argenx SE (ARGX) 20-F 26 Mar 18 2017 FY Annual report (foreign) Financial data

Document and Entity Information

Document and Entity Information	12 Months Ended
	Dec. 31, 2017shares
Document and Entity Information [Abstract]
Entity Registrant Name	ARGENX SE
Entity Central Index Key	1,697,862
Document Type	20-F
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding	32,180,641
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY

CONSOLIDATED STATEMENT OF FINAN

CONSOLIDATED STATEMENT OF FINANCIAL POSITION - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current assets
Cash and cash equivalents	€ 190,867	€ 89,897	€ 35,514
Restricted cash	1,692	786
Research and development incentive receivables	158	163
Financial assets	168,907	6,831	6,813
Prepaid expenses	2,338	2,146	454
Trade and other receivables	2,842	1,970	1,356
Total current assets	366,804	101,793	44,137
Non‑current assets
Restricted cash	256	1,149
Research and development incentive receivables	3,033	2,046	1,568
Other non-current assets	125
Financial assets	1	1	1
Property, plant and equipment	676	766	249
Intangible assets	13	17	7
Total non-current assets	4,104	3,979	1,825
TOTAL ASSETS	370,908	105,772	45,962
Equity
Share capital	3,217	2,012	1,580
Share premium	430,518	126,358	82,169
Accumulated losses	(100,568)	(72,492)	(51,118)
Other reserves	11,764	7,496	4,647
Total equity	344,931	63,374	37,278
Non-current liabilities	25	1
Provisions for employee benefits	25	1
Current liabilities	25,952	42,397	8,684
Trade and other payables	15,285	12,191	4,543
Current tax liabilities	597
Deferred revenue	10,070	30,206	4,141
Total liabilities	25,977	42,398	8,684
TOTAL EQUITY AND LIABILITIES	€ 370,908	€ 105,772	€ 45,962

CONSOLIDATED STATEMENT OF PROFI

CONSOLIDATED STATEMENT OF PROFIT AND LOSS AND OTHER COMPREHENSIVE INCOME - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CONSOLIDATED STATEMENT OF PROFIT AND LOSS AND OTHER COMPREHENSIVE INCOME
Revenue	€ 36,415	€ 14,713	€ 6,854
Other operating income	4,841	2,439	3,101
Total operating income	41,256	17,152	9,955
Research and development expenses	(51,740)	(31,557)	(20,635)
Selling, general and administrative expenses	(12,448)	(7,011)	(4,925)
Operating loss	(22,932)	(21,416)	(15,605)
Financial income	1,250	73	112
Exchange gains/(losses)	(5,797)	(31)	181
Loss before taxes	(27,479)	(21,374)	(15,312)
Income tax expense	(597)
Loss for the year and total comprehensive loss	€ (28,076)	€ (21,374)	€ (15,312)
Weighted average number of shares outstanding	24,609,536	18,820,612	15,734,007
Basic and diluted loss per share (in €)	€ (1.14)	€ (1.14)	€ (0.97)

CONSOLIDATED STATEMENT OF CASH

CONSOLIDATED STATEMENT OF CASH FLOWS - EUR (€) € in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS (USED IN) / FROM OPERATING ACTIVITIES
Operating result		€ (22,932)	€ (21,416)	€ (15,605)
Adjustments for non-cash items
Amortization of intangible assets		10	11	5
Depreciation of property, plant and equipment		425	323	191
Loss on disposal of fixed assets		11
Provisions for employee benefits		24	1
Expense recognized in respect of share‑based payments		4,268	2,849	2,270
Adjustments for non-cash items		(18,195)	(18,232)	(13,139)
Movements in current assets/liabilities
(Increase)/decrease in trade and other receivables		(122)	(614)	(651)
(Increase)/decrease in other current assets		(1,093)	(2,641)	(362)
Increase/(decrease) in trade and other payables		3,094	7,648	(434)
Increase/(decrease) in deferred revenue		(20,136)	26,065	689
Increase)/decrease in other non‑current assets		(94)	(1,627)
NET CASH FLOWS (USED IN) / FROM OPERATING ACTIVITIES		(36,546)	10,599	(13,897)
CASH FLOWS (USED IN) / FROM INVESTING ACTIVITIES
Purchase of intangible assets		(6)	(21)	(5)
Purchase of property, plant and equipment		(345)	(840)	(274)
(Increase)/decrease in current financial assets		(162,076)	(18)	16,979
Interest received		375	73	112
NET CASH FLOWS (USED IN) / FROM INVESTING ACTIVITIES		(162,052)	(806)	16,812
CASH FLOWS (USED IN) / FROM FINANCING ACTIVITIES
Proceeds from issue of shares	[1]	305,365	44,621	238
NET CASH FLOWS (USED IN) / FROM FINANCING ACTIVITIES		305,365	44,621	238
NET INCREASE (DECREASE) IN CASH & CASH EQUIVALENTS		106,767	54,414	3,153
Cash and cash equivalents at the beginning of the period		89,897	35,514	32,180
Exchange gains/(losses) on cash & cash equivalents		(5,797)	(31)	181
Cash and cash equivalents at the end of the period		€ 190,867	€ 89,897	€ 35,514
[1]	The gross cash flow from the issue of shares amounts to €308.7 million. The Company paid €3.4 million with respect to issuance costs.

CONSOLIDATED STATEMENT OF CASH5

CONSOLIDATED STATEMENT OF CASH FLOWS (Parenthetical) € in Millions	12 Months Ended
	Dec. 31, 2017EUR (€)
CONSOLIDATED STATEMENT OF CASH FLOWS
Proceeds from issue of shares	€ 308.7
Payments for share issue costs	€ 3.4

CONSOLIDATED STATEMENT OF CHANG

CONSOLIDATED STATEMENT OF CHANGES IN EQUITY - EUR (€) € in Thousands	Share capital	Share premium	Accumulated losses	Other reserves Equity-settled share-based payment reserve	Total equity attributable to owners of the parent	Total
Equity at beginning of period at Dec. 31, 2014	€ 1,571	€ 81,940	€ (35,806)	€ 2,377	€ 50,082	€ 50,082
Total comprehensive loss of the period			(15,312)		(15,312)	(15,312)
Issue of share capital	9	229			238	238
Share-based payment				2,270	2,270	2,270
Equity at end of period at Dec. 31, 2015	1,580	82,169	(51,118)	4,647	37,278	37,278
Total comprehensive loss of the period			(21,374)		(21,374)	(21,374)
Issue of share capital	432	46,038			46,470	46,470
Transaction costs for equity issue		(1,849)			(1,849)	(1,849)
Share-based payment				2,849	2,849	2,849
Equity at end of period at Dec. 31, 2016	2,012	126,358	(72,492)	7,496	63,374	63,374
Total comprehensive loss of the period			(28,076)		(28,076)	(28,076)
Issue of share capital	1,205	327,175			328,380	328,380
Transaction costs for equity issue		(23,015)			(23,015)	(23,015)
Share-based payment				4,268	4,268	4,268
Equity at end of period at Dec. 31, 2017	€ 3,217	€ 430,518	€ (100,568)	€ 11,764	€ 344,931	€ 344,931

General information about the c

General information about the company	12 Months Ended
	Dec. 31, 2017
General information about the company
General information about the company	1. General information about the company argenx SE (the Company) is a Dutch European public company with limited liability incorporated under the laws of the Netherlands. The Company (COC 24435214) has its official seat in Rotterdam, the Netherlands, and its registered office is at Willemstraat 5, 4811 AH, Breda, the Netherlands. An overview of the Company and its subsidiaries (the Group) are described in note 7.5. argenx SE is a publicly traded company with ordinary shares listed on Euronext Brussels under the symbol “ARGX” since July 2014 and with American Depositary Shares listed on Nasdaq under the symbol “ARGX” since May 2017.

Significant accounting policies

Significant accounting policies	12 Months Ended
	Dec. 31, 2017
Significant accounting policies
Significant accounting policies	2. Significant accounting policies The principal Group accounting policies are summarized below. 2.1 Statement of compliance and basis of preparation The consolidated financial statements are prepared in accordance with the International Financial Reporting Standards (IFRS), issued by the International Accounting Standards Board (IASB) and the interpretations issued by the IASB’s International Financial Reporting Interpretation Committee. The consolidated financial statements provide a general overview of the Group’s activities and the results achieved. They present fairly the entity’s financial position, its financial performance and cash flows, on a going concern basis. The accounting policies described in Note 2 to our consolidated financial statements have been applied in preparing the consolidated financial statements as of and for the year ended December 31, 2017 and for the comparative information as of and for the years ended December 31, 2016 and 2015. The preparation of consolidated financial statements in conformity with IFRS, issued by the IASB, requires the use of certain critical accounting estimates. It also requires management to exercise its judgment in the process of applying the Group’s accounting policies. The areas involving a higher degree of judgment or complexity, or areas where assumptions and estimates are significant to the consolidated financial statements are disclosed in Note 3. The principal accounting policies applied in the preparation of the above financial statements are set out below. All amounts are presented in thousands of euro, unless otherwise indicated, rounded to the nearest € ‘000. The consolidated financial statements have been approved for issue by the Company’s Board of Directors (the Board) on February 27, 2018. 2.2 Basis of consolidation The consolidated financial statements include the financial statements of the Company and entities controlled by the Company (its subsidiaries). Control is achieved when the Company: • has power over the investee; • is exposed, or has rights, to variable returns from its involvement with the investee; and • has the ability to use its power to affect its returns. The Company reassesses whether or not it controls an investee if facts and circumstances indicate that there are changes to one or more of the three elements of control listed above. Consolidation of a subsidiary begins when the Company obtains control over the subsidiary and ceases when the Company loses control of thesubsidiary. Income and expenses of subsidiaries acquired or disposed of during the year are included in the consolidated statement of profit and loss and other comprehensive income from the effective date of acquisition and up to the effective date of disposal, as appropriate. Total comprehensive income of subsidiaries is attributed to the owners of the Company and to the non‑controlling interests even if this results in the non‑controlling interests having a deficit balance. When necessary, adjustments are made to the financial statements of subsidiaries to bring their accounting policies into line with those used by other members of the Group. All intra‑group transactions, balances, income and expenses are eliminated in full on consolidation. 2.3 Foreign currency transactions Functional and presentation currency The financial statements are presented in euro (€), which is the Group’s presentation currency and the Company’s functional currency. Transactions and balances Transactions in foreign currencies are translated at the exchange rate ruling at the date of the transaction. Monetary assets and liabilities denominated in foreign currencies are translated at the exchange rate ruling at the reporting date. Foreign exchange differences arising on translation are recognized in the statement of profit and loss and other comprehensive income. Non‑monetary assets and liabilities denominated in foreign currencies are translated at the foreign exchange rate ruling at the date of the transaction. Financial statements of foreign entities For foreign entities using a different functional currency than the euro: · Non-monetary assets and liabilities are converted to the euro at the historical exchange rate at the date of the transaction. · Monetary assets and liabilities are converted to the euro using the exchange rate on the reporting date. · Income statements are converted to the euro at the annual average exchange rate. · Equity items are converted to the euro at the historical exchange rate for the date of the transaction. Translation differences resulting from the conversion of equity into euro using the rate at the end of the reporting period are recognized as translation differences under equity. Translation differences remain in equity up to the disposal of the company. In case of disposal, the deferred cumulative amount included in equity is included in the results for the foreign activity in question. 2.4 Intangible assets Intangible assets with finite useful lives that are acquired separately are carried at cost less accumulated amortization and accumulated impairment losses. Amortization is recognized on a straight‑line basis over their estimated useful lives. The estimated useful life and amortization method are reviewed at the end of each reporting period, with the effect of any changes in estimate being accounted for on a prospective basis. Intangible assets with indefinite useful lives that are acquired separately are carried at cost less accumulated impairment losses. Intangible assets related to software are amortized over 3 years. Expenditure on research activities is recognized as an expense in the period in which it is incurred. An internally‑generated intangible asset arising from development (or from the development phase of an internal project) is recognized if, and only if, all of the following have been demonstrated: · the technical feasibility of completing the intangible asset so that it will be available for use or sale; · the intention to complete the intangible asset and use or sell it; · the ability to use or sell the intangible asset; · how the intangible asset will generate probable future economic benefits; · the availability of adequate technical, financial and other resources to complete the development and to use or sell the intangible asset; and · the ability to measure reliably the expenditure attributable to the intangible asset during its development. The amount initially recognized for internally‑generated intangible assets is the sum of the expenditure incurred from the date when the intangible asset first meets the recognition criteria listed above. Where no internally‑generated intangible asset can be recognized, development expenditures are recognized in the statement of profit and loss and other comprehensive income in the period in which they are incurred. Due to uncertainties inherent to the development and registration with the relevant healthcare authorities of its products, the Company estimates that the conditions for capitalization are not met until the regulatory procedures required by such healthcare authorities have been finalized. The Company currently does not own products that have been approved by the relevant healthcare authorities. As such, research expenditures not satisfying the above criteria and expenditures in the research phase of internal projects are recognized in the statement of profit and loss and other comprehensive income as they are incurred. Subsequent to initial recognition, internally‑generated intangible assets are reported at cost less accumulated amortization and accumulated impairment losses, on the same basis as intangible assets that are acquired separately. An intangible asset is derecognized either on disposal or when no future economic benefits are expected from its use. Gains or losses arising from derecognition of an intangible asset, measured as the difference between the net disposal proceeds and the carrying amount of the asset, are recognized in profit or loss when the asset is derecognized. 2.5 Property, plant and equipment Items of property, plant and equipment held for use in the production or supply of goods or services, or for administrative purposes, are stated in the statement of financial position at their cost, less accumulated depreciation and accumulated impairment losses. The cost comprises the initial purchase price plus other direct purchase costs (such as non‑refundable tax and transport). Depreciation is recognized as from acquisition date onwards (unless asset is not ready for use) so as to write off the cost or valuation of assets (other than freehold land and properties under construction) less their residual values over their useful lives, using the straight‑line method. The estimated useful lives, residual values and depreciation method are reviewed at the end of each reporting period, with the effect of any changes in estimate accounted for on a prospective basis. Unless revised due to specific changes in the estimated useful life, annual depreciation rates are as follows: · Office and lab equipment: 3–5 years · IT equipment: 3 years An item of property, plant and equipment is derecognized upon disposal or when no future economic benefits are expected to arise from the continued use of the asset. Any gain or loss arising on the disposal or retirement of an item of property, plant and equipment is determined as the difference between the sales proceeds and the carrying amount of the asset and is recognized in profit or loss. 2.6 Leases Operating lease payments are recognized as an expense on a straight‑line basis over the lease term, except where another systematic basis is more representative of the time pattern in which economic benefits from the leased asset are consumed. Contingent rentals arising under operating leases are recognized as an expense in the period in which they are incurred. In the event that lease incentives are received to enter into operating leases, such incentives are recognized as a liability. The aggregate benefit of incentives is recognized as a reduction of rental expense on a straight‑line basis, except where another systematic basis is more representative of the time pattern in which economic benefits from the leased asset are consumed. 2.7 Impairment of assets At the end of each reporting period, the Company reviews the carrying amounts of its tangible and intangible assets to determine whether there is any indication that those assets have suffered an impairment loss. If any such indication exists, the recoverable amount of the asset is estimated in order to determine the extent of the impairment loss (if any). Where it is not possible to estimate the recoverable amount of an individual asset, the Company estimates the recoverable amount of the cash‑generating unit to which the asset belongs. Where a reasonable and consistent basis of allocation can be identified, corporate assets are also allocated to individual cash‑generating units, or otherwise they are allocated to the smallest group of cash‑generating units for which a reasonable and consistent allocation basis can be identified. Intangible assets with indefinite useful lives and intangible assets not yet available for use are tested for impairment at least annually, and whenever there is an indication that the asset may be impaired. Recoverable amount is the higher of fair value less costs to sell and value in use. In assessing value in use, the estimated future cash flows are discounted to their present value using a pre‑tax discount rate that reflects current market assessments of the time value of money and the risks specific to the asset for which the estimates of future cash flows have not been adjusted. If the recoverable amount of an asset (or cash‑generating unit) is estimated to be less than its carrying amount, the carrying amount of the asset (or cash‑generating unit) is reduced to its recoverable amount. An impairment loss is recognized immediately in profit or loss. Where an impairment loss subsequently reverses, the carrying amount of the asset (or a cash‑generating unit) is increased to the revised estimate of its recoverable amount, but so that the increased carrying amount does not exceed the carrying amount that would have been determined had no impairment loss been recognized for the asset (or cash‑generating unit) in prior years. A reversal of an impairment loss is recognized immediately in profit or loss. 2.8 Financial assets Financial assets are classified into the following specified categories: financial assets ‘at fair value through profit or loss’ (FVTPL), ‘held-to-maturity’ investments, ‘available-for-sale’ (AFS) financial assets and ‘loans and receivables.’ The classification depends on the nature and purpose of the financial assets and is determined at the time of initial recognition. Management determines the classification at the time of the purchase and re‑evaluates such designation at each subsequent balance sheet date. Purchase and sale of financial assets are recognized on the settlement date, which is the date an asset is delivered to or by the Group. The cost of financial assets includes transaction costs. The carrying amounts of all financial assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount is impaired. If objective evidence exists that a financial asset or group of financial assets is impaired, the amount of the impairment loss is calculated as the difference between the carrying amount of the financial asset and the present value of estimated future cash flows, discounted at the original effective interest rate ( i.e. , the effective interest rate computed at initial recognition of these financial assets). The resulting impairment loss is immediately recognized in net finance costs. An impairment loss on financial assets is reversed if, in a subsequent period, the amount of the impairment loss decreased and this decrease can be related objectively to an event occurring after the impairment loss was recognized. Such reversal is immediately recognized in net finance costs. 2.9 Trade and other receivables Trade and other receivables are initially recognized at fair value and are subsequently carried at amortized cost using the effective interest method. A provision for impairment of trade and other receivables is established when there is objective evidence that the Company will not be able to collect all amounts due according to the original terms of the receivables. 2.10 Research and development incentive receivables Since the Company carries out extensive research and development activities, it benefits from various research and development incentives from certain governmental agencies. These research and development incentives generally aim to partly reimburse approved expenditures incurred in research and development efforts of the Company and are credited to the consolidated statement of profit and loss and other comprehensive income, in other operating income, when there is reasonable assurance that the research and development incentives are receivable. Non‑current research and development incentives receivables are discounted over the period until maturity date according to the appropriate discount rates. 2.11 Cash and cash equivalents Cash and cash equivalents includes cash in hand, deposits held at call with banks and other short term highly liquid investments with original maturities of three months or less and with an insignificant risk of changes in value. Bank overdrafts, if any, are shown within borrowings in current liabilities on the statement of financial position. Cash balances that are not available for use by the Company are presented as “Restricted cash” in the statement of financial position. For the purpose of the statements of cash flows, cash and cash equivalents includes cash on hand and deposits held at call or short term maturity with banks (three months or less with insignificant risk of changes in value). 2.12 Shareholder’s equity An equity instrument is any contract that evidences a residual interest in the assets of an entity after deducting all of its liabilities. Equity instruments issued by the Company are recognized at the proceeds received, net of direct issue costs. Where the Company purchases treasury shares, the consideration paid, including any directly attributable incremental costs (net of income taxes), is deducted from equity attributable to the Company’s equity holders until the shares are cancelled, reissued or disposed of. Where such shares are subsequently sold or reissued, any consideration received, net of any directly attributable incremental transaction costs and the related income tax effects is included in equity attributable to the Company’s equity holders. The Company has never distributed any dividends to its shareholders. As of 31 December 2017, no profits were available for distribution. 2.13 Trade payables Payables after and within one year are measured at amortized cost, i.e., at the net present value of the payable amount. Unless the impact of discounting is material, the nominal value is recognized. 2.14 Financial liabilities Debt and equity instruments issued by the Company are classified as either financial liabilities or as equity in accordance with the substance of the contractual arrangements and the definitions of a financial liability and an equity instrument. Financial liabilities are classified as either “financial liabilities at fair value through profit or loss” or “other financial liabilities”. 2.15 Provisions Provisions are recognized when the Company has a present obligation (legal or constructive) as a result of a past event, it is probable that the Company will be required to settle the obligation, and a reliable estimate can be made of the amount of the obligation. The amount recognized as a provision is the best estimate of the consideration required to settle the present obligation at the end of the reporting period, taking into account the risks and uncertainties surrounding the obligation. When a provision is measured using the cash flows estimated to settle the present obligation, its carrying amount is the present value of those cash flows (where the effect of the time value of money is material). When some or all of the economic benefits required to settle a provision are expected to be recovered from a third party, a receivable is recognized as an asset if it is reasonably certain that reimbursement will be received and the amount of the receivable can be measured reliably. 2.16 Retirement benefits The Company offers a post‑employment, death, disability and healthcare benefit scheme. All employees have access to these schemes. The death, disability and healthcare benefits granted to employees of the Company are covered by an external insurance company, where premiums are paid annually and charged to the income statement as they were incurred. The post‑employment pension plan granted to employees of the Company is a defined contribution plan under Belgian Law. Under defined contribution plans, the Company pays contributions based on salaries to organizations responsible for paying out pensions and social security benefits, in accordance with the laws and agreements applicable in each country. The Belgian defined contribution pension plans are by law subject to minimum guaranteed rates of return, historically 3.25% on employer contributions and 3.75% on employee contributions. These rates have been modified by the law of December 18, 2015 and effective for contribution paid as from 2016 to a new variable minimum return based on the OLO (‘Obligation Lineaire Obligaties’—Belgian Government Bond) rates, with a minimum of 1.75% and a maximum of 3.75%. Hence, those plans classify as defined benefit plans. Until year‑end 2015, the net liability recognized in the statement of financial position was based on the sum of the positive differences, determined by individual plan participant, between the minimum guaranteed reserves and the accumulated contributions based on the actual rates of return at the closing date. From 2016 onwards, these plans are accounted for as defined benefit plans (see note 4.13). The liability recognized in the balance sheet is the present value of the defined benefit obligation less the fair value of plan assets. An independent actuary calculates the defined benefit obligation based on factors such as age, years of service and compensation (projected unit credit method). The present value of the defined benefit obligation is determined by discounting the estimated future cash outflows using interest rates of high‑quality corporate bonds denominated in the currency in which the benefits will be paid and with terms to maturity that approximate the term when the related liability is due. Current service costs are recognized in personnel expenses and reflect the increase in the defined benefit obligation resulting from employee service in the current year. Past service costs are recognized immediately in personnel expenses. The net interest expense on the defined benefit liability is determined by applying the discount rate used to measure the defined benefit obligation at the beginning of the year to the then net defined benefit liability. Net interest expense is recognized in personnel expenses. Remeasurement gains and losses of the defined benefit obligation arising from experience adjustments and changes in actuarial assumptions are recognized immediately in other comprehensive income. 2.17 Short‑term employee benefits Short‑term employee benefits include salaries and social security taxes, paid vacation and bonuses. They are recognized as expenses for the period in which employees perform the corresponding services. Outstanding payments at the end of the period are shown as other current liabilities. 2.18 Share‑based payments Equity‑settled share‑based payments to employees and others providing similar services are measured at the fair value of the equity instruments at the grant date. Details regarding the determination of the fair value of equity‑settled share‑based transactions are set out in note 4.12. The fair value determined at the grant date of the equity‑settled share‑based payments is expensed on a straight‑line basis over the vesting period, based on the Group’s estimate of equity instruments that will eventually vest, with a corresponding increase in equity. At the end of each reporting period, the Group revises its estimate of the number of equity instruments expected to vest. The impact of the revision of the original estimates, if any, is recognized in profit or loss such that the cumulative expense reflects the revised estimate, with a corresponding adjustment to the equity‑settled share‑based payment reserve. Where the terms of equity‑settled share‑based payments are modified, the minimum expense recognized is the expense that would have been recognized if the terms had not been modified. An additional expense is recognized for any modification that increases the total fair value of the share‑based payments, or is otherwise beneficial to the employee as measured at the date of modification. 2.19 Deferred revenue Deferred revenue relates to cash received from commercial partnerships prior to completion of the earnings process. These payments are recognized as revenue over the estimated duration of the Company’s involvement in the research and development programs provided for under the terms of the agreements. Government grants whose primary condition is that the Company should purchase, construct or otherwise acquire non‑current assets are also recognized as deferred revenue in the statement of financial position. 2.20 Income taxes Income tax expense represents the sum of the tax currently payable and deferred tax. The tax currently payable is based on taxable profit for the year. Taxable profit differs from profit as reported in the statement of profit and loss and other comprehensive income because of items of income or expense that are taxable or deductible in other years and items that are never taxable or deductible. The Company’s liability for current tax is calculated using tax rates that have been enacted or substantively enacted by the end of the reporting period. Deferred tax is recognized on temporary differences between the carrying amounts of assets and liabilities in the financial statements and the corresponding tax basis used in the computation of taxable profit (e.g. differences between carrying amounts under IFRS and the statutory tax basis). Deferred tax liabilities are generally recognized for all taxable temporary differences. Deferred tax assets are generally recognized for all deductible temporary differences to the extent that it is probable that taxable profits will be available against which those deductible temporary differences can be utilized. Such deferred tax assets and liabilities are not recognized if the temporary difference arises from goodwill or from the initial recognition (other than in a business combination) of other assets and liabilities in a transaction that affects neither the taxable profit nor the accounting profit. The carrying amount of deferred tax assets is reviewed at the end of each reporting period and reduced to the extent that it is no longer probable that sufficient taxable profits will be available to allow all or part of the asset to be recovered. Deferred tax assets and liabilities are measured at the tax rates that are expected to apply in the period in which the liability is settled or the asset realized, based on tax rates (and tax laws) that have been enacted or substantially enacted by the end of the reporting period. The measurement of deferred tax liabilities and assets reflects the tax consequences that would follow from the manner in which the Company expects, at the end of the reporting period, to recover or settle the carrying amount of its assets and liabilities. Deferred tax assets and deferred tax liabilities are offset if there is a legally enforceable right to offset current tax assets and liabilities and if they relate to income taxes imposed by the same authority on the same taxable entity or in different tax entities that intend to settle current tax assets and liabilities on a net basis or their tax assets and liabilities will be realized simultaneously. 2.21 Revenue and other operating income recognition The Group generates revenue from collaborations and strategic alliances. Revenue is recognized when it is probable that future economic benefits will flow to the group and these benefits can be measured reliably. Further, revenue recognition requires that all significant risks and rewards of ownership of the goods included in the transaction have been transferred to the buyer or when the related services are performed and specific criteria have been met for each of the Group’s activities as described below. Collaborations Collaborations typically include upfront payments, milestone payments, research and development service fees and may involve multiple elements. The Group evaluates whether the elements under these arrangements have value to its collaboration partner or client on a stand‑alone basis. If the Group determines that multiple deliverables exist, the consideration is allocated to one or more units of accounting based upon the best estimate of the selling price of each deliverable. Deliverables that do not meet these criteria are not evaluated separately for the purpose of revenue recognition. The Group receives upfront, milestone and other similar payments related to the sale of services or out‑licensing of products from these collaborations and strategic alliances. The revenue recognition policies can be summarized as follows: Upfront payments Upfront payments, for which there are subsequent deliverables, are initially reported as deferred revenue and are recognized as revenue when earned over the period of the development collaboration or the manufacturing obligation. Upfront payments also include license fees received upfront. Deferred revenue reflects the part of revenue that has not been recognized as income immediately upon receipt of payment and which relates to agreements with multiple components which cannot be separated. Deferred revenue is measured at nominal value. Milestone payments Revenue associated with performance milestones is recognized based upon the achievement of the milestone event if the event is substantive, objectively determinable and represents an important point in the development life cycle of the product. Research and development services fees Research and development service fees are recognized as revenue over the life of the research agreement as the required services are provided and costs are incurred. These services are usually in the form of a defined number of full‑time equivalents (FTE) at a specified rate per FTE. Commercial collaborations resulting in a reimbursement of research and development costs are recognized as revenue as the related costs are incurred. The corresponding research and development expenses are included in research and development expenses in the consolidated financial statements. Grants, research and development incentives and payroll tax rebates Because it carries out extensive research and development activities, the Group benefits from various grants, research and development incentives and payroll tax rebates from certain governmental agencies. These grants, research and development incentives and payroll tax rebates generally aim to partly reimburse approved expenditures incurred in research and development efforts of the Group and are credited to the statement of profit and loss and other comprehensive income, under other operating income, when the relevant expenditure has been incurred and there is reasonable assurance that the grants or research and development incentives are receivable. 2.22 Earnings per share Basic net profit / (loss) per share is computed based on the weighted average number of ordinary shares outstanding during the period, excluding treasury shares. Diluted net profit / (loss) per share is computed based on the weighted‑average number of ordinary shares outstanding including the dilutive effect of options. Options should be treated as dilutive, when and only when their conversion to ordinary shares would decrease net profit per share from continuing operations. 2.23 Fair value measurements Historical cost is generally based on the fair value of the consideration given in exchange for assets. Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value measurement is based on the presumption that the transaction to sell the asset or transfer the liability takes place either in the principal market for the asset or liability or in the absence of a principal market, in the most advantageous market for the asset or liability. The principal or the most advantageous market must be accessible by the Company. The fair value of an asset or a liability is measured using the assumptions that market participants would use when pricing the asset or liability, assuming that market participants act in their economic best interest. All assets and liabilities for which fair value is measured or disclosed in the financial statements are categorized within the fair value hierarchy, described as follows, based on the lowest level input that is significant to the fair value measurement as a whole: Level 1— Quoted (unadjusted) market prices in active markets for identical assets or liabilities Level 2— Valuation techniques for which the lowest level input that is significant to the fair value measurement is directly or indirectly observable Level 3— Valuation techniques for which the lowest level input that is significant to the fair value measurement is unobservable 2.24 Adoption of new and revised standards New ac The following new standards and amendments to standards are mandatory for the first time for the financial year beginning January 1, 2017: ■ Amendments to IAS 12,'Income taxes' on Recognition of deferred tax assets for unrealized losses. These amendments on the recognition of deferred tax assets for unrealized losses clarify how to account for deferred tax assets related to debt instruments measured at fair value. ■ Annual improvements 2014-2016 applicable to three standards of which changes on IFRS 1 and IAS 28 are applicable as of 1 January 2018 and changes on

Critical accounting judgements

Critical accounting judgements and key sources of estimation uncertainty	12 Months Ended
	Dec. 31, 2017
Critical accounting judgements and key sources of estimation uncertainty
Critical accounting judgements and key sources of estimation uncertainty	3. Critical accounting judgements and key sources of estimation uncertainty In the application of the Company’s accounting policies, which are described above, the Company is required to make judgments, estimates and assumptions about the carrying amounts of assets and liabilities that are not readily apparent from other sources. The estimates and associated assumptions are based on historical experience and other factors that are considered to be relevant. Actual results may differ from these estimates. The estimates and underlying assumptions are reviewed on an ongoing basis. Revisions to accounting estimates are recognized in the period in which the estimate is revised if the revision affects only that period or in the period of the revision and future periods if the revision affects both current and future periods. The following areas are areas where key assumptions concerning the future, and other key sources of estimation uncertainty at the end of the reporting period, have a significant risk of causing a material adjustment to the carrying amounts of assets and liabilities within the next financial year: Going concern The Group has incurred net losses since its inception and for the year ended December 31, 2017, its consolidated statement of profit and loss and other comprehensive income reflects a net loss, and its consolidated statement of financial position includes a loss carried forward. On February 27, 2018, the Board has reviewed and approved the consolidated financial statements and accounting standards. Taking into account the cash and cash equivalents and current financial asset position of €359.8 million on December 31, 2017, the Board is of the opinion that the Group is a going concern basis. Whilst the current cash position is sufficient for the Group’s immediate and mid‑term needs, the Board pointed out that if the research and development activities continue to deliver added value, the Company may seek additional funding to support the continuing development of its portfolio of products or to be able to execute other business opportunities. Revenue recognition For revenue recognition, the significant estimates relate to allocation of value to the separate elements in multiple element arrangements. With respect to the allocation of value to the separate elements, the Company is using the stand‑alone selling prices or management’s best estimates of selling prices to estimate the fair value of the elements and account for them separately. Revenue is allocated to each deliverable based on the fair value of each individual element and is recognized when the revenue recognition criteria described above are met. Upfront fees under collaboration or licensing agreements are recognized over the expected duration of the performance obligations, unless there is no continuous involvement required. Management estimates this period at the start of the collaboration and validates the remaining estimated collaboration term at each closing date. Measurement of share‑based payments In accordance with IFRS 2— Share‑based Payment , the fair value of the options at grant date is recognized as an expense in the statement of profit and loss and other comprehensive income over the vesting period. Subsequently, the fair value recognized in equity is not re‑measured. The fair value of each stock option granted during the year is calculated using the Black‑Scholes pricing model. This pricing model requires the input of subjective assumptions, which are detailed in note 4.12. Recognition of deferred tax assets Deferred tax assets are recognized only if management assesses that these tax assets can be offset against positive taxable income within a foreseeable future. This judgment is made by management on an ongoing basis and is based on budgets and business plans for the coming years, including planned commercial initiatives. These budgets and business plans are reviewed and approved by the Board of Directors. Since inception, the Group has reported losses, and consequently, the Group has unused tax losses. The deferred tax assets are currently not deemed to meet the criteria for recognition as management is not able to provide any convincing positive evidence that deferred tax assets should be recognized. Therefore, management has concluded that deferred tax assets should not be recognized on December 31, 2017.

Notes_relating to the consolida

Notes relating to the consolidated statement of financial position	12 Months Ended
	Dec. 31, 2017
Notes relating to the consolidated statement of financial position
Notes relating to the consolidated statement of financial position	4. Notes relating to the consolidated statement of financial position 4.1 Intangible assets (in thousands of €) Opening balance as on January 1, 2015 Cost € 67 Accumulated amortization (60) Book value at the beginning of the year 7 Movements Additions 5 Amortization (5) Balance as on December 31, 2015 Cost 72 Accumulated amortization (65) Book value at year end 7 Movements Additions 21 Amortization (11) Balance as on December 31, 2016 Cost 93 Accumulated amortization (76) Book value at year end 17 Movements Additions 6 Amortization (10) Balance as on December 31, 2017 Cost 99 Accumulated amortization (86) Book value at year end € 13 The intangible assets correspond to software. There are no commitments to acquire additional intangible assets. No intangible assets are pledged as security for liabilities nor are there any intangible assets whose title is restricted. 4.2 Property, plant and equipment Office and lab (in thousands of €) IT equipment equipment Total Opening balance as on January 1, 2015 Cost € 63 € 935 € 998 Accumulated depreciation (48) (784) (832) Book value at the beginning of the year 15 151 166 Movements Additions 30 244 274 Depreciation (18) (173) (191) Closing balance as on December 31, 2015 Cost 93 1,179 1,272 Accumulated depreciation (66) (957) (1,023) Book value at year end 27 222 249 Movements Additions 115 725 840 Depreciation (38) (285) (323) Closing balance as on December 31, 2016 Cost 208 1,904 2,112 Accumulated depreciation (104) (1,242) (1,346) Book value at year end 104 662 766 Movements Additions 25 321 346 Cost of disposals — (69) (69) Depreciation (53) (372) (425) Accumulated depreciation on disposals — 58 58 Closing balance as on December 31, 2017 Cost 233 2,156 2,389 Accumulated depreciation (157) (1,556) (1,713) Book value at year end € 76 € 600 € 676 There are no commitments to acquire property, plant and equipment. Furthermore, no items of property, plant and equipment are pledged. 4.3 Non‑current financial assets Non‑current financial assets consist of a minority participation in Bird Rock Bio, Inc. (formerly RuiYi, Inc.) (Bird Rock Bio). The Company has no significant influence over these investments. This investment is classified as “available for sale”—investment and if no reliable fair value measurements are available, valued at cost. At the end of 2017, this investment was recorded at cost as no reliable fair value information was available. In December 2017, the Company sold the minority participation in FairJourney Biologics LDA, recorded at cost at the end of 2016 as no reliable fair value information was available at that time, and realized a gain of €0.9 million. This gain is reported in the income statement as financial income. 4.4 Other non‑current assets On December 31, 2017, the Group had a total receivable of €0.9 million in relation with the sale of its minority participation in FairJourney Biologics LDA in December 2017. The amount of any services to be rendered by FairJourney Biologics LDA invoiced until December 31, 2019, will be considered as a payment in-kind to be off-set against the receivable generated by the sale of the minority participation. €0.1 million of this receivable has a long term maturity (more than 12 months) and has been recorded as “Other non-current assets”. The balance of €0.8 million has a short term maturity and has been recorded as “Trade and other receivables”, see note 4.7. 4.5 Research and development incentive receivables Year Ended December 31, (in thousands of €) 2017 2016 2015 Research and development incentive receivables—current € 158 € 163 € — Research and development incentive receivables—non-current 3,033 2,046 1,568 € 3,191 € 2,209 € 1,568 On December 31, 2017, the Group has recorded a tax receivable of €3.2 million compared to €2.2 million on December 31, 2016, in relation with a research and development incentive tax scheme in Belgium under which the research and development incentives can be refunded after five years if not offset against future income tax expense. The research and development incentives are recorded in other operating income (see note 5.2) in the consolidated statement of profit and loss and other comprehensive income. These amounts are expected to be gradually reimbursed in cash as from 2018 onwards. 4.6 Restricted cash Year Ended December 31, (in thousands of €) 2017 2016 2015 Non ‑ current restricted cash Rental guarantees € 256 € 244 € — Escrow account > 1 year — 905 — Total non ‑ current € 256 € 1,149 € — Current restricted cash Escrow account < 1 year 1,692 786 — Total restricted cash € 1,948 € 1,935 € — On December 31, 2017, the Group had a total amount of €1.9 million of restricted cash. This amount is split as follows: · A non‑current part for an amount of €0.25 million with a long term maturity (more than 12 months) and mainly relating to a deposit guarantee paid under the lease agreement for the laboratory and offices of the company. · A current part for an amount of €1.69 million with a short maturity and relating to an escrow account opened under an agreement with a third party involved in the collaboration with AbbVie. This escrow account will be released to the Group or to the third party under certain conditions after the completion of the work plan of the related collaboration agreement with AbbVie. 4.7 Trade and other receivables The trade and other receivables are composed of receivables which are detailed below: Year Ended December 31, (in thousands of €) 2017 2016 2015 VAT receivable € 317 € 278 € 175 Trade receivables 845 1,118 719 Other receivables 750 — — Interest receivable — 6 17 VLAIO grant receivable 930 568 445 € 2,842 € 1,970 € 1,356 The nominal amounts of all trade and other receivables approximate their respective fair values. The VAT receivable relates to VAT amounts to be recovered in the first quarter of 2018. Trade receivables correspond to amounts invoiced to the collaborators or strategic allies of the Group. No bad debt allowance was recorded nor were any trade receivables impaired on December 31, 2017 and December 31, 2016. The amount of €0.8 million in “Other receivables” relates to the short-term part of the receivable with FairJourney Biologics LDA described in note 4.4. The Flanders Innovation and Entrepreneurship Agency grant to receive consists of earned income from government grants for which no payments have been received but for which the relating expenditures have been incurred. For more information on the Flanders Innovation and Entrepreneurship Agency grants to receive, see note 5.2. 4.8 Prepaid expenses The prepaid expenses on December 31, 2017 amounted to €2.3 million compared to €2.1 million on December 31, 2016. On December 31, 2017, the prepaid expenses related to (i) a €1.0 million upfront reservation fee paid in 2017 to a third-party drug product manufacturer, (ii) a €0.5 million license fee paid to a third party involved in the license agreement signed with AbbVie in April 2016, this amount being recognized as expense in the statement of profit and loss over the period of the agreement, and (iii) a €0.9 million to insurance prepayments and prepayments for other invoices for which the services will be rendered in future periods. 4.9 Current financial assets On December 31, 2017, the current financial assets amounted to €168.9 million compared to €6.8 million on December 31, 2016. These current financial assets relate to: · Financial instruments in the form of money market funds with a recommended investment horizon of 6 months. These funds are highly liquid investments and can be readily converted into a known amount of cash, but because of their historical volatility these funds cannot be classified as cash and cash equivalents. Values recognized on the balance sheet are the fair values. · A USD term account with a maturity of 6 months. Please also refer to note 6.1 for more information on the financial instruments. 4.10 Cash and cash equivalents Year Ended December 31, (in thousands of €) 2017 2016 2015 Cash equivalents € 25,000 € 54,500 € 11,006 Cash and bank balances 165,867 35,397 24,508 € 190,867 € 89,897 € 35,514 On December 31, 2017, cash and cash equivalents amounted to €190.9 million compared to €89.9 million on December 31, 2016 and included cash equivalents and cash and bank balances held in different banks. Cash positions are invested with preferred financial partners, which are mostly considered to be high quality financial institutions with sound credit ratings, or in highly rated money market funds. Policies are in place that limit the amount of credit exposure to any one financial institution (see also note 6.4). 4.11 Shareholders’ capital Roll forward of number of shares outstanding: Number of shares outstanding on January 1,2015 15,705,112 Exercise of Options on September 1,2015 97,655 Number of shares outstanding on December 31,2015 15,802,767 Private placement (Federated Investment) on January 20, 2016 1,480,420 Exercise of Options on February 15, 2016 2,200 Exercise of Options on March 16, 2016 10,000 Exercise of Options on April 21, 2016 10,000 Exercise of Options on May 27 , 2016 33,092 Private placement (Sunflower) on June 1, 2016 2,703,000 Exercise of Options on September 26, 2016 70,000 Exercise of Options on October 17, 2016 15,000 Number of shares outstanding on December 31, 2016 20,126,479 U.S. initial public offering on Nasdaq on May 17, 2017 5,865,000 Over-allotment option exercised by underwriters on May 19, 2017 879,750 Exercise of Options on August 24, 2017 5,000 Exercise of Options on September 1, 2017 15,000 Exercise of Options on October 2, 2017 1,400 Exercise of Options on November 7, 2017 950 Exercise of Options on November 14, 2017 4,260 Exercise of Options on November 15, 2017 40,750 Exercise of Options on November 21, 2017 53,092 Exercise of Options on November 22, 2017 7,730 Exercise of Options on December 4, 2017 65,380 U.S. second public offering on Nasdaq on December 13, 2017 4,440,000 Over-allotment option exercised by underwriters on December 14, 2017 666,000 Exercise of Options on December 18, 2017 9,850 Number of shares outstanding on December 31,2017 32,180,641 New shares issued during 2016 In January 2016, U.S. funds advised by subsidiaries of Federated Investors, Inc. purchased 1,480,420 new shares issued by the Company, and subsequently in June 2016, following a private placement, 2,703,000 additional new shares were issued to institutional investors. 140,292 new shares were also issued in 2016 as a result of the exercise of stock options under the argenx Employee Stock Option Plan. This resulted in a total of 20,126,479 ordinary shares with a nominal value of €0.1 per share on December 31, 2016. At the same date, the authorized unissued share capital of the Company amounted to €4.5 million divided into 45 million ordinary shares. New shares issued during 2017 On May 17, 2017, argenx SE offered 5,865,000 of its ordinary shares through an initial public offering in the United States in the form of ADSs at a price to the public of $17.00 per ADS, before underwriting discounts and commissions and offering expenses. On May 19, 2017, the underwriters of the offering exercised their over-allotment option to purchase 879,750 additional ADSs in full. As a result, argenx SE received €102.1 million of total gross proceeds from the offering, decreased by €9.6 million of underwriter discounts and commissions, and offering expenses, of which €8.9 million has been deducted from equity. The total net cash proceeds from this offering amounted to €92.5 million. On December 14, 2017, argenx SE offered 4,440,000 of its ordinary shares through a public offering in the United States in the form of ADSs at a price to the public of $52.00 per ADS, before underwriting discounts and commissions and offering expenses. On December 15, 2017, the underwriters of the offering exercised their over-allotment option to purchase 666,000 additional ADSs in full. As a result, argenx SE received €225.6 million of gross proceeds from this offering, decreased by €14.3 million of underwriter discounts and commissions, and offering expenses, of which €14.1 million has been deducted from equity. The total net cash proceeds from the Offering amounted to €211.3 million. For both offerings completed in 2017, the ADSs are evidenced by American Depositary Receipts (ADRs), and each ADS represents the right to receive one ordinary share. These ADSs are listed on the NASDAQ Global Select Market under the symbol “ARGX”. 203,412 new shares were also issued in 2017 as a result of the exercise of stock options under the argenx Employee Stock Option Plan. This resulted in a total of 32,180,641 ordinary shares with a nominal value of €0.1 per share on December 31, 2017. The extraordinary general meeting of the Company of November 7, 2017 had authorized the board of directors to issue up to a maximum of 20% of the then outstanding share capital for a period of 18 months, or up to a capital increase of €537,852.60 represented by 5,378,526 shares. The board of directors has issued 5,106,000 shares on the occasion of the U.S. public offering in December 2017 and as of December 31, 2017, the existing authorization covered the issuance of up to 272,526 shares. 4.12 Share‑based payments The Company has a stock options scheme for the employees of the Company and its subsidiaries. In accordance with the terms of the plan, as approved by shareholders, employees may be granted options to purchase ordinary shares at an exercise price as mentioned below per ordinary share. The Group has granted on June 20, 2017 a total of 120,536 stock options and on December 14, 2017 a total of 653,825 stock options to its employees, Board members and consultants. The total number of stock options outstanding on December 31, 2017 totaled 2,862,216 compared to 2,293,636 on December 31, 2016 and 1,752,926 on December 31, 2015. No stock options were expired in the years ended December 31, 2017, 2016 and 2015. 203,412 stock options have been exercised in the year ended December 31, 2017 compared to 140,292 in the year ended December 31, 2016 and 97,656 in the year ended December 31, 2015. A total of 2,369 stock options have been forfeited in the year ended December 31, 2017 compared to 31,174 in the year ended December 31, 2016 and 47,333 in the year ended December 31, 2015. The stock options are granted to employees, consultants or directors of the Company and its subsidiaries. The stock options have been granted free of charge. Each employee’s stock option converts into one ordinary share of the Company upon exercise. No amounts are paid or payable by the recipient on receipt of the option. The options carry neither rights to dividends nor voting rights. Options may be exercised at any time from the date of vesting to the date of their expiry. The stock options granted vest, in principle, as follows: · 1/3rd of the stock options granted will vest on the first anniversary of the granting of the stock options, and · 1/24th of the remaining 2/3rd of the stock options granted will vest on the last day of each of the 24 months following the month of the first anniversary of the granting of the stock options. No other conditions are attached to the stock options. The following share‑based payment arrangements were in existence during the current and prior years and which are exercisable at the end of each period presented: Exercise price Outstanding per stock stock options on options December 31, Expiry date (in €) 2017 2016 2015 2019 € 3.95 — — 103,370 2020 3.95 36,960 112,738 62,460 2021 3.95 2,850 3,800 3,800 2022 2.44 — — 686,732 2023 3.95 — — 55,747 2024 2.44 314,593 360,787 — 2024 2.44 135,890 169,926 — 2024 3.95 15,692 55,746 — 2024 7.17 516,100 522,500 537,917 2024 2.44 83,820 83,820 — 2025 11.44 39,000 39,000 56,500 2025 10.34 3,000 3,000 3,000 2025 9.47 235,514 235,733 243,400 2026 11.38 60,000 60,000 — 2026 11.47 282,310 283,360 — 2026 14.13 362,126 363,226 — 2027 18.41 120,536 — — 2027 € 21.17 653,825 — — 2,862,216 2,293,636 1,752,926 2017 2016 2015 Number of Weighted average Number of Weighted average Number of Weighted average stock options exercise price stock options exercise price stock options exercise price Outstanding at January 1 2,293,636 € 7.72 1,752,926 € 5.37 1,595,015 € 4.39 Granted 774,361 20.74 712,176 12.82 302,900 9.84 Exercised (203,412) 3.46 (140,292) 3.52 (97,656) 2.44 Forfeited (2,369) 12.52 (31,174) 10.90 (47,333) 7.17 Outstanding at December 31, 2,862,216 11.54 2,293,636 7.72 1,752,926 5.37 Exercisable at December 31, 1,598,829 € 6.80 1,257,091 € 4.68 1,366,703 € 4.41 The weighted average remaining contractual life of the stock options outstanding amounted to 8.03 years on December 31, 2017 (December 31, 2016: 8.09 years). The table below shows the weighted average remaining contractual life for each range of exercise price: Weighted average remaining Outstanding on contractual life Exercise price (in €) December 31,2017 (in years) 2.44–3.95 589,805 5.81 7.17–9.47 751,614 7.28 10.33–14.13 746,436 8.62 18.41–21.17 774,361 9.88 The fair market value of the stock options has been determined based on the Black and Scholes model. The expected volatility in the model is based on the historical volatility of peer companies and historical volatility of the Group since its initial public offering. Below is an overview of the parameters used in relation to the grants during 2017: Stock options granted in June 2017 Dec 2017 Number of options granted 120,536 653,825 Average fair value of options (in EUR) € 7.90 € 37.10 Share price (in EUR) € 17.76 € 53.50 Exercise price (in EUR) € 18.41 € 21.17 Expected volatility 36.6 % 36.1 % Average expected option life (in years) 10 10 Risk ‑ free interest rate 0.61 % 0.53 % Expected dividends — % — % Below is an overview of the parameters used in relation to the grants during 2016: Stock options granted in May 2016 June 2016 Dec 2016 Number of options granted 288,950 60,000 363,226 Average fair value of options (in EUR) € 5.32 € 5.46 € 7.25 Share price (in EUR) € 11.10 € 11.36 € 14.96 Exercise price (in EUR) € 11.47 € 11.38 € 14.13 Expected volatility 40.2 % 39.6 % 38.0 % Average expected option life (in years) 10 10 10 Risk ‑ free interest rate 0.52 % 0.46 % 0.67 % Expected dividends — % — % — % Below in an overview of the parameter used in relation to the grants during 2015: Stock options granted in June 2015 Sept 2015 Dec 2015 Number of options granted 56,500 3,000 243,400 Average fair value of options (in EUR) € 7.79 € 6.79 € 6.25 Share price (in EUR) € 11.58 € 10.24 € 9.85 Exercise price (in EUR) € 11.44 € 10.34 € 9.47 Expected volatility 59 % 59 % 58 % Average expected option life (in years) 10 10 10 Risk‑free interest rate 1.21 % 1.08 % 0.98 % Expected dividends — % — % — % The total share‑based payment expense recognized in the consolidated statement of comprehensive income totaled €4.3 million for the year ended December 31, 2017 compared to €2.8 million for the year ended December 31, 2016 and €2.3 million for the year ended December 31, 2015. 4.13 Defined benefit plans Our personnel in Belgium participated in a defined contribution plan (extra-legal pension). The Belgian defined contribution pension plans were by law subject to minimum guaranteed rates of return, 3.25% on employer contributions and 3.75% on employee contributions. These rates, which apply as an average over the entire career, may be modified by Royal Decree. Therefore, those plans were basically accounted for as defined contribution plans. As a consequence of the law of December 18, 2015, minimum returns were guaranteed by the employer as follows: (a) for the contributions paid as from January 1, 2016, a new variable minimum return based on OLO rates, with a minimum of 1.75% and a maximum of 3.75%. In review of the low rates of the OLO in the last years, the return has been initially set to 1.75%; (b) for the contributions paid until end of December 2015, the previously applied legal returns as mentioned above, continue to apply until the leaving of the employees. In view of the minimum returns guarantees, the Belgian defined contribution plans classify as defined benefit plans as from end December 2015. As at December 31, 2015, a net liability of €10 thousand was recognized in the balance sheet as the minimum rates of return to be guaranteed by the employer were closely matched by the rates of return guaranteed by the insurer. As at December 31, 2016 and 2017, a net defined benefit obligation of respectively €1 thousand and €25 thousand was recorded. The amounts recognized in the balance sheet are as follows: (in thousands of €) 2017 2016 2015 Defined benefit obligation € 1,007 € 670 € 486 Fair value of plan assets 982 669 486 Deficit / surplus (−) of funded obligations 25 1 — Net liability (asset) € 25 € 1 € — The movement in the defined benefit obligation, plan assets, net liability and asset over the year is as follows: (in thousands of €) 2017 2016 Defined benefit obligation at 1 January € 670 € 486 Service cost 352 113 Interest expense / income (−) 11 6 Contributions by plan participants (148) (64) Actuarial gains (-) / losses (+) 124 131 Benefits paid / transfers out (2) (2) Defined benefit obligation at 31 December € 1,007 € 670 (in thousands of €) 2017 2016 Fair value of plan assets at 1 January € 669 € 486 Interest expense / income (−) 10 7 Administrative costs & taxes (46) (19) Contributions by company & participants 423 176 Contributions by plan participants (148) (64) Actuarial gains (+) / losses (-) 76 85 Benefits paid / transfers out (2) (2) Fair value of plan assets at 31 December € 982 € 669 In the income statement, current service cost and interest expense or income are included in the operating loss. The Group’s estimated employer contributions for 2017 amount to €0.3 million compared to €0.1 million in 2016. Plan assets on December 31, 2016 and 2017 consisted fully of insurance contracts and did not include direct positions in the Company’s shares or bonds, nor do they include any property used by the Company. As the insurance contracts match the benefits payable by the plan, the plan assets correspond to the present value of the related obligations. The principal actuarial assumption on the balance sheet date (weighted averages based on outstanding defined benefit obligation) was: Actuarial assumption 2017 2016 Discount rate 1.3 % 1.3 % The duration of the benefit obligations equals 21 years. Sensitivity analyses show the following effects: Sensitivity analysis Change in Impact on defined ‑ (in thousands of €) assumption benefit obligation % Discount rate −0.25 % Increase by 35.9 3.56 % Discount rate 0.25 % Decrease by 31.0 (3.08) % The above analyses were done on a mutually exclusive basis, and holding all other assumptions constant. Through its defined benefit plan, the Group is exposed to a number of risks, the most significant of which are detailed below: Asset volatility The plan liabilities are calculated using a discount rate set with reference to corporate bond yields; if plan assets underperform this yield, this will create a deficit. Changes in bond yields A decrease in corporate bond yields will increase plan liabilities, although this will be partially offset by an increase in the value of the plan’s bond holdings. Salary risk The majority of the plan’s benefit obligations are calculated by reference to the future salaries of plan members. As such, a salary increase of plan members higher than expected will lead to higher liabilities. Longevity risk Belgian pension plans provide for lump sum payments upon retirement. As such there is limited or no longevity risk. The weighted average age of the plan participants equals 46 years on December 31, 2017 compared to 48 years on December 31, 2016. 4.14 Trade and other payables Year Ended December 31, (in thousands of €) 2017 2016 2015 Trade payables € 4,395 € 4,385 € 1,886 Accruals for invoices to be received 4,046 5,444 1,239 Short-term employee benefits 6,844 2,362 1,418 € 15,285 € 12,191 € 4,543 Trade payables correspond primarily to clinical and manufacturing activities. The fair value of trade payables approximates their carrying amount, no trade payables were overdue. The accruals for invoices to be received amount to €4.0 million for the year ended December 31, 2017 and relate to invoices to be received from clinical manufacturing organizations for the manufacturing of drug products to be used in clinical trials and from clinical research organization for expenses incurred in relation with ongoing clinical trials were not yet charged to the Group on December 31, 2017. Short‑term employee benefits include payables and accruals for salaries and bonuses to be paid to the employees of the Group. 4.15 Current tax liability As part of its business restructuring, the Group transferred the legal ownership of its intellectual property rights from the Dutch argenx SE to its wholly owned Belgian subsidiary, argenx BVBA effective as of January 1, 2017. The tax consequences of this transaction for argenx SE have been agreed with the Dutch tax authorities on March 23, 2017, and relate to: (i) The at arm’s length compensation for the Company being fixed at €79.9 million; and (ii) the right to offset the full amount of the Company’s tax loss carry forward of €77.5 million against this compensation. Hence, the business restructuring has resulted in a taxable amount for argenx SE of €2.4 million subject to a Dutch corporate income tax rate of 25%, or a tax amount of €0.6 million. For the same business restructuring, there is also a tax ruling pending in Belgium, and if approved as currently proposed, the restructuring will result in additional tax deductible costs for argenx BVBA of €79.9 million. The Group cannot assure that it will obtain the tax ruling from the Belgian tax authorities, and it may not be allowed to treat the aforementioned amount as a tax deductible cost in the Belgian subsidiary. Accordingly, no deferred tax asset has been recognized in respect of these tax operating losses. 4.16 Deferred revenue Deferred revenue relates to cash received from collaboration and strategic alliances prior to completion of the earnings process. On December 31, 2017, deferred revenue amounted to €10.1 million compared to €30.2 million at the same date in 2016, and included €9.8 million related to the upfront payment received from AbbVie in April 2016, and €0.3 million related to the upfront payment received from LEO Pharma in May 2015. These payments are recognized as revenue over the estimated duration of the Group’s involvement in the research and development programs provided for under the terms of the agreements.

Notes to consolidated statement

Notes to consolidated statement of profit and loss and other comprehensive income	12 Months Ended
	Dec. 31, 2017
Notes to consolidated statement of profit and loss and other comprehensive income
Notes to consolidated statement of profit and loss and other comprehensive income	5. Notes to consolidated statement of profit and loss and other comprehensive income 5.1 Revenue Year Ended December 31, (in thousands of €) 2017 2016 2015 Upfront payments € 20,137 € 9,103 € 2,194 Milestone payments 9,677 500 343 Research and development service fees (FTE) 6,601 5,110 4,317 € 36,415 € 14,713 € 6,854 For the years ended December 31, 2017 and 2016, the majority of the revenue was generated under the agreements with Shire, LEO Pharma and AbbVie, each as described below. These agreements comprise elements of upfront payments, milestone payments based on development criteria and research and development funding on an agreed FTE basis. The upfront payments received in the year ended December 31, 2017 corresponded principally to the partial recognition in revenue over the period of the upfront payment received following the signatures of a collaboration agreement with AbbVie in April 2016, with LEO Pharma in May 2015, and with Shire in February 2012. These payments are recognized as revenue over the estimated period of the Group’s continuing involvement in the research and development activities provided for under the terms of these agreements. The milestone payment of €9.7 million recognized in the year ended December 31, 2017 related to a payment received under the AbbVie and LEO Pharma collaborations. The research and development service fees (FTE) for the year ended December 31, 2017 corresponded to FTE payments received under the collaboration agreements of €2.1 million from Shire, €3.9 million from LEO Pharma and €0.6 million from Staten Biotechnology B.V. (Staten). Below are summaries of the key collaborations. AbbVie In April 2016, the Group entered into a collaboration agreement with AbbVie S.À.R.L. (AbbVie) to develop and commercialize ARGX 115. Under the terms of the collaboration agreement, the Group will be responsible for conducting and funding all ARGX‑115 research and development activities up to completion of IND enabling studies. The Group has granted AbbVie an exclusive option, for a specified period following completion of IND enabling studies, to obtain a worldwide, exclusive license to the ARGX‑115 program to develop and commercialize products. Following the exercise of the option, AbbVie will assume certain development obligations, and will be solely responsible for all research, development and regulatory costs relating to the products. The Group received an upfront, non refundable, non creditable payment of $40 million (€35.1 million as of the date the payment was received) from AbbVie for the exclusive option to license ARGX‑115, and we achieved the first of two preclinical milestones, triggering a $10.0 million (€8.9 million based on the exchange rate in effect as of the date the payment was received) payment, and are eligible to receive a second near‑term preclinical milestones of $10 million. The Group is also eligible, if AbbVie exercises its option, to receive additional development, regulatory and commercial milestone payments in aggregate amounts of up to $110 million, $190 million and $325 million, respectively, as well as tiered royalties on sales at percentages ranging from the mid‑single digits to the lower teens, subject to customary reductions. The Group has the right, on a product‑by‑product basis to co‑promote ARGX‑115 based products in the European Economic Area and Switzerland and to combine the product with the Group’s own future immuno‑oncology programs. The co‑promotion effort would be governed by a co‑promotion agreement negotiated in good faith by the parties In addition to the ARGX‑115 program, and upon reaching a predetermined preclinical stage milestone, AbbVie will fund further GARP‑related research by the Group for an initial period of two years. AbbVie will have the right to license additional therapeutic programs emerging from this research, for which the Group could receive associated milestone and royalty payments. If AbbVie does not exercise its option to license ARGX-115, the Group has the right to pursue development and commercialization of ARGX-115 by itself or with another partner. Unless terminated earlier upon mutual agreement, for material breach or as otherwise specified in the agreement, the term of the option and license agreement ends, with respect to the ARGX‑115 program, upon the earliest of (i) a technical failure of the IND‑enabling studies which is outside of the Group’s control, (ii) AbbVie’s election to not exercise its option, or (iii) following AbbVie’s exercise of the option, fulfilment of all payment obligations under the agreement. AbbVie may terminate the agreement for any reason upon prior written notice to the Group. AbbVie’s royalty payment obligations expire, on a product‑by‑product and country‑by‑country basis, on the date that is the later of (i) such time as there are no valid claims covering such product, (ii) expiration of regulatory or market exclusivity in respect of such product or (iii) 10 years after the first commercial sale of such product sold in that country under the agreement. Shire In February 2012 the Group entered into a research collaboration and exclusive product license option agreement with Shire International GmbH (Shire). Pursuant to the agreement the Group is using its SIMPLE Antibody™ Technology to create novel human therapeutic antibodies addressing diverse rare and unmet diseases being pursued by Shire. Shire has the option to license the most promising antibody leads from each collaborative program for further developments and commercialization worldwide, in return for milestone and royalty payments. Under the terms of the license, the Group has already received technology access fees and research funding and is eligible to receive discovery milestone payments. In September 2013, the Group received a first technical success milestone payment from Shire, and in January 2014, the Group received two extra discovery milestone payments from Shire. In January 2013 the scope of the agreement was expanded by the parties with no change to the agreement structure. On May 30, 2014 the collaboration between Shire and the Group was expanded to include in addition to the use of the Group’s entire suite of human antibody discovery technologies for an expanded set of disease targets. Pursuant to the amended agreement (which is in addition to the existing collaboration), the Group shall apply during multiple years these technologies for the generation and development of human mAbs against multiple targets selected by Shire in line with its therapeutic focus. Shire has the option to license the most promising antibody leads for further developments and commercialization worldwide, in return for fees, clinical, regulatory and sales milestones, as well as single digit royalties on therapeutic product sales. As of the reporting date, this is considered contingent revenue. Shire will be responsible for clinical development and commercialization of products, with the Group having the right to license any programs not pursued by Shire into its own development pipeline. Under the amended agreement, Shire made an upfront cash payment of €3 million. At the same time as expanding the collaboration, Shire made an equity investment during the Group’s IPO in July 2014 of €12 million. The upfront cash payment is recognized based on the principle of percentage of completion of the work plan. Research funding based on an agreed FTE rate, is recognized on a monthly basis in the income statement. Leo Pharma In May 2015 the Group and LEO Pharma A/S (LEO Pharma), a global healthcare company dedicated to helping people achieve healthy skin, entered into an alliance in which they will collaborate to develop innovative antibody‑based solutions for the treatment of chronic inflammation underlying many skin conditions. Under the terms of the agreement, LEO Pharma received exclusive access to an existing argenx antibody currently in preclinical development for inflammation related skin diseases. The Group receives pre‑IND payments of €4.5 million, including an upfront payment. The companies will co‑fund product development costs up to clinical trial application (CTA) filing. The Group is also eligible to receive clinical, regulatory, and sales milestone payments, as well as tiered royalties on sales of resulting products at percentages ranging from the low single digits to the low teens, which are, as of the reporting date, considered contingent revenue. The access fee related to the existing argenx antibody that has been received is recognized based on the principle of percentage of completion of the work plan. Development and management funding based on an agreed FTE rate, is recognized on a monthly basis in the income statement. 5.2 Other operating income Year Ended December 31, (in thousands of €) 2017 2016 2015 Grants € 422 € 779 € 1,598 Research and development incentives 983 641 608 Payroll tax rebates 3,436 1,019 895 € 4,841 € 2,439 € 3,101 Grants The Flanders Innovation and Entrepreneurship Agency provided the Group with several grants. On December 31, 2017 the situation of the grants received by the Group reflected the expenses incurred by the Group in the various research and development projects sponsored by Flanders Innovation and Entrepreneurship Agency and was as follows: (Amounts presented in thousands of €) Flanders Innovation & Entrepreneurship—TGO Grantor: Flanders Innovation & Entrepreneurship Agency Start date: 01/01/2013 End date: 06/30/2017 Amount granted and approved: € 2,697 Amount recognized: 2,697 Flanders Innovation & Entrepreneurship—Baekelandt Grantor: Flanders Innovation & Entrepreneurship Agency Start date: 01/01/2014 End date: 12/31/2017 Amount granted and approved: € 277 Amount recognized: 270 Flanders Innovation & Entrepreneurship 4 Grantor: Flanders Innovation & Entrepreneurship Agency Start date: 01/01/2015 End date: 12/31/2017 Amount granted and approved: € 1,568 Amount recognized: 1,568 No conditions related to the above government grants were unfulfilled, nor were there any contingencies related thereon at the date of the approval of these financial statements, except for those described in note 7.2 of this report. Other Incentives Research and development incentives The Group has accounted for a tax receivable of €1.0 million in the year ended December 31, 2017, compared to €0.6 million in the year ended December 31, 2016, following a research and development tax incentive scheme in Belgium according to which the incentive will be refunded after a 5 year period, if not offset against the current tax payable over the period (see also note 4.5). Payroll tax rebates The Group accounted for €3.4 million payroll tax rebates in the year ended December 31, 2017, compared to €1.0 million in the year ended December 31, 2016, as a reduction in withholding income taxes for its highly‑qualified personnel employed in its research and development department. 5.3 Segment reporting The Group operates from the Netherlands, Belgium and the United States of America. Revenues are invoiced by the subsidiary in Belgium and are generated by clients geographically located as shown in the table below. The table below also discloses where the non‑current assets from the group are situated. Revenue from external customers Year ended December 31, (in thousands of €) 2017 2016 2015 Netherlands € 628 € 548 € 275 Belgium — — — Germany — 311 2,190 Denmark 6,240 3,066 827 Switzerland 2,486 3,315 3,127 United States 1 47 435 Luxembourg 27,060 7,426 — Total € 36,415 € 14,713 € 6,854 Information about major clients: The Group received €36.4 million of revenue from its external customers in the year ended December 31, 2017 compared to €14.7 million over the same period in 2016, of which €27.1 million came from the Group’s largest client, €6.2 million from its second largest client and €2.5 million from its third largest client, compared to respectively €7.4 million, €3.3 million and €3.1 million in the year ended December 31, 2016. 5.4 Research and development expenses Year Ended December 31, (in thousands of €) 2017 2016 2015 Personnel expense € 16,473 € 9,844 € 6,665 External research and development expenses 27,893 17,562 11,653 Materials and consumables 1,562 1,180 1,050 Depreciation and amortization 446 335 196 Other expenses 5,366 2,636 1,071 € 51,740 € 31,557 € 20,635 5.5 Selling, general and administrative expenses Year Ended December 31, (in thousands of €) 2017 2016 2015 Personnel expense € 6,745 € 3,256 € 1,607 Consulting fees 3,289 2,563 2,395 Supervisory board 621 446 165 Office costs 1,793 746 758 € 12,448 € 7,011 € 4,925 5.6 Personnel expenses The personnel expenses which exclude consultants mentioned above are as follows: Year Ended December 31, (in thousands of €) 2017 2016 2015 Short ‑ term employee benefits—Salaries € 12,149 € 8,527 € 5,192 Short ‑ term employee benefits—Social Security 1,504 1,027 802 Post ‑ employment benefits 291 175 207 Termination benefits 8 86 124 Share ‑ based payment 3,985 2,849 1,945 Employer social security contributions stock options 5,281 436 — € 23,218 € 13,100 € 8,270 The post‑employment benefits relate to the pension plans the Company has in place for its employees. The number of full‑time equivalents (FTE) employees by department is presented below: Year Ended December 31, Number of FTE 2017 2016 2015 Research and development 56.8 46.9 31.4 General and administrative 14.7 9.9 5.8 71.5 56.8 37.2 These FTE’s are working outside the Netherlands. 5.7 Operating leases Operating lease payments recognized as an expense in the statement of profit and loss and other comprehensive income amount to €1.2 million for the year ended December 31, 2017 (of which €0.3 million is presented as research and development expenses and €0.9 million is included under selling, general and administrative expenses) versus €0.9 million for the year ended December 31, 2016 (of which €0.2 million is presented as research and development expenses and €0.7 million is included under selling, general and administrative expenses). The Group’s future operating lease commitments are as follows: Year Ended December 31, Operating lease commitments (in thousands of €) 2017 2016 2015 Less than 1 year € 1,028 € 915 € 630 1–3 years 465 1,159 1,130 3–5 years 33 24 142 More than 5 years — — — € 1,526 € 2,098 € 1,902 The Group has a lease plan for the company’s cars with maturity dates up to four years. For the laboratory and office space, the Group has a lease agreement in Zwijnaarde Belgium for a period of nine years starting from April 1, 2016, with the possibility to terminate the lease by giving a notice of at least twelve months in advance at the occasion of the third and sixth anniversary of the agreement. For its offices in the Netherlands and the United States of America, the Company has a lease agreement renewable on an annual base. No purchase options were in effect under the lease agreements described above. 5.8 Financial result and exchange gains/(losses) Year Ended December 31, (in thousands of €) 2017 2016 2015 Interest income on bank deposits € 165 € 61 € 76 Net gains on investments at FVTPL 210 12 36 Realized gain on non-current financial assets 875 — — Financial income 1 250 73 112 Exchange gains/(losses) (5 797) (31) 181 The exchange losses of €5.8 million for the year ended December 31, 2017 was primarily attributable to unrealized exchange rate losses on our cash and current financial assets position in USD due to the unfavorable fluctuation of the USD exchange rate over the period. 5.9 Income taxes The income tax expense for the year can be reconciled to the accounting loss as follows: Year Ended December 31, (in thousands of €) 2017 2016 2015 Loss before taxes (27,479) (21,374) (15,312) Income tax calculated at 25% 6,870 5,344 3,828 Effect of expenses that are not deductible in determining taxable results (1,141) (755) (568) Effect of stock issue expenses that are not deductible in determining taxable results 5,754 462 — Effect of concessions (R&D incentives and grants) 453 463 759 Effect of tax losses carried forward not recognized (Netherlands) — (5,551) (3,601) Effect of usage of tax losses carried forward not previously recognized (Netherlands) 19,378 — — Effect of tax losses carried forward not recognized (Belgium) (27,413) — (301) Effect of usage of tax losses carried forward not previously recognized (Belgium) — 195 — Effect of change in corporate tax rate on deferred tax asset not previously recognized (Belgium) 373 — — Effect of different tax rates in jurisdictions in which the company operates (517) (180) (122) Deferred tax asset other than loss carryforwards not recognized (4,363) — — Other 9 22 5 Income tax expense recognized in the consolidated statement of profit and loss € (597) € — € — The tax rate used for the 2017, 2016 and 2015 reconciliations above is the corporate income tax rate of 25% payabale by corporate entities in the Netherlands. The unrecognized deferred tax asset on deductible temporary differences and unused tax losses amounts to €28.4 million on December 31, 2017 compared to €21.0 million on December 31, 2016. The reduction of the Belgian corporation tax rate from 33.99% to 29.58% as of 2018 and subsequently to 25% as of 2020 was substantively enacted on December 25, 2017 and will be effective from January 1, 2018. As a result, the relevant unrecognized deferred tax balances have been remeasured. Deferred tax have been measured using the effective rate that will apply in Belgium (25%). The unrecognized deferred tax asset on unused tax credits amounts to €0.01 million on December 31, 2017 compared to €6.6 million on December 31, 2016. The Group has unused tax loss carried forwards for an amount of €113.6 million on December 31, 2017, of which €1.3 million will expire in 2026. This, combined with other temporary differences, resulted in a net deferred tax asset position. Due to the uncertainty surrounding the Group’s ability to realize taxable profits in the near future, the Company did not recognize any deferred tax assets. The Group has transferred the legal ownership of its intellectual property rights from the Dutch argenx SE to its wholly owned Belgian subsidiary, argenx BVBA. The tax consequences of this transaction for argenx SE have been preliminarily agreed with the Dutch tax authorities on March 23, 2017 and relate to: (i) the arm’s length compensation for the Company being fixed at €79.9 million; and (ii) the right to offset the full amount of the Company’s tax loss carry forward of €77.5 million against this compensation. The restructuring is estimated to result in a taxable amount for argenx SE of €2.3 million subject to an exit tax in the Netherlands at a rate of 25%, i.e. , an estimated tax payable amount of €0.6 million for the year ended December 31, 2017. For the same business restructuring, there is also a tax ruling pending in Belgium. If approved as currently proposed, the restructuring is estimated to result in additional tax deductible costs for argenx BVBA for an amount of up to €79.9 million (see note 4.15). 5.10 Loss per share Year Ended December 31, (in thousands of €) 2017 2016 2015 Loss of the year € (28,076) € (21,374) € (15,312) Weighted average number of shares outstanding 24,609,536 18,820,612 15,734,007 Basic and diluted loss per share (in €) € (1.14) € (1.14) € (0.97) Earnings/losses per ordinary share are calculated by dividing the loss for the period by the weighted average number of ordinary shares during the year. As the Group is suffering operating losses, options have an anti‑dilutive effect. As such, there is no difference between basic and diluted earnings/losses per ordinary share. There are no other instruments that could potentially dilute earnings per ordinary share in the future.

Financial instruments and finan

Financial instruments and financial risk management	12 Months Ended
	Dec. 31, 2017
Financial instruments and financial risk management
Financial instruments and financial risk management	6. Financial instruments and financial risk management 6.1 Overview of financial instruments At December 31,2017 At December 31,2016 At December 31,2015 Carrying Carrying Carrying (in thousands of €) amount Fair value amount Fair value amount Fair value Non ‑ current financial assets € 1 € 1 € 1 € 1 € 1 € 1 Current financial assets 168,907 168,907 6,831 6,831 6,813 6,813 Financial assets 168,908 168,908 6,832 6,832 6,814 6,814 Other non-current assets 125 125 — — — — Trade and other receivables 2,842 2,842 1,970 1,970 1,356 1,356 Cash and cash equivalents 190,867 190,867 89,897 89,897 35,514 35,514 Non ‑ current restricted cash 256 256 1,149 1,149 — — Current restricted cash 1,692 1,692 787 787 — — Loans and receivables 195,782 195,782 93,803 93,803 36,870 36,870 Total financial assets 364,690 364,690 100,635 100,635 43,684 43,684 Provision for employee benefits 25 25 1 1 — — Trade and other payables 15,285 15,285 12,191 12,191 4,543 4,543 Financial liabilities at amortized cost 15,310 15,310 12,192 12,192 4,543 4,543 Total financial liabilities € 15,310 € 15,310 € 12,192 € 12,192 € 4,543 € 4,543 Financial assets: · non‑current financial assets: please refer to note 4.3 for more information (level 3). · current financial assets included: - collective investment funds nominated in € and $ that are not considered as cash equivalents and of which the underlying investments include bonds and other international debt securities. The average credit rating of the underlying instruments is BBB or higher. The maximum exposure to credit risk is the carrying value at reporting date. These investment funds are recognized at fair value in the Group’s financial statements (level 1). The fair value corresponds to the quoted market price and can therefore be classified as a level 1 fair value measurement. The net asset value (NAV) of the funds is available on a daily basis. Any difference between amounts invested and fair value at reporting date is booked in Profit & Loss; and - a USD term account with a maturity of six months. This term account is held at a bank which is independently rated with a minimum rating of ‘A’. Loans and receivables: · other non-current assets: please refer to note 4.3 for more information · trade and other receivables: please refer to note 4.7 for more information and to note 6.3 below for the credit risk · cash and cash equivalents: please refer to note 4.10 for more information and to note 6.3 below for the credit risk · restricted cash: please refer to note 4.6 for more information Financial liabilities: Due to the current nature of the financial liabilities, the nominal value of all financial liabilities presented above approximates their fair value. Fair value hierarchy: The Group carried the following assets at fair value on December 31, 2017, 2016 and 2015 respectively: At December 31,2017 (in thousands of €) Level 1 Level 2 Level 3 Non-current financial assets € € € 1 Current financial assets 168,907 Assets carried at fair value € 168,907 € — € 1 At December 31,2016 (in thousands of €) Level 1 Level 2 Level 3 Non-current financial assets € € € 1 Current financial assets 6,831 Assets carried at fair value € 6,831 € — € 1 At December 31,2015 (in thousands of €) Level 1 Level 2 Level 3 Non-current financial assets € € € 1 Current financial assets 6,813 Assets carried at fair value € 6,813 € — € 1 All assets and liabilities for which fair value was measured or disclosed in the financial statements are categorized within the fair value hierarchy, described as follows, based on the lowest level input that is significant to the fair value measurement as a whole: · Level 1—Quoted (unadjusted) market prices in active markets for identical assets or liabilities · Level 2—Valuation techniques for which the lowest level input that is significant to the fair value measurement is directly or indirectly observable · Level 3—Valuation techniques for which the lowest level input that is significant to the fair value measurement is unobservable During the disclosed calendar year no transfers occurred between the applicable categories. Given the insignificant value of the Group’s assets categorized as Level 3, the additional Level 3 disclosures have been omitted. 6.2 Capital risk The Group manages its capital to ensure that it will be able to continue as a going concern. The capital structure of the Company consists of equity attributed to the holders of equity instruments of the Company, such as capital, reserves and accumulated losses as mentioned in the consolidated statement of changes in equity. The Group makes the necessary adjustments in the light of changes in the economic circumstances, risks associated to the different assets and the projected cash needs of the current and projected research activities. On December 31, 2017 cash and cash equivalents amounted to €190.9 million and total capital amounted to €433.7 million. The current cash situation and the anticipated cash generation are the most important parameters in assessing the capital structure. The Group’s objective is to maintain the capital structure at a level to be able to finance its activities for at least twelve months. Cash income from existing and new partnerships is taken into account and, if needed and possible, the Company can issue new shares or enter into financing agreements. 6.3 Credit risk Credit risk refers to the risk that a counterparty will default on its contractual obligations resulting in financial loss to the Group. The Group has adopted a policy of only dealing with creditworthy counterparties and obtaining sufficient collateral, where appropriate, as a means of mitigating the risk of financial loss from defaults. Concentrations in credit risk are determined based on an analysis of counterparties and their importance on the overall outstanding contractual obligations at year end. The Group has a limited number of collaboration partners and therefore has a significant concentration of credit risk. However, it has policies in place to ensure that credit exposure is kept to a minimum and significant concentrations of credit exposure are only granted for short periods of time to high credit quality collaboration partners. Credit exposure is controlled by counterparty limits that are reviewed and approved by management annually. Cash and cash equivalents and short‑term deposits are invested with several highly reputable banks and financial institutions. The Group holds its cash and cash equivalents mainly with different banks which are independently rated with a minimum rating of ‘A-’. The Group also holds short term investment funds in the form of money market funds with a recommended investment horizon of 6 months or shorter but with a low historical volatility. These money market funds are highly liquid investments, can be readily convertible into a known amount of cash. Since they are a basket of funds there is no individual credit risk involved. The average credit rating of the underlying instruments for the investment funds is BBB or higher. The maximum credit risk, to which the Group is theoretically exposed as at the balance sheet date, is the carrying amount of the financial assets. At the end of the reporting period no financial assets were past due, consequently no financial assets were subject to impairment. 6.4 Liquidity risk The Group manages liquidity risk by maintaining adequate reserves, by continuously monitoring forecast and actual cash flows, and by matching the maturity profiles of financial assets and liabilities. The Group’s main sources of cash inflows are obtained through capital increases and collaboration agreements. This cash is invested in savings accounts, term accounts and short term investment funds in the form of money market funds. These money market funds represent the majority of the Group’s available sources of liquidity however since all of these are immediately tradable and convertible in cash they have a limited impact on the liquidity risk. All financial liabilities (principally trade and other payables as disclosed in note 6.1) have a maturity within 3 months unless otherwise disclosed in these financial statements. 6.5 Interest rate risk The Group is currently not exposed to significant interest rate risk. The only interest‑bearing financial assets are cash at banks on deposit and term accounts. Given the short‑term nature of these investments the sensitivity towards interest rate fluctuations is deemed not to be significant. For the year ended December 31, 2017, if applicable interest rates would increase/decrease by 25 basis points this would have a positive/negative impact of €0.3 million (compared to €0.1 million for the year ended December 31, 2016 and 2015). 6.6 Foreign exchange risk The Group undertakes transactions denominated in foreign currencies; consequently, exposures to exchange rate fluctuations arise. The Group is mainly exposed to the US Dollar and GBP. The net exposure to exchange differences of the monetary assets (being cash and cash equivalents) of the Group at the end of the reporting period are as follows: At December 31, (in thousands of €) 2017 2016 2015 USD 147,169 624 345 GBP 406 — — On December 31, 2017, if the USD/EUR exchange rate would have increased/decreased by 10%, this would have had a negative/positive impact of €13.38 million (compared to €0.06 million on December 31, 2016). On December 31, 2017, if the GBP/EUR exchange rate would have increased/decreased by 10%, this would have had no significant impact. 10% is the sensitivity rate used when reporting foreign currency risk internally to key management personnel and represents management’s assessment of the reasonably possible change in foreign exchange rates. The sensitivity analysis includes only outstanding foreign currency denominated monetary items and adjusts their translation at the period end for a 10% change in foreign currency rates.

Other disclosures

Other disclosures	12 Months Ended
	Dec. 31, 2017
Other disclosures
Other disclosures	7. Other disclosures 7.1 Related party transactions Amongst the shareholders of the Company, there are minority investors and venture capitalist funds which individually do not hold a significant influence on the Company. Balances and transactions between the Company and its subsidiaries, which are related parties of the Company, have been eliminated on consolidation and are not disclosed in this note. There were no significant transactions with related parties during the period, other than compensation of key management personnel. Compensation of key management personnel Key management personnel of the Company is composed of the Chief Executive Officer, the Chief Financial Officer, the Chief Scientific Officer, the Chief Development Officer, the Chief Medical Officer, the Senior Vice President of Business Development and the General Counsel. The remuneration of the key management personnel during the year was as follows: Year Ended December 31, (in thousands of €) 2017 2016 2015 Short term employee benefits € 3,126 € 1,832 € 1,482 Post employment benefits 115 125 59 Termination benefits — — 124 Share‑based payment(1) 12,041 2,261 1,761 Employer social security contributions stock options(2) 3,073 436 — € 18,355 € 4,654 € 3,426 (1) Amount shown represents the expenses, recorded with respect to the option awards granted in the year, measured using the Black Scholes formula. (2) The Group incurs employer social security costs with respect to the option awards granted to certain members of the executive management. The amount of employer social security costs depends on the actual economic value realized and therefore varies based on our stock price. At each reporting date, the Group makes a calculation of the exposure. Remuneration of the executive directors The tables below show the remuneration received by executive directors for the years ended December 31, 2017, 2016 and 2015 (in €). Eric Castaldi served as a member of our board until April 26, 2017. A scenario analysis based on best practice clause II.2.1. of the Dutch Corporate Governance Code was made. Both executive directors have met each of their bonus targets previously established by the non-executive directors during the years ended December 31, 2017, 2016 and 2015 and the full bonus was granted in the same year. Pension 2015 Base salary Bonus contributions Social security costs ESOP (1) Other (2) Total Tim Van Hauwermeiren 217,260 103,298 8,690 8,760 201,248 9,210 548,466 Eric Castaldi 222,159 75,075 62,097 133,621 185,464 — 678,416 Total 439,419 178,373 70,787 142,381 386,712 9,210 1,226,882 Pension 2016 Base salary Bonus contributions Social security costs ESOP (1) Other (2) Total Tim Van Hauwermeiren 253,284 101,314 11,929 10,284 488,020 9,184 874,015 Eric Castaldi 235,952 82,583 84,972 136,124 786,035 — 1,325,666 Total 489,236 183,897 96,901 146,408 842,597 9,184 1,768,223 Pension 2017 Base salary Bonus contributions Social security costs ESOP (1) Other (2) Total Tim Van Hauwermeiren 303,941 301,635 14,315 9,459 2,968,195 9,601 3,607,146 Eric Castaldi 271,344 173,284 62,335 254,732 4,089,209 14,979 4,865,883 Total 575,285 474,919 76,650 264,191 7,057,404 24,580 8,473,029 (1) Amount shown represents the expenses, recorded with respect to the option awards granted in the year, measured using the Black Scholes formula, and the employer social security costs with respect to the option awards granted to certain members of the executive management. The amount of employer social security costs depends on the actual economic value realized and therefore varies based on our stock price. At each reporting date, the Group makes a calculation of the exposure. (2) Consists of costs attributable to the lease of a company car and employer-paid medical insurance premiums. The table below shows the number of stock options granted to the executive directors during the years ended December 31, 2017, 2016 and 2015 and their exercise price equal to the fair market value upon date of grant, and the stock options exercised during 2017, 2016 and 2015. 2015 ESOPs Term Exercise price Exercised Tim Van Hauwermeiren 30,600 10 years 9.47 — Eric Castaldi 28,200 10 years 9.47 — Total 58,800 — 2016 ESOPs Term Exercise price Exercised Tim Van Hauwermeiren 50,000 10 years 11.47 30,600 10 years 14.13 3.95 53,092 2.44 72,200 Eric Castaldi 28,200 10 years 11.47 28,200 10 years 14.13 Total 137,000 125,292 2017 ESOPs Term Exercise price Exercised Tim Van Hauwermeiren 80,000 10 years 21.17 2.44 65,380 Eric Castaldi 43,200 10 years 21.17 Total 123,200 65,380 The table below shows the stock options held at the start of the year ended December 31, 2017, the stock options granted to executive directors which have vested during the year ended December 31, 2017 and the stock options to vest in the years until 2020. Total Total options options held on options options held on Options Options Options Options Options January 1, granted in exercised in December 31, vested Exercise vested in Exercise to vest Exercise to vest Exercise to vest Exercise Name 2017 2017 2017 2017 until 2016 price 2017 price 2018 price 2019 price 2020 price Tim Van Hauwermeiren 281,580 80,000 (65,380) 296,200 70,000 7.17 35,000 10,200 9.47 10,200 10,200 26,389 16,667 6,944 10,200 10,200 10,200 26,667 21.17 26,666 21.17 26,667 21.17 Eric Castaldi 230,607 43,200 — 273,807 72,007 2.44 9,000 2.44 43,333 7.17 21,667 7.17 9,400 9.47 9,400 9.47 9,400 9.47 14,883 9,400 11.47 3,917 11.47 9,400 9,400 14.13 9,400 14.13 14,400 21.17 14,400 21.17 14,400 21.17 The table below shows the remaining term of the options held by the executive directors on December 31, 2017. Name Number of options Remaining term at December 31, 2017 (rounded up) Tim Van Hauwermeiren 105,000 7.0 years 30,600 8.0 years 50,000 8.5 years 30,600 9.0 years 80,000 10.0 years Eric Castaldi 60,970 6.5 years 85,037 7.0 years 28,200 8.0 years 28,200 8.5 years 28,200 9.0 years 43,200 10.0 years Stock options are granted to the executive directors by the Board based on the recommendation of the Remuneration and Nomination Committee and the option allocation scheme established by the Board pursuant to the argenx Employee Stock Option Plan. Remuneration of non-executive directors The following table sets forth the information regarding the compensation earned by our non‑executive directors during the years ended December 31, 2017, 2016 and 2015: 2017 2016 2015 Peter Verhaeghe € 77,500 € 55,000 € 35,000 John Paul de Koning — — — Christina Takke NA NA — David L Lacey 50,000 45,930 45,651 Werner Lanthaler 55,000 45,000 35,000 Pamela Klein 42,500 35,000 NA Don Debethizy 52,500 43,000 27,617 A.A. Rosenberg 42,500 — — Total € 320,000 € 223,930 € 143,268 The table below shows the number of stock options granted to the non-executive directors during the years ended December 31, 2017, 2016 and 2015 and their exercise price, based on the 30 day average stock price prior to their date of grant, and the stock options exercised during the years ended December 31, 2015 and 2016. 2015 ESOPs Term Exercise price Exercised Don Debethizy 15,000 10 years 11.44 Total 15,000 — 2016 ESOPs Term Exercise price Exercised Peter Verhaeghe 10,000 10 years 11.38 David L Lacey 10,000 10 years 11.38 Werner Lanthaler 10,000 10 years 11.38 Don Debethizy 10,000 10 years 11.38 Pamela Klein 10,000 10 years 11.38 A.A. Rosenberg (1) 15,000 10 years 14.13 Total 50,000 — (1) 15,000 stock options were granted to Msc. A.A. Rosenberg in December 2016 in his capacity of consultant to the company. Msc. A.A. Rosenberg was appointed as a member of our board of directors at our Annual General Meeting in April 2017. 2017 ESOPs Term Exercise price Exercised David L Lacey 15,000 10 years 21.17 Total 15,000 — The table below shows the stock options held at the start of the year ended December 31, 2017 and the stock options granted to the non‑executive directors which have vested during the year ended December 31, 2017, as well as the stock options to vest in the years ending December 31, 2018, December 31, 2019 and December 31, 2020 (in number of stock options), and the respective exercise price of such stock options: Total Total Options Options Options options Options options Options Options to to to held on granted held on vested vested vest vest vest January 1, in December 31, until Exercise in Exercise in Exercise in Exercise in Exercise Name 2017 2017 2017 2016 price 2017 price 2018 price 2019 price 2020 price Peter Verhaeghe 34,585 — 34,585 11,626 € 2.44 7,959 € 3.95 3,333 € 7.17 1,667 € 7.17 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 David L. Lacey 29,443 15,000 44,443 6,643 € 2.44 8,533 € 7.17 4,267 € 7.17 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 5,000 € 21.17 5,000 € 21.17 5,000 € 21.17 Werner Lanthaler 29,416 — 29,416 12,814 € 2.44 1,602 € 2.44 3,333 € 7.17 1,667 € 7.17 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 J. Donald deBethizy 25,000 — 25,000 7,500 € 11.44 5,000 € 11.44 2,500 € 11.44 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 Pamela Klein 25,000 — 25,000 7,500 € 11.44 5,000 € 11.44 2,500 € 11.44 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 A.A. Rosenberg 15,000 — 15,000 — € 14.13 5,000 € 14.13 5,000 € 14.13 5,000 € 14.13 The table below shows the remaining term of the stock options held by the non‑executive directors on December 31, 2017. Remaining term on Number of December 31, 2017 Name stock options (rounded up) Peter K.M. Verhaeghe 3,650 2.5 years 2,340 3.0 years 5,560 5.5 years 3,181 6.0 years 9,854 7.0 years 10,000 8.5 years David L. Lacey 3,180 5.5 years 1,818 6.0 years 14,445 7.0 years 10,000 8.5 years 15,000 10.0 years Werner Lanthaler 10,850 6.0 years 8,566 7.0 years 10,000 8.5 years J. Donald deBethizy 15,000 7.5 years 10,000 8.5 years Pamela Klein 15,000 7.5 years 10,000 8.5 years A.A. Rosenberg 15,000 9.0 years Stock options are granted to the non-executive directors by the Board based on the recommendation of the Remuneration and Nomination Committee, and the option allocation scheme established by the board pursuant to the argenx Employee Stock Option Plan. No stock options were exercised by non‑executive directors during the year ended December 31, 2017, and no corresponding shares were issued in relation thereto. 7.2 Contingencies The Group is currently not facing any outstanding claims or litigations that may have a significant adverse impact on the Group’s financial position. As described in note 5.2 the Group has received several types of government grants which are granted subject to a certain number of conditions that need to be met at grant date and in the future. The Group recognizes grant income from Belgian and Flemish grant bodies when all contractual conditions are met. These government institutions may however subsequently perform an audit which may result in a (partial) claw back of the grant. The Group deems that the claw back risk is remote in view of the continuous monitoring of the contractual conditions. Currently the Group has fulfilled all the existing conditions relating to the recognition of its grant income. Contracts with these grant bodies also typically include clauses that define the need for future validation of the project results after completion of the initial grant term during which the subsidized expenses or investments have been incurred and for which the grant was earned. Should this validation not occur or be deemed inadequate, the grant bodies have the right to reclaim funds previously granted. 7.3 Commitments At balance sheet date, there were no commitments signed for the acquisition of property, plant and equipment or intangible assets. In July 2017, the Group signed a letter of intent with its drug substance manufacturing contractor, Lonza Sales AG, or Lonza, related to the biologics license application for ARGX‑113. The total commitment under this letter of intent amounts to a minimum spend of £5.0 million before the end of calendar year 2018, of which the Group paid £1.0 million upon signature. In December 2017, the Group amended one of its manufacturing agreements with Lonza. This amendment expands the scope of Lonza’s services with additional services for ARGX‑113 to be performed at the Lonza facility in Tuas, Singapore. These services relate to the start‑up of Lonza Singapore as a potential future commercial manufacturing site. Pursuant to this amendment, the Group has additional contractual obligations in the aggregate amounts of approximately $9.3 million, with payments beginning in January 2018. In addition to the obligations for ARGX‑113, the Group also has contractual obligations for ARGX‑110 for approximately £0.9 million, with payments beginning by the third quarter of 2018. For information on the operating leases see note 5.7. 7.4 Audit Fees The following auditors’ fees were expensed in the income statement: Year Ended December 31, Fees 2017 2016 2015 in thousands of € Audit fees(1) € 205 € 85 € 70 Audit-related fees 698 65 35 Tax and other services(2) — 2 3 Total € 903 € 152 € 108 (1) Audit services performed by Deloitte Accountants B.V. as the external auditor referred to in Section 1 of the Dutch Accounting Firms Oversight Act (Wta) as well as by the Deloitte network. (2) Tax and other services performed conducted by the Deloitte network. 7.5 Overview of consolidation scope The parent company argenx SE is domiciled in the Netherlands. The Company, argenx SE, has one subsidiary, argenx BVBA, based in Belgium. Since October 2017, argenx BVBA has also one subsidiary, argenx US Inc., based in the United States of America. Details of the Group’s consolidated entities at the end of the reporting period are as follows: List of consolidated companies. Name Registration number Country Participation Main activity argenx SE COC 24435214 The Netherlands 100.00 % Holding company argenx BVBA Belgium 100.00 % Biotechnical research on drugs and pharma processes argenx US, Inc. 36-4880497 USA 100.00 % Pharmaceuticals and pharmacy supplies merchant wholesalers 7.6 Events after the balance sheet date On March 16, 2018, the Company has been awarded a €2.5 million VLAIO grant to identify novel therapeutic antibodies. This grant will be used to fund research of novel targets involved in regulation of locally-released TGF-ß, a protein active in immunosuppression. On March 22, 2018, the Company announced the expansion of its pipeline with addition of complement targeted ARGX-117 for treatment of severe autoimmune diseases. ARGX-117 has the potential to have synergistic effect with the lead autoimmune compound ARGX-113.

Significant accounting polici14

Significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2017
Significant accounting policies
Statement of compliance and basis of preparation	2.1 Statement of compliance and basis of preparation The consolidated financial statements are prepared in accordance with the International Financial Reporting Standards (IFRS), issued by the International Accounting Standards Board (IASB) and the interpretations issued by the IASB’s International Financial Reporting Interpretation Committee. The consolidated financial statements provide a general overview of the Group’s activities and the results achieved. They present fairly the entity’s financial position, its financial performance and cash flows, on a going concern basis. The accounting policies described in Note 2 to our consolidated financial statements have been applied in preparing the consolidated financial statements as of and for the year ended December 31, 2017 and for the comparative information as of and for the years ended December 31, 2016 and 2015. The preparation of consolidated financial statements in conformity with IFRS, issued by the IASB, requires the use of certain critical accounting estimates. It also requires management to exercise its judgment in the process of applying the Group’s accounting policies. The areas involving a higher degree of judgment or complexity, or areas where assumptions and estimates are significant to the consolidated financial statements are disclosed in Note 3. The principal accounting policies applied in the preparation of the above financial statements are set out below. All amounts are presented in thousands of euro, unless otherwise indicated, rounded to the nearest € ‘000. The consolidated financial statements have been approved for issue by the Company’s Board of Directors (the Board) on February 27, 2018.
Basis of consolidation	2.2 Basis of consolidation The consolidated financial statements include the financial statements of the Company and entities controlled by the Company (its subsidiaries). Control is achieved when the Company: • has power over the investee; • is exposed, or has rights, to variable returns from its involvement with the investee; and • has the ability to use its power to affect its returns. The Company reassesses whether or not it controls an investee if facts and circumstances indicate that there are changes to one or more of the three elements of control listed above. Consolidation of a subsidiary begins when the Company obtains control over the subsidiary and ceases when the Company loses control of thesubsidiary. Income and expenses of subsidiaries acquired or disposed of during the year are included in the consolidated statement of profit and loss and other comprehensive income from the effective date of acquisition and up to the effective date of disposal, as appropriate. Total comprehensive income of subsidiaries is attributed to the owners of the Company and to the non‑controlling interests even if this results in the non‑controlling interests having a deficit balance. When necessary, adjustments are made to the financial statements of subsidiaries to bring their accounting policies into line with those used by other members of the Group. All intra‑group transactions, balances, income and expenses are eliminated in full on consolidation.
Foreign currency transactions	2.3 Foreign currency transactions Functional and presentation currency The financial statements are presented in euro (€), which is the Group’s presentation currency and the Company’s functional currency. Transactions and balances Transactions in foreign currencies are translated at the exchange rate ruling at the date of the transaction. Monetary assets and liabilities denominated in foreign currencies are translated at the exchange rate ruling at the reporting date. Foreign exchange differences arising on translation are recognized in the statement of profit and loss and other comprehensive income. Non‑monetary assets and liabilities denominated in foreign currencies are translated at the foreign exchange rate ruling at the date of the transaction. Financial statements of foreign entities For foreign entities using a different functional currency than the euro: · Non-monetary assets and liabilities are converted to the euro at the historical exchange rate at the date of the transaction. · Monetary assets and liabilities are converted to the euro using the exchange rate on the reporting date. · Income statements are converted to the euro at the annual average exchange rate. · Equity items are converted to the euro at the historical exchange rate for the date of the transaction. Translation differences resulting from the conversion of equity into euro using the rate at the end of the reporting period are recognized as translation differences under equity. Translation differences remain in equity up to the disposal of the company. In case of disposal, the deferred cumulative amount included in equity is included in the results for the foreign activity in question.
Intangible assets	2.4 Intangible assets Intangible assets with finite useful lives that are acquired separately are carried at cost less accumulated amortization and accumulated impairment losses. Amortization is recognized on a straight‑line basis over their estimated useful lives. The estimated useful life and amortization method are reviewed at the end of each reporting period, with the effect of any changes in estimate being accounted for on a prospective basis. Intangible assets with indefinite useful lives that are acquired separately are carried at cost less accumulated impairment losses. Intangible assets related to software are amortized over 3 years. Expenditure on research activities is recognized as an expense in the period in which it is incurred. An internally‑generated intangible asset arising from development (or from the development phase of an internal project) is recognized if, and only if, all of the following have been demonstrated: · the technical feasibility of completing the intangible asset so that it will be available for use or sale; · the intention to complete the intangible asset and use or sell it; · the ability to use or sell the intangible asset; · how the intangible asset will generate probable future economic benefits; · the availability of adequate technical, financial and other resources to complete the development and to use or sell the intangible asset; and · the ability to measure reliably the expenditure attributable to the intangible asset during its development. The amount initially recognized for internally‑generated intangible assets is the sum of the expenditure incurred from the date when the intangible asset first meets the recognition criteria listed above. Where no internally‑generated intangible asset can be recognized, development expenditures are recognized in the statement of profit and loss and other comprehensive income in the period in which they are incurred. Due to uncertainties inherent to the development and registration with the relevant healthcare authorities of its products, the Company estimates that the conditions for capitalization are not met until the regulatory procedures required by such healthcare authorities have been finalized. The Company currently does not own products that have been approved by the relevant healthcare authorities. As such, research expenditures not satisfying the above criteria and expenditures in the research phase of internal projects are recognized in the statement of profit and loss and other comprehensive income as they are incurred. Subsequent to initial recognition, internally‑generated intangible assets are reported at cost less accumulated amortization and accumulated impairment losses, on the same basis as intangible assets that are acquired separately. An intangible asset is derecognized either on disposal or when no future economic benefits are expected from its use. Gains or losses arising from derecognition of an intangible asset, measured as the difference between the net disposal proceeds and the carrying amount of the asset, are recognized in profit or loss when the asset is derecognized.
Property, plant and equipment	2.5 Property, plant and equipment Items of property, plant and equipment held for use in the production or supply of goods or services, or for administrative purposes, are stated in the statement of financial position at their cost, less accumulated depreciation and accumulated impairment losses. The cost comprises the initial purchase price plus other direct purchase costs (such as non‑refundable tax and transport). Depreciation is recognized as from acquisition date onwards (unless asset is not ready for use) so as to write off the cost or valuation of assets (other than freehold land and properties under construction) less their residual values over their useful lives, using the straight‑line method. The estimated useful lives, residual values and depreciation method are reviewed at the end of each reporting period, with the effect of any changes in estimate accounted for on a prospective basis. Unless revised due to specific changes in the estimated useful life, annual depreciation rates are as follows: · Office and lab equipment: 3–5 years · IT equipment: 3 years An item of property, plant and equipment is derecognized upon disposal or when no future economic benefits are expected to arise from the continued use of the asset. Any gain or loss arising on the disposal or retirement of an item of property, plant and equipment is determined as the difference between the sales proceeds and the carrying amount of the asset and is recognized in profit or loss.
Leases	2.6 Leases Operating lease payments are recognized as an expense on a straight‑line basis over the lease term, except where another systematic basis is more representative of the time pattern in which economic benefits from the leased asset are consumed. Contingent rentals arising under operating leases are recognized as an expense in the period in which they are incurred. In the event that lease incentives are received to enter into operating leases, such incentives are recognized as a liability. The aggregate benefit of incentives is recognized as a reduction of rental expense on a straight‑line basis, except where another systematic basis is more representative of the time pattern in which economic benefits from the leased asset are consumed.
Impairment of assets	2.7 Impairment of assets At the end of each reporting period, the Company reviews the carrying amounts of its tangible and intangible assets to determine whether there is any indication that those assets have suffered an impairment loss. If any such indication exists, the recoverable amount of the asset is estimated in order to determine the extent of the impairment loss (if any). Where it is not possible to estimate the recoverable amount of an individual asset, the Company estimates the recoverable amount of the cash‑generating unit to which the asset belongs. Where a reasonable and consistent basis of allocation can be identified, corporate assets are also allocated to individual cash‑generating units, or otherwise they are allocated to the smallest group of cash‑generating units for which a reasonable and consistent allocation basis can be identified. Intangible assets with indefinite useful lives and intangible assets not yet available for use are tested for impairment at least annually, and whenever there is an indication that the asset may be impaired. Recoverable amount is the higher of fair value less costs to sell and value in use. In assessing value in use, the estimated future cash flows are discounted to their present value using a pre‑tax discount rate that reflects current market assessments of the time value of money and the risks specific to the asset for which the estimates of future cash flows have not been adjusted. If the recoverable amount of an asset (or cash‑generating unit) is estimated to be less than its carrying amount, the carrying amount of the asset (or cash‑generating unit) is reduced to its recoverable amount. An impairment loss is recognized immediately in profit or loss. Where an impairment loss subsequently reverses, the carrying amount of the asset (or a cash‑generating unit) is increased to the revised estimate of its recoverable amount, but so that the increased carrying amount does not exceed the carrying amount that would have been determined had no impairment loss been recognized for the asset (or cash‑generating unit) in prior years. A reversal of an impairment loss is recognized immediately in profit or loss.
Financial assets	2.8 Financial assets Financial assets are classified into the following specified categories: financial assets ‘at fair value through profit or loss’ (FVTPL), ‘held-to-maturity’ investments, ‘available-for-sale’ (AFS) financial assets and ‘loans and receivables.’ The classification depends on the nature and purpose of the financial assets and is determined at the time of initial recognition. Management determines the classification at the time of the purchase and re‑evaluates such designation at each subsequent balance sheet date. Purchase and sale of financial assets are recognized on the settlement date, which is the date an asset is delivered to or by the Group. The cost of financial assets includes transaction costs. The carrying amounts of all financial assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount is impaired. If objective evidence exists that a financial asset or group of financial assets is impaired, the amount of the impairment loss is calculated as the difference between the carrying amount of the financial asset and the present value of estimated future cash flows, discounted at the original effective interest rate ( i.e. , the effective interest rate computed at initial recognition of these financial assets). The resulting impairment loss is immediately recognized in net finance costs. An impairment loss on financial assets is reversed if, in a subsequent period, the amount of the impairment loss decreased and this decrease can be related objectively to an event occurring after the impairment loss was recognized. Such reversal is immediately recognized in net finance costs.
Trade and other receivables	2.9 Trade and other receivables Trade and other receivables are initially recognized at fair value and are subsequently carried at amortized cost using the effective interest method. A provision for impairment of trade and other receivables is established when there is objective evidence that the Company will not be able to collect all amounts due according to the original terms of the receivables.
Research and development incentive receivables	2.10 Research and development incentive receivables Since the Company carries out extensive research and development activities, it benefits from various research and development incentives from certain governmental agencies. These research and development incentives generally aim to partly reimburse approved expenditures incurred in research and development efforts of the Company and are credited to the consolidated statement of profit and loss and other comprehensive income, in other operating income, when there is reasonable assurance that the research and development incentives are receivable. Non‑current research and development incentives receivables are discounted over the period until maturity date according to the appropriate discount rates.
Cash and cash equivalents	2.11 Cash and cash equivalents Cash and cash equivalents includes cash in hand, deposits held at call with banks and other short term highly liquid investments with original maturities of three months or less and with an insignificant risk of changes in value. Bank overdrafts, if any, are shown within borrowings in current liabilities on the statement of financial position. Cash balances that are not available for use by the Company are presented as “Restricted cash” in the statement of financial position. For the purpose of the statements of cash flows, cash and cash equivalents includes cash on hand and deposits held at call or short term maturity with banks (three months or less with insignificant risk of changes in value).
Shareholder’s equity	2.12 Shareholder’s equity An equity instrument is any contract that evidences a residual interest in the assets of an entity after deducting all of its liabilities. Equity instruments issued by the Company are recognized at the proceeds received, net of direct issue costs. Where the Company purchases treasury shares, the consideration paid, including any directly attributable incremental costs (net of income taxes), is deducted from equity attributable to the Company’s equity holders until the shares are cancelled, reissued or disposed of. Where such shares are subsequently sold or reissued, any consideration received, net of any directly attributable incremental transaction costs and the related income tax effects is included in equity attributable to the Company’s equity holders. The Company has never distributed any dividends to its shareholders. As of 31 December 2017, no profits were available for distribution.
Trade payables	2.13 Trade payables Payables after and within one year are measured at amortized cost, i.e., at the net present value of the payable amount. Unless the impact of discounting is material, the nominal value is recognized.
Financial liabilities	2.14 Financial liabilities Debt and equity instruments issued by the Company are classified as either financial liabilities or as equity in accordance with the substance of the contractual arrangements and the definitions of a financial liability and an equity instrument. Financial liabilities are classified as either “financial liabilities at fair value through profit or loss” or “other financial liabilities”.
Provisions	2.15 Provisions Provisions are recognized when the Company has a present obligation (legal or constructive) as a result of a past event, it is probable that the Company will be required to settle the obligation, and a reliable estimate can be made of the amount of the obligation. The amount recognized as a provision is the best estimate of the consideration required to settle the present obligation at the end of the reporting period, taking into account the risks and uncertainties surrounding the obligation. When a provision is measured using the cash flows estimated to settle the present obligation, its carrying amount is the present value of those cash flows (where the effect of the time value of money is material). When some or all of the economic benefits required to settle a provision are expected to be recovered from a third party, a receivable is recognized as an asset if it is reasonably certain that reimbursement will be received and the amount of the receivable can be measured reliably.
Retirement benefits	2.16 Retirement benefits The Company offers a post‑employment, death, disability and healthcare benefit scheme. All employees have access to these schemes. The death, disability and healthcare benefits granted to employees of the Company are covered by an external insurance company, where premiums are paid annually and charged to the income statement as they were incurred. The post‑employment pension plan granted to employees of the Company is a defined contribution plan under Belgian Law. Under defined contribution plans, the Company pays contributions based on salaries to organizations responsible for paying out pensions and social security benefits, in accordance with the laws and agreements applicable in each country. The Belgian defined contribution pension plans are by law subject to minimum guaranteed rates of return, historically 3.25% on employer contributions and 3.75% on employee contributions. These rates have been modified by the law of December 18, 2015 and effective for contribution paid as from 2016 to a new variable minimum return based on the OLO (‘Obligation Lineaire Obligaties’—Belgian Government Bond) rates, with a minimum of 1.75% and a maximum of 3.75%. Hence, those plans classify as defined benefit plans. Until year‑end 2015, the net liability recognized in the statement of financial position was based on the sum of the positive differences, determined by individual plan participant, between the minimum guaranteed reserves and the accumulated contributions based on the actual rates of return at the closing date. From 2016 onwards, these plans are accounted for as defined benefit plans (see note 4.13). The liability recognized in the balance sheet is the present value of the defined benefit obligation less the fair value of plan assets. An independent actuary calculates the defined benefit obligation based on factors such as age, years of service and compensation (projected unit credit method). The present value of the defined benefit obligation is determined by discounting the estimated future cash outflows using interest rates of high‑quality corporate bonds denominated in the currency in which the benefits will be paid and with terms to maturity that approximate the term when the related liability is due. Current service costs are recognized in personnel expenses and reflect the increase in the defined benefit obligation resulting from employee service in the current year. Past service costs are recognized immediately in personnel expenses. The net interest expense on the defined benefit liability is determined by applying the discount rate used to measure the defined benefit obligation at the beginning of the year to the then net defined benefit liability. Net interest expense is recognized in personnel expenses. Remeasurement gains and losses of the defined benefit obligation arising from experience adjustments and changes in actuarial assumptions are recognized immediately in other comprehensive income.
Short-term employee benefits	2.17 Short‑term employee benefits Short‑term employee benefits include salaries and social security taxes, paid vacation and bonuses. They are recognized as expenses for the period in which employees perform the corresponding services. Outstanding payments at the end of the period are shown as other current liabilities.
Share‑based payments	2.18 Share‑based payments Equity‑settled share‑based payments to employees and others providing similar services are measured at the fair value of the equity instruments at the grant date. Details regarding the determination of the fair value of equity‑settled share‑based transactions are set out in note 4.12. The fair value determined at the grant date of the equity‑settled share‑based payments is expensed on a straight‑line basis over the vesting period, based on the Group’s estimate of equity instruments that will eventually vest, with a corresponding increase in equity. At the end of each reporting period, the Group revises its estimate of the number of equity instruments expected to vest. The impact of the revision of the original estimates, if any, is recognized in profit or loss such that the cumulative expense reflects the revised estimate, with a corresponding adjustment to the equity‑settled share‑based payment reserve. Where the terms of equity‑settled share‑based payments are modified, the minimum expense recognized is the expense that would have been recognized if the terms had not been modified. An additional expense is recognized for any modification that increases the total fair value of the share‑based payments, or is otherwise beneficial to the employee as measured at the date of modification.
Deferred revenue	2.19 Deferred revenue Deferred revenue relates to cash received from commercial partnerships prior to completion of the earnings process. These payments are recognized as revenue over the estimated duration of the Company’s involvement in the research and development programs provided for under the terms of the agreements. Government grants whose primary condition is that the Company should purchase, construct or otherwise acquire non‑current assets are also recognized as deferred revenue in the statement of financial position.
Income taxes	2.20 Income taxes Income tax expense represents the sum of the tax currently payable and deferred tax. The tax currently payable is based on taxable profit for the year. Taxable profit differs from profit as reported in the statement of profit and loss and other comprehensive income because of items of income or expense that are taxable or deductible in other years and items that are never taxable or deductible. The Company’s liability for current tax is calculated using tax rates that have been enacted or substantively enacted by the end of the reporting period. Deferred tax is recognized on temporary differences between the carrying amounts of assets and liabilities in the financial statements and the corresponding tax basis used in the computation of taxable profit (e.g. differences between carrying amounts under IFRS and the statutory tax basis). Deferred tax liabilities are generally recognized for all taxable temporary differences. Deferred tax assets are generally recognized for all deductible temporary differences to the extent that it is probable that taxable profits will be available against which those deductible temporary differences can be utilized. Such deferred tax assets and liabilities are not recognized if the temporary difference arises from goodwill or from the initial recognition (other than in a business combination) of other assets and liabilities in a transaction that affects neither the taxable profit nor the accounting profit. The carrying amount of deferred tax assets is reviewed at the end of each reporting period and reduced to the extent that it is no longer probable that sufficient taxable profits will be available to allow all or part of the asset to be recovered. Deferred tax assets and liabilities are measured at the tax rates that are expected to apply in the period in which the liability is settled or the asset realized, based on tax rates (and tax laws) that have been enacted or substantially enacted by the end of the reporting period. The measurement of deferred tax liabilities and assets reflects the tax consequences that would follow from the manner in which the Company expects, at the end of the reporting period, to recover or settle the carrying amount of its assets and liabilities. Deferred tax assets and deferred tax liabilities are offset if there is a legally enforceable right to offset current tax assets and liabilities and if they relate to income taxes imposed by the same authority on the same taxable entity or in different tax entities that intend to settle current tax assets and liabilities on a net basis or their tax assets and liabilities will be realized simultaneously.
Revenue and other operating income recognition	2.21 Revenue and other operating income recognition The Group generates revenue from collaborations and strategic alliances. Revenue is recognized when it is probable that future economic benefits will flow to the group and these benefits can be measured reliably. Further, revenue recognition requires that all significant risks and rewards of ownership of the goods included in the transaction have been transferred to the buyer or when the related services are performed and specific criteria have been met for each of the Group’s activities as described below. Collaborations Collaborations typically include upfront payments, milestone payments, research and development service fees and may involve multiple elements. The Group evaluates whether the elements under these arrangements have value to its collaboration partner or client on a stand‑alone basis. If the Group determines that multiple deliverables exist, the consideration is allocated to one or more units of accounting based upon the best estimate of the selling price of each deliverable. Deliverables that do not meet these criteria are not evaluated separately for the purpose of revenue recognition. The Group receives upfront, milestone and other similar payments related to the sale of services or out‑licensing of products from these collaborations and strategic alliances. The revenue recognition policies can be summarized as follows: Upfront payments Upfront payments, for which there are subsequent deliverables, are initially reported as deferred revenue and are recognized as revenue when earned over the period of the development collaboration or the manufacturing obligation. Upfront payments also include license fees received upfront. Deferred revenue reflects the part of revenue that has not been recognized as income immediately upon receipt of payment and which relates to agreements with multiple components which cannot be separated. Deferred revenue is measured at nominal value. Milestone payments Revenue associated with performance milestones is recognized based upon the achievement of the milestone event if the event is substantive, objectively determinable and represents an important point in the development life cycle of the product. Research and development services fees Research and development service fees are recognized as revenue over the life of the research agreement as the required services are provided and costs are incurred. These services are usually in the form of a defined number of full‑time equivalents (FTE) at a specified rate per FTE. Commercial collaborations resulting in a reimbursement of research and development costs are recognized as revenue as the related costs are incurred. The corresponding research and development expenses are included in research and development expenses in the consolidated financial statements. Grants, research and development incentives and payroll tax rebates Because it carries out extensive research and development activities, the Group benefits from various grants, research and development incentives and payroll tax rebates from certain governmental agencies. These grants, research and development incentives and payroll tax rebates generally aim to partly reimburse approved expenditures incurred in research and development efforts of the Group and are credited to the statement of profit and loss and other comprehensive income, under other operating income, when the relevant expenditure has been incurred and there is reasonable assurance that the grants or research and development incentives are receivable.
Earnings per share	2.22 Earnings per share Basic net profit / (loss) per share is computed based on the weighted average number of ordinary shares outstanding during the period, excluding treasury shares. Diluted net profit / (loss) per share is computed based on the weighted‑average number of ordinary shares outstanding including the dilutive effect of options. Options should be treated as dilutive, when and only when their conversion to ordinary shares would decrease net profit per share from continuing operations.
Fair value measurements	2.23 Fair value measurements Historical cost is generally based on the fair value of the consideration given in exchange for assets. Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value measurement is based on the presumption that the transaction to sell the asset or transfer the liability takes place either in the principal market for the asset or liability or in the absence of a principal market, in the most advantageous market for the asset or liability. The principal or the most advantageous market must be accessible by the Company. The fair value of an asset or a liability is measured using the assumptions that market participants would use when pricing the asset or liability, assuming that market participants act in their economic best interest. All assets and liabilities for which fair value is measured or disclosed in the financial statements are categorized within the fair value hierarchy, described as follows, based on the lowest level input that is significant to the fair value measurement as a whole: Level 1— Quoted (unadjusted) market prices in active markets for identical assets or liabilities Level 2— Valuation techniques for which the lowest level input that is significant to the fair value measurement is directly or indirectly observable Level 3— Valuation techniques for which the lowest level input that is significant to the fair value measurement is unobservable
Adoption of new and revised standards	2.24 Adoption of new and revised standards New ac The following new standards and amendments to standards are mandatory for the first time for the financial year beginning January 1, 2017: ■ Amendments to IAS 12,'Income taxes' on Recognition of deferred tax assets for unrealized losses. These amendments on the recognition of deferred tax assets for unrealized losses clarify how to account for deferred tax assets related to debt instruments measured at fair value. ■ Annual improvements 2014-2016 applicable to three standards of which changes on IFRS 1 and IAS 28 are applicable as of 1 January 2018 and changes on IFRS 12 are applicable as of 1 January 2017. These set of amendments impacts 3 standards: IFRS 1,’ First-time adoption of IFRS’, regarding the deletion of short-term exemptions for first-time adopters regarding IFRS 7, IAS 19, and IFRS 10; IFRS 12,’Disclosure of interests in other entities’ regarding clarification of the scope of the standard (these amendments should be applied retrospectively for annual periods beginning on or after 1 January 2017) and IAS 28, ‘Investments in associates and joint ventures’ regarding measuring an associate or joint venture at fair value. New accounting policies and disclosures effective in 2018 or later The following new standards and amendments to standards have been issued, but are not mandatory for the first time for the financial year beginning 1 January 2017 and have been endorsed by the European Union. ■ IFRS 9 ‘Financial instruments’ and subsequent amendments, effective for annual periods beginning on or after 1 January 2018. The standard addresses the classification, measurement, derecognition of financial assets and financial liabilities and general hedge accounting. We performed a preliminary assessment evaluating the guidance to determine the potential impact on the consolidated financial statements. Financial assets and liabilities are recognized on our statement of financial position when we become a party to the contractual provisions of the instrument. Hedging and derivatives have never been used: we do not use currency derivatives to hedge planned future cash flows, nor do we make use of forward foreign exchange contracts. Our assessment is that the coming new standards on IFRS 9 “Financial instruments” and subsequent amendments (applicable for annual periods beginning on or after January 1, 2018) should not have a material impact on our consolidated financial statements. We plan to adopt IFRS 9 on the effective date. ■ IFRS 15 ‘Revenue from contracts with customers’ and subsequent amendments. The standard will improve comparability of the top line in financial statements globally. Companies using IFRS will be required to apply the revenue standard for annual periods beginning on or after 1 January 2018. In 2017, the Company made an impact analysis in view of the application of IFRS 15 Revenue from Contracts with Customers, applicable for annual periods beginning on or after 1 January 2018. In accordance with IFRS 15 companies need to apply a five-step model to determine when, how and at what amount revenue is to be recognized depending on whether certain criteria are met. 1. An inventory of the contracts with customers was completed. The substance of our current arrangements is that the Group is licensing its Intellectual Property, providing research and development services and in the future, selling its products to collaborative partner entities. Revenue is generated through these arrangements via upfront payments, milestone payments based on development criteria, research and development service fees on an agreed full-time equivalent (FTE) basis and future sales based milestones and sales based royalties. 2. Identify performance obligations We have assessed that there is one single combined performance obligation for certain arrangements in our material ongoing license and collaboration arrangements under the new standards of IFRS 15, being the transfer of a license combined with performance of research and development services. This is because we consider that the license has no stand-alone value without the Group being further involved in the research and development collaboration and that there is interdependence between the license and the research and development services to be provided. We estimate that the Group’s activities during the collaboration are going to significantly add to Intellectual Property and thereby the value of the programs. 3. Determine the transaction price We have analyzed the transaction prices of our material ongoing license and collaboration arrangements currently composed of upfront payments, milestone payments and research and development service fees being delivered. Sales based milestones and sales based royalties are part of certain of our arrangements but are not yet included in our revenues as our most advanced license and collaboration arrangement is still in the development phase. As prescribed under IFRS 15 transaction price needs to be re-assessed at each reporting period. 4. Allocate the transaction price In principle, an entity shall allocate the transaction price to each performance obligation identified in the contract on a relative stand-alone selling price. However, the transaction price of certain of our arrangements is allocated to a single combined performance obligation since the transfer of a license is considered to be combined with performance of research and development services. Therefore, research and development milestone payments are variable considerations that are entirely allocated to the single combined performance obligation. 5. Recognize revenue Revenue from certain arrangements is recognized as the Group satisfies a combined performance obligation. The Company recognizes upfront payments and milestone payments, allocated to a combined performance obligation over the estimated service period based on a pattern that reflects the transfer of the services. The revenues recognized would reflect the level of service each period. In this case, the Group would use an output model that considers estimates of the percentage of total research and development service costs that are completed each period compared to the total estimated services costs (% of completion method). Research and development service fees are recognized as revenues when costs are incurred and agreed by the parties as the Group is acting as a principal in the scope of its stake of the research and development activities of its ongoing license and collaboration agreements. Assessment of the impact of IFRS 15 The Company plans to adopt IFRS 15 on January 1, 2018 using a modified retrospective approach. Based on the company’s assessment of all contracts, potential performance obligations, and potential allocation of the revenue, the Group estimates the impact of IFRS 15 on its consolidated financial statements as follows: - there is no impact on the pattern and timing of revenue recognition for upfront payments and research and development service fees, - the pattern and timing of revenue recognition of milestone payments is different: milestone payments were previously recognized based on upon the achievement of the milestone event, whereas under IFRS 15, the milestone payment is linked to a combined performance obligation over the estimated service period, - as a result, the accumulated losses and deferred revenue will increase by €2.7 million at the opening balance sheet date of January 1, 2018. ■ IFRS 16 ’Leases’ (effective 1 January 2019). This standard replaces the current guidance in IAS 17 and is a far-reaching change in accounting by lessees in particular. Under IAS 17, lessees were required to make a distinction between a finance lease (on balance sheet) and an operating lease (off balance sheet). IFRS 16 requires lessees to recognize a lease liability reflecting future lease payments and a ‘right-of-use asset’ for virtually all lease contracts. For lessors, the accounting stays almost the same. However, as the IASB has updated the guidance on the definition of a lease (as well as the guidance on the combination and separation of contracts), lessors will also be affected by the new standard. Under IFRS 16, a contract is, or contains, a lease if the contract conveys the right to control the use of an identified asset for a period of time in exchange for consideration. We know that this new coming standard will have an impact on our consolidated financial statements in 2019 and we are currently evaluating the guidance to determine this impact. We plan to adopt IFRS 16 on the effective date. ■ Amendments to IFRS 2: Share-based payments (effective 1 January 2018): The amendment clarifies the measurement basis for cash-settled payments and the accounting for modifications that change an award from cash settled to equity settled. It also introduces an exception to the principles in IFRS 2 that will require an award to be treated as if it was wholly equity-settled, where an employer is obliged to withhold an amount for the employee’s tax obligation associated with a share-based payment and pay the amount to the tax authorities. These amendments will not have any material impact on our consolidated financial statements. ■ IFRIC 22,’ Foreign currency transactions and advance consideration (effective 1 January 2018): ’This IFRIC addresses foreign currency transactions or parts of transactions where there is consideration that is denominated or priced in a foreign currency. The interpretation provides guidance for when a single payment/receipt is made as well as for situations where multiple payments/receipts are made. The guidance aims to reduce diversity in practice. This standard will not have any material impact on our consolidated financial statements. ■ IFRIC 23, ‘Uncertainty over income tax treatments’ (effective 1 January 2019). This interpretation clarifies the accounting for uncertainties in income taxes. The interpretation is to be applied to the determination of taxable profit (tax loss), tax bases, unused tax losses, unused tax credits and tax rates, when there is uncertainty over income tax treatments under IAS 12. We are currently evaluating the guidance to determine the impact on our consolidated financial statements in 2019. We plan to adopt IFRIC 23 on the effective date.
Segment reporting	2.25 Segment reporting Segment results include revenue and expenses directly attributable to a segment and the relevant portion of revenue and expenses that can be allocated on a reasonable basis to a segment. Segment assets and liabilities comprise those operating assets and liabilities that are directly attributable to the segment or can be allocated to the segment on a reasonable basis. Segment assets and liabilities do not include income tax items. The Group manages its activities and operates as one business unit which is reflected in its organizational structure and internal reporting. The Group does not distinguish in its internal reporting different segments, neither business nor geographical segments. The chief operating decision‑maker is the Board of Directors.

Notes_relating to the consoli15

Notes relating to the consolidated statement of financial position (Tables)	12 Months Ended
	Dec. 31, 2017
Notes relating to the consolidated statement of financial position
Schedule of Intangible assets	(in thousands of €) Opening balance as on January 1, 2015 Cost € 67 Accumulated amortization (60) Book value at the beginning of the year 7 Movements Additions 5 Amortization (5) Balance as on December 31, 2015 Cost 72 Accumulated amortization (65) Book value at year end 7 Movements Additions 21 Amortization (11) Balance as on December 31, 2016 Cost 93 Accumulated amortization (76) Book value at year end 17 Movements Additions 6 Amortization (10) Balance as on December 31, 2017 Cost 99 Accumulated amortization (86) Book value at year end € 13
Schedule of Property, plant and equipment	Office and lab (in thousands of €) IT equipment equipment Total Opening balance as on January 1, 2015 Cost € 63 € 935 € 998 Accumulated depreciation (48) (784) (832) Book value at the beginning of the year 15 151 166 Movements Additions 30 244 274 Depreciation (18) (173) (191) Closing balance as on December 31, 2015 Cost 93 1,179 1,272 Accumulated depreciation (66) (957) (1,023) Book value at year end 27 222 249 Movements Additions 115 725 840 Depreciation (38) (285) (323) Closing balance as on December 31, 2016 Cost 208 1,904 2,112 Accumulated depreciation (104) (1,242) (1,346) Book value at year end 104 662 766 Movements Additions 25 321 346 Cost of disposals — (69) (69) Depreciation (53) (372) (425) Accumulated depreciation on disposals — 58 58 Closing balance as on December 31, 2017 Cost 233 2,156 2,389 Accumulated depreciation (157) (1,556) (1,713) Book value at year end € 76 € 600 € 676
Schedule of Research and development incentive receivables	Year Ended December 31, (in thousands of €) 2017 2016 2015 Research and development incentive receivables—current € 158 € 163 € — Research and development incentive receivables—non-current 3,033 2,046 1,568 € 3,191 € 2,209 € 1,568
Schedule of Restricted cash	Year Ended December 31, (in thousands of €) 2017 2016 2015 Non ‑ current restricted cash Rental guarantees € 256 € 244 € — Escrow account > 1 year — 905 — Total non ‑ current € 256 € 1,149 € — Current restricted cash Escrow account < 1 year 1,692 786 — Total restricted cash € 1,948 € 1,935 € —
Schedule of Trade and other receivables	Year Ended December 31, (in thousands of €) 2017 2016 2015 VAT receivable € 317 € 278 € 175 Trade receivables 845 1,118 719 Other receivables 750 — — Interest receivable — 6 17 VLAIO grant receivable 930 568 445 € 2,842 € 1,970 € 1,356
Schedule of Cash and cash equivalents	Year Ended December 31, (in thousands of €) 2017 2016 2015 Cash equivalents € 25,000 € 54,500 € 11,006 Cash and bank balances 165,867 35,397 24,508 € 190,867 € 89,897 € 35,514
Schedule of Shareholders’ capital	Number of shares outstanding on January 1,2015 15,705,112 Exercise of Options on September 1,2015 97,655 Number of shares outstanding on December 31,2015 15,802,767 Private placement (Federated Investment) on January 20, 2016 1,480,420 Exercise of Options on February 15, 2016 2,200 Exercise of Options on March 16, 2016 10,000 Exercise of Options on April 21, 2016 10,000 Exercise of Options on May 27 , 2016 33,092 Private placement (Sunflower) on June 1, 2016 2,703,000 Exercise of Options on September 26, 2016 70,000 Exercise of Options on October 17, 2016 15,000 Number of shares outstanding on December 31, 2016 20,126,479 U.S. initial public offering on Nasdaq on May 17, 2017 5,865,000 Over-allotment option exercised by underwriters on May 19, 2017 879,750 Exercise of Options on August 24, 2017 5,000 Exercise of Options on September 1, 2017 15,000 Exercise of Options on October 2, 2017 1,400 Exercise of Options on November 7, 2017 950 Exercise of Options on November 14, 2017 4,260 Exercise of Options on November 15, 2017 40,750 Exercise of Options on November 21, 2017 53,092 Exercise of Options on November 22, 2017 7,730 Exercise of Options on December 4, 2017 65,380 U.S. second public offering on Nasdaq on December 13, 2017 4,440,000 Over-allotment option exercised by underwriters on December 14, 2017 666,000 Exercise of Options on December 18, 2017 9,850 Number of shares outstanding on December 31,2017 32,180,641
Schedule of Share‑based payment arrangements	Exercise price Outstanding per stock stock options on options December 31, Expiry date (in €) 2017 2016 2015 2019 € 3.95 — — 103,370 2020 3.95 36,960 112,738 62,460 2021 3.95 2,850 3,800 3,800 2022 2.44 — — 686,732 2023 3.95 — — 55,747 2024 2.44 314,593 360,787 — 2024 2.44 135,890 169,926 — 2024 3.95 15,692 55,746 — 2024 7.17 516,100 522,500 537,917 2024 2.44 83,820 83,820 — 2025 11.44 39,000 39,000 56,500 2025 10.34 3,000 3,000 3,000 2025 9.47 235,514 235,733 243,400 2026 11.38 60,000 60,000 — 2026 11.47 282,310 283,360 — 2026 14.13 362,126 363,226 — 2027 18.41 120,536 — — 2027 € 21.17 653,825 — — 2,862,216 2,293,636 1,752,926
Schedule of number and weighted average exercise prices of share options roll forward	2017 2016 2015 Number of Weighted average Number of Weighted average Number of Weighted average stock options exercise price stock options exercise price stock options exercise price Outstanding at January 1 2,293,636 € 7.72 1,752,926 € 5.37 1,595,015 € 4.39 Granted 774,361 20.74 712,176 12.82 302,900 9.84 Exercised (203,412) 3.46 (140,292) 3.52 (97,656) 2.44 Forfeited (2,369) 12.52 (31,174) 10.90 (47,333) 7.17 Outstanding at December 31, 2,862,216 11.54 2,293,636 7.72 1,752,926 5.37 Exercisable at December 31, 1,598,829 € 6.80 1,257,091 € 4.68 1,366,703 € 4.41
Schedule of weighted average remaining contractual life for each range of exercise price:	Weighted average remaining Outstanding on contractual life Exercise price (in €) December 31,2017 (in years) 2.44–3.95 589,805 5.81 7.17–9.47 751,614 7.28 10.33–14.13 746,436 8.62 18.41–21.17 774,361 9.88
Schedule of parameters used in relation to the new grants	Below is an overview of the parameters used in relation to the grants during 2017: Stock options granted in June 2017 Dec 2017 Number of options granted 120,536 653,825 Average fair value of options (in EUR) € 7.90 € 37.10 Share price (in EUR) € 17.76 € 53.50 Exercise price (in EUR) € 18.41 € 21.17 Expected volatility 36.6 % 36.1 % Average expected option life (in years) 10 10 Risk ‑ free interest rate 0.61 % 0.53 % Expected dividends — % — % Below is an overview of the parameters used in relation to the grants during 2016: Stock options granted in May 2016 June 2016 Dec 2016 Number of options granted 288,950 60,000 363,226 Average fair value of options (in EUR) € 5.32 € 5.46 € 7.25 Share price (in EUR) € 11.10 € 11.36 € 14.96 Exercise price (in EUR) € 11.47 € 11.38 € 14.13 Expected volatility 40.2 % 39.6 % 38.0 % Average expected option life (in years) 10 10 10 Risk ‑ free interest rate 0.52 % 0.46 % 0.67 % Expected dividends — % — % — % Below in an overview of the parameter used in relation to the grants during 2015: Stock options granted in June 2015 Sept 2015 Dec 2015 Number of options granted 56,500 3,000 243,400 Average fair value of options (in EUR) € 7.79 € 6.79 € 6.25 Share price (in EUR) € 11.58 € 10.24 € 9.85 Exercise price (in EUR) € 11.44 € 10.34 € 9.47 Expected volatility 59 % 59 % 58 % Average expected option life (in years) 10 10 10 Risk‑free interest rate 1.21 % 1.08 % 0.98 % Expected dividends — % — % — %
Schedule of Defined benefit plans	(in thousands of €) 2017 2016 2015 Defined benefit obligation € 1,007 € 670 € 486 Fair value of plan assets 982 669 486 Deficit / surplus (−) of funded obligations 25 1 — Net liability (asset) € 25 € 1 € —
Schedule of movement in the defined benefit obligation, plan assets, net liability and asset	(in thousands of €) 2017 2016 Defined benefit obligation at 1 January € 670 € 486 Service cost 352 113 Interest expense / income (−) 11 6 Contributions by plan participants (148) (64) Actuarial gains (-) / losses (+) 124 131 Benefits paid / transfers out (2) (2) Defined benefit obligation at 31 December € 1,007 € 670 (in thousands of €) 2017 2016 Fair value of plan assets at 1 January € 669 € 486 Interest expense / income (−) 10 7 Administrative costs & taxes (46) (19) Contributions by company & participants 423 176 Contributions by plan participants (148) (64) Actuarial gains (+) / losses (-) 76 85 Benefits paid / transfers out (2) (2) Fair value of plan assets at 31 December € 982 € 669
Schedule of Actuarial assumption	Actuarial assumption 2017 2016 Discount rate 1.3 % 1.3 %
Schedule of Sensitivity analyses	Sensitivity analysis Change in Impact on defined ‑ (in thousands of €) assumption benefit obligation % Discount rate −0.25 % Increase by 35.9 3.56 % Discount rate 0.25 % Decrease by 31.0 (3.08) %
Schedule of Trade and other payables	Year Ended December 31, (in thousands of €) 2017 2016 2015 Trade payables € 4,395 € 4,385 € 1,886 Accruals for invoices to be received 4,046 5,444 1,239 Short-term employee benefits 6,844 2,362 1,418 € 15,285 € 12,191 € 4,543

Notes to consolidated stateme16

Notes to consolidated statement of profit and loss and other comprehensive income (Tables)	12 Months Ended
	Dec. 31, 2017
Notes to consolidated statement of profit and loss and other comprehensive income
Schedule of revenue	Year Ended December 31, (in thousands of €) 2017 2016 2015 Upfront payments € 20,137 € 9,103 € 2,194 Milestone payments 9,677 500 343 Research and development service fees (FTE) 6,601 5,110 4,317 € 36,415 € 14,713 € 6,854
Schedule of other operating income	Year Ended December 31, (in thousands of €) 2017 2016 2015 Grants € 422 € 779 € 1,598 Research and development incentives 983 641 608 Payroll tax rebates 3,436 1,019 895 € 4,841 € 2,439 € 3,101
Schedule of grants	(Amounts presented in thousands of €) Flanders Innovation & Entrepreneurship—TGO Grantor: Flanders Innovation & Entrepreneurship Agency Start date: 01/01/2013 End date: 06/30/2017 Amount granted and approved: € 2,697 Amount recognized: 2,697 Flanders Innovation & Entrepreneurship—Baekelandt Grantor: Flanders Innovation & Entrepreneurship Agency Start date: 01/01/2014 End date: 12/31/2017 Amount granted and approved: € 277 Amount recognized: 270 Flanders Innovation & Entrepreneurship 4 Grantor: Flanders Innovation & Entrepreneurship Agency Start date: 01/01/2015 End date: 12/31/2017 Amount granted and approved: € 1,568 Amount recognized: 1,568
Schedule of revenue and non-current assets generated geographically	Revenue from external customers Year ended December 31, (in thousands of €) 2017 2016 2015 Netherlands € 628 € 548 € 275 Belgium — — — Germany — 311 2,190 Denmark 6,240 3,066 827 Switzerland 2,486 3,315 3,127 United States 1 47 435 Luxembourg 27,060 7,426 — Total € 36,415 € 14,713 € 6,854
Schedule of research and development expenses	Year Ended December 31, (in thousands of €) 2017 2016 2015 Personnel expense € 16,473 € 9,844 € 6,665 External research and development expenses 27,893 17,562 11,653 Materials and consumables 1,562 1,180 1,050 Depreciation and amortization 446 335 196 Other expenses 5,366 2,636 1,071 € 51,740 € 31,557 € 20,635
Schedule of general and administrative expenses	Year Ended December 31, (in thousands of €) 2017 2016 2015 Personnel expense € 6,745 € 3,256 € 1,607 Consulting fees 3,289 2,563 2,395 Supervisory board 621 446 165 Office costs 1,793 746 758 € 12,448 € 7,011 € 4,925
Schedule of personnel expenses	Year Ended December 31, (in thousands of €) 2017 2016 2015 Short ‑ term employee benefits—Salaries € 12,149 € 8,527 € 5,192 Short ‑ term employee benefits—Social Security 1,504 1,027 802 Post ‑ employment benefits 291 175 207 Termination benefits 8 86 124 Share ‑ based payment 3,985 2,849 1,945 Employer social security contributions stock options 5,281 436 — € 23,218 € 13,100 € 8,270
Schedule of full-time equivalents employees	Year Ended December 31, Number of FTE 2017 2016 2015 Research and development 56.8 46.9 31.4 General and administrative 14.7 9.9 5.8 71.5 56.8 37.2
Schedule of operating lease commitments	Year Ended December 31, Operating lease commitments (in thousands of €) 2017 2016 2015 Less than 1 year € 1,028 € 915 € 630 1–3 years 465 1,159 1,130 3–5 years 33 24 142 More than 5 years — — — € 1,526 € 2,098 € 1,902
Schedule of financial result and exchange gains/(losses)	Year Ended December 31, (in thousands of €) 2017 2016 2015 Interest income on bank deposits € 165 € 61 € 76 Net gains on investments at FVTPL 210 12 36 Realized gain on non-current financial assets 875 — — Financial income 1 250 73 112 Exchange gains/(losses) (5 797) (31) 181
Schedule of income tax expenses	Year Ended December 31, (in thousands of €) 2017 2016 2015 Loss before taxes (27,479) (21,374) (15,312) Income tax calculated at 25% 6,870 5,344 3,828 Effect of expenses that are not deductible in determining taxable results (1,141) (755) (568) Effect of stock issue expenses that are not deductible in determining taxable results 5,754 462 — Effect of concessions (R&D incentives and grants) 453 463 759 Effect of tax losses carried forward not recognized (Netherlands) — (5,551) (3,601) Effect of usage of tax losses carried forward not previously recognized (Netherlands) 19,378 — — Effect of tax losses carried forward not recognized (Belgium) (27,413) — (301) Effect of usage of tax losses carried forward not previously recognized (Belgium) — 195 — Effect of change in corporate tax rate on deferred tax asset not previously recognized (Belgium) 373 — — Effect of different tax rates in jurisdictions in which the company operates (517) (180) (122) Deferred tax asset other than loss carryforwards not recognized (4,363) — — Other 9 22 5 Income tax expense recognized in the consolidated statement of profit and loss € (597) € — € —
Schedule of loss per share	Year Ended December 31, (in thousands of €) 2017 2016 2015 Loss of the year € (28,076) € (21,374) € (15,312) Weighted average number of shares outstanding 24,609,536 18,820,612 15,734,007 Basic and diluted loss per share (in €) € (1.14) € (1.14) € (0.97)

Financial instruments and fin17

Financial instruments and financial risk management (Tables)	12 Months Ended
	Dec. 31, 2017
Financial instruments and financial risk management
Schedule of overview of financial instruments	At December 31,2017 At December 31,2016 At December 31,2015 Carrying Carrying Carrying (in thousands of €) amount Fair value amount Fair value amount Fair value Non ‑ current financial assets € 1 € 1 € 1 € 1 € 1 € 1 Current financial assets 168,907 168,907 6,831 6,831 6,813 6,813 Financial assets 168,908 168,908 6,832 6,832 6,814 6,814 Other non-current assets 125 125 — — — — Trade and other receivables 2,842 2,842 1,970 1,970 1,356 1,356 Cash and cash equivalents 190,867 190,867 89,897 89,897 35,514 35,514 Non ‑ current restricted cash 256 256 1,149 1,149 — — Current restricted cash 1,692 1,692 787 787 — — Loans and receivables 195,782 195,782 93,803 93,803 36,870 36,870 Total financial assets 364,690 364,690 100,635 100,635 43,684 43,684 Provision for employee benefits 25 25 1 1 — — Trade and other payables 15,285 15,285 12,191 12,191 4,543 4,543 Financial liabilities at amortized cost 15,310 15,310 12,192 12,192 4,543 4,543 Total financial liabilities € 15,310 € 15,310 € 12,192 € 12,192 € 4,543 € 4,543
Schedule of assets at fair value	At December 31,2017 (in thousands of €) Level 1 Level 2 Level 3 Non-current financial assets € € € 1 Current financial assets 168,907 Assets carried at fair value € 168,907 € — € 1 At December 31,2016 (in thousands of €) Level 1 Level 2 Level 3 Non-current financial assets € € € 1 Current financial assets 6,831 Assets carried at fair value € 6,831 € — € 1 At December 31,2015 (in thousands of €) Level 1 Level 2 Level 3 Non-current financial assets € € € 1 Current financial assets 6,813 Assets carried at fair value € 6,813 € — € 1
Schedule of net exposure exchange differences of the monetary assets	At December 31, (in thousands of €) 2017 2016 2015 USD 147,169 624 345 GBP 406 — —

Other disclosures (Tables)

Other disclosures (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of transactions between related parties [line items]
Schedule of key management personnel	Year Ended December 31, (in thousands of €) 2017 2016 2015 Short term employee benefits € 3,126 € 1,832 € 1,482 Post employment benefits 115 125 59 Termination benefits — — 124 Share‑based payment(1) 12,041 2,261 1,761 Employer social security contributions stock options(2) 3,073 436 — € 18,355 € 4,654 € 3,426 (1) Amount shown represents the expenses, recorded with respect to the option awards granted in the year, measured using the Black Scholes formula. (2) The Group incurs employer social security costs with respect to the option awards granted to certain members of the executive management. The amount of employer social security costs depends on the actual economic value realized and therefore varies based on our stock price. At each reporting date, the Group makes a calculation of the exposure.
Schedule of number and weighted average exercise prices of share options roll forward	2017 2016 2015 Number of Weighted average Number of Weighted average Number of Weighted average stock options exercise price stock options exercise price stock options exercise price Outstanding at January 1 2,293,636 € 7.72 1,752,926 € 5.37 1,595,015 € 4.39 Granted 774,361 20.74 712,176 12.82 302,900 9.84 Exercised (203,412) 3.46 (140,292) 3.52 (97,656) 2.44 Forfeited (2,369) 12.52 (31,174) 10.90 (47,333) 7.17 Outstanding at December 31, 2,862,216 11.54 2,293,636 7.72 1,752,926 5.37 Exercisable at December 31, 1,598,829 € 6.80 1,257,091 € 4.68 1,366,703 € 4.41
Schedule of auditors’ fees expensed in the income statement	Year Ended December 31, Fees 2017 2016 2015 in thousands of € Audit fees(1) € 205 € 85 € 70 Audit-related fees 698 65 35 Tax and other services(2) — 2 3 Total € 903 € 152 € 108 (1) Audit services performed by Deloitte Accountants B.V. as the external auditor referred to in Section 1 of the Dutch Accounting Firms Oversight Act (Wta) as well as by the Deloitte network. (2) Tax and other services performed conducted by the Deloitte network.
Schedule of overview of Subsidiaries	Name Registration number Country Participation Main activity argenx SE COC 24435214 The Netherlands 100.00 % Holding company argenx BVBA Belgium 100.00 % Biotechnical research on drugs and pharma processes argenx US, Inc. 36-4880497 USA 100.00 % Pharmaceuticals and pharmacy supplies merchant wholesalers
Executive Directors
Disclosure of transactions between related parties [line items]
Schedule of key management personnel	Pension 2015 Base salary Bonus contributions Social security costs ESOP (1) Other (2) Total Tim Van Hauwermeiren 217,260 103,298 8,690 8,760 201,248 9,210 548,466 Eric Castaldi 222,159 75,075 62,097 133,621 185,464 — 678,416 Total 439,419 178,373 70,787 142,381 386,712 9,210 1,226,882 Pension 2016 Base salary Bonus contributions Social security costs ESOP (1) Other (2) Total Tim Van Hauwermeiren 253,284 101,314 11,929 10,284 488,020 9,184 874,015 Eric Castaldi 235,952 82,583 84,972 136,124 786,035 — 1,325,666 Total 489,236 183,897 96,901 146,408 842,597 9,184 1,768,223 Pension 2017 Base salary Bonus contributions Social security costs ESOP (1) Other (2) Total Tim Van Hauwermeiren 303,941 301,635 14,315 9,459 2,968,195 9,601 3,607,146 Eric Castaldi 271,344 173,284 62,335 254,732 4,089,209 14,979 4,865,883 Total 575,285 474,919 76,650 264,191 7,057,404 24,580 8,473,029 (1) Amount shown represents the expenses, recorded with respect to the option awards granted in the year, measured using the Black Scholes formula, and the employer social security costs with respect to the option awards granted to certain members of the executive management. The amount of employer social security costs depends on the actual economic value realized and therefore varies based on our stock price. At each reporting date, the Group makes a calculation of the exposure. (2) Consists of costs attributable to the lease of a company car and employer-paid medical insurance premiums.
Schedule of number and weighted average exercise prices of share options roll forward	The table below shows the number of stock options granted to the executive directors during the years ended December 31, 2017, 2016 and 2015 and their exercise price equal to the fair market value upon date of grant, and the stock options exercised during 2017, 2016 and 2015. 2015 ESOPs Term Exercise price Exercised Tim Van Hauwermeiren 30,600 10 years 9.47 — Eric Castaldi 28,200 10 years 9.47 — Total 58,800 — 2016 ESOPs Term Exercise price Exercised Tim Van Hauwermeiren 50,000 10 years 11.47 30,600 10 years 14.13 3.95 53,092 2.44 72,200 Eric Castaldi 28,200 10 years 11.47 28,200 10 years 14.13 Total 137,000 125,292 2017 ESOPs Term Exercise price Exercised Tim Van Hauwermeiren 80,000 10 years 21.17 2.44 65,380 Eric Castaldi 43,200 10 years 21.17 Total 123,200 65,380 The table below shows the stock options held at the start of the year ended December 31, 2017, the stock options granted to executive directors which have vested during the year ended December 31, 2017 and the stock options to vest in the years until 2020. Total Total options options held on options options held on Options Options Options Options Options January 1, granted in exercised in December 31, vested Exercise vested in Exercise to vest Exercise to vest Exercise to vest Exercise Name 2017 2017 2017 2017 until 2016 price 2017 price 2018 price 2019 price 2020 price Tim Van Hauwermeiren 281,580 80,000 (65,380) 296,200 70,000 7.17 35,000 10,200 9.47 10,200 10,200 26,389 16,667 6,944 10,200 10,200 10,200 26,667 21.17 26,666 21.17 26,667 21.17 Eric Castaldi 230,607 43,200 — 273,807 72,007 2.44 9,000 2.44 43,333 7.17 21,667 7.17 9,400 9.47 9,400 9.47 9,400 9.47 14,883 9,400 11.47 3,917 11.47 9,400 9,400 14.13 9,400 14.13 14,400 21.17 14,400 21.17 14,400 21.17
Schedule of weighted average contractual term	Name Number of options Remaining term at December 31, 2017 (rounded up) Tim Van Hauwermeiren 105,000 7.0 years 30,600 8.0 years 50,000 8.5 years 30,600 9.0 years 80,000 10.0 years Eric Castaldi 60,970 6.5 years 85,037 7.0 years 28,200 8.0 years 28,200 8.5 years 28,200 9.0 years 43,200 10.0 years
Non-executive Directors
Disclosure of transactions between related parties [line items]
Schedule of key management personnel	2017 2016 2015 Peter Verhaeghe € 77,500 € 55,000 € 35,000 John Paul de Koning — — — Christina Takke NA NA — David L Lacey 50,000 45,930 45,651 Werner Lanthaler 55,000 45,000 35,000 Pamela Klein 42,500 35,000 NA Don Debethizy 52,500 43,000 27,617 A.A. Rosenberg 42,500 — — Total € 320,000 € 223,930 € 143,268
Schedule of number and weighted average exercise prices of share options roll forward	The table below shows the number of stock options granted to the non-executive directors during the years ended December 31, 2017, 2016 and 2015 and their exercise price, based on the 30 day average stock price prior to their date of grant, and the stock options exercised during the years ended December 31, 2015 and 2016. 2015 ESOPs Term Exercise price Exercised Don Debethizy 15,000 10 years 11.44 Total 15,000 — 2016 ESOPs Term Exercise price Exercised Peter Verhaeghe 10,000 10 years 11.38 David L Lacey 10,000 10 years 11.38 Werner Lanthaler 10,000 10 years 11.38 Don Debethizy 10,000 10 years 11.38 Pamela Klein 10,000 10 years 11.38 A.A. Rosenberg (1) 15,000 10 years 14.13 Total 50,000 — (1) 15,000 stock options were granted to Msc. A.A. Rosenberg in December 2016 in his capacity of consultant to the company. Msc. A.A. Rosenberg was appointed as a member of our board of directors at our Annual General Meeting in April 2017. 2017 ESOPs Term Exercise price Exercised David L Lacey 15,000 10 years 21.17 Total 15,000 — The table below shows the stock options held at the start of the year ended December 31, 2017 and the stock options granted to the non‑executive directors which have vested during the year ended December 31, 2017, as well as the stock options to vest in the years ending December 31, 2018, December 31, 2019 and December 31, 2020 (in number of stock options), and the respective exercise price of such stock options: Total Total Options Options Options options Options options Options Options to to to held on granted held on vested vested vest vest vest January 1, in December 31, until Exercise in Exercise in Exercise in Exercise in Exercise Name 2017 2017 2017 2016 price 2017 price 2018 price 2019 price 2020 price Peter Verhaeghe 34,585 — 34,585 11,626 € 2.44 7,959 € 3.95 3,333 € 7.17 1,667 € 7.17 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 David L. Lacey 29,443 15,000 44,443 6,643 € 2.44 8,533 € 7.17 4,267 € 7.17 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 5,000 € 21.17 5,000 € 21.17 5,000 € 21.17 Werner Lanthaler 29,416 — 29,416 12,814 € 2.44 1,602 € 2.44 3,333 € 7.17 1,667 € 7.17 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 J. Donald deBethizy 25,000 — 25,000 7,500 € 11.44 5,000 € 11.44 2,500 € 11.44 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 Pamela Klein 25,000 — 25,000 7,500 € 11.44 5,000 € 11.44 2,500 € 11.44 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 A.A. Rosenberg 15,000 — 15,000 — € 14.13 5,000 € 14.13 5,000 € 14.13 5,000 € 14.13
Schedule of weighted average contractual term	Remaining term on Number of December 31, 2017 Name stock options (rounded up) Peter K.M. Verhaeghe 3,650 2.5 years 2,340 3.0 years 5,560 5.5 years 3,181 6.0 years 9,854 7.0 years 10,000 8.5 years David L. Lacey 3,180 5.5 years 1,818 6.0 years 14,445 7.0 years 10,000 8.5 years 15,000 10.0 years Werner Lanthaler 10,850 6.0 years 8,566 7.0 years 10,000 8.5 years J. Donald deBethizy 15,000 7.5 years 10,000 8.5 years Pamela Klein 15,000 7.5 years 10,000 8.5 years A.A. Rosenberg 15,000 9.0 years

Significant accounting polici19

Significant accounting policies (Details)	12 Months Ended
	Dec. 31, 2017
Software
Intangible assets
Amortization period	3 years

Significant accounting polici20

Significant accounting policies - Property Plant and Equipment and Others (Details) € in Thousands	12 Months Ended
	Dec. 31, 2017EUR (€)item	Jan. 01, 2018EUR (€)	Dec. 31, 2016EUR (€)	Dec. 31, 2015EUR (€)
Property, plant and equipment
Impairment of assets	€ 0
Profit available for distribution	0
Accumulated losses	100,568		€ 72,492	€ 51,118
Deferred revenue	€ 10,070		€ 30,206	€ 4,141
Number of operating segments | item	1
Assessment of the impact of IFRS 15
Property, plant and equipment
Accumulated losses		€ 2,700
Deferred revenue		€ 2,700
IT equipment
Property, plant and equipment
Estimated useful life	3 years
Minimum | Office and lab equipment
Property, plant and equipment
Estimated useful life	3 years
Maximum | Office and lab equipment
Property, plant and equipment
Estimated useful life	5 years

Significant accounting polici21

Significant accounting policies - Retirement Benefits (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Significant accounting policies
Historical minimum guaranteed rates of return on employer contributions	3.25%
Historical minimum guaranteed rates of return on employee contributions	3.75%
Minimum return rate on defined contribution pension plans	1.75%	1.75%
Maximum return rate on defined contribution pension plans	3.75%	3.75%

Critical accounting judgement22

Critical accounting judgements and key sources of estimation uncertainty - (Details) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Critical accounting judgements and key sources of estimation uncertainty
Cash and cash equivalents	€ 190,867	€ 89,897	€ 35,514	€ 32,180
Cash and cash equivalents and current financial assets	€ 359,800

Notes relating to the consolida

Notes relating to the consolidated statement of financial position (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible assets
Intangible assets other than goodwill at beginning of period	€ 17	€ 7
Intangible assets other than goodwill at end of period	13	17	€ 7
Commitments to acquire additional intangible assets	0
Intangible assets are pledged as security	0
Software
Intangible assets
Intangible assets other than goodwill at beginning of period	17	7	7
Additions	6	21	5
Amortization	(10)	(11)	(5)
Intangible assets other than goodwill at end of period	13	17	7
Cost | Software
Intangible assets
Intangible assets other than goodwill at beginning of period	93	72	67
Intangible assets other than goodwill at end of period	99	93	72
Accumulated depreciation and amortization | Software
Intangible assets
Intangible assets other than goodwill at beginning of period	76	65	60
Intangible assets other than goodwill at end of period	€ 86	€ 76	€ 65

Notes relating to the consoli24

Notes relating to the consolidated statement of financial position - PPE (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, plant and equipment
Property, plant and equipment at beginning of period	€ 766	€ 249	€ 166
Additions	346	840	274
Sales and disposals	(69)
Depreciation	(425)	(323)	(191)
Property, plant and equipment at end of period	676	766	249
Commitments to acquire property, plant and equipment	0
Assets are pledged as security for liabilities	0
Other non-current financial assets
Realized gain on non-current financial assets	875
Other non-current assets
Other non-current assets	125
Other current assets	800
Other current receivables	750
FairJourney Biologics LDA
Other non-current assets
Total receivable in relation with the sale of minority participation	900
IT equipment
Property, plant and equipment
Property, plant and equipment at beginning of period	104	27	15
Additions	25	115	30
Depreciation	(53)	(38)	(18)
Property, plant and equipment at end of period	76	104	27
Office and lab equipment
Property, plant and equipment
Property, plant and equipment at beginning of period	662	222	151
Additions	321	725	244
Sales and disposals	(69)
Depreciation	(372)	(285)	(173)
Property, plant and equipment at end of period	600	662	222
Cost
Property, plant and equipment
Property, plant and equipment at beginning of period	2,112	1,272	998
Property, plant and equipment at end of period	2,389	2,112	1,272
Cost | IT equipment
Property, plant and equipment
Property, plant and equipment at beginning of period	208	93	63
Property, plant and equipment at end of period	233	208	93
Cost | Office and lab equipment
Property, plant and equipment
Property, plant and equipment at beginning of period	1,904	1,179	935
Property, plant and equipment at end of period	2,156	1,904	1,179
Accumulated depreciation and amortization
Property, plant and equipment
Property, plant and equipment at beginning of period	1,346	1,023	832
Sales and disposals	58
Property, plant and equipment at end of period	1,713	1,346	1,023
Accumulated depreciation and amortization | IT equipment
Property, plant and equipment
Property, plant and equipment at beginning of period	104	66	48
Property, plant and equipment at end of period	157	104	66
Accumulated depreciation and amortization | Office and lab equipment
Property, plant and equipment
Property, plant and equipment at beginning of period	1,242	957	784
Sales and disposals	58
Property, plant and equipment at end of period	€ 1,556	€ 1,242	€ 957

Notes relating to the consoli25

Notes relating to the consolidated statement of financial position - Research and development incentive receivables (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes relating to the consolidated statement of financial position
Research and development incentive receivables	€ 158	€ 163
Research and development incentive receivables	3,033	2,046	€ 1,568
Total	€ 3,191	€ 2,209	€ 1,568
Minimum refund period of research and development incentive receivables.	5 years	5 years

Notes relating to the consoli26

Notes relating to the consolidated statement of financial position - Non‑current restricted cash (Details) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016
Notes relating to the consolidated statement of financial position
Rental guarantees	€ 256	€ 244
Escrow account more than year		905
Total non‑current	256	1,149
Escrow account less than 1 year	1,692	786
Total restricted cash	€ 1,948	€ 1,935

Notes relating to the consoli27

Notes relating to the consolidated statement of financial position - Trade and other receivables (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Trade and other receivables
VAT receivable	€ 317	€ 278	€ 175
Trade receivables	845	1,118	719
Other receivables	750
Interest receivable		6	17
VLAIO grant receivable	930	568	445
Total trade and other current receivables	2,842	1,970	1,356
Government grant received from Flanders Innovation and Entrepreneurship Agency	422	€ 779	€ 1,598
Flanders Innovation and Entrepreneurship Agency
Trade and other receivables
Government grant received from Flanders Innovation and Entrepreneurship Agency	0
FairJourney Biologics LDA
Trade and other receivables
Other assets	€ 900

Notes relating to the consoli28

Notes relating to the consolidated statement of financial position - Prepaid expenses and Other current financial assets (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes relating to the consolidated statement of financial position
Prepaid expenses	€ 2,338	€ 2,146	€ 454
Prepaid upfront reservation fee	1,000
Prepaid expenses relate to a license fee paid	500
Prepaid insurance and other expense	900
Other current financial assets
Financial assets	€ 168,907	€ 6,831	€ 6,813
Maturity Term	6 months

Notes relating to the consoli29

Notes relating to the consolidated statement of financial position - Cash and cash equivalents (Details) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Notes relating to the consolidated statement of financial position
Cash equivalents	€ 25,000	€ 54,500	€ 11,006
Cash and bank balances	165,867	35,397	24,508
Total cash and cash equivalents	€ 190,867	€ 89,897	€ 35,514	€ 32,180

Notes relating to the consoli30

Notes relating to the consolidated statement of financial position - Shareholders’ capital (Details)	Dec. 18, 2017shares	Dec. 15, 2017EUR (€)shares	Dec. 14, 2017$ / sharesshares	Dec. 13, 2017shares	Dec. 04, 2017shares	Nov. 22, 2017shares	Nov. 21, 2017shares	Nov. 15, 2017shares	Nov. 14, 2017shares	Nov. 07, 2017shares	Oct. 02, 2017shares	Sep. 01, 2017shares	Aug. 24, 2017shares	May 19, 2017EUR (€)shares	May 17, 2017$ / sharesshares	Oct. 17, 2016shares	Sep. 26, 2016shares	May 27, 2016shares	Apr. 21, 2016shares	Mar. 16, 2016shares	Feb. 15, 2016shares	Jan. 20, 2016shares	Dec. 31, 2017€ / sharesshares	Jun. 30, 2016shares	Jan. 31, 2016shares	Dec. 31, 2017EUR (€)€ / sharesshares	Dec. 31, 2016EUR (€)€ / sharesshares	Dec. 31, 2015shares
Disclosure of classes of share capital [line items]
Number of shares outstanding at beginning of period																									15,802,767	20,126,479	15,802,767	15,705,112
New shares issued for private placement, initial public offering, public offering and underwriters' over-allotment option		666,000	4,440,000	4,440,000										879,750	5,865,000							1,480,420		2,703,000	1,480,420	5,106,000
Exercise of Options	9,850		666,000		65,380	7,730	53,092	40,750	4,260	950	1,400	15,000	5,000	879,750		15,000	70,000	33,092	10,000	10,000	2,200							97,655
Number of shares outstanding at end of period																							32,180,641			32,180,641	20,126,479	15,802,767
Share price | $ / shares			$ 52												$ 17
Number of shares on conversion															1											1
Gross proceeds from issue of shares | €		€ 225,600,000												€ 102,100,000
Underwriter discounts and commissions, and offering expenses | €		14,300,000												9,600,000
Expenses deducted from equity | €		14,100,000												8,900,000
Net proceeds | €		€ 211,300,000												€ 92,500,000
Par value per share | € / shares																							€ 0.1			€ 0.1	€ 0.1
Unissued authorized capital | €																											€ 4,500,000
Number of shares authorised																											45
Maximum authorized increase of then outstanding share capital (as a percent)																										20.00%
Period of outstanding share capital																										18 months
Maximum authorized increase in share capital | €																										€ 537,852.60
Maximum authorized increase in number of shares																										5,378,526
Number of shares covered by existing authorization																										272,526
Employee Stock Option
Disclosure of classes of share capital [line items]
Exercise of Options																							203,412				140,292
Private placement (Sunflower)
Disclosure of classes of share capital [line items]
New shares issued for private placement, initial public offering, public offering and underwriters' over-allotment option																											2,703,000

Notes relating to the consoli31

Notes relating to the consolidated statement of financial position - Share‑based payments (Details)	May 17, 2017shares	Dec. 31, 2017EUR (€)EquityInstrumentsshares	Dec. 31, 2016EUR (€)EquityInstruments	Dec. 31, 2015EUR (€)EquityInstruments	Jun. 30, 2017EUR (€)	Jun. 30, 2016EUR (€)	May 31, 2016EUR (€)	Sep. 30, 2015EUR (€)	Jun. 30, 2015EUR (€)	Dec. 31, 2014EquityInstruments
Disclosure of terms and conditions of share-based payment arrangement [line items]
Options expired		0	0	0
Number of shares on conversion | shares	1	1
Vesting period		24 months
Exercise price per stock options | €		€ 21.17	€ 14.130	€ 9.47	€ 18.41	€ 11.38	€ 11.47	€ 10.34	€ 11.44
Outstanding options on December 31,		2,862,216	2,293,636	1,752,926						1,595,015
Tranche One
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting percentage		33.00%
Tranche Two
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting percentage		2.79%
Percentage of stock options granted		67.00%
3.95 | 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 3.95
Outstanding options on December 31,				103,370
3.95 | 2020
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 3.95
Outstanding options on December 31,		36,960	112,738	62,460
3.95 | 2021
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 3.95
Outstanding options on December 31,		2,850	3,800	3,800
3.95 | 2023
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 3.95
Outstanding options on December 31,				55,747
3.95 | 2024
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 3.95
Outstanding options on December 31,		15,692	55,746
2.44 - Expiry date 2024 option 1 | 2022
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 2.44
Outstanding options on December 31,				686,732
2.44 - Expiry date 2024 option 1 | 2024
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 2.44
Outstanding options on December 31,		314,593	360,787
2.44 - Expiry date 2024 option 2 | 2024
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 2.44
Outstanding options on December 31,		135,890	169,926
2.44 - Expiry date 2024 option 3 | 2024
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 2.44
Outstanding options on December 31,		83,820	83,820
7.17 | 2024
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 7.17
Outstanding options on December 31,		516,100	522,500	537,917
11.44 | 2025
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 11.44
Outstanding options on December 31,		39,000	39,000	56,500
10.34 | 2025
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 10.34
Outstanding options on December 31,		3,000	3,000	3,000
9.47 | 2025
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 9.47
Outstanding options on December 31,		235,514	235,733	243,400
11.38 | 2026
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 11.38
Outstanding options on December 31,		60,000	60,000
11.47 | 2026
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 11.47
Outstanding options on December 31,		282,310	283,360
14.13 | 2026
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 14.13
Outstanding options on December 31,		362,126	363,226
18.41 | 2027
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 18.41
Outstanding options on December 31,		120,536
21.17 | 2027
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €		€ 21.17
Outstanding options on December 31,		653,825

Notes relating to the consoli32

Notes relating to the consolidated statement of financial position - Share‑based payments - Rollforward (Details)	1 Months Ended								12 Months Ended
	Dec. 31, 2017EUR (€)EquityInstruments	Jun. 30, 2017EquityInstruments	Dec. 31, 2016EUR (€)EquityInstrumentsY	Jun. 30, 2016EquityInstruments	May 31, 2016EquityInstruments	Dec. 31, 2015EUR (€)EquityInstrumentsY	Sep. 30, 2015EquityInstruments	Jun. 30, 2015EquityInstruments	Dec. 31, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstrumentsY	Dec. 31, 2015EUR (€)EquityInstrumentsY
Number of stock options
Total options at beginning of year | EquityInstruments									2,293,636	1,752,926	1,595,015
Granted | EquityInstruments	653,825	120,536	363,226	60,000	288,950	243,400	3,000	56,500	774,361	712,176	302,900
Exercised | EquityInstruments									(203,412)	(140,292)	(97,656)
Forfeited | EquityInstruments									(2,369)	(31,174)	(47,333)
Total options at end of year | EquityInstruments	2,862,216		2,293,636			1,752,926			2,862,216	2,293,636	1,752,926
Exercisable | EquityInstruments	1,598,829		1,257,091			1,366,703			1,598,829	1,257,091	1,366,703
Weighted average exercise price
Beginning balance | €									€ 7.72	€ 5.37	€ 4.39
Granted | €									20.74	12.82	9.84
Exercised | €									3.46	3.52	2.44
Forfeited | €									12.52	10.90	7.17
Ending balance | €	€ 11.54		€ 7.72			€ 5.37			11.54	7.72	5.37
Exercisable | €	€ 6.80		€ 4.68			€ 4.41			€ 6.80	€ 4.68	€ 4.41
Weighted average remaining contractual life of outstanding share options | Y			8.03			8.09				8.03	8.09

Notes relating to the consoli33

Notes relating to the consolidated statement of financial position - Share‑based payments - Range of excercise price (Details)	Dec. 31, 2017EUR (€)EquityInstrumentsY	Jun. 30, 2017EUR (€)	Dec. 31, 2016EUR (€)EquityInstrumentsY	Jun. 30, 2016EUR (€)	May 31, 2016EUR (€)	Dec. 31, 2015EUR (€)EquityInstrumentsY	Sep. 30, 2015EUR (€)	Jun. 30, 2015EUR (€)	Dec. 31, 2014EquityInstruments
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	€ 21.17	€ 18.41	€ 14.130	€ 11.38	€ 11.47	€ 9.47	€ 10.34	€ 11.44
Number of share options outstanding in share-based payment arrangement | EquityInstruments	2,862,216		2,293,636			1,752,926			1,595,015
Weighted average remaining contractual life | Y			8.03			8.09
2.44–3.95
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of share options outstanding in share-based payment arrangement | EquityInstruments	589,805
Weighted average remaining contractual life | Y	5.81
7.17–9.47
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of share options outstanding in share-based payment arrangement | EquityInstruments	751,614
Weighted average remaining contractual life | Y	7.28
10.33–14.13
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of share options outstanding in share-based payment arrangement | EquityInstruments	746,436
Weighted average remaining contractual life | Y	8.62
18.41–21.17
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of share options outstanding in share-based payment arrangement | EquityInstruments	774,361
Weighted average remaining contractual life | Y	9.88
Minimum | 2.44–3.95
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	€ 2.44
Minimum | 7.17–9.47
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	7.17
Minimum | 10.33–14.13
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	10.33
Minimum | 18.41–21.17
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	18.41
Maximum | 2.44–3.95
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	3.95
Maximum | 7.17–9.47
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	9.47
Maximum | 10.33–14.13
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	14.13
Maximum | 18.41–21.17
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	€ 21.17

Notes relating to the consoli34

Notes relating to the consolidated statement of financial position - Share‑based payments - Overview (Details)	1 Months Ended								12 Months Ended
	Dec. 31, 2017EUR (€)EquityInstrumentsY	Jun. 30, 2017EUR (€)EquityInstrumentsY	Dec. 31, 2016EUR (€)EquityInstrumentsY	Jun. 30, 2016EUR (€)EquityInstrumentsY	May 31, 2016EUR (€)EquityInstrumentsY	Dec. 31, 2015EUR (€)EquityInstrumentsY	Sep. 30, 2015EUR (€)EquityInstrumentsY	Jun. 30, 2015EUR (€)EquityInstrumentsY	Dec. 31, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments	Dec. 31, 2015EUR (€)EquityInstruments
Notes relating to the consolidated statement of financial position
Number of options granted | EquityInstruments	653,825	120,536	363,226	60,000	288,950	243,400	3,000	56,500	774,361	712,176	302,900
Average fair value of options	€ 37.10	€ 7.90	€ 7.25	€ 5.46	€ 5.32	€ 6.25	€ 6.79	€ 7.79	€ 37.10	€ 7.25	€ 6.25
Share price	53.50	17.76	14.96	11.36	11.10	9.85	10.24	11.58
Exercise price	€ 21.17	€ 18.41	€ 14.130	€ 11.38	€ 11.47	€ 9.47	€ 10.34	€ 11.44	21.17	14.130	9.47
Expected volatility	36.10%	36.60%	38.00%	39.60%	40.20%	58.00%	59.00%	59.00%
Average expected option life (in years) | Y	10	10	10	10	10	10	10	10
Risk‑free interest rate	0.53%	0.61%	0.67%	0.46%	0.52%	0.98%	1.08%	1.21%
Total share based payment expense									€ 4,300,000	€ 2,800,000	€ 2,300,000

Notes relating to the consoli35

Notes relating to the consolidated statement of financial position - Defined Benefit Plans (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of net defined benefit liability (asset) [line items]
Minimum guaranteed reserve			€ 10
Deficit / surplus (−) of funded obligations	€ 25	€ 1
Net liability (asset)	25	1
Defined benefit obligation
Disclosure of net defined benefit liability (asset) [line items]
Net liability (asset)	1,007	670	486
Fair value of plan assets
Disclosure of net defined benefit liability (asset) [line items]
Net liability (asset)	€ 982	€ 669	€ 486
Belgium
Disclosure of net defined benefit liability (asset) [line items]
Guaranteed rate of return on employer contributions	3.25%
Guaranteed rate of return on employee contributions	3.75%
Minimum | Belgium
Disclosure of net defined benefit liability (asset) [line items]
Guaranteed rate of return on employer contributions	1.75%
Maximum | Belgium
Disclosure of net defined benefit liability (asset) [line items]
Guaranteed rate of return on employer contributions	3.75%

Notes relating to the consoli36

Notes relating to the consolidated statement of financial position - Defined Benefit Plans - Rollforward (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of net defined benefit liability (asset) [line items]
Beginning balance	€ 1
Ending balance	€ 25	€ 1
Discount rate	1.30%	1.30%
Term of Benefit Obligations	21 years
Weighted average age of the plan participants	46 years	48 years
Defined benefit obligation
Disclosure of net defined benefit liability (asset) [line items]
Beginning balance	€ 670	€ 486
Service cost	352	113
Interest expense / income (−)	11	6
Contributions by plan participants	(148)	(64)
Actuarial gains (+) / losses (-)	124	131
Benefits paid / transfers out	(2)	(2)
Ending balance	1,007	670
Fair value of plan assets
Disclosure of net defined benefit liability (asset) [line items]
Beginning balance	669	486
Interest expense / income (−)	10	7
Administrative costs and taxes	(46)	(19)
Contributions by company & participants	423	176
Contributions by plan participants	(148)	(64)
Actuarial gains (+) / losses (-)	76	85
Benefits paid / transfers out	(2)	(2)
Ending balance	€ 982	€ 669

Notes relating to the consoli37

Notes relating to the consolidated statement of financial position - Defined Benefit Plans - Sensitivity Analysis (Details) - Discount rate	12 Months Ended
	Dec. 31, 2017EUR (€)
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Decrease in percentage	0.25%
Increase in percentage	0.25%
Defined benefit obligation increase due to increase in discount rate	€ 35,900
Defined benefit obligation decrease due to decrease in discount rate	€ 31,000
Defined benefit obligation increase (in percentage)	3.56%
Defined benefit obligation decrease (in percentage)	(3.08%)

Notes relating to the consoli38

Notes relating to the consolidated statement of financial position - Current tax liability (Details) - EUR (€) € in Thousands	Mar. 23, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of subsidiaries [line items]
Arm’s length compensation	€ 79,900
Tax losses carryforward limit	77,500
Loss before taxes		€ (27,479)	€ (21,374)	€ (15,312)
Current tax liabilities		€ 597
Applicable tax rate		25.00%
Deferred tax asset recognized		€ 113,600
ARGENX BVBA
Disclosure of subsidiaries [line items]
Arm’s length compensation	79,900
Tax losses carryforward limit	€ 77,500
Current tax liabilities		600
Applicable tax rate	25.00%
Additional tax deductible costs		79,900
Deferred tax asset recognized		€ 0

Notes relating to the consoli39

Notes relating to the consolidated statement of financial position - Trade and other payables (Details) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes relating to the consolidated statement of financial position
Trade payables	€ 4,395	€ 4,385	€ 1,886
Accruals for invoices to be received	4,046	5,444	1,239
Short-term employee benefits accruals	6,844	2,362	1,418
Total	€ 15,285	€ 12,191	€ 4,543

Notes relating to the consoli40

Notes relating to the consolidated statement of financial position - Deferred revenues (Details) - EUR (€) € in Thousands	1 Months Ended		12 Months Ended
	Apr. 30, 2016	May 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of offsetting of financial assets [line items]
Deferred revenue			€ 10,070	€ 30,206	€ 4,141
Upfront Payments Received			€ 20,137	€ 9,103	€ 2,194
AbbVie
Disclosure of offsetting of financial assets [line items]
Upfront Payments Received	€ 9,800
LEO Pharma collaboration
Disclosure of offsetting of financial assets [line items]
Upfront Payments Received		€ 300

Notes to consolidated stateme41

Notes to consolidated statement of profit and loss and other comprehensive income (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes to consolidated statement of profit and loss and other comprehensive income
Upfront payments	€ 20,137	€ 9,103	€ 2,194
Milestone payments	9,677	500	343
Research and development service fees (FTE)	6,601	5,110	4,317
Total revenue	€ 36,415	€ 14,713	€ 6,854

Notes to consolidated stateme42

Notes to consolidated statement of profit and loss and other comprehensive income - Revenue (Details) € in Thousands, $ in Millions	May 30, 2014EUR (€)	Apr. 30, 2016USD ($)item	Apr. 30, 2016EUR (€)item	May 31, 2015EUR (€)	Jul. 31, 2014EUR (€)	Jan. 31, 2014item	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)	Dec. 31, 2015EUR (€)
Disclosure of detailed information about business combination [line items]
Milestone payments							€ 9,677	€ 500	€ 343
Research and development service fees (FTE)							6,601	€ 5,110	€ 4,317
Proceeds from issue of shares							308,700
Shire
Disclosure of detailed information about business combination [line items]
Research and development service fees (FTE)							2,100
Number of extra discovery milestone payments received | item						2
Upfront cash payment received	€ 3,000
Proceeds from issue of shares					€ 12,000
LEO Pharma collaboration
Disclosure of detailed information about business combination [line items]
Research and development service fees (FTE)							3,900
Pre-IND payments including upfront payments received				€ 4,500
Staten
Disclosure of detailed information about business combination [line items]
Research and development service fees (FTE)							€ 600
AbbVie
Disclosure of detailed information about business combination [line items]
Upfront, non-refundable, non-creditable payment received		$ 40	€ 35,100
Number of preclinical milestones achieved | item		2	2
Amount of preclinical milestone payment received		$ 10	€ 8,900
Amount of each near-term preclinical milestone payment | $		10
Maximum additional development milestone payments | $		110
Maximum additional regulatory milestone payments | $		190
Maximum additional commercial milestone payments | $		$ 325
Term of additional GARP-related research funding		2 years	2 years
Period after first commercial sale for expiry of royalty payment obligation		10 years	10 years

Notes to consolidated stateme43

Notes to consolidated statement of profit and loss and other comprehensive income - Other operating income (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes to consolidated statement of profit and loss and other comprehensive income
Grants	€ 422	€ 779	€ 1,598
Research and development incentives	983	641	608
Payroll tax rebates	3,436	1,019	895
Total	€ 4,841	€ 2,439	€ 3,101

Notes to consolidated stateme44

Notes to consolidated statement of profit and loss and other comprehensive income - Other operating income - Grants (Details) € in Thousands	Dec. 31, 2017EUR (€)item
Other operating income - Grants
Number of conditions related to government grants that are unfulfilled | item	0
Flanders Innovation & Entrepreneurship TGO
Other operating income - Grants
Amount granted and approved	€ 2,697
Amount recognized	2,697
Flanders Innovation & Entrepreneurship—Baekelandt
Other operating income - Grants
Amount granted and approved	277
Amount recognized	270
Flanders Innovation & Entrepreneurship 4
Other operating income - Grants
Amount granted and approved	1,568
Amount recognized	€ 1,568

Notes to consolidated stateme45

Notes to consolidated statement of profit and loss and other comprehensive income - Other operating income - Other Incentives (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes to consolidated statement of profit and loss and other comprehensive income
Research and development incentives	€ 983	€ 641	€ 608
Incentive refund period	5 years
Payroll tax rebates	€ 3,436	€ 1,019	€ 895

Notes to consolidated stateme46

Notes to consolidated statement of profit and loss and other comprehensive income - Segment reporting (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes to consolidated statement of profit and loss and other comprehensive income
Revenue from external customers	€ 36,415	€ 14,713	€ 6,854
Non-current assets	4,104	3,979	1,825
Netherlands
Notes to consolidated statement of profit and loss and other comprehensive income
Revenue from external customers	628	548	275
Germany
Notes to consolidated statement of profit and loss and other comprehensive income
Revenue from external customers		311	2,190
Denmark
Notes to consolidated statement of profit and loss and other comprehensive income
Revenue from external customers	6,240	3,066	827
Switzerland
Notes to consolidated statement of profit and loss and other comprehensive income
Revenue from external customers	2,486	3,315	3,127
United States
Notes to consolidated statement of profit and loss and other comprehensive income
Revenue from external customers	1	47	€ 435
Luxembourg
Notes to consolidated statement of profit and loss and other comprehensive income
Revenue from external customers	€ 27,060	€ 7,426

Notes to consolidated stateme47

Notes to consolidated statement of profit and loss and other comprehensive income - Segment reporting - Major clients (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment reporting - Major clients
Revenue	€ 36,415	€ 14,713	€ 6,854
Largest client
Segment reporting - Major clients
Revenue	27,100	7,400
Second largest client
Segment reporting - Major clients
Revenue	6,200	3,300
Third largest client
Segment reporting - Major clients
Revenue	€ 2,500	€ 3,100

Notes to consolidated stateme48

Notes to consolidated statement of profit and loss and other comprehensive income - Research and development expenses (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes to consolidated statement of profit and loss and other comprehensive income
Personnel expenses	€ 16,473	€ 9,844	€ 6,665
External research and development expenses	27,893	17,562	11,653
Materials and consumables	1,562	1,180	1,050
Depreciation and amortisation	446	335	196
Other expenses	5,366	2,636	1,071
Research and development expenses	€ 51,740	€ 31,557	€ 20,635

Notes to consolidated stateme49

Notes to consolidated statement of profit and loss and other comprehensive income - General and administrative expenses (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes to consolidated statement of profit and loss and other comprehensive income
Personnel expenses	€ 6,745	€ 3,256	€ 1,607
Consulting fees	3,289	2,563	2,395
Supervisory board	621	446	165
Office costs	1,793	746	758
Total	€ 12,448	€ 7,011	€ 4,925

Notes to consolidated stateme50

Notes to consolidated statement of profit and loss and other comprehensive income - Personnel expenses (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes to consolidated statement of profit and loss and other comprehensive income
Short-term employee benefits - Salaries	€ 12,149	€ 8,527	€ 5,192
Short-term employee benefits - Social Security	1,504	1,027	802
Post-employment benefits	291	175	207
Termination benefits	8	86	124
Share-based payment	3,985	2,849	1,945
Employer social security contributions stock options	5,281	436
Total employee benefits expense	€ 23,218	€ 13,100	€ 8,270

Notes to consolidated stateme51

Notes to consolidated statement of profit and loss and other comprehensive income - Personnel expenses FTE (Details) - employee	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes to consolidated statement of profit and loss and other comprehensive income
Research and development	56.8	46.9	31.4
General and administrative	14.7	9.9	5.8
Number of FTE	71.5	56.8	37.2

Notes to consolidated stateme52

Notes to consolidated statement of profit and loss and other comprehensive income - Operating leases (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating leases
Operating lease payments recognized as expense	€ 1,200	€ 900
Operating lease payments recognized as expense in research and development expenses	300	200
Operating lease payments recognized as expense in selling, general and administrative expenses	900	700
Operating lease commitments	€ 1,526	2,098	€ 1,902
Cars | Maximum
Operating leases
Maturity term of lease	4 years
Laboratory and office space
Operating leases
Maturity term of lease	9 years
Minimum period of notice for lease termination	12 months
First anniversary of lease termination possibility	3 years
Second anniversary of lease termination possibility	6 years
Less than 1 year
Operating leases
Operating lease commitments	€ 1,028	915	630
1-3 years
Operating leases
Operating lease commitments	465	1,159	1,130
3-5 years
Operating leases
Operating lease commitments	€ 33	€ 24	€ 142

Notes to consolidated stateme53

Notes to consolidated statement of profit and loss and other comprehensive income - Financial result and exchange gains/(losses) (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes to consolidated statement of profit and loss and other comprehensive income
Interest income on bank deposits	€ 165	€ 61	€ 76
Net gains on investments at FVTPL	210	12	36
Realized gain on non-current financial assets	875
Financial income	1,250	73	112
Exchange gains/(losses)	€ (5,797)	€ (31)	€ 181

Notes to consolidated stateme54

Notes to consolidated statement of profit and loss and other comprehensive income - Income tax expense (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes to consolidated statement of profit and loss and other comprehensive income
Loss before taxes	€ (27,479)	€ (21,374)	€ (15,312)
Income tax calculated at 25%	(6,870)	(5,344)	(3,828)
Effect of expenses that are not deductible in determining taxable results	(1,141)	(755)	(568)
Effect of stock issue expenses that are not deductible in determining taxable results	(5,754)	(462)
Effect of concessions (R&D incentives and grants)	(453)	(463)	(759)
Effect of different tax rates in jurisdictions in which the company operates	(517)	(180)	(122)
Deferred tax asset other than loss carryforwards not recognized	(4,363)
Other	(9)	(22)	(5)
Income tax expense recognized in the consolidated statement of profit and loss	(597)
Netherlands
Notes to consolidated statement of profit and loss and other comprehensive income
Effect of tax losses carried forward not recognized		(5,551)	(3,601)
Effect of usage of tax losses carried forward not previously recognized	19,378
Belgium
Notes to consolidated statement of profit and loss and other comprehensive income
Effect of tax losses carried forward not recognized	(27,413)		€ (301)
Effect of usage of tax losses carried forward not previously recognized		€ 195
Effect of change in corporate tax rate on deferred tax asset not previously recognized (Belgium)	€ 373

Notes to consolidated stateme55

Notes to consolidated statement of profit and loss and other comprehensive income - Income tax expense - Deferred tax assets (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income tax expense - Deferred tax assets
Unused tax losses for which no deferred tax asset recognised			€ 113,600
Unused tax loss carried forward, which will expire in 2026			€ 1,300
Tax rate applicable			25.00%
Temporary differences and unused tax losses
Income tax expense - Deferred tax assets
Unrecognized deferred tax assets			€ 28,400	€ 21,000
Unused tax credits
Income tax expense - Deferred tax assets
Unrecognized deferred tax assets			€ 10	€ 6,600
Netherlands
Income tax expense - Deferred tax assets
Tax rate applicable			25.00%
Belgium
Income tax expense - Deferred tax assets
Tax rate applicable	25.00%	29.58%	33.99%

Notes to consolidated stateme56

Notes to consolidated statement of profit and loss and other comprehensive income - Income tax expense - Restructuring (Details) - EUR (€) € in Thousands	Mar. 23, 2017	Dec. 31, 2017
Notes to consolidated statement of profit and loss and other comprehensive income
Arm’s length compensation	€ 79,900
Tax losses carryforward limit	77,500
Tax rate applicable		25.00%
Current tax liabilities		€ 597
ARGENX BVBA
Notes to consolidated statement of profit and loss and other comprehensive income
Arm’s length compensation	79,900
Tax losses carryforward limit	77,500
Restructuring estimated taxable amount	€ 2,300
Tax rate applicable	25.00%
Current tax liabilities		600
Additional tax deductible costs		€ 79,900

Notes to consolidated stateme57

Notes to consolidated statement of profit and loss and other comprehensive income - Loss per share (Details) - EUR (€) € / shares in Units, € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes to consolidated statement of profit and loss and other comprehensive income
Loss of the year	€ (28,076)	€ (21,374)	€ (15,312)
Weighted average number of shares outstanding	24,609,536	18,820,612	15,734,007
Basic and diluted loss per share	€ (1.14)	€ (1.14)	€ (0.97)

Financial instruments and fin58

Financial instruments and financial risk management (Details) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of financial assets [line items]
Non-current financial assets	€ 1	€ 1	€ 1
Current financial assets	168,907	6,831	6,813
Total financial assets	168,908	6,832	6,814
Total financial assets including loans and receivables	364,690	100,635	43,684
Financial assets, at fair value	168,908	6,832	6,814
Total financial assets, including loans and receivables at fair value	364,690	100,635	43,684
Current financial liabilities	15,310	12,192	4,543
Financial liabilities , Fair value	15,310	12,192	4,543
Investments
Disclosure of financial assets [line items]
Non-current financial assets	1	1	1
Non Current Financial Assets at Fair Value	1	1	1
Debt securities
Disclosure of financial assets [line items]
Current financial assets	168,907	6,831	6,813
Current Financial assets, at fair value	168,907	6,831	6,813
Other Noncurrent Assets
Disclosure of financial assets [line items]
Non-current financial assets	125
Non Current Financial Assets at Fair Value	125
Trade and other receivables
Disclosure of financial assets [line items]
Current financial assets	2,842	1,970	1,356
Current Financial assets, at fair value	2,842	1,970	1,356
Cash and cash equivalents
Disclosure of financial assets [line items]
Current financial assets	190,867	89,897	35,514
Current Financial assets, at fair value	190,867	89,897	35,514
Non‑current restricted cash
Disclosure of financial assets [line items]
Non-current financial assets	256	1,149
Non Current Financial Assets at Fair Value	256	1,149
Current restricted cash
Disclosure of financial assets [line items]
Current financial assets	1,692	787
Current Financial assets, at fair value	1,692	787
Loans and receivables
Disclosure of financial assets [line items]
Total financial assets	195,782	93,803	36,870
Financial assets, at fair value	195,782	93,803	36,870
Provision for employee benefits
Disclosure of financial assets [line items]
Current financial liabilities	25	1
Financial liabilities , Fair value	25	1
Trade and other payables
Disclosure of financial assets [line items]
Current financial liabilities	15,285	12,191	4,543
Financial liabilities , Fair value	15,285	12,191	4,543
Financial liabilities at amortized cost
Disclosure of financial assets [line items]
Current financial liabilities	15,310	12,192	4,543
Financial liabilities , Fair value	€ 15,310	€ 12,192	€ 4,543

Financial instruments and fin59

Financial instruments and financial risk management - Fair value (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of fair value measurement of assets [line items]
Assets carried at fair value	€ 168,908	€ 6,832	€ 6,814
Assets carried at fair value	168,908	6,832	6,814
Transfers out of Level 1 to Level 2 assets	0
Transfers out of Level 1 to Level 2 liabilities	0
Transfers out of Level 2 to Level 1 assets	0
Transfers out of Level 2 to Level 1 liabilities	0
Transfer into level 3 assets	0
Transfer out of level 3 assets	0
Transfer into level 3 liabilities	0
Transfer out of level 3 liabilities	0
Level 1
Disclosure of fair value measurement of assets [line items]
Current financial assets	168,907	6,831	6,813
Assets carried at fair value	168,907	6,831	6,813
Assets carried at fair value	€ 168,907	6,831	6,813
Level 3
Disclosure of fair value measurement of assets [line items]
Non-current financial assets		1	1
Assets carried at fair value		1	1
Assets carried at fair value		€ 1	€ 1

Financial instruments and fin60

Financial instruments and financial risk management - Capital risk (Details) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financial instruments and financial risk management
Cash and cash equivalents	€ 190,867	€ 89,897	€ 35,514	€ 32,180
Total capital		€ 433,700

Financial instruments and fin61

Financial instruments and financial risk management - Credit risk (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of financial assets that are either past due or impaired [line items]
Financial assets	€ 168,908	€ 6,832	€ 6,814
Credit risk | Financial assets past due but not impaired
Disclosure of financial assets that are either past due or impaired [line items]
Financial assets	0
Credit risk | Financial assets impaired
Disclosure of financial assets that are either past due or impaired [line items]
Financial assets	€ 0
Credit risk | Maximum
Disclosure of financial assets that are either past due or impaired [line items]
Recommended maturity term for short term investment	6 months

Financial instruments and fin62

Financial instruments and financial risk management - Interest rate risk (Details) - Interest rate risk - EUR (€) € in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of risk management strategy related to hedge accounting [line items]
Increase decrease in basis points	0.25%
Positive/negative impact	€ 0.3	€ 0.1	€ 0.1

Financial instruments and fin63

Financial instruments and financial risk management - Foreign exchange risk (Details) - Currency risk - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of risk management strategy related to hedge accounting [line items]
Sensitivity rate reported to key management personnel	10.00%
USD
Disclosure of risk management strategy related to hedge accounting [line items]
Net exposure to exchange differences of the monetary assets	€ 147,169	€ 624	€ 345
Percentage of reasonably possible increase in risk assumption	10.00%	10.00%
Percent of reasonably possible decrease in risk assumption	10.00%	10.00%
Increase (decrease) in financial instrument due to reasonably possible increase in designated risk component	€ (13,380)	€ (60)
Increase (decrease) in financial instrument due to reasonably possible decrease in designated risk component	13,380	€ 60
GBP
Disclosure of risk management strategy related to hedge accounting [line items]
Net exposure to exchange differences of the monetary assets	€ 406
Percentage of reasonably possible increase in risk assumption	10.00%
Percent of reasonably possible decrease in risk assumption	10.00%
Increase (decrease) in financial instrument due to reasonably possible increase in designated risk component	€ 0
Increase (decrease) in financial instrument due to reasonably possible decrease in designated risk component	€ 0

Other disclosures - Related par

Other disclosures - Related party transactions (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation of key management personnel
Short term employee benefits	€ 3,126	€ 1,832	€ 1,482
Post employment benefits	115	125	59
Termination benefits			124
Share‑based payment	12,041	2,261	1,761
Employer social security contributions stock options	3,073	436
Total	€ 18,355	€ 4,654	€ 3,426

Other disclosures - Related p65

Other disclosures - Related party transactions - Executive directors remuneration (Details) - EUR (€)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of transactions between related parties [line items]
Pension contribution	€ 115,000	€ 125,000	€ 59,000
Social security costs	3,073,000	436,000
ESOP	12,041,000	2,261,000	1,761,000
Total	18,355,000	4,654,000	3,426,000
Executive Directors
Disclosure of transactions between related parties [line items]
Base salary	575,285	489,236	439,419
Bonus	474,919	183,897	178,373
Pension contribution	76,650	96,901	70,787
Social security costs	264,191	146,408	142,381
ESOP	7,057,404	842,597	386,712
Other	24,580	9,184	9,210
Total	8,473,029	1,768,223	1,226,882
Tim Van Hauwermeiren
Disclosure of transactions between related parties [line items]
Base salary	303,941	253,284	217,260
Bonus	301,635	101,314	103,298
Pension contribution	14,315	11,929	8,690
Social security costs	9,459	10,284	8,760
ESOP	2,968,195	488,020	201,248
Other	9,601	9,184	9,210
Total	3,607,146	874,015	548,466
Eric Castaldi
Disclosure of transactions between related parties [line items]
Base salary	271,344	235,952	222,159
Bonus	173,284	82,583	75,075
Pension contribution	62,335	84,972	62,097
Social security costs	254,732	136,124	133,621
ESOP	4,089,209	786,035	185,464
Other	14,979
Total	€ 4,865,883	€ 1,325,666	€ 678,416

Other disclosures - Related p66

Other disclosures - Related party transactions - Executive directors ESOP (Details)	12 Months Ended
	Dec. 31, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments	Dec. 31, 2015EUR (€)EquityInstruments	Jun. 30, 2017EUR (€)	Jun. 30, 2016EUR (€)	May 31, 2016EUR (€)	Sep. 30, 2015EUR (€)	Jun. 30, 2015EUR (€)	Dec. 31, 2014EquityInstruments
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding options on December 31,	2,862,216	2,293,636	1,752,926						1,595,015
Exercise price | €	€ 21.17	€ 14.130	€ 9.47	€ 18.41	€ 11.38	€ 11.47	€ 10.34	€ 11.44
Exercised	203,412	140,292	97,656
Executive Directors
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding options on December 31,	123,200	137,000	58,800
Exercised	65,380	125,292
Tim Van Hauwermeiren | 9.47
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding options on December 31,			30,600
Term			10 years
Exercise price | €			€ 9.47
Tim Van Hauwermeiren | 11.47
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding options on December 31,		50,000
Term		10 years
Exercise price | €		€ 11.47
Tim Van Hauwermeiren | 14.13
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding options on December 31,		30,600
Term		10 years
Exercise price | €		€ 14.13
Tim Van Hauwermeiren | 3.95
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price | €		€ 3.95
Exercised		53,092
Tim Van Hauwermeiren | 2.44
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price | €	€ 2.44	€ 2.44
Exercised	65,380	72,200
Tim Van Hauwermeiren | 21.17
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding options on December 31,	80,000
Term	10 years
Exercise price | €	€ 21.17
Eric Castaldi | 9.47
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding options on December 31,			28,200
Term			10 years
Exercise price | €			€ 9.47
Eric Castaldi | 11.47
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding options on December 31,		28,200
Term		10 years
Exercise price | €		€ 11.47
Eric Castaldi | 14.13
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding options on December 31,		28,200
Term		10 years
Exercise price | €		€ 14.13
Eric Castaldi | 2.44
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding options on December 31,	273,807	230,607
Eric Castaldi | 21.17
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding options on December 31,	43,200
Term	10 years
Exercise price | €	€ 21.17

Other disclosures - Related p67

Other disclosures - Related party transactions - Executive directors ESOP - Rollforward and Vesting (Details)	1 Months Ended								12 Months Ended
	Dec. 31, 2017EUR (€)EquityInstruments	Jun. 30, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments	Jun. 30, 2016EUR (€)EquityInstruments	May 31, 2016EUR (€)EquityInstruments	Dec. 31, 2015EUR (€)EquityInstruments	Sep. 30, 2015EUR (€)EquityInstruments	Jun. 30, 2015EUR (€)EquityInstruments	Dec. 31, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments	Dec. 31, 2015EUR (€)EquityInstruments
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									2,293,636	1,752,926	1,595,015
Granted	653,825	120,536	363,226	60,000	288,950	243,400	3,000	56,500	774,361	712,176	302,900
Exercised									(203,412)	(140,292)	(97,656)
Total options at end of year	2,862,216		2,293,636			1,752,926			2,862,216	2,293,636	1,752,926
Exercise price | €	€ 21.17	€ 18.41	€ 14.130	€ 11.38	€ 11.47	€ 9.47	€ 10.34	€ 11.44	€ 21.17	€ 14.130	€ 9.47
Tim Van Hauwermeiren | 2.44
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercised									(65,380)	(72,200)
Exercise price | €	€ 2.44		€ 2.44						€ 2.44	€ 2.44
Tim Van Hauwermeiren | 7.17
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									281,580
Granted									80,000
Exercised									(65,380)
Total options at end of year	296,200		281,580						296,200	281,580
Tim Van Hauwermeiren | 7.17 | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	70,000								70,000
Exercise price | €	€ 7.17								€ 7.17
Tim Van Hauwermeiren | 7.17 | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	35,000								35,000
Exercise price | €	€ 7.17								€ 7.17
Tim Van Hauwermeiren | 9.47
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year										30,600
Total options at end of year						30,600					30,600
Exercise price | €						€ 9.47					€ 9.47
Tim Van Hauwermeiren | 9.47 | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	10,200								10,200
Exercise price | €	€ 9.47								€ 9.47
Tim Van Hauwermeiren | 9.47 | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	10,200								10,200
Exercise price | €	€ 9.47								€ 9.47
Tim Van Hauwermeiren | 9.47 | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	10,200								10,200
Exercise price | €	€ 9.47								€ 9.47
Tim Van Hauwermeiren | 11.47
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									50,000
Total options at end of year			50,000							50,000
Exercise price | €			€ 11.47							€ 11.47
Tim Van Hauwermeiren | 11.47 | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	26,389								26,389
Exercise price | €	€ 11.47								€ 11.47
Tim Van Hauwermeiren | 11.47 | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	16,667								16,667
Exercise price | €	€ 11.47								€ 11.47
Tim Van Hauwermeiren | 11.47 | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	6,944								6,944
Exercise price | €	€ 11.47								€ 11.47
Tim Van Hauwermeiren | 14.13
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									30,600
Total options at end of year			30,600							30,600
Exercise price | €			€ 14.13							€ 14.13
Tim Van Hauwermeiren | 14.13 | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	10,200								10,200
Exercise price | €	€ 14.13								€ 14.13
Tim Van Hauwermeiren | 14.13 | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	10,200								10,200
Exercise price | €	€ 14.13								€ 14.13
Tim Van Hauwermeiren | 14.13 | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	10,200								10,200
Exercise price | €	€ 14.13								€ 14.13
Tim Van Hauwermeiren | 21.17
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	80,000								80,000
Exercise price | €	€ 21.17								€ 21.17
Tim Van Hauwermeiren | 21.17 | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	26,667								26,667
Exercise price | €	€ 21.17								€ 21.17
Tim Van Hauwermeiren | 21.17 | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	26,666								26,666
Exercise price | €	€ 21.17								€ 21.17
Tim Van Hauwermeiren | 21.17 | Options to vest in 2020
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	26,667								26,667
Exercise price | €	€ 21.17								€ 21.17
Eric Castaldi | 2.44
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									230,607
Granted									43,200
Total options at end of year	273,807		230,607						273,807	230,607
Eric Castaldi | 2.44 | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	72,007								72,007
Exercise price | €	€ 2.44								€ 2.44
Eric Castaldi | 2.44 | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	9,000								9,000
Exercise price | €	€ 2.44								€ 2.44
Eric Castaldi | 7.17 | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	43,333								43,333
Exercise price | €	€ 7.17								€ 7.17
Eric Castaldi | 7.17 | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	21,667								21,667
Exercise price | €	€ 7.17								€ 7.17
Eric Castaldi | 9.47
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year										28,200
Total options at end of year						28,200					28,200
Exercise price | €						€ 9.47					€ 9.47
Eric Castaldi | 9.47 | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	9,400								9,400
Exercise price | €	€ 9.47								€ 9.47
Eric Castaldi | 9.47 | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	9,400								9,400
Exercise price | €	€ 9.47								€ 9.47
Eric Castaldi | 9.47 | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	9,400								9,400
Exercise price | €	€ 9.47								€ 9.47
Eric Castaldi | 11.47
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									28,200
Total options at end of year			28,200							28,200
Exercise price | €			€ 11.47							€ 11.47
Eric Castaldi | 11.47 | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	14,883								14,883
Exercise price | €	€ 11.47								€ 11.47
Eric Castaldi | 11.47 | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	9,400								9,400
Exercise price | €	€ 11.47								€ 11.47
Eric Castaldi | 11.47 | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,917								3,917
Exercise price | €	€ 11.47								€ 11.47
Eric Castaldi | 14.13
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									28,200
Total options at end of year			28,200							28,200
Exercise price | €			€ 14.13							€ 14.13
Eric Castaldi | 14.13 | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	9,400								9,400
Exercise price | €	€ 14.13								€ 14.13
Eric Castaldi | 14.13 | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	9,400								9,400
Exercise price | €	€ 14.13								€ 14.13
Eric Castaldi | 14.13 | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	9,400								9,400
Exercise price | €	€ 14.13								€ 14.13
Eric Castaldi | 21.17
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	43,200								43,200
Exercise price | €	€ 21.17								€ 21.17
Eric Castaldi | 21.17 | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	14,400								14,400
Exercise price | €	€ 21.17								€ 21.17
Eric Castaldi | 21.17 | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	14,400								14,400
Exercise price | €	€ 21.17								€ 21.17
Eric Castaldi | 21.17 | Options to vest in 2020
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	14,400								14,400
Exercise price | €	€ 21.17								€ 21.17

Other disclosures - Related p68

Other disclosures - Related party transactions - Executive directors ESOP - Remaining term (Details)	Dec. 31, 2017EquityInstrumentsY	Dec. 31, 2016EquityInstrumentsY	Dec. 31, 2015EquityInstrumentsY	Dec. 31, 2014EquityInstruments
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	2,862,216	2,293,636	1,752,926	1,595,015
Remaining term | Y		8.03	8.09
Tim Van Hauwermeiren | 7.0 years
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	105,000
Remaining term | Y	7
Tim Van Hauwermeiren | 8.0 years
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	30,600
Remaining term | Y	8
Tim Van Hauwermeiren | 8.5 years
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	50,000
Remaining term | Y	8.5
Tim Van Hauwermeiren | 9.0 years
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	30,600
Remaining term | Y	9
Tim Van Hauwermeiren | 10.0 years
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	80,000
Remaining term | Y	10
Eric Castaldi | 6.5 years
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	60,970
Remaining term | Y	6.5
Eric Castaldi | 7.0 years
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	85,037
Remaining term | Y	7
Eric Castaldi | 8.0 years
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	28,200
Remaining term | Y	8
Eric Castaldi | 8.5 years
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	28,200
Remaining term | Y	8.5
Eric Castaldi | 9.0 years
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	28,200
Remaining term | Y	9
Eric Castaldi | 10.0 years
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	43,200
Remaining term | Y	10

Other disclosures - Related p69

Other disclosures - Related party transactions - Remuneration of non-executive directors (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	€ 18,355	€ 4,654	€ 3,426
Non-executive Directors
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	320,000	223,930	143,268
Peter Verhaeghe
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	77,500	55,000	35,000
David L Lacey
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	50,000	45,930	45,651
Werner Lanthaler
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	55,000	45,000	35,000
Pamela Klein
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	42,500	35,000
Don Debethizy
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	52,500	€ 43,000	€ 27,617
A.A. Rosenberg
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	€ 42,500

Other disclosures - Related p70

Other disclosures - Related party transactions - Non-executive directors ESOP (Details)	12 Months Ended
	Dec. 31, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments	Dec. 31, 2015EUR (€)EquityInstruments	Jun. 30, 2017EUR (€)	Jun. 30, 2016EUR (€)	May 31, 2016EUR (€)	Sep. 30, 2015EUR (€)	Jun. 30, 2015EUR (€)	Dec. 31, 2014EquityInstruments
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options	2,862,216	2,293,636	1,752,926						1,595,015
Exercise price | €	€ 21.17	€ 14.130	€ 9.47	€ 18.41	€ 11.38	€ 11.47	€ 10.34	€ 11.44
Exercised	203,412	140,292	97,656
Non-executive Directors
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options	15,000	50,000	15,000
Exercised	0
11.38 | Peter Verhaeghe
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options		10,000
Term		10 years
Exercise price | €		€ 11.38
11.38 | David L Lacey
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options		10,000
Term		10 years
Exercise price | €		€ 11.38
11.38 | Werner Lanthaler
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options		10,000
Term		10 years
Exercise price | €		€ 11.38
11.38 | Pamela Klein
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options		10,000
Term		10 years
Exercise price | €		€ 11.38
11.38 | Don Debethizy
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options		10,000
Term		10 years
Exercise price | €		€ 11.38
14.13 | A.A. Rosenberg
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options	15,000	15,000
Term		10 years
Exercise price | €		€ 14.13
11.44 | Pamela Klein
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options	25,000	25,000
11.44 | Don Debethizy
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options	25,000	25,000	15,000
Term			10 years
Exercise price | €			€ 11.44
21.17 | David L Lacey
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options	15,000
Term	10 years
Exercise price | €	€ 21.17

Other disclosures - Related p71

Other disclosures - Related party transactions - Non-executive directors ESOP - Rollforward and vesting (Details)	1 Months Ended								12 Months Ended
	Dec. 31, 2017EUR (€)EquityInstruments	Jun. 30, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments	Jun. 30, 2016EUR (€)EquityInstruments	May 31, 2016EUR (€)EquityInstruments	Dec. 31, 2015EUR (€)EquityInstruments	Sep. 30, 2015EUR (€)EquityInstruments	Jun. 30, 2015EUR (€)EquityInstruments	Dec. 31, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments	Dec. 31, 2015EUR (€)EquityInstruments
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									2,293,636	1,752,926	1,595,015
Number of options granted	653,825	120,536	363,226	60,000	288,950	243,400	3,000	56,500	774,361	712,176	302,900
Exercised									203,412	140,292	97,656
Total options at end of year	2,862,216		2,293,636			1,752,926			2,862,216	2,293,636	1,752,926
Exercise price | €	€ 21.17	€ 18.41	€ 14.130	€ 11.38	€ 11.47	€ 9.47	€ 10.34	€ 11.44	€ 21.17	€ 14.130	€ 9.47
2.44 | Peter Verhaeghe
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									34,585
Total options at end of year	34,585		34,585						34,585	34,585
2.44 | Peter Verhaeghe | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	11,626								11,626
Exercise price | €	€ 2.44								€ 2.44
2.44 | David L Lacey
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									29,443
Number of options granted									15,000
Total options at end of year	44,443		29,443						44,443	29,443
2.44 | David L Lacey | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	6,643								6,643
Exercise price | €	€ 2.44								€ 2.44
2.44 | Werner Lanthaler
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									29,416
Total options at end of year	29,416		29,416						29,416	29,416
2.44 | Werner Lanthaler | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	12,814								12,814
Exercise price | €	€ 2.44								€ 2.44
2.44 | Werner Lanthaler | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	1,602								1,602
Exercise price | €	€ 2.44								€ 2.44
3.95 | Peter Verhaeghe | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	7,959								7,959
Exercise price | €	€ 3.95								€ 3.95
7.17 | Peter Verhaeghe | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333								3,333
Exercise price | €	€ 7.17								€ 7.17
7.17 | Peter Verhaeghe | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	1,667								1,667
Exercise price | €	€ 7.17								€ 7.17
7.17 | David L Lacey | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	8,533								8,533
Exercise price | €	€ 7.17								€ 7.17
7.17 | David L Lacey | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	4,267								4,267
Exercise price | €	€ 7.17								€ 7.17
7.17 | Werner Lanthaler | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333								3,333
Exercise price | €	€ 7.17								€ 7.17
7.17 | Werner Lanthaler | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	1,667								1,667
Exercise price | €	€ 7.17								€ 7.17
11.38 | Peter Verhaeghe
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									10,000
Total options at end of year			10,000							10,000
Exercise price | €			€ 11.38							€ 11.38
11.38 | Peter Verhaeghe | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	5,000								5,000
Exercise price | €	€ 11.38								€ 11.38
11.38 | Peter Verhaeghe | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333								3,333
Exercise price | €	€ 11.38								€ 11.38
11.38 | Peter Verhaeghe | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	1,667								1,667
Exercise price | €	€ 11.38								€ 11.38
11.38 | David L Lacey
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									10,000
Total options at end of year			10,000							10,000
Exercise price | €			€ 11.38							€ 11.38
11.38 | David L Lacey | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	5,000								5,000
Exercise price | €	€ 11.38								€ 11.38
11.38 | David L Lacey | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333								3,333
Exercise price | €	€ 11.38								€ 11.38
11.38 | David L Lacey | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	1,667								1,667
Exercise price | €	€ 11.38								€ 11.38
11.38 | Werner Lanthaler
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									10,000
Total options at end of year			10,000							10,000
Exercise price | €			€ 11.38							€ 11.38
11.38 | Werner Lanthaler | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	5,000								5,000
Exercise price | €	€ 11.38								€ 11.38
11.38 | Werner Lanthaler | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333								3,333
Exercise price | €	€ 11.38								€ 11.38
11.38 | Werner Lanthaler | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	1,667								1,667
Exercise price | €	€ 11.38								€ 11.38
11.38 | Pamela Klein
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									10,000
Total options at end of year			10,000							10,000
Exercise price | €			€ 11.38							€ 11.38
11.38 | Pamela Klein | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	5,000								5,000
Exercise price | €	€ 11.38								€ 11.38
11.38 | Pamela Klein | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333								3,333
Exercise price | €	€ 11.38								€ 11.38
11.38 | Pamela Klein | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	1,667								1,667
Exercise price | €	€ 11.38								€ 11.38
11.38 | Don Debethizy
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									10,000
Total options at end of year			10,000							10,000
Exercise price | €			€ 11.38							€ 11.38
11.38 | Don Debethizy | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	5,000								5,000
Exercise price | €	€ 11.38								€ 11.38
11.38 | Don Debethizy | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333								3,333
Exercise price | €	€ 11.38								€ 11.38
11.38 | Don Debethizy | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	1,667								1,667
Exercise price | €	€ 11.38								€ 11.38
21.17 | David L Lacey
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	15,000								15,000
Exercise price | €	€ 21.17								€ 21.17
21.17 | David L Lacey | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	5,000								5,000
Exercise price | €	€ 21.17								€ 21.17
21.17 | David L Lacey | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	5,000								5,000
Exercise price | €	€ 21.17								€ 21.17
21.17 | David L Lacey | Options to vest in 2020
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	5,000								5,000
Exercise price | €	€ 21.17								€ 21.17
11.44 | Pamela Klein
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									25,000
Total options at end of year	25,000		25,000						25,000	25,000
11.44 | Pamela Klein | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	7,500								7,500
Exercise price | €	€ 11.44								€ 11.44
11.44 | Pamela Klein | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	5,000								5,000
Exercise price | €	€ 11.44								€ 11.44
11.44 | Pamela Klein | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	2,500								2,500
Exercise price | €	€ 11.44								€ 11.44
11.44 | Don Debethizy
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									25,000	15,000
Total options at end of year	25,000		25,000			15,000			25,000	25,000	15,000
Exercise price | €						€ 11.44					€ 11.44
11.44 | Don Debethizy | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	7,500								7,500
Exercise price | €	€ 11.44								€ 11.44
11.44 | Don Debethizy | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	5,000								5,000
Exercise price | €	€ 11.44								€ 11.44
11.44 | Don Debethizy | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	2,500								2,500
Exercise price | €	€ 11.44								€ 11.44
14.13 | A.A. Rosenberg
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									15,000
Total options at end of year	15,000		15,000						15,000	15,000
Exercise price | €			€ 14.13							€ 14.13
14.13 | A.A. Rosenberg | Options vested until 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price | €	€ 14.13								€ 14.13
14.13 | A.A. Rosenberg | Options vested in 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	5,000								5,000
Exercise price | €	€ 14.13								€ 14.13
14.13 | A.A. Rosenberg | Options to vest in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	5,000								5,000
Exercise price | €	€ 14.13								€ 14.13
14.13 | A.A. Rosenberg | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	5,000								5,000
Exercise price | €	€ 14.13								€ 14.13

Other disclosures - Related p72

Other disclosures - Related party transactions - Non-executive directors ESOP - Remaining term (Details)	12 Months Ended
	Dec. 31, 2017EquityInstrumentsY	Dec. 31, 2016EquityInstrumentsY	Dec. 31, 2015EquityInstrumentsY	Dec. 31, 2014EquityInstruments
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	2,862,216	2,293,636	1,752,926	1,595,015
Remaining term | Y		8.03	8.09
Exercise of Options	203,412	140,292	97,656
Non-executive Directors
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	15,000	50,000	15,000
Exercise of Options	0
2.5 years | Peter Verhaeghe
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	3,650
Remaining term | Y	2.5
3.0 years | Peter Verhaeghe
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	2,340
Remaining term | Y	3
5.5 years | Peter Verhaeghe
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	5,560
Remaining term | Y	5.5
5.5 years | David L Lacey
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	3,180
Remaining term | Y	5.5
6.0 years | Peter Verhaeghe
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	3,181
Remaining term | Y	6
6.0 years | David L Lacey
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	1,818
Remaining term | Y	6
6.0 years | Werner Lanthaler
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	10,850
Remaining term | Y	6
7.0 years | Peter Verhaeghe
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	9,854
Remaining term | Y	7
7.0 years | David L Lacey
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	14,445
Remaining term | Y	7
7.0 years | Werner Lanthaler
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	8,566
Remaining term | Y	7
7.5 years | Don Debethizy
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	15,000
Remaining term | Y	7.5
7.5 years | Pamela Klein
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	15,000
Remaining term | Y	7.5
8.5 years | Peter Verhaeghe
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	10,000
Remaining term | Y	8.5
8.5 years | David L Lacey
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	10,000
Remaining term | Y	8.5
8.5 years | Werner Lanthaler
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	10,000
Remaining term | Y	8.5
8.5 years | Don Debethizy
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	10,000
Remaining term | Y	8.5
8.5 years | Pamela Klein
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	10,000
Remaining term | Y	8.5
9.0 years | A.A. Rosenberg
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	15,000
Remaining term | Y	9
10.0 years | David L Lacey
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	15,000
Remaining term | Y	10

Other disclosures - Commitments

Other disclosures - Commitments (Details) - EUR (€) € in Thousands	1 Months Ended
	Jul. 31, 2017	Dec. 31, 2017
Commitments [Line Items]
Contractual commitments for acquisition of property, plant and equipment		€ 0
Contractual commitments for acquisition of intangible assets		€ 0
ARGX110
Commitments [Line Items]
Contractual obligations	€ 900
Lonza Sales AG
Commitments [Line Items]
Contractual obligations	5,000
Payment of Contract Amount	1,000
Lonza Sales AG | ARGX-113
Commitments [Line Items]
Contractual obligations	€ 9,300

Other disclosures - Audit Fees

Other disclosures - Audit Fees (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other disclosures
Audit fees(1)	€ 205	€ 85	€ 70
Audit‑related fees	698	65	35
Tax and other services(2)		2	3
Total	€ 903	€ 152	€ 108

Other disclosures - Overview of

Other disclosures - Overview of Subsidiaries and Subsequent Events(Details) € in Millions	Mar. 16, 2018EUR (€)	Dec. 31, 2017subsidiary
Subsequent Event
Subsequent Events
VLAIO grant awarded | €	€ 2.5
Netherlands
Disclosure of subsidiaries [line items]
Participation ( as a percent)		100.00%
Belgium | ARGENX BVBA
Disclosure of subsidiaries [line items]
Number of subsidiaries		1
Participation ( as a percent)		100.00%
United States | ARGENX US INC
Disclosure of subsidiaries [line items]
Number of subsidiaries		1
Participation ( as a percent)		100.00%