argenx SE (ARGX) 20-F 26 Mar 19 2018 FY Annual report (foreign) Financial data

Document and Entity Information

Document and Entity Information	12 Months Ended
	Dec. 31, 2018shares
Document and Entity Information [Abstract]
Entity Registrant Name	ARGENX SE
Entity Central Index Key	0001697862
Document Type	20-F
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	35,975,312
Entity Emerging Growth Company	false
Entity Shell Company	false
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY

CONSOLIDATED STATEMENT OF FINAN

CONSOLIDATED STATEMENT OF FINANCIAL POSITION € in Thousands, $ in Thousands	Dec. 31, 2018EUR (€)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)
Current assets
Cash and cash equivalents	€ 281,040	€ 190,867	€ 89,897
Restricted cash — current	1,692	1,692	786
Research and development incentive receivables — current	301	158	163
Financial assets — current	283,529	168,907	6,831
Prepaid expenses	2,995	2,338	2,146
Trade and other receivables	2,886	2,842	1,970
Total current assets	572,443	366,804	101,793
Noncurrent assets
Restricted cash — non-current	251	256	1,149
Research and development incentive receivables — non-current	4,883	3,033	2,046
Other non-current assets		125
Financial assets — non-current	1	1	1
Property, plant and equipment	824	676	766
Intangible assets	56	13	17
Total non-current assets	6,015	4,104	3,979
TOTAL ASSETS	578,458	370,908	105,772
Equity
Share capital	3,597	3,217	2,012
Share premium	673,454	430,518	126,358
Accumulated losses	(169,603)	(100,568)	(72,492)
Other reserves	30,947	11,764	7,496
Total equity	538,395	344,931	63,374
Non-current liabilities	7	1,460	10,071
Provisions for employee benefits	7	25	1
Deferred revenue — non-current		1,435	10,070
Current liabilities	40,056	24,517	32,327
Trade and other payables	37,072	15,285	12,191
Tax liabilities	823	597
Deferred revenue - current	2,161	8,635	20,136
Total liabilities	40,063	25,977	42,398
TOTAL EQUITY AND LIABILITIES	€ 578,458	€ 370,908	€ 105,772

CONSOLIDATED STATEMENT OF PROFI

CONSOLIDATED STATEMENT OF PROFIT AND LOSS AND OTHER COMPREHENSIVE INCOME € in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018EUR (€)€ / sharesshares	Dec. 31, 2017EUR (€)€ / sharesshares	Dec. 31, 2016EUR (€)€ / sharesshares
CONSOLIDATED STATEMENT OF PROFIT AND LOSS AND OTHER COMPREHENSIVE INCOME
Revenue	€ 21,482	€ 36,415	€ 14,713
Other operating income	7,749	4,841	2,439
Total operating income	29,231	41,256	17,152
Research and development expenses	(83,609)	(51,740)	(31,557)
Selling, general and administrative expenses	(27,471)	(12,448)	(7,011)
Operating loss	(81,849)	(22,932)	(21,416)
Financial income	3,694	1,250	73
Exchange gains/(losses)	12,308	(5,797)	(31)
Loss before taxes	(65,847)	(27,479)	(21,374)
Income tax expense	(794)	(597)	0
Loss for the year and total comprehensive loss	€ (66,641)	€ (28,076)	€ (21,374)
Weighted average number of shares outstanding | shares	33,419,356	24,609,536	18,820,612
Basic and diluted loss per share | € / shares	€ (1.99)	€ (1.14)	€ (1.14)

CONSOLIDATED STATEMENT OF CASH

CONSOLIDATED STATEMENT OF CASH FLOWS € in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018EUR (€)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)
CASH FLOWS (USED IN) / FROM OPERATING ACTIVITIES
Operating result	€ (81,849)	€ (22,932)	€ (21,416)
Adjustments for non-cash items
Amortization of intangible assets	19	10	11
Depreciation of property, plant and equipment	474	425	323
Loss on disposal of fixed assets		11
Provisions for employee benefits	(18)	24	1
Expense recognized in respect of share-based payments	19,183	4,268	2,849
Adjustments for non-cash items	(62,191)	(18,195)	(18,232)
Movements in current assets/liabilities
(Increase)/decrease in trade and other receivables	(44)	(122)	(614)
(Increase)/decrease in other current assets	(800)	(1,093)	(2,641)
Increase/(decrease) in trade and other payables	21,784	3,094	7,648
Increase/(decrease) in current deferred revenue	(8,868)	(11,501)	7,545
Movements in non-current assets/liabilities
Increase)/decrease in other noncurrent assets	(1,720)	(94)	(1,627)
(Increase)/decrease in non-current deferred revenue	(1,435)	(8,635)	18,520
Cash flows (used in)/from operating activities	(53,274)	(36,546)	10,599
Income taxes paid	(565)
NET CASH FLOWS (USED IN) / FROM OPERATING ACTIVITIES	(53,839)	(36,546)	10,599
CASH FLOWS (USED IN) / FROM INVESTING ACTIVITIES
Purchase of intangible assets	(62)	(6)	(21)
Purchase of property, plant and equipment	(622)	(345)	(840)
(Increase)/decrease in current financial assets	(108,229)	(162,076)	(18)
Interest received	1,371	375	73
NET CASH FLOWS (USED IN) / FROM INVESTING ACTIVITIES	(107,542)	(162,052)	(806)
CASH FLOWS (USED IN) / FROM FINANCING ACTIVITIES
Proceeds from issue of new shares, gross amount	255,721	327,700	45,977
Issue costs paid	(14,655)	(23,015)	(1,849)
Exchange gain from currency conversion on proceeds from issue of new shares	1,354
Proceeds from exercise of stock options	2,251	679	493
NET CASH FLOWS (USED IN) / FROM FINANCING ACTIVITIES	244,671	305,365	44,621
NET INCREASE (DECREASE) IN CASH & CASH EQUIVALENTS	83,290	106,767	54,414
Cash and cash equivalents at the beginning of the period	190,867	89,897	35,514
Exchange gains/(losses) on cash & cash equivalents	6,883	(5,797)	(31)
Cash and cash equivalents at the end of the period	€ 281,040	€ 190,867	€ 89,897

CONSOLIDATED STATEMENT OF CHANG

CONSOLIDATED STATEMENT OF CHANGES IN EQUITY € in Thousands, $ in Thousands	Share capitalEUR (€)	Share premiumEUR (€)	Accumulated lossesEUR (€)	Other reservesEUR (€)	Total equity attributable to owners of the parentEUR (€)	EUR (€)	USD ($)
Equity at beginning 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)
Share-based payment				2,849	2,849	2,849
Issue of share capital (restated)	418	45,559			45,977	45,977
Transaction costs for equity issue (restated)		(1,849)			(1,849)	(1,849)
Exercise of stock options (restated)	14	479			493	493
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)
Share-based payment				4,268	4,268	4,268
Issue of share capital (restated)	1,185	326,515			327,700	327,700
Transaction costs for equity issue (restated)		(23,015)			(23,015)	(23,015)
Exercise of stock options (restated)	19	660			679	679
Equity at end of period at Dec. 31, 2017	3,216	430,518	(100,568)	11,764	344,931	344,931
Total comprehensive loss of the period			(66,641)		(66,641)	(66,641)	$ (66,641)
Share-based payment				19,183	19,183	19,183
Issue of share capital (restated)	347	255,374			255,721	255,721
Transaction costs for equity issue (restated)		(14,655)			(14,655)	(14,655)
Exercise of stock options (restated)	34	2,217			2,251	2,251
Equity at end of period at Dec. 31, 2018	€ 3,597	€ 673,454	(169,603)	€ 30,947	538,395	538,395
Adoption of IFRS 15 (modified retrospective approach)			€ (2,395)		€ (2,395)	€ (2,395)

General information about the c

General information about the company	12 Months Ended
	Dec. 31, 2018
General information about the company
General information about the company	1. General information about the company argenx SE 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 Company) 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, 2018
Significant accounting policies
Significant accounting policies	2. Significant accounting policies The significant Company’s 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 Company’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, 2018 and for the comparative information as of and for the years ended December 31, 2017 and 2016. 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 Company’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 significant accounting policies applied in the preparation of the above consolidated 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 March 26, 2019. Correction of an immaterial error Subsequent to the issuance of the Company’s consolidated financial statements for the year ended December 31, 2017 on Form 20-F, the Company determined that the current versus non-current classification of deferred revenue as of December 31, 2017 and December 31, 2016, respectively, was not made correctly, impacting the Company’s consolidated statement of financial position and the consolidated statement of cash flows. Management evaluated the materiality of the errors from a quantitative and qualitative perspective and concluded that this adjustment was not material to the Company’s previously issued consolidated financial statements. The Company has elected to revise the historical consolidated financial information presented herein in the consolidated statement of financial position and the consolidated statement of cash flows to reflect the correction of this error for the prior periods presented and to confirm to current year presentation. Since the revisions were not material, no amendments to previously filed reports were required. The revision had the effect of decreasing the current deferred revenue balance and increasing the non-current deferred revenue with €1.4 million as of December 31, 2017 and €10.1 million as of December 31, 2016, respectively. Each affected individual line item within the consolidated statement of cash flows relating to the change in these balances have likewise been revised. Reclassifications Certain amounts from previous periods have been reclassified to conform to the 2018 presentation. Specifically, for the years ended December 31, 2017 and December 31, 2016, issue costs paid and proceeds from exercise of stock options are now disclosed on as a separate line item on the consolidated statement of cash flows and on the consolidated statement of changes in equity. 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 the subsidiary. 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 consolidated financial statements are presented in euro (€), which is the Company’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 Leases of property, plant and equipment where the Company, as lessee, has substantially all the risks and rewards of ownership are classified as finance leases. Finance leases are capitalised at the lease’s inception at the fair value of the leased property or, if lower, the present value of the minimum lease payments. The corresponding rental obligations, net of finance charges, are included in other short-term and long-term payables. Each lease payment is allocated between the liability and finance cost. The finance cost is charged to the profit or loss over the lease period so as to produce a constant periodic rate of interest on the remaining balance of the liability for each period. The property, plant and equipment acquired under finance leases is depreciated over the asset’s useful life or over the shorter of the asset’s useful life and the lease term if there is no reasonable certainty that the Company will obtain ownership at the end of the lease term. 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. 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 instruments Financial assets and financial liabilities are recognised in the Company’s statement of financial position when the Company becomes a party to the contractual provisions of the instrument. Financial assets and financial liabilities are initially measured at fair value. Transaction costs that are directly attributable to the acquisition or issue of financial assets and financial liabilities (other than financial assets and financial liabilities at fair value through profit or loss) are added to or deducted from the fair value of the financial assets or financial liabilities, as appropriate, on initial recognition. Transaction costs directly attributable to the acquisition of financial assets or financial liabilities at fair value through profit or loss are recognised immediately in profit or loss. The Company has adopted IFRS 9 on January 1, 2018. In accordance with the transitional provisions in IFRS 9, comparative figures have not been restated. The adoption of IFRS 9 had no material impact on the consolidated financial statements (see also note 6.1). 2.8.1 Investment securities (i) Classification From January 1, 2018, the Company classifies its financial assets at fair value through profit and loss (FVTPL). For assets measured at fair value, gains and losses will either be recorded in profit or loss. For investments in equity instruments that are not held for trading, this will depend on whether the Company has made an irrevocable election at the time of initial recognition to account for the equity investment at fair value through other comprehensive income (FVOCI). (ii) Recognition and derecognition Purchases and sales of financial assets are recognised on trade-date, the date on which the Company commits to purchase or sell the asset. Financial assets are derecognised when the rights to receive cash flows from the financial assets have expired or have been transferred and the Company has transferred substantially all the risks and rewards of ownership. (iii) Measurement At initial recognition, the Company measures a financial asset at its fair value. Transaction costs of financial assets carried at FVTPL are expensed in profit or loss. (iv) Impairment From January 1, 2018, the Company assesses on a forward-looking basis the expected credit losses associated with its debt instruments carried at amortised cost and FVOCI. The impairment methodology applied depends on whether there has been a significant increase in credit risk. (v) Accounting policies applied until December 31, 2017 Financial assets were 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 depended on the nature and purpose of the financial assets and was determined at the time of initial recognition. Management determined the classification at the time of the purchase and reevaluated such designation at each subsequent balance sheet date. Purchase and sale of financial assets were recognized on the settlement date, which was the date an asset is delivered to or by the Group. The cost of financial assets included transaction costs. The carrying amounts of all financial assets were reviewed for impairment whenever events or changes in circumstances indicated that the carrying amount is impaired. If objective evidence existed that a financial asset or group of financial assets was impaired, the amount of the impairment loss was 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 was immediately recognized in net finance costs. An impairment loss on financial assets was reversed if, in a subsequent period, the amount of the impairment loss decreased and this decrease could be related objectively to an event occurring after the impairment loss was recognized. Such reversal was immediately recognized in net finance costs. 2.9 Trade and other receivables Trade receivables are recognised initially at the amount of consideration that is unconditional. The Company holds the trade receivables with the objective to collect the contractual cash flows and therefore measures them subsequently at amortised cost using the effective interest method. Unless the impact of discounting is material, the nominal value is recognized. The Company measures the loss allowance for trade receivables at an amount equal to lifetime expected credit loss. The expected credit losses are 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 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. 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. The Company has never distributed any dividends to its shareholders. As of 31 December 2018, no profits were available for distribution. 2.13 Trade and other 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 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. 2.15 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, which are included in Research and development expenses and in Selling, general and administrative 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. 2.16 Short‑term employee benefits Short‑term employee benefits include payables and accruals for salaries and bonuses to be paid to the employees of the Company. They are recognized as expenses for the period in which employees perform the corresponding services. 2.17 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 4.9. 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 Company’s estimate of equity instruments that will eventually vest, with a corresponding increase in equity. At the end of each reporting period, the Company 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. 2.18 Deferred revenue Current and non-current 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. IFRS 15 uses the term ‘contract liability’ to describe what might more commonly be known as ‘deferred revenue’, however IFRS 15 does not prohibit an entity from using alternative descriptions in the statement of financial position. The Company will continue to report its contract liabilities under the term ‘deferred revenue. 2.19 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 consolidated 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. 2.20 Revenue and other operating income recognition Collaborations The Company generates revenue from collaborations and strategic alliances. The Company applies 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. Identify the contracts In our current arrangements, the Company 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 The Company has assessed that there is one single performance obligation for certain arrangements in our material ongoing license and collaboration arrangements, 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 Company 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 Company’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 s

Critical accounting judgements

Critical accounting judgements and key sources of estimation uncertainty	12 Months Ended
	Dec. 31, 2018
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. Critical judgements in applying accounting policies Revenue recognition Revenue from certain arrangements is recognized as the Company satisfies a single performance obligation. The Company recognizes upfront payments and milestone payments, allocated to a single performance obligation over the estimated service period based on a pattern that reflects the transfer of the services. The revenue recognized would reflect the level of service during each period. In this case, the Company would use an input model that considers estimates of the percentage of total research and development service costs that are completed each period compared to the total estimated service costs (percentage of completion method). Research and development service fees are recognized as revenue when costs are incurred and agreed by the parties as the Company is acting as a principal in the scope of its stake in the research and development activities of its ongoing license and collaboration agreements. Research and development cost accruals Research and development costs are charged to expense as incurred and are typically made up of payroll costs, clinical and preclinical activities, drug development and manufacturing costs, including costs for clinical research organizations and investigative sites. Costs for certain development activities, such as clinical trials, are recognized based on an evaluation of the progress to completion of specific tasks using data such as information provided by vendors on their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the financial statements as prepaid expenses. Critical accounting estimates Going concern The Company has incurred net losses since its inception and for the year ended December 31, 2018, 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 March 26, 2019, the Board has reviewed and approved the consolidated financial statements and accounting policies. Taking into account the cash and cash equivalents and current financial asset position of €564.6 million on December 31, 2018, the Board is of the opinion that the Company can submit its consolidated financial statements on a going concern basis. Whilst the current cash position is sufficient for the Company’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. 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 4.9. 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 Company has reported losses, and consequently, the Company 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, 2018.

Notes relating to the consolida

Notes relating to the consolidated statement of financial position	12 Months Ended
	Dec. 31, 2018
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, 2016 Cost € 72 Accumulated amortization (65) Book value at the beginning of the year 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 Movements Additions 62 Cost of disposals (2) Amortization (19) Accumulated depreciation on disposals 2 Balance as on December 31, 2018 Cost 159 Accumulated amortization (103) Book value at year end € 56 The intangible assets correspond to software. As of December 31, 2018, 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 Lease (in thousands of €) IT equipment equipment equipment Total Opening balance as on January 1, 2016 Cost € 93 € 1,179 € € 1,272 Accumulated depreciation (66) (957) (1,023) Book value at the beginning of the year 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 Movements Additions 111 259 253 623 Cost of disposals (12) (34) (46) Depreciation (64) (399) (11) (474) Accumulated depreciation on disposals 12 34 46 Closing balance as on December 31, 2018 Cost 331 2,381 253 2,965 Accumulated depreciation (209) (1,921) (11) (2,141) Book value at year end € 122 € 460 € 242 € 824 There are no commitments to acquire property, plant and equipment. Furthermore, no items of property, plant and equipment are pledged. 4.3 Research and development incentive receivables Year Ended December 31, (in thousands of €) 2018 2017 2016 Research and development incentive receivables—current € 301 € 158 € 163 Research and development incentive receivables—non-current 4,883 3,033 2,046 € 5,184 € 3,191 € 2,209 On December 31, 2018, the Company has recorded a tax receivable of €5.2 million, compared to €3.2 million on December 31, 2017, in relation to 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 2019 onwards. 4.4 Restricted cash Year Ended December 31, (in thousands of €) 2018 2017 2016 Non ‑ current restricted cash Rental guarantees € 251 € 256 € 244 Escrow account > 1 year — — 905 Total non ‑ current € 251 € 256 € 1,149 Current restricted cash Escrow account < 1 year 1,692 1,692 786 Total restricted cash € 1,943 € 1,948 € 1,935 On December 31, 2018, the Company 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 €0.3 million 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 €1.7 million 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 Company or to the third party under certain conditions after the completion of the work plan of the related collaboration agreement with AbbVie. 4.5 Trade and other receivables The trade and other receivables are composed of receivables which are detailed below: Year Ended December 31, (in thousands of €) 2018 2017 2016 VAT receivable € 496 € 317 € 278 Trade receivables 214 845 1,118 Other receivables 455 750 — Interest receivable 556 — 6 VLAIO grant receivable 1,165 930 568 € 2,886 € 2,842 € 1,970 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 2019. Trade receivables correspond to amounts invoiced to the collaborators or strategic allies of the Company. No bad debt allowance was recorded nor were any trade receivables impaired on December 31, 2018 and December 31, 2017. 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. 4.6 Current financial assets On December 31, 2018, the current financial assets amounted to €283.5 million compared to €168.9 million on December 31, 2017. 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, with changes in fair value going through profit and loss. Please also refer to note 6.1 for more information on the financial instruments. 4.7 Cash and cash equivalents Year Ended December 31, (in thousands of €) 2018 2017 2016 Cash equivalents € 217,626 € 25,000 € 54,500 Cash and bank balances 63,414 165,867 35,397 € 281,040 € 190,867 € 89,897 On December 31, 2018, cash and cash equivalents amounted to €281.0 million compared to €190.9 million on December 31, 2017 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. Policies are in place that limit the amount of credit exposure to any one financial institution (see also note 6.4). 4.8 Shareholders’ capital Roll forward of number of shares outstanding: Number of shares outstanding on January 1, 2016 15,802,767 Private placement (Federated Investment) on January 20, 2016 1,480,420 Exercise of options in February 2016 2,200 Exercise of options in March 2016 10,000 Exercise of options in Apil 2016 10,000 Exercise of options in May 2016 33,092 Private placement (Sunflower) on June 1, 2016 2,703,000 Exercise of options in September 2016 70,000 Exercise of options in October 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 in August 2017 5,000 Exercise of options in September 2017 15,000 Exercise of options in October 2017 1,400 Exercise of options in November 2017 106,782 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 in December 2017 75,230 Number of shares outstanding on December 31,2017 32,180,641 Exercise of options in January 2018 111,727 Exercise of options in March 2018 113,075 Exercise of options in April 2018 34,039 Exercise of options in May 2018 5,900 Exercise of options in June 2018 5,393 Exercise of options in July 2018 469 Exercise of options in August 2018 2,300 Exercise of options in September 2018 5,913 U.S. third public offering on Nasdaq on September 18, 2018 3,475,000 Exercise of options in October 2018 556 Exercise of options in November 2018 9,768 Exercise of options in December 2018 30,531 Number of shares outstanding on December 31,2018 35,975,312 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. New shares issued during 2018 On September 18, 2018, argenx SE offered 3,475,000 of its ordinary shares through a public offering in the United States in the form of ADSs at a price to the public of $86.50 per ADS, before underwriting discounts and commissions and offering expenses. As a result, argenx SE received €255.7 million of gross proceeds from this offering, decreased by €14.8 million of underwriter discounts and commissions, and offering expenses, of which €14.7 million has been deducted from equity. The total net cash proceeds from the offering amounted to €240.9 million. As a result of the exercise of options under the argenx Employee Stock Option Plan, 319,671 new shares were created in 2018. This resulted in a total of 35,975,312 ordinary shares, with a nominal value of €0.1 per share, on December 31, 2018. The annual general meeting of the Company on May 8, 2018 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 €648,790 represented by 6,487,896 shares. The board of directors has issued 3,475,000 shares on the occasion of the follow-on U.S. public offering in September 2018, and as of December 31, 2018, the existing authorization covered the issuance of up to 3,012,896 shares. 4.9 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 Company has granted on June 28, 2018 a total of 178,900 stock options and on December 21, 2018 a total of 861,575 stock options to its employees, Board members and consultants. The total number of stock options outstanding on December 31, 2018 totaled 3,536,651 compared to 2,862,216 on December 31, 2017 and 2,293,636 on December 31, 2016. No stock options were expired in the years ended December 31, 2018, 2017 and 2016. 319,671 stock options have been exercised in the year ended December 31, 2018 compared to 203,412 in the year ended December 31, 2017 and 140,292 in the year ended December 31, 2016. A total of 46,369 stock options have been forfeited in the year ended December 31, 2018 compared to 2,369 in the year ended December 31, 2017 and 31,174 in the year ended December 31, 2016. 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 €) 2018 2017 2016 2020 € 3.95 18,200 36,960 112,738 2021 3.95 — 2,850 3,800 2023 2.44 294,400 314,593 360,787 2024 2.44 117,733 135,890 169,926 2024 3.95 6,895 15,692 55,746 2024 7.17 407,061 516,100 522,500 2024 2.44 26,970 83,820 83,820 2025 11.44 39,000 39,000 39,000 2025 10.34 3,000 3,000 3,000 2025 9.47 226,323 235,514 235,733 2026 11.38 50,415 60,000 60,000 2026 11.47 257,616 282,310 283,360 2026 14.13 315,102 362,126 363,226 2027 18.41 114,019 120,536 — 2027 21.17 628,292 653,825 — 2023 80.82 94,600 — — 2028 80.82 75,450 — — 2023/2028 (1) € 86.32 861,575 — — 3,536,651 2,862,216 2,293,636 (1) On December 21, 2018, the Company granted options for which the beneficiaries had a 60-day period to choose between a contractual term of five or ten years. 2018 2017 2016 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 2,862,216 € 11.54 2,293,636 € 7.72 1,752,926 € 5.37 Granted 1,040,475 85.37 774,361 20.74 712,176 12.82 Exercised (319,671) 7.02 (203,412) 3.46 (140,292) 3.52 Forfeited (46,369) 30.44 (2,369) 12.52 (31,174) 10.90 Outstanding at December 31, 3,536,651 33.42 2,862,216 11.54 2,293,636 7.72 Exercisable at December 31, 1,859,315 € 9.62 1,598,829 € 6.80 1,257,091 € 4.68 The weighted average remaining contractual life of the stock options outstanding amounted to 7.82 years on December 31, 2018 compared to 8.03 years on December 31, 2017 and 8.09 years on December 31, 2016. 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 31,2018 (in years) 2.44-3.95 464,198 4.83 7.17-9.47 633,384 6.32 10.34-14.13 665,133 7.61 18.41-21.17 742,311 8.88 80.82-86.32 1,031,625 9.44 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 Company since its initial public offering. Below is an overview of the parameters used in relation to the grants during 2018: Stock options granted in June 2018 Dec 2018 Number of options granted 178,900 861,575 Average fair value of options (in EUR) € 32.12 € 44.49 Share price (in EUR) € 72.00 € 82.20 Exercise price (in EUR) € 80.82 € 86.32 Expected volatility 45.5 % 46.2 % Average expected option life (in years) (1) 7.36 10 Risk ‑ free interest rate 0.72 % 0.77 % Expected dividends — % — % (1) On December 21, 2018, the Company granted a total of 861,575 stock options. The beneficiary can choose between a contractual term of five or ten years. The average expected option life is currently estimated at ten years. This estimate will be reassessed once the acceptance period of 60 days has passed and the beneficiaries will have made a choice between a contractual term of five or ten years. The total fair value of the grant would range from €27.7 million (100% of the stock options at an expected option life of five years) to €38.3 million (100% of the stock options at an expected option life of ten years). 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 in an overview of the parameter 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 — % — % — % The total share-based payment expense recognized in the consolidated statement of comprehensive income totaled €19.2 million for the year ended December 31, 2018, compared to €4.3 million for the year ended December 31, 2017 and €2.3 million for the year ended December 31, 2016. 4.10 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, 2016, a net liability of €1 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, 2017 and 2018, a net defined benefit obligation of respectively €25 thousand and €7 thousand was recorded. The amounts recognized in the balance sheet are as follows: (in thousands of €) 2018 2017 2016 Defined benefit obligation € 1,277 € 1,007 € 670 Fair value of plan assets 1,270 982 669 Deficit / surplus (−) of funded obligations 7 25 1 Net liability (asset) € 7 € 25 € 1 The movement in the defined benefit obligation, plan assets, net liability and asset over the year is as follows: (in thousands of €) 2018 2017 2016 Defined benefit obligation at January 1 € 1,007 € 670 € 486 Service cost 336 352 113 Interest expense 15 11 6 Contributions by plan participants (116) (148) (64) Actuarial gains (-) / losses (+) 35 124 131 Benefits paid / transfers out — (2) (2) Defined benefit obligation at December 31 € 1,277 € 1,007 € 670 (in thousands of €) 2018 2017 2016 Fair value of plan assets at January 1 € 982 € 669 € 486 Interest income 16 10 7 Administrative costs & taxes (32) (46) (19) Contributions by company & participants 328 423 176 Contributions by plan participants (116) (148) (64) Actuarial gains (+) / losses (-) 92 76 85 Benefits paid / transfers out — (2) (2) Fair value of plan assets at December 31 € 1,270 € 982 € 669 In the income statement, current service cost and interest expense or income are included in the operating loss. The Company’s estimated employer contributions for 2018 amount to €0.2 million compared to €0.3 million in 2017 and €0.1 million in 2016. Plan assets on December 31, 2018, 2017 and 2016 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 2018 2017 2016 Discount rate 1.3 % 1.3 % 1.3 % The weighted average duration of the benefit obligations equals 18 years. Sensitivity analyses show the following effects: Sensitivity analysis Change in Impact on defined ‑ (in thousands of €) assumption benefit obligation % Discount rate -1.00 % Increase by 198.1 15.51 % Discount rate 1.00 % Decrease by 57.1 (4.47) % The above analyses were done on a mutually exclusive basis, and holding all other assumptions constant. Through its defined benefit plan, the Company 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 43.8 years on December 31, 2018, compared to 46 years on December 31, 2017 and 48 years on December 31, 2016. 4.11 Trade and other payables Year Ended December 31, (in thousands of €) 2018 2017 2016 Trade payables € 6,007 € 4,395 € 4,385 Accruals for invoices to be received 18,145 4,046 5,444 Short‑term employee benefits 12,920 6,844 2,362 € 37,072 € 15,285 € 12,191 Trade payables correspond primarily to clinical and manufacturing activities. The fair value of trade payables approximates their carrying amount. The accruals for invoices to be received amount to €18.1 million for the year ended December 31, 2018 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. Short‑term employee benefits include payables and accruals for salaries and bonuses to be paid to the employees of the Company. 4.12 Current tax liability The current tax liability amounts to €0.8 million for the year ended December 31, 2018 and corresponds primarily to the tax payable on the result of argenx SE and on the result of argenx US, Inc. in view of the transfer price agreements set up between argenx BVBA and argenx US, Inc. As part of its business restructuring, the Company 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. There is 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 Company 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. 4.13 Deferred revenue Deferred revenue relates to cash received from collaboration and strategic alliances prior to completion of the earnings process. On December 31, 2018, current and non-current deferred revenue amounted to €2.2 million compared to €10.1 million at the same date in 2017, and included €2.0 million related to the upfront and milestone payments received from AbbVie in 2018, 2017 and 2016, and €0.2 million related to the upfront and milestone payments received from LEO Pharma in 2018, 2017 and 2016. 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.

Notes to consolidated statement

Notes to consolidated statement of profit and loss and other comprehensive income	12 Months Ended
	Dec. 31, 2018
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 €) 2018 2017 2016 Upfront payments € 8,635 € 20,137 € 9,103 Milestone payments 11,440 9,677 500 Research and development service fees (FTE) 1,407 6,601 5,110 € 21,482 € 36,415 € 14,713 For the years ended December 31, 2018 and 2017, the majority of the revenue was generated under the agreements with 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, 2018 corresponded principally to the partial recognition in revenue over the year of the upfront payment received following the signatures of a collaboration agreement with AbbVie in April 2016 and with LEO Pharma in May 2015. The milestone payments of €11.4 million recognized in the year ended December 31, 2018 mainly related to milestone payments received under the AbbVie and LEO Pharma collaborations. The upfront and milestone payments are recognized as revenue over the estimated period of the Company’s continuing involvement in the research and development activities provided for under the terms of these agreements. The research and development service fees (FTE) for the year ended December 31, 2018 corresponded to FTE payments received under the collaboration agreements of €0.5 million from Shire, €0.5 million from Staten Biotechnology B.V. (Staten) and €0.4 million from LEO Pharma. We adopted IFRS 15 - Revenue from contracts with customers on January 1, 2018 using the modified retrospective approach. For more information on the impact of adopting IFRS 15, see note 2.22. In our current arrangements, the Company is licensing certain of its intellectual property to collaborative entities and conducts research and development activities. Such activities result in a service that is the output of the Company’s ordinary activities. The Company generates revenue through a number of these arrangements, which include license fees, milestone payments, reimbursement income and future sales-based milestones and sales-based royalties. The Company assessed that the revenues from the current material licensing and collaboration agreements are in the scope of IFRS 15. With regard to its collaboration with AbbVie and LEO Pharma, the Company concluded as follows: · There is one single performance obligation under the new standard of IFRS 15, that being the transfer of a license combined with performance of research and development activities. The Company concluded that the license is not distinct in the context of the contract. · The transaction price of these two agreements is currently composed of a fixed part, that being an upfront license fee, and a variable part, that being milestone payments and cost reimbursements of research and development activities delivered. Milestone payments are included in the transaction price of the arrangement only when achieved. Sales-based milestones and sales-based royalties are a part of the Company’s arrangements but are not yet included in its revenues, as its programs with AbbVie and LEO Pharma are still in the development phase. · The transaction price has been allocated to the single performance obligation, and revenues have been recognized over the estimated service period based on a pattern that reflects the transfer of the license and progress to complete satisfaction of the research and development activities. This is because the transfer of the license is considered to be combined with the performance of research and development activities. Therefore, research and development milestone payments are variable considerations that are entirely allocated to the single performance obligation. · The Company has chosen an input model to measure the satisfaction of the single performance obligation that considers percentage of costs incurred for these programs (percentage of completion method). · Cost reimbursements received could be recognized in revenues when costs are incurred and agreed by the parties, as the Company is acting as a principal in the scope of its stake of the research and development activities of its ongoing license and collaboration agreements. For the year ended December 31, 2018, €10.5 million of milestone revenue associated with the AbbVie collaboration agreement was recognized, of which (i) €8.3 million is related with the recognition of a preclinical milestone obtained in 2018 and (ii) €2.2 million is related with deferred revenue that was already recognized in previous periods under the former IAS 18 standard. For the year ended December 31, 2018, €0.6 million of milestone revenue associated with the LEO Pharma collaboration agreement was recognized, of which (i) €0.5 million is related with the recognition of a preclinical milestone obtained in 2018 and (ii) €0.1 million is related with deferred revenue that was already recognized in previous periods under the former IAS 18 standard. Below are summaries of the key collaborations. AbbVie In April 2016, the Company entered into a collaboration agreement with AbbVie S.À.R.L. (AbbVie) to develop and commercialize ARGX-115 (ABBV-151). Under the terms of the collaboration agreement, the Company was responsible for conducting and funding all ARGX‑115 (ABBV-151) research and development activities up to completion of IND enabling studies. The Company 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 (ABBV-151) program to develop and commercialize products. The Company received an upfront, nonrefundable, 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 (ABBV-151), and we achieved two preclinical milestones, each of which triggered a $10.0 million payment (€8.9 million based on the exchange rate in effect as of the date the first milestone payment was received, and €8.7 million based on the exchange rate in effect as of the date the second milestone payment was received). In August 2018, AbbVie exercised its option and has now assumed certain development obligations, being solely responsible for all research, development and regulatory costs relating to ARGX-115 based products. Subject to the continuing progress of ARGX-115 (ABBV-151) by AbbVie, the Company is eligible to receive 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 Company has the right, on a product‑by‑product basis to co‑promote ARGX‑115 (ABBV-151) based products in the European Economic Area and Switzerland and to combine the product with the Company’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. AbbVie will fund further GARP‑related research by the Company for an initial period of two years. AbbVie will have the right to license additional therapeutic programs emerging from this research, for which the Company could receive associated milestone and royalty payments. Leo Pharma In May 2015 the Company 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 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. The Company received pre‑IND payments of €4.5 million, including an upfront payment. The companies co‑funded product development costs up to clinical trial application (CTA) filing, which was obtained in April 2018. The Company 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. 5.2 Other operating income Year Ended December 31, (in thousands of €) 2018 2017 2016 Grants € 1,842 € 422 € 779 Research and development incentives 2,151 983 641 Payroll tax rebates 3,756 3,436 1,019 € 7,749 € 4,841 € 2,439 Grants The Flanders Innovation and Entrepreneurship Agency provided the Company with several grants. On December 31, 2018, the situation of the grants received by the Company reflected the expenses incurred by the Company in the various research and development projects sponsored by Flanders Innovation and Entrepreneurship Agency. On December 31, 2018, the Company had two ongoing grant research projects: (Amounts presented in thousands of €) Flanders Innovation & Entrepreneurship - VLAIO 1 Grantor: Flanders Innovation & Entrepreneurship Agency Start date: 11/01/2017 End date: 31/10/2020 Amount granted and approved: € 2,527 Amount recognized: 982 Flanders Innovation & Entrepreneurship - VLAIO 2 Grantor: Flanders Innovation & Entrepreneurship Agency Start date: 01/05/2018 End date: 31/10/2020 Amount granted and approved: € 2,634 Amount recognized: 740 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 consolidated financial statements, except for those described in note 7.2 of this report. Other Incentives Research and development incentives The Company has accounted for a tax receivable of €2.2 million in the year ended December 31, 2018, compared to €1.0 million in the year ended December 31, 2017, 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 4.3). Payroll tax rebates The Company accounted for €3.8 million payroll tax rebates in the year ended December 31, 2018, compared to €3.4 million in the year ended December 31, 2017, as a reduction in withholding income taxes for its highly‑qualified personnel employed in its research and development department. 5.3 Segment reporting The Company 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. Revenue from external customers Year ended December 31, (in thousands of €) 2018 2017 2016 Netherlands € 470 € 628 € 548 Germany — — 311 Denmark 1,136 6,240 3,066 Switzerland 912 2,486 3,315 United States — 1 47 Luxembourg 18,964 27,060 7,426 Total € 21,482 € 36,415 € 14,713 Information about major clients: The Company received €21.5 million of revenue from its external customers in the year ended December 31, 2018 compared to €36.4 million over the same period in 2017, of which €19.0 million came from the Company’s largest client, €1.1 million from its second largest client and €0.9 million from its third largest client, compared to respectively €27.1 million, €6.2 million and €2.5 million in the year ended December 31, 2017. For a detailed description of our key collaborations, see note 5.1. 5.4 Research and development expenses Year Ended December 31, (in thousands of €) 2018 2017 2016 Personnel expense € 26,519 € 16,473 € 9,844 External research and development expenses 48,859 27,893 17,562 Materials and consumables 1,464 1,562 1,180 Depreciation and amortization 494 446 335 Other expenses 6,273 5,366 2,636 € 83,609 € 51,740 € 31,557 5.5 Selling, general and administrative expenses Year Ended December 31, (in thousands of €) 2018 2017 2016 Personnel expense € 18,292 € 6,745 € 3,256 Consulting fees 5,472 3,289 2,563 Supervisory board 1,088 621 446 Office costs 2,619 1,793 746 € 27,471 € 12,448 € 7,011 5.6 Personnel expenses The personnel expenses which exclude consultants mentioned above are as follows: Year Ended December 31, (in thousands of €) 2018 2017 2016 Short ‑ term employee benefits—Salaries € 18,617 € 12,149 € 8,527 Short ‑ term employee benefits—Social Security 2,213 1,504 1,027 Post ‑ employment benefits 441 291 175 Termination benefits 96 8 86 Share ‑ based payment 18,527 3,985 2,849 Employer social security contributions stock options 4,918 5,281 436 € 44,812 € 23,218 € 13,100 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 2018 2017 2016 Research and development 74.4 56.8 46.9 Selling, general and administrative 29.5 14.7 9.9 103.9 71.5 56.8 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 €1.5 million for the year ended December 31, 2018 (of which €1.1 million is presented as research and development expenses and €0.4 million is included under selling, general and administrative expenses) versus €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). The Company’s future operating lease commitments are as follows: Year Ended December 31, Operating lease commitments (in thousands of €) 2018 2017 2016 Less than 1 year € 1,028 € 1,028 € 915 1–3 years 1,766 465 1,159 3–5 years 210 33 24 More than 5 years — — — € 3,004 € 1,526 € 2,098 The Company has a lease plan for the Company’s cars with maturity dates up to four years. For the laboratory and office space, the Company 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 (see also note 7.6). 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 €) 2018 2017 2016 Interest income on bank deposits € 1,371 € 165 € 61 Net gains on current financial assets at FVTPL 2,323 210 12 Realized gain on non-current financial assets — 875 — Financial income 3,694 1,250 73 Realized exchange gains/(losses) 1,355 — — Unrealized exchange gains/(losses) 10,953 (5,797) (31) Exchange gains/(losses) 12,308 (5,797) (31) The exchange gains of €12.3 million for the year ended December 31, 2018 were primarily attributable to unrealized exchange rate gains on our cash and cash equivalents and current financial assets position in USD due to the favorable 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 €) 2018 2017 2016 Loss before taxes (65,847) (27,479) (21,374) Income tax calculated at 25% 16,462 6,870 5,344 Effect of expenses and gains that are not deductible in determining taxable results (3,934) (1,141) (755) Effect of stock issue expenses that are not deductible in determining taxable results 3,716 5,754 462 Effect of concessions (R&D incentives and grants) 430 453 463 Effect of tax losses carried forward not recognized (Netherlands) — — (5,551) Effect of usage of tax losses carried forward not previously recognized (Netherlands) — 19,378 — Effect of tax losses carried forward not recognized (Belgium) (5,511) (27,413) — 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 (15) (517) (180) Deferred tax asset other than loss carryforwards not recognized (11,968) (4,363) — Other 26 9 22 Income tax expense recognized in the consolidated statement of profit and loss € (794) € (597) € 0 The tax rate used for the 2018, 2017 and 2016 reconciliations above is the corporate income tax rate of 25% payable by corporate entities in the Netherlands. The unrecognized deferred tax asset on deductible temporary differences and unused tax losses amounts to €29.3 million on December 31, 2018, compared to €28.4 million on December 31, 2017. Deferred tax have been measured using the effective rate that will apply in Belgium (25%). The Company has unused tax loss carried forwards for an amount of €117.1 million on December 31, 2018. This, combined with other temporary differences, resulted in a net deferred tax asset position. Due to the uncertainty surrounding the Company’s ability to realize taxable profits in the near future, the Company did not recognize any deferred tax assets. As part of its business restructuring, the Company 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. There is 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 Company cannot guarantee 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 (see note 4.12). 5.10 Loss per share Year Ended December 31, (in thousands of €) 2018 2017 2016 Loss of the year € (66,641) € (28,076) € (21,374) Weighted average number of shares outstanding 33,419,356 24,609,536 18,820,612 Basic and diluted loss per share (in €) € (1.99) € (1.14) € (1.14) 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 Company 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, 2018
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 The Company adopted IFRS 9 on January 1, 2018. On the date of initial application, the financial instruments of the Company were as follows: Measurement category Carrying amount Original New Original New (in thousands of €) IAS 39 IFRS 9 IAS 39 IFRS 9 Financial assets — non-current Available for sale FVTPL € 1 € 1 Research and development incentive receivables — non-current Amortised cost Amortised cost 3,033 3,033 Restricted cash — non-current Amortised cost Amortised cost 256 256 Trade and other receivables Amortised cost Amortised cost 2,842 2,842 Prepaid expenses Amortised cost Amortised cost 2,338 2,338 Financial assets—current FVTPL FVTPL 168,907 168,907 Research and development incentive receivables — current Amortised cost Amortised cost 158 158 Restricted cash — current Amortised cost Amortised cost 1,692 1,692 Cash and cash equivalents Amortised cost Amortised cost 190,867 190,867 Trade and other payables Amortised cost Amortised cost 15,285 15,285 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 Company’s consolidated 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. Due to the current nature of the financial liabilities, the nominal value of all financial liabilities presented above approximates their fair value. The Company carried the following assets at fair value on December 31, 2018, 2017 and 2016 respectively: At December 31,2018 (in thousands of €) Level 1 Level 2 Level 3 Non-current financial assets € € € 1 Current financial assets 283,529 Assets carried at fair value € 283,529 € — € 1 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 During the disclosed calendar year no transfers occurred between the applicable categories. Given the insignificant value of the Company’s assets categorized as Level 3, the additional Level 3 disclosures have been omitted. 6.2 Capital risk The Company 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 Company 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, 2018 cash and cash equivalents amounted to €281.0 million and total capital amounted to €677.1 million. The current cash situation and the anticipated cash generation are the most important parameters in assessing the capital structure. The Company’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 Company. The Company 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 Company 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 Company holds its cash and cash equivalents mainly with different banks which are independently rated with a minimum rating of ‘BBB’. The Company 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 Company 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 Company 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 Company’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 Company’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 consolidated financial statements. 6.5 Interest rate risk The Company 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, 2018, if applicable interest rates would increase/decrease by 25 basis points, this would have a positive/negative impact of €0.3 million (compared to €0.3 million for the year ended December 31, 2017 and €0.1 million for the year ended December 31, 2016). 6.6 Foreign exchange risk The Company undertakes transactions denominated in foreign currencies; consequently, exposures to exchange rate fluctuations arise. The Company is mainly exposed to the US Dollar and GBP. The net exposure to exchange differences of the monetary assets (being cash, cash equivalents and current financial assets) of the Company at the end of the reporting period are as follows: At December 31, (in thousands of €) 2018 2017 2016 USD 312,831 147,169 624 GBP 2 406 — On December 31, 2018, if the USD/EUR exchange rate would have increased/decreased by 10%, this would have had a negative/positive impact of €28.44 million (compared to €13.38 million on December 31, 2017). On December 31, 2018, if the GBP/EUR exchange rate would have increased/decreased by 10%, this would have had no significant impact.

Other disclosures

Other disclosures	12 Months Ended
	Dec. 31, 2018
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 Operating 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 €) 2018 2017 2016 Short term employee benefits € 4,236 € 3,126 € 1,832 Post employment benefits 153 115 125 Termination benefits — — — Share ‑ based payment (1) 13,363 12,041 2,261 Employer social security contributions stock options (2) 2,792 3,073 436 € 20,544 € 18,355 € 4,654 (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 Company 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 Company 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, 2018, 2017 and 2016 (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, 2018, 2017 and 2016 and the full bonus was granted in the same year. 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 1,274,055 9,184 2,199,681 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 Pension 2018 Base salary Bonus contributions Social security costs ESOP (1) Other (2) Total Tim Van Hauwermeiren 500,000 284,600 15,102 10,011 3,559,200 33,855 4,402,768 Total 500,000 284,600 15,102 10,011 3,559,200 33,855 4,402,768 (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 Company makes a calculation of the exposure. (2) Consists of rent paid by the Company, 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, 2018, 2017 and 2016 and their exercise price equal to the fair market value upon date of grant, and the stock options exercised during 2018, 2017 and 2016. 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 years 11.47 28,200 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 years 21.17 Total 123,200 65,380 2018 ESOPs Term Exercise price Exercised Tim Van Hauwermeiren (1) 80,000 5 / 10 years 86.32 7.17 40,000 Total 80,000 40,000 (1) On December 21, 2018, the Company granted options for which the beneficiary had a 60-day period to choose between a contractual term of five or ten years. The table below shows the stock options held at the start of the year ended December 31, 2018, the stock options granted to executive directors which have vested during the year ended December 31, 2018 and the stock options to vest in the years until 2021. Total Total options options Options held on options options held on vested Options Options Options Options January 1, granted in exercised in December 31, until Exercise vested in Exercise to vest Exercise to vest Exercise to vest Exercise Name 2018 2018 2018 2018 2017 price 2018 price 2019 price 2020 price 2021 price Tim Van Hauwermeiren 296,200 80,000 (40,000) 336,200 65,000 7.17 20,400 9.47 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 26,667 86.32 26,666 86.32 26,667 86.32 The table below shows the remaining term of the options held by the executive directors on December 31, 2018. Name Number of options Remaining term at December 31, 2018 (rounded up) Tim Van Hauwermeiren 65,000 years 30,600 years 50,000 years 30,600 years 80,000 years 80,000 5.0 / 10.0 (1) years (1) On December 21, 2018, the Company granted options for which the beneficiary had a 60-day period to choose between a contractual term of five or ten 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, 2018, 2017 and 2016: 2018 2017 2016 Peter Verhaeghe € 77,500 € 77,500 € 55,000 David L Lacey 50,000 50,000 45,930 Werner Lanthaler 55,000 55,000 45,000 Pamela Klein 42,500 42,500 35,000 Don Debethizy 52,500 52,500 43,000 A.A. Rosenberg 42,500 42,500 — James M. Daly 35,000 — — Total € 355,000 € 320,000 € 223,930 The table below shows the number of stock options granted to the non-executive directors during the years ended December 31, 2018, 2017 and 2016 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, 2018, 2017 and 2016. 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 65,000 — (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 21.37 Total 15,000 — 2018 ESOPs Term Exercise price Exercised James M. Daly 15,000 10 years 80.82 Peter Verhaeghe 10,000 10 years 86.32 David L Lacey 10,000 10 years 86.32 Werner Lanthaler 10,000 10 years 86.32 2.44 3,566 7.17 5,000 2.44 10,850 11.38 5,556 Don Debethizy 10,000 10 years 86.32 Pamela Klein 10,000 10 years 86.32 A.A. Rosenberg 10,000 10 years 86.32 James M. Daly 10,000 10 years 86.32 Total 85,000 24,972 The table below shows the stock options held at the start of the year ended December 31, 2018 and the stock options granted to the non‑executive directors which have vested during the year ended December 31, 2018, as well as the stock options to vest in the years ending December 31, 2019, December 31, 2020 and December 31, 2021 (in number of stock options), and the respective exercise price of such stock options: Total Total Options Options Options options Options Options options Options Options to to to held on granted exercised held on vested vested vest vest vest January 1, in in December 31, until Exercise in Exercise in Exercise in Exercise in Exercise Name 2018 2018 2018 2018 2017 price 2018 price 2019 price 2020 price 2021 price Peter Verhaeghe 34,585 10,000 44,585 11,626 € 2.44 7,959 € 3.95 5,000 € 7.17 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 3,333 € 86.32 3,334 € 86.32 3,333 € 86.32 David L. Lacey 44,443 10,000 54,443 6,643 € 2.44 12,800 € 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 3,333 € 86.32 3,334 € 86.32 3,333 € 86.32 Werner Lanthaler 29,416 10,000 (24,972) 14,444 — € 2.44 — € 7.17 — € 11.38 2,777 € 11.38 1,667 € 11.38 3,333 € 86.32 3,334 € 86.32 3,333 € 86.32 J. Donald deBethizy 25,000 10,000 35,000 12,500 € 11.44 2,500 € 11.44 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 3,333 € 86.32 3,334 € 86.32 3,333 € 86.32 Pamela Klein 25,000 10,000 35,000 12,500 € 11.44 2,500 € 11.44 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 3,333 € 86.32 3,334 € 86.32 3,333 € 86.32 A.A. Rosenberg 15,000 10,000 25,000 5,000 € 14.13 5,000 € 14.13 5,000 € 14.13 3,333 € 86.32 3,334 € 86.32 3,333 € 86.32 James M. Daly — 25,000 25,000 7,500 € 80.82 5,000 € 80.82 2,500 € 80.82 3,333 € 86.32 3,334 € 86.32 3,333 € 86.32 The table below shows the remaining term of the stock options held by the non‑executive directors on December 31, 2018. Remaining term on Number of December 31, 2018 Name stock options (rounded up) Peter K.M. Verhaeghe 3,650 1.5 years 2,340 2.0 years 5,560 4.5 years 3,181 5.0 years 9,854 6.0 years 10,000 7.5 years 10,000 10.0 years David L. Lacey 3,180 4.5 years 1,818 5.0 years 14,445 6.0 years 10,000 7.5 years 15,000 9.0 years 10,000 10.0 years Werner Lanthaler 4,444 7.5 years 10,000 10.0 years J. Donald deBethizy 15,000 6.5 years 10,000 7.5 years 10,000 10.0 years Pamela Klein 15,000 6.5 years 10,000 7.5 years 10,000 10.0 years A.A. Rosenberg 15,000 8.0 years 10,000 10.0 years James M. Daly 15,000 9.5 years 10,000 10.0 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. 7.2 Contingencies The Company is currently not facing any outstanding claims or litigations that may have a significant adverse impact on the Company’s financial position. As described in note 5.2 the Company 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 Company 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 Company deems that the claw back risk is remote in view of the continuous monitoring of the contractual conditions. In September 2018, the Company was awarded a grant from the Flanders Innovation and Entrepreneurship Agency (“the VLAIO 2 grant”). The award of this grant is linked to the fulfillment of a specific condition in which our subsidiary argenx BVBA has to demonstrate that it does no longer meet the criteria of Article 2.18 of EU regulation nr. 651/2014 with regard to “undertakings in difficulty”. The deadline for providing supporting evidence that argenx BVBA is no longer an “undertaking in difficult” was determined on May 31, 2019 and will be based on the audited statutory accounts of argenx BVBA for the year ending December 31, 2018. Until then, all payments in respect of the VLAIO 2 grant have been suspended. The Company has recognized grant income in respect of this VLAIO 2 grant for the year ended December 31, 2018, as the equity of its subsidiary argenx BVBA has been restored and as such does no longer meet the criteria of Article 2.18 of EU regulation nr. 651/2014 with regard to “undertakings in difficulty”. The Company has fulfilled all remaining 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. As described in note 4.9, in 2018, the Company granted a total of 1,040,475 stock options to certain of its employees, Board members and consultants. As part of the grant of these stock options, the Company has undertaken to compensate Belgian taxes that are paid upon the grant of these stock options if and when at the end of the exercise period, the stock price would be lower than the exercise price, as increased with these taxes. The Company has applied for a tax ruling on this subject that would cover the stock option grants as from June 28, 2018. The exposure that the Company could face at the end of the exercise period for the stock options granted in 2018 ranges from €2.9 million to €3.5 million. 7.3 Commitments At balance sheet date, there were no commitments signed for the acquisition of property, plant and equipment or intangible assets. The Company’s manufacturing commitments with its drug substance manufacturing contractor Lonza relate to the ongoing execution of the BLA services for efgartigimod and the ongoing manufacturing activities related to the start-up of Lonza Singapore as a potential future commercial manufacturing site. In December 2018, the Company signed its first commercial supply agreement with Lonza related to the reservation of commercial drug substance supply capacity for efgartigimod. The total commitment under this commercial supply agreement amounts to a minimum commitment of £25.3 million over a period of five years starting from 2020. In the aggregate, the Company has outstanding commitments for efgartigimod of approximately €42.2 million. In addition to the obligations for efgartigimod, the Company also has contractual obligations for cusatuzumab of approximately €4.5 million starting from 2019. 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 2018 2017 2016 in thousands of € Audit fees (1) € 648 € 179 € 85 Audit-related fees 143 724 65 Tax and other services (2) — — 2 Total € 791 € 903 € 152 (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 Company’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 The Company signed a new lease agreement effective January 2, 2019 for approximately 560 square meters of additional office space in Zwijnaarde, Belgium. This lease agreement will automatically expire on the same date as the lease agreement for our current office and laboratory space, being March 31, 2025. The new lease agreement increases the future commitments with €0.7 million. On January 18, 2019, the Company announced the closing of an exclusive global collaboration and license agreement for cusatuzumab with Janssen. The collaboration agreement became effective following expiration of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act and the closing of the private placement of 1,766,899 new argenx shares at a price of €100.02 per share to Johnson & Johnson Innovation Inc. (JJDC, Inc). argenx and Janssen have agreed to a joint global clinical development plan to evaluate cusatuzumab in acute myeloid leukemia, myelodysplastic syndromes and other potential future indications. Under the terms of the agreement, Janssen has paid argenx $300 million in an upfront payment. argenx will be eligible to receive potentially up to $1.3 billion in development, regulatory and sales milestones, in addition to tiered royalties, On February 4, 2019, the Company announced that it entered into a global collaboration and license agreement with Halozyme that enables use by argenx of Halozyme’s ENHANZE® drug delivery technology to develop multiple subcutaneous product formulations for current or future argenx product candidates. Under the terms of the agreement, argenx will pay an upfront payment of $30 million to Halozyme, $10 million per target for future target nominations and potential future payments of up to $160 million per selected target, subject to achievement of specified development, regulatory and sales-based milestones. Halozyme will also receive mid-single digit royalties on sales of commercialized products. On March 14, 2019, the Company announced that ABBV-151, an antibody product candidate formerly named ARGX-115 and exclusively licensed to AbbVie, has commenced clinical development with the initiation of a first-in-human clinical trial. The attainment of this development milestone triggers a $30 million payment by AbbVie. On March 20, 2019, the Company signed a new lease agreement for approximately 580 square meters of additional office space in Boston, USA. This lease agreement will expire in July 2024. The new lease agreement increases the future commitments with $2.2 million.

Significant accounting polici_2

Significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2018
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 Company’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, 2018 and for the comparative information as of and for the years ended December 31, 2017 and 2016. 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 Company’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 significant accounting policies applied in the preparation of the above consolidated 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 March 26, 2019. Correction of an immaterial error Subsequent to the issuance of the Company’s consolidated financial statements for the year ended December 31, 2017 on Form 20-F, the Company determined that the current versus non-current classification of deferred revenue as of December 31, 2017 and December 31, 2016, respectively, was not made correctly, impacting the Company’s consolidated statement of financial position and the consolidated statement of cash flows. Management evaluated the materiality of the errors from a quantitative and qualitative perspective and concluded that this adjustment was not material to the Company’s previously issued consolidated financial statements. The Company has elected to revise the historical consolidated financial information presented herein in the consolidated statement of financial position and the consolidated statement of cash flows to reflect the correction of this error for the prior periods presented and to confirm to current year presentation. Since the revisions were not material, no amendments to previously filed reports were required. The revision had the effect of decreasing the current deferred revenue balance and increasing the non-current deferred revenue with €1.4 million as of December 31, 2017 and €10.1 million as of December 31, 2016, respectively. Each affected individual line item within the consolidated statement of cash flows relating to the change in these balances have likewise been revised. Reclassifications Certain amounts from previous periods have been reclassified to conform to the 2018 presentation. Specifically, for the years ended December 31, 2017 and December 31, 2016, issue costs paid and proceeds from exercise of stock options are now disclosed on as a separate line item on the consolidated statement of cash flows and on the consolidated statement of changes in equity.
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 the subsidiary. 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 consolidated financial statements are presented in euro (€), which is the Company’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 Leases of property, plant and equipment where the Company, as lessee, has substantially all the risks and rewards of ownership are classified as finance leases. Finance leases are capitalised at the lease’s inception at the fair value of the leased property or, if lower, the present value of the minimum lease payments. The corresponding rental obligations, net of finance charges, are included in other short-term and long-term payables. Each lease payment is allocated between the liability and finance cost. The finance cost is charged to the profit or loss over the lease period so as to produce a constant periodic rate of interest on the remaining balance of the liability for each period. The property, plant and equipment acquired under finance leases is depreciated over the asset’s useful life or over the shorter of the asset’s useful life and the lease term if there is no reasonable certainty that the Company will obtain ownership at the end of the lease term. 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. 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 instruments	2.8 Financial instruments Financial assets and financial liabilities are recognised in the Company’s statement of financial position when the Company becomes a party to the contractual provisions of the instrument. Financial assets and financial liabilities are initially measured at fair value. Transaction costs that are directly attributable to the acquisition or issue of financial assets and financial liabilities (other than financial assets and financial liabilities at fair value through profit or loss) are added to or deducted from the fair value of the financial assets or financial liabilities, as appropriate, on initial recognition. Transaction costs directly attributable to the acquisition of financial assets or financial liabilities at fair value through profit or loss are recognised immediately in profit or loss. The Company has adopted IFRS 9 on January 1, 2018. In accordance with the transitional provisions in IFRS 9, comparative figures have not been restated. The adoption of IFRS 9 had no material impact on the consolidated financial statements (see also note 6.1). 2.8.1 Investment securities (i) Classification From January 1, 2018, the Company classifies its financial assets at fair value through profit and loss (FVTPL). For assets measured at fair value, gains and losses will either be recorded in profit or loss. For investments in equity instruments that are not held for trading, this will depend on whether the Company has made an irrevocable election at the time of initial recognition to account for the equity investment at fair value through other comprehensive income (FVOCI). (ii) Recognition and derecognition Purchases and sales of financial assets are recognised on trade-date, the date on which the Company commits to purchase or sell the asset. Financial assets are derecognised when the rights to receive cash flows from the financial assets have expired or have been transferred and the Company has transferred substantially all the risks and rewards of ownership. (iii) Measurement At initial recognition, the Company measures a financial asset at its fair value. Transaction costs of financial assets carried at FVTPL are expensed in profit or loss. (iv) Impairment From January 1, 2018, the Company assesses on a forward-looking basis the expected credit losses associated with its debt instruments carried at amortised cost and FVOCI. The impairment methodology applied depends on whether there has been a significant increase in credit risk. (v) Accounting policies applied until December 31, 2017 Financial assets were 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 depended on the nature and purpose of the financial assets and was determined at the time of initial recognition. Management determined the classification at the time of the purchase and reevaluated such designation at each subsequent balance sheet date. Purchase and sale of financial assets were recognized on the settlement date, which was the date an asset is delivered to or by the Group. The cost of financial assets included transaction costs. The carrying amounts of all financial assets were reviewed for impairment whenever events or changes in circumstances indicated that the carrying amount is impaired. If objective evidence existed that a financial asset or group of financial assets was impaired, the amount of the impairment loss was 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 was immediately recognized in net finance costs. An impairment loss on financial assets was reversed if, in a subsequent period, the amount of the impairment loss decreased and this decrease could be related objectively to an event occurring after the impairment loss was recognized. Such reversal was immediately recognized in net finance costs.
Trade and other receivables	2.9 Trade and other receivables Trade receivables are recognised initially at the amount of consideration that is unconditional. The Company holds the trade receivables with the objective to collect the contractual cash flows and therefore measures them subsequently at amortised cost using the effective interest method. Unless the impact of discounting is material, the nominal value is recognized. The Company measures the loss allowance for trade receivables at an amount equal to lifetime expected credit loss. The expected credit losses are 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 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. 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. The Company has never distributed any dividends to its shareholders. As of 31 December 2018, no profits were available for distribution.
Trade and other payables	2.13 Trade and other 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.
Provisions	2.14 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	2.15 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, which are included in Research and development expenses and in Selling, general and administrative 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	2.16 Short‑term employee benefits Short‑term employee benefits include payables and accruals for salaries and bonuses to be paid to the employees of the Company. They are recognized as expenses for the period in which employees perform the corresponding services.
Share-based payments	2.17 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 4.9. 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 Company’s estimate of equity instruments that will eventually vest, with a corresponding increase in equity. At the end of each reporting period, the Company 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	2.18 Deferred revenue Current and non-current 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. IFRS 15 uses the term ‘contract liability’ to describe what might more commonly be known as ‘deferred revenue’, however IFRS 15 does not prohibit an entity from using alternative descriptions in the statement of financial position. The Company will continue to report its contract liabilities under the term ‘deferred revenue.
Income taxes	2.19 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 consolidated 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	2.20 Revenue and other operating income recognition Collaborations The Company generates revenue from collaborations and strategic alliances. The Company applies 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. Identify the contracts In our current arrangements, the Company 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 The Company has assessed that there is one single performance obligation for certain arrangements in our material ongoing license and collaboration arrangements, 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 Company 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 Company’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. 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 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 performance obligation. 5. Recognize revenue Revenue from certain arrangements is recognized over time as the Company satisfies a single performance obligation. Our collaborative partner entities simultaneously receive the benefits provided by the Company’s performance as the Company performs. The Company recognizes upfront payments and milestone payments, allocated to a single performance obligation over the estimated service period based on a pattern that reflects the transfer of the services. The revenues recognized reflect the level of service each period. In this case, the Company would use an input 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 (percentage of completion method). Research and development service fees are recognized as revenue when costs are incurred and agreed by the parties as the Company is acting as a principal in the scope of its stake of the research and development activities of its ongoing license and collaboration agreements. Grants, research and development incentives and payroll tax rebates Because it carries out extensive research and development activities, the Company 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 Company 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	2.21 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.
Adoption of new and revised standards	2.22 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 on or after January 1, 2018: ■ IFRS 9, ‘Financial instruments’ (effective for fiscal years beginning on or after January 1, 2018). This standard, which covers financial instruments on both the asset as well as the liability side, describes the criteria for recognition, classification and derecognition of such instruments, in addition to the allowed measurement methods. The adoption of IFRS 9 had no material impact on our consolidated financial statements. ■ IFRS 15 and amendments to IFRS 15, ‘Revenue from contracts with customers’ (effective for fiscal years beginning on or after January 1, 2018). The IASB and FASB have jointly published a standard regarding revenue from contracts with customers. The standard will result in better financial reporting and will improve the comparability of the top line in financial statements globally. The Company has adopted IFRS 15 on January 1, 2018. The Company elected the modified retrospective approach for the transition, which foresees that prior period figures remain as reported under the previous standard IAS 18, and the cumulative effect of applying IFRS 15 is recognized as an adjustment to the opening balance of equity as at the date of initial application (i.e., the beginning of the year 2018). In previous reporting periods, milestone payments were recognized under IAS 18 based upon the achievement of the milestone event, whereas under IFRS 15, the milestone payment is linked to a single performance obligation over the estimated service period. The revenue recognition of the upfront payments was not impacted by the transition from IAS 18 to IFRS 15. The cumulative effect of adopting IFRS 15 to the consolidated statement of financial position as of January 1, 2018 is as follows: (in thousands of €) Balance at December 31, 2017 Adjustments due to adoption IFRS 15 Balance at January 1, 2018 Assets Prepaid expenses € 2,338 € (255) € 2,083 Liabilities Deferred revenue — non-current € 1,435 € 378 € 1,813 Deferred revenue — current 8,635 2,272 10,907 Equity Accumulated losses € (100,568) € (2,395) € (102,962) In accordance with the new revenue guidance, the disclosure of the impact of adoption on the consolidated statement of financial position and the consolidated statement of profit ans loss and other comprehensive income is as follows: Consolidated statement of financial position For the Year Ended December 31, 2018 (in thousands of €) As reported Adjustments Balances without adoption of IFRS 15 Assets Prepaid expenses € 2,995 € 68 € 3,063 Liabilities Deferred revenue — current € 2,161 € (726) € 1,435 Equity Accumulated losses € (169,603) € 658 € (168,945) Consolidated statement of profit and loss and other comprehensive income For the Year Ended December 31, 2018 (in thousands of €) As reported Adjustments Balances without adoption of IFRS 15 Revenue € 21,482 € (1,924) € 19,558 Research and development expenses € (83,609) € 188 € (83,421) Loss for the year and total comprehensive loss € (66,641) € (1,736) € (68,377) There is no material impact on the basic and diluted earnings per share. Consolidated statement of cash flows For the Year Ended December 31, 2018 (in thousands of €) As reported Adjustments Balances without adoption of IFRS 15 Operating result € (81,849) € (1,736) € (83,585) Movements in current assets/liabilities: (Increase)/decrease in other current assets € (800) € 68 € (732) Increase/(decrease) in current deferred revenue (8,868) 1,668 (7,200) Cash flows (used in)/from operating activities € (53,274) € (0) € (53,274) ■ Other new standards and amendments to standards that are mandatory for the first time for the financial year beginning on or after January 1, 2018 had no material impact on our consolidated financial statements. New accounting policies and disclosures effective in 2019 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 January 1, 2018 and have been endorsed by the European Union. ■ IFRS 16, ‘Leases’ (effective for fiscal years beginning on or after January 1, 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 recognise 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 performed a preliminary assessment evaluating the guidance to determine the potential impact on the consolidated financial statements. The standard will affect primarily the accounting for the Company’s operating leases. As of the reporting date, the Company has non-cancellable operating lease commitments of €3.0 million, see note 5.7. Of these commitments, approximately €0.1 million related to short-term leases or low value leases which will be recognized on a straight-line basis as expense in profit and loss. For the remaining lease commitments, the Company expects to recognize on January 1, 2019 right-of-use assets of approximately €2.8 million and lease liabilities of approximately €2.8 million. Operating cash flows will increase and financing cash flows will decrease by approximately €1.1 million as repayment of the principal portion of the lease liabilities will be classified as cash flows from financing activities. The Company does not use EBITDA to measure its performance. We plan to adopt IFRS 16 on the effective date using the modified retrospective approach. ■ Amendments to IFRS 9, ‘Prepayment features with negative compensation’ (effective for fiscal years beginning on or after January 1, 2019 with the EU). The amendments to allow companies to measure particular prepayable financial assets with so-called negative compensation at amortised cost or at fair value through other comprehensive income if a specified condition is met—instead of at fair value through profit or loss, because they would otherwise fail the SPPI-test. In addition, this amendment clarifies an aspect of the accounting for financial liabilities following a modification. These amendments will not have any material impact on our consolidated financial statements. ■ IFRIC 23, ‘Uncertainty over income tax treatments’ (effective for fiscal years beginning on or after January 1, 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. Except for the matters already disclosed in note 4.12 of the consolidated financial statements, the Company does not anticipate that the application of this interpretation will have a material impact on the Company’s consolidated financial statements. We plan to adopt IFRIC 23 on the effective date. ■ Other new standards and amendments to standards that have been issued, but are not mandatory for the first time for the financial year beginning January 1, 2018 will have no material impact on our consolidated financial statements. The following new standards and amendments to standards have been issued, but are not mandatory for the first time for the financial year beginning January 1, 2018 and have not been endorsed by the European Union. ■ Amendments to IAS 19, ‘Plan Amendment, Curtailment or Settlement’ (effective for fiscal years beginning on or after January 1, 2019). The amendments require an entity to use updated assumptions to determine current service cost and net interest for the remainder of the period after a plan amendment, curtailment or settlement. In addition, an entity will have to recognise in profit or loss as part of past service cost, or a gain or loss on settlement, any reduction in a surplus, even if that surplus was not previously recognised because of the impact of the asset ceiling. The amendments will affect any entity that changes the terms or the membership of a defined benefit plan such that there is past service cost or a gain or loss on settlement. These amendments are not expected to have any material impact on our consolidated financial statements. ■ Amendments to References to the Conceptual Framework in IFRS Standards (effective for fiscal years beginning on or after January 1, 2020). The revised Conceptual Framework includes a new chapter on measurement; guidance on reporting financial performance; improved definitions and guidance—in particular the definition of a liability; and clarifications in important areas, such as the roles of stewardship, prudence and measurement uncertainty in financial reporting. These amendments are not expected to have any material impact on our consolidated financial statements. ■ Amendments to the definition of material in IAS 1 and IAS 8 (effective for fiscal years beginning on or after January 1, 2020). The amendments clarify the definition of material and make IFRSs more consistent. The amendment clarifies that the reference to obscuring information addresses situations in which the effect is similar to omitting or misstating that information. It also states that an entity assesses materiality in the context of the financial statements as a whole. The amendment also clarifies the meaning of ‘primary users of general purpose financial statements’ to whom those financial statements are directed, by defining them as ‘existing and potential investors, lenders and other creditors’ that must rely on general purpose financial statements for much of the financial information they need. These amendments will not have any material impact on our consolidated financial statements. ■ Annual improvements to IFRS Standards 2015-2017 cycle, applicable as of January 1, 2019 and containing the following amendments to IFRSs: o IFRS 3 Business Combinations and IFRS 11 Joint Arrangements, the amendments to IFRS 3 clarify that when an entity obtains control of a business that is a joint operation, it remeasures previously held interests in that business. The amendments to IFRS 11 clarify that when an entity obtains joint control of a business that is a joint operation, the entity does not remeasure previously held interests in that business. o IAS 12 Income Taxes, the amendments clarify that all income tax consequences of dividends (i.e. distribution of profits) should be recognised in profit or loss, regardless of how the tax arises. o IAS 23 Borrowing Costs, the amendments clarify that if any specific borrowing remains outstanding after the related asset is ready for its intended use or sale, that borrowing becomes part of the funds that an entity borrows generally when calculating the capitalisation rate on general borrowings. These improvements will not have any material impact on our consolidated financial statements.
Segment reporting	2.23 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 Company manages its activities and operates as one business unit which is reflected in its organizational structure and internal reporting. The Company does not distinguish in its internal reporting different segments, neither business nor geographical segments. The chief operating decision‑maker is the Board of Directors.

Significant accounting polici_3

Significant accounting policies (Tables)	12 Months Ended
	Dec. 31, 2018
Significant accounting policies
Schedule of cumulative effect of adoption	The cumulative effect of adopting IFRS 15 to the consolidated statement of financial position as of January 1, 2018 is as follows: (in thousands of €) Balance at December 31, 2017 Adjustments due to adoption IFRS 15 Balance at January 1, 2018 Assets Prepaid expenses € 2,338 € (255) € 2,083 Liabilities Deferred revenue — non-current € 1,435 € 378 € 1,813 Deferred revenue — current 8,635 2,272 10,907 Equity Accumulated losses € (100,568) € (2,395) € (102,962) In accordance with the new revenue guidance, the disclosure of the impact of adoption on the consolidated statement of financial position and the consolidated statement of profit ans loss and other comprehensive income is as follows: Consolidated statement of financial position For the Year Ended December 31, 2018 (in thousands of €) As reported Adjustments Balances without adoption of IFRS 15 Assets Prepaid expenses € 2,995 € 68 € 3,063 Liabilities Deferred revenue — current € 2,161 € (726) € 1,435 Equity Accumulated losses € (169,603) € 658 € (168,945) Consolidated statement of profit and loss and other comprehensive income For the Year Ended December 31, 2018 (in thousands of €) As reported Adjustments Balances without adoption of IFRS 15 Revenue € 21,482 € (1,924) € 19,558 Research and development expenses € (83,609) € 188 € (83,421) Loss for the year and total comprehensive loss € (66,641) € (1,736) € (68,377) There is no material impact on the basic and diluted earnings per share. Consolidated statement of cash flows For the Year Ended December 31, 2018 (in thousands of €) As reported Adjustments Balances without adoption of IFRS 15 Operating result € (81,849) € (1,736) € (83,585) Movements in current assets/liabilities: (Increase)/decrease in other current assets € (800) € 68 € (732) Increase/(decrease) in current deferred revenue (8,868) 1,668 (7,200) Cash flows (used in)/from operating activities € (53,274) € (0) € (53,274) ■ Other new standards and amendments to standards that are mandatory for the first time for the financial year beginning on or after January 1, 2018 had no material impact on our consolidated financial statements.

Notes relating to the consoli_2

Notes relating to the consolidated interim statement of financial position (Tables)	12 Months Ended
	Dec. 31, 2018
Notes relating to the consolidated statement of financial position
Schedule of Intangible assets	(in thousands of €) Opening balance as on January 1, 2016 Cost € 72 Accumulated amortization (65) Book value at the beginning of the year 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 Movements Additions 62 Cost of disposals (2) Amortization (19) Accumulated depreciation on disposals 2 Balance as on December 31, 2018 Cost 159 Accumulated amortization (103) Book value at year end € 56
Schedule of Property, plant and equipment	Office and lab Lease (in thousands of €) IT equipment equipment equipment Total Opening balance as on January 1, 2016 Cost € 93 € 1,179 € € 1,272 Accumulated depreciation (66) (957) (1,023) Book value at the beginning of the year 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 Movements Additions 111 259 253 623 Cost of disposals (12) (34) (46) Depreciation (64) (399) (11) (474) Accumulated depreciation on disposals 12 34 46 Closing balance as on December 31, 2018 Cost 331 2,381 253 2,965 Accumulated depreciation (209) (1,921) (11) (2,141) Book value at year end € 122 € 460 € 242 € 824
Schedule of Research and development incentive receivables	Year Ended December 31, (in thousands of €) 2018 2017 2016 Research and development incentive receivables—current € 301 € 158 € 163 Research and development incentive receivables—non-current 4,883 3,033 2,046 € 5,184 € 3,191 € 2,209
Schedule of Restricted cash	Year Ended December 31, (in thousands of €) 2018 2017 2016 Non ‑ current restricted cash Rental guarantees € 251 € 256 € 244 Escrow account > 1 year — — 905 Total non ‑ current € 251 € 256 € 1,149 Current restricted cash Escrow account < 1 year 1,692 1,692 786 Total restricted cash € 1,943 € 1,948 € 1,935
Schedule of Trade and other receivables	Year Ended December 31, (in thousands of €) 2018 2017 2016 VAT receivable € 496 € 317 € 278 Trade receivables 214 845 1,118 Other receivables 455 750 — Interest receivable 556 — 6 VLAIO grant receivable 1,165 930 568 € 2,886 € 2,842 € 1,970
Schedule of Cash and cash equivalents	Year Ended December 31, (in thousands of €) 2018 2017 2016 Cash equivalents € 217,626 € 25,000 € 54,500 Cash and bank balances 63,414 165,867 35,397 € 281,040 € 190,867 € 89,897
Schedule of Shareholders' capital	Number of shares outstanding on January 1, 2016 15,802,767 Private placement (Federated Investment) on January 20, 2016 1,480,420 Exercise of options in February 2016 2,200 Exercise of options in March 2016 10,000 Exercise of options in Apil 2016 10,000 Exercise of options in May 2016 33,092 Private placement (Sunflower) on June 1, 2016 2,703,000 Exercise of options in September 2016 70,000 Exercise of options in October 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 in August 2017 5,000 Exercise of options in September 2017 15,000 Exercise of options in October 2017 1,400 Exercise of options in November 2017 106,782 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 in December 2017 75,230 Number of shares outstanding on December 31,2017 32,180,641 Exercise of options in January 2018 111,727 Exercise of options in March 2018 113,075 Exercise of options in April 2018 34,039 Exercise of options in May 2018 5,900 Exercise of options in June 2018 5,393 Exercise of options in July 2018 469 Exercise of options in August 2018 2,300 Exercise of options in September 2018 5,913 U.S. third public offering on Nasdaq on September 18, 2018 3,475,000 Exercise of options in October 2018 556 Exercise of options in November 2018 9,768 Exercise of options in December 2018 30,531 Number of shares outstanding on December 31,2018 35,975,312
Schedule of Sharebased payment arrangements	Exercise price Outstanding per stock stock options on options December 31, Expiry date (in €) 2018 2017 2016 2020 € 3.95 18,200 36,960 112,738 2021 3.95 — 2,850 3,800 2023 2.44 294,400 314,593 360,787 2024 2.44 117,733 135,890 169,926 2024 3.95 6,895 15,692 55,746 2024 7.17 407,061 516,100 522,500 2024 2.44 26,970 83,820 83,820 2025 11.44 39,000 39,000 39,000 2025 10.34 3,000 3,000 3,000 2025 9.47 226,323 235,514 235,733 2026 11.38 50,415 60,000 60,000 2026 11.47 257,616 282,310 283,360 2026 14.13 315,102 362,126 363,226 2027 18.41 114,019 120,536 — 2027 21.17 628,292 653,825 — 2023 80.82 94,600 — — 2028 80.82 75,450 — — 2023/2028 (1) € 86.32 861,575 — — 3,536,651 2,862,216 2,293,636
Schedule of number and weighted average exercise prices of share options roll forward	2018 2017 2016 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 2,862,216 € 11.54 2,293,636 € 7.72 1,752,926 € 5.37 Granted 1,040,475 85.37 774,361 20.74 712,176 12.82 Exercised (319,671) 7.02 (203,412) 3.46 (140,292) 3.52 Forfeited (46,369) 30.44 (2,369) 12.52 (31,174) 10.90 Outstanding at December 31, 3,536,651 33.42 2,862,216 11.54 2,293,636 7.72 Exercisable at December 31, 1,859,315 € 9.62 1,598,829 € 6.80 1,257,091 € 4.68
Schedule of weighted average remaining contractual life for each range of exercise price:	Weighted average remaining Outstanding on contractual life Exercise price (in €) December 31,2018 (in years) 2.44-3.95 464,198 4.83 7.17-9.47 633,384 6.32 10.34-14.13 665,133 7.61 18.41-21.17 742,311 8.88 80.82-86.32 1,031,625 9.44
Schedule of parameters used in relation to the new grants	Below is an overview of the parameters used in relation to the grants during 2018: Stock options granted in June 2018 Dec 2018 Number of options granted 178,900 861,575 Average fair value of options (in EUR) € 32.12 € 44.49 Share price (in EUR) € 72.00 € 82.20 Exercise price (in EUR) € 80.82 € 86.32 Expected volatility 45.5 % 46.2 % Average expected option life (in years) (1) 7.36 10 Risk ‑ free interest rate 0.72 % 0.77 % Expected dividends — % — % (1) On December 21, 2018, the Company granted a total of 861,575 stock options. The beneficiary can choose between a contractual term of five or ten years. The average expected option life is currently estimated at ten years. This estimate will be reassessed once the acceptance period of 60 days has passed and the beneficiaries will have made a choice between a contractual term of five or ten years. The total fair value of the grant would range from €27.7 million (100% of the stock options at an expected option life of five years) to €38.3 million (100% of the stock options at an expected option life of ten years). 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 in an overview of the parameter 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 — % — % — %
Schedule of Defined benefit plans	(in thousands of €) 2018 2017 2016 Defined benefit obligation € 1,277 € 1,007 € 670 Fair value of plan assets 1,270 982 669 Deficit / surplus (−) of funded obligations 7 25 1 Net liability (asset) € 7 € 25 € 1
Schedule of movement in the defined benefit obligation, plan assets, net liability and asset	(in thousands of €) 2018 2017 2016 Defined benefit obligation at January 1 € 1,007 € 670 € 486 Service cost 336 352 113 Interest expense 15 11 6 Contributions by plan participants (116) (148) (64) Actuarial gains (-) / losses (+) 35 124 131 Benefits paid / transfers out — (2) (2) Defined benefit obligation at December 31 € 1,277 € 1,007 € 670 (in thousands of €) 2018 2017 2016 Fair value of plan assets at January 1 € 982 € 669 € 486 Interest income 16 10 7 Administrative costs & taxes (32) (46) (19) Contributions by company & participants 328 423 176 Contributions by plan participants (116) (148) (64) Actuarial gains (+) / losses (-) 92 76 85 Benefits paid / transfers out — (2) (2) Fair value of plan assets at December 31 € 1,270 € 982 € 669
Schedule of Actuarial assumption	Actuarial assumption 2018 2017 2016 Discount rate 1.3 % 1.3 % 1.3 %
Schedule of Sensitivity analyses	Sensitivity analysis Change in Impact on defined ‑ (in thousands of €) assumption benefit obligation % Discount rate -1.00 % Increase by 198.1 15.51 % Discount rate 1.00 % Decrease by 57.1 (4.47) %
Schedule of Trade and other payables	Year Ended December 31, (in thousands of €) 2018 2017 2016 Trade payables € 6,007 € 4,395 € 4,385 Accruals for invoices to be received 18,145 4,046 5,444 Short‑term employee benefits 12,920 6,844 2,362 € 37,072 € 15,285 € 12,191

Notes to consolidated interim s

Notes to consolidated interim statement of profit and loss and other comprehensive income (Tables)	12 Months Ended
	Dec. 31, 2018
Notes to consolidated statement of profit and loss and other comprehensive income
Schedule of revenue	Year Ended December 31, (in thousands of €) 2018 2017 2016 Upfront payments € 8,635 € 20,137 € 9,103 Milestone payments 11,440 9,677 500 Research and development service fees (FTE) 1,407 6,601 5,110 € 21,482 € 36,415 € 14,713
Schedule of other operating income	Year Ended December 31, (in thousands of €) 2018 2017 2016 Grants € 1,842 € 422 € 779 Research and development incentives 2,151 983 641 Payroll tax rebates 3,756 3,436 1,019 € 7,749 € 4,841 € 2,439
Schedule of grants	(Amounts presented in thousands of €) Flanders Innovation & Entrepreneurship - VLAIO 1 Grantor: Flanders Innovation & Entrepreneurship Agency Start date: 11/01/2017 End date: 31/10/2020 Amount granted and approved: € 2,527 Amount recognized: 982 Flanders Innovation & Entrepreneurship - VLAIO 2 Grantor: Flanders Innovation & Entrepreneurship Agency Start date: 01/05/2018 End date: 31/10/2020 Amount granted and approved: € 2,634 Amount recognized: 740
Schedule of revenue and non-current assets generated geographically	Revenue from external customers Year ended December 31, (in thousands of €) 2018 2017 2016 Netherlands € 470 € 628 € 548 Germany — — 311 Denmark 1,136 6,240 3,066 Switzerland 912 2,486 3,315 United States — 1 47 Luxembourg 18,964 27,060 7,426 Total € 21,482 € 36,415 € 14,713
Schedule of research and development expenses	Year Ended December 31, (in thousands of €) 2018 2017 2016 Personnel expense € 26,519 € 16,473 € 9,844 External research and development expenses 48,859 27,893 17,562 Materials and consumables 1,464 1,562 1,180 Depreciation and amortization 494 446 335 Other expenses 6,273 5,366 2,636 € 83,609 € 51,740 € 31,557
Schedule of general and administrative expenses	Year Ended December 31, (in thousands of €) 2018 2017 2016 Personnel expense € 18,292 € 6,745 € 3,256 Consulting fees 5,472 3,289 2,563 Supervisory board 1,088 621 446 Office costs 2,619 1,793 746 € 27,471 € 12,448 € 7,011
Schedule of personnel expenses	Year Ended December 31, (in thousands of €) 2018 2017 2016 Short ‑ term employee benefits—Salaries € 18,617 € 12,149 € 8,527 Short ‑ term employee benefits—Social Security 2,213 1,504 1,027 Post ‑ employment benefits 441 291 175 Termination benefits 96 8 86 Share ‑ based payment 18,527 3,985 2,849 Employer social security contributions stock options 4,918 5,281 436 € 44,812 € 23,218 € 13,100
Schedule of full-time equivalents employees	Year Ended December 31, Number of FTE 2018 2017 2016 Research and development 74.4 56.8 46.9 Selling, general and administrative 29.5 14.7 9.9 103.9 71.5 56.8
Schedule of operating lease commitments	Year Ended December 31, Operating lease commitments (in thousands of €) 2018 2017 2016 Less than 1 year € 1,028 € 1,028 € 915 1–3 years 1,766 465 1,159 3–5 years 210 33 24 More than 5 years — — — € 3,004 € 1,526 € 2,098
Schedule of financial result and exchange gains/(losses)	Year Ended December 31, (in thousands of €) 2018 2017 2016 Interest income on bank deposits € 1,371 € 165 € 61 Net gains on current financial assets at FVTPL 2,323 210 12 Realized gain on non-current financial assets — 875 — Financial income 3,694 1,250 73 Realized exchange gains/(losses) 1,355 — — Unrealized exchange gains/(losses) 10,953 (5,797) (31) Exchange gains/(losses) 12,308 (5,797) (31)
Schedule of income tax expenses	Year Ended December 31, (in thousands of €) 2018 2017 2016 Loss before taxes (65,847) (27,479) (21,374) Income tax calculated at 25% 16,462 6,870 5,344 Effect of expenses and gains that are not deductible in determining taxable results (3,934) (1,141) (755) Effect of stock issue expenses that are not deductible in determining taxable results 3,716 5,754 462 Effect of concessions (R&D incentives and grants) 430 453 463 Effect of tax losses carried forward not recognized (Netherlands) — — (5,551) Effect of usage of tax losses carried forward not previously recognized (Netherlands) — 19,378 — Effect of tax losses carried forward not recognized (Belgium) (5,511) (27,413) — 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 (15) (517) (180) Deferred tax asset other than loss carryforwards not recognized (11,968) (4,363) — Other 26 9 22 Income tax expense recognized in the consolidated statement of profit and loss € (794) € (597) € 0
Schedule of loss per share	Year Ended December 31, (in thousands of €) 2018 2017 2016 Loss of the year € (66,641) € (28,076) € (21,374) Weighted average number of shares outstanding 33,419,356 24,609,536 18,820,612 Basic and diluted loss per share (in €) € (1.99) € (1.14) € (1.14)

Financial instruments and fin_2

Financial instruments and financial risk management (Tables)	12 Months Ended
	Dec. 31, 2018
Financial instruments and financial risk management
Schedule of overview of financial instruments	Measurement category Carrying amount Original New Original New (in thousands of €) IAS 39 IFRS 9 IAS 39 IFRS 9 Financial assets — non-current Available for sale FVTPL € 1 € 1 Research and development incentive receivables — non-current Amortised cost Amortised cost 3,033 3,033 Restricted cash — non-current Amortised cost Amortised cost 256 256 Trade and other receivables Amortised cost Amortised cost 2,842 2,842 Prepaid expenses Amortised cost Amortised cost 2,338 2,338 Financial assets—current FVTPL FVTPL 168,907 168,907 Research and development incentive receivables — current Amortised cost Amortised cost 158 158 Restricted cash — current Amortised cost Amortised cost 1,692 1,692 Cash and cash equivalents Amortised cost Amortised cost 190,867 190,867 Trade and other payables Amortised cost Amortised cost 15,285 15,285
Schedule of assets at fair value	At December 31,2018 (in thousands of €) Level 1 Level 2 Level 3 Non-current financial assets € € € 1 Current financial assets 283,529 Assets carried at fair value € 283,529 € — € 1 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
Schedule of net exposure exchange differences of the monetary assets	At December 31, (in thousands of €) 2018 2017 2016 USD 312,831 147,169 624 GBP 2 406 —

Other disclosures (Tables)

Other disclosures (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of transactions between related parties [line items]
Schedule of remuneration of key management personnel	Year Ended December 31, (in thousands of €) 2018 2017 2016 Short term employee benefits € 4,236 € 3,126 € 1,832 Post employment benefits 153 115 125 Termination benefits — — — Share ‑ based payment (1) 13,363 12,041 2,261 Employer social security contributions stock options (2) 2,792 3,073 436 € 20,544 € 18,355 € 4,654 (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 Company 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 Company makes a calculation of the exposure.
Schedule of number and weighted average exercise prices of share options roll forward	2018 2017 2016 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 2,862,216 € 11.54 2,293,636 € 7.72 1,752,926 € 5.37 Granted 1,040,475 85.37 774,361 20.74 712,176 12.82 Exercised (319,671) 7.02 (203,412) 3.46 (140,292) 3.52 Forfeited (46,369) 30.44 (2,369) 12.52 (31,174) 10.90 Outstanding at December 31, 3,536,651 33.42 2,862,216 11.54 2,293,636 7.72 Exercisable at December 31, 1,859,315 € 9.62 1,598,829 € 6.80 1,257,091 € 4.68
Schedule of auditors' fees expensed in the income statement	Year Ended December 31, Fees 2018 2017 2016 in thousands of € Audit fees (1) € 648 € 179 € 85 Audit-related fees 143 724 65 Tax and other services (2) — — 2 Total € 791 € 903 € 152 (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 remuneration of key management personnel	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 1,274,055 9,184 2,199,681 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 Pension 2018 Base salary Bonus contributions Social security costs ESOP (1) Other (2) Total Tim Van Hauwermeiren 500,000 284,600 15,102 10,011 3,559,200 33,855 4,402,768 Total 500,000 284,600 15,102 10,011 3,559,200 33,855 4,402,768 (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 Company makes a calculation of the exposure. (2) Consists of rent paid by the Company, 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, 2018, 2017 and 2016 and their exercise price equal to the fair market value upon date of grant, and the stock options exercised during 2018, 2017 and 2016. 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 years 11.47 28,200 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 years 21.17 Total 123,200 65,380 2018 ESOPs Term Exercise price Exercised Tim Van Hauwermeiren (1) 80,000 5 / 10 years 86.32 7.17 40,000 Total 80,000 40,000 (1) On December 21, 2018, the Company granted options for which the beneficiary had a 60-day period to choose between a contractual term of five or ten years. The table below shows the stock options held at the start of the year ended December 31, 2018, the stock options granted to executive directors which have vested during the year ended December 31, 2018 and the stock options to vest in the years until 2021. Total Total options options Options held on options options held on vested Options Options Options Options January 1, granted in exercised in December 31, until Exercise vested in Exercise to vest Exercise to vest Exercise to vest Exercise Name 2018 2018 2018 2018 2017 price 2018 price 2019 price 2020 price 2021 price Tim Van Hauwermeiren 296,200 80,000 (40,000) 336,200 65,000 7.17 20,400 9.47 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 26,667 86.32 26,666 86.32 26,667 86.32
Schedule of weighted average contractual term	Name Number of options Remaining term at December 31, 2018 (rounded up) Tim Van Hauwermeiren 65,000 years 30,600 years 50,000 years 30,600 years 80,000 years 80,000 5.0 / 10.0 (1) years (1) On December 21, 2018, the Company granted options for which the beneficiary had a 60-day period to choose between a contractual term of five or ten years.
Non-executive Directors
Disclosure of transactions between related parties [line items]
Schedule of remuneration of key management personnel	2018 2017 2016 Peter Verhaeghe € 77,500 € 77,500 € 55,000 David L Lacey 50,000 50,000 45,930 Werner Lanthaler 55,000 55,000 45,000 Pamela Klein 42,500 42,500 35,000 Don Debethizy 52,500 52,500 43,000 A.A. Rosenberg 42,500 42,500 — James M. Daly 35,000 — — Total € 355,000 € 320,000 € 223,930
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, 2018, 2017 and 2016 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, 2018, 2017 and 2016. 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 65,000 — (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 21.37 Total 15,000 — 2018 ESOPs Term Exercise price Exercised James M. Daly 15,000 10 years 80.82 Peter Verhaeghe 10,000 10 years 86.32 David L Lacey 10,000 10 years 86.32 Werner Lanthaler 10,000 10 years 86.32 2.44 3,566 7.17 5,000 2.44 10,850 11.38 5,556 Don Debethizy 10,000 10 years 86.32 Pamela Klein 10,000 10 years 86.32 A.A. Rosenberg 10,000 10 years 86.32 James M. Daly 10,000 10 years 86.32 Total 85,000 24,972 The table below shows the stock options held at the start of the year ended December 31, 2018 and the stock options granted to the non‑executive directors which have vested during the year ended December 31, 2018, as well as the stock options to vest in the years ending December 31, 2019, December 31, 2020 and December 31, 2021 (in number of stock options), and the respective exercise price of such stock options: Total Total Options Options Options options Options Options options Options Options to to to held on granted exercised held on vested vested vest vest vest January 1, in in December 31, until Exercise in Exercise in Exercise in Exercise in Exercise Name 2018 2018 2018 2018 2017 price 2018 price 2019 price 2020 price 2021 price Peter Verhaeghe 34,585 10,000 44,585 11,626 € 2.44 7,959 € 3.95 5,000 € 7.17 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 3,333 € 86.32 3,334 € 86.32 3,333 € 86.32 David L. Lacey 44,443 10,000 54,443 6,643 € 2.44 12,800 € 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 3,333 € 86.32 3,334 € 86.32 3,333 € 86.32 Werner Lanthaler 29,416 10,000 (24,972) 14,444 — € 2.44 — € 7.17 — € 11.38 2,777 € 11.38 1,667 € 11.38 3,333 € 86.32 3,334 € 86.32 3,333 € 86.32 J. Donald deBethizy 25,000 10,000 35,000 12,500 € 11.44 2,500 € 11.44 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 3,333 € 86.32 3,334 € 86.32 3,333 € 86.32 Pamela Klein 25,000 10,000 35,000 12,500 € 11.44 2,500 € 11.44 5,000 € 11.38 3,333 € 11.38 1,667 € 11.38 3,333 € 86.32 3,334 € 86.32 3,333 € 86.32 A.A. Rosenberg 15,000 10,000 25,000 5,000 € 14.13 5,000 € 14.13 5,000 € 14.13 3,333 € 86.32 3,334 € 86.32 3,333 € 86.32 James M. Daly — 25,000 25,000 7,500 € 80.82 5,000 € 80.82 2,500 € 80.82 3,333 € 86.32 3,334 € 86.32 3,333 € 86.32
Schedule of weighted average contractual term	Remaining term on Number of December 31, 2018 Name stock options (rounded up) Peter K.M. Verhaeghe 3,650 1.5 years 2,340 2.0 years 5,560 4.5 years 3,181 5.0 years 9,854 6.0 years 10,000 7.5 years 10,000 10.0 years David L. Lacey 3,180 4.5 years 1,818 5.0 years 14,445 6.0 years 10,000 7.5 years 15,000 9.0 years 10,000 10.0 years Werner Lanthaler 4,444 7.5 years 10,000 10.0 years J. Donald deBethizy 15,000 6.5 years 10,000 7.5 years 10,000 10.0 years Pamela Klein 15,000 6.5 years 10,000 7.5 years 10,000 10.0 years A.A. Rosenberg 15,000 8.0 years 10,000 10.0 years James M. Daly 15,000 9.5 years 10,000 10.0 years

Significant accounting polici_4

Significant accounting policies (Details) € in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018EUR (€)	Dec. 31, 2018USD ($)	Jan. 01, 2018USD ($)	Dec. 31, 2017EUR (€)	Dec. 31, 2017USD ($)	Dec. 31, 2016EUR (€)
Intangible assets
Deferred revenue	€ 2,161	$ 2,161	$ 10,907	€ 8,635	$ 8,635	€ 20,136
Deferred revenue — non-current			$ 1,813	1,435	$ 1,435	10,070
Increase (decrease) due to corrections of prior period errors
Intangible assets
Deferred revenue				(1,400)		(10,100)
Deferred revenue — non-current				€ 1,400		€ 10,100
Software
Intangible assets
Amortization period	3 years

Significant accounting polici_5

Significant accounting policies - Property Plant and Equipment and Others (Details) € in Thousands	12 Months Ended
	Dec. 31, 2018EUR (€)item	Dec. 31, 2017
Property, plant and equipment
Impairment of assets	€ 0
Minimum Refund Period of Research and Development Incentives	5 years	5 years
Profit available for distribution	€ 0
Number of operating segments | item	1
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 polici_6

Significant accounting policies - Retirement Benefits (Details)	12 Months Ended
	Dec. 31, 2018	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%

Significant accounting polici_7

Significant accounting policies - Cumulative effect of adopting IFRS15 (Details) € in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018EUR (€)	Dec. 31, 2018USD ($)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)	Dec. 31, 2018USD ($)	Jan. 01, 2018USD ($)	Dec. 31, 2017USD ($)
ASSETS
Prepaid expenses	€ 2,995		€ 2,338	€ 2,146	$ 2,995	$ 2,083	$ 2,338
Liabilities
Deferred revenue — non-current			1,435	10,070		1,813	1,435
Deferred revenue - current	2,161		8,635	20,136	2,161	10,907	8,635
Equity
Accumulated losses	(169,603)		(100,568)	(72,492)	(169,603)	(102,962)	$ (100,568)
Consolidated statement of profit and loss and other comprehensive income
Revenue	21,482	$ 21,482	36,415	14,713
Research and development expenses	(83,609)	(83,609)	(51,740)	(31,557)
Loss for the year and total comprehensive loss	(66,641)	(66,641)	(28,076)	(21,374)
Consolidated statement of cash flows
Operating result	(81,849)	(81,849)	(22,932)	(21,416)
Movements in Current Assets or Liabilities [Abstract]
(Increase)/decrease in other current assets	(800)	(800)	(1,093)	(2,641)
Increase/(decrease) in current deferred revenue	(8,868)	(8,868)	(11,501)	7,545
Cash flows (used in)/from operating activities	€ (53,274)	(53,274)	€ (36,546)	€ 10,599
Balances without adoption of IFRS 15
ASSETS
Prepaid expenses					3,063
Liabilities
Deferred revenue - current					1,435
Equity
Accumulated losses					(168,945)
Consolidated statement of profit and loss and other comprehensive income
Revenue		19,558
Research and development expenses		(83,421)
Loss for the year and total comprehensive loss		(68,377)
Consolidated statement of cash flows
Operating result		(83,585)
Movements in Current Assets or Liabilities [Abstract]
(Increase)/decrease in other current assets		(732)
Increase/(decrease) in current deferred revenue		(7,200)
Cash flows (used in)/from operating activities		(53,274)
Adjustments due to adoption IFRS 15
ASSETS
Prepaid expenses					68	(255)
Liabilities
Deferred revenue — non-current						378
Deferred revenue - current					(726)	2,272
Equity
Accumulated losses					$ 658	$ (2,395)
Consolidated statement of profit and loss and other comprehensive income
Revenue		(1,924)
Research and development expenses		188
Loss for the year and total comprehensive loss		(1,736)
Consolidated statement of cash flows
Operating result		(1,736)
Movements in Current Assets or Liabilities [Abstract]
(Increase)/decrease in other current assets		68
Increase/(decrease) in current deferred revenue		1,668
Cash flows (used in)/from operating activities		$ 0

Significant accounting polici_8

Significant accounting policies - New accounting policies and disclosures (Details) - EUR (€) € in Thousands	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Significant accounting policies
Operating lease commitments		€ 3,004	€ 1,526	€ 2,098
Short term leases		€ 100
Right-of-use assets	€ 2,800
Lease liabilities	2,800
Repayments of lease liabilities	€ 1,100

Critical accounting judgement_2

Critical accounting judgements and key sources of estimation uncertainty - (Details) € in Millions	Dec. 31, 2018EUR (€)
Critical accounting judgements and key sources of estimation uncertainty
Cash and cash equivalents and current financial assets	€ 564.6

Notes relating to the consoli_3

Notes relating to the consolidated statement of financial position (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Intangible assets
Intangible assets other than goodwill at beginning of period	€ 13	€ 17
Intangible assets other than goodwill at end of period	56	13	€ 17
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	13	17	7
Additions	62	6	21
Amortization	(19)	(10)	(11)
Intangible assets other than goodwill at end of period	56	13	17
Cost | Software
Intangible assets
Intangible assets other than goodwill at beginning of period	99	93	72
Cost of disposals	(2)
Intangible assets other than goodwill at end of period	159	99	93
Accumulated depreciation and amortization | Software
Intangible assets
Intangible assets other than goodwill at beginning of period	86	76	65
Cost of disposals	2
Intangible assets other than goodwill at end of period	€ 103	€ 86	€ 76

Notes relating to the consoli_4

Notes relating to the consolidated statement of financial position - PPE (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, plant and equipment
Property, plant and equipment at beginning of period	€ 676	€ 766	€ 249
Additions	623	346	840
Depreciation	(474)	(425)	(323)
Property, plant and equipment at end of period	824	676	766
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 receivables	455	750
IT equipment
Property, plant and equipment
Property, plant and equipment at beginning of period	76	104	27
Additions	111	25	115
Depreciation	(64)	(53)	(38)
Property, plant and equipment at end of period	122	76	104
Office and lab equipment
Property, plant and equipment
Property, plant and equipment at beginning of period	600	662	222
Additions	259	321	725
Depreciation	(399)	(372)	(285)
Property, plant and equipment at end of period	460	600	662
Lease equipment
Property, plant and equipment
Additions	253
Depreciation	(11)
Property, plant and equipment at end of period	242
Cost
Property, plant and equipment
Property, plant and equipment at beginning of period	2,389	2,112	1,272
Sales and disposals	(46)	(69)
Property, plant and equipment at end of period	2,965	2,389	2,112
Cost | IT equipment
Property, plant and equipment
Property, plant and equipment at beginning of period	233	208	93
Sales and disposals	(12)
Property, plant and equipment at end of period	331	233	208
Cost | Office and lab equipment
Property, plant and equipment
Property, plant and equipment at beginning of period	2,156	1,904	1,179
Sales and disposals	(34)	(69)
Property, plant and equipment at end of period	2,381	2,156	1,904
Cost | Lease equipment
Property, plant and equipment
Property, plant and equipment at end of period	253
Accumulated depreciation and amortization
Property, plant and equipment
Property, plant and equipment at beginning of period	1,713	1,346	1,023
Sales and disposals	46	58
Property, plant and equipment at end of period	2,141	1,713	1,346
Accumulated depreciation and amortization | IT equipment
Property, plant and equipment
Property, plant and equipment at beginning of period	157	104	66
Sales and disposals	12
Property, plant and equipment at end of period	209	157	104
Accumulated depreciation and amortization | Office and lab equipment
Property, plant and equipment
Property, plant and equipment at beginning of period	1,556	1,242	957
Sales and disposals	34	58
Property, plant and equipment at end of period	1,921	€ 1,556	€ 1,242
Accumulated depreciation and amortization | Lease equipment
Property, plant and equipment
Property, plant and equipment at end of period	€ 11

Notes relating to the consoli_5

Notes relating to the consolidated statement of financial position - Research and development incentive receivables (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Notes relating to the consolidated statement of financial position
Research and development incentive receivables - Current	€ 301	€ 158	€ 163
Research and development incentive receivables - non-current	4,883	3,033	2,046
Total	€ 5,184	€ 3,191	€ 2,209
Minimum refund period of research and development incentive receivables.	5 years	5 years

Notes relating to the consoli_6

Notes relating to the consolidated statement of financial position - Noncurrent restricted cash (Details) - EUR (€) € in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Notes relating to the consolidated statement of financial position
Rental guarantees	€ 251	€ 256	€ 244
Escrow account more than year			905
Total noncurrent	251	256	1,149
Escrow account less than 1 year	1,692	1,692	786
Total restricted cash	€ 1,943	€ 1,948	€ 1,935

Notes relating to the consoli_7

Notes relating to the consolidated statement of financial position - Trade and other receivables (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Trade and other receivables
VAT receivable	€ 496	€ 317	€ 278
Trade receivables	214	845	1,118
Other receivables	455	750
Interest receivable	556		6
VLAIO grant receivable	1,165	930	568
Total trade and other current receivables	2,886	2,842	1,970
Government grant received from Flanders Innovation and Entrepreneurship Agency	1,842	€ 422	€ 779
Flanders Innovation and Entrepreneurship Agency
Trade and other receivables
Government grant received from Flanders Innovation and Entrepreneurship Agency	€ 0

Notes relating to the consoli_8

Notes relating to the consolidated statement of financial position - Current financial assets (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other current financial assets
Financial assets — current	€ 283,529	€ 168,907	€ 6,831
Maturity Term	6 months

Notes relating to the consoli_9

Notes relating to the consolidated statement of financial position - Cash and cash equivalents (Details) - EUR (€) € in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes relating to the consolidated statement of financial position
Cash equivalents	€ 217,626	€ 25,000	€ 54,500
Cash and bank balances	63,414	165,867	35,397
Total cash and cash equivalents	€ 281,040	€ 190,867	€ 89,897	€ 35,514

Notes relating to the consol_10

Notes relating to the consolidated statement of financial position - Shareholders' capital (Details)	Dec. 31, 2018EUR (€)shares	Sep. 18, 2018EUR (€)€ / sharesshares	Dec. 15, 2017EUR (€)	Dec. 14, 2017$ / sharesshares	Dec. 13, 2017shares	May 19, 2017EUR (€)shares	May 17, 2017$ / sharesshares	Jun. 01, 2016shares	Jan. 20, 2016shares	Dec. 31, 2018shares	Nov. 30, 2018shares	Oct. 31, 2018shares	Sep. 30, 2018shares	Aug. 31, 2018shares	Jul. 31, 2018shares	Jun. 30, 2018shares	May 31, 2018shares	Apr. 30, 2018shares	Mar. 31, 2018shares	Jan. 31, 2018shares	Dec. 31, 2017shares	Nov. 30, 2017shares	Oct. 31, 2017shares	Sep. 30, 2017shares	Aug. 31, 2017shares	Oct. 31, 2016shares	Sep. 30, 2016shares	Jun. 30, 2016shares	May 31, 2016shares	Apr. 30, 2016shares	Mar. 31, 2016shares	Feb. 29, 2016shares	Jan. 31, 2016shares	Dec. 31, 2018shares	Dec. 31, 2017EUR (€)shares	Dec. 31, 2018€ / sharesshares	Dec. 31, 2017€ / sharesshares	Dec. 31, 2016EUR (€)€ / sharesshares	Jan. 01, 2016shares
Disclosure of classes of share capital [line items]
Number of shares outstanding	35,975,312									35,975,312										32,180,641	32,180,641													32,180,641	20,126,479	35,975,312	32,180,641	20,126,479	15,802,767
Number of shares outstanding at beginning of period																				32,180,641														32,180,641	20,126,479
New shares issued for private placement, initial public offering, public offering and underwriters' over-allotment option		3,475,000		666,000	4,440,000	879,750	5,865,000		1,480,420																			2,703,000					1,480,420		5,106,000
Exercise of Options										30,531	9,768	556	5,913	2,300	469	5,393	5,900	34,039	113,075	111,727	75,230	106,782	1,400	15,000	5,000	15,000	70,000		33,092	10,000	10,000	2,200
Number of shares outstanding at end of period	35,975,312									35,975,312											32,180,641													35,975,312	32,180,641
Share price | (per share)		€ 86.50		$ 52			$ 17
Number of shares on conversion							1																											1
Gross proceeds from issue of shares | €		€ 255,700,000	€ 225,600,000			€ 102,100,000
Underwriter discounts and commissions, and offering expenses | €		14,800,000	14,300,000			9,600,000
Expenses deducted from equity | €		14,700,000	14,100,000			8,900,000
Net proceeds | €		€ 240,900,000	€ 211,300,000			€ 92,500,000
Number of share options issued																																		319,671
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%																																		20.00%
Period of outstanding share capital	18 months																																		18 months
Maximum authorized increase in share capital | €	€ 648,790																																		€ 537,852.60
Maximum authorized increase in number of shares	6,487,896																																		5,378,526
Number of shares covered by existing authorization	3,012,896																																		272,526
IFRS Employee Stock Option [Member]
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 consol_11

Notes relating to the consolidated statement of financial position - Share-based payments (Details)	Dec. 21, 2018Y	May 17, 2017shares	Dec. 31, 2018EUR (€)EquityInstrumentsY	Jun. 30, 2018EUR (€)Y	Dec. 31, 2017EUR (€)EquityInstrumentsY	Jun. 30, 2017EUR (€)Y	Dec. 31, 2016EUR (€)EquityInstrumentsY	Jun. 30, 2016EUR (€)Y	May 31, 2016EUR (€)Y	Dec. 31, 2018EUR (€)EquityInstrumentsshares	Dec. 31, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments	Dec. 31, 2015EquityInstruments
Disclosure of terms and conditions of share-based payment arrangement [line items]
Options expired										0	0	0
Exercised										319,671	203,412	140,292
Forfeited										46,369	2,369	31,174
Number of shares on conversion | shares		1								1
Vesting period										24 months
Exercise price per stock options | €			€ 86.32	€ 80.82	€ 21.17	€ 18.41	€ 14.13	€ 11.38	€ 11.47	€ 86.32	€ 21.17	€ 14.13
Outstanding stock options			3,536,651		2,862,216		2,293,636			3,536,651	2,862,216	2,293,636	1,752,926
Time period for beneficiaries to choose contractual term (in days)	60 days
Option life (in years) | Y			10	7.36	10	10	10	10	10
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 | 2020
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €			€ 3.95							€ 3.95
Outstanding stock options			18,200		36,960		112,738			18,200	36,960	112,738
3.95 | 2021
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €			€ 3.95							€ 3.95
Outstanding stock options					2,850		3,800				2,850	3,800
3.95 | 2024
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €			€ 3.95							€ 3.95
Outstanding stock options			6,895		15,692		55,746			6,895	15,692	55,746
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							€ 2.44
Outstanding stock options			294,400		314,593		360,787			294,400	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							€ 2.44
Outstanding stock options			117,733		135,890		169,926			117,733	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							€ 2.44
Outstanding stock options			26,970		83,820		83,820			26,970	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							€ 7.17
Outstanding stock options			407,061		516,100		522,500			407,061	516,100	522,500
11.44 | 2025
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €			€ 11.44							€ 11.44
Outstanding stock options			39,000		39,000		39,000			39,000	39,000	39,000
10.34 | 2025
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €			€ 10.34							€ 10.34
Outstanding stock options			3,000		3,000		3,000			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							€ 9.47
Outstanding stock options			226,323		235,514		235,733			226,323	235,514	235,733
11.38 | 2026
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €			€ 11.38							€ 11.38
Outstanding stock options			50,415		60,000		60,000			50,415	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							€ 11.47
Outstanding stock options			257,616		282,310		283,360			257,616	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							€ 14.13
Outstanding stock options			315,102		362,126		363,226			315,102	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							€ 18.41
Outstanding stock options			114,019		120,536					114,019	120,536
21.17 | 2027
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €			€ 21.17							€ 21.17
Outstanding stock options			628,292		653,825					628,292	653,825
80.82 | 2023
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €			€ 80.82							€ 80.82
Outstanding stock options			94,600							94,600
80.82 | 2028
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €			€ 80.82							€ 80.82
Outstanding stock options			75,450							75,450
86.32 | 2023/2028
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price per stock options | €			€ 86.32							€ 86.32
Outstanding stock options			861,575							861,575
Maximum
Disclosure of terms and conditions of share-based payment arrangement [line items]
Option life (in years) | Y	10
Minimum
Disclosure of terms and conditions of share-based payment arrangement [line items]
Option life (in years) | Y	5

Notes relating to the consol_12

Notes relating to the consolidated statement of financial position - Share-based payments - Rollforward (Details)	1 Months Ended							12 Months Ended
	Dec. 31, 2018EUR (€)EquityInstrumentsY	Jun. 30, 2018EquityInstruments	Dec. 31, 2017EUR (€)EquityInstrumentsY	Jun. 30, 2017EquityInstruments	Dec. 31, 2016EUR (€)EquityInstrumentsY	Jun. 30, 2016EquityInstruments	May 31, 2016EquityInstruments	Dec. 31, 2018EUR (€)EquityInstrumentsY	Dec. 31, 2017EUR (€)EquityInstrumentsY	Dec. 31, 2016EUR (€)EquityInstrumentsY
Number of stock options
Total options at beginning of year | EquityInstruments								2,862,216	2,293,636	1,752,926
Granted | EquityInstruments	861,575	178,900	653,825	120,536	363,226	60,000	288,950	1,040,475	774,361	712,176
Exercised | EquityInstruments								(319,671)	(203,412)	(140,292)
Forfeited | EquityInstruments								(46,369)	(2,369)	(31,174)
Total options at end of year | EquityInstruments	3,536,651		2,862,216		2,293,636			3,536,651	2,862,216	2,293,636
Exercisable | EquityInstruments	1,859,315		1,598,829		1,257,091			1,859,315	1,598,829	1,257,091
Weighted average exercise price
Beginning balance | €								€ 11.54	€ 7.72	€ 5.37
Granted | €								85.37	20.74	12.82
Exercised | €								7.02	3.46	3.52
Forfeited | €								30.44	12.52	10.90
Ending balance | €	€ 33.42		€ 11.54		€ 7.72			33.42	11.54	7.72
Exercisable | €	€ 9.62		€ 6.80		€ 4.68			€ 9.62	€ 6.80	€ 4.68
Weighted average remaining contractual life of outstanding share options | Y	7.82		8.03		8.09			7.82	8.03	8.09

Notes relating to the consol_13

Notes relating to the consolidated statement of financial position - Share-based payments - Range of exercise price (Details)	Dec. 31, 2018EUR (€)EquityInstrumentsY	Jun. 30, 2018EUR (€)	Dec. 31, 2017EUR (€)EquityInstrumentsY	Jun. 30, 2017EUR (€)	Dec. 31, 2016EUR (€)EquityInstrumentsY	Jun. 30, 2016EUR (€)	May 31, 2016EUR (€)	Dec. 31, 2015EquityInstruments
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	€ 86.32	€ 80.82	€ 21.17	€ 18.41	€ 14.13	€ 11.38	€ 11.47
Number of share options outstanding in share-based payment arrangement | EquityInstruments	3,536,651		2,862,216		2,293,636			1,752,926
Weighted average remaining contractual life | Y	7.82		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	464,198
Weighted average remaining contractual life | Y	4.83
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	633,384
Weighted average remaining contractual life | Y	6.32
10.34-14.13
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of share options outstanding in share-based payment arrangement | EquityInstruments	665,133
Weighted average remaining contractual life | Y	7.61
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	742,311
Weighted average remaining contractual life | Y	8.88
80.82-86.32
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of share options outstanding in share-based payment arrangement | EquityInstruments	1,031,625
Weighted average remaining contractual life | Y	9.44
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 | 10.34-14.13
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	10.34
Minimum | 18.41-21.17
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	18.41
Minimum | 80.82-86.32
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	80.82
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 | 10.34-14.13
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
Maximum | 80.82-86.32
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price	€ 86.32

Notes relating to the consol_14

Notes relating to the consolidated statement of financial position - Share-based payments - Overview (Details)	Dec. 21, 2018EUR (€)Y	Dec. 31, 2018EUR (€)EquityInstrumentsY	Jun. 30, 2018EUR (€)EquityInstrumentsY	Dec. 31, 2017EUR (€)EquityInstrumentsY	Jun. 30, 2017EUR (€)EquityInstrumentsY	Dec. 31, 2016EUR (€)EquityInstrumentsY	Jun. 30, 2016EUR (€)EquityInstrumentsY	May 31, 2016EUR (€)EquityInstrumentsY	Dec. 31, 2018EUR (€)EquityInstruments	Dec. 31, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options granted | EquityInstruments		861,575	178,900	653,825	120,536	363,226	60,000	288,950	1,040,475	774,361	712,176
Average fair value of options		€ 44.49	€ 32.12	€ 37.10	€ 7.90	€ 7.25	€ 5.46	€ 5.32	€ 44.49	€ 37.10	€ 7.25
Share price		82.20	72	53.50	17.76	14.96	11.36	11.10
Exercise price		€ 86.32	€ 80.82	€ 21.17	€ 18.41	€ 14.13	€ 11.38	€ 11.47	86.32	21.17	14.13
Expected volatility		46.20%	45.50%	36.10%	36.60%	38.00%	39.60%	40.20%
Riskfree interest rate		0.77%	0.72%	0.53%	0.61%	0.67%	0.46%	0.52%
Total share based payment expense									€ 19,200,000	4,300,000	2,300,000
Vesting period									24 months
Average expected option life (in years) | Y		10	7.36	10	10	10	10	10
Time period for beneficiaries to choose contractual term (in days)	60 days
Total fair value of grant		€ 44.49	€ 32.12	€ 37.10	€ 7.90	€ 7.25	€ 5.46	€ 5.32	€ 44.49	€ 37.10	€ 7.25
Share options granted (as a percent)	100.00%
Maximum
Disclosure of terms and conditions of share-based payment arrangement [line items]
Average fair value of options	€ 38,300,000
Average expected option life (in years) | Y	10
Total fair value of grant	€ 38,300,000
Minimum
Disclosure of terms and conditions of share-based payment arrangement [line items]
Average fair value of options	€ 27,700,000
Average expected option life (in years) | Y	5
Total fair value of grant	€ 27,700,000

Notes relating to the consol_15

Notes relating to the consolidated statement of financial position - Defined Benefit Plans (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of net defined benefit liability (asset) [line items]
Minimum guaranteed reserve			€ 1
Deficit / surplus () of funded obligations	€ 7	€ 25	1
Net liability (asset)	7	25	1
Employer contributions	200	300	100
Defined benefit obligation
Disclosure of net defined benefit liability (asset) [line items]
Net liability (asset)	1,277	1,007	670	€ 486
Fair value of plan assets
Disclosure of net defined benefit liability (asset) [line items]
Net liability (asset)	€ 1,270	€ 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 consol_16

Notes relating to the consolidated statement of financial position - Defined Benefit Plans - Rollforward (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of net defined benefit liability (asset) [line items]
Beginning balance	€ 25	€ 1
Ending balance	€ 7	€ 25	€ 1
Discount rate	1.30%	1.30%	1.30%
Term of Benefit Obligations	18 years
Weighted average age of the plan participants	43 years 9 months 18 days	46 years	48 years
Defined benefit obligation
Disclosure of net defined benefit liability (asset) [line items]
Beginning balance	€ 1,007	€ 670	€ 486
Service cost	336	352	113
Interest expense / income ()	15	11	6
Contributions by plan participants	(116)	(148)	(64)
Actuarial gains (+) / losses (-)	35	124	131
Benefits paid / transfers out		(2)	(2)
Ending balance	1,277	1,007	670
Fair value of plan assets
Disclosure of net defined benefit liability (asset) [line items]
Beginning balance	982	669	486
Interest expense / income ()	16	10	7
Administrative costs and taxes	(32)	(46)	(19)
Contributions by company & participants	328	423	176
Contributions by plan participants	(116)	(148)	(64)
Actuarial gains (+) / losses (-)	92	76	85
Benefits paid / transfers out		(2)	(2)
Ending balance	€ 1,270	€ 982	€ 669

Notes relating to the consol_17

Notes relating to the consolidated statement of financial position - Defined Benefit Plans - Sensitivity Analysis (Details) - Discount rate	12 Months Ended
	Dec. 31, 2018EUR (€)
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Decrease in percentage	1.00%
Increase in percentage	1.00%
Defined benefit obligation increase due to increase in discount rate	€ 198,100
Defined benefit obligation decrease due to decrease in discount rate	€ 57,100
Defined benefit obligation increase (in percentage)	15.51%
Defined benefit obligation decrease (in percentage)	(4.47%)

Notes relating to the consol_18

Notes relating to the consolidated statement of financial position - Current tax liability (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of subsidiaries [line items]
Loss before taxes	€ (65,847)	€ (27,479)	€ (21,374)
Applicable tax rate	25.00%	25.00%	25.00%
Current tax liabilities	€ 823	€ 597
Deferred tax asset recognized	117,100
ARGENX BVBA
Disclosure of subsidiaries [line items]
Current tax liabilities	800
Additional tax deductible costs	€ 79,900

Notes relating to the consol_19

Notes relating to the consolidated statement of financial position - Trade and other payables (Details) - EUR (€) € in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Notes relating to the consolidated statement of financial position
Trade payables	€ 6,007	€ 4,395	€ 4,385
Accruals for invoices to be received	18,145	4,046	5,444
Short-term employee benefits accruals	€ 12,920	€ 6,844	€ 2,362

Notes relating to the consol_20

Notes relating to the consolidated statement of financial position - Deferred revenue (Details) € in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018EUR (€)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)	Dec. 31, 2018USD ($)	Jan. 01, 2018USD ($)	Dec. 31, 2017USD ($)
Disclosure of offsetting of financial assets [line items]
Deferred revenue	€ 2,161	€ 8,635	€ 20,136	$ 2,161	$ 10,907	$ 8,635
Upfront Payments Received	8,635	20,137	9,103
AbbVie
Disclosure of offsetting of financial assets [line items]
Deferred revenue	2,200
Upfront Payments Received	2,000	2,000	2,000
LEO Pharma collaboration
Disclosure of offsetting of financial assets [line items]
Deferred revenue	100
Upfront Payments Received	€ 200	€ 200	€ 200

Notes to consolidated stateme_2

Notes to consolidated statement of profit and loss and other comprehensive income (Details) € in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018EUR (€)	Dec. 31, 2018USD ($)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)	Dec. 31, 2018USD ($)	Jan. 01, 2018USD ($)	Dec. 31, 2017USD ($)
Notes to consolidated statement of profit and loss and other comprehensive income
Upfront payments	€ 8,635		€ 20,137	€ 9,103
Milestone payments	11,440		9,677	500
Research and development service fees (FTE)	1,407		6,601	5,110
Total revenue	21,482	$ 21,482	36,415	14,713
Deferred revenue - current	€ 2,161		€ 8,635	€ 20,136	$ 2,161	$ 10,907	$ 8,635

Notes to consolidated stateme_3

Notes to consolidated statement of profit and loss and other comprehensive income - Revenue (Details) € in Thousands, $ in Thousands	1 Months Ended				12 Months Ended
	Aug. 31, 2018USD ($)	Apr. 30, 2016EUR (€)item	Apr. 30, 2016USD ($)item	May 31, 2015EUR (€)	Dec. 31, 2018EUR (€)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)	Dec. 31, 2018USD ($)	Jan. 01, 2018USD ($)	Dec. 31, 2017USD ($)
Notes to unaudited condensed consolidated interim statement of profit and loss and other comprehensive income
Milestone payments					€ 11,440	€ 9,677	€ 500
Research and development service fees (FTE)					1,407	6,601	5,110
Deferred revenue					2,161	€ 8,635	€ 20,136	$ 2,161	$ 10,907	$ 8,635
Shire
Notes to unaudited condensed consolidated interim statement of profit and loss and other comprehensive income
Research and development service fees (FTE)					500
LEO Pharma collaboration
Notes to unaudited condensed consolidated interim statement of profit and loss and other comprehensive income
Milestone payments					600
Research and development service fees (FTE)					400
Deferred revenue					100
Amount of preclinical first milestone payment received					500
Pre-IND payments including upfront payments received				€ 4,500
Staten
Notes to unaudited condensed consolidated interim statement of profit and loss and other comprehensive income
Research and development service fees (FTE)					500
AbbVie
Notes to unaudited condensed consolidated interim statement of profit and loss and other comprehensive income
Milestone payments					10,500
Deferred revenue					2,200
Upfront, non-refundable, non-creditable payment received		€ 35,100	$ 40,000
Number of preclinical milestones achieved | item		2	2
Amount of preclinical first milestone payment received		€ 8,900	$ 10,000		€ 8,300
Amount of preclinical second milestone payment received		€ 8,700
Maximum additional development milestone payments | $	$ 110,000
Maximum additional regulatory milestone payments | $	190,000
Maximum additional commercial milestone payments | $	$ 325,000
Term of additional GARP-related research funding	2 years

Notes to consolidated stateme_4

Notes to consolidated statement of profit and loss and other comprehensive income - Other operating income (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Notes to consolidated statement of profit and loss and other comprehensive income
Grants	€ 1,842	€ 422	€ 779
Research and development incentives	2,151	983	641
Payroll tax rebates	3,756	3,436	1,019
Total	€ 7,749	€ 4,841	€ 2,439

Notes to consolidated stateme_5

Notes to consolidated statement of profit and loss and other comprehensive income - Other operating income - Grants (Details) € in Thousands	Dec. 31, 2018EUR (€)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	€ 2,527
Amount recognized	982
Flanders Innovation & Entrepreneurship-Baekelandt
Other operating income - Grants
Amount granted and approved	2,634
Amount recognized	€ 740

Notes to consolidated stateme_6

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, 2018	Dec. 31, 2017	Dec. 31, 2016
Notes to consolidated statement of profit and loss and other comprehensive income
Research and development incentives	€ 2,151	€ 983	€ 641
Incentive refund period	5 years
Payroll tax rebates	€ 3,756	€ 3,436	€ 1,019

Notes to consolidated stateme_7

Notes to consolidated statement of profit and loss and other comprehensive income - Segment reporting (Details) € in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018EUR (€)	Dec. 31, 2018USD ($)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)
Notes to consolidated statement of profit and loss and other comprehensive income
Revenue from external customers	€ 21,482	$ 21,482	€ 36,415	€ 14,713
Non-current assets	6,015		4,104	3,979
Netherlands
Notes to consolidated statement of profit and loss and other comprehensive income
Revenue from external customers	470		628	548
Germany
Notes to consolidated statement of profit and loss and other comprehensive income
Revenue from external customers				311
Denmark
Notes to consolidated statement of profit and loss and other comprehensive income
Revenue from external customers	1,136		6,240	3,066
Switzerland
Notes to consolidated statement of profit and loss and other comprehensive income
Revenue from external customers	912		2,486	3,315
United States
Notes to consolidated statement of profit and loss and other comprehensive income
Revenue from external customers			1	47
Luxembourg
Notes to consolidated statement of profit and loss and other comprehensive income
Revenue from external customers	€ 18,964		€ 27,060	€ 7,426

Notes to consolidated stateme_8

Notes to consolidated statement of profit and loss and other comprehensive income - Segment reporting - Major clients (Details) € in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018EUR (€)	Dec. 31, 2018USD ($)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)
Segment reporting - Major clients
Revenue	€ 21,482	$ 21,482	€ 36,415	€ 14,713
Largest client
Segment reporting - Major clients
Revenue	19,000		27,100
Second largest client
Segment reporting - Major clients
Revenue	1,100		6,200
Third largest client
Segment reporting - Major clients
Revenue	€ 900		€ 2,500

Notes to consolidated stateme_9

Notes to consolidated statement of profit and loss and other comprehensive income - Research and development expenses (Details) € in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018EUR (€)	Dec. 31, 2018USD ($)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)
Notes to consolidated statement of profit and loss and other comprehensive income
Personnel expenses	€ 26,519		€ 16,473	€ 9,844
External research and development expenses	48,859		27,893	17,562
Materials and consumables	1,464		1,562	1,180
Depreciation and amortisation	494		446	335
Other expenses	6,273		5,366	2,636
Research and development expenses	€ 83,609	$ 83,609	€ 51,740	€ 31,557

Notes to consolidated statem_10

Notes to consolidated statement of profit and loss and other comprehensive income - Selling, general and administrative expenses (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Notes to consolidated statement of profit and loss and other comprehensive income
Personnel expenses	€ 18,292	€ 6,745	€ 3,256
Consulting fees	5,472	3,289	2,563
Supervisory board	1,088	621	446
Office costs	2,619	1,793	746
Total	€ 27,471	€ 12,448	€ 7,011

Notes to consolidated statem_11

Notes to consolidated statement of profit and loss and other comprehensive income - Personnel expenses (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Notes to consolidated statement of profit and loss and other comprehensive income
Short-term employee benefits - Salaries	€ 18,617	€ 12,149	€ 8,527
Short-term employee benefits - Social Security	2,213	1,504	1,027
Post-employment benefits	441	291	175
Termination benefits	96	8	86
Share-based payment	18,527	3,985	2,849
Employer social security contributions stock options	4,918	5,281	436
Total employee benefits expense	€ 44,812	€ 23,218	€ 13,100

Notes to consolidated statem_12

Notes to consolidated statement of profit and loss and other comprehensive income - Personnel expenses FTE (Details) - employee	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Notes to consolidated statement of profit and loss and other comprehensive income
Research and development	74.4	56.8	46.9
General and administrative	29.5	14.7	9.9
Number of FTE	103.9	71.5	56.8

Notes to consolidated statem_13

Notes to consolidated statement of profit and loss and other comprehensive income - Operating leases (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating leases
Operating lease payments recognized as expense	€ 1,500	€ 1,200
Operating lease payments recognized as expense in research and development expenses	1,100	300
Operating lease payments recognized as expense in selling, general and administrative expenses	400	900
Operating lease commitments	€ 3,004	1,526	€ 2,098
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	1,028	915
1-3 years
Operating leases
Operating lease commitments	1,766	465	1,159
3-5 years
Operating leases
Operating lease commitments	€ 210	€ 33	€ 24

Notes to unaudited condensed co

Notes to unaudited condensed consolidated interim statement of profit and loss and other comprehensive income - Financial result and exchange gains/(losses) (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Notes to consolidated statement of profit and loss and other comprehensive income
Interest income on bank deposits	€ 1,371	€ 165	€ 61
Net gains on current financial assets at FVTPL	2,323	210	12
Realized gain on non-current financial assets		875
Financial income	3,694	1,250	73
Realized exchange gains/(losses)	1,355
Unrealized exchange gains/(losses)	10,953	(5,797)	(31)
Exchange gains/(losses)	€ 12,308	€ (5,797)	€ (31)

Notes to consolidated statem_14

Notes to consolidated statement of profit and loss and other comprehensive income - Income tax expense (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Notes to consolidated statement of profit and loss and other comprehensive income
Loss before taxes	€ (65,847)	€ (27,479)	€ (21,374)
Income tax calculated at 25%	(16,462)	(6,870)	(5,344)
Effect of expenses that are not deductible in determining taxable results	(3,934)	(1,141)	(755)
Effect of stock issue expenses that are not deductible in determining taxable results	(3,716)	(5,754)	(462)
Effect of concessions (R&D incentives and grants)	(430)	(453)	(463)
Effect of different tax rates in jurisdictions in which the company operates	(15)	(517)	(180)
Deferred tax asset other than loss carryforwards not recognized	(11,968)	(4,363)
Other	26	9	22
Income tax expense recognized in the consolidated statement of profit and loss	(794)	(597)	0
Netherlands
Notes to consolidated statement of profit and loss and other comprehensive income
Effect of tax losses carried forward not recognized			(5,551)
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	€ (5,511)	(27,413)
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 statem_15

Notes to consolidated statement of profit and loss and other comprehensive income - Income tax expense - Deferred tax assets (Details) - EUR (€) € in Millions	12 Months Ended
	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	€ 117.1
Tax rate applicable	25.00%	25.00%	25.00%
Temporary differences and unused tax losses
Income tax expense - Deferred tax assets
Unrecognized deferred tax assets	€ 29.3	€ 28.4
Netherlands
Income tax expense - Deferred tax assets
Tax rate applicable	25.00%	25.00%	25.00%
Belgium
Income tax expense - Deferred tax assets
Tax rate applicable	25.00%

Notes to consolidated statem_16

Notes to consolidated statement of profit and loss and other comprehensive income - Income tax expense - Restructuring (Details) € in Millions	12 Months Ended
	Dec. 31, 2018EUR (€)
ARGENX BVBA
Notes to consolidated statement of profit and loss and other comprehensive income
Additional tax deductible costs	€ 79.9

Notes to consolidated statem_17

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, 2018	Dec. 31, 2017	Dec. 31, 2016
Notes to consolidated statement of profit and loss and other comprehensive income
Loss of the year	€ (66,641)	€ (28,076)	€ (21,374)
Weighted average number of shares outstanding	33,419,356	24,609,536	18,820,612
Basic and diluted loss per share	€ (1.99)	€ (1.14)	€ (1.14)
Other instruments that could potentially dilute earnings per ordinary share in the future	0

Financial instruments and fin_3

Financial instruments and financial risk management (Details) € in Thousands	Dec. 31, 2017EUR (€)
Amortised cost | Trade and other payables
Disclosure of financial assets [line items]
Carrying amount of liabilities under IAS 39	€ 15,285
Carrying amount of liabilities under IFRS 9	15,285
Available for sale | Financial assets — non-current
Disclosure of financial assets [line items]
Carrying amount of assets under IAS 39	1
FVTPL | Financial assets — non-current
Disclosure of financial assets [line items]
Carrying amount of assets under IFRS 9	1
FVTPL | Financial assets—current
Disclosure of financial assets [line items]
Carrying amount of assets under IAS 39	168,907
Carrying amount of assets under IFRS 9	168,907
Amortised cost | Research and development incentive receivables — non-current member
Disclosure of financial assets [line items]
Carrying amount of assets under IAS 39	3,033
Carrying amount of assets under IFRS 9	3,033
Amortised cost | Restricted cash — non-current
Disclosure of financial assets [line items]
Carrying amount of assets under IAS 39	256
Carrying amount of assets under IFRS 9	256
Amortised cost | Trade and other receivables
Disclosure of financial assets [line items]
Carrying amount of assets under IAS 39	2,842
Carrying amount of assets under IFRS 9	2,842
Amortised cost | Prepaid expenses
Disclosure of financial assets [line items]
Carrying amount of assets under IAS 39	2,338
Carrying amount of assets under IFRS 9	2,338
Amortised cost | Research and development incentive receivables — current
Disclosure of financial assets [line items]
Carrying amount of assets under IAS 39	158
Carrying amount of assets under IFRS 9	158
Amortised cost | Restricted cash — current
Disclosure of financial assets [line items]
Carrying amount of assets under IAS 39	1,692
Carrying amount of assets under IFRS 9	1,692
Amortised cost | Cash and cash equivalents
Disclosure of financial assets [line items]
Carrying amount of assets under IAS 39	190,867
Carrying amount of assets under IFRS 9	€ 190,867

Financial instruments and fin_4

Financial instruments and financial risk management - Fair value (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair value hierarchy
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
Fair value hierarchy
Current financial assets	283,529	€ 168,907	€ 6,831
Assets carried at fair value	283,529	168,907	6,831
Level 3
Fair value hierarchy
Non-current financial assets	1	1	1
Assets carried at fair value	€ 1	€ 1	€ 1

Financial instruments and fin_5

Financial instruments and financial risk management - Capital risk (Details) - EUR (€) € in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financial instruments and financial risk management
Cash and cash equivalents	€ 281,040	€ 190,867	€ 89,897	€ 35,514
Total capital	€ 677,100

Financial instruments and fin_6

Financial instruments and financial risk management - Credit risk (Details) - Credit risk € in Thousands	12 Months Ended
	Dec. 31, 2018EUR (€)
Financial assets past due but not impaired
Disclosure of financial assets that are either past due or impaired [line items]
Financial assets	€ 0
Financial assets impaired
Disclosure of financial assets that are either past due or impaired [line items]
Financial assets	€ 0
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 fin_7

Financial instruments and financial risk management - Interest rate risk (Details) - Interest rate risk - EUR (€) € in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of risk management strategy related to hedge accounting [line items]
Increase decrease in basis points	0.25%
Positive/negative impact	€ 0.3	€ 0.3	€ 0.1

Financial instruments and fin_8

Financial instruments and financial risk management - Foreign exchange risk (Details) - Currency risk - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
USD
Disclosure of risk management strategy related to hedge accounting [line items]
Net exposure to exchange differences of the monetary assets	€ 312,831	€ 147,169	€ 624
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	€ (28,440)	€ (13,380)
Increase (decrease) in financial instrument due to reasonably possible decrease in designated risk component	28,440	13,380
GBP
Disclosure of risk management strategy related to hedge accounting [line items]
Net exposure to exchange differences of the monetary assets	€ 2	€ 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, 2018	Dec. 31, 2017	Dec. 31, 2016
Compensation of key management personnel
Short term employee benefits	€ 4,236	€ 3,126	€ 1,832
Post employment benefits	153	115	125
Sharebased payment	13,363	12,041	2,261
Employer social security contributions stock options	2,792	3,073	436
Total	€ 20,544	€ 18,355	€ 4,654

Other disclosures - Related p_2

Other disclosures - Related party transactions - Executive directors remuneration (Details) - EUR (€)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of transactions between related parties [line items]
Pension contribution	€ 153,000	€ 115,000	€ 125,000
Social security costs	2,792,000	3,073,000	436,000
ESOP	13,363,000	12,041,000	2,261,000
Total	20,544,000	18,355,000	4,654,000
Executive Directors
Disclosure of transactions between related parties [line items]
Base salary	500,000	575,285	489,236
Bonus	284,600	474,919	183,897
Pension contribution	15,102	76,650	96,901
Social security costs	10,011	264,191	146,408
ESOP	3,559,200	7,057,404	1,274,055
Other	33,855	24,580	9,184
Total	4,402,768	8,473,029	2,199,681
Tim Van Hauwermeiren
Disclosure of transactions between related parties [line items]
Base salary	500,000	303,941	253,284
Bonus	284,600	301,635	101,314
Pension contribution	15,102	14,315	11,929
Social security costs	10,011	9,459	10,284
ESOP	3,559,200	2,968,195	488,020
Other	33,855	9,601	9,184
Total	€ 4,402,768	3,607,146	874,015
Eric Castaldi
Disclosure of transactions between related parties [line items]
Base salary		271,344	235,952
Bonus		173,284	82,583
Pension contribution		62,335	84,972
Social security costs		254,732	136,124
ESOP		4,089,209	786,035
Other		14,979
Total		€ 4,865,883	€ 1,325,666

Other disclosures - Related p_3

Other disclosures - Related party transactions - Executive directors ESOP (Details)	Dec. 21, 2018	Dec. 31, 2018EUR (€)EquityInstruments	Dec. 31, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments	Jun. 30, 2018EUR (€)	Jun. 30, 2017EUR (€)	Jun. 30, 2016EUR (€)	May 31, 2016EUR (€)	Dec. 31, 2015EquityInstruments
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding stock options		3,536,651	2,862,216	2,293,636					1,752,926
Exercise price | €		€ 86.32	€ 21.17	€ 14.13	€ 80.82	€ 18.41	€ 11.38	€ 11.47
Exercised		319,671	203,412	140,292
Time period for beneficiaries to choose contractual term (in days)	60 days
Executive Directors
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding stock options		80,000	123,200	137,000
Exercised		40,000	65,380	125,292
Time period for beneficiaries to choose contractual term (in days)	60 days
Tim Van Hauwermeiren | 11.47
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding stock options				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 stock options				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 stock options			80,000
Term			10 years
Exercise price | €			€ 21.17
Tim Van Hauwermeiren | 86.32
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding stock options		80,000
Exercise price | €		€ 86.32
Tim Van Hauwermeiren | 86.32 | Minimum
Disclosure of terms and conditions of share-based payment arrangement [line items]
Term		5 years
Tim Van Hauwermeiren | 86.32 | Maximum
Disclosure of terms and conditions of share-based payment arrangement [line items]
Term		10 years
Tim Van Hauwermeiren | 7.17
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding stock options		336,200	296,200
Exercise price | €		€ 7.17
Exercised		40,000
Eric Castaldi | 11.47
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding stock options				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 stock options				28,200
Term				10 years
Exercise price | €				€ 14.13
Eric Castaldi | 21.17
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding stock options			43,200
Term			10 years
Exercise price | €			€ 21.17

Other disclosures - Related p_4

Other disclosures - Related party transactions - Executive directors ESOP - Rollforward and Vesting (Details)	1 Months Ended							12 Months Ended
	Dec. 31, 2018EUR (€)EquityInstruments	Jun. 30, 2018EUR (€)EquityInstruments	Dec. 31, 2017EUR (€)EquityInstruments	Jun. 30, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments	Jun. 30, 2016EUR (€)EquityInstruments	May 31, 2016EUR (€)EquityInstruments	Dec. 31, 2018EUR (€)EquityInstruments	Dec. 31, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year								2,862,216	2,293,636	1,752,926
Granted	861,575	178,900	653,825	120,536	363,226	60,000	288,950	1,040,475	774,361	712,176
Exercised								(319,671)	(203,412)	(140,292)
Total options at end of year	3,536,651		2,862,216		2,293,636			3,536,651	2,862,216	2,293,636
Exercise price | €	€ 86.32	€ 80.82	€ 21.17	€ 18.41	€ 14.13	€ 11.38	€ 11.47	€ 86.32	€ 21.17	€ 14.13
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								296,200
Granted								80,000
Exercised								(40,000)
Total options at end of year	336,200		296,200					336,200	296,200
Exercise price | €	€ 7.17							€ 7.17
Tim Van Hauwermeiren | 7.17 | Options vested until 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	65,000							65,000
Exercise price | €			€ 7.17						€ 7.17
Tim Van Hauwermeiren | 9.47 | Options vested until 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	20,400							20,400
Exercise price | €			9.47						€ 9.47
Tim Van Hauwermeiren | 9.47 | Options vested 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 until 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 vested 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 until 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 vested 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 beginning of year								80,000
Total options at end of year			80,000						80,000
Exercise price | €			€ 21.17						€ 21.17
Tim Van Hauwermeiren | 21.17 | Options vested 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
Tim Van Hauwermeiren | 86.32
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	80,000							80,000
Exercise price | €	€ 86.32							€ 86.32
Tim Van Hauwermeiren | 86.32 | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	26,667							26,667
Exercise price | €	€ 86.32							€ 86.32
Tim Van Hauwermeiren | 86.32 | Options to vest in 2020
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	26,666							26,666
Exercise price | €	€ 86.32							€ 86.32
Tim Van Hauwermeiren | 86.32 | Options to vest in 2021
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	26,667							26,667
Exercise price | €	€ 86.32							€ 86.32
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 | 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 | 21.17
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year								43,200
Total options at end of year			43,200						43,200
Exercise price | €			€ 21.17						€ 21.17

Other disclosures - Related p_5

Other disclosures - Related party transactions - Executive directors ESOP - Remaining term (Details)	Dec. 31, 2018EquityInstrumentsY	Dec. 31, 2017EquityInstrumentsY	Dec. 31, 2016EquityInstrumentsY	Dec. 31, 2015EquityInstruments
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	3,536,651	2,862,216	2,293,636	1,752,926
Remaining term	7.82	8.03	8.09
Tim Van Hauwermeiren | 5.0 years | Minimum
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Remaining term	5
Tim Van Hauwermeiren | 6.0 years
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	65,000
Remaining term	6
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	30,600
Remaining term	7
Tim Van Hauwermeiren | 7.5 years
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	50,000
Remaining term	7.5
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	8
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	80,000
Remaining term	9
Tim Van Hauwermeiren | 10.0 years | Maximum
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Remaining term	10
Tim Van Hauwermeiren | 5.0 / 10.0 years
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options | EquityInstruments	80,000

Other disclosures - Related p_6

Other disclosures - Related party transactions - Remuneration of non-executive directors (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	€ 20,544	€ 18,355	€ 4,654
Non-executive Directors
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	355,000	320,000	223,930
Peter Verhaeghe
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	77,500	77,500	55,000
David L Lacey
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	50,000	50,000	45,930
Werner Lanthaler
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	55,000	55,000	45,000
Pamela Klein
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	42,500	42,500	35,000
Don Debethizy
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	52,500	52,500	€ 43,000
A.A. Rosenberg
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	42,500	€ 42,500
James M Daly
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total	€ 35,000

Other disclosures - Related p_7

Other disclosures - Related party transactions - Non-executive directors ESOP (Details)	7 Months Ended	11 Months Ended	12 Months Ended
	Oct. 31, 2018EquityInstruments	Nov. 30, 2018EquityInstruments	Dec. 31, 2018EUR (€)EquityInstruments	Dec. 31, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments	Jun. 30, 2018EUR (€)	Jun. 30, 2017EUR (€)	Jun. 30, 2016EUR (€)	May 31, 2016EUR (€)	Dec. 31, 2015EquityInstruments
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			3,536,651	2,862,216	2,293,636					1,752,926
Exercise price | €			€ 86.32	€ 21.17	€ 14.13	€ 80.82	€ 18.41	€ 11.38	€ 11.47
Exercised			319,671	203,412	140,292
Non-executive Directors
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			85,000	15,000	65,000
Exercised			24,972
Werner Lanthaler
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options				29,416
Exercised			24,972
James M Daly
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			25,000
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
Exercised			5,556
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
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
14.13 | A.A. Rosenberg
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			25,000	15,000	15,000
Term					10 years
Exercise price | €					€ 14.13
21.37 | 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 | €				€ 21.37
80.82 | James M Daly
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			15,000
Term			10 years
Exercise price | €			€ 80.82
86.32 | Peter Verhaeghe
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			10,000
Term			10 years
Exercise price | €			€ 86.32
86.32 | 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 | €			€ 86.32
86.32 | Werner Lanthaler
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			10,000
Term			10 years
Exercise price | €			€ 86.32
86.32 | Don Debethizy
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			10,000
Term			10 years
Exercise price | €			€ 86.32
86.32 | Pamela Klein
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			10,000
Term			10 years
Exercise price | €			€ 86.32
86.32 | A.A. Rosenberg
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			10,000
Term			10 years
Exercise price | €			€ 86.32
86.32 | James M Daly
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			10,000
Term			10 years
Exercise price | €			€ 86.32
2.44 | Peter Verhaeghe
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			44,585	34,585
2.44 | David L Lacey
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			54,443	44,443
2.44 | Werner Lanthaler
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			14,444
Exercise price | €			€ 2.44
Exercised	3,566	10,850
7.17 | Werner Lanthaler
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price | €			€ 7.17
Exercised			5,000
11.44 | Pamela Klein
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options			35,000	25,000

Other disclosures - Related p_8

Other disclosures - Related party transactions - Non-executive directors ESOP - Rollforward and vesting (Details)	1 Months Ended							7 Months Ended	11 Months Ended	12 Months Ended
	Dec. 31, 2018EUR (€)EquityInstruments	Jun. 30, 2018EUR (€)EquityInstruments	Dec. 31, 2017EUR (€)EquityInstruments	Jun. 30, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments	Jun. 30, 2016EUR (€)EquityInstruments	May 31, 2016EUR (€)EquityInstruments	Oct. 31, 2018EquityInstruments	Nov. 30, 2018EquityInstruments	Dec. 31, 2018EUR (€)EquityInstruments	Dec. 31, 2017EUR (€)EquityInstruments	Dec. 31, 2016EUR (€)EquityInstruments
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									2,862,216	2,862,216	2,293,636	1,752,926
Number of options granted	861,575	178,900	653,825	120,536	363,226	60,000	288,950			1,040,475	774,361	712,176
Exercised										(319,671)	(203,412)	(140,292)
Total options at end of year	3,536,651		2,862,216		2,293,636					3,536,651	2,862,216	2,293,636
Exercise price | €	€ 86.32	€ 80.82	€ 21.17	€ 18.41	€ 14.13	€ 11.38	€ 11.47			€ 86.32	€ 21.17	€ 14.13
Werner Lanthaler
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									29,416	29,416
Number of options granted										10,000
Exercised										(24,972)
Total options at end of year			29,416								29,416
James M Daly
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options granted										25,000
Total options at end of year	25,000									25,000
2.44 | Peter Verhaeghe
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									34,585	34,585
Number of options granted										10,000
Total options at end of year	44,585		34,585							44,585	34,585
2.44 | Peter Verhaeghe | Options vested until 2017
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									44,443	44,443
Number of options granted										10,000
Total options at end of year	54,443		44,443							54,443	44,443
2.44 | David L Lacey | Options vested until 2017
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]
Exercised								(3,566)	(10,850)
Total options at end of year	14,444									14,444
Exercise price | €	€ 2.44									€ 2.44
2.44 | Werner Lanthaler | Options vested until 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price | €	€ 2.44									€ 2.44
3.95 | Peter Verhaeghe | Options vested until 2017
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 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 | €	€ 7.17									€ 7.17
7.17 | David L Lacey | Options vested until 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	12,800									12,800
Exercise price | €	€ 7.17									€ 7.17
7.17 | Werner Lanthaler
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercised										(5,000)
Exercise price | €	7.17									€ 7.17
7.17 | Werner Lanthaler | Options vested until 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
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 until 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 vested 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 until 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 vested 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
Exercised										(5,556)
Total options at end of year					10,000							10,000
Exercise price | €	11.38				€ 11.38					€ 11.38		€ 11.38
11.38 | Werner Lanthaler | Options vested until 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Exercise price | €	€ 11.38									€ 11.38
11.38 | Werner Lanthaler | Options vested in 2018
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	2,777									2,777
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 | J. Donald deBethizy | Options vested until 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 | J. Donald deBethizy | Options vested 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 | J. Donald 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
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 until 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 vested 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
86.32 | Peter Verhaeghe
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	10,000									10,000
Exercise price | €	€ 86.32									€ 86.32
86.32 | 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	3,333									3,333
Exercise price | €	€ 86.32									€ 86.32
86.32 | Peter Verhaeghe | Options to vest in 2020
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,334									3,334
Exercise price | €	€ 86.32									€ 86.32
86.32 | Peter Verhaeghe | Options to vest in 2021
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333									3,333
Exercise price | €	€ 86.32									€ 86.32
86.32 | David L Lacey
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	10,000									10,000
Exercise price | €	€ 86.32									€ 86.32
86.32 | 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	3,333									3,333
Exercise price | €	€ 86.32									€ 86.32
86.32 | 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	3,334									3,334
Exercise price | €	€ 86.32									€ 86.32
86.32 | David L Lacey | Options to vest in 2021
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333									3,333
Exercise price | €	€ 86.32									€ 86.32
86.32 | Werner Lanthaler
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	10,000									10,000
Exercise price | €	€ 86.32									€ 86.32
86.32 | 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	3,333									3,333
Exercise price | €	€ 86.32									€ 86.32
86.32 | Werner Lanthaler | Options to vest in 2020
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,334									3,334
Exercise price | €	€ 86.32									€ 86.32
86.32 | Werner Lanthaler | Options to vest in 2021
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333									3,333
Exercise price | €	€ 86.32									€ 86.32
86.32 | J. Donald deBethizy | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333									3,333
Exercise price | €	€ 86.32									€ 86.32
86.32 | J. Donald deBethizy | Options to vest in 2020
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,334									3,334
Exercise price | €	€ 86.32									€ 86.32
86.32 | J. Donald deBethizy | Options to vest in 2021
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333									3,333
Exercise price | €	€ 86.32									€ 86.32
86.32 | Pamela Klein
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	10,000									10,000
Exercise price | €	€ 86.32									€ 86.32
86.32 | 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	3,333									3,333
Exercise price | €	€ 86.32									€ 86.32
86.32 | Pamela Klein | Options to vest in 2020
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,334									3,334
Exercise price | €	€ 86.32									€ 86.32
86.32 | Pamela Klein | Options to vest in 2021
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333									3,333
Exercise price | €	€ 86.32									€ 86.32
86.32 | Don Debethizy
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	10,000									10,000
Exercise price | €	€ 86.32									€ 86.32
86.32 | A.A. Rosenberg
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	10,000									10,000
Exercise price | €	€ 86.32									€ 86.32
86.32 | 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	3,333									3,333
Exercise price | €	€ 86.32									€ 86.32
86.32 | A.A. Rosenberg | Options to vest in 2020
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,334									3,334
Exercise price | €	€ 86.32									€ 86.32
86.32 | A.A. Rosenberg | Options to vest in 2021
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333									3,333
Exercise price | €	€ 86.32									€ 86.32
86.32 | James M Daly
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	10,000									10,000
Exercise price | €	€ 86.32									€ 86.32
86.32 | James M Daly | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333									3,333
Exercise price | €	€ 86.32									€ 86.32
86.32 | James M Daly | Options to vest in 2020
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,334									3,334
Exercise price | €	€ 86.32									€ 86.32
86.32 | James M Daly | Options to vest in 2021
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	3,333									3,333
Exercise price | €	€ 86.32									€ 86.32
21.17 | David L Lacey | Options vested 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 | J. Donald deBethizy
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									25,000	25,000
Number of options granted										10,000
Total options at end of year	35,000		25,000							35,000	25,000
11.44 | J. Donald deBethizy | Options vested until 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	12,500									12,500
Exercise price | €	€ 11.44									€ 11.44
11.44 | J. Donald deBethizy | Options vested 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 | Pamela Klein
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at beginning of year									25,000	25,000
Number of options granted										10,000
Total options at end of year	35,000		25,000							35,000	25,000
11.44 | Pamela Klein | Options vested until 2017
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	12,500									12,500
Exercise price | €	€ 11.44									€ 11.44
11.44 | Pamela Klein | Options vested 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	15,000	15,000
Number of options granted										10,000
Total options at end of year	25,000		15,000		15,000					25,000	15,000	15,000
Exercise price | €					€ 14.13							€ 14.13
14.13 | A.A. Rosenberg | Options vested until 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 vested 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
80.82 | James M Daly
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	15,000									15,000
Exercise price | €	€ 80.82									€ 80.82
80.82 | James M Daly | Options to vest in 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	7,500									7,500
Exercise price | €	€ 80.82									€ 80.82
80.82 | James M Daly | 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 | €	€ 80.82									€ 80.82
80.82 | James M Daly | Options to vest in 2021
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total options at end of year	2,500									2,500
Exercise price | €	€ 80.82									€ 80.82

Other disclosures - Related p_9

Other disclosures - Related party transactions - Non-executive directors ESOP - Remaining term (Details)	12 Months Ended
	Dec. 31, 2018EquityInstrumentsY	Dec. 31, 2017EquityInstrumentsY	Dec. 31, 2016EquityInstrumentsY	Dec. 31, 2015EquityInstruments
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	3,536,651	2,862,216	2,293,636	1,752,926
Remaining term | Y	7.82	8.03	8.09
Exercise of Options	319,671	203,412	140,292
Non-executive Directors
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	85,000	15,000	65,000
Exercise of Options	24,972
Werner Lanthaler
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options		29,416
Exercise of Options	24,972
Don Debethizy
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Remaining term | Y	6.5
Pamela Klein
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Remaining term | Y	8
A.A. Rosenberg
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Remaining term | Y	10
James M Daly
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	25,000
1.5 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	1.5
2.0 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	2
4.5 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	4.5
4.5 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	4.5
5.0 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	5
5.0 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	5
6.0 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	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	14,445
Remaining term | Y	6
6.5 years | Werner Lanthaler
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Remaining term | Y	6.5
6.5 years | J. Donald deBethizy
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	15,000
Remaining term | Y	6.5
6.5 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	6.5
7.5 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	7.5
7.5 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	7.5
7.5 years | Werner Lanthaler
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	4,444
Remaining term | Y	7.5
7.5 years | J. Donald deBethizy
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	10,000
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	10,000
Remaining term | Y	7.5
8.0 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	8
9.0 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	9
9.5 years | James M Daly
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	15,000
Remaining term | Y	9.5
10.0 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	10
10.0 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	10
10.0 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	10
10.0 years | J. Donald deBethizy
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	10,000
Remaining term | Y	10
10.0 years | Don Debethizy
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Remaining term | Y	10
10.0 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	10
10.0 years | A.A. Rosenberg
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	10,000
Remaining term | Y	10
10.0 years | James M Daly
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Number of options	10,000
Remaining term | Y	10

Other disclosures - Commitments

Other disclosures - Commitments (Details) € in Thousands	1 Months Ended							12 Months Ended
	Dec. 31, 2018EUR (€)EquityInstruments	Jun. 30, 2018EquityInstruments	Dec. 31, 2017EquityInstruments	Jun. 30, 2017EquityInstruments	Dec. 31, 2016EquityInstruments	Jun. 30, 2016EquityInstruments	May 31, 2016EquityInstruments	Dec. 31, 2018EUR (€)EquityInstruments	Dec. 31, 2017EquityInstruments	Dec. 31, 2016EquityInstruments
Commitments [Line Items]
Number of options granted | EquityInstruments	861,575	178,900	653,825	120,536	363,226	60,000	288,950	1,040,475	774,361	712,176
Commitments to acquire property, plant and equipment	€ 0							€ 0
Commitments to acquire additional intangible assets	0							0
Outstanding commitment	42,200							42,200
ARGX-110
Commitments [Line Items]
Contractual obligations	4,500							4,500
Lonza Sales AG
Commitments [Line Items]
Contractual obligations	€ 25,300							25,300
Contractual period	5 years
Minimum
Commitments [Line Items]
Estimated exposure of stock option	€ 2,900							2,900
Maximum
Commitments [Line Items]
Estimated exposure of stock option	€ 3,500							€ 3,500

Other disclosures - Audit Fees

Other disclosures - Audit Fees (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other disclosures
Audit fees(1)	€ 648	€ 179	€ 85
Audit-related fees	143	724	65
Tax and other services(2)			2
Total	€ 791	€ 903	€ 152

Other disclosures - Overview of

Other disclosures - Overview of Subsidiaries and Subsequent Events (Details) € / shares in Units, $ / shares in Units, € in Thousands, $ in Millions

Mar. 14, 2019EUR (€)

Feb. 04, 2019USD ($)

Jan. 18, 2019USD ($)€ / shares

Jan. 18, 2019USD ($)shares

Sep. 18, 2018€ / sharesshares

Dec. 14, 2017$ / sharesshares

Dec. 13, 2017shares

May 19, 2017shares

May 17, 2017$ / sharesshares

Jun. 01, 2016shares

Jan. 20, 2016shares

Jun. 30, 2016shares

Jan. 31, 2016shares

Dec. 31, 2018EUR (€)subsidiary

Dec. 31, 2017EUR (€)shares

Mar. 20, 2019USD ($)m²

Jan. 02, 2019EUR (€)m²

Dec. 31, 2016EUR (€)

Subsequent Events

Future lease commitments | €

€ 3,004

€ 1,526

€ 2,098

New shares issued for private placement, initial public offering, public offering and underwriters' over-allotment option | shares

3,475,000

666,000

4,440,000

879,750

5,865,000

1,480,420

2,703,000

1,480,420

5,106,000

Share price | (per share)

€ 86.50

$ 52

$ 17

Netherlands

Overview of consolidation scope

Participation ( as a percent)

100.00%

Belgium | Subsequent Event | New lease agreement

Subsequent Events

Area of lease | m²

560

Future lease commitments | €

€ 700

United States | Subsequent Event | New lease agreement

Subsequent Events

Area of lease | m²

580

Future lease commitments

$ 2.2

ARGENX BVBA | Belgium

Overview of consolidation scope

Number of subsidiaries | subsidiary

1

Participation ( as a percent)

100.00%

ARGENX US INC | United States

Overview of consolidation scope

Number of subsidiaries | subsidiary

1

Participation ( as a percent)

100.00%

Private placement (Sunflower)

Subsequent Events

New shares issued for private placement, initial public offering, public offering and underwriters' over-allotment option | shares

2,703,000

Private placement (Sunflower) | Subsequent Event | Share transaction

Subsequent Events

New shares issued for private placement, initial public offering, public offering and underwriters' over-allotment option | shares

1,766,899

Share price | € / shares

€ 100.02

Janssen | Subsequent Event | Collaboration agreement transaction

Subsequent Events

Upfront payment received

$ 300

Development, regulatory and sales milestones receivable

€ 1,300

$ 1,300

Proportionate share of economics

50/50

Halozyme | Subsequent Event | Collaboration agreement transaction

Subsequent Events

Upfront payment

$ 30

Additional payment for each target

10

Halozyme | Subsequent Event | Maximum | Collaboration agreement transaction

Subsequent Events

Future milestone payments

$ 160

AbbVie | Subsequent Event | Collaboration agreement transaction

Subsequent Events

Development milestone payment received | €

€ 30,000