — 1,100 275 SO with exercise price of €66.11 — — — — 19,100 — SO with exercise price of €66.25 — — — — 7,200 — SO with exercise price of €60.77 — — — — 16,500 — SO with exercise price of €59.05 — — — — 118,500 — SO with exercise price of €60.54 — — — — 111,600 — SO with exercise price of €71.61 — — — — 30,900 — SO with exercise price of €74.22 — — — — 52,600 — SO with exercise price of €39.00 — — — — 625,200 — SO with exercise price of €38.18 — — — — 8,300 — Total 861,000 — 1,160,000 85,000 2,133,100 755,650
Free Share [Member]
Summary Details of Share Based Payments	Details of Free Shares Date of grant (Board of Directors) 04/02/2012 07/25/2012 11/28/2012 07/25/2013&09/12/2013 06/03/2014 Vesting period (years) 2 2 2 2 2 Number of free shares granted 669,796 134,081 35,360 501,500 186,000 Share entitlement per free share (1) 1 1 1 1 1 Grant date share fair value (in euros) 8.86 8.20 8.70 7.96 19.01 Expected dividends 0 % 0 % 0 % 0 % 0 % Performance conditions Yes (1) Yes (1) No Yes (2) Yes (3) Expected turnover during the vesting period 1 % 1 % 1 % 1 % 1 % Date of grant (Board of Directors) 09/30/2015 12/15/2015 Vesting period (years) 2 2 Number of free shares granted 708,500 42,000 Share entitlement per free share (1) 1 1 Grant date share fair value (in euros) 62.99 64.14 Expected dividends 0% 0% Performance conditions Yes (4) Yes (4) Expected turnover during the vesting period 0% 0% (1) The acquisition of free shares is contingent for certain individuals (the “Key Managers”), including Dr. Benhamou, upon the achievement of the three performance criteria below: • One-third th • One-third • One-third (2) The acquisition of free shares is contingent for the Key Managers, including Dr. Benhamou, upon the achievement of the three performance criteria below: • One-third th • One-third • One-third It is specified that in the event of a change of control of the Company (as defined in Article L. 233-3 (3) The acquisition of free shares is contingent for the Key Managers, including Dr. Benhamou, upon the achievement of the two performance criteria below: • Half of the shares allocated to Key Managers will only be acquired from the later of the two following dates (i) expiry of a period of two years from the date of allocation and (ii) inclusion of the 100 th • Half of the shares allocated to Key Managers will only be acquired from the later of the two following dates (i) expiry of a period of two years from the date of allocation and (ii) approval by the FDA of a protocol for the Phase III trial of Viaskin Peanut. (4) The acquisition of free shares is contingent for all the employees, including Dr. Benhamou, upon the achievement of the three performance criteria below: • One third of the shares will only be acquired from the later of the following two dates : (i) the end of the 2 year vesting period which runs from September 30, 2015 and (ii) achievement of the primary efficacy endpoint of the Phase III ‘Pepites’ trial for Viaskin Peanut; on December 13, 2017, the Board determined that the results from the PEPITES trial did not mean that the performance criteria was not reached and has precised this condition. • One third of the shares will only be acquired from the later of the following two dates : (i) the end of the 2 year vesting period which runs from September 30, 2015 and (ii) achievement of the primary efficacy endpoint of the Phase II ‘Miles’ trial for Viaskin Milk; • One third of the shares will only be acquired from until the later of the following two dates: (i) the end of the 2 year vesting period which runs from September 30, 2015 and (ii) the beginning of clinical testing of another product candidate from the Viaskin platform. Board of Directors Grant date 04/06/2016 06/21/2016 08/16/2016 09/01/2016 10/27/2016 12/09/2016 Vesting period (years) 2 2 2 2 2 2 Number of free shares granted 63,750 193,000 10,000 5,000 15,000 23,600 Share entitlement per free share 1 1 1 1 1 1 Grant date share fair value (in euros) 62.40 52.97 60.68 61.49 67.44 69.75 Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions yes (1) yes (1) yes (1) yes (1) yes (2) yes (2) Expected turnover during the vesting period 0 % 0 % 0 % 0 % 0 % 0 % (1) The acquisition of free shares is contingent for all the employees, including Dr. Benhamou, upon the achievement of the three performance criteria below: • One third of the shares will only be acquired from the later of the following two dates: (i) the end of the 2 year vesting period which runs from Grant Date and (ii) achievement of the primary efficacy endpoint of the Phase III ‘Pepites’ trial for Viaskin Peanut; on December 13, 2017, the Board determined that the results from the PEPITES trial did not mean that the performance criteria was not reached and has precised this condition. • One third of the shares will only be acquired from the later of the following two dates: (i) the end of the 2 year vesting period which runs from Grant Date and (ii) achievement of the primary efficacy endpoint of the Phase II ‘Miles’ trial for Viaskin Milk; • One third of the shares will only be acquired from until the later of the following two dates: (i) the end of the 2 year vesting period which runs from Grant date and (ii) the beginning of clinical testing of another product candidate from the Viaskin platform. (2) The acquisition of free shares is contingent for key and new employees upon the achievement of the two performance criteria below: • Half of the shares will only be acquired from the later of the following two dates: (i) the end of the 2 year vesting period which runs from Grant Date and (ii) achievement of the primary efficacy endpoint of the Phase III ‘Pepites’ trial for Viaskin Peanut; on December 13, 2017, the Board determined that the results from the PEPITES trial did not mean that the performance criteria was not reached and has precised this condition. • Half of the shares will only be acquired from the later of the following two dates: (i) the end of the 2 year vesting period which runs from Grant Date and (ii) achievement of the primary efficacy endpoint of the Phase II ‘Miles’ trial for Viaskin Milk. Performance conditions other than market conditions, which are taken into account by adjusting the number of equity instruments included in the measurement of the transaction amount, but are not taken into account when estimating the fair value of the shares. Board of Directors Grant date 03/14/2017 04/20/2017 Vesting period (years) 2 2 Number of free shares granted 22,500 24,000 Share entitlement per free share 1 1 Grant date share fair value (in euros) 68.07 61.20 Expected dividends 0 % 0 % Performance conditions yes (1) yes (1) Expected turnover during the vesting period 0 % 0 % (1) The acquisition of free shares is contingent for key and new employees upon the achievement of the two performance criteria below: • Half of the Shares allocated will not be acquired until the later of the following two dates: (i) the end of the two (2)-year acquisition period which runs from today and (ii) submission of the application for market authorization from the FDA for Viaskin Peanut. • Half of the Shares allocated will not be acquired until the later of the following two dates: (i) the end of the two (2)-year acquisition period which runs from today and (ii) the first date of sale of Viaskin Peanut in the United States.
Summary Of Change in Number of BCE4 Outstanding	Change in Number of Free Shares Outstanding Year ended December 31, Number of Free shares 2015 2016 2017 Balance at beginning of period 641,360 1,008,329 1,036,850 Granted during the period 750,500 310,350 46,500 Forfeited during the period 61,833 24,000 18,650 Exercised during the period 321,698 257,829 241,844 Expired during the period — — — Balance at end of period 1,008,329 1,036,850 822,856
Board of Director [Member]
Summary Of Change in Number of Outstanding shares	By a decision by the Board of Directors meeting held on November 22, 2011, the BSA2 warrants became exercisable beginning on the date of the first quotation of the shares of the Company on the Euronext regulated market in Paris. Details of BSA2 Date of grant (Board of Directors) 01/21/2009 01/21/2009 01/21/2009 01/21/2009 01/21/2009 Vesting period (years) 0 1 2 3 4 Plan expiration date 01/20/2019 01/20/2019 01/20/2019 01/20/2019 01/20/2019 Number of BSA2 granted 4,822 2,680 1,072 1,072 1,070 Share entitlement per BSA2(1) 15 15 15 15 15 Exercise price (in euros) 65 65 65 65 65 Valuation method used Black - Scholes Grant date share fair value (in euros) 70 70 70 70 70 Expected volatility 40 % 40 % 40 % 40 % 40 % Average life of BSA2 (in years) 5.0 5.5 6.0 6.5 7.0 Discount rate(2) 2.71 % 2.71 % 2.98 % 2.98 % 3.11 % Expected dividends 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA Fair value per BSA2 (in euros) 29.05 30.32 31.89 33.05 33.45 (1) The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BSA2 warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BSA2 plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans. (2) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BSA2.
BSAX [Member]
Summary Details of Share Based Payments	Details of BSAX Date of grant (Board of Directors) 01/21/2009 01/21/2009 01/21/2009 01/21/2009 06/25/2010 06/25/2010 06/25/2010 06/25/2010 Vesting period (years) 1 2 3 4 1 2 3 4 Plan expiration date 01/20/2019 01/20/2019 01/20/2019 01/20/2019 06/24/2020 06/24/2020 06/24/2020 06/24/2020 Number of BSAX granted 77 77 77 75 457 457 456 455 Share entitlement per BSAX(1) 15 15 15 15 15 15 15 15 Exercise price (in euros) 65 65 65 65 65 65 65 65 Valuation method used Black - Scholes Grant date share fair value (in euros) 70 70 70 70 70 70 70 70 Expected volatility 40 % 40 % 40 % 40 % 40 % 40 % 40 % 40 % Average life of BSAX (in years) 5.5 6.0 6.5 7.0 5.5 6.0 6.5 7.0 Discount rate(2) 2.71 % 2.98 % 2.98 % 3.11 % 2.04 % 2.23 % 2.23 % 2.50 % Expected dividends 0 % 0 % 0 % 0 % 0 % 0 % 0 % 0 % Performance conditions NA NA NA NA NA NA NA NA Fair value per BSAX (in euros) 30.32 31.89 33.05 33.45 29.47 30.88 31.99 33.44 (1) The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BSAX warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BSAX plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans. (2) Based on French government bonds (GFRN) with a maturity corresponding to the maturity of BSAX.
Summary Of Change in Number of Outstanding shares	Change in Number of BSAX Outstanding Year ended December 31, Number of BSAX 2015 2016 2017 Balance at beginning of period 2,131 1,036 1,036 Granted during the period — — — Forfeited during the period — — — Exercised during the period 1,095 — 1,036 Expired during the period — — — Balance at end of period 1,036 1,036 —
Summary Of Breakdown of the Closing Balance	Breakdown of the Closing Balance Year ended December 31, 2014 2015 2016 Number of BSAX Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable BSAX with exercise price of €65 1,036 1,036 1,036 1,036 — — Total 1,036 1,036 1,036 1,036 — —

Financial Revenue and Expenses

Financial Revenue and Expenses (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Financial Income and Expenses	The financial income and expenses are broken down as follows: Year ended December 31, 2015 2016 2017 (thousands of Euros) Financial revenues 1,018 1,646 616 Financial expenses (146 ) (145 ) (3,325 ) Total 871 1,500 (2,709 )

Income Tax Expense (Tables)

Income Tax Expense (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Reconciliation of Effective and Nominal Tax Expense	The following table shows the reconciliation between the effective and nominal tax expense at the nominal standard French rate of 33.33% (excluding additional contributions): Year ended December 31, 2015 2016 2017 (thousands of Euros) (Loss) before taxes (44,674 ) (114,531 ) (147,692 ) Theoretical group tax rate 33.33 % 33.33 % 33.33 % Nominal tax expense 14,890 38,173 49,226 Increase/decrease in tax expense arising from: Permanent differences (1) 6,089 — — Research tax credit 1,895 2,409 3,110 Share-based compensation (3,473 ) (11,451 ) (10,260 ) Non recognition of deferred tax assets related to tax losses and temporary differences (19,211 ) (29,195 ) (41,453 ) Other differences 190 64 622 Effective tax expense — — — Effective tax rate 0 % 0 % 0 % (1) The significant balance of permanent differences is mainly affected by transaction costs on capital increase occurred in 2015. These transaction costs are booked in equity and are subject to a tax deduction.

Commitments (Tables)

Commitments (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Schedule of Future Rents and Charges	The amount of future rents and charges in that capacity breaks down as follows at December 31, 2017: 12/31/2017 2018 2,617 2019 2,623 2020 2,357 2021 2,169 2022 2,119 2023 1,847 2024 1,258 2025 — Total 14,991

Relationships with Related Pa50

Relationships with Related Parties (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Relationships with Related Parties	December 31, 2015 2016 2017 (thousands of Euros) Members of the Board of Directors 605 714 745 Executive committee 1,768 2,268 2,184 Directors’ fees 195 195 407 Share-based payments to members of the Board of Directors 4,637 13,714 12,018 Total 7,205 16,891 15,353
Schedule of Amounts Payable to Related Parties	A schedule of amounts payable to related parties as of December 31, 2017: December 31, 2015 2016 2017 (thousands of Euros) Compensation 674 767 689 Directors’ fees 195 195 432 Pension obligations 233 342 402 Total 1,102 1,304 1,523

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Earnings Per Share	December 31, 2015 2016 2017 (thousands of Euros) Net income of the reporting period (44,674 ) (114,531 ) (147,693 ) Adjusted weighted average number of outstanding shares 21,522,342 24,454,850 24,757,176 Basic / Diluted earnings per share (€/share) (2.08 ) (4.68 ) (5.97 )

The Company - Additional Inform

The Company - Additional Information (Detail)	Jun. 21, 2016Director	Sep. 30, 2016Patient	Dec. 31, 2017
Disclosure Of Company [Line items]
Number of directors after additions | Director	8
Viaskin Peanut [member] | Bottom of range [member]
Disclosure Of Company [Line items]
Age of patients evaluated			4 years
Viaskin Peanut [member] | Top of range [member]
Disclosure Of Company [Line items]
Age of patients evaluated			11 years
Viaskin Milk [member]
Disclosure Of Company [Line items]
Number of patients evaluated | Patient		198
Viaskin Milk [member] | Bottom of range [member]
Disclosure Of Company [Line items]
Age of patients evaluated		2 years
Viaskin Milk [member] | Top of range [member]
Disclosure Of Company [Line items]
Age of patients evaluated		17 years

General Information and State53

General Information and Statement of Compliance - Additional Information (Detail)	Apr. 07, 2015
US subsidiary [member]
Disclosure of subsidiaries [line items]
Proportion of ownership interest in subsidiary	100.00%

Accounting Principles - Additio

Accounting Principles - Additional Information (Detail) - EUR (€)	1 Months Ended	12 Months Ended
	Jul. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2018
Disclosure of summary of significant accounting policies [line Items]
Research tax credit reimbursement		€ 7,300,000	€ 5,700,000	€ 4,300,000
Tax credit reimbursement to be requested					€ 9,200,000
Potential development, clinical, commercial milestones payment receivable	€ 100,000,000
Non-refundable upfront payment	€ 10,000,000
Deferred revenue		€ 9,500,000
Bottom of range [member] | Software [member]
Disclosure of summary of significant accounting policies [line Items]
Depreciation periods		1 year
Top of range [member] | Software [member]
Disclosure of summary of significant accounting policies [line Items]
Depreciation periods		3 years

Accounting Principles - Summary

Accounting Principles - Summary of Depreciation Periods (Detail)	12 Months Ended
	Dec. 31, 2017
Fixtures and improvements in structures [member]
Disclosure of detailed information about property, plant and equipment [line items]
Depreciation periods	9 years
Research and development / production tools [member]
Disclosure of detailed information about property, plant and equipment [line items]
Depreciation periods	5 years
Research equipment and technical facilities [member]
Disclosure of detailed information about property, plant and equipment [line items]
Depreciation periods	5 years
Computer equipment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Depreciation periods	3 years
Office equipment and furniture [member]
Disclosure of detailed information about property, plant and equipment [line items]
Depreciation periods	5 years

Intangible Assets - Summary of

Intangible Assets - Summary of Intangible Assets (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of detailed information about intangible assets [line items]
Intangible assets other than goodwill	€ 123	€ 96	€ 94
Total, gross [member]
Disclosure of detailed information about intangible assets [line items]
Intangible assets other than goodwill	864	572	356
Total accumulated amortization and depreciation [member]
Disclosure of detailed information about intangible assets [line items]
Intangible assets other than goodwill	741	476	262
Patents, licenses, trademarks [member] | Total, gross [member]
Disclosure of detailed information about intangible assets [line items]
Intangible assets other than goodwill	414	196	54
Patents, licenses, trademarks [member] | Total accumulated amortization and depreciation [member]
Disclosure of detailed information about intangible assets [line items]
Intangible assets other than goodwill	340	125	53
Software [member] | Total, gross [member]
Disclosure of detailed information about intangible assets [line items]
Intangible assets other than goodwill	450	376	302
Software [member] | Total accumulated amortization and depreciation [member]
Disclosure of detailed information about intangible assets [line items]
Intangible assets other than goodwill	€ 401	€ 351	€ 210

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017EUR (€)
Disclosure of detailed information about intangible assets [abstract]
increase in value of intangible assets corresponds to Acquisition	€ 292,000
Impairment of assets	€ 0

Property, Plant, and Equipmen58

Property, Plant, and Equipment - Summary of Property, Plant, and Equipment (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant, and equipment beginning balance	€ 12,482	€ 5,581	€ 2,225
Increase in property, plant, and equipment	5,443	6,901	3,375
Decrease in property, plant, and equipment	(118)		18
Property, plant, and equipment ending balance	17,808	12,482	5,581
Total, gross [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant, and equipment beginning balance	15,685	7,646	3,775
Increase in property, plant, and equipment	7,114	8,039	4,365
Decrease in property, plant, and equipment	(329)		(493)
Property, plant, and equipment ending balance	22,470	15,685	7,646
Total, gross [member] | Laboratory equipment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant, and equipment beginning balance	3,097	2,357	2,257
Increase in property, plant, and equipment	2,806	740	467
Decrease in property, plant, and equipment	(83)		(368)
Property, plant, and equipment ending balance	5,820	3,097	2,357
Total, gross [member] | Building fixtures [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant, and equipment beginning balance	4,610	938	930
Increase in property, plant, and equipment	534	3,672	8
Decrease in property, plant, and equipment	(46)
Property, plant, and equipment ending balance	5,098	4,610	938
Total, gross [member] | Office equipment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant, and equipment beginning balance	607	209	215
Increase in property, plant, and equipment	275	398	24
Decrease in property, plant, and equipment	(116)		(30)
Property, plant, and equipment ending balance	766	607	209
Total, gross [member] | Computer equipment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant, and equipment beginning balance	986	470	322
Increase in property, plant, and equipment	116	516	244
Decrease in property, plant, and equipment	(30)		(95)
Property, plant, and equipment ending balance	1,073	986	470
Total, gross [member] | Property, plant, and equipment in progress [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant, and equipment beginning balance	6,385	3,672	51
Increase in property, plant, and equipment	3,384	2,713	3,622
Decrease in property, plant, and equipment	(55)
Property, plant, and equipment ending balance	9,714	6,385	3,672
Total accumulated amortization and depreciation [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant, and equipment beginning balance	3,202	2,065	1,550
Increase in property, plant, and equipment	1,671	1,137	990
Decrease in property, plant, and equipment	(211)		(475)
Property, plant, and equipment ending balance	4,663	3,202	2,065
Total accumulated amortization and depreciation [member] | Scenario, Previously Reported [Member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant, and equipment beginning balance	3,203
Property, plant, and equipment ending balance		3,203
Total accumulated amortization and depreciation [member] | Laboratory equipment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant, and equipment beginning balance	1,505	948	916
Increase in property, plant, and equipment	802	557	382
Decrease in property, plant, and equipment	(63)		(349)
Property, plant, and equipment ending balance	2,244	1,505	948
Total accumulated amortization and depreciation [member] | Building fixtures [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant, and equipment beginning balance	1,109	782	286
Increase in property, plant, and equipment	484	327	496
Decrease in property, plant, and equipment	(14)
Property, plant, and equipment ending balance	1,580	1,109	782
Total accumulated amortization and depreciation [member] | Office equipment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant, and equipment beginning balance	212	131	126
Increase in property, plant, and equipment	213	81	35
Decrease in property, plant, and equipment	(105)		(30)
Property, plant, and equipment ending balance	320	212	131
Total accumulated amortization and depreciation [member] | Computer equipment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant, and equipment beginning balance	377	205	222
Increase in property, plant, and equipment	172	172	78
Decrease in property, plant, and equipment	(30)		(95)
Property, plant, and equipment ending balance	€ 520	€ 377	€ 205

Non-Current Financial Assets -

Non-Current Financial Assets - Summary of Non-Current Financial Assets (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of non financial assets.
Non-current financial assets	€ 3,012	€ 2,745	€ 2,711
Deposits [member]
Disclosure of non financial assets.
Non-current financial assets	577	824	716
Pledged securities [member]
Disclosure of non financial assets.
Non-current financial assets	1,102	611	611
Liquidity contract [member]
Disclosure of non financial assets.
Non-current financial assets	€ 1,333	€ 1,310	€ 1,384

Non-Current Financial Assets 60

Non-Current Financial Assets - Additional Information (Detail)	Dec. 31, 2017shares
Disclosure of non financial assets.
Number of shares outstanding	24,990,822
Liquidity contract [member]
Disclosure of non financial assets.
Number of treasury shares	4,939

Inventories and Work in Progr61

Inventories and Work in Progress - Summary of Inventories (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of inventories [abstract]
Inventories of raw materials		€ 69	€ 69
Depreciation of inventories		(69)	(69)
Total net value of the inventories	€ 0	€ 0	€ 0

Customer Accounts Receivable 62

Customer Accounts Receivable and Other Current Assets - Summary of Customer Accounts Receivable and Related Receivables (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Trade and other receivables [abstract]
Accounts receivable	€ 1,265	€ 1,263	€ 13
Valuation allowance		(13)	€ (13)
Total net value of accounts receivable	€ 1,265	€ 1,250

Customer Accounts Receivable 63

Customer Accounts Receivable and Other Current Assets - Additional Information (Detail) - EUR (€) € in Thousands	Jul. 04, 2016	Dec. 31, 2017	Dec. 31, 2015
Trade and other receivables [abstract]
Trade receivables payment terms		Less than one year
Research tax credit current adjustment	€ 900	€ 113	€ (18)

Customer Accounts Receivable 64

Customer Accounts Receivable and Other Current Assets - Summary of Other Current Assets (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of accounts receivables [abstract]
Research tax credit	€ 9,217	€ 7,228	€ 5,702	€ 4,340
Other tax claims	5,258	2,618	2,550
Other receivables	1,192	1,883	1,409
Prepaid expenses	2,054	2,725	1,850
Total	€ 17,721	€ 14,454	€ 11,512

Customer Accounts Receivable 65

Customer Accounts Receivable and Other Current Assets - Reconciliation of Research Tax Credit (Detail) - EUR (€) € in Thousands	Jul. 04, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Trade and other receivables [abstract]
Opening balance sheet receivable		€ 7,228	€ 5,702	€ 4,340
+ Other income		9,217	7,228	5,702
- Payment received		(7,341)	(5,702)	(4,322)
- Adjustment	€ 900	113		(18)
Closing balance sheet receivable		€ 9,217	€ 7,228	€ 5,702

Cash and Cash Equivalents - Sum

Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash and cash equivalents [abstract]
Cash	€ 32,054	€ 146,374	€ 178,895
Cash equivalent term deposits	105,826	110,100	144,486
Total cash and cash equivalent as reported in statement of financial position	137,880	256,473	323,381	€ 114,555
Bank overdrafts	0	0	0
Total net cash and cash equivalents as reported in the statement of cash flow	€ 137,880	€ 256,473	€ 323,381	€ 114,555

Capital - Additional Informatio

Capital - Additional Information (Detail)	Jul. 20, 2015€ / sharesshares	Oct. 22, 2014€ / shares$ / sharesshares	Dec. 09, 2011	Jul. 31, 2015EUR (€)shares	Oct. 31, 2014EUR (€)shares	Dec. 31, 2016EUR (€)shares	Dec. 31, 2015EUR (€)shares	Dec. 31, 2017EUR (€)€ / sharesshares	Dec. 31, 2014shares
Disclosure of classes of share capital [line items]
Share Capital | €						€ 2,465,000	€ 2,421,000	€ 2,499,082.20
Number of share authorised								24,990,822
Number of share issued								24,990,822
Par value per share | € / shares								€ 0.10
Fees and commission expense related to share capital | €						€ 0	€ 18,300,000
Number of shares issued during period shares						2,606,435	2,336,224	3,309,539
Number of additional american depository shares issued	1,080,000
Description of american depository shares	Each ADS represents the right to receive one-half of one ordinary share.
Number of ordinary shares per american depository shares | € / shares	€ 0.5
Share split ratio			0.0667
Common Shares [member]
Disclosure of classes of share capital [line items]
Number of share issued						24,648,828	24,205,129	24,990,822	19,160,661
Initial Public Offering [Member]
Disclosure of classes of share capital [line items]
Increase in share capital during period shares				4,140,000	3,074,686
Increase in share capital through issuance of shares | €				€ 414,000	€ (307,468)
Increase in share capital through issuance of shares gross | €				254,900,000	104,231,855
Increase in share capital through issuance of shares net | €				236,900,000	93,403,561
Fees and expenses related to share capital | €				18,000,000	10,828,294.23
Number of common shares issued		2,673,641
Initial Public Offering [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Increase in share capital through issuance of shares | €				€ 236,900,000	€ 93,403,561
Initial Public Offering [Member] | Common Shares [member]
Disclosure of classes of share capital [line items]
Number of shares issued during period shares	4,140,000	2,138,913
Initial Public Offering [Member] | American Depositary Shares [Member]
Disclosure of classes of share capital [line items]
Par value per share | (per share)	€ 34	$ 21.64
Number of shares issued during period shares	8,280,000	4,277,826
Private Placements Offering [Member]
Disclosure of classes of share capital [line items]
Number of common shares issued		534,728
Number of common shares issued per share | € / shares		$ 34

Capital - Summary of Historical

Capital - Summary of Historical Changes in the Share Capital of the Company (Detail) - EUR (€)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of classes of share capital [line items]
Beginning balance	€ 242,849,000	€ 322,076,000	€ 115,445,000
Ending balance	€ 129,923,000	242,849,000	322,076,000
Balance as of December 31, 2015	24,990,822
Share capital [Member]
Disclosure of classes of share capital [line items]
Beginning balance	€ 2,464,900	2,420,500	1,916,100
Ending balance	€ 2,499,100	€ 2,464,900	€ 2,420,500
Balance as of January 1, 2015	24,648,828	24,205,129	19,160,661
Balance as of December 31, 2015	24,990,822	24,648,828	24,205,129
Share premium [Member]
Disclosure of classes of share capital [line items]
Beginning balance	€ 405,882,500	€ 403,910,400	€ 163,876,800
Ending balance	406,709,300	405,882,500	403,910,400
01/06/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			400
01/06/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			18,900
01/07/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			1,000
01/07/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			59,000
01/22/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve			3,500
01/22/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve			(3,500)
01/30/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			9,800
01/30/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			476,800
02/03/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			800
02/03/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			37,700
02/13/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			3,800
02/13/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			188,600
02/17/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			2,000
02/17/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			100,600
03/04/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			1,000
03/04/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			59,000
03/26/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			5,000
03/26/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			400,000
04/07/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			4,000
04/07/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			169,200
04/09/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			15,000
04/09/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			692,100
04/28/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			1,400
04/28/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			77,100
05/11/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			2,000
05/11/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			100,700
06/23/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			59,100
06/23/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			27,029,400
06/23/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital Decrease			(58,600)
06/23/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital Decrease			(26,823,400)
07/20/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			414,000
07/20/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			254,932,900
07/24/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			1,600
07/24/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			79,200
07/25/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve			28,600
07/25/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve			(28,600)
07/28/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			1,700
07/28/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			91,500
09/18/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			300
09/18/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			46,700
10/07/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			4,800
10/07/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			241,200
12/10/2015 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			1,800
12/10/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			146,900
12/14/2015 [Member ] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			1,600
12/14/2015 [Member ] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			69,500
05/05/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Issue of share subscription warrants			43,000
12/10/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Issue of share subscription warrants			99,200
12/31/2015 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Fees charged to share premium			€ (18,269,700)
1/5/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		600
1/5/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		32,700
2/16/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Issue of share subscription warrants		471,100
4/6/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve		10,200
4/6/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve		(10,200)
5/27/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		200
5/27/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		7,500
6/3/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		15,600
6/3/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		(15,600)
6/6/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		6,000
6/6/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		301,200
6/10/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		3,500
6/10/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		176,000
7/18/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		2,000
7/18/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		100,700
8/4/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		1,000
8/4/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		50,400
8/24/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		700
8/24/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		37,100
8/30/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		400
8/30/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		66,200
8/31/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		400
8/31/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		66,200
9/1/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		400
9/1/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		66,200
9/2/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		400
9/2/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		66,200
9/5/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		400
9/5/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		66,200
9/6/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		400
9/6/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		66,200
9/6/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		400
9/6/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		66,200
9/8/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		400
9/8/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		66,200
9/9/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		400
9/9/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		66,200
9/12/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		400
9/12/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		66,200
9/12/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		500
9/12/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		23,100
11/25/2016 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		600
11/25/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		30,200
8/21/2016 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Issue of share subscription warrants		€ 106,000
02/03/2017 [member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	2,000
02/03/2017 [member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	100,700
05/16/2017 [member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	4,000
05/16/2017 [member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	170,700
07/12/2017 [member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	200
07/12/2017 [member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	8,300
08/04/2017 [member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	100
08/04/2017 [member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	64,600
09/14/2017 [member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	3,600
09/14/2017 [member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	208,200
Issue of share subscription warrants	53,100
09/29/2017 [member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	100
09/29/2017 [member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	4,000
09/30/2017 [member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve	23,100
09/30/2017 [member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve	(23,100)
10/02/2017 [Member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	100
10/02/2017 [Member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	4,000
12/15/2017 [member] | Share capital [Member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve	1,100
12/15/2017 [member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve	(1,100)
02/09/2017 [member] | Share premium [Member]
Disclosure of classes of share capital [line items]
Issue of share subscription warrants	€ 237,400
Common Shares [member]
Disclosure of classes of share capital [line items]
Balance as of January 1, 2015	24,648,828	24,205,129	19,160,661
Balance as of December 31, 2015	24,990,822	24,648,828	24,205,129
Beginning balance, Nominal value	€ 0.10	€ 0.10	€ 0.10
Ending balance, Nominal value	€ 0.10	€ 0.10	€ 0.10
Common Shares [member] | 01/06/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			3,750
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 01/07/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			10,000
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 01/22/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve			35,360
Capital increase by incorporation of reserve			€ 0.10
Common Shares [member] | 01/30/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			97,720
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 02/03/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			7,500
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 02/13/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			37,500
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 02/17/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			19,995
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 03/04/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			10,000
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 03/26/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			50,000
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 04/07/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			40,005
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 04/09/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			150,375
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 04/28/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			14,290
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 05/11/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			20,010
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 06/23/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			590,543
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 06/23/2015 [Member]
Disclosure of classes of share capital [line items]
Capital Decrease			(586,048)
Capital Decrease, Nominal value			€ 0.10
Common Shares [member] | 07/20/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			4,140,000
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 07/24/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			15,750
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 07/25/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve			286,338
Capital increase by incorporation of reserve			€ 0.10
Common Shares [member] | 07/28/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			17,000
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 09/18/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			2,500
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 10/07/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			47,955
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 12/10/2015 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			17,500
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 12/14/2015 [Member ]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares			16,425
Capital increase by issuance of common shares			€ 0.10
Common Shares [member] | 1/5/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		6,495
Common Shares [member] | 2/16/2016 [Member]
Disclosure of classes of share capital [line items]
Issue of share subscription warrants		0
Issue of share subscription warrants, Nominal value		€ 0.10
Common Shares [member] | 4/6/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve		101,829
Capital increase by incorporation of reserve		€ 0.10
Common Shares [member] | 5/27/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		1,500
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 6/3/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		156,000
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 6/6/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		59,890
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 6/10/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		34,985
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 7/18/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		20,010
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 8/4/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		10,020
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 8/24/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		7,380
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 8/30/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		3,500
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 8/31/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		3,500
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 9/1/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		3,500
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 9/2/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		3,500
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 9/5/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		3,500
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 9/6/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		3,500
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 9/6/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		3,500
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 9/8/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		3,500
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 9/9/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		3,500
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 9/12/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		3,500
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 9/12/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		4,590
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 11/25/2016 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares		6,000
Capital increase by issuance of common shares		€ 0.10
Common Shares [member] | 8/21/2016 [Member]
Disclosure of classes of share capital [line items]
Issue of share subscription warrants		0
Common Shares [member] | 02/03/2017 [member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	20,010
Capital increase by issuance of common shares	€ 0.10
Common Shares [member] | 05/16/2017 [member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	40,365
Capital increase by issuance of common shares	€ 0.10
Common Shares [member] | 07/12/2017 [member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	1,650
Capital increase by issuance of common shares	€ 0.10
Common Shares [member] | 08/04/2017 [member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	1,200
Capital increase by issuance of common shares	€ 0.10
Common Shares [member] | 09/14/2017 [member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	35,925
Capital increase by issuance of common shares	€ 0.10
Common Shares [member] | 09/29/2017 [member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	500
Capital increase by issuance of common shares	€ 0.10
Common Shares [member] | 09/30/2017 [member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve	230,843
Capital increase by incorporation of reserve	€ 0.10
Common Shares [member] | 10/02/2017 [Member]
Disclosure of classes of share capital [line items]
Capital increase by issuance of common shares	500
Capital increase by issuance of common shares	€ 0.10
Common Shares [member] | 12/15/2017 [member]
Disclosure of classes of share capital [line items]
Capital increase by incorporation of reserve	11,001
Capital increase by incorporation of reserve	€ 0.10

Capital - Summary of Share Warr

Capital - Summary of Share Warrants and Employee Warrants (Detail) - € / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of classes of share capital [line items]
Number of warrants issued	5,388,616	4,275,616	3,496,206
Number of warrants null and void	341,196	273,294	207,794
Number of warrants null and outstanding	3,148,469	2,360,945	2,033,768
Maximum number of shares to be issued	3,309,539	2,606,435	2,336,224
12/07/2007 [Member] | BSA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	1,717	1,717	1,717
Number of warrants null and void	572	572	572
Number of warrants null and outstanding		859	859
Maximum number of shares to be issued		12,885	12,885
Strike price per share	€ 4.33	€ 4.33	€ 4.33
1/21/2009 [Member] | BSA/BSPCE [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	16,380	16,380	16,380
Number of warrants null and outstanding		2,997	4,041
Maximum number of shares to be issued		44,955	60,615
Strike price per share	€ 4.33	€ 4.33	€ 4.33
1/21/2009 [Member] | BSPCE [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	2,296	2,296	2,296
Strike price per share	€ 4.33	€ 4.33	€ 4.33
6/25/2010 [Member] | BSA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	1,825	1,825	1,825
Number of warrants null and outstanding		730	730
Maximum number of shares to be issued		10,950	10,950
Strike price per share	€ 4.33	€ 4.33	€ 4.33
1/28/2011 [Member] | BSA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	10,039	10,039	10,039
Number of warrants null and void	7,529	7,529	7,529
Strike price per share	€ 5.13	€ 5.13	€ 5.13
6/24/2011 [Member] | BSA/BSPCE [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	32,000	32,000	32,000
Number of warrants null and outstanding	8,996	10,440	13,465
Maximum number of shares to be issued	134,940	156,600	201,975
Strike price per share	€ 5.13	€ 5.13	€ 5.13
11/22/2011 [Member] | BSA/BSPCE [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	11,377	11,377	11,377
Number of warrants null and outstanding	2,509	2,509	2,509
Maximum number of shares to be issued	37,635	37,635	37,635
Strike price per share	€ 5.13	€ 5.13	€ 5.13
1/17/2012 [Member] | BSA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	89,835	89,835	89,835
Number of warrants null and outstanding			89,835
Maximum number of shares to be issued			89,835
Strike price per share	€ 5.13	€ 5.13	€ 5.13
4/2/2012 [Member] | AGA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	669,796	669,796	669,796
Number of warrants null and void	1,860	1,860	1,860
7/25/2012 [Member] | AGA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	134,081	134,081	134,081
9/25/2012 [Member] | BSA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	30,000	30,000	30,000
Number of warrants null and outstanding	7,500	10,000	10,000
Maximum number of shares to be issued	7,500	10,000	10,000
Strike price per share	€ 8.59	€ 8.59	€ 8.59
11/28/2012 [Member] | AGA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	35,360	35,360	35,360
7/25/2013 [Member] | BSA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	73,000	73,000	73,000
Number of warrants null and outstanding	9,500	13,000	13,000
Maximum number of shares to be issued	9,500	13,000	13,000
Strike price per share	€ 8.10	€ 8.10	€ 8.10
9/12/2013 [Member] | AGA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	501,500	501,500	501,500
Number of warrants null and void	113,333	113,333	113,333
Number of warrants null and outstanding			101,829
Maximum number of shares to be issued			101,829
9/18/2013 [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	518,000	518,000	518,000
Number of warrants null and void	47,000	47,000	47,000
Number of warrants null and outstanding	471,000	471,000	471,000
Maximum number of shares to be issued	471,000	471,000	471,000
Strike price per share	€ 7.57	€ 7.57	€ 7.57
6/3/2014 [Member] | BSA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	10,000	10,000	10,000
Number of warrants null and outstanding	2,500	5,000	5,000
Maximum number of shares to be issued	2,500	5,000	5,000
Strike price per share	€ 18.79	€ 18.79	€ 18.79
6/3/2014 [Member] | AGA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	186,000	186,000	186,000
Number of warrants null and void	30,000	30,000	30,000
Number of warrants null and outstanding			156,000
Maximum number of shares to be issued			156,000
6/3/2014 [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	75,000	75,000	75,000
Number of warrants null and outstanding	40,000	40,000	75,000
Maximum number of shares to be issued	40,000	40,000	75,000
Strike price per share	€ 19.01	€ 19.01	€ 19.01
3/24/2015 [Member] | BSA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	10,000	10,000	10,000
Number of warrants null and outstanding	10,000	10,000	10,000
Maximum number of shares to be issued	10,000	10,000	10,000
Strike price per share	€ 43	€ 43	€ 43
6/23/2015 [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	120,000	120,000	120,000
Number of warrants null and outstanding	120,000	120,000	120,000
Maximum number of shares to be issued	120,000	120,000	120,000
Strike price per share	€ 48.90	€ 48.90	€ 48.90
9/30/2015 [Member] | AGA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	708,500	708,500	708,500
Number of warrants null and void	23,000	13,000
Number of warrants null and outstanding	454,657	695,500	708,500
Maximum number of shares to be issued	454,657	695,500	708,500
11/19/2015 [Member] | BSA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	22,500	22,500	22,500
Number of warrants null and void	7,500	7,500	7,500
Number of warrants null and outstanding	15,000	15,000	15,000
Maximum number of shares to be issued	15,000	15,000	15,000
Strike price per share	€ 66.06	€ 66.06	€ 66.06
11/19/2015 [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	195,000	195,000	195,000
Number of warrants null and void	25,000	25,000
Number of warrants null and outstanding	170,000	170,000	195,000
Maximum number of shares to be issued	170,000	170,000	195,000
Strike price per share	€ 66.06	€ 66.06	€ 66.06
12/15/2015 [Member] | BSA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	90,000	90,000
Number of warrants null and void	16,500	16,500
Number of warrants null and outstanding	73,500	73,500
Maximum number of shares to be issued	73,500	73,500
Strike price per share	€ 64.14	€ 64.14
12/15/2015 [Member] | AGA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	42,000	42,000	42,000
Number of warrants null and void	9,000	6,000
Number of warrants null and outstanding	21,999	36,000	42,000
Maximum number of shares to be issued	21,999	36,000	42,000
1/4/2016 [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	75,000	75,000
Number of warrants null and outstanding	75,000	75,000
Maximum number of shares to be issued	75,000	75,000
Strike price per share	€ 65.68	€ 65.68
4/6/2016 [Member] | AGA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	63,750	63,750
Number of warrants null and void	6,250	5,000
Number of warrants null and outstanding	57,500	58,750
Maximum number of shares to be issued	57,500	58,750
4/21/2016 [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	33,000	33,000
Number of warrants null and outstanding	33,000	33,000
Maximum number of shares to be issued	33,000	33,000
Strike price per share	€ 62.82	€ 62.82
5/2/2016 [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	22,000	22,000
Number of warrants null and outstanding	22,000	22,000
Maximum number of shares to be issued	22,000	22,000
Strike price per share	€ 59.04	€ 59.04
6/21/2016 [Member] | BSA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	20,000	20,000
Number of warrants null and outstanding	20,000	20,000
Maximum number of shares to be issued	20,000	20,000
Strike price per share	€ 52.97	€ 52.97
6/21/2016 [Member] | AGA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	208,000	208,000
Number of warrants null and outstanding	208,000	208,000
Maximum number of shares to be issued	208,000	208,000
6/21/2016 [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	110,000	110,000
Number of warrants null and void	7,500
Number of warrants null and outstanding	101,300	110,000
Maximum number of shares to be issued	101,300	110,000
Strike price per share	€ 53.96	€ 53.96
8/1/2016 [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	10,000	10,000
Number of warrants null and outstanding	10,000	10,000
Maximum number of shares to be issued	10,000	10,000
Strike price per share	€ 62.24	€ 62.24
9/15/2016 [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	9,300	9,300
Number of warrants null and outstanding	9,300	9,300
Maximum number of shares to be issued	9,300	9,300
Strike price per share	€ 62.80	€ 62.80
10/17/2016 [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	16,500	16,500
Number of warrants null and void	7,200
Number of warrants null and outstanding	9,300	16,500
Maximum number of shares to be issued	9,300	16,500
Strike price per share	€ 64.39	€ 64.39
10/27/2016 [Member] | AGA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	15,000	15,000
Number of warrants null and outstanding	15,000	15,000
Maximum number of shares to be issued	15,000	15,000
11/15/2016 [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	8,300	8,300
Number of warrants null and outstanding	8,300	8,300
Maximum number of shares to be issued	8,300	8,300
Strike price per share	€ 68.33	€ 68.33
12/9/2016 [Member] | BSA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	59,000
Number of warrants null and void	24,992
Number of warrants null and outstanding	34,008
Maximum number of shares to be issued	34,008
Strike price per share	€ 69.75
12/9/2016 [Member] | AGA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	23,600	23,600
Number of warrants null and void	1,900
Number of warrants null and outstanding	21,700	23,600
Maximum number of shares to be issued	21,700	23,600
12/9/2016 [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	74,960	74,960
Number of warrants null and void	2,000
Number of warrants null and outstanding	72,000	74,960
Maximum number of shares to be issued	72,000	74,960
Strike price per share	€ 69.75	€ 6,975
December fifteen two thousand and sixteen [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	1,100
Number of warrants null and outstanding	1,100
Maximum number of shares to be issued	1,100
Strike price per share	€ 69.35
January Sixteen Two thousand And Seventeen [member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	19,100
Number of warrants null and outstanding	19,100
Maximum number of shares to be issued	19,100
Strike price per share	€ 66.11
March Fourteen two thousand Seventeen [member] | AGA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	22,500
Number of warrants null and void	2,500
Number of warrants null and outstanding	20,000
Maximum number of shares to be issued	20,000
March Fifteen two thousand Seventeen [member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	7,200
Number of warrants null and outstanding	7,200
Maximum number of shares to be issued	7,200
Strike price per share	€ 66.25
April Eighteen Two Thousand Seventeen [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	16,500
Number of warrants null and outstanding	16,500
Maximum number of shares to be issued	16,500
Strike price per share	€ 60.77
April twenty two thousand seventeen [member] | AGA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	24,000
Number of warrants null and outstanding	24,000
Maximum number of shares to be issued	24,000
June Fifteen Two Thousand Seventeen [Member] | BSA [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	9,000
Number of warrants null and outstanding	9,000
Maximum number of shares to be issued	9,000
Strike price per share	€ 59.05
June Fifteen Two Thousand Seventeen [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	126,000
Number of warrants null and void	7,500
Number of warrants null and outstanding	118,500
Maximum number of shares to be issued	118,500
Strike price per share	€ 59.05
June Fifteen Two Thousand Seventeen [Member] | Share Option [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	111,600
Number of warrants null and outstanding	111,600
Maximum number of shares to be issued	111,600
Strike price per share	€ 60.54
July Seventeen Two Thousand Seventeen [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	30,900
Number of warrants null and outstanding	30,900
Maximum number of shares to be issued	30,900
Strike price per share	€ 71.61
September Fifteen Two Thousand Seventeen [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	52,600
Number of warrants null and outstanding	52,600
Maximum number of shares to be issued	52,600
Strike price per share	€ 74.22
December Five two thousand and seventeen [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	625,200
Number of warrants null and outstanding	625,200
Maximum number of shares to be issued	625,200
Strike price per share	€ 39
December fifteen two thousand and seventeen [Member] | SO [Member]
Disclosure of classes of share capital [line items]
Number of warrants issued	8,300
Number of warrants null and outstanding	8,300
Maximum number of shares to be issued	8,300
Strike price per share	€ 38.08

Financial and Other Non-Curre70

Financial and Other Non-Current Liabilities - Additional Information (Detail)	Jun. 30, 2024EUR (€)	Jun. 30, 2023EUR (€)	Jun. 30, 2022EUR (€)	Jun. 30, 2021EUR (€)	Jun. 30, 2017EUR (€)	Sep. 30, 2015EUR (€)	Jan. 22, 2015EUR (€)	Sep. 30, 2014EUR (€)	Apr. 30, 2018EUR (€)	Oct. 31, 2015EUR (€)	Oct. 31, 2014EUR (€)	Apr. 30, 2013EUR (€)	Dec. 31, 2017EUR (€)Contracts	Dec. 31, 2016EUR (€)Installments	Dec. 31, 2015EUR (€)	Dec. 31, 2014EUR (€)	Dec. 31, 2013EUR (€)	Dec. 31, 2011EUR (€)
Disclosure of Detailed Information About Financial Instruments [line items]
Advances repayable at nominal value													100.00%
Number of advance contracts | Contracts													2
Income earned on termination of contract														€ 146,000
Cash collected from conditional advance															€ 865,000
Repayment of conditional advance													€ 578,000	275,000	192,000
Borrowing to be repaid regardless of outcome														€ 256,000
Number of installment payments | Installments														4
Installment payment start date														Sep. 30, 2014
Borrowing to be paid in installment														€ 64,000
Financial assistance													4,150,000	4,628,000	4,809,000	€ 4,047,000
Current financial liabilities													2,325,000	591,000	149,000
Non-current part of deferred revenue													7,000,000
3rd OSEO contract [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Cash collected from conditional advance																128,000	€ 256,000	€ 256,000
Repayment of conditional advance													128,000	128,000	192,000
Financial assistance													64,000	192,000	318,000	507,000
3rd OSEO contract [member] | Top of range [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Cash collected from conditional advance																		€ 640,000
Repayment of conditional advance						€ 32,000		€ 64,000
4th OSEO contract [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Cash collected from conditional advance							€ 864,989			€ 918,000	€ 903,500	€ 903,500			865,000
Financial assistance													€ 1,700,000	€ 1,684,000	€ 1,669,000	805,000
Annual interest rate on advance													2.05%	2.05%	2.05%
Conditional advance, including interest to be paid															€ 3,750,000
Current financial liabilities													€ 1,700,000
4th OSEO contract [member] | Collaborative research and clinical development [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Cash collected from conditional advance																	€ 3,206,162
4th OSEO contract [member] | Scenario, Forecast [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Cash collected from conditional advance									€ 481,162
4th OSEO contract [member] | Scenario, Forecast [member] | Top of range [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Repayment of conditional advance	€ 1,450,000	€ 1,100,000	€ 800,000	€ 400,000
BPI advance [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Cash collected from conditional advance																3,000,000
Repayment of conditional advance					€ 150,000								450,000
Financial assistance													2,386,000	€ 2,751,000	2,666,000	2,584,000
Number of quarterly repayments					20
COFACE [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Income earned on termination of contract														146,000
Cash collected from conditional advance													€ 147,000
Repayment of conditional advance														€ 147,000
Financial assistance															€ 156,000	€ 151,000
Proportion of revenue to be paid in advance by the company													7.00%
Agreement termination date														Dec. 31, 2016

Financial and Other Non-Curre71

Financial and Other Non-Current Liabilities - Summary of Debt Recorded on Statement of Financial Position (Detail) (Detail) - EUR (€)	Jun. 30, 2017	Sep. 30, 2015	Jan. 22, 2015	Sep. 30, 2014	Oct. 31, 2015	Oct. 31, 2014	Apr. 30, 2013	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2011
Disclosure of detailed information about borrowings [line items]
Beginning balance								€ 4,628,000	€ 4,809,000	€ 4,047,000
Receipts										865,000
Repayments								(578,000)	(275,000)	(192,000)
Other transactions								101,000	95,000	89,000
Ending balance								4,150,000	4,628,000	4,809,000	€ 4,047,000
Of which - non-currentportion								1,825,000	4,049,000	4,681,000
Of which - current portion								2,325,000	578,000	128,000
3rd OSEO contract [member]
Disclosure of detailed information about borrowings [line items]
Beginning balance								192,000	318,000	507,000
Receipts											128,000	€ 256,000	€ 256,000
Repayments								(128,000)	(128,000)	(192,000)
Other transactions								1,000	2,000	3,000
Ending balance								64,000	192,000	318,000	507,000
4th OSEO contract [member]
Disclosure of detailed information about borrowings [line items]
Beginning balance								1,684,000	1,669,000	805,000
Receipts			€ 864,989		€ 918,000	€ 903,500	€ 903,500			865,000
Other transactions								16,000	16,000	(2,000)
Ending balance								€ 1,700,000	€ 1,684,000	€ 1,669,000	805,000
Stated interest rate								2.05%	2.05%	2.05%
BPI advance [member]
Disclosure of detailed information about borrowings [line items]
Beginning balance								€ 2,751,000	€ 2,666,000	€ 2,584,000
Repayments	€ (150,000)							(450,000)
Other transactions								84,000	85,000	82,000
Ending balance								€ 2,386,000	€ 2,751,000	€ 2,666,000	2,584,000
Discount rate								3.20%	3.20%	3.20%
COFACE [member]
Disclosure of detailed information about borrowings [line items]
Beginning balance									€ 156,000	€ 151,000
Repayments									(147,000)
Other transactions									€ (9,000)	5,000
Ending balance										€ 156,000	€ 151,000
Discount rate									4.25%	4.25%
Maturity (in years)									0	0
Bottom of range [member] | 3rd OSEO contract [member]
Disclosure of detailed information about borrowings [line items]
Discount rate								0.40%	0.40%	0.40%
Maturity (in years)								0	0	0
Bottom of range [member] | 4th OSEO contract [member]
Disclosure of detailed information about borrowings [line items]
Discount rate								1.50%	1.50%	1.50%
Maturity (in years)								7	7	7
Bottom of range [member] | BPI advance [member]
Disclosure of detailed information about borrowings [line items]
Maturity (in years)								2	2	2
Top of range [member] | 3rd OSEO contract [member]
Disclosure of detailed information about borrowings [line items]
Repayments		€ (32,000)		€ (64,000)
Discount rate								1.90%	1.90%	1.90%
Maturity (in years)								3	3	3
Top of range [member] | 4th OSEO contract [member]
Disclosure of detailed information about borrowings [line items]
Discount rate								1.80%	1.80%	1.80%
Maturity (in years)								9	9	9
Top of range [member] | BPI advance [member]
Disclosure of detailed information about borrowings [line items]
Maturity (in years)								7	7	7
Scenario, Previously Reported [Member]
Disclosure of detailed information about borrowings [line items]
Beginning balance								€ 4,627,000
Ending balance									€ 4,627,000

Financial and Other Non-Curre72

Financial and Other Non-Current Liabilities - Summary of Due Dates of the Financial Liabilities (Detail) - EUR (€)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of financial liabilities [line items]
Non-current conditional advances	€ 1,825,000	€ 4,049,000	€ 4,681,000
Current conditional advances	2,325,000	578,000	128,000
Supplier accounts payable and related payables	0
Not Later Than One Year [member]
Disclosure of financial liabilities [line items]
Current conditional advances	2,325,000	578,000	128,000
Current financial rent debts		12,000	21,000
Other current liabilities	15,751,000	14,692,000
Supplier accounts payable and related payables	16,941,000	13,720,000	10,034,000
Total financial liabilities	35,017,000	29,003,000	10,183,000
Later than one year and not later than five years [member]
Disclosure of financial liabilities [line items]
Non-current conditional advances	1,825,000	2,531,000	2,378,000
Non-current financial rent debts			12,000
Other non-current liabilities	8,421,000	10,370,000
Total financial liabilities	10,246,000	12,900,000	2,391,000
2021 [member]
Disclosure of financial liabilities [line items]
Non-current conditional advances		1,518,000	2,302,000
Other non-current liabilities	448,000	377,000
Total financial liabilities	448,000	1,895,000	2,302,000
Total, gross [member]
Disclosure of financial liabilities [line items]
Non-current conditional advances	1,825,000	4,049,000	4,681,000
Non-current financial rent debts			12,000
Other non-current liabilities	8,869,000	10,746,000
Current conditional advances	2,325,000	578,000	128,000
Current financial rent debts		12,000	21,000
Other current liabilities	15,751,000	14,692,000
Supplier accounts payable and related payables	16,941,000	13,720,000	10,034,000
Total financial liabilities	€ 45,711,000	€ 43,798,000	€ 14,876,000

Non-Current Provisions - Schedu

Non-Current Provisions - Schedule of Non-Current Provisions (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of other provisions [abstract]
Pension retirement obligations	€ 1,260	€ 853	€ 490
Total	€ 1,260	€ 853	€ 490	€ 531

Non-Current Provisions - Sche74

Non-Current Provisions - Schedule of Commitments for Compensation Payable to Employees Upon Their Retirement (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Retirement Benefits [Abstract]
Beginning balance	€ (853)	€ (490)	€ (531)
Costs of services rendered (operating expense)	(219)	(104)	(116)
Interest expense (finance expense)	(11)	(10)	(9)
Benefit paid	0	0	0
Actuarial gains	(177)	(249)	166
Ending balance	€ (1,260)	€ (853)	€ (490)

Non-Current Provisions - Sche75

Non-Current Provisions - Schedule of Retirement Commitments (Detail)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of sensitivity analysis for actuarial assumptions [abstract]
% social security contributions	50.00%	50.00%	50.00%
Salary increases	2.00%	2.00%	2.00%
Discount rate	1.30%	1.31%	2.08%

Non-Current Provisions - Additi

Non-Current Provisions - Additional Information (Detail) - yr	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Noncurrent Provisions [Abstract]
Retirement age of employee	65	65	65

Supplier Accounts Receivable 77

Supplier Accounts Receivable and Other Current Liabilities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017EUR (€)
Disclosure Of Supplier Accounts And Other Current Liabilities [Abstract]
Supplier accounts payable and related payables	€ 0
Supplier accounts and related payables term	1 year

Supplier Accounts Receivable 78

Supplier Accounts Receivable and Other Current Liabilities - Schedule of Other Current Liabilities (Details) (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Supplier Accounts And Other Current Liabilities [Abstract]
Social security	€ 12,094	€ 10,794	€ 4,464
Tax liabilities	428	504	388
Other debts	440	146	195
Deferred revenues	2,789	3,248	791
Total	€ 15,751	€ 14,692	€ 5,838

Financial Instruments Recogni79

Financial Instruments Recognized in the Consolidated Statements of Financial Position and Related Effect on the Consolidated Statements of (Loss) - Schedule of Financial Instruments Recognized in the Consolidated Statements of Financial Position and Related Effect on the Consolidated Statements of (Loss) (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets, fair value	€ 142,534	€ 260,985	€ 326,425
Financial liabilities, fair value	45,711	43,798	20,714
Long-term conditional advances [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities, fair value			4,681
Long term financial rent debt [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities, fair value			12
Short term conditional advances [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities, fair value			128
Short term financial rent debt [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities, fair value			21
Account payable and other liabilities [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities, fair value			15,872
Carrying amount [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities	45,711	43,798	20,714
Carrying amount [member] | Long-term conditional advances [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities			4,681
Carrying amount [member] | Long term financial rent debt [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities			12
Carrying amount [member] | Short term conditional advances [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities			128
Carrying amount [member] | Short term financial rent debt [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities			21
Carrying amount [member] | Account payable and other liabilities [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities			15,872
Financial liabilities at amortised cost, category [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities	45,711	43,798	20,714
Financial liabilities at amortised cost, category [member] | Long-term conditional advances [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities			4,681
Financial liabilities at amortised cost, category [member] | Long term financial rent debt [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities			12
Financial liabilities at amortised cost, category [member] | Short term conditional advances [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities			128
Financial liabilities at amortised cost, category [member] | Short term financial rent debt [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities			21
Financial liabilities at amortised cost, category [member] | Account payable and other liabilities [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities			15,872
Long-term financial assets [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets, fair value	3,012	2,745	2,711
Customer accounts receivables and related receivables [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets, fair value	1,265	1,250
Other current financial assets [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets, fair value	378	516	333
Cash and cash equivalent [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets, fair value	137,880	256,473	323,381
Long-term conditional advances [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities, fair value	1,825	4,049
Long-term conditional advances [member] | Carrying amount [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities	1,825	4,049
Long-term conditional advances [member] | Financial liabilities at amortised cost, category [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities	1,825	4,049
Other long term liabilities [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities, fair value	8,869	10,746
Other long term liabilities [member] | Carrying amount [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities	8,869	10,746
Other long term liabilities [member] | Financial liabilities at amortised cost, category [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities	8,869	10,746
Short term conditional advances [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities, fair value	2,325	578
Short term conditional advances [member] | Carrying amount [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities	2,325	578
Short term conditional advances [member] | Financial liabilities at amortised cost, category [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities	2,325	578
Short term financial rent debt [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities, fair value		12
Short term financial rent debt [member] | Carrying amount [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities		12
Short term financial rent debt [member] | Financial liabilities at amortised cost, category [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities		12
Other short term liabilities [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities, fair value	15,751	14,692
Other short term liabilities [member] | Carrying amount [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities	15,751	14,692
Other short term liabilities [member] | Financial liabilities at amortised cost, category [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities	15,751	14,692
Account payable and other liabilities [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities, fair value	16,941	13,720
Account payable and other liabilities [member] | Carrying amount [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities	16,941	13,720
Account payable and other liabilities [member] | Financial liabilities at amortised cost, category [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial liabilities	16,941	13,720
Carrying amount [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets	142,534	260,985	326,425
Carrying amount [member] | Long-term financial assets [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets	3,012	2,745	2,711
Carrying amount [member] | Customer accounts receivables and related receivables [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets	1,265	1,250
Carrying amount [member] | Other current financial assets [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets	378	516	333
Carrying amount [member] | Cash and cash equivalent [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets	137,880	256,473	323,381
Fair value through Consolidated Statements of (Loss) [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets	139,213	257,783	324,746
Fair value through Consolidated Statements of (Loss) [member] | Long-term financial assets [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets	1,333	1,310	1,365
Fair value through Consolidated Statements of (Loss) [member] | Cash and cash equivalent [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets	137,880	256,473	323,381
Loans and receivables, category [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets	3,321	3,202	1,679
Loans and receivables, category [member] | Long-term financial assets [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets	1,679	1,435	1,346
Loans and receivables, category [member] | Customer accounts receivables and related receivables [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets	1,265	1,250
Loans and receivables, category [member] | Other current financial assets [member]
Disclosure of Detailed Information About Financial Instruments [line items]
Financial assets	€ 378	€ 516	€ 333

Operating Income - Summary of O

Operating Income - Summary of Operating Income (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Analysis of income and expense [abstract]
Revenues			€ 202
Research tax credit	€ 9,330	€ 7,228	5,685
Subsidies	271	303	279
Other operating income	2,308	1,554
Total income	€ 11,909	€ 9,084	€ 6,166

Operating Income - Additional I

Operating Income - Additional Information (Detail) € in Millions	Dec. 31, 2017EUR (€)
Disclosure of finance income costs [abstract]
Deferred revenue	€ 9.5

Operating Expenses - Summary of

Operating Expenses - Summary of Research and Development (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Other Operating Expense [Abstract]
Personnel expenses	€ 37,112	€ 32,777	€ 13,268
Sub-contracting,collaboration, and consultants	54,397	34,413	15,325
Research supplies	1,464	1,234	911
Rental	2,018	1,903	1,094
Conferences, travel expenses	2,807	2,387	1,233
Depreciation and amortization	2,424	1,141	1,000
Small equipments and other supplies	2,646	2,675	795
Others	2,364	2,298	608
Total research and development expenses	€ 105,232	€ 78,828	€ 34,234

Operating Expenses - Summary 83

Operating Expenses - Summary of Sales and Marketing Expenses (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of sales and marketing expense [Abstract]
Personnel expenses	€ 6,976	€ 4,954	€ 133
Fees	2,480	4,447	339
Marketing, tradeshows and travel expenses	5,984	1,393	20
Others	384	487
Total sales and marketing expenses	€ 15,824	€ 11,282	€ 491

Operating Expenses - Summary 84

Operating Expenses - Summary of General and Administrative Expenses (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of General And Administrative Expense [Abstract]
Personnel expenses	€ 19,742	€ 22,613	€ 8,768
Fees	10,347	7,701	4,234
Rental	584	501	305
Insurance policies	1,367	1,853	1,239
Corporate communication and travel expenses	1,599	1,136	1,010
Depreciation and amortization	422	181	74
Others	1,776	1,020	1,229
Total general and administrative expenses	€ 35,837	€ 35,005	€ 16,859

Operating Expenses - Additional

Operating Expenses - Additional Information (Detail) - Employees	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of personnel expense [Abstract]
Number of employees	242	164	91

Operating Expenses - Summary 86

Operating Expenses - Summary of Personnel Expenses (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of personnel expense [Abstract]
Wages and salaries	€ 22,451	€ 14,651	€ 7,243
Social security contributions	7,157	3,903	3,193
Expenses for pension commitments	1,583	982	116
Employer contribution to bonus shares	1,857	6,456	1,198
Share-based payments	30,781	34,353	10,419
Total	€ 63,830	€ 60,345	€ 22,168

Share-Based Payments - Addition

Share-Based Payments - Additional Information (Detail)

Dec. 31, 2017shares

Dec. 15, 2017

Jun. 15, 2017shares

Dec. 15, 2016

Dec. 09, 2016

Jun. 24, 2016

Jun. 21, 2016shares

Apr. 06, 2016

Jan. 17, 2016

Dec. 15, 2015

Nov. 19, 2015

Sep. 30, 2015

Sep. 21, 2015

Jun. 23, 2015shares

Mar. 24, 2015

Dec. 23, 2014Equity

Jun. 03, 2014shares

Dec. 23, 2013Equity

Sep. 18, 2013

Jul. 25, 2013

Jun. 04, 2013shares

Dec. 23, 2012Equity

Sep. 25, 2012

Jan. 17, 2012

Dec. 23, 2011Equity

Dec. 09, 2011shares

Nov. 22, 2011

Jun. 24, 2011

Jan. 28, 2011

Dec. 16, 2010shares

Jun. 25, 2010

Jan. 21, 2009shares

Dec. 07, 2007

Jun. 14, 2007shares

Dec. 15, 2016

Sep. 30, 2016

Jan. 20, 2019

Dec. 31, 2017

Dec. 15, 2017

Dec. 05, 2017

Dec. 31, 2016

Dec. 31, 2015

Nov. 22, 2015Equity

Nov. 22, 2014Equity

Nov. 22, 2013Equity

Nov. 22, 2012Equity

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

8,300

625,200

Basis of exercise by beneficiary

181,008

181,008

147,359

53,859

Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting period

4 years

4 years

Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting period

1 year

1 year

BSAX [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

0

0

0

Date of grant (Board of Directors)

Jun. 25, 2010

Jan. 21, 2009

Share based payment arrangement, vesting percentage

P10Y

Share based payment arrangement, shares exercised

1,036

1,095

BSAX [Member] | Not Later Than One Year [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting Period

1 year

1 year

BSAX [Member] | Later Than One Year and Not Later Than Two Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting Period

2 years

2 years

BSAX [Member] | Later Than Two Years and Not Later Than Three Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting Period

3 years

3 years

BSAX [Member] | Later Than Three Years and Not Later Than Four Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting Period

4 years

4 years

BSAX [Member] | Top of range [member] | Not Later Than One Year [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Basis of exercise by beneficiary

25.00%

BSAX [Member] | Top of range [member] | Later Than One Year and Not Later Than Two Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Basis of exercise by beneficiary

25.00%

BSAX [Member] | Top of range [member] | Later Than Two Years and Not Later Than Three Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Basis of exercise by beneficiary

25.00%

BSAX [Member] | Top of range [member] | Later Than Three Years and Not Later Than Four Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Basis of exercise by beneficiary

25.00%

BCEX [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share-based payment arrangement shares issued on authorization

2,296

BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share-based payment arrangement shares issued on authorization

9,000

54,008

88,500

20,000

73,000

194,552

194,552

194,552

Share based payment arrangement, shares exercised

9,359

89,835

77,786

BSA [Member] | Date of Grant One [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Dec. 7, 2007

Share based payment arrangement, vesting period

10 years

BSA [Member] | Date of Grant One [Member] | Share-based Payment Arrangement Tranche One [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting period

1 year

BSA [Member] | Date of Grant One [Member] | Share-based Payment Arrangement Tranche Two [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting period

2 years

BSA [Member] | Date of Grant One [Member] | Share-based Payment Arrangement Tranche Three [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting period

3 years

BSA [Member] | Date of Grant One [Member] | Share-based Payment Arrangement Tranche Four [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting period

4 years

BSA [Member] | Date of Grant One [Member] | Top of range [member] | Share-based Payment Arrangement Tranche One [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting percentage

25.00%

BSA [Member] | Date of Grant One [Member] | Top of range [member] | Share-based Payment Arrangement Tranche Two [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting percentage

25.00%

BSA [Member] | Date of Grant One [Member] | Top of range [member] | Share-based Payment Arrangement Tranche Three [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting percentage

25.00%

BSA [Member] | Date of Grant One [Member] | Top of range [member] | Share-based Payment Arrangement Tranche Four [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting percentage

25.00%

BSA [Member] | Date of Grant Two [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Jan. 17, 2012

Share based payment arrangement, vesting period

10 years

BSA [Member] | Date of Grant Two [Member] | Share-based Payment Arrangement Tranche One [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting period

1 year

BSA [Member] | Date of Grant Two [Member] | Share-based Payment Arrangement Tranche Two [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting period

2 years

BSA [Member] | Date of Grant Two [Member] | Share-based Payment Arrangement Tranche Three [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting period

3 years

BSA [Member] | Date of Grant Two [Member] | Share-based Payment Arrangement Tranche Four [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting period

4 years

BSA [Member] | Date of Grant Two [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

89,835

BSA [Member] | Date of Grant Three [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Sep. 25, 2012

Share based payment arrangement, vesting period

10 years

BSA [Member] | Date of Grant Three [Member] | Share-based Payment Arrangement Tranche One [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting period

1 year

BSA [Member] | Date of Grant Three [Member] | Share-based Payment Arrangement Tranche Two [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting period

2 years

BSA [Member] | Date of Grant Three [Member] | Share-based Payment Arrangement Tranche Three [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting period

3 years

BSA [Member] | Date of Grant Three [Member] | Share-based Payment Arrangement Tranche Four [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting period

4 years

BSA [Member] | Date of Grant Three [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

30,000

BSA [Member] | Date of Grant Four [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Jul. 25, 2013

Share based payment arrangement, vesting period

0 years

10 years

BSA [Member] | Date of Grant Four [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

73,000

BSA [Member] | Date of Grant Five [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Jun. 3, 2014

Share based payment arrangement, vesting period

0 years

10 years

BSA [Member] | Date of Grant Five [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

10,000

BSA [Member] | Date of Grant 03/24/2015 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Mar. 24, 2015

Share based payment arrangement, vesting period

10 years

BSA [Member] | Date of Grant 03/24/2015 [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

10,000

BSA [Member] | Date of Grant Seven [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Nov. 19, 2015

Share based payment arrangement, vesting period

10 years

BSA [Member] | Date of Grant Seven [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

15,000

BSA [Member] | Date of Grant Eight [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Dec. 15, 2015

Share based payment arrangement, vesting period

10 years

BSA [Member] | Date of Grant Eight [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

73,500

BSA [Member] | Date of Grant 06/21/2016 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Jun. 21, 2016

Share based payment arrangement, vesting period

10 years

BSA [Member] | Date of Grant 06/21/2016 [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

20,000

BSA [Member] | Date of Grant 06/09/2016 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Dec. 9, 2016

Share based payment arrangement, vesting period

10 years

BSA [Member] | Date of Grant 06/09/2016 [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

34,008

BSA [Member] | Date of Grant 06/15/2017 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Jun. 15, 2019

Share based payment arrangement, vesting period

10 years

BSA [Member] | Date of Grant 06/15/2017 [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

9,000

BSA 2 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share-based payment arrangement shares issued on authorization

10,716

Bons De Createurs D Entreprise Bce Four [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share-based payment arrangement shares issued on authorization

5,358

BSA 2010 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share-based payment arrangement shares issued on authorization

19,377

BSAX[Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share-based payment arrangement shares issued on authorization

2,131

BSPCE2010 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share-based payment arrangement shares issued on authorization

34,039

OPTIONS 2013 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share-based payment arrangement shares issued on authorization

518,000

Free shares [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share-based payment arrangement shares issued on authorization

241,844

186,000

1,340,737

Number of options granted

1,107,350

Options [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share-based payment arrangement shares issued on authorization

828,600

918,960

BSA 2 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

0

0

0

Share based payment arrangement, shares exercised

8,049

BSA 2 [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

4,822

BSA 2 [Member] | Top of range [member] | First Anniversary [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

2,680

BSA 2 [Member] | Top of range [member] | Second Anniversary [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

1,072

BSA 2 [Member] | Top of range [member] | Third Anniversary [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

1,072

BSA 2 [Member] | Top of range [member] | Fourth Anniversary [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

1,070

BSA 2 [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting Period

10 years

BCE 4 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

0

0

0

Share based payment arrangement, shares exercised

2,691

2,667

BCE 4 [Member] | Not Later Than One Year [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

2,411

Date of grant (Board of Directors)

Jan. 21, 2009

Vesting Period

0 years

BCE 4 [Member] | Later Than One Year and Not Later Than Two Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

1,340

Date of grant (Board of Directors)

Jan. 21, 2009

Vesting Period

1 year

BCE 4 [Member] | Later Than Two Years and Not Later Than Three Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

536

Date of grant (Board of Directors)

Jan. 21, 2009

Vesting Period

2 years

BCE 4 [Member] | Later Than Three Years and Not Later Than Four Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

536

Date of grant (Board of Directors)

Jan. 21, 2009

Vesting Period

3 years

BCE 4 [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

2,411

BCE 4 [Member] | Top of range [member] | First Anniversary [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

1,340

BCE 4 [Member] | Top of range [member] | Second Anniversary [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

536

BCE 4 [Member] | Top of range [member] | Third Anniversary [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

536

BCE 4 [Member] | Top of range [member] | Fourth Anniversary [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

535

BSA [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting Period

10 years

BSA2010 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

2,000

0

0

0

Date of grant (Board of Directors)

Nov. 22, 2011

Jun. 24, 2011

Jan. 28, 2011

Share based payment arrangement, shares exercised

77

Basis of exercise by beneficiary | Equity

2,509

2,510

2,510

2,510

334

334

335

335

Basis of exercise by beneficiary

25.00%

25.00%

25.00%

25.00%

Share based payment arrangement, shares exercised

110

434

7,290

BSA2010 [Member] | Not Later Than One Year [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

335

Share based payment arrangement, shares exercised

77

BSA2010 [Member] | Later Than One Year and Not Later Than Two Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

335

Share based payment arrangement, shares exercised

77

BSA2010 [Member] | Later Than Two Years and Not Later Than Three Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

334

Share based payment arrangement, shares exercised

77

BSA2010 [Member] | Later Than Three Years and Not Later Than Four Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

334

Share based payment arrangement, shares exercised

77

BSA2010 [Member] | Date of Grant 06/09/2016 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

59,000

Share based payment arrangement, shares exercised

69.75

BSA2010 [Member] | Date of Grant 06/15/2017 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

9,000

Share based payment arrangement, shares exercised

59.05

BCE2010 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

1,334

3,635

13,998

Basis of exercise by beneficiary

11,005

11,005

12,339

15,974

BCE2010 [Member] | Date of Grant One [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Jun. 24, 2011

Share based payment arrangement, vesting percentage

At the latest within before the 11/22/2021

At the latest within before the 11/22/2021

BCE2010 [Member] | Date of Grant One [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting percentage

At the latest before the 12/15/2025

BCE2010 [Member] | Date of Grant One [Member] | Top of range [member] | Not Later Than One Year [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting percentage

25.00%

25.00%

25.00%

Basis of exercise by beneficiary

25.00%

BCE2010 [Member] | Date of Grant One [Member] | Top of range [member] | Later Than One Year and Not Later Than Two Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting percentage

25.00%

25.00%

25.00%

Basis of exercise by beneficiary

25.00%

BCE2010 [Member] | Date of Grant One [Member] | Top of range [member] | Later Than Two Years and Not Later Than Three Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting percentage

25.00%

25.00%

25.00%

Basis of exercise by beneficiary

25.00%

BCE2010 [Member] | Date of Grant One [Member] | Top of range [member] | Later Than Three Years and Not Later Than Four Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting percentage

25.00%

25.00%

25.00%

Basis of exercise by beneficiary

25.00%

BCE2010 [Member] | Date of Grant Two [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Sep. 18, 2013

Nov. 22, 2011

Share Option [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

998,500

359,060

315,000

Basis of exercise by beneficiary

755,650

755,650

85,000

Share based payment arrangement, shares exercised

1,200

35,000

Share Option [Member] | Date of Grant One [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Jun. 3, 2014

Share based payment arrangement, vesting period

10 years

Share based payment arrangement, vesting percentage

At the latest before the 06/03/2024

Share Option [Member] | Date of Grant One [Member] | Top of range [member] | Share-based Payment Arrangement Tranche Four [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

75,000

518,000

Share Option [Member] | Date of Grant Three [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Jun. 23, 2015

Share based payment arrangement, vesting percentage

At the latest before the 06/24/2025

Share Option [Member] | Date of Grant Three [Member] | Top of range [member] | Not Later Than One Year [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

30,000

Share Option [Member] | Date of Grant Three [Member] | Top of range [member] | Later Than One Year and Not Later Than Two Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

30,000

Share Option [Member] | Date of Grant Three [Member] | Top of range [member] | Later Than Two Years and Not Later Than Three Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

30,000

Share Option [Member] | Date of Grant Three [Member] | Top of range [member] | Later Than Three Years and Not Later Than Four Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

30,000

Share Option [Member] | Date of Grant Four [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Sep. 30, 2015

Share based payment arrangement, shares exercised

195,000

Share Option [Member] | Date of Grant Five [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Apr. 6, 2016

Dec. 15, 2015

Share based payment arrangement, shares exercised

75,000

Share Option [Member] | Date of Grant 03/24/2015 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting percentage

At the latest before 10 years of the date of the Grant

Share based payment arrangement, shares exercised

55,000

Share Option [Member] | Date of Grant Seven [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Jun. 21, 2016

Share based payment arrangement, vesting period

10 years

10 years

10 years

Share based payment arrangement, shares exercised

1,100

154,100

Share Option [Member] | Date of Grant Seven [Member] | Top of range [member] | Not Later Than One Year [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting percentage

25.00%

25.00%

25.00%

Share Option [Member] | Date of Grant Seven [Member] | Top of range [member] | Later Than One Year and Not Later Than Two Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting percentage

12.50%

12.50%

12.50%

Share Option [Member] | Date of Grant Seven [Member] | Top of range [member] | Later Than Two Years and Not Later Than Three Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting percentage

12.50%

12.50%

12.50%

Share Option [Member] | Date of Grant Seven [Member] | Top of range [member] | Later Than Three Years and Not Later Than Four Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, vesting percentage

12.50%

12.50%

12.50%

Share Option [Member] | Date of Grant Eight [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

Dec. 9, 2016

Share based payment arrangement, vesting period

10 years

Share based payment arrangement, shares exercised

74,960

Share Option [Member] | Date of Grant Eight [Member] | Top of range [member] | Not Later Than One Year [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

18,740

Share Option [Member] | Date of Grant Eight [Member] | Top of range [member] | Later Than One Year and Not Later Than Two Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

9,370

Share Option [Member] | Date of Grant Eight [Member] | Top of range [member] | Later Than Two Years and Not Later Than Three Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

9,370

Share Option [Member] | Date of Grant Eight [Member] | Top of range [member] | Later Than Three Years and Not Later Than Four Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

9,370

Share Option [Member] | Date of Grant 06/21/2016 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Date of grant (Board of Directors)

12/15/2016

Share Option [Member] | Grant Date Six A [Member] | Top of range [member] | Not Later Than One Year [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

8,250

Share Option [Member] | Grant Date Six A [Member] | Top of range [member] | Later Than One Year and Not Later Than Two Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

8,250

Share Option [Member] | Grant Date Six A [Member] | Top of range [member] | Later Than Two Years and Not Later Than Three Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

8,250

Share Option [Member] | Grant Date Six A [Member] | Top of range [member] | Later Than Three Years and Not Later Than Four Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

8,250

Share Option [Member] | Grant Date Six B [Member] | Top of range [member] | Not Later Than One Year [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

5,500

Share Option [Member] | Grant Date Six B [Member] | Top of range [member] | Later Than One Year and Not Later Than Two Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

5,500

Share Option [Member] | Grant Date Six B [Member] | Top of range [member] | Later Than Two Years and Not Later Than Three Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

5,500

Share Option [Member] | Grant Date Six B [Member] | Top of range [member] | Later Than Three Years and Not Later Than Four Years [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Share based payment arrangement, shares exercised

5,500

Share-Based Payments - Summary

Share-Based Payments - Summary of Details of Share Based Payment Arrangement BSA (Detail)

Nov. 19, 2025EUR (€)€ / shares

Mar. 24, 2025EUR (€)€ / shares

Jun. 15, 2017EUR (€)€ / sharesshares

Dec. 09, 2016EUR (€)€ / sharesshares

Jun. 21, 2016EUR (€)€ / shares

Dec. 15, 2015EUR (€)€ / shares

Jun. 03, 2014EUR (€)€ / shares

Jul. 25, 2013EUR (€)€ / shares

Sep. 25, 2012EUR (€)€ / shares

Jan. 17, 2012EUR (€)€ / shares

Jun. 24, 2011EUR (€)€ / sharesshares

Dec. 07, 2007EUR (€)€ / shares

Dec. 31, 2017

Dec. 15, 2017€ / shares

Dec. 05, 2017€ / shares

Dec. 31, 2016

Dec. 31, 2015

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

12/15/2027

12/05/2027

Share entitlement per BSA

€ 1

€ 1

Number of options granted

8,300

625,200

BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of BSA granted

68,000

93,500

25,000

Exercise price (in euros)

9,359

89,835

77,786

BSA2010 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

Nov. 22, 2021

Expected volatility

40.00%

Average life of BSA (in years)

0

Expected dividends

0.00%

Vesting period (years)

1 year 6 months

Number of options granted

2,000

0

0

0

Share entitlement per BSA | shares

15

Exercise price (in euros)

77

Grant date share fair value (in euros) | €

€ 77

Discount rate

2.68%

Fair value per BSA (in euros)

€ 32.70

Date of Grant Three [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

10 years

Date of Grant Three [Member] | Share-based Payment Arrangement Tranche One [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

Plan expiration date

Sep. 22, 2022

Share entitlement per BSA

€ 1

Exercise price (in euros) | €

€ 8.59

Expected volatility

40.00%

Discount rate

1.21%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 2.29

Grant date share fair value (in euros)

€ 8.40

Date of Grant Three [Member] | Share-based Payment Arrangement Tranche Two [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Plan expiration date

Sep. 22, 2022

Share entitlement per BSA

€ 1

Exercise price (in euros) | €

€ 8.59

Expected volatility

40.00%

Discount rate

1.21%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 2.43

Grant date share fair value (in euros)

€ 8.40

Date of Grant Three [Member] | Share-based Payment Arrangement Tranche Three [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

3 years

Plan expiration date

Sep. 22, 2022

Share entitlement per BSA

€ 1

Exercise price (in euros) | €

€ 8.59

Expected volatility

40.00%

Discount rate

1.53%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 2.61

Grant date share fair value (in euros)

€ 8.40

Date of Grant Three [Member] | Share-based Payment Arrangement Tranche Four [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

Plan expiration date

Sep. 25, 2022

Share entitlement per BSA

€ 1

Exercise price (in euros) | €

€ 8.59

Expected volatility

40.00%

Discount rate

1.53%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 2.74

Grant date share fair value (in euros)

€ 8.40

Date of Grant Four [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

0 years

10 years

Plan expiration date

Jul. 25, 2023

Share entitlement per BSA

€ 1

Exercise price (in euros) | €

€ 8.10

Expected volatility

40.00%

Discount rate

1.16%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 2.18

Grant date share fair value (in euros)

€ 8.15

Date of Grant Five [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

0 years

10 years

Plan expiration date

Jun. 3, 2024

Share entitlement per BSA

€ 1

Exercise price (in euros) | €

€ 18.79

Expected volatility

40.00%

Discount rate

0.71%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 4.98

Grant date share fair value (in euros)

€ 19.01

Date of Grant 03/24/2015 [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

10 years

Plan expiration date

Mar. 24, 2025

Number of BSA granted

10,000

Share entitlement per BSA

€ 1

Exercise price (in euros) | €

€ 43

Expected volatility

36.00%

Discount rate

0.68%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 9.90

Grant date share fair value (in euros)

€ 43

Date of Grant Seven [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

10 years

Plan expiration date

Nov. 19, 2025

Number of BSA granted

15,000

Share entitlement per BSA

€ 1

Exercise price (in euros) | €

€ 66.06

Expected volatility

50.91%

Discount rate

0.81%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 22.60

Grant date share fair value (in euros)

€ 66.06

Date of Grant Eight [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

10 years

Plan expiration date

Dec. 15, 2015

Share entitlement per BSA

€ 1

Exercise price (in euros) | €

€ 6,414

Expected volatility

51.00%

Discount rate

(0.09%)

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 7.28

Grant date share fair value (in euros)

€ 42.61

Date of Grant 06/21/2016 [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

10 years

Plan expiration date

Jun. 21, 2016

Number of BSA granted

20,000

Share entitlement per BSA

€ 1

Exercise price (in euros) | €

€ 52.97

Expected volatility

47.00%

Discount rate

(0.41%)

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 21.59

Grant date share fair value (in euros)

€ 61.25

Date of Grant 06/09/2016 [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

10 years

Date of Grant 06/09/2016 [Member] | BSA2010 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

Dec. 9, 2026

Expected volatility

40.00%

Average life of BSA (in years)

5

Expected dividends

0.00%

Vesting period (years)

0 years

Number of options granted

59,000

Share entitlement per BSA | shares

1

Exercise price (in euros)

69.75

Grant date share fair value (in euros) | €

€ 63.18

Discount rate

(0.04%)

Fair value per BSA (in euros)

€ 12.94

Date of Grant 06/15/2017 [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

10 years

Date of Grant 06/15/2017 [Member] | BSA2010 [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

Jun. 15, 2027

Expected volatility

39.00%

Average life of BSA (in years)

5

Expected dividends

0.00%

Vesting period (years)

0 years

Number of options granted

9,000

Share entitlement per BSA | shares

1

Exercise price (in euros)

59.05

Grant date share fair value (in euros) | €

€ 73.32

Discount rate

(0.12%)

Fair value per BSA (in euros)

€ 24.02

Date of Grant One [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

10 years

Date of Grant One [Member] | Share-based Payment Arrangement Tranche One [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

Plan expiration date

Dec. 8, 2017

Number of BSA granted

431

Share entitlement per BSA

€ 15

Exercise price (in euros) | €

€ 65

Grant date share fair value (in euros) | €

€ 65

Expected volatility

40.00%

Average life of BSA (in years)

4.5

Discount rate

4.06%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 22.18

Date of Grant One [Member] | Share-based Payment Arrangement Tranche Two [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Plan expiration date

Dec. 8, 2017

Number of BSA granted

431

Share entitlement per BSA

€ 15

Exercise price (in euros) | €

€ 65

Grant date share fair value (in euros) | €

€ 65

Expected volatility

40.00%

Average life of BSA (in years)

5

Discount rate

4.09%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 23.62

Date of Grant One [Member] | Share-based Payment Arrangement Tranche Three [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

3 years

Plan expiration date

Dec. 8, 2017

Number of BSA granted

428

Share entitlement per BSA

€ 15

Exercise price (in euros) | €

€ 65

Grant date share fair value (in euros) | €

€ 65

Expected volatility

40.00%

Average life of BSA (in years)

5.5

Discount rate

4.09%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 24.95

Date of Grant One [Member] | Share-based Payment Arrangement Tranche Four [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

Plan expiration date

Dec. 8, 2017

Number of BSA granted

427

Share entitlement per BSA

€ 15

Exercise price (in euros) | €

€ 65

Grant date share fair value (in euros) | €

€ 65

Expected volatility

40.00%

Average life of BSA (in years)

6

Discount rate

4.10%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 26.22

Date of Grant Two [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

10 years

Date of Grant Two [Member] | Share-based Payment Arrangement Tranche One [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

Plan expiration date

Jan. 17, 2022

Number of BSA granted

22,459

Share entitlement per BSA

€ 1

Exercise price (in euros) | €

€ 5.13

Grant date share fair value (in euros) | €

€ 5.13

Expected volatility

40.00%

Average life of BSA (in years)

5.5

Discount rate

2.33%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 2.05

Date of Grant Two [Member] | Share-based Payment Arrangement Tranche Two [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Plan expiration date

Jan. 17, 2022

Number of BSA granted

22,459

Share entitlement per BSA

€ 1

Exercise price (in euros) | €

€ 5.13

Grant date share fair value (in euros) | €

€ 5.13

Expected volatility

40.00%

Average life of BSA (in years)

6

Discount rate

2.33%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 2.14

Date of Grant Two [Member] | Share-based Payment Arrangement Tranche Three [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

3 years

Plan expiration date

Jan. 17, 2022

Number of BSA granted

22,459

Share entitlement per BSA

€ 1

Exercise price (in euros) | €

€ 5.13

Grant date share fair value (in euros) | €

€ 5.13

Expected volatility

40.00%

Average life of BSA (in years)

6.5

Discount rate

2.61%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 2.26

Date of Grant Two [Member] | Share-based Payment Arrangement Tranche Four [Member] | BSA [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

Plan expiration date

Jan. 17, 2022

Number of BSA granted

22,458

Share entitlement per BSA

€ 1

Exercise price (in euros) | €

€ 5.13

Grant date share fair value (in euros) | €

€ 5.13

Expected volatility

40.00%

Average life of BSA (in years)

7

Discount rate

2.61%

Expected dividends

0.00%

Fair value per BSA (in euros)

€ 2.34

Share-Based Payments - Summar89

Share-Based Payments - Summary of Details of Share Based Payment Arrangement BSA (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017
BSA [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Description of price per share entitlement	The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BSA warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BSA plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans.

Share-Based Payments - Summar90

Share-Based Payments - Summary of Change in BSA Outstanding Number (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of terms and conditions of share-based payment arrangement [line items]
Balance at beginning of period	147,359	143,694
Balance at end of period	181,008	147,359	143,694
BSA [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Balance at beginning of period	147,359	143,694	196,480
Granted during the period	68,000	93,500	25,000
Forfeited during the period	24,902
Exercised during the period	9,359	89,835	77,786
Expired during the period	0	0	0
Balance at end of period	181,008	147,359	143,694

Share-Based Payments - Schedule

Share-Based Payments - Schedule of Breakdown of the Closing Balance BSA (Detail)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	181,008	147,359	143,694
Exercisable	181,008	147,359	53,859
Bons de souscriptiond actions two thousand ten [Member] | Exercise price 65 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding		859	859
Exercisable		859	859
Bons de souscriptiond actions two thousand ten [Member] | Exercise price 5.13 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding			89,835
Bons de souscriptiond actions two thousand ten [Member] | Exercise price 8.59 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	7,500	10,000	10,000
Exercisable	7,500	10,000	10,000
Bons de souscriptiond actions two thousand ten [Member] | Exercise price 8.1 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	9,500	13,000	13,000
Exercisable	9,500	13,000	13,000
Bons de souscriptiond actions two thousand ten [Member] | Exercise price18.79 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	2,500	5,000	5,000
Exercisable	2,500	5,000	5,000
BSA [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	181,008	147,359	143,694	196,480
BSA [Member] | Exercise price 43.00 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	10,000	10,000	10,000
Exercisable	10,000	10,000	10,000
BSA [Member] | Exercise price 66.06 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	15,000	15,000	15,000
Exercisable	15,000	15,000	15,000
BSA [Member] | Exercise price 64.14 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	73,500	73,500
Exercisable	73,500	73,500
BSA [Member] | Exercise price 52.97 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	20,000	20,000
Exercisable	20,000	20,000
BSA [Member] | Exercise price 69.75 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	34,008
Exercisable	34,008
BSA [Member] | Exercise price 59.05 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	9,000
Exercisable	9,000

Share-Based Payments - Schedu92

Share-Based Payments - Schedule of Breakdown of the Closing Balance (Detail)	Dec. 31, 2017$ / shares
Bons de souscriptiond actions two thousand ten [Member] | Exercise price 65 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	$ 65
Bons de souscriptiond actions two thousand ten [Member] | Exercise price 5.13 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	5.13
Bons de souscriptiond actions two thousand ten [Member] | Exercise price 8.59 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	8.59
Bons de souscriptiond actions two thousand ten [Member] | Exercise price 8.1 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	8.1
Bons de souscriptiond actions two thousand ten [Member] | Exercise price18.79 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	18.79
BSA [Member] | Exercise price 43.00 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	43
BSA [Member] | Exercise price 66.06 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	66.06
BSA [Member] | Exercise price 64.14 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	64.14
BSA [Member] | Exercise price 52.97 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	52.97
BSA [Member] | Exercise price 69.75 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	69.75
BSA [Member] | Exercise price 59.05 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	$ 59.05

Share-Based Payments - Summar93

Share-Based Payments - Summary Details of BSA2 (Detail)	Jan. 20, 2019EUR (€)€ / shares	Dec. 31, 2017	Dec. 15, 2017€ / shares	Dec. 05, 2017€ / shares	Dec. 31, 2016	Dec. 31, 2015
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options granted			8,300	625,200
Share entitlement per BSA2 | € / shares			€ 1	€ 1
BSA 2 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options granted		0			0	0
Board of Director [Member] | BSA 2 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	0 years
Plan expiration date	Jan. 20, 2019
Number of options granted	4,822
Share entitlement per BSA2 | € / shares	€ 15
Exercise price (in euros)	€ 65
Valuation method used
Grant date share fair value (in euros)	€ 70
Expected volatility	40.00%
Average life of BCE2010 (in years)	0
Discount rate	2.71%
Expected dividends	0.00%
Fair value per BSA2 (in euros)	€ 29.05
Board of Director [Member] | BSA 2 [Member] | First Anniversary [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	1 year
Plan expiration date	Jan. 20, 2019
Number of options granted	2,680
Share entitlement per BSA2 | € / shares	€ 15
Exercise price (in euros)	€ 65
Valuation method used
Grant date share fair value (in euros)	€ 70
Expected volatility	40.00%
Average life of BCE2010 (in years)	0
Discount rate	2.71%
Expected dividends	0.00%
Fair value per BSA2 (in euros)	€ 30.32
Board of Director [Member] | BSA 2 [Member] | Second Anniversary [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	2 years
Plan expiration date	Jan. 20, 2019
Number of options granted	1,072
Share entitlement per BSA2 | € / shares	€ 15
Exercise price (in euros)	€ 65
Valuation method used
Grant date share fair value (in euros)	€ 70
Expected volatility	40.00%
Average life of BCE2010 (in years)	0
Discount rate	2.98%
Expected dividends	0.00%
Fair value per BSA2 (in euros)	€ 31.89
Board of Director [Member] | BSA 2 [Member] | Third Anniversary [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	3 years
Plan expiration date	Jan. 20, 2019
Number of options granted	1,072
Share entitlement per BSA2 | € / shares	€ 15
Exercise price (in euros)	€ 65
Valuation method used
Grant date share fair value (in euros)	€ 70
Expected volatility	40.00%
Average life of BCE2010 (in years)	0
Discount rate	2.98%
Expected dividends	0.00%
Fair value per BSA2 (in euros)	€ 33.05
Board of Director [Member] | BSA 2 [Member] | Fourth Anniversary [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	4 years
Plan expiration date	Jan. 20, 2019
Number of options granted	1,070
Share entitlement per BSA2 | € / shares	€ 15
Exercise price (in euros)	€ 65
Valuation method used
Grant date share fair value (in euros)	€ 70
Expected volatility	40.00%
Average life of BCE2010 (in years)	0
Discount rate	3.11%
Expected dividends	0.00%
Fair value per BSA2 (in euros)	€ 33.45

Share-Based Payments - Summar94

Share-Based Payments - Summary Details of BSA2 (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017
BSA 2 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Description of subscribe shares	The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BSA2 warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BSA2 plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans.

Share-Based Payments - Summar95

Share-Based Payments - Summary of Change in Number of BSA 2 Outstanding (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 15, 2017	Dec. 05, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of terms and conditions of share-based payment arrangement [line items]
Granted during the period		8,300	625,200
BSA 2 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Balance at beginning of period	0			0	8,049
Granted during the period	0			0	0
Forfeited during the period	0			0	0
Exercised during the period					8,049
Expired during the period	0			0	0
Balance at end of period	0			0	0

Share-Based Payments - Schedu96

Share-Based Payments - Schedule of Breakdown of the Closing Balance BSA 2 (Detail) - BSA 2 [Member]	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	0	0	0	8,049
Exercisable	0	0	0
Exercise price 65 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	0	0	0
Exercisable	0	0	0

Share-Based Payments - Schedu97

Share-Based Payments - Schedule of Breakdown of the Closing Balance BSA 2 (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 15, 2017EUR (€)	Dec. 05, 2017EUR (€)
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price | €		€ 38.18	€ 39
Exercise price 65 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price | $	$ 65

Share-Based Payments - Summar98

Share-Based Payments - Summary Details of BCE4 (Detail)	12 Months Ended
	Jan. 20, 2019EUR (€)	Dec. 31, 2017	Dec. 15, 2017	Dec. 05, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of terms and conditions of share-based payment arrangement [line items]
Plan expiration date			12/15/2027	12/05/2027
Number of options granted			8,300	625,200
Black and Scholes Method [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Expected volatility			43.13%	43.23%
Expected dividends			0.00%	0.00%
BCE 4 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options granted		0			0	0
Not Later Than One Year [member] | BCE 4 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Date of grant (Board of Directors)	Jan. 21, 2009
Vesting period (years)	0 years
Plan expiration date	Jan. 20, 2019
Number of options granted	2,411
Share entitlement per BCE4	1500.00%
Exercise price (in euros)	€ 65
Not Later Than One Year [member] | BCE 4 [Member] | Black and Scholes Method [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Grant date share fair value (in euros)	€ 70
Expected volatility	40.00%
Average life of BCE4 (in years)	0
Discount rate	2.71%
Expected dividends	0.00%
Performance conditions	0.00%
Fair value per BCE4 (in euros)	2906.00%
Later Than One Year and Not Later Than Two Years [member] | BCE 4 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Date of grant (Board of Directors)	Jan. 21, 2009
Vesting period (years)	1 year
Plan expiration date	Jan. 20, 2019
Number of options granted	1,340
Share entitlement per BCE4	1500.00%
Exercise price (in euros)	€ 65
Later Than One Year and Not Later Than Two Years [member] | BCE 4 [Member] | Black and Scholes Method [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Grant date share fair value (in euros)	€ 70
Expected volatility	40.00%
Average life of BCE4 (in years)	0
Discount rate	2.71%
Expected dividends	0.00%
Performance conditions	0.00%
Fair value per BCE4 (in euros)	3033.00%
Later Than Two Years and Not Later Than Three Years [member] | BCE 4 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Date of grant (Board of Directors)	Jan. 21, 2009
Vesting period (years)	2 years
Plan expiration date	Jan. 20, 2019
Number of options granted	536
Share entitlement per BCE4	1500.00%
Exercise price (in euros)	€ 65
Later Than Two Years and Not Later Than Three Years [member] | BCE 4 [Member] | Black and Scholes Method [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Grant date share fair value (in euros)	€ 70
Expected volatility	40.00%
Average life of BCE4 (in years)	0
Discount rate	2.98%
Expected dividends	0.00%
Performance conditions	0.00%
Fair value per BCE4 (in euros)	3190.00%
Later Than Three Years and Not Later Than Four Years [member] | BCE 4 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Date of grant (Board of Directors)	Jan. 21, 2009
Vesting period (years)	3 years
Plan expiration date	Jan. 20, 2019
Number of options granted	536
Share entitlement per BCE4	1500.00%
Exercise price (in euros)	€ 65
Later Than Three Years and Not Later Than Four Years [member] | BCE 4 [Member] | Black and Scholes Method [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Grant date share fair value (in euros)	€ 70
Expected volatility	40.00%
Average life of BCE4 (in years)	0
Discount rate	2.98%
Expected dividends	0.00%
Performance conditions	0.00%
Fair value per BCE4 (in euros)	3306.00%
Later Than Four Years and Not Later Than Five Years [member] | BCE 4 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Date of grant (Board of Directors)	Jan. 21, 2009
Vesting period (years)	4 years
Plan expiration date	Jan. 20, 2019
Number of options granted	535
Share entitlement per BCE4	1500.00%
Exercise price (in euros)	€ 65
Later Than Four Years and Not Later Than Five Years [member] | BCE 4 [Member] | Black and Scholes Method [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Grant date share fair value (in euros)	€ 70
Expected volatility	40.00%
Average life of BCE4 (in years)	0
Discount rate	3.11%
Expected dividends	0.00%
Performance conditions	0.00%
Fair value per BCE4 (in euros)	3435.00%

Share-Based Payments - Summar99

Share-Based Payments - Summary Details of BCE4 (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017
BCE 4 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Description of price per share entitlement	The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BCE4 warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BCE4 plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans.

Share-Based Payments - Summa100

Share-Based Payments - Summary of Change in Number of BCE2 Outstanding (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 15, 2017	Dec. 05, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of terms and conditions of share-based payment arrangement [line items]
Granted during the period		8,300	625,200
BCE 4 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Balance at beginning of period	2,691			2,691	5,358
Granted during the period	0			0	0
Forfeited during the period	0			0	0
Exercised during the period	2,691				2,667
Expired during the period	0			0	0
Balance at end of period				2,691	2,691

Share-Based Payments - Sched101

Share-Based Payments - Schedule of Breakdown of the Closing Balance BCE4 (Detail) - BCE 4 [Member]	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	2,691	2,691	5,358
Exercisable	2,691	2,691
Exercise price 65 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	2,691	2,691
Exercisable	2,691	2,691

Share-Based Payments - Summa102

Share-Based Payments - Summary of Details of Share Based Payment Arrangement BSA 2010 (Detail)	Nov. 22, 2011EUR (€)€ / sharesshares	Jun. 24, 2011EUR (€)€ / sharesshares	Jan. 28, 2011EUR (€)€ / sharesshares	Dec. 31, 2017	Dec. 15, 2017	Dec. 05, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of terms and conditions of share-based payment arrangement [line items]
Plan expiration date					12/15/2027	12/05/2027
Number of options granted					8,300	625,200
BSA2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)		1 year 6 months
Plan expiration date		Nov. 22, 2021
Number of options granted		2,000		0			0	0
Share entitlement per BSA | shares		15
Exercise price (in euros)		77
Grant date share fair value (in euros) | €		€ 77
Expected volatility		40.00%
Average life of BSA (in years)		0
Discount rate		2.68%
Expected dividends		0.00%
Performance conditions		NA
Fair value per BSA (in euros) | € / shares		€ 32.70
Not Later Than One Year [member] | BSA2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	1 year
Plan expiration date	Nov. 22, 2021
Number of options granted	335
Share entitlement per BSA | shares	15
Exercise price (in euros)	77
Grant date share fair value (in euros) | €	€ 77
Expected volatility	40.00%
Average life of BSA (in years)	0
Discount rate	2.23%
Expected dividends	0.00%
Fair value per BSA (in euros) | € / shares	€ 30.70
Later Than One Year and Not Later Than Two Years [member] | BSA2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	2 years
Plan expiration date	Nov. 22, 2021
Number of options granted	335
Share entitlement per BSA | shares	15
Exercise price (in euros)	77
Grant date share fair value (in euros) | €	€ 77
Expected volatility	40.00%
Average life of BSA (in years)	0
Discount rate	2.60%
Expected dividends	0.00%
Fair value per BSA (in euros) | € / shares	€ 32.58
Later Than Two Years and Not Later Than Three Years [member] | BSA2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	3 years
Plan expiration date	Nov. 22, 2021
Number of options granted	334
Share entitlement per BSA | shares	15
Exercise price (in euros)	77
Grant date share fair value (in euros) | €	€ 77
Expected volatility	40.00%
Average life of BSA (in years)	0
Discount rate	2.60%
Expected dividends	0.00%
Fair value per BSA (in euros) | € / shares	€ 33.89
Later Than Three Years and Not Later Than Four Years [member] | BSA2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	4 years
Plan expiration date	Nov. 22, 2021
Number of options granted	334
Share entitlement per BSA | shares	15
Exercise price (in euros)	77
Grant date share fair value (in euros) | €	€ 77
Expected volatility	40.00%
Average life of BSA (in years)	0
Discount rate	2.85%
Expected dividends	0.00%
Fair value per BSA (in euros) | € / shares	€ 35.54
Zero Point Nine Year [Member] | BSA2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)			10 months 25 days
Plan expiration date			Jan. 27, 2021
Number of options granted			2,510
Share entitlement per BSA | shares			15
Exercise price (in euros)			77
Grant date share fair value (in euros) | €			€ 77
Expected volatility			40.00%
Average life of BSA (in years)			0
Discount rate			2.70%
Expected dividends			0.00%
Performance conditions			NA
Fair value per BSA (in euros) | € / shares			€ 31.33
One Point Nine Year [Member] | BSA2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)			1 year 10 months 25 days
Plan expiration date			Jan. 27, 2021
Number of options granted			2,510
Share entitlement per BSA | shares			15
Exercise price (in euros)			77
Grant date share fair value (in euros) | €			€ 77
Expected volatility			40.00%
Average life of BSA (in years)			0
Discount rate			2.82%
Expected dividends			0.00%
Performance conditions			NA
Fair value per BSA (in euros) | € / shares			€ 32.90
Two point Nine Year [Member] | BSA2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)			2 years 10 months 25 days
Plan expiration date			Jan. 27, 2021
Number of options granted			2,510
Share entitlement per BSA | shares			15
Exercise price (in euros)			77
Grant date share fair value (in euros) | €			€ 77
Expected volatility			40.00%
Average life of BSA (in years)			0
Discount rate			2.82%
Expected dividends			0.00%
Performance conditions			NA
Fair value per BSA (in euros) | € / shares			€ 34.23
Three Point Nine Year [Member] | BSA2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)			3 years 10 months 25 days
Plan expiration date			Jan. 27, 2021
Number of options granted			2,509
Share entitlement per BSA | shares			15
Exercise price (in euros)			77
Grant date share fair value (in euros) | €			€ 77
Expected volatility			40.00%
Average life of BSA (in years)			0
Discount rate			3.04%
Expected dividends			0.00%
Performance conditions			NA
Fair value per BSA (in euros) | € / shares			€ 35.84
Zero Point Five Year [Member] | BSA2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)		6 months
Plan expiration date		Nov. 22, 2021
Number of options granted		2,000
Share entitlement per BSA | shares		15
Exercise price (in euros)		77
Grant date share fair value (in euros) | €		€ 77
Expected volatility		40.00%
Average life of BSA (in years)		0
Discount rate		2.55%
Expected dividends		0.00%
Performance conditions		NA
Fair value per BSA (in euros) | € / shares		€ 31.15
Two Point Five Year [Member] | BSA2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)		2 years 6 months
Plan expiration date		Nov. 22, 2021
Number of options granted		2,000
Share entitlement per BSA | shares		15
Exercise price (in euros)		77
Grant date share fair value (in euros) | €		€ 77
Expected volatility		40.00%
Average life of BSA (in years)		0
Discount rate		2.68%
Expected dividends		0.00%
Performance conditions		NA
Fair value per BSA (in euros) | € / shares		€ 34.02
Three point Five Year [Member] | BSA2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)		3 years 6 months
Plan expiration date		Nov. 22, 2021
Number of options granted		2,000
Share entitlement per BSA | shares		15
Exercise price (in euros)		77
Grant date share fair value (in euros) | €		€ 77
Expected volatility		40.00%
Average life of BSA (in years)		0
Discount rate		2.87%
Expected dividends		0.00%
Performance conditions		NA
Fair value per BSA (in euros) | € / shares		€ 35.57

Share-Based Payments - SShare-B

Share-Based Payments - SShare-Based Payments - Summary Of Change in Number of BSA 2010 Outstanding (Detail)	Jun. 24, 2011	Dec. 31, 2017	Dec. 15, 2017	Dec. 05, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of terms and conditions of share-based payment arrangement [line items]
Granted during the period			8,300	625,200
BSA2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Balance at beginning of period		610			1,044	8,334
Granted during the period	2,000	0			0	0
Forfeited during the period		0			0	0
Exercised during the period		110			434	7,290
Expired during the period		0			0	0
Balance at end of period		500			610	1,044

Share-Based Payments - Share-Ba

Share-Based Payments - Share-Based Payments - Disclosure of Details of Breakdown of the Closing Balance BSA 2010 (Detail) - BSA2010 [Member]	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	500	610	1,044	8,334
Exercisable	500	610	1,044

Share-Based Payments - Share105

Share-Based Payments - Share-Based Payments - Disclosure of Details of Breakdown of the Closing Balance BSA 2010 (Parenthetical) (Detail)	Dec. 31, 2017EUR (€)
BSA2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	€ 77

Share-Based Payments - Summa106

Share-Based Payments - Summary of Details of Share Based Payment Arrangement BSAX (Detail)	Jun. 25, 2010EUR (€)€ / shares	Jan. 21, 2009EUR (€)€ / shares	Dec. 15, 2017€ / shares	Dec. 05, 2017€ / shares	Dec. 31, 2015EUR (€)
Disclosure of terms and conditions of share-based payment arrangement [line items]
Plan expiration date			12/15/2027	12/05/2027
Share entitlement per BCE2010(1) | € / shares			€ 1	€ 1
BSAX [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price (in euros)					€ 65
Not Later Than One Year [member] | BSAX [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	1 year	1 year
Plan expiration date	Jun. 24, 2020	Jan. 20, 2019
Number of BSAX granted	€ 457	€ 77
Share entitlement per BCE2010(1) | € / shares	€ 15	€ 15
Exercise price (in euros)	€ 65	€ 65
Not Later Than One Year [member] | BSAX [Member] | Option pricing model [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Grant date share fair value (in euros)	€ 70	€ 70
Expected volatility	40.00%	40.00%
Average life of BSAX (in years)	0	0
Discount rate	2.04%	2.71%
Expected dividends	0.00%	0.00%
Performance conditions	NA	NA
Fair value per BSAX (in euros) | € / shares	€ 29.47	€ 30.32
Later Than One Year and Not Later Than Two Years [member] | BSAX [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	2 years	2 years
Plan expiration date	Jun. 24, 2020	Jan. 20, 2019
Number of BSAX granted	€ 457	€ 77
Share entitlement per BCE2010(1) | € / shares	€ 15	€ 15
Exercise price (in euros)	€ 65	€ 65
Later Than One Year and Not Later Than Two Years [member] | BSAX [Member] | Option pricing model [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Grant date share fair value (in euros)	€ 70	€ 70
Expected volatility	40.00%	40.00%
Average life of BSAX (in years)	0	0
Discount rate	2.23%	2.98%
Expected dividends	0.00%	0.00%
Performance conditions	NA	NA
Fair value per BSAX (in euros) | € / shares	€ 30.88	€ 31.89
Later Than Two Years and Not Later Than Three Years [member] | BSAX [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	3 years	3 years
Plan expiration date	Jun. 24, 2020	Jan. 20, 2019
Number of BSAX granted	€ 456	€ 77
Share entitlement per BCE2010(1) | € / shares	€ 15	€ 15
Exercise price (in euros)	€ 65	€ 65
Later Than Two Years and Not Later Than Three Years [member] | BSAX [Member] | Option pricing model [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Grant date share fair value (in euros)	€ 70	€ 70
Expected volatility	40.00%	40.00%
Average life of BSAX (in years)	0	0
Discount rate	2.23%	2.98%
Expected dividends	0.00%	0.00%
Performance conditions	NA	NA
Fair value per BSAX (in euros) | € / shares	€ 31.99	€ 33.05
Later Than Three Years and Not Later Than Four Years [member] | BSAX [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	4 years	4 years
Plan expiration date	Jun. 24, 2020	Jan. 20, 2019
Number of BSAX granted	€ 455	€ 75
Share entitlement per BCE2010(1) | € / shares	€ 15	€ 15
Exercise price (in euros)	€ 65	€ 65
Later Than Three Years and Not Later Than Four Years [member] | BSAX [Member] | Option pricing model [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Grant date share fair value (in euros)	€ 70	€ 70
Expected volatility	40.00%	40.00%
Average life of BSAX (in years)	0	0
Discount rate	2.50%	3.11%
Expected dividends	0.00%	0.00%
Performance conditions	NA	NA
Fair value per BSAX (in euros) | € / shares	€ 33.44	€ 33.45

Share-Based Payments - Summa107

Share-Based Payments - Summary Of Change in Number of BSAX Outstanding (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 15, 2017	Dec. 05, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of terms and conditions of share-based payment arrangement [line items]
Granted during the period		8,300	625,200
BSAX [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Balance at beginning of period	1,036			1,036	1,036
Granted during the period	0			0	0
Forfeited during the period	0			0	0
Exercised during the period	1,036				1,095
Expired during the period	0			0	0
Balance at end of period				1,036	1,036
BSAX [Member] | Scenario, Previously Reported [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Balance at beginning of period					2,131

Share-Based Payments - Disclosu

Share-Based Payments - Disclosure of Details of Breakdown of the Closing Balance BSAX (Detail) - BSAX [Member]	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	1,036	1,036	1,036
Exercisable		1,036	1,036

Share-Based Payments - Discl109

Share-Based Payments - Disclosure of Details of Breakdown of the Closing Balance BSAX (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2015EUR (€)
BSAX [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	€ 65

Share-Based Payments - Summa110

Share-Based Payments - Summary of Details of Share Based Payment Arrangement BCE 2010 (Detail)	Nov. 22, 2011EUR (€)€ / shares	Jun. 24, 2011EUR (€)€ / shares	Dec. 31, 2017	Dec. 15, 2017EUR (€)€ / shares	Dec. 05, 2017EUR (€)€ / shares	Dec. 31, 2016	Dec. 31, 2015
Disclosure of terms and conditions of share-based payment arrangement [line items]
Plan expiration date				12/15/2027	12/05/2027
Share entitlement per BCE2010(1) | € / shares				€ 1	€ 1
Black and Scholes Method [Member]
Valuation method used
Grant date share fair value (in euros) | €				€ 36.43	€ 35.73
Expected volatility				43.13%	43.23%
Expected dividends				0.00%	0.00%
BCE2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of BCE2010 granted			0			0	0
Not Later Than One Year [member] | Date of Grant One [Member] | Board of Director [Member] | BCE2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)		6 months
Plan expiration date		Nov. 22, 2021
Number of BCE2010 granted		6,000
Share entitlement per BCE2010(1) | € / shares		€ 15
Exercise price (in euros) | €		€ 77
Not Later Than One Year [member] | Date of Grant One [Member] | Board of Director [Member] | BCE2010 [Member] | Black and Scholes Method [Member]
Valuation method used
Grant date share fair value (in euros) | €		€ 77
Expected volatility		40.00%
Average life of BCE2010 (in years)		0
Discount rate(2)		2.55%
Expected dividends		0.00%
Fair value per BCE2010 (in euros) | € / shares		€ 31.16
Not Later Than One Year [member] | Date of Grant Two [Member] | Board of Director [Member] | BCE2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	1 year
Plan expiration date	Nov. 22, 2021
Number of BCE2010 granted	2,510
Share entitlement per BCE2010(1) | € / shares	€ 15
Exercise price (in euros) | €	€ 77
Not Later Than One Year [member] | Date of Grant Two [Member] | Board of Director [Member] | BCE2010 [Member] | Black and Scholes Method [Member]
Valuation method used
Grant date share fair value (in euros) | €	€ 77
Expected volatility	40.00%
Average life of BCE2010 (in years)	0
Discount rate(2)	2.05%
Expected dividends	0.00%
Fair value per BCE2010 (in euros) | € / shares	€ 30.42
Later Than One Year and Not Later Than Two Years [member] | Date of Grant One [Member] | Board of Director [Member] | BCE2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)		1 year 6 months
Plan expiration date		Nov. 22, 2021
Number of BCE2010 granted		6,000
Share entitlement per BCE2010(1) | € / shares		€ 15
Exercise price (in euros) | €		€ 77
Later Than One Year and Not Later Than Two Years [member] | Date of Grant One [Member] | Board of Director [Member] | BCE2010 [Member] | Black and Scholes Method [Member]
Valuation method used
Grant date share fair value (in euros) | €		€ 77
Expected volatility		40.00%
Average life of BCE2010 (in years)		0
Discount rate(2)		2.68%
Expected dividends		0.00%
Fair value per BCE2010 (in euros) | € / shares		€ 32.71
Later Than One Year and Not Later Than Two Years [member] | Date of Grant Two [Member] | Board of Director [Member] | BCE2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	2 years
Plan expiration date	Nov. 22, 2021
Number of BCE2010 granted	2,510
Share entitlement per BCE2010(1) | € / shares	€ 15
Exercise price (in euros) | €	€ 77
Later Than One Year and Not Later Than Two Years [member] | Date of Grant Two [Member] | Board of Director [Member] | BCE2010 [Member] | Black and Scholes Method [Member]
Valuation method used
Grant date share fair value (in euros) | €	€ 77
Expected volatility	40.00%
Average life of BCE2010 (in years)	0
Discount rate(2)	2.42%
Expected dividends	0.00%
Fair value per BCE2010 (in euros) | € / shares	€ 32.29
Later Than Two Years and Not Later Than Three Years [member] | Date of Grant One [Member] | Board of Director [Member] | BCE2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)		2 years 6 months
Plan expiration date		Nov. 22, 2021
Number of BCE2010 granted		6,000
Share entitlement per BCE2010(1) | € / shares		€ 15
Exercise price (in euros) | €		€ 77
Later Than Two Years and Not Later Than Three Years [member] | Date of Grant One [Member] | Board of Director [Member] | BCE2010 [Member] | Black and Scholes Method [Member]
Valuation method used
Grant date share fair value (in euros) | €		€ 77
Expected volatility		40.00%
Average life of BCE2010 (in years)		0
Discount rate(2)		2.68%
Expected dividends		0.00%
Fair value per BCE2010 (in euros) | € / shares		€ 34.03
Later Than Two Years and Not Later Than Three Years [member] | Date of Grant Two [Member] | Board of Director [Member] | BCE2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	3 years
Plan expiration date	Nov. 22, 2021
Number of BCE2010 granted	2,510
Share entitlement per BCE2010(1) | € / shares	€ 15
Exercise price (in euros) | €	€ 77
Later Than Two Years and Not Later Than Three Years [member] | Date of Grant Two [Member] | Board of Director [Member] | BCE2010 [Member] | Black and Scholes Method [Member]
Valuation method used
Grant date share fair value (in euros) | €	€ 77
Expected volatility	40.00%
Average life of BCE2010 (in years)	0
Discount rate(2)	2.42%
Expected dividends	0.00%
Fair value per BCE2010 (in euros) | € / shares	€ 33.58
Later Than Three Years and Not Later Than Four Years [member] | Date of Grant One [Member] | Board of Director [Member] | BCE2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)		3 years 6 months
Plan expiration date		Nov. 22, 2021
Number of BCE2010 granted		6,000
Share entitlement per BCE2010(1) | € / shares		€ 15
Exercise price (in euros) | €		€ 77
Later Than Three Years and Not Later Than Four Years [member] | Date of Grant One [Member] | Board of Director [Member] | BCE2010 [Member] | Black and Scholes Method [Member]
Valuation method used
Grant date share fair value (in euros) | €		€ 77
Expected volatility		40.00%
Average life of BCE2010 (in years)		0
Discount rate(2)		2.87%
Expected dividends		0.00%
Fair value per BCE2010 (in euros) | € / shares		€ 35.58
Later Than Three Years and Not Later Than Four Years [member] | Date of Grant Two [Member] | Board of Director [Member] | BCE2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	4 years
Plan expiration date	Nov. 22, 2021
Number of BCE2010 granted	2,509
Share entitlement per BCE2010(1) | € / shares	€ 15
Exercise price (in euros) | €	€ 77
Later Than Three Years and Not Later Than Four Years [member] | Date of Grant Two [Member] | Board of Director [Member] | BCE2010 [Member] | Black and Scholes Method [Member]
Valuation method used
Grant date share fair value (in euros) | €	€ 77
Expected volatility	40.00%
Average life of BCE2010 (in years)	0
Discount rate(2)	2.66%
Expected dividends	0.00%
Fair value per BCE2010 (in euros) | € / shares	€ 35.20

Share-Based Payments - Summa111

Share-Based Payments - Summary of Details of Share Based Payment Arrangement BCE 2010 (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017
BCE2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Description of payment entitlement	The number of shares takes into account an exercise parity adjusted by the division by 15 of the nominal value of the shares decided by the general meeting on December 9, 2011; each BCE2010 warrant now gives the right to subscribe to 15 new shares instead of 1 new share. For the same reason, the exercise price of each BCE2010 plan was adjusted as a result and is thus equal to 1/15th of the price initially determined by the general meeting that authorized each of the plans

Share-Based Payments - Summa112

Share-Based Payments - Summary Of Change in Number of BCE 2010 Outstanding (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of terms and conditions of share-based payment arrangement [line items]
Balance at beginning of period	147,359	143,694
Balance at end of period	181,008	147,359	143,694
BCE2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Balance at beginning of period	12,339	15,974	29,972
Granted during the period	0	0	0
Forfeited during the period	0	0	0
Exercised during the period	1,334	3,635	13,998
Expired during the period	0	0	0
Balance at end of period	11,005	12,339	15,974

Share-Based Payments - Discl113

Share-Based Payments - Disclosure of Details of Breakdown of the Closing Balance BCE 2010 (Detail)	Dec. 31, 2017EUR (€)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	181,008	147,359	143,694
Exercisable	181,008	147,359	53,859
BCE2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	11,005	12,339	15,974	29,972
Exercisable	11,005	12,339	15,974
Exercise price, Exercisable	€ 77

Share-Based Payments - Discl114

Share-Based Payments - Disclosure of Details of Breakdown of the Closing Balance BCE 2010 (Parenthetical) (Detail)	Dec. 31, 2017EUR (€)
BCE2010 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price, outstanding	€ 77

Share-Based Payment - Additiona

Share-Based Payment - Additional information (Detail)	Dec. 15, 2017	Dec. 15, 2016	Dec. 09, 2016	Jun. 21, 2016	Dec. 31, 2017	Dec. 15, 2017	Dec. 05, 2017	Dec. 31, 2016
Top of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)						4 years	4 years
Share Option [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, shares exercised					1,200			35,000
Share Option [Member] | Date of Grant Seven [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, date of grant				Jun. 21, 2016
Share based payment arrangement, shares exercised	1,100			154,100
Vesting period (years)		10 years		10 years	10 years
Share Option [Member] | Date of Grant Eight [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, date of grant			Dec. 9, 2016
Share based payment arrangement, shares exercised			74,960
Vesting period (years)			10 years
Share Option [Member] | Date of Grant 06/21/2016 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, date of grant		12/15/2016
Share Option [Member] | Top of range [member] | Date of Grant Seven [Member] | Not Later Than One Year [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, vesting percentage		25.00%		25.00%	25.00%
Share Option [Member] | Top of range [member] | Date of Grant Seven [Member] | Later Than One Year and Not Later Than Two Years [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, vesting percentage		12.50%		12.50%	12.50%
Share Option [Member] | Top of range [member] | Date of Grant Seven [Member] | 24 months [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, vesting percentage		12.50%		12.50%	12.50%
Share Option [Member] | Top of range [member] | Date of Grant Seven [Member] | Later Than Two Years and Not Later Than Three Years [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, vesting percentage		12.50%		12.50%	12.50%
Share Option [Member] | Top of range [member] | Date of Grant Seven [Member] | 36 months [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, vesting percentage		12.50%		12.50%	12.50%
Share Option [Member] | Top of range [member] | Date of Grant Seven [Member] | Later Than Three Years and Not Later Than Four Years [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, vesting percentage		12.50%		12.50%	12.50%
Share Option [Member] | Top of range [member] | Date of Grant Seven [Member] | 48 months [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, vesting percentage		12.50%		12.50%	12.50%
Share Option [Member] | Top of range [member] | Date of Grant Eight [Member] | Not Later Than One Year [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, shares exercised			18,740
Share Option [Member] | Top of range [member] | Date of Grant Eight [Member] | Later Than One Year and Not Later Than Two Years [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, shares exercised			9,370
Share Option [Member] | Top of range [member] | Date of Grant Eight [Member] | 24 months [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, shares exercised			9,370
Share Option [Member] | Top of range [member] | Date of Grant Eight [Member] | Later Than Two Years and Not Later Than Three Years [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, shares exercised			9,370
Share Option [Member] | Top of range [member] | Date of Grant Eight [Member] | 36 months [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, shares exercised			9,370
Share Option [Member] | Top of range [member] | Date of Grant Eight [Member] | Later Than Three Years and Not Later Than Four Years [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, shares exercised			9,370
Share Option [Member] | Top of range [member] | Date of Grant Eight [Member] | 48 months [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, shares exercised			9,370

Share-Based Payments - Summa116

Share-Based Payments - Summary of Details of Share Based Payment Arrangement SO (Detail)

Sep. 15, 2017EUR (€)€ / shares

Jul. 17, 2017EUR (€)€ / shares

Jun. 15, 2017EUR (€)€ / shares

Apr. 18, 2017EUR (€)€ / shares

Mar. 15, 2017EUR (€)€ / shares

Jan. 16, 2017EUR (€)€ / shares

Dec. 15, 2016EUR (€)€ / shares

Dec. 09, 2016EUR (€)€ / shares

Nov. 15, 2016EUR (€)€ / shares

Oct. 17, 2016EUR (€)€ / shares

Sep. 15, 2016EUR (€)€ / shares

Aug. 01, 2016EUR (€)€ / shares

Jun. 21, 2016EUR (€)€ / shares

May 02, 2016EUR (€)€ / shares

Apr. 21, 2016EUR (€)€ / shares

Jan. 04, 2016EUR (€)€ / shares

Nov. 19, 2015EUR (€)€ / shares

Jun. 23, 2015EUR (€)€ / shares

Jun. 03, 2014EUR (€)€ / shares

Sep. 18, 2013EUR (€)€ / shares

Dec. 31, 2017

Dec. 15, 2017EUR (€)€ / shares

Dec. 05, 2017EUR (€)€ / shares

Dec. 31, 2016

Dec. 31, 2015

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

12/15/2027

12/05/2027

Number of options granted

8,300

625,200

Share entitlement per SO

€ 1

€ 1

Exercise price (in euros) | €

€ 38.18

€ 39

Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 36.43

€ 35.73

Expected volatility

43.13%

43.23%

Expected dividends

0.00%

0.00%

Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

1 year

Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

0

Discount rate

(0.23%)

(0.23%)

Fair value per SO (in euros)

€ 13.5

€ 12.9

Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

4 years

Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

0

Discount rate

0.07%

0.07%

Fair value per SO (in euros)

€ 15.4

€ 14.7

Share Option [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

998,500

359,060

315,000

Date of Grant One [Member] | Share Option [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

10 years

Date of Grant One [Member] | Share Option [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

Plan expiration date

06/21/2026

09/18/2023

Number of options granted

110,000

518,000

Share entitlement per SO

€ 1

€ 1

Exercise price (in euros) | €

€ 53.96

€ 7.57

Date of Grant One [Member] | Share Option [Member] | Board of Director [Member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 52.97

€ 7.90

Expected volatility

40.00%

Average life of SO (in years)

0

Discount rate

(0.01%)

1.72%

Expected dividends

0.00%

0.00%

Fair value per SO (in euros)

€ 3.57

Date of Grant One [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

4 years

Date of Grant One [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Expected volatility

49.10%

Average life of SO (in years)

0

0

Fair value per SO (in euros)

€ 23.4

Date of Grant One [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

Date of Grant One [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Expected volatility

50.30%

Average life of SO (in years)

0

0

Fair value per SO (in euros)

€ 25.5

Date of Grant Two [Member] | Share Option [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Plan expiration date

08/01/2026

06/03/2024

Number of options granted

10,000

75,000

Share entitlement per SO

€ 1

€ 1

Exercise price (in euros) | €

€ 62.24

€ 19.01

Date of Grant Two [Member] | Share Option [Member] | Board of Director [Member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 62.24

€ 19.01

Expected volatility

40.00%

Average life of SO (in years)

0

Discount rate

(0.25%)

0.89%

Expected dividends

0.00%

0.00%

Fair value per SO (in euros)

€ 7.46

Date of Grant Two [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

Date of Grant Two [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Expected volatility

48.80%

Average life of SO (in years)

0

0

Fair value per SO (in euros)

€ 27.3

Date of Grant Two [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

Date of Grant Two [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Expected volatility

49.80%

Average life of SO (in years)

0

0

Fair value per SO (in euros)

€ 29.9

Date of Grant Three [Member] | Share Option [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

09/15/2016

06/23/2025

Number of options granted

9,300

120,000

Share entitlement per SO

€ 1

€ 1

Exercise price (in euros) | €

€ 62.80

€ 48.90

Date of Grant Three [Member] | Share Option [Member] | Board of Director [Member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 62.80

€ 48.90

Expected volatility

51.00%

Average life of SO (in years)

0

Discount rate

(0.18%)

0.89%

Expected dividends

0.00%

0.00%

Fair value per SO (in euros)

€ 25.28

Date of Grant Three [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

1 year

Date of Grant Three [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Expected volatility

48.60%

Average life of SO (in years)

0

0

Fair value per SO (in euros)

€ 27.4

Date of Grant Three [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

4 years

Date of Grant Three [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Expected volatility

49.40%

Average life of SO (in years)

0

0

Fair value per SO (in euros)

€ 30.1

Date of Grant 06/21/2016 [Member] | Share Option [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

10/17/2026

11/19/2025

Number of options granted

16,500

195,000

Share entitlement per SO

€ 1

€ 1

Exercise price (in euros) | €

€ 64.39

€ 66.06

Date of Grant 06/21/2016 [Member] | Share Option [Member] | Board of Director [Member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 64.39

€ 66.06

Expected volatility

51.00%

Average life of SO (in years)

0

Discount rate

0.81%

Expected dividends

0.00%

0.00%

Fair value per SO (in euros)

€ 34.05

Date of Grant 06/21/2016 [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

1 year

Date of Grant 06/21/2016 [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Expected volatility

48.00%

Average life of SO (in years)

0

0

Discount rate

(0.32%)

Fair value per SO (in euros)

€ 27.6

Date of Grant 06/21/2016 [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

4 years

Date of Grant 06/21/2016 [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Expected volatility

48.90%

Average life of SO (in years)

0

0

Discount rate

(0.15%)

Fair value per SO (in euros)

€ 30.6

Date of Grant 06/09/2016 [Member] | Share Option [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

11/15/2026

01/04/2026

Number of options granted

8,300

75,000

Share entitlement per SO

€ 1

€ 1

Exercise price (in euros) | €

€ 68.33

€ 65.68

Date of Grant 06/09/2016 [Member] | Share Option [Member] | Board of Director [Member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 68.33

€ 65.68

Average life of SO (in years)

0

Discount rate

0.39%

Expected dividends

0.00%

0.00%

Date of Grant 06/09/2016 [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

1 year

Date of Grant 06/09/2016 [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Expected volatility

47.80%

49.30%

Average life of SO (in years)

0

0

Discount rate

(0.11%)

Fair value per SO (in euros)

€ 29.4

€ 29.5

Date of Grant 06/09/2016 [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

4 years

Date of Grant 06/09/2016 [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Expected volatility

48.80%

49.80%

Average life of SO (in years)

0

0

Discount rate

0.16%

Fair value per SO (in euros)

€ 32.7

€ 32.6

Date of Grant 06/15/2017 [Member] | Share Option [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

12/09/2026

04/21/2026

Number of options granted

74,960

33,000

Share entitlement per SO

€ 1

€ 1

Exercise price (in euros) | €

€ 69.75

€ 62.82

Date of Grant 06/15/2017 [Member] | Share Option [Member] | Board of Director [Member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 69.75

€ 62.82

Average life of SO (in years)

0

Discount rate

0.04%

Expected dividends

0.00%

0.00%

Date of Grant 06/15/2017 [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

1 year

Date of Grant 06/15/2017 [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Expected volatility

47.70%

49.40%

Average life of SO (in years)

0

0

Discount rate

(0.20%)

Fair value per SO (in euros)

€ 29.7

€ 28.3

Date of Grant 06/15/2017 [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

4 years

Date of Grant 06/15/2017 [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Expected volatility

48.50%

50.70%

Average life of SO (in years)

0

0

Discount rate

0.18%

Fair value per SO (in euros)

€ 33.4

€ 30.9

Grant Date Twelve [Member] | Share Option [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

12/15/2026

05/02/2026

Number of options granted

1,100

22,000

Share entitlement per SO

€ 1

€ 1

Exercise price (in euros) | €

€ 69.35

€ 59.04

Grant Date Twelve [Member] | Share Option [Member] | Board of Director [Member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 69.35

€ 58.62

Expected volatility

40.44%

Average life of SO (in years)

0

Discount rate

0.10%

Expected dividends

0.00%

0.00%

Grant Date Twelve [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

1 year

Grant Date Twelve [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Expected volatility

49.30%

Average life of SO (in years)

0

0

Discount rate

(0.18%)

Fair value per SO (in euros)

€ 25.2

€ 26.4

Grant Date Twelve [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

4 years

Grant Date Twelve [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Expected volatility

50.60%

Average life of SO (in years)

0

0

Discount rate

0.16%

Fair value per SO (in euros)

€ 28.7

€ 28.8

Date of Grant Seven [Member] | Share Option [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

10 years

10 years

10 years

Date of Grant Seven [Member] | Share Option [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

01/16/2027

Number of options granted

19,100

Share entitlement per SO

€ 1

Exercise price (in euros) | €

€ 66.11

Date of Grant Seven [Member] | Share Option [Member] | Board of Director [Member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 66.11

Expected volatility

40.21%

Expected dividends

0.00%

Date of Grant Seven [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

Date of Grant Seven [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

Discount rate

(0.17%)

Fair value per SO (in euros)

€ 23.9

Date of Grant Seven [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

Date of Grant Seven [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

Discount rate

0.19%

Fair value per SO (in euros)

€ 27.20

Grant date thirteen [member] | Share Option [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

03/15/2027

Number of options granted

7,200

Share entitlement per SO

€ 1

Exercise price (in euros) | €

€ 66.25

Grant date thirteen [member] | Share Option [Member] | Board of Director [Member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 65.42

Expected volatility

39.82%

Expected dividends

0.00%

Grant date thirteen [member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

Grant date thirteen [member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

Discount rate

0.21%

Fair value per SO (in euros)

€ 23.6

Grant date thirteen [member] | Share Option [Member] | Board of Director [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

Grant date thirteen [member] | Share Option [Member] | Board of Director [Member] | Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

Discount rate

0.61%

Fair value per SO (in euros)

€ 27.10

Date of Grant 06/24/2011 [Member] | Share Option [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

04/18/2027

Number of options granted

16,500

Share entitlement per SO

€ 1

Exercise price (in euros) | €

€ 60.77

Date of Grant 06/24/2011 [Member] | Share Option [Member] | Board of Director [Member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 59.73

Expected volatility

39.63%

Expected dividends

0.00%

Date of Grant 06/24/2011 [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

Date of Grant 06/24/2011 [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

Discount rate

0.02%

Fair value per SO (in euros)

€ 21.2

Date of Grant 06/24/2011 [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

Date of Grant 06/24/2011 [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

Discount rate

0.39%

Fair value per SO (in euros)

€ 24.20

Date of Grant 11/22/2011 [Member] | Share Option [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

06/15/2027

Number of options granted

126,000

Share entitlement per SO

€ 1

Exercise price (in euros) | €

€ 59.05

Date of Grant 11/22/2011 [Member] | Share Option [Member] | Board of Director [Member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 59.05

Expected volatility

39.23%

Expected dividends

0.00%

Date of Grant 11/22/2011 [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

Date of Grant 11/22/2011 [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

Discount rate

(0.21%)

Fair value per SO (in euros)

€ 20.8

Date of Grant 11/22/2011 [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

Date of Grant 11/22/2011 [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

Discount rate

0.07%

Fair value per SO (in euros)

€ 23.60

Grant Date Sixteen [Member] | Share Option [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

06/15/2027

Number of options granted

111.600

Share entitlement per SO

€ 1

Exercise price (in euros) | €

€ 60.54

Grant Date Sixteen [Member] | Share Option [Member] | Board of Director [Member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 59.05

Expected volatility

39.23%

Expected dividends

0.00%

Grant Date Sixteen [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

Grant Date Sixteen [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

Discount rate

(0.21%)

Fair value per SO (in euros)

€ 20.4

Grant Date Sixteen [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

Grant Date Sixteen [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

Discount rate

0.07%

Fair value per SO (in euros)

€ 232.22

Date of Grant Eight [Member] | Share Option [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

10 years

Date of Grant Eight [Member] | Share Option [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

07/17/2027

Number of options granted

30,900

Share entitlement per SO

€ 1

Exercise price (in euros) | €

€ 71.61

Date of Grant Eight [Member] | Share Option [Member] | Board of Director [Member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 71.61

Expected volatility

38.84%

Expected dividends

0.00%

Date of Grant Eight [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

Date of Grant Eight [Member] | Share Option [Member] | Board of Director [Member] | Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

Discount rate

0.01%

Fair value per SO (in euros)

€ 25.3

Date of Grant Eight [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

Date of Grant Eight [Member] | Share Option [Member] | Board of Director [Member] | Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

Discount rate

0.34%

Fair value per SO (in euros)

€ 28.20

Grant Date Seventeen Member | Share Option [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Plan expiration date

09/15/2027

Number of options granted

52,600

Share entitlement per SO

€ 1

Exercise price (in euros) | €

€ 74.22

Grant Date Seventeen Member | Share Option [Member] | Board of Director [Member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Grant date share fair value (in euros) | €

€ 71.80

Expected volatility

38.57%

Expected dividends

0.00%

Grant Date Seventeen Member | Share Option [Member] | Board of Director [Member] | Bottom of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

1 year

Grant Date Seventeen Member | Share Option [Member] | Board of Director [Member] | Bottom of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

Discount rate

(0.14%)

Fair value per SO (in euros)

€ 24.3

Grant Date Seventeen Member | Share Option [Member] | Board of Director [Member] | Top of range [member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

4 years

Grant Date Seventeen Member | Share Option [Member] | Board of Director [Member] | Top of range [member] | Black and Scholes Method [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Average life of SO (in years)

0

Discount rate

0.19%

Fair value per SO (in euros)

€ 27.80

Share-Based Payments - Discl117

Share-Based Payments - Disclosure of Change in Number of Share Options Outstanding (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 15, 2017	Dec. 05, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options granted		8,300	625,200
Share Option [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Balance at beginning of period	1,160,060			861,000	546,000
Number of options granted	998,500			359,060	315,000
Forfeited during the period	24,260			25,000
Exercised during the period	1,200			35,000
Expired during the period	0			0	0
Balance at end of period	2,133,100			1,160,060	861,000

Share-Based Payments - Discl118

Share-Based Payments - Disclosure of Details of Breakdown of the Closing Balance SO (Detail)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)	Dec. 31, 2015EUR (€)
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	181,008	147,359	143,694
Exercisable	181,008	147,359	53,859
Share Option [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	2,133,100	1,160,000	861,000
Exercisable	755,650	85,000
Share Option [Member] | Exercise Price of Euro 7.57 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	471,000	471,000	471,000
Exercisable	471,000
Exercise price, outstanding	€ 7.57	€ 7.57	€ 7.57
Exercise price, Exercisable	€ 7.57
Share Option [Member] | Exercise Price of Euro 19.01 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	40,000	40,000	75,000
Exercisable	40,000	40,000
Exercise price, outstanding	€ 19.01	€ 19.01	€ 19.01
Exercise price, Exercisable	€ 19.01	€ 19.01
Share Option [Member] | Exercise Price of Euro 48.90 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	120,000	120,000	120,000
Exercisable	75,000	45,000
Exercise price, outstanding	€ 48.90	€ 48.90	€ 48.90
Exercise price, Exercisable	€ 48.90	€ 48.90
Share Option [Member] | Exercise Price of Euro 66.06 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	170,000	170,000	195,000
Exercisable	85,000
Exercise price, outstanding	€ 66.06	€ 66.06	€ 66.06
Exercise price, Exercisable	€ 66.06
Share Option [Member] | Exercise Price of Euro 65.68 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	75,000	75,000
Exercisable	18,750
Exercise price, outstanding	€ 65.68	€ 65.68
Exercise price, Exercisable	€ 65.68
Share Option [Member] | Exercise Price of Euro 62.82 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	33,000	33,000
Exercisable	8,250
Exercise price, outstanding	€ 62.82	€ 62.82
Exercise price, Exercisable	€ 62.82
Share Option [Member] | Exercise Price of Euro 59.04 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	22,000	22,000
Exercisable	5,500
Exercise price, outstanding	€ 59.04	€ 59.04
Exercise price, Exercisable	€ 59.04
Share Option [Member] | Exercise Price of Euro 53.96 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	101,300	110,000
Exercisable	24,425
Exercise price, outstanding	€ 53.96	€ 53.96
Exercise price, Exercisable	€ 53.96
Share Option [Member] | Exercise Price of Euro 62.24 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	10,000	10,000
Exercisable	2,500
Exercise price, outstanding	€ 62.24	€ 62.24
Exercise price, Exercisable	€ 62.24
Share Option [Member] | Exercise Price of Euro 62.80 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	9,300	9,300
Exercisable	2,325
Exercise price, outstanding	€ 62.80	€ 62.80
Exercise price, Exercisable	€ 62.80
Share Option [Member] | Exercise Price of Euro 64.39 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	9,300	16,500
Exercisable	2,325
Exercise price, outstanding	€ 64.39	€ 64.39
Exercise price, Exercisable	€ 64.39
Share Option [Member] | Exercise Price of Euro 68.33 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	8,300	8,300
Exercisable	2,075
Exercise price, outstanding	€ 68.33	€ 68.33
Exercise price, Exercisable	€ 68.33
Share Option [Member] | Exercise Price of Euro 69.75 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	72,900	74,960
Exercisable	18,225
Exercise price, outstanding	€ 69.75	€ 69.75
Exercise price, Exercisable	€ 69.75
Share Option [Member] | Exercise price of Euro 66.35 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	1,100
Exercisable	275
Exercise price, outstanding	€ 66.35
Exercise price, Exercisable	€ 66.35
Share Option [Member] | Exercise price of Euro 66.11 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	19,100
Exercise price, outstanding	€ 66.11
Share Option [Member] | Exercise price of Euro 66.25 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	7,200
Exercise price, outstanding	€ 66.25
Share Option [Member] | Exercise price of Euro 60.77 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	16,500
Exercise price, outstanding	€ 60.77
Share Option [Member] | Exercise price of Euro 59.05 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	118,500
Exercise price, outstanding	€ 59.05
Share Option [Member] | Exercise price of Euro 60.54 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	111,600
Exercise price, outstanding	€ 60.54
Share Option [Member] | Exercise price of Euro 71.61 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	30,900
Exercise price, outstanding	€ 71.61
Share Option [Member] | Exercise price of Euro 74.22 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	52,600
Exercise price, outstanding	€ 74.22
Share Option [Member] | Exercise price of Euro 39.00 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	625,200
Exercise price, outstanding	€ 39
Share Option [Member] | Exercise price of Euro 38.18 [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding	8,300
Exercise price, outstanding	€ 38.18

Disclosure - Share-Based Paymen

Disclosure - Share-Based Payments - Summary of Details of Share Based Payment Arrangement Free Shares (Detail)

Apr. 20, 2017€ / shares

Mar. 14, 2017€ / shares

Dec. 09, 2016EUR (€)€ / shares

Oct. 27, 2016EUR (€)€ / shares

Sep. 01, 2016EUR (€)€ / shares

Aug. 16, 2016EUR (€)€ / shares

Jun. 21, 2016EUR (€)€ / shares

Apr. 06, 2016EUR (€)€ / shares

Dec. 15, 2015EUR (€)€ / shares

Sep. 30, 2015EUR (€)€ / shares

Jun. 03, 2014EUR (€)€ / shares

Sep. 12, 2013EUR (€)€ / shares

Nov. 28, 2012EUR (€)€ / shares

Jul. 25, 2012EUR (€)€ / shares

Apr. 02, 2012EUR (€)€ / shares

Dec. 31, 2017

Dec. 15, 2017€ / shares

Dec. 05, 2017€ / shares

Dec. 31, 2016

Dec. 31, 2015

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

8,300

625,200

Share entitlement per free share

€ 1

€ 1

Free Share [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Number of options granted

46,500

310,350

750,500

Date of Grant One [Member] | Free Share [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Number of options granted

669,796

Share entitlement per free share

€ 1

Grant date share fair value (in euros) | €

€ 8.86

Expected dividends

0.00%

Performance conditions

Yes

Expected turnover during the vesting period

1.00%

Date of Grant Two [Member] | Free Share [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Number of options granted

134,081

Share entitlement per free share

€ 1

Grant date share fair value (in euros) | €

€ 8.20

Expected dividends

0.00%

Performance conditions

Yes

Expected turnover during the vesting period

1.00%

Date of Grant Three [Member] | Free Share [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Number of options granted

35,360

Share entitlement per free share

€ 1

Grant date share fair value (in euros) | €

€ 8.70

Expected dividends

0.00%

Performance conditions

No

Expected turnover during the vesting period

1.00%

Date of Grant Four [Member] | Free Share [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Number of options granted

501,500

Share entitlement per free share

€ 1

Grant date share fair value (in euros) | €

€ 7.96

Expected dividends

0.00%

Performance conditions

Yes

Expected turnover during the vesting period

1.00%

Date of Grant Five [Member] | Free Share [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Number of options granted

186,000

Share entitlement per free share

€ 1

Grant date share fair value (in euros) | €

€ 19.01

Expected dividends

0.00%

Performance conditions

Yes

Expected turnover during the vesting period

1.00%

Date of Grant 03/24/2015 [Member] | Free Share [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

2 years

Number of options granted

708,500

Share entitlement per free share

€ 1

Grant date share fair value (in euros) | €

€ 62.99

Expected dividends

0.00%

Performance conditions

yes

Yes

Expected turnover during the vesting period

0.00%

Number of free shares granted

22,500

Share entitlement per free share

€ 1

Grant date share fair value (in euros)

€ 68.07

Expected dividends

0.00%

Expected turnover during the vesting period

0.00%

Date of Grant Seven [Member] | Free Share [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

2 years

Number of options granted

42,000

Share entitlement per free share

€ 1

Grant date share fair value (in euros) | €

€ 64.14

Expected dividends

0.00%

Performance conditions

yes

Yes

Expected turnover during the vesting period

0.00%

Number of free shares granted

24,000

Share entitlement per free share

€ 1

Grant date share fair value (in euros)

€ 61.20

Expected dividends

0.00%

Expected turnover during the vesting period

0.00%

Date of Grant Eight [Member] | Free Share [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Number of options granted

63,750

Share entitlement per free share

€ 1

Grant date share fair value (in euros) | €

€ 62.40

Expected dividends

0.00%

Performance conditions

yes

Expected turnover during the vesting period

0.00%

Date of Grant 06/21/2016 [Member] | Free Share [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Number of options granted

193,000

Share entitlement per free share

€ 1

Grant date share fair value (in euros) | €

€ 52.97

Expected dividends

0.00%

Performance conditions

yes

Expected turnover during the vesting period

0.00%

Date of Grant 06/09/2016 [Member] | Free Share [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Number of options granted

10,000

Share entitlement per free share

€ 1

Grant date share fair value (in euros) | €

€ 60.68

Expected dividends

0.00%

Performance conditions

yes

Expected turnover during the vesting period

0.00%

Date of Grant 06/15/2017 [Member] | Free Share [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Number of options granted

5,000

Share entitlement per free share

€ 1

Grant date share fair value (in euros) | €

€ 61.49

Expected dividends

0.00%

Performance conditions

yes

Expected turnover during the vesting period

0.00%

Grant Date Twelve [Member] | Free Share [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Number of options granted

15,000

Share entitlement per free share

€ 1

Grant date share fair value (in euros) | €

€ 67.44

Expected dividends

0.00%

Performance conditions

yes

Expected turnover during the vesting period

0.00%

Grant date thirteen [member] | Free Share [Member] | Board of Director [Member]

Disclosure of terms and conditions of share-based payment arrangement [line items]

Vesting period (years)

2 years

Number of options granted

23,600

Share entitlement per free share

€ 1

Grant date share fair value (in euros) | €

€ 69.75

Expected dividends

0.00%

Performance conditions

yes

Expected turnover during the vesting period

0.00%

Disclosure - Share-Based Pay120

Disclosure - Share-Based Payments - Summary of Details of Share Based Payment Arrangement Free Shares (Parenthetical) (Detail) - Free Share [Member]	12 Months Ended
	Dec. 31, 2017
Grant Date One And Two [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of free shares upon achievement of performance criteria, description	The acquisition of free shares is contingent for certain individuals (the "Key Managers"), including Dr. Benhamou, upon the achievement of the three performance criteria
Grant date eight, nine, ten and eleven [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of free shares upon achievement of performance criteria, description	The acquisition of free shares is contingent for all the employees, including Dr. Benhamou, upon the achievement of the three performance criteria

Share-Based Payments - Summa121

Share-Based Payments - Summary of Details of Free Shares (Parenthetical) (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 15, 2017	Dec. 05, 2017
Top of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)		4 years	4 years
Bottom of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)		1 year	1 year
Viaskin Peanut [Member] | Top of range [member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of shares on achievement of performance criteria	Half of the shares
Vesting period (years)	2 years
Grant date twelve and thirteen [member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of free shares upon achievement of performance criteria, description	The acquisition of free shares is contingent for key and new employees upon the achievement of the two performance criteria
Grant date twelve and thirteen [member] | Viaskin Milk [member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of shares on achievement of performance criteria	Half
Vesting period (years)	2 years
Grant date twelve and thirteen [member] | Viaskin Peanut [member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of shares on achievement of performance criteria	Half
Vesting period (years)	2 years
Grant date eight, nine, ten and eleven [member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of shares on achievement of performance criteria	One third
Vesting period (years)	2 years
Acquisition of free shares upon achievement of performance criteria, description	The acquisition of free shares is contingent for all the employees, including Dr. Benhamou, upon the achievement of the three performance criteria
Date of Grant 03/24/2015 [Member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of free shares upon achievement of performance criteria, description	The acquisition of free shares is contingent for all the employees, including Dr. Benhamou, upon the achievement of the three performance criteria
Date of Grant 03/24/2015 [Member] | Viaskin Platform [Member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of shares on achievement of performance criteria	One third of the shares
Vesting period (years)	2 years
Date of Grant 03/24/2015 [Member] | Phase II Miles Trial For Viaskin Milk [Member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of shares on achievement of performance criteria	One third of the shares
Vesting period (years)	2 years
Date of Grant 03/24/2015 [Member] | Phase I I I Pepites Trial For Viaskin Peanut [Member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of shares on achievement of performance criteria	One third of the shares
Vesting period (years)	2 years
Date of Grant Five [Member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of free shares upon achievement of performance criteria, description	The acquisition of free shares is contingent for the Key Managers, including Dr. Benhamou, upon the achievement of the two performance criteria
Date of Grant Five [Member] | Viaskin Peanut [Member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of shares on achievement of performance criteria	Half of the shares
Vesting period (years)	2 years
Date of Grant Four [Member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of free shares upon achievement of performance criteria, description	The acquisition of free shares is contingent for the Key Managers, including Dr. Benhamou, upon the achievement of the three performance criteria
Date of Grant Four [Member] | Adoption Of 2013 Free Share Allocation Plan [Member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of shares on achievement of performance criteria	One-third of the shares
Vesting period (years)	2 years
Number of consecutive days	5
Date of Grant Four [Member] | Adoption Of 2013 Free Share Allocation Plan [Member] | Bottom of range [member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Percentage increase in share price	50.00%
Date of Grant Four [Member] | Inclusion Of 100th Patient In VIPES Phase II Study [Member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of shares on achievement of performance criteria	One-third of the shares
Vesting period (years)	2 years
Grant Date One And Two [Member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of free shares upon achievement of performance criteria, description	The acquisition of free shares is contingent for certain individuals (the "Key Managers"), including Dr. Benhamou, upon the achievement of the three performance criteria
Grant Date One And Two [Member] | On achievement of phase three Pepites trial for Viaskin Peanut [Member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of shares on achievement of performance criteria	One-third of the shares
Vesting period (years)	2 years
Grant Date One And Two [Member] | Inclusion Of 100th Patient In VIPES Phase II Study [Member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of shares on achievement of performance criteria	One-third of the shares
Vesting period (years)	2 years
Grant Date One And Two [Member] | Inclusion Of First Patient In Viaskin Milk Phase II Study [Member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of shares on achievement of performance criteria	One-third of the shares
Vesting period (years)	2 years
Grant Date One And Two [Member] | Achievement Of Principal Evaluation Criterion In VIPES Phase II Study [Member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of shares on achievement of performance criteria	One-third of the shares
Vesting period (years)	2 years
Grant Date Fourteen And Fifteen [member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Acquisition of free shares upon achievement of performance criteria, description	The acquisition of free shares is contingent for key and new employees upon the achievement of the two performance criteria
Grant Date Fourteen And Fifteen [member] | Viaskin Milk [member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	2 years
Acquisition of shares on achievement of performance criteria	0
Grant Date Fourteen And Fifteen [member] | Viaskin Peanut [member] | Free Share [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period (years)	2 years
Acquisition of shares on achievement of performance criteria	0

Share-Based Payments - Change i

Share-Based Payments - Change in Number of Free Shares Outstanding (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 15, 2017	Dec. 05, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes In Number Of Shares Outstanding [line items]
Granted during the period		8,300	625,200
Free Share [Member]
Changes In Number Of Shares Outstanding [line items]
Balance at beginning of period	1,036,850			1,008,329	641,360
Granted during the period	46,500			310,350	750,500
Forfeited during the period	18,650			24,000	61,833
Exercised during the period	241,844			257,829	321,698
Expired during the period	0			0	0
Balance at end of period	822,856			1,036,850	1,008,329

Financial Revenue and Expens123

Financial Revenue and Expenses - Summary of Financial Income and Expenses (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Detail Information About Financial Income And Expenses [line items]
Financial revenues	€ 616	€ 1,516	€ 1,018
Financial expenses	(3,325)	(16)	(146)
Total	€ (2,709)	1,500	€ 871
Scenario, Previously Reported [Member]
Disclosure Of Detail Information About Financial Income And Expenses [line items]
Financial revenues		1,646
Financial expenses		€ (145)

Income Tax Expense - Additional

Income Tax Expense - Additional Information (Detail) - 12 months ended Dec. 31, 2017 € in Millions	EUR (€)	USD ($)
Disclosure of reconciliation of effective and applicable income tax expenses [line items]
Deferred tax assets | $		$ 0
Amount of losses carried forward	€ 369
Parent [member]
Disclosure of reconciliation of effective and applicable income tax expenses [line items]
Amount of losses carried forward	€ 334
French (Member)
Disclosure of reconciliation of effective and applicable income tax expenses [line items]
Effective income tax rate	33.33%

Income Tax Expense - Summary of

Income Tax Expense - Summary of Reconciliation of Effective and Nominal Tax Expense (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Major components of tax expense (income) [abstract]
(Loss) before taxes	€ (147,692)	€ (114,531)	€ (44,674)
Theoretical group tax rate	33.33%	33.33%	33.33%
Nominal tax expense	€ 49,226	€ 38,173	€ 14,890
Permanent differences			6,089
Research tax credit	3,110	2,409	1,895
Share-based compensation	(10,260)	(11,451)	(3,473)
Non recognition of deferred tax assets related to tax losses and temporary differences	(41,453)	(29,195)	(19,211)
Other differences	622	64	€ 190
Effective tax expense	€ 1	€ 0
Effective tax rate	0.00%	0.00%	0.00%

Commitments - Additional Inform

Commitments - Additional Information (Detail) € in Thousands, $ in Thousands	1 Months Ended		12 Months Ended
	Nov. 30, 2017ft²	Jun. 30, 2017ft²	Dec. 31, 2017EUR (€)ft²m²Facilities	Dec. 31, 2017USD ($)Facilities	May 31, 2017USD ($)	Apr. 30, 2016USD ($)
Disclosure of commitments [line items]
Future rental payments			€ 14,991
Other agreements [member] | Contract Research Organizations [Member] | Viaskin Peanuts And Viaskin Milk Products [member]
Disclosure of commitments [line items]
Launching value of clinical studies			78,700
Remaining value of clinical studies			32,600
Monetary market fund [member] | Other agreements [member]
Disclosure of commitments [line items]
Sum of term deposit			€ 227
Term deposit period			3 years
Property, plant and equipment subject to operating leases [member] | Letter of credit 1 [member] | Other agreements [member]
Disclosure of commitments [line items]
Future rental payments | $				$ 164	$ 300	$ 143
Not Later Than One Year [member]
Disclosure of commitments [line items]
Future rental payments			€ 2,617
Later Than One Year and Not Later Than Two Years [member]
Disclosure of commitments [line items]
Future rental payments			2,623
Later Than Two Years and Not Later Than Three Years [member]
Disclosure of commitments [line items]
Future rental payments			2,357
Later Than Three Years and Not Later Than Four Years [member]
Disclosure of commitments [line items]
Future rental payments			2,169
Office equipment and vehicles [member] | Not Later Than One Year [member]
Disclosure of commitments [line items]
Future rental payments			116
Office equipment and vehicles [member] | Later Than One Year and Not Later Than Two Years [member]
Disclosure of commitments [line items]
Future rental payments			77
Office equipment and vehicles [member] | Later Than Two Years and Not Later Than Three Years [member]
Disclosure of commitments [line items]
Future rental payments			70
Office equipment and vehicles [member] | Later Than Three Years and Not Later Than Four Years [member]
Disclosure of commitments [line items]
Future rental payments			€ 16
North america [member] | Rental agreements [member]
Disclosure of commitments [line items]
Area of office and laboratory space | ft²	3,780	3,913
Subleases expiration period			Jun. 30, 2017
Additional initial Period of sublease			5 years
Bagneux [member] | Monetary market fund [member] | Other agreements [member]
Disclosure of commitments [line items]
Guarantee for ordinary rental agreements of the premises			€ 300
Facility [member] | Rental agreements [member]
Disclosure of commitments [line items]
Office and laboratory space | m²			4,770
Number of facilities | Facilities			2	2
Lease agreement date			Mar. 9, 2015
Leases expires period			Mar. 8, 2024
Second Facility [member] | Rental agreements [member]
Disclosure of commitments [line items]
Office and laboratory space | m²			2,237
Leases expires period			May 31, 2020
Commercial Facility [member] | Bottom of range [member]
Disclosure of commitments [line items]
Lease extension period			2 years
Commercial Facility [member] | Top of range [member]
Disclosure of commitments [line items]
Lease extension period			5 years
Commercial Facility [member] | Rental agreements [member]
Disclosure of commitments [line items]
Office and laboratory space | ft²			8,919
Lease commenced period			Eight years and four months.

Commitments - Schedule of Futur

Commitments - Schedule of Future Rents and Charges (Detail) € in Thousands	Dec. 31, 2017EUR (€)
Disclosure of finance lease and operating lease by lessee [line items]
Amount of future rents and charges	€ 14,991
Not Later Than One Year [member]
Disclosure of finance lease and operating lease by lessee [line items]
Amount of future rents and charges	2,617
Later Than One Year and Not Later Than Two Years [member]
Disclosure of finance lease and operating lease by lessee [line items]
Amount of future rents and charges	2,623
Later Than Two Years and Not Later Than Three Years [member]
Disclosure of finance lease and operating lease by lessee [line items]
Amount of future rents and charges	2,357
Later Than Three Years and Not Later Than Four Years [member]
Disclosure of finance lease and operating lease by lessee [line items]
Amount of future rents and charges	2,169
Later Than Four Years and Not Later Than Five Years [member]
Disclosure of finance lease and operating lease by lessee [line items]
Amount of future rents and charges	2,119
Later than five years and not later than six years [member]
Disclosure of finance lease and operating lease by lessee [line items]
Amount of future rents and charges	1,847
2023 [member]
Disclosure of finance lease and operating lease by lessee [line items]
Amount of future rents and charges	€ 1,258

Relationships with Related P128

Relationships with Related Parties - Additional Information (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of transactions between related parties [line items]
Compensation awarded to board of directors and executive committee	€ 15,353	€ 16,891	€ 7,205
Commercial strategy consulting works [member]
Disclosure of transactions between related parties [line items]
Compensation awarded to board of directors and executive committee	€ 45

Relationships with Related P129

Relationships with Related Parties - Summary of Relationships with Related Parties (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of transactions between related parties [line items]
Related party compensation	€ 15,353	€ 16,891	€ 7,205
Executive Committee [member]
Disclosure of transactions between related parties [line items]
Related party compensation	2,184	2,268	1,768
Members of the Board of Directors [member]
Disclosure of transactions between related parties [line items]
Related party compensation	745	714	605
Share-based payments to members of the Board of Directors	12,018	13,714	4,637
Directors Fees [member]
Disclosure of transactions between related parties [line items]
Related party compensation	€ 407	€ 195	€ 195

Relationships with Related P130

Relationships with Related Parties - Schedule of Amounts Payable to Related Parties (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of amount payables to related parties [Line Items]
Amounts Payable	€ 1,523	€ 1,304	€ 1,102
Directors Fees [member]
Disclosure of amount payables to related parties [Line Items]
Amounts Payable	432	195	195
Compensation [member]
Disclosure of amount payables to related parties [Line Items]
Amounts Payable	689	767	674
Pension obligation [member]
Disclosure of amount payables to related parties [Line Items]
Amounts Payable	€ 402	€ 342	€ 233

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings per share [line items]
Description of types of warranties	Multiplying it by 15
Anti-dilutive instruments	3,309,539	2,360,945	2,033,768
Common Shares [member]
Earnings per share [line items]
Weighted average number of shares outstanding	24,757,176	24,454,850	21,522,342

Earnings Per Share - Summary of

Earnings Per Share - Summary of Earnings Per Share (Detail) - EUR (€) € / shares in Units, € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings per share [abstract]
Net income of the reporting period	€ (147,693)	€ (114,531)	€ (44,674)
Adjusted weighted average number of outstanding shares	24,757,176	24,454,850	21,522,342
Basic / Diluted earnings per share (€/share)	€ (5.97)	€ (4.68)	€ (2.08)

Management of Financial Risks -

Management of Financial Risks - Additional Information (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure Of Financial Risk Management [line items]
Cash and cash equivalents	€ 137,880	€ 256,473	€ 323,381	€ 114,555
Operating losses and cash out flows from operation	(147,693)	(114,531)	(44,674)
Accumulated deficit and reserves	(279,300)
Net cash used in operating activities	€ (114,314)	€ (59,538)	€ (26,763)
Top of range [member]
Disclosure Of Financial Risk Management [line items]
Percentage of purchases and other external expenses made in U.S. dollars	12.00%	12.00%	12.00%

Events After the Close of th134

Events After the Close of the Fiscal Year - Additional Information (Detail) € in Thousands	Feb. 14, 2018	Mar. 31, 2018EUR (€)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)	Dec. 31, 2015EUR (€)
Disclosure of non-adjusting events after reporting period [line items]
Share-based compensation expense corresponding to the acceleration of the vesting period			€ 30,781	€ 34,353	€ 10,419
Accelerated vesting period [member] | Scenario, Forecast [member]
Disclosure of non-adjusting events after reporting period [line items]
Share-based compensation expense corresponding to the acceleration of the vesting period		€ 5,400
Bottom of range [member] | Events after reporting period [member]
Disclosure of non-adjusting events after reporting period [line items]
Peanut allergy treatment covering age as per BLA	4
Top of range [member] | Events after reporting period [member]
Disclosure of non-adjusting events after reporting period [line items]
Peanut allergy treatment covering age as per BLA	11