Merus (MRUS) 20-F 30 Apr 18 2017 FY Annual report (foreign) Financial data

Document and Entity Information

Document and Entity Information	12 Months Ended
	Dec. 31, 2017shares
Document - Document and Entity Information [Abstract]
Document Type	20-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	MRUS
Entity Registrant Name	Merus N.V.
Entity Central Index Key	1,651,311
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding	19,429,848

Consolidated Statement of Finan

Consolidated Statement of Financial Position - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016
Non-current assets
Property, plant and equipment	€ 1,168	€ 648
Intangible assets	312	374
Restricted cash		167
Non-current investments	7,060
Other assets	129	109
Non-current assets	8,669	1,298
Current assets
Financial asset		11,847
Trade and other receivables	4,413	2,248
Current investments	34,043
Cash and cash equivalents	149,678	56,917
Current assets	188,134	71,012
Total assets	196,803	72,310
Shareholders' equity
Issued and paid-in capital	1,749	1,448
Share premium account	213,618	139,878
Accumulated loss	(167,480)	(107,295)
Total equity	47,887	34,031
Non-current liabilities
Borrowings		319
Deferred revenue	130,195	30,206
Current liabilities
Borrowings		167
Trade payables	2,855	2,298
Taxes and social security liabilities	243	29
Deferred revenue	6,996	1,610
Other liabilities and accruals	8,627	3,650
Current liabilities	18,721	7,754
Total liabilities	148,916	38,279
Total equity and liabilities	€ 196,803	€ 72,310

Consolidated Statement of Profi

Consolidated Statement of Profit or Loss and Comprehensive Loss - EUR (€) € in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating expenses from railroad and related business [abstract]
Revenue		€ 13,600	€ 2,719	€ 1,977
Revenue		13,600	2,719	1,977
Research and development costs		(34,125)	(18,424)	(16,181)
Management and administration costs		(13,697)	(4,258)	(768)
Other expenses		(9,395)	(7,709)	(8,067)
Total operating expenses		(57,217)	(30,391)	(25,016)
Operating result		(43,617)	(27,672)	(23,039)
Finance income		1,112	88	50
Finance expenses		(30,335)	(19,644)	(195)
Total		(29,223)	(19,556)	(145)
Result before tax		(72,840)	(47,228)	(23,184)
Income tax expense		(249)
Result after taxation		(73,089)	(47,228)	(23,184)
Exchange differences from translation of foreign operations		89	8
Other comprehensive income		89	8
Total comprehensive loss for the year		€ (73,000)	€ (47,220)	€ (23,184)
Basic (and diluted) loss per share	[1],[2]	€ (3.80)	€ (3.57)	€ (3.95)
[1]	For the periods included in these financial statements, the share options are not included in the diluted loss per share calculation as the Company was loss-making in all these periods. Due to the anti-dilutive nature of the outstanding options, basic and diluted loss per share is equal.
[2]	The basic (and diluted) loss per share is adjusted for the 2015 period based on the reverse share split with reference to note 14 regarding the capital reorganization.

Consolidated Statement of Chang

Consolidated Statement of Changes in Equity - EUR (€) € in Thousands	Total	Issued capital [member]Common share capital [member]	Issued capital [member]Class A preference share capital [member]	Issued capital [member]Class B preference share capital [member]	Issued capital [member]Class C preference share capital [member]	Share premium [member]Common share premium [member]	Share premium [member]Class A preference share premium [member]	Share premium [member]Class B preference share premium [member]	Share premium [member]Class C preference share premium [member]	Accumulated loss [member]
Beginning balance at Dec. 31, 2014	€ (3,559)	€ 30	€ 21	€ 231		€ 1,564	€ 1,334	€ 34,026		€ (40,765)
Result	(23,184)									(23,184)
Total comprehensive loss	(23,184)									(23,184)
Transactions with owners of the Company:
Issuance of shares (net)	54,478			120	€ 373			4,880	€ 49,105
Equity settled shared-based payments	567									567
Total contributions by and distributions to owners of the Company	55,045			120	373			4,880	49,105	567
Ending balance at Dec. 31, 2015	(28,302)	30	21	351	373	1,564	1,334	38,906	49,105	(63,382)
Result	(47,228)									(47,228)
Other comprehensive income	8									8
Total comprehensive loss	(47,220)									(47,220)
Transactions with owners of the Company:
Issuance of shares (net)	51,151	673				50,478
IPO expenses	(1,509)					(1,509)
Conversion of preference shares		745	(21)	(351)	(373)	89,345	(1,334)	(38,906)	(49,105)
Equity settled shared-based payments	3,307									3,307
Total contributions by and distributions to owners of the Company	52,949	1,418	€ (21)	€ (351)	€ (373)	138,314	€ (1,334)	€ (38,906)	€ (49,105)	3,307
Ending balance at Dec. 31, 2016	34,031	1,448				139,878				(107,295)
Result	(73,089)									(73,089)
Other comprehensive income	89									89
Total comprehensive loss	(73,000)									(73,000)
Transactions with owners of the Company:
Issuance of shares (net)	74,041	301				73,740
Equity settled shared-based payments	12,815									12,815
Total contributions by and distributions to owners of the Company	86,856	301				73,740				12,815
Ending balance at Dec. 31, 2017	€ 47,887	€ 1,749				€ 213,618				€ (167,480)

Consolidated Statement of Cash

Consolidated Statement of Cash flows € in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)	Dec. 31, 2015EUR (€)
Cash flows from operating activities
Result after taxation	€ (73,089)	€ (47,228)	€ (23,184)
Adjustments for:
Change in fair value derivative	10,667	19,213
Unrealized foreign exchange results	15,767	365
Depreciation and amortization	318	234	193
Share-based payment expenses	12,815	3,307	567
Net finance (income) expenses	(1,040)	(33)	145
Cash flows from (used in) operations before changes in working capital	(34,562)	(24,142)	(22,279)
Changes in working capital:
Trade and other receivables	(1,837)	(1,256)	(816)
Other assets	(20)	(109)
Trade payables	505	(121)	10
Other liabilities and accruals	4,977	286	461
Deferred revenue	(6,618)	(223)	(223)
Tax and social security liabilities	214	(113)	11
Cash used in operating activities	(37,341)	(25,678)	(22,836)
Interest paid	(29)	(55)	(195)
Taxes paid	(43)
Net cash used in operating activities	(37,413)	(25,733)	(23,031)
Cash flows from investing activities
Purchases of investments	(41,830)
Acquisition of property, plant and equipment	(724)	(496)	(103)
Interest received	929	88	50
Net cash used in investing activities	(41,625)	(408)	(53)
Cash flows from financing activities
Proceeds from issuing shares, net of issuance costs	74,738	50,547	46,478
Financing costs	(190)
Prepaid share issuance costs		(230)
Proceeds from collaboration agreement	111,993
Proceeds from borrowings			8,000
Repayment of borrowings	(486)	(167)	(166)
Changes in restricted cash	167	51	55
Net cash from financing activities	186,222	50,201	54,367
Net increase in cash and cash equivalents	107,184	24,060	31,283
Effects of exchange rate changes on cash and cash equivalents	(14,423)	6
Cash and cash equivalents as at January 1	56,917	32,851	1,568
Cash and cash equivalents as at December 31	149,678	€ 56,917	€ 32,851
Supplemental disclosure of non-cash activities:
Changes in accrued capital expenditures	€ 52

General Information

General Information	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
General Information	1. General Information Merus N.V. is a clinical-stage immuno-oncology company developing innovative bispecific antibody therapeutics, headquartered in Utrecht, the Netherlands. Merus US, Inc. is a wholly-owned subsidiary of Merus N.V. located in Boston, Massachusetts, United States. These audited consolidated financial statements as at and for the twelve-month period ended December 31, 2017 comprise Merus N.V. and Merus US, Inc. (collectively, the “Company”). Merus N.V. was incorporated in the Netherlands, with its statutory seat in Utrecht. In connection with becoming a listed company on the Nasdaq Global Market (“Nasdaq”), on May 19, 2016, Merus N.V.’s legal structure under Dutch law was changed from a private company with limited liability (in Dutch: besloten vennootschap met beperkte aansprakelijkheid naamloze vennootschap Nature of Business The Company expects to incur significant expenses and operating losses for the foreseeable future as its bispecific antibody candidates advance from discovery through preclinical development and into clinical trials, and it seeks regulatory approval and pursues commercialization of any approved bispecific antibody candidate. As a result, the Company may need additional financing to support its continuing operations. Until the Company can generate significant revenue from product sales, if ever, the Company expects to finance its operations through public equity or debt financings or other sources, which may include collaborations and business development opportunities with third parties. Adequate additional financing may not be available to the Company on acceptable terms, or at all. The Company’s inability to raise capital as and when needed would have a negative impact on the financial condition and ability to pursue its business strategy. The Company will need to generate significant revenue to achieve profitability and may never do so. Based on the Company’s current operating plan, it expects its existing cash balances, including proceeds received from the private placement offering that closed in February 2018, to last through the end of 2020. For this assessment, we have taken into consideration our existing cash and cash equivalents of €149.7 million and investments of €41.1 million at December 31, 2017, together with the $55.8 million of proceeds received from our private placement offering that closed in February 2018. (see Note 24).

Basis of Preparation

Basis of Preparation	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Basis of Preparation	2. Basis of Preparation These consolidated financial statements have been authorized for issuance on April 30, 2018. Certain amounts were reclassified in the prior years consolidated financial statements for consistency with the current year presentation. These changes in classification do not materially affect the previously reported Consolidated Statement of Financial Position, Consolidated Statement of Profit or Loss and Comprehensive Loss or Consolidated Statements of Cash Flows for any period. Statement of Compliance These consolidated financial statements (“the financial statements”) have been prepared in accordance with International Financial Reporting Standards (“IFRS”) as issued by the International Accounting Standards Board. The financial statements have been prepared under the historical cost convention unless otherwise stated in the below accounting policies. Initial Public Offering On May 6, 2016, the general meeting of our shareholders resolved to approve and effect a capital reorganization, based on a reverse share split. The effect of the reverse share split was a 1-for-1.8 per-share On May 24, 2016, the Company closed the initial public offering of 5,500,000 of its common shares and, on May 26, 2016, of an additional 639,926 of its common shares, at a price to the public of US $10 per share (the “IPO”). Net proceeds to the Company after deducting underwriting discounts and commissions and offering expenses were $53.3 million. On May 19, 2016, the Company’s common shares were listed on the Nasdaq and all of the Company’s preferred shares converted into common shares. Follow-on On June 1, 2017, the Company filed with the U.S. Securities and Exchange Commission a registration statement on Form F-3 333-218432) “F-3 F-3 F-3 On February 13, 2018, the Company entered into a Securities Purchase Agreement (the “Purchase Agreement”) with the purchasers named therein (the “Investors”). Pursuant to the Purchase Agreement, the Company agreed to sell an aggregate of 3,099,997 of its common shares, nominal value €0.09 per share, to the Investors for aggregate gross proceeds of approximately $55.8 million, at a purchase price equal to $18.00 per share (the “Private Placement”). The Purchase Agreement contains customary representations and warranties from the Company and the Investors and customary closing conditions. The closing of the Private Placement occurred on February 15, 2018. Functional and Presentation Currency The financial statements are presented in euros, which is the Company’s functional and presentation currency. All amounts are rounded to the nearest thousands of euros, except as otherwise indicated. Use of Estimates, Judgements and Assumptions In the application of the Company’s accounting policies, management is required to make judgments, estimates and assumptions that affect the reported amounts of assets, liabilities, income and expenses 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. Estimates and underlying assumptions are reviewed on an ongoing basis. Revisions to accounting estimates are recognized prospectively. The following are the critical judgments and assumptions that management has made in the process of applying the Company’s accounting policies and that have the most significant effect on the amounts recognized in the financial statements. Capitalization of Development Costs The criteria for capitalization of development costs have been considered by management and determined not to have been met in the twelve month period ended December 31, 2017. Therefore, all development expenditures relating to internally generated intangible assets in the twelve month period ended December 31, 2017 were expensed as incurred. Income Taxes The criteria for the recognition of unused tax losses are disclosed in Note 3 “Significant accounting policies”. As of December 31, 2017, deferred tax assets have not been recognized in respect of tax losses, because the Company has no history of generating taxable profits and therefore, it is not probable that sufficient taxable profit will be available against which the tax losses can be utilized. The amount of the unrecognized tax losses is disclosed in Note 8. Deferred Revenue The Company maintains certain research, collaboration and license agreements with ONO Pharmaceuticals Co., Ltd (“ONO”) and Incyte under which the Company has received upfront non-refundable Equity Settled Share-Based Payments Share options granted to employees, consultants and directors are measured at the grant date fair value of the equity instruments granted. The grant date fair value is determined through the use of an option-pricing model considering the following variables: (a) the exercise price of the option; (b) the expected life of the option; (c) the current value of the underlying shares; (d) the expected volatility of the share price; (e) the dividends expected on the shares; and (f) the risk-free interest rate for the life of the option. Prior to the Company’s IPO, the estimated the fair value of each share option granted was determined utilizing the Black-Scholes option-pricing model. For the Company’s share option plans subsequent to its IPO, management’s judgment was that the Hull & White option pricing model is the most appropriate method for determining the fair value of the Company’s share options considering the terms and conditions attached to the grants made and reflective of exercise behavior. Since the Company was not listed on a national securities exchange until May 19, 2016, there was no published share price information available until May 19, 2016. Consequently, the Company estimated the fair value of its shares and the expected volatility of that share value for the period up to May 19, 2016. As the Company’s shares have not been publicly traded for a sufficient amount of time, the expected volatility was set by considering the historic share price volatility of a set of peer companies. For pre-IPO post-IPO The result of the share option valuations and the related compensation expense that is recognized for the respective vesting periods during which services are received, is dependent on the model and input parameters used. Even though management considers the fair values reasonable and defensible based on the methodologies applied and the information available, others might derive a different fair value for the Company’s share options. These assumptions and estimates are further discussed in Note 14 to the financial statements.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Significant Accounting Policies	3. Significant Accounting Policies The accounting policies set out below have been consistently applied to all periods presented in these financial statements. Income and expenses are accounted for on an accrual basis. Profit is only included when realized at the statement of financial position date. Losses originating before the end of the financial year are taken into account if they have become known before preparation of the financial statements. Basis of consolidation (i) Subsidiaries Subsidiaries are entities controlled by the Company, consisting of Merus N.V. and its wholly owned subsidiary Merus US, Inc. The Company controls an entity when it is exposed to, or has rights to, variable returns from its involvement with the entity and has the ability to affect those returns through its power over the entity. The financial statements of subsidiaries are included in the consolidated financial statements from the date on which control commences until the date on which control ceases. (ii) Loss of control When the Company loses control over a subsidiary, it derecognizes the assets and liabilities of the subsidiary, and any non-controlling (iii) Transactions eliminated on consolidation Intra-company balances and transactions, and any unrealized income and expenses arising from intra-company transactions, are eliminated. Unrealized gains arising from transactions with equity-accounted investees are eliminated against the investment to the extent of the Company’s interest in the investee. Unrealized losses are eliminated in the same way as unrealized gains, but only to the extent that there is no evidence of impairment. Foreign Currency Transactions Foreign currency transactions are translated using the exchange rates at the dates of the transactions. Foreign exchange gains and losses resulting from the settlement of such transactions and from the translation of monetary assets and liabilities denominated in foreign currencies at the exchange rate at the reporting date are generally recognized in the statement of profit or loss and comprehensive loss as a component of finance costs. The results and financial position of foreign operations that have a functional currency different from the presentation currency are translated into the presentation currency as follows: • assets and liabilities for each balance sheet presented are translated at the closing rate at the date of that balance sheet; • income and expenses for each statement of profit or loss and comprehensive income or loss are translated at average exchange rates (unless this is not a reasonable approximation of the cumulative effect of the rates prevailing on the transaction dates, in which case income and expenses are translated at the exchange rates at the dates of the transactions); and • all resulting exchange differences are recognized in other comprehensive income. Property, Plant and Equipment Property, plant and equipment are measured at cost less accumulated depreciation and accumulated impairment losses (if any). Cost includes expenditure that is directly attributable to the acquisition of the items. Depreciation of property, plant and equipment is recognized in the consolidated statement of profit and loss and comprehensive loss on a straight-line basis over estimated useful lives of generally five years, taking residual value into account. If significant parts of an item of property, plant and equipment have different useful lives, they are accounted for as separate items (major components) of property, plant and equipment. Subsequent expenditure is capitalized only when the expenditure will increase the future economic benefit of the asset. All other expenditures are expensed in the profit or loss and comprehensive loss. Depreciation rates are based on the following estimated economic useful lives of the tangible fixed assets concerned: • Plant and equipment: 5 years • Other fixed assets: 5 years Intangible Assets Intangible assets are identifiable non-monetary The useful lives of intangible assets are assessed to be finite and amortized over the useful economic life and assessed for impairment whenever there is an indication that the intangible asset may be impaired. Amortization begins when the asset is available for use. Patents Patents acquired separately by the Company are reported at cost less accumulated amortization and accumulated impairment losses. Amortization is recognized in the consolidated statement of profit and loss and comprehensive loss on a straight-line basis over the shorter of their estimated economic or legal lives. The estimated useful life and amortization method are reviewed at the end of each annual reporting period, with the effect of any changes in estimates being accounted for on a prospective basis. Research and Development The Company incurs research and development expenses related to its clinical trials and preclinical drug development programs. Development expenses are defined as expenses incurred to achieve technical and commercial feasibility. Expenditure on research activities is recognized as an expense in the period in which it is incurred. Development is capitalized 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. Financial Instruments The Company classifies non-derivative non-derivative Non-Derivative The Company initially recognizes receivables and investments at fair value on the date when they are originated. Subsequent to initial recognition, they are measured at amortized cost using the effective interest rate method. All other financial assets and financial liabilities are initially recognized on the trade date. The Company derecognizes a financial asset when the contractual rights to the cash flows from the asset expire, or it transfers the rights to receive the contractual cash flows in a transaction in which substantially all the risks and rewards of ownership of the financial asset are transferred, or it neither transfers nor retains substantially all of the risks and rewards of ownership and does not retain control over the transferred asset. Any interest in such derecognized financial assets that is created or retained by the Company is recognized as a separate asset or liability. The Company derecognizes a financial liability when its contractual obligations are settled or cancelled, or expire. Financial assets and financial liabilities are offset and the net amount presented in the statement of financial position when, and only when, the Company has a legal right to offset the amounts and intends either to settle them on a net basis or to realize the asset and settle the liability simultaneously. Investments Investments are classified as held-to-maturity held-to-maturity Receivables These assets are initially recognized at fair value plus any directly attributable transaction costs. Derivative Financial Assets and Liabilities Derivative financial instruments are initially recognized at fair value on the date on which a derivative contract is entered into and are subsequently remeasured at fair value with net changes in fair value presented as finance expenses (negative net changes in fair value) or finance income (positive net changes in fair value) in the consolidated statement of profit or loss and comprehensive loss. Derivatives are carried as financial assets when the fair value is positive and as financial liabilities when the fair value is negative. Derivatives embedded in host contracts are accounted for as separate derivatives and recorded at fair value if their economic characteristics and risks are not closely related to those of the host contracts and the host contracts are not held for trading or designated at fair value through profit or loss. These embedded derivatives are measured at fair value with changes in fair value recognized in profit or loss. Reassessment only occurs if there is either a change in the terms of the contract that significantly modifies the cash flows that would otherwise be required or a reclassification of a financial asset out of the fair value through profit or loss category. Non-Derivative Non-derivative Cash and Cash Equivalents For the purpose of presentation in the statement of cash flows as well as the statement of financial position, cash and cash equivalents includes deposits held with financial institutions with original maturities of less than three months. Treatment of equity issuance costs Costs related to the issuance of new shares have been accounted for as follows: • Incremental costs that are directly attributable to issuing new shares are included as prepaid expenses and are deducted from equity on the date the Company closes its new share transactions (net of any income tax benefit). Such as, for example, the date of the closing of its IPO or the share subscription agreement with Incyte; • Incremental costs directly associated with a probable, successful future offering of equity instruments are also deferred and deducted from equity when the new shares are issued. During 2017, the Company expensed €0.2 million of prepaid share issuance costs related to a potential future issuance of shares under the Company’s F-3 • Costs that relate to listing on Nasdaq, or other new share transaction costs that are otherwise not incremental and directly attributable to issuing new shares, are recorded as an expense in the consolidated statement of profit or loss and comprehensive loss; and • Costs that relate to both share issuance and listing are allocated between those functions on a rational and consistent basis. Provisions A provision is recognized if the following applies: • the company has a legal or constructive obligation, arising from a past event; • the amount can be estimated reliably; and • it is probable that an outflow of resources embodying economic benefits will be required to settle the obligation. If all or part of the payments that are necessary to settle a provision are virtually certain to be fully or partially compensated by a third party upon settlement of the provision, then the compensation amount is presented separately as an asset. Provisions are determined by discounting the expected future cash flows at a pre-tax Impairment Financial Assets Measured at Amortized Cost The Company considers evidence of impairment for these assets at both an individual asset and a collective level. All individually significant assets are individually assessed for impairment. Those found not to be impaired are then collectively assessed for any impairment that has been incurred but not yet individually identified. Assets that are not individually significant are collectively assessed for impairment. Collective assessment is carried out by grouping together assets with similar risk characteristics. In assessing collective impairment, the Company uses historical information on the timing of recoveries and the amount of loss incurred, and makes an adjustment if current economic and credit conditions are such that the actual losses are likely to be greater or lesser than suggested by historical trends. An impairment loss is calculated as the difference between an asset’s carrying amount and the present value of the estimated future cash flows discounted at the asset’s original effective interest rate. Losses are recognized in the consolidated statement of profit or loss and comprehensive income and reflected in an allowance account. When the Company considers that there are no realistic prospects of recovery of the asset, the relevant amounts are written off. If the amount of impairment loss subsequently decreases and the decrease can be related objectively to an event occurring after the impairment was recognized, then the previously recognized impairment loss is reversed through profit or loss. Non-Financial At each reporting date, the Company reviews the carrying amounts of its non-financial For impairment testing, assets are grouped together into the smallest group of assets that generates cash inflows from continuing use that are largely independent of the cash inflows of other assets or cash generating units (“CGU”). The recoverable amount of an asset or CGU is the greater of its value in use and its fair value less costs to sell. Value in use is based on the estimated future cash flows, discounted to their present value using a pre-tax An impairment loss is recognized if the carrying amount of an asset or CGU exceeds its recoverable amount. Impairment losses are recognized in profit or loss. They are allocated first to reduce the carrying amount of any goodwill allocated to the CGU, and then to reduce the carrying amounts of the other assets in the CGU on a pro rata basis. An impairment loss is reversed only to the extent that the asset’s carrying amount does not exceed the carrying amount that would have been determined, net of depreciation or amortization, if no impairment loss had been recognized. Revenue Recognition Revenue is recognized to the extent that it is probable that the economic benefits will flow to the Company and the revenue can be reliably measured. Up-front The Company maintains research and license agreements with ONO and Incyte. In connection with these arrangements, the Company received upfront fees, which relate to the integrated package of deliverables under the contract (one single performance obligation) and are initially recorded in deferred revenue. The applicable period over which to recognize the upfront payment is a significant judgment. Up-front non-refundable re-assessed Collaboration Income Collaboration income, which is typically related to reimbursements from collaborators for the Company’s performance of research and development services under the respective agreements, is recognized on the basis of labor hours valued at a contractually agreed rate. Collaboration income includes reimbursements for related out-of-pocket Government Grants The Company receives certain government and regional grants, which support its research efforts in defined projects, and include contributions towards the cost of research and development. When there is reasonable assurance that the Company will comply with the conditions attached to a received grant, and when there is reasonable assurance that the grant will be received, government grants are recognized as revenue on a gross basis in the consolidated statement of profit or loss and comprehensive loss on a systematic basis over the periods in which the entity recognizes expenses for the related costs for which the grants are intended to compensate. In the case of grants related to assets, the received grant will be deducted from the carrying amount of the asset. Research and development expenses Research and development expenses represent costs which primarily include (i.) payroll and related costs (including share-based payment expenses) associated with research and development personnel, (ii.) costs related to clinical trials and preclinical testing of the Company’s technologies under development, (iii.) costs to develop product candidates, including raw materials and supplies, product testing, depreciation, and facility related expenses, (iv.) expenses for research services provided by universities and contract laboratories, and (v.) other research and development expenses. Research and development expenses are recognized in the consolidated statement of profit or loss and comprehensive loss as incurred when these expenditures relate to the Company’s research and development services and have no alternative future uses. The Company has entered into various research and development contracts with research institutions and other companies. These agreements are generally cancelable. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates may be made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs. WBSO The WBSO ( afdrachtvermindering speur- en ontwikkelingswerk Employee Benefits Short-term Employee Benefits Short-term employee benefits are expensed as the related service is provided. A liability is recognized for the amount expected to be paid if the Company has a present legal or constructive obligation to pay this amount as a result of past service provided by the employee and the obligation can be estimated reliably. Share-Based Payment Transactions The grant-date fair value of equity-settled share-based payment awards granted to employees including grants of employee options, restricted share units, and modifications to existing instruments, is recognized as an expense, net of an estimated forfeiture rate, with a corresponding increase in equity (accumulated loss), over the vesting period of the awards. Forfeitures of employee options are recognized as they occur. Service conditions and non-market non-market non-market non-vesting true-up Post-Employment Benefit Plans The Company contributes to a post-employment benefit plan that entitles directors, executive officers and other staff members to retire at the age of 67 and receive annual payments based upon the average salary earned during the service period. The Company has insured the liabilities from the post-employment benefit plan with an insurance company and has no other obligation than to pay the annual insurance premiums to the insurance company. The annual pension payments are conditional; the Company will have no further obligation (legal or constructive) to pay further amounts if the insurance fund has insufficient assets to pay all employee benefits relating to current and prior service. Based on its characteristics the Company’s post-employment benefit plan is classified as a defined contribution plan. Obligations for contributions to defined contribution plans are expensed as the related service is provided. Prepaid contributions are recognized as an asset. Leases Determining whether an Arrangement Contains a Lease At inception of an arrangement, the Company determines whether such an arrangement is or contains a lease. At inception or on reassessment of the arrangement, the Company separates payments and other consideration required by such an arrangement into those for the lease and those for other elements on the basis of their relative fair values. If the Company concludes for a finance lease that it is impracticable to separate the payments reliably, then an asset and a liability are recognized at an amount equal to the fair value of the underlying asset. Subsequently the liability is reduced as payments are made and an imputed finance cost on the liability is recognized using the Company’s incremental borrowing rate. Leased Assets Assets held by the Company under leases that transfer to the Company substantially all of the risks and rewards of ownership are classified as finance leases. The leased assets are measured initially at an amount equal to the lower of their fair value and the present value of the minimum lease payments. Subsequent to initial recognition, the assets are accounted for in accordance with the accounting policy applicable to that asset. Assets held under other leases are classified as operating leases and are not recognized in the Company’s statement of financial position. Lease Payments Payments made under operating leases are recognized in the consolidated statement of profit or loss and comprehensive loss on a straight-line basis over the term of the lease. Lease incentives received are recognized as an integral part of the total lease expense, over the term of the lease. Minimum lease payments made under finance leases are apportioned between the finance expense and the reduction of the outstanding liability. The finance expense is allocated to each period during the lease term so as to produce a constant periodic rate of interest on the remaining balance of the liability. Finance Income and Finance Expenses The Company’s finance income and finance expenses include: • interest and related income; • interest expense and changes in fair value of the forward contract (derivative); • financing costs; and • the foreign currency gain or loss on financial assets and financial liabilities. Interest income or expense is recognized using the effective interest method. Income Tax Income tax expense comprises current and deferred tax. It is recognized in the statement of profit or loss and comprehensive loss except to the extent that it relates to a business combination, or items recognized directly in equity or in other comprehensive income. Current tax comprises the expected tax payable or receivable on the taxable income or loss for the year and any adjustment to tax payable or receivable in respect of previous years. It is measured using tax rates enacted or substantively enacted at the reporting date. Current tax also includes any tax arising from dividends. Current tax assets and liabilities are offset only if certain criteria are met. Deferred tax is recognized in respect of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for taxation purposes. Deferred tax is not recognized for: • temporary differences on the initial recognition of assets or liabilities in a transaction that is not a business combination and that affects neither accounting nor taxable profit or loss; • temporary differences related to investments in subsidiaries, associates and joint arrangements to the extent that the group is able to control the timing of the reversal of the temporary differences and it is probable that they will not reverse in the foreseeable future; and • taxable temporary differences arising on the initial recognition of goodwill. Deferred tax assets are recognized for unused tax losses, unused tax credits and deductible temporary differences to the extent that it is probable that future taxable profits will be available against which they can be used. Deferred tax assets are reviewed at each reporting date and are reduced to the extent that it is no longer probable that the related tax benefit will be realized; such reductions are reversed when the probability of future taxable profits improves. Unrecognized deferred tax assets are reassessed at each reporting date and recognized to the extent that it has become probable that future taxable profits will be available against which they can be utilized. Deferred tax is measured at the tax rates that are expected to be applied to temporary differences when they reverse, using tax rates enacted or substantively enacted at the reporting date. The measurement of deferred tax reflects the tax consequences that would follow from the manner in which the Company expects, at the reporting date, to recover or settle the carrying amount of its assets and liabilities. Deferred tax assets and liabilities are offset only if certain criteria are met.

New Standards and Interpretatio

New Standards and Interpretations Not Yet Adopted	12 Months Ended
	Dec. 31, 2017
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New Standards and Interpretations Not Yet Adopted	4. New Standards and Interpretations Not Yet Adopted A number of new standards, amendments to standards and interpretations are effective for annual periods beginning after January 1, 2018, and have not been applied in preparing these financial statements. Those which may be relevant to the Company are set out below. The Company does not plan to adopt these standards early. IFRS 9 Financial Instruments IFRS 9, published in July 2014, replaces the existing guidance in IAS 39 Financial Instruments: Recognition and Measurement. IFRS 9 includes contains a new classification and measurement approach for financial assets that reflects the business model in which assets are managed and their cash flow characteristics. IFRS 9 contains three principal classification categories for financial assets: measured at amortized cost, measured at fair value through other comprehensive income and measured at fair value through profit or loss. The standard eliminates the existing IAS 39 categories of held to maturity, loans and receivables and available for sale. In addition, the revised guidance on the classification and measurement of financial instruments includes a new expected credit loss model for calculating impairment on financial assets and the new general hedge accounting requirements. Finally, IFRS 9 carries forward the guidance on recognition and derecognition of financial instruments from IAS 39. IFRS 9 is effective for annual reporting periods beginning on or after January 1, 2018, with early adoption permitted. Based on its assessment, the Company believes that adoption of IFRS 9’s new classification requirements, new credit loss model or the new general hedge accounting requirements are not expected to have a material impact on the Company’s financial statements. IFRS 15 Revenue from Contracts with Customers In May 2014, the International Accounting Standards Board (IASB) issued IFRS 15—Revenue from Contracts with Customers, which will replace existing revenue recognition guidance. The new standard requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. To achieve that core principle, an entity must identify the contract(s) with a customer, identify the performance obligations in the contract, determine the transaction price, allocate the transaction price to the performance obligations in the contract, and recognize revenue when (or as) the entity satisfies the performance obligation. The new standard will be effective for annual and interim reporting periods beginning on or after January 1, 2018. In anticipation of IFRS 15, the Company performed an impact assessment which consisted of a review of all license and collaboration agreements and government grants. Further, the Company held discussions with key stakeholders and identified and cataloged potential impacts of the new standard on the Company’s financial statements, accounting policies, financial controls and operations. Based on this assessment, the adoption of IFRS 15 will primarily impact the amortization of the Company’s up-front up-front up-front The Company will adopt the standard using the retrospective method, with the effect of initially applying this standard recognized at the beginning of the earliest period presented and will elect to apply the practical expedient to not apply this guidance to contracts which are completed before the beginning of the earliest period presented or January 1, 2016, and the practical expedients for contract modifications (assessing the contracts in combination with any modifications before January 1, 2016). As a result, the impact under this methodology to the Company’s previously reported revenues will be to restate prior reported revenues to conform to the new financial reporting commencing on January 1, 2018. The Company will report new disclosures required by this guidance within the Company’s Form 6-K IFRS 16 Leases The IASB has issued a new standard on leases that will require lessees to recognize most leases on their balance sheets as lease liabilities with a corresponding right-of-use

Segment Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2017
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Segment Reporting	5. Segment Reporting The Company operates in one reportable segment, which comprises the discovery and development of innovative bispecific therapeutics.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2017
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Property, Plant and Equipment	6. Property, Plant and Equipment Movements in property, plant and equipment were as follows: Plant and equipment Other fixed assets Total (euros in thousands) Balance as at January 1, 2016 Costs 325 1,220 1,545 Accumulated depreciation (171 ) (1,049 ) (1,220 ) Book value 154 171 325 Changes in book value Additions 330 166 496 Depreciation (56 ) (117 ) (173 ) Disposals (Cost) (6 ) — (6 ) Disposals (Accumulated depreciation) 6 — 6 Balance 274 49 323 Balance as at December 31, 2016 Costs 649 1,386 2,035 Accumulated depreciation (221 ) (1,166 ) (1,387 ) Book value 428 220 648 Changes in book value Additions 663 113 776 Depreciation (186 ) (70 ) (256 ) Disposals (Cost) (51 ) (1,086 ) (1,137 ) Disposals (Accumulated depreciation) 51 1,086 1,137 Balance 477 43 520 Balance as at December 31, 2017 Costs 1,261 413 1,674 Accumulated depreciation (356 ) (150 ) (506 ) Book value 905 263 1,168

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2017
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Intangible Assets	7. Intangible Assets The intangible assets relate to acquired intellectual property rights. The movements are as follows: 2017 2016 (euros in thousands) Balance as at January 1 Historical cost 860 860 Accumulated amortization (486 ) (425 ) Book value 374 435 Capital expenditures — — Amortization charge for the year (62 ) (61 ) Book value as at December 31 312 374 Balance as at December 31 Historical cost 860 860 Accumulated amortization (548 ) (486 ) Book value 312 374 On January 23, 2009, the Company purchased the family of patents and future filings based on those patents, entitled “Recombinant production of mixtures of antibodies” from Crucell Holland B.V. The non-provisional

Taxation

Taxation	12 Months Ended
	Dec. 31, 2017
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Taxation	8. Taxation Deferred tax assets have not been recognized in respect of tax losses, because the Company has no history of generating taxable profits and at the balance sheet date, there is no convincing evidence that sufficient taxable profit will be available against which the tax losses can be utilized. As of December 31, 2017, the tax losses carried forward amounted to €149.2 million as compared to €101.1 million at December 31, 2016. In order to promote innovative technology development activities and investments in new technologies, a corporate income tax incentive has been introduced in Dutch tax law called the Innovations Box. Based on the Innovations Box ruling, the Company would owe on the first 75% of qualifying profits under the Dutch jurisdiction effectively 5% for Dutch income taxes. The remaining profit would be taxed at the Dutch statutory tax rate of 25%. Taxable profits will only qualify for the Innovations Box once the tax losses carried forward are completely utilized. The agreement with the tax authorities was originally signed for the tax years beginning in 2011 through 2015 and was subsequently extended through the year 2019. Since the Company is loss-making, no Dutch income tax is recognized in the consolidated statement of profit or loss and comprehensive loss. Merus US, Inc., which is incorporated in the United States in the State of Delaware, is subject to statutory U.S. Federal corporate income taxes and state income taxes for Massachusetts at a blended rate of 40% for the years ended December 31, 2017 and 2016. Current year income tax expense was attributable entirely to Merus US, Inc. which was established on February 17, 2016 and provided general management services and strategic advisory services to the Company. Corporate income tax expenses were €0.2 million and zero for the years ended December 31, 2017 and 2016, respectively.

Financial assets

Financial assets	12 Months Ended
	Dec. 31, 2017
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Financial assets	9. Financial assets Derivative On December 20, 2016, the Company entered into a share subscription agreement with Incyte. As the contract is denominated in U.S. dollars, the Company determined that the forward contract to sell its own shares at a future date to which the Company became committed on December 20, 2016 represented a derivative financial instrument. The remaining fair value of the derivative recognized in the statement of financial position at December 31, 2016 was €11.8 million. The Company had determined the fair value of this derivative utilizing the Bloomberg Pricing System and the Company’s closing stock prices at each valuation date which are significant Level 2 observable inputs. On January 23, 2017, the Company settled the forward contract by delivering shares to Incyte upon the closing of the share subscription agreement, thereby extinguishing the derivative financial asset. Upon the extinguishment of the financial asset, the Company recorded finance charges of €10.7 million relating to the change in fair value of the asset and a discount on the share subscription of €1.1 million representing the difference between the original subscription price and the actual price of the common stock on the date of settlement on January 23, 2017. Investments Held to maturity investments are investments in commercial paper, securities issued by several public corporations and the United States Treasury with a maturity date of greater than three months at the date of settlement. Investments with a maturity of 12 months or more from the original investment date are classified as non-current. Investments as of December 31, 2017 consist of the following: (euros in thousands) Commercial paper 15,527 U.S. Treasury securities 9,177 Corporate fixed income bonds 7,886 Agency bond 1,453 Investments, current portion 34,043 Corporate fixed income bonds 7,060 Non-current 7,060 Total investments 41,103 During the fourth quarter of 2017, the Company made purchases of investments totaling €41.8 million which are held and denominated in U.S. dollars. As a result of the fluctuation in foreign currency between the euro and U.S. dollar, the Company recorded unrealized exchanges losses of €0.8 million in net loss on foreign exchange for the year ended December 31, 2017.

Trade and Other Receivables

Trade and Other Receivables	12 Months Ended
	Dec. 31, 2017
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Trade and Other Receivables	10. Trade and Other Receivables All trade and other receivables are short-term and due within 1 year. Balance per December 31 2017 2016 (euros in thousands) Trade receivables 1,594 205 Unbilled receivables 710 — VAT receivable 582 782 Prepaid general expenses 427 382 Prepaid pension costs 838 463 Prepaid share issuance costs — 230 Interest bank 170 32 Other receivables 92 154 4,413 2,248 Trade and unbilled receivables relate primarily to invoicing for cost reimbursements relating to the Incyte collaboration and license agreement and the ONO research and license agreement. VAT receivable relates to value added tax receivable from the Dutch tax authorities based on the tax application for the fourth quarter of 2017. Prepaid expenses reflected above in the form of prepaid general expenses, prepaid pension costs and prepaid share issuance costs consist of expenses that were paid during the reporting period, but are related to activities taking place in the subsequent year.

Other Liabilities and Accruals

Other Liabilities and Accruals	12 Months Ended
	Dec. 31, 2017
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Other Liabilities and Accruals	11. Other Liabilities and Accruals All amounts are short-term and payable within 1 year. Balance per December 31 2017 2016 (euros in thousands) Accrued auditor’s fee 96 282 Personnel 446 220 Research and development costs 5,272 1,256 IP—Legal fee 509 114 Bonuses 1,545 768 Subsidy advance received 224 224 Other accruals 535 786 8,627 3,650 The research and development costs relate to accrued expenses for costs of certain development activities, such as clinical trials, and are recorded based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, and information provided the Company by vendors on their actual costs incurred. The increase in research and development cost accrued expenses reflect increased enrollment in and support of the Company’s clinical trials and expanded pre-clinical The bonuses relate to the employee bonuses for the financial year 2017, which are paid out annually in February. The subsidy advances received relate to active grants where the Company has received cash in excess of allowances which is required to be repaid or recognized as grant income when the relevant reimbursable costs are incurred as services are performed.

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2017
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Borrowings	12. Borrowings The Company entered into a financing agreement with Rabobank Utrechtse Heuvelrug U.A. (“Rabobank”) on December 29, 2005, which provided for total borrowings of €1.5 million for the financing of its business activities. The duration of the agreement was 12 years. Under the agreement, the loans were to be repaid in monthly installments of €14 thousand. The loans bore interest at an annual rate equal to 4.45% and were fixed until April 1, 2016. At that date, the interest rate was fixed at 3.55% until March 31, 2017. Movements in the Company’s borrowings with the Rabobank were as follows: (euros in thousands) Balance December 31, 2016 486 Short term portion December 31, 2016 167 Long term portion December 31, 2016 319 Balance January 1, 2017 486 Repayments (486 ) Balance December 31, 2017 — On March 31, 2017, the Company repaid, in full, the loan from Rabobank. At the repayment date, the total outstanding balance of the loan amounted to approximately €0.5 million. As a result of the repayment, the pledge associated with the loan was removed and the related cash was released from restriction.

Deferred Revenue

Deferred Revenue	12 Months Ended
	Dec. 31, 2017
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Deferred Revenue	13. Deferred Revenue Deferred revenue is as follows: Balance per December 31 (euros in thousands) 2017 2016 Deferred revenue—current portion 6,996 1,610 Deferred revenue 130,195 30,206 137,191 31,816 Of the total deferred revenue balance at December 31, 2017, €137.0 million was related to the Incyte Agreements while €0.2 million related to the ONO research and license agreement. Of the total deferred revenue balance at December 31, 2016, €31.4 million was related to the Incyte Agreements while €0.4 million related to the ONO research and license agreement. On April 8, 2014, the Company entered into a research and license agreement with ONO pursuant to which the Company received a non-refundable upfront a mid-single digit On December 20, 2016, the Company entered into a collaboration and license agreement (the “collaboration and license agreement”) and a share subscription agreement (the “share subscription agreement”) with Incyte (together, the “Incyte Agreements”). Under the collaboration and license agreement, Incyte agreed to pay the Company a $120 million non-refundable non-refundable The parties have agreed to collaborate on the development and commercialization of up to 11 bispecific antibody programs. For one current preclinical program, the Company will retain all rights to develop and commercialize approved products in the United States, and Incyte will develop and commercialize approved products arising from the program outside the United States. Following any regulatory approval of a product candidate for this particular preclinical program, each company has agreed to pay the other tiered royalties ranging from 6% to 10% on net sales of products in their respective territories. The Company also has the option to co-fund development its co-development option, on ex-U.S. sales For each of the other up to eight programs, Incyte has agreed to independently fund all development and commercialization activities. For these programs, the Company will be eligible to receive potential development, regulatory and sales milestone payments of up to $350 million per program, which could result in an aggregate milestone opportunity of approximately $2.8 billion if all development, regulatory and sales milestones are achieved across all such eight other programs in all territories. The Company will also be eligible to receive tiered royalties ranging from 6% to 10% on global sales of any approved products under these eight programs. The Company will retain rights to three of its clinical candidates (MCLA-128, MCLA-117 MCLA-158),

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2017
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Shareholders' Equity	14. Shareholders’ Equity Share subscription agreement with Incyte Concurrent with the collaboration and license agreement discussed above under Note 13, the Company entered into a share subscription agreement with Incyte on December 20, 2016. On January 23, 2017, under the terms of the share subscription agreement, the Company issued 3,200,000 of its common shares to Incyte at a price per share of $25, for an aggregate purchase price of $80.0 million or €74.7 million, representing 19.9% of the “pre-transaction” Issued and Paid-in All issued shares have been fully paid in cash. Common Shares For year ended December 31, 2017, 136,666 options were exercised at a weighted average price of €2.24 per share and 7,331 Restricted Stock Units (“RSUs”) vested; as a consequence, 143,997 common shares were issued, share capital increased by €12,960 and share premium increased by €293,660. For the year ended December 31, 2016, 18,283 options were exercised at an exercise price of €1.93 per share. As a result, 18,283 common shares were issued, share capital increased by €1,645 and share premium increased by €33,641. For the year ended December 31, 2015, no options were exercised. As a result of the IPO, all issued and paid-in one-for-one Situation as at December 31, 2017 At December 31, 2017, a total of 19,429,848 common shares were issued and fully paid in cash. At December 31, 2016, a total of 16,085,851 common shares were issued and fully paid in cash. At December 31, 2015, a total of 4,149,884 Class C preferred shares, 3,899,104 Class B preferred shares, 229,055 Class A preferred shares and 337,562 common shares with a nominal value of €0.09 each were issued and paid up. Share Premium Reserve The share premium reserve relates to amounts contributed by shareholders at the issue of shares in excess of the par value of the shares issued. All share premium can be considered as free share premium as referred to in the Netherlands Income tax act. Share-based Payment Arrangements In 2010, the Company established the Merus B.V. 2010 Employee Option Plan (the “2010 Plan”) that entitled key management personnel, staff and consultants providing similar services to purchase shares in the Company. Under the 2010 Plan, holders of vested options were entitled to purchase depositary receipts for common shares at the exercise price determined at the date of grant. Upon exercise of the option, common shares were issued to a foundation established to facilitate administration of share-based compensation awards and pool the voting interests of the underlying shares, and depositary receipts were issued by the foundation to the individual holders. In connection with the IPO, the 2010 Plan was amended to cancel the depositary receipts and allow individual holders to directly hold the common shares obtained upon exercise of their options. Options granted under the 2010 Plan are exercisable once vested. The options granted under the 2010 Plan vest in installments over a four-year period from the grant date. Twenty-five percent of the options vest on the first anniversary of the vesting commencement date, and the remaining 75% of the options vest in 36 monthly installments for each full month of continuous service provided by the option holder thereafter, such that 100% of the options become vested on the fourth anniversary of the vesting commencement date. Options lapse on the eighth anniversary of the date of grant. Prior to the IPO, participants that voluntarily left the Company, except for members of the former Supervisory Board, were required to offer to the foundation the depositary receipts acquired from exercising options against payment of the exercise price or the lower fair market value of the underlying shares. This obligation for a participant to offer depositary receipts to the foundation upon resignation within four years from exercising the options was treated as a non-market The reduction of the vesting period has been accounted for, taking into consideration the modified vesting conditions, to reflect the best estimate available of the options that are expected to vest. At the modification date in 2016, the cumulative expense for the options has been trued-up non-market In connection with the IPO, the Company established the 2016 Incentive Award Plan (the “2016 Plan”). Following the IPO, the Company is no longer making grants under the 2010 Plan; however, the terms of the 2010 Plan will continue to govern grants made under the 2010 Plan. All new incentive award grants since the IPO are being made under the 2016 Plan. Options granted under the 2016 Plan are exercisable once vested. The options granted under the 2016 Plan vest in installments over a four-year period from the grant date. Twenty-five percent of the options vest on the first anniversary of the vesting commencement date, and the remaining seventy-five percent of the options vest in 36 monthly installments for each full month of continuous service provided by the option holder thereafter, such that 100% of the options shall become vested on the fourth anniversary of the vesting commencement date. Options will lapse on the tenth anniversary of the date of grant. The Restricted Stock Units (“RSUs”) granted under the 2016 Plan also vest in installments over a four-year period from the grant date. Each RSU represents the right to receive one common share of the Company. As stated in the 2016 Plan, the Company also established the Supervisory Board Compensation Program, which was subsequently replaced by the Non-Executive Non-Executive The initial awards granted under the Non-Executive Share-based payment expenses are recognized as from the IPO date for each subsequent award that a Non-Executive Measurement of Fair Value of the Equity-settled Share-based Payment Arrangements The fair value of the employee share options has been measured using a binomial option pricing model, including members of the Board of Directors. Service and non-market There were 2,213,985 outstanding share options at December 31, 2017 (December 31, 2016: 1,394,844; December 31, 2015: 953,689) with a weighted average exercise price of €13.99 (December 31, 2016: €8.69; December 31, 2015: €5.35). The number of options outstanding, by group of employees, was as follows: Group of employees entitled December 31, 2017 December 31, 2016 December 31, 2015 Key management personnel 1,777,437 1,302,417 857,318 All other employees 436,548 92,427 96,371 Total 2,213,985 1,394,844 953,689 The inputs used in the measurement of the fair values and the related fair values at the grant dates for the options granted during the respective year ended December 31 were as follows: 2017 2016 2015 Key Management All Other Key Management All Other Key All Other € € € € € € Fair value at grant date 9.04 – 16.10 8.94 – 18.02 9.97 – 11.03 5.74 – 5.79 3.98 – 5.76 4.03 – 5.06 Share price at grant date 17.08 – 24.54 13.71 – 27.47 15.24 – 16.85 8.46 – 8.87 6.12 – 7.20 5.94 – 7.20 Exercise price 17.08 – 24.54 13.71 – 27.47 15.24 – 16.85 8.46 – 8.87 1.93 – 7.20 1.93 – 7.20 Expected volatility (weighted-average) 95.05% 94.88% 95.30% 97.15% 94.85% 94.85% Expected life 10 years 10 years 10 years 8 – 10 years 4 years 8 years Expected dividends 0% 0% 0% 0% 0% 0% Risk-free interest rate (based on government bonds) 2.29% – 2.51% 2.24% – 2.62% 1.84% – 1.86% 0.10% – 1.87% 0.16% – 0.70% 0.16% – 0.70% Reconciliation of outstanding share options and RSU’s 2017 2016 2015 Weighted Number of Weighted Number of Weighted Number of (€) (€) (€) Outstanding at January 1 8.69 1,394,844 5.35 953,689 5.15 192,276 Forfeited during the year 17.27 (58,164 ) 6.07 (31,351 ) 1.93 (1,033 ) Expired during the year 8.67 (762 ) 11.95 (5,454 ) 4.18 (9,216 ) Exercised during the year 2.24 (136,666 ) 1.93 (18,283 ) — — Granted during the year 19.88 1,014,733 14.74 496,243 5.99 771,662 Outstanding at December 31 13.99 2,213,985 8.69 1,394,844 5.35 953,689 Exercisable at December 31 687,070 418,453 157,562 The options outstanding at December 31, 2017 had an exercise price in the range of €1.93 to €27.47 (2016: €1.93 to €16.85; 2015: €1.93 to €13.50) and a weighted-average remaining contractual life of 8.25 years (2016: 6.68 years; 2015: 3.63 years). On October 5, 2015, the Company amended the exercise price of options granted under the 2010 Option plan prior to January 2015, to be €1.93, which has been reflected in the weighted average exercise price of the options outstanding at December 31, 2015. The weighted-average share price at the date of exercise for share options exercised in 2017 was €20.69. During 2017, the Company granted RSUs to Key Management Personnel. RSU’s are summarized as follows: 2017 Weighted average exercise price Number of RSU’s (€) Outstanding at January 1 — — Forfeited during the year 20.03 (12,219 ) Expired during the year — — Vested during the year 20.03 (7,331 ) Granted during the year 20.03 214,096 Outstanding at December 31 20.03 194,546 Expense Recognized in Profit or Loss For details on the related option expenses recognized as employee benefit expenses, see Note 17.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2017
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Revenue	15. Revenue (euros in thousands) 2017 2016 2015 Up-front 6,616 223 223 Collaboration income 5,789 1,109 1,092 Income from grants on research projects 1,195 1,387 662 13,600 2,719 1,977 For the year ended December 31, 2017, the Company recognized amortization of €6.4 million and €0.2 million on up-front up-front Collaboration income for the year ended December 31, 2017 was €5.8 million and consisted of cost reimbursements in support of the Company’s research and license agreements with Incyte and ONO. The Company did not recognize any research milestones during 2017. During 2016, the Company recognized one research milestone reached by the Company under its agreement with ONO which amounted to €0.7 million (2015: €1.1 million). Additionally, the Company received an amount of €0.4 million revenue from a new consultancy agreement that was signed with ONO on March 7, 2016. The Company currently has two active grants consisting of cash allowances for specific research and development projects. For these grants, the Company has reporting obligations at the end of the grant contract term. The unconditional receipt of the grant allowances is dependent on the final review of the reporting provided by Merus at the end of the contract term. For the years ended December 31, 2017, 2016, and 2015, the Company recognized €1.2 million, €1.4 million and €0.7 million in grant income, respectively. On June 12, 2017, the European Commission approved for reimbursement the final installment of the FP-7

Total Operating Expenses

Total Operating Expenses	12 Months Ended
	Dec. 31, 2017
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Total Operating Expenses	16. Total Operating Expenses 2017 2016 2015 (Euros in thousands) Manufacturing costs 13,567 3,162 5,878 IP and license costs 1,858 1,167 1,112 Personnel related R&D 6,673 3,285 2,997 Other research and development costs 12,027 10,810 6,194 Total research and development costs 34,125 18,424 16,181 Management and administration costs 13,697 4,258 768 Litigation costs 1,039 1,490 4,419 Other operating expenses 8,356 6,219 3,648 Total other expenses 9,395 7,709 8,067 Total operating expenses 57,217 30,391 25,016 Research and development costs were €34.1 million for the year ended December 31, 2017 as compared to €18.4 million for 2016. The increases in research and development costs is primarily attributable to the increase in manufacturing costs, higher research and development headcount and related costs, including share-based payment expenses, as well as additional spending in support of the Company’s preclinical and clinical development programs for MCLA-128, MCLA-117, MCLA-158 MCLA-145. Personnel related research and development expenses mainly increased due to higher headcount to support the expansion of clinical programs and additional expenses resulting from the implementation of the new option plan in 2016 (see Note 14) whereas initial equity grants made in 2016 with higher market valuations were expensed over a full year in 2017. Other research and development costs represent costs related to expenditures to contract research organizations and related expenses in support of preclinical and clinical activities. Management and administrative costs consist of salaries and related expenses for employees in finance, legal, human resources and business development functions. These costs include all salary, salary related expenses and share-based payment expenses. The large increase in management and administrative costs during 2017 was due primarily to the expansion of the Company’s headcount in finance, legal and business development functions to support the expansion of the Company’s operations. Other operating expenses consist primarily of expenses related to professional fees for consulting, audit, and tax services of €4.0 million (2016: €1.7 million, 2015: €1.0 million) which support the finance function in maintaining and establishing public company status and general legal, insurance and facility related expenses amounting to €3.2 million (2016: €3.9 million, 2015: €2.2 million). The increase in these costs during 2017 is due to the expansion of the Company’s operations to support ongoing growth and public company requirements. Litigation costs relate to ongoing legal proceedings which are more fully described under “Litigation”. The decline in 2017 when compared to 2016 is a result of lower litigation activity with regard to the Regeneron litigation as described below. A breakdown of other research and development costs is presented as follows: 2017 2016 2015 (Euros in thousands) Discovery and pre-clinical 2,473 5,185 2,534 Clinical costs 5,919 3,409 1,883 Consumables 2,149 1,055 979 Other research and development costs 1,486 1,161 798 Total other research and development costs 12,027 10,810 6,194 Other research and development costs consist mainly of consultancy expenses related to R&D activities, which cannot be specifically allocated to a research project. Litigation On March 11, 2014 Regeneron Pharmaceuticals Inc. (“Regeneron”) filed a complaint in the United States District Court for the Southern District of New York (the “Court”), alleging that the Company was infringing on one or more claims in Regeneron’s U.S. Patent No. 8,502,018 (the “‘018 patent”), entitled “Methods of Modifying Eukaryotic Cells.” On July 3, 2014, the Company filed a response to the complaint, denying Regeneron’s allegations of infringement and raising affirmative defenses, and filed counterclaims seeking, among other things, a declaratory judgment that the Company did not infringe the patent and that the patent was invalid. The Company subsequently filed amended counterclaims during the period from August to December 2014, seeking a declaratory judgment of unenforceability of the patent due to Regeneron’s commission of inequitable conduct. On November 21, 2014, the Court found that there was clear and convincing evidence that a claim term present in each of the patent claims was indefinite and granted the Company’s proposed claim constructions. On February 24, 2015, the Court entered partial judgment in the proceeding, on the grounds that the Company did not infringe each of the patent claims, and that each of the patent claims were invalid due to indefiniteness. On November 2, 2015, the Court found Regeneron had withheld material information from the United States Patent and Trademark Office during prosecution of the patent, and Regeneron had engaged in inequitable conduct and affirmative egregious misconduct in connection with the prosecution of the patent. On December 18, 2015, Regeneron filed an appeal of the Court’s decision. On July 27, 2017, the U.S. Court of Appeals for the Federal Circuit affirmed the trial court’s conclusion that Regeneron had engaged in inequitable conduct before the United States Patent and Trademark Office and affirmed that Regeneron’s ‘018 patent is unenforceable. Regeneron petitioned for a panel rehearing and rehearing en banc of this decision by the Federal Circuit on September 12, 2017, which the Company responded to and opposed on November 2, 2017. On December 26, 2017, the full Federal Circuit denied Regeneron’s request to rehear the matter. The case is returned to the District Court to adjudicate the Company’s motion requesting that Regeneron pay Merus’ attorney’s fees and costs incurred as a result of Regeneron filing suit. On March 11, 2014, Regeneron served a writ in the Netherlands alleging that the Company was infringing one or more claims in their European patent EP 1 360 287 B1. The Company opposed the patent in June 2014. On September 17, 2014, Regeneron’s patent EP 1 360 287 B1 was revoked in its entirety by the European Opposition Division of the European Patent Office (the “EPO”). In Europe, an appeal hearing occurred in October and November 2015 at the Technical Board of Appeal for the EPO at which time the patent was reinstated to Regeneron with amended claims. The Company believes that its current business operations do not infringe the patent reinstated to Regeneron with amended claims because it believes it has not used the technology or methods claimed under the amended claims. The Dutch litigation procedure is stayed. The costs incurred in the above litigation and opposition (€1.0 million in 2017; €1.5 million in 2016; €4.4 million in 2015) are included in the consolidated statement of profit or loss and comprehensive loss for the period. On July 15, 2014, a notice of opposition against Merus’ EP 2314629 patent (the “EP ‘629 patent”), entitled “Recombinant Production of Mixtures of Antibodies” was filed in the European Patent Office (the “EPO”) by Regeneron. The notice asserted, as applicable, added subject matter, lack of novelty, lack of inventive step, and insufficiency. Merus responded on February 24, 2015. Following an oral hearing before the Opposition Division of the EPO on June 22, 2016, the Opposition Division upheld the EP ‘629 Patent with amendments. Both Regeneron and Merus filed a notice of appeal followed by grounds of appeal on December 1st and 4th, 2017 respectively, with further proceedings to follow. On August 11, 2014, a notice of opposition against Merus’ EP 2147594 (the “EP ‘594 patent”), entitled “Antibody Producing Non-Human Based on the current facts and circumstances no provision has been recognized under IAS 37 related to contingent liabilities. Operating expenses presented by nature are outlined below: 2017 2016 2015 (Euros in thousands) Contract manufacturing 13,567 3,162 5,878 Other external and outsourced costs 22,333 18,885 15,012 Employee costs & related benefits 20,999 8,110 3,933 Depreciation and amortization 318 234 193 Total operating expenses 57,217 30,391 25,016 The increases in costs of contract manufacturing and other external and outsourced costs are mainly due to the increase in the Company’s preclinical and clinical operations in support of its programs for MCLA-128, MCLA-117, MCLA-158 MCLA-145.

Employee Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2017
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Employee Benefits	17. Employee Benefits Details of the employee benefits are as follows: 2017 2016 2015 (Euros in thousands) Salaries and wages 9,556 5,166 3,204 WBSO subsidy (3,523 ) (1,721 ) (348 ) Social security premiums 621 382 238 Health insurance 222 27 31 Pension costs 652 507 241 Share-based payment expenses 12,815 3,307 567 Other personnel expense 656 442 — 20,999 8,110 3,933 Share-based payment expenses (see Note 14) were recognized as employee benefit expenses as follows: (euros in thousands) 2017 2016 2015 Research and development costs 3,245 703 168 Management and administration costs 8,942 2,037 230 Other expenses 628 567 169 12,815 3,307 567 The WBSO (“ afdrachtvermindering speur- en ontwikkelingswerk The Company has received and recognized subsidies of €3.5 million (2016: €1.7 million; 2015: €0.3 million). The increases in subsidies for each year are primarily attributable to the increase in the Company’s eligible research and development activities and the expansion of the Company’s preclinical and clinical development programs for MCLA-128, MCLA-117, MCLA-158 MCLA-145. The average number of personnel during the year was approximately 69 (2016: 45; 2015: 32), with a majority employed in the Netherlands, with the exception of an average of ten (2016: two; 2015: nil) employees employed in the United States. Employees are principally employed in the area of research and development. For the years ended December 31, 2017 and 2016, a total of 21 and 11 employees, respectively, which are devoted to activities other than research and development, are included under management and administration costs.

Finance Income and Expense

Finance Income and Expense	12 Months Ended
	Dec. 31, 2017
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Finance Income and Expense	18. Finance Income and Expense 2017 2016 2015 (Euros in thousands) Interest and related income 1,112 88 50 Net loss on foreign exchange (19,449 ) (409 ) — Interest and other expenses (10,696 ) (19,235 ) (195 ) Financing costs (190 ) — — (29,223 ) (19,556 ) (145 ) Interest income primarily results from interest earned on cash held on account and accretion of investment earnings. The Company’s current year increase in cash, cash equivalents and investments was due primarily from the $200 million of funds received as part of the Incyte Agreements during the first quarter of 2017. During 2017, the Company has held the $200 million of Incyte funds in short-term investments with a one month maturity, callable on demand, and later in the year, in short-term investments in securities issued by several public corporations and United States Treasury, denominated and held in U.S. dollars. In July and August 2017, the Company converted $50.3 million of U.S. dollars into euros from the account effectively realizing exchange losses of €4.4 million, included in net loss on foreign exchange for the year ended December 31, 2017. The Company experienced losses on its U.S. dollar denominated cash, cash equivalents and investments of approximately €19.4 million and €0.4 million for the years ended December 31, 2017 and 2016, respectively. As of December 31, 2017, the Company held approximately $98.0 million and $49.4 million in U.S. dollar denominated cash and cash equivalent accounts and investment accounts, respectively, subject to the fluctuation in foreign currency between the euro and U.S. dollar. On December 20, 2016, the Company entered into the Incyte Agreements. As these contracts are denominated in U.S. dollars, the Company determined that the subscription agreement to sell its own shares to which the Company became committed on December 20, 2016, should be accounted for as a forward contract or a derivative financial instrument which was recognized in the consolidated statement of financial position as of December 31, 2016. The interest expense and similar expenses for the year ended December 31, 2017 include an amount of €10.7 million related to the effective settlement of the forward contract on January 23, 2017, the date the shares were issued and the date through which the related expense was incurred. During 2017, the Company expensed €0.2 million of prepaid share issuance costs related to a potential future issuance of shares under the Company’s F-3

Loss per share

Loss per share	12 Months Ended
	Dec. 31, 2017
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Loss per share	19. Loss per share (a) Basic and Diluted Loss per Share Basic loss per share is calculated by dividing the loss attributable to equity holders of the Company by the weighted average numbers of shares outstanding during the year. 2017 2016 2015 (Euros in thousands, except per share data) Loss attributable to equity holders of the Company (73,000 ) (47,220 ) (23,184 ) Weighted average number of shares 19,196,440 13,236,649 5,871,237 Basic (and diluted) loss per share (€ per share) (3.80 ) (3.57 ) (3.95 ) (b) Diluted Loss per Share For the periods included in these financial statements, the share options are not included in the diluted loss per share calculation as the Company was loss-making in all these periods. Due to the anti-dilutive nature of the outstanding options, basic and diluted loss per share is equal. (c) Dividends per Share The Company did not declare dividends for any of the years presented in these financial statements.

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2017
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Financial Instruments	20. Financial Instruments Financial Risk Management The Company is exposed to a variety of financial risks: credit risk, liquidity risk and market risk. The Company’s overall risk management program seeks to minimize potential adverse effects of these financial risk factors on the Company’s financial performance. Management is primarily responsible for the overall risk management approach and for the approval of risk strategies and principles of the Company. The Company’s Audit Committee oversees these risk management activities. The Company’s management reviews and approves policies for managing each of these risks which are summarized below. Credit Risk Credit risk is the risk of financial loss to the Company if a customer or counterparty to a financial instrument fails to meet its contractual obligations, and arises principally from the Company’s receivables from its collaborators and investments in debt securities and financial institutions. The Company’s principal financial assets are held to maturity investments, trade receivables, and cash and cash equivalents that are derived primarily from financing activities and, to a lesser extent, from its operations. The main purpose of these financial assets are to support the Company’s operations which consist primarily of research and development, preclinical and clinical development and related manufacturing in support of the Company’s preclinical and clinical development programs for MCLA-128, MCLA-117, MCLA-158 MCLA-145. The carrying amount of financial assets represents the maximum credit exposure. 2017 2016 (Euros in thousands) Financial Assets Financial asset (derivative) — 11,847 Trade and unbilled receivables 2,283 205 Investments 41,103 — Restricted cash — 167 Cash and cash equivalents 149,678 56,917 193,064 69,136 Cash and cash equivalents include deposits held with financial institutions with original maturities of less than three months. Investments, held to maturity, include commercial paper, securities issued by several public corporations and the United States Treasury with a maturity date of greater than three months at the date of settlement. These investments were acquired in fourth quarter of 2017. Cash and cash equivalents are held at banks and financial institutions with credit ratings varying between A and AA while investments are in highly rated vehicles with identical credit ratings. As discussed in Note 9, the Company entered into a share subscription agreement with Incyte in December 2016. As the contract is denominated in U.S. dollars, the Company determined that the forward contract to sell its own shares at a future date represented a derivative financial instrument. The remaining fair value of the derivative recognized in the statement of financial position at December 31, 2016 was €11.8 million. The Company had determined the fair value of this derivative utilizing the Bloomberg Pricing System and the Company’s closing stock prices at each valuation date which are significant Level 2 observable inputs. The settlement of the forward contract occurred through the delivery shares to Incyte upon the closing of the share subscription agreement during the first quarter of 2017 thereby extinguishing the derivative financial asset. The aging of trade and unbilled receivables was as follows: 2017 2016 Balance per December 31 in thousands of euros Neither past due nor impaired 2,283 205 Past due — — 2,283 205 There is no allowance for impairment. Liquidity Risk Liquidity risk is the risk that the Company will not be able to meet its financial obligations as they become due. The Company’s core objective is to maintain a balance between continuity of funding and flexibility through the monitoring of cash flows at varying levels to ensure that it has sufficient cash on demand to meet expected operational expenses. The following are the remaining contractual maturities of financial liabilities at the reporting date. The amounts are gross and undiscounted, and include estimated interest payments and excluding the impact of netting agreements: December 31, 2017 Carrying amount Total < 12 months 1 - 2 years 2 - 5 years More than 5 years (Euros in thousands) Non-derivative Trade payables 2,855 2,855 2,855 — — — Other liabilities and accruals 6,176 6,176 6,176 — — — 9,031 9,031 9,031 — — — December 31, 2016 Carrying amount Total < 12 months 1 - 2 years 2 - 5 years More than 5 years (Euros in thousands) Non-derivative Secured bank loans 486 526 190 181 155 — Trade payables 2,298 2,298 2,298 — — — Other liabilities and accruals 3,679 3,679 3,679 — — — 6,463 6,503 6,167 181 155 — The secured bank loan was paid in full on March 31, 2017. Market risk Market risk is the risk that changes in market prices – such as foreign exchange rates and interest rates – will affect the Company’s income or the value of its holdings of financial instruments. The objective of market risk management is to manage and control market risk exposures within acceptable parameters, while optimizing the return. The Company’s market risk relates to foreign exchange and to a lesser extent, interest risks. Foreign currency risk Foreign exchange risk arises from future commercial transactions and recognized assets and liabilities in foreign currencies. With respect to monetary assets and liabilities denominated in foreign currencies, the Company’s primary currency exposure is impacted by monetary assets and liabilities denominated in U.S. Dollars (USD). Changes in sensitivity rates reflect various changes in the economy year-over-year. The following table provides a sensitivity analysis for a change in the primary currency exposure for the Company relating to monetary assets and liabilities denominated in USD as of December 31, 2017. The analysis shows the impact that a change in the exchange rate at that date would have on the Company’s total comprehensive loss: Financial Statement Line Item Exposure Balance (in Effect on profit before tax if USD Effect on profit before tax if USD Cash and cash equivalents 88,538 3,691 (3,691 ) Total investments 47,310 1,972 (1,972 ) Trade and other receivables 2,311 97 (97 ) Trade payables, other liabilities and accruals (1,420 ) (59 ) 59 Net Assets 136,739 5,701 (5,701 ) The closing exchange rates per the European Central Bank (ECB) utilized above for converting USD to EUR at December 31, 2017 was 0.834. Exposure to interest rate risk The interest rate profile of the Company’s interest-bearing financial instruments is as follows: Carrying amount 2017 2016 Balance per December 31 in thousands of euros Fixed-rate instruments Investments 41,103 — Financial liabilities — (486 ) Variable rate instruments Cash and cash equivalents 149,678 56,917 Due to the limited impact of changes in interest rates on the Company no sensitivity data is provided. Accounting classifications and fair values The Company classifies financial assets and financial liabilities into the loans and receivables and other financial liability categories except for the derivative recognized as a result of the Incyte collaboration and share Subscription agreement as more fully described in Note 9. The fair value of the financial assets and financial liabilities not measured at fair value is not disclosed, as the carrying amount of the financial assets and financial liabilities is a reasonable approximation of the fair value. Accordingly, information on the fair value hierarchy is omitted. The fair value of the derivative related to the Incyte collaboration and share Subscription agreement was recorded using Level 2 inputs. For determining the fair value the Company has used as valuation technique the Bloomberg forward pricing model. In this valuation the inputs used are related to the foreign exchange component (spot prices of EUR and USD), closing stock prices of the Company, as well as discount rates to reflect the time value of money (limited). On January 23, 2017, the Company settled the forward contract by delivering shares to Incyte upon the closing of the share subscription agreement, thereby extinguishing the derivative financial asset.

Board Compensation and Key Mana

Board Compensation and Key Management Personnel	12 Months Ended
	Dec. 31, 2017
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Board Compensation and Key Management Personnel	21. Board Compensation and Key Management Personnel On May 29, 2017, the Company changed its governance structure from a two-tier one-tier Non-Executive one-tier Non-Executive to-day Non-Executive Prior to May 29, 2017, the Company’s Management Board was in charge of managing the Company and consisted of Ton Logtenberg, Chief Executive Officer (CEO) and Shelly Margetson, the former Chief Operating Officer (COO). Ms. Margetson resigned as a statutory director of the Company effective as of May 24, 2017 and ended her employment with the Company effective as of August 1, 2017. The Supervisory Board was responsible for the supervision of the Management Board and the general course of affairs of the Company. Subsequent to May 29, 2017, the members of the Supervisory Board are now Non-Executive In addition to Board of Directors, the Company employs certain Key Management Personnel responsible for executing the day-to-day Executive Directors In 2017, 2016, and 2015 the following amounts were charged to the consolidated statement of profit or loss and comprehensive loss for the remuneration of the statutory directors: December 31, Name Gross Salary Bonus Pension Option cost Total (Amounts in Euros) Ton Logtenberg, CEO 2017 432,782 337,945 51,528 4,675,590 5,497,845 2016 369,204 147,820 17,717 907,236 1,441,977 2015 236,032 89,072 18,591 1,910,204 2,253,899 Shelley Margetson(*), COO 2017 (**) 420,782 — 19,595 451,752 892,129 2016 198,987 84,000 6,152 164,547 453,686 2015 159,749 37,365 13,824 284,938 495,876 (*) Resigned as a statutory director of the Company effective as of May 24, 2017. (**) Gross salary includes severance payments totaling €257,260. During the year ended December 31, 2017, Mr. Logtenberg was granted 377,271 options and 123,745 RSU’s while Ms. Margetson was granted 59,605 options and 19,550 RSU’s. In addition, upon her separation date, Ms. Margetson was entitled to an accelerated vesting of any unvested Company options and restricted stock units held that would have vested during the 12-month As of December 31, 2017, Mr. Logtenberg held 661,629 options (2016: 376,912; and 2015: 54,866) with a weighted average exercise price of €14.20 (2016: €2.98; 2015: €5.35) and 123,745 RSU’s. Key Management Personnel The remainder of the key management personnel has received the following remuneration for the year 2017. Remuneration 2017 2016 2015 (Amounts in Euros) Short term employment benefits 2,808,998 1,139,763 190,763 Post-employment benefits 108,416 18,720 11,671 Other long term benefits — — — Termination benefits — — — Share based payments 5,171,233 1,195,876 57,065 Total 8,088,647 2,354,359 259,499 Some of the key management personnel have long term benefits in the form of life and long term disability insurance policies which have been affected in their name as well as severance conditions in case of termination without cause or leave for good reason. A number of key management personnel, or their related parties, hold positions in other companies that result in them having control or significant influence over these companies. These companies did not enter into transactions with the Company during the year. On October 27, 2016, the Company appointed Andres Sirulnik as its Chief Medical Officer (CMO). A total 219,890 options over common shares were granted to Dr. Sirulnik with an exercise price of €16.85 per option. On February 15, 2017, the Company appointed Peter Silverman as its Senior Vice President, Legal (SVP). A total 50,000 options over common shares were granted to Mr. Silverman with an exercise price of €24.54 per option. On November 1, 2016, the Company appointed John Crowley as its Chief Financial Officer. A total of 183,241 options over common shares were granted to Mr. Crowley with an exercise price of €15.24 per option. On October 5, 2015, the Company amended the exercise price of options granted under the 2010 Option plan prior to January 2015, to be €1.93. Those option holders that had already exercised options under this plan were reimbursed the excess paid over €1.93 per share. This amounted in a total reimbursement of €60,935. Non-Executive In May 2016, the Company established the Supervisory Board Remuneration Program, which was subsequently replaced by the Non-Executive Non-Executive The following amounts were charged to the consolidated statement of profit or loss and comprehensive loss for the remuneration of the members of the Board: December 31, 2017 December 31, 2016 December 31, 2015 Name Cash compensation Option Total Cash compensation Option Total Cash compensation Option Total (Amounts in Euros) (Amounts in Euros) (Amounts in Euros) Mark Iwicki 59,840 120,596 180,436 50,394 183,367 233,761 26,325 115,380 141,705 Wolfgang Berthold 37,530 90,944 128,474 19,850 50,928 70,778 — 15,475 15,475 Lionel Carnot 35,445 61,870 97,315 24,852 66,959 91,811 — — — John de Koning 38,573 113,613 152,186 26,230 37,000 63,230 — — — Anand Mehra 39,615 83,683 123,298 26,938 84,703 111,641 — — — Gregory Perry 41,700 103,169 144,869 28,356 97,365 125,721 — — — Gabriele Dallmann(*) — — — — — — 11,000 5,795 16,795 Gerard van Odijk(*) — — — — — — — 16,298 16,298 Total 252,703 573,875 826,578 176,620 520,322 696,942 37,235 152,948 190,273 (*) former board member As at December 31, members of the Board held the following number of options: December 31, 2017 December 31, 2016 December, 31 2015 Name Number Weighted exercise price Number Weighted exercise price Number Weighted exercise price Mark Iwicki 79,226 € 7.32 73,576 € 6.57 73,576 € 6.57 Wolfgang Berthold 24,040 € 8.90 26,724 € 3.02 14,168 € 1.93 Lionel Carnot 22,650 € 11.80 17,000 € 8.87 — — John de Koning 22,650 € 11.80 17,000 € 8.87 — — Anand Mehra 22,650 € 11.80 17,000 € 8.87 — — Gregory Perry 22,650 € 11.80 17,000 € 8.87 — — Gabriele Dallmann(*) — — 16,828 € 3.24 4,272 € 1.93 Gerard van Odijk(*) — — — — 21,874 € 1.93 Total 193,866 € 9.61 185,128 € 7.21 113,890 € 4.93 (*) former board member

Related party disclosures

Related party disclosures	12 Months Ended
	Dec. 31, 2017
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Related party disclosures	22. Related party disclosures For the years ended December 31, 2017, 2016, and 2015, certain Key Management Personnel and other senior management received regular salaries, bonuses and contributions to post-employment schemes as well as non-cash non-cash On May 24, 2017, the Company entered into a settlement agreement with Shelley Margetson, the Company’s former Chief Operating Officer pursuant to which Ms. Margetson resigned as a statutory director of the Company effective as of May 24, 2017 and ended her employment with the Company effective as of August 1, 2017. As part of the terms of the settlement agreement, Ms. Margetson is entitled to a severance payment equal to 12 months of her annual base salary, 50% of which was paid in a lump sum in August 2017 and the remaining 50% is being paid in the form of salary continuation over the six-month 12-month As of March 28, 2018, the following shareholders currently hold a position in the Board of Directors and have filed a form 13-D • Bay City Capital Coöperatief U.A. • Coöperatief LSP IV U.A. • Sofinnova Venture Partners IX, L.P. Additionally, Ton Logtenberg, the Company’s CEO) and Executive Director, is the sole the Director and owner of Biophrase BV (“Biophrase”). As of March 28, 2018, Biophrase is a less than 1% shareholder. There were no transactions between the Company and Biophrase BV in 2017.

Operating leases

Operating leases	12 Months Ended
	Dec. 31, 2017
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Operating leases	23. Operating leases Rent On November 1, 2016, Merus N.V. closed a new lease agreement with Stichting Incubator Utrecht for a new office building. The agreement term is for five years and expires in the fourth quarter of 2021. If the lease is not terminated by Merus, it will be automatically renewed for a period of two years. The agreed rental price is €434 thousand per year. The Company moved into the new office building in November 2016. For the years ended December 31, 2017, and 2016, the Company recognized an amount of €564 thousand and €270 thousand, respectively, for rent and service charges related to the abovementioned buildings. Future minimum lease payments under this lease as at December 31, 2017 are payable as follows: Less than one year 602 Between one and five years 1,897 More than five years — Total 2,499

Subsequent events

Subsequent events	12 Months Ended
	Dec. 31, 2017
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Subsequent events	24. Subsequent events On January 8, 2018, the Company and Simcere Pharmaceutical Group executed a collaboration and license agreement and agreed to grant Simcere an exclusive license to develop and commercialize in China three bispecific antibodies utilizing the Company’s Biclonics ® On February 13, 2018, the Company entered into a Purchase Agreement with the purchasers named therein. Pursuant to the Purchase Agreement, the Company agreed to sell an aggregate of 3,099,997 of its common shares, nominal value €0.09 per share, to the Investors for aggregate gross proceeds of approximately $55.8 million, at a purchase price equal to $18.00 per share. The Purchase Agreement contains customary representations and warranties from the Company and the Investors and customary closing conditions. The closing of the Private Placement occurred on February 15, 2018. On February 13, 2018, in connection with the Purchase Agreement, the Company entered into a Registration Rights Agreement with the Investors. Pursuant to the Registration Rights Agreement, the Company agreed to prepare and file a registration statement with the SEC no later than May 15, 2018 for purposes of registering the resale of the Shares. As part of the terms of the Registration Rights Agreement, the Company agreed to use its reasonable best efforts to cause this registration statement to be declared effective by the SEC prior to the 120th day after the Closing Date (or the 150th day if the SEC reviews the registration statement). On March 14, 2018, we entered into a second contract research and license agreement with ONO. Pursuant to an exclusive option granted to ONO in a prior agreement executed in April 2014, ONO exercised its option to enter into the March 2018 agreement. We granted ONO an exclusive, worldwide, royalty-bearing license, with the right to sublicense, research, test, make, use and market bispecific antibody candidates based on our Biclonics ® non-clinical ONO has agreed to pay an upfront non-refundable mid-single

Basis of Preparation (Policies)

Basis of Preparation (Policies)	12 Months Ended
	Dec. 31, 2017
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Functional and Presentation Currency	Functional and Presentation Currency The financial statements are presented in euros, which is the Company’s functional and presentation currency. All amounts are rounded to the nearest thousands of euros, except as otherwise indicated.
Use of Estimates, Judgements and Assumptions	Use of Estimates, Judgements and Assumptions In the application of the Company’s accounting policies, management is required to make judgments, estimates and assumptions that affect the reported amounts of assets, liabilities, income and expenses 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. Estimates and underlying assumptions are reviewed on an ongoing basis. Revisions to accounting estimates are recognized prospectively. The following are the critical judgments and assumptions that management has made in the process of applying the Company’s accounting policies and that have the most significant effect on the amounts recognized in the financial statements.
Capitalization of Development Costs	Capitalization of Development Costs The criteria for capitalization of development costs have been considered by management and determined not to have been met in the twelve month period ended December 31, 2017. Therefore, all development expenditures relating to internally generated intangible assets in the twelve month period ended December 31, 2017 were expensed as incurred.
Income Tax	Income Taxes The criteria for the recognition of unused tax losses are disclosed in Note 3 “Significant accounting policies”. As of December 31, 2017, deferred tax assets have not been recognized in respect of tax losses, because the Company has no history of generating taxable profits and therefore, it is not probable that sufficient taxable profit will be available against which the tax losses can be utilized. The amount of the unrecognized tax losses is disclosed in Note 8. Income tax expense comprises current and deferred tax. It is recognized in the statement of profit or loss and comprehensive loss except to the extent that it relates to a business combination, or items recognized directly in equity or in other comprehensive income. Current tax comprises the expected tax payable or receivable on the taxable income or loss for the year and any adjustment to tax payable or receivable in respect of previous years. It is measured using tax rates enacted or substantively enacted at the reporting date. Current tax also includes any tax arising from dividends. Current tax assets and liabilities are offset only if certain criteria are met. Deferred tax is recognized in respect of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for taxation purposes. Deferred tax is not recognized for: • temporary differences on the initial recognition of assets or liabilities in a transaction that is not a business combination and that affects neither accounting nor taxable profit or loss; • temporary differences related to investments in subsidiaries, associates and joint arrangements to the extent that the group is able to control the timing of the reversal of the temporary differences and it is probable that they will not reverse in the foreseeable future; and • taxable temporary differences arising on the initial recognition of goodwill. Deferred tax assets are recognized for unused tax losses, unused tax credits and deductible temporary differences to the extent that it is probable that future taxable profits will be available against which they can be used. Deferred tax assets are reviewed at each reporting date and are reduced to the extent that it is no longer probable that the related tax benefit will be realized; such reductions are reversed when the probability of future taxable profits improves. Unrecognized deferred tax assets are reassessed at each reporting date and recognized to the extent that it has become probable that future taxable profits will be available against which they can be utilized. Deferred tax is measured at the tax rates that are expected to be applied to temporary differences when they reverse, using tax rates enacted or substantively enacted at the reporting date. The measurement of deferred tax reflects the tax consequences that would follow from the manner in which the Company expects, at the reporting date, to recover or settle the carrying amount of its assets and liabilities. Deferred tax assets and liabilities are offset only if certain criteria are met.
Deferred Revenue	Deferred Revenue The Company maintains certain research, collaboration and license agreements with ONO Pharmaceuticals Co., Ltd (“ONO”) and Incyte under which the Company has received upfront non-refundable
Equity Settled Share-Based Payments	Equity Settled Share-Based Payments Share options granted to employees, consultants and directors are measured at the grant date fair value of the equity instruments granted. The grant date fair value is determined through the use of an option-pricing model considering the following variables: (a) the exercise price of the option; (b) the expected life of the option; (c) the current value of the underlying shares; (d) the expected volatility of the share price; (e) the dividends expected on the shares; and (f) the risk-free interest rate for the life of the option. Prior to the Company’s IPO, the estimated the fair value of each share option granted was determined utilizing the Black-Scholes option-pricing model. For the Company’s share option plans subsequent to its IPO, management’s judgment was that the Hull & White option pricing model is the most appropriate method for determining the fair value of the Company’s share options considering the terms and conditions attached to the grants made and reflective of exercise behavior. Since the Company was not listed on a national securities exchange until May 19, 2016, there was no published share price information available until May 19, 2016. Consequently, the Company estimated the fair value of its shares and the expected volatility of that share value for the period up to May 19, 2016. As the Company’s shares have not been publicly traded for a sufficient amount of time, the expected volatility was set by considering the historic share price volatility of a set of peer companies. For pre-IPO post-IPO The result of the share option valuations and the related compensation expense that is recognized for the respective vesting periods during which services are received, is dependent on the model and input parameters used. Even though management considers the fair values reasonable and defensible based on the methodologies applied and the information available, others might derive a different fair value for the Company’s share options. These assumptions and estimates are further discussed in Note 14 to the financial statements.
Basis of consolidation	Basis of consolidation (i) Subsidiaries Subsidiaries are entities controlled by the Company, consisting of Merus N.V. and its wholly owned subsidiary Merus US, Inc. The Company controls an entity when it is exposed to, or has rights to, variable returns from its involvement with the entity and has the ability to affect those returns through its power over the entity. The financial statements of subsidiaries are included in the consolidated financial statements from the date on which control commences until the date on which control ceases. (ii) Loss of control When the Company loses control over a subsidiary, it derecognizes the assets and liabilities of the subsidiary, and any non-controlling (iii) Transactions eliminated on consolidation Intra-company balances and transactions, and any unrealized income and expenses arising from intra-company transactions, are eliminated. Unrealized gains arising from transactions with equity-accounted investees are eliminated against the investment to the extent of the Company’s interest in the investee. Unrealized losses are eliminated in the same way as unrealized gains, but only to the extent that there is no evidence of impairment.
Foreign Currency Transactions	Foreign Currency Transactions Foreign currency transactions are translated using the exchange rates at the dates of the transactions. Foreign exchange gains and losses resulting from the settlement of such transactions and from the translation of monetary assets and liabilities denominated in foreign currencies at the exchange rate at the reporting date are generally recognized in the statement of profit or loss and comprehensive loss as a component of finance costs. The results and financial position of foreign operations that have a functional currency different from the presentation currency are translated into the presentation currency as follows: • assets and liabilities for each balance sheet presented are translated at the closing rate at the date of that balance sheet; • income and expenses for each statement of profit or loss and comprehensive income or loss are translated at average exchange rates (unless this is not a reasonable approximation of the cumulative effect of the rates prevailing on the transaction dates, in which case income and expenses are translated at the exchange rates at the dates of the transactions); and • all resulting exchange differences are recognized in other comprehensive income.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are measured at cost less accumulated depreciation and accumulated impairment losses (if any). Cost includes expenditure that is directly attributable to the acquisition of the items. Depreciation of property, plant and equipment is recognized in the consolidated statement of profit and loss and comprehensive loss on a straight-line basis over estimated useful lives of generally five years, taking residual value into account. If significant parts of an item of property, plant and equipment have different useful lives, they are accounted for as separate items (major components) of property, plant and equipment. Subsequent expenditure is capitalized only when the expenditure will increase the future economic benefit of the asset. All other expenditures are expensed in the profit or loss and comprehensive loss. Depreciation rates are based on the following estimated economic useful lives of the tangible fixed assets concerned: • Plant and equipment: 5 years • Other fixed assets: 5 years
Intangible Assets	Intangible Assets Intangible assets are identifiable non-monetary The useful lives of intangible assets are assessed to be finite and amortized over the useful economic life and assessed for impairment whenever there is an indication that the intangible asset may be impaired. Amortization begins when the asset is available for use. Patents Patents acquired separately by the Company are reported at cost less accumulated amortization and accumulated impairment losses. Amortization is recognized in the consolidated statement of profit and loss and comprehensive loss on a straight-line basis over the shorter of their estimated economic or legal lives. The estimated useful life and amortization method are reviewed at the end of each annual reporting period, with the effect of any changes in estimates being accounted for on a prospective basis. Research and Development The Company incurs research and development expenses related to its clinical trials and preclinical drug development programs. Development expenses are defined as expenses incurred to achieve technical and commercial feasibility. Expenditure on research activities is recognized as an expense in the period in which it is incurred. Development is capitalized 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.
Financial Instruments	Financial Instruments The Company classifies non-derivative non-derivative Non-Derivative The Company initially recognizes receivables and investments at fair value on the date when they are originated. Subsequent to initial recognition, they are measured at amortized cost using the effective interest rate method. All other financial assets and financial liabilities are initially recognized on the trade date. The Company derecognizes a financial asset when the contractual rights to the cash flows from the asset expire, or it transfers the rights to receive the contractual cash flows in a transaction in which substantially all the risks and rewards of ownership of the financial asset are transferred, or it neither transfers nor retains substantially all of the risks and rewards of ownership and does not retain control over the transferred asset. Any interest in such derecognized financial assets that is created or retained by the Company is recognized as a separate asset or liability. The Company derecognizes a financial liability when its contractual obligations are settled or cancelled, or expire. Financial assets and financial liabilities are offset and the net amount presented in the statement of financial position when, and only when, the Company has a legal right to offset the amounts and intends either to settle them on a net basis or to realize the asset and settle the liability simultaneously. Receivables These assets are initially recognized at fair value plus any directly attributable transaction costs. Derivative Financial Assets and Liabilities Derivative financial instruments are initially recognized at fair value on the date on which a derivative contract is entered into and are subsequently remeasured at fair value with net changes in fair value presented as finance expenses (negative net changes in fair value) or finance income (positive net changes in fair value) in the consolidated statement of profit or loss and comprehensive loss. Derivatives are carried as financial assets when the fair value is positive and as financial liabilities when the fair value is negative. Derivatives embedded in host contracts are accounted for as separate derivatives and recorded at fair value if their economic characteristics and risks are not closely related to those of the host contracts and the host contracts are not held for trading or designated at fair value through profit or loss. These embedded derivatives are measured at fair value with changes in fair value recognized in profit or loss. Reassessment only occurs if there is either a change in the terms of the contract that significantly modifies the cash flows that would otherwise be required or a reclassification of a financial asset out of the fair value through profit or loss category. Non-Derivative Non-derivative
Investments	Investments Investments are classified as held-to-maturity held-to-maturity
Cash and Cash Equivalents	Cash and Cash Equivalents For the purpose of presentation in the statement of cash flows as well as the statement of financial position, cash and cash equivalents includes deposits held with financial institutions with original maturities of less than three months.
Provisions	Provisions A provision is recognized if the following applies: • the company has a legal or constructive obligation, arising from a past event; • the amount can be estimated reliably; and • it is probable that an outflow of resources embodying economic benefits will be required to settle the obligation. If all or part of the payments that are necessary to settle a provision are virtually certain to be fully or partially compensated by a third party upon settlement of the provision, then the compensation amount is presented separately as an asset. Provisions are determined by discounting the expected future cash flows at a pre-tax
Impairment	Impairment Financial Assets Measured at Amortized Cost The Company considers evidence of impairment for these assets at both an individual asset and a collective level. All individually significant assets are individually assessed for impairment. Those found not to be impaired are then collectively assessed for any impairment that has been incurred but not yet individually identified. Assets that are not individually significant are collectively assessed for impairment. Collective assessment is carried out by grouping together assets with similar risk characteristics. In assessing collective impairment, the Company uses historical information on the timing of recoveries and the amount of loss incurred, and makes an adjustment if current economic and credit conditions are such that the actual losses are likely to be greater or lesser than suggested by historical trends. An impairment loss is calculated as the difference between an asset’s carrying amount and the present value of the estimated future cash flows discounted at the asset’s original effective interest rate. Losses are recognized in the consolidated statement of profit or loss and comprehensive income and reflected in an allowance account. When the Company considers that there are no realistic prospects of recovery of the asset, the relevant amounts are written off. If the amount of impairment loss subsequently decreases and the decrease can be related objectively to an event occurring after the impairment was recognized, then the previously recognized impairment loss is reversed through profit or loss. Non-Financial At each reporting date, the Company reviews the carrying amounts of its non-financial For impairment testing, assets are grouped together into the smallest group of assets that generates cash inflows from continuing use that are largely independent of the cash inflows of other assets or cash generating units (“CGU”). The recoverable amount of an asset or CGU is the greater of its value in use and its fair value less costs to sell. Value in use is based on the estimated future cash flows, discounted to their present value using a pre-tax An impairment loss is recognized if the carrying amount of an asset or CGU exceeds its recoverable amount. Impairment losses are recognized in profit or loss. They are allocated first to reduce the carrying amount of any goodwill allocated to the CGU, and then to reduce the carrying amounts of the other assets in the CGU on a pro rata basis. An impairment loss is reversed only to the extent that the asset’s carrying amount does not exceed the carrying amount that would have been determined, net of depreciation or amortization, if no impairment loss had been recognized.
Revenue Recognition	Revenue Recognition Revenue is recognized to the extent that it is probable that the economic benefits will flow to the Company and the revenue can be reliably measured. Up-front The Company maintains research and license agreements with ONO and Incyte. In connection with these arrangements, the Company received upfront fees, which relate to the integrated package of deliverables under the contract (one single performance obligation) and are initially recorded in deferred revenue. The applicable period over which to recognize the upfront payment is a significant judgment. Up-front non-refundable re-assessed Collaboration Income Collaboration income, which is typically related to reimbursements from collaborators for the Company’s performance of research and development services under the respective agreements, is recognized on the basis of labor hours valued at a contractually agreed rate. Collaboration income includes reimbursements for related out-of-pocket Government Grants The Company receives certain government and regional grants, which support its research efforts in defined projects, and include contributions towards the cost of research and development. When there is reasonable assurance that the Company will comply with the conditions attached to a received grant, and when there is reasonable assurance that the grant will be received, government grants are recognized as revenue on a gross basis in the consolidated statement of profit or loss and comprehensive loss on a systematic basis over the periods in which the entity recognizes expenses for the related costs for which the grants are intended to compensate. In the case of grants related to assets, the received grant will be deducted from the carrying amount of the asset. Research and development expenses Research and development expenses represent costs which primarily include (i.) payroll and related costs (including share-based payment expenses) associated with research and development personnel, (ii.) costs related to clinical trials and preclinical testing of the Company’s technologies under development, (iii.) costs to develop product candidates, including raw materials and supplies, product testing, depreciation, and facility related expenses, (iv.) expenses for research services provided by universities and contract laboratories, and (v.) other research and development expenses. Research and development expenses are recognized in the consolidated statement of profit or loss and comprehensive loss as incurred when these expenditures relate to the Company’s research and development services and have no alternative future uses. The Company has entered into various research and development contracts with research institutions and other companies. These agreements are generally cancelable. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates may be made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs. WBSO The WBSO ( afdrachtvermindering speur- en ontwikkelingswerk
Employee Benefits	Employee Benefits Short-term Employee Benefits Short-term employee benefits are expensed as the related service is provided. A liability is recognized for the amount expected to be paid if the Company has a present legal or constructive obligation to pay this amount as a result of past service provided by the employee and the obligation can be estimated reliably. Share-Based Payment Transactions The grant-date fair value of equity-settled share-based payment awards granted to employees including grants of employee options, restricted share units, and modifications to existing instruments, is recognized as an expense, net of an estimated forfeiture rate, with a corresponding increase in equity (accumulated loss), over the vesting period of the awards. Forfeitures of employee options are recognized as they occur. Service conditions and non-market non-market non-market non-vesting true-up Post-Employment Benefit Plans The Company contributes to a post-employment benefit plan that entitles directors, executive officers and other staff members to retire at the age of 67 and receive annual payments based upon the average salary earned during the service period. The Company has insured the liabilities from the post-employment benefit plan with an insurance company and has no other obligation than to pay the annual insurance premiums to the insurance company. The annual pension payments are conditional; the Company will have no further obligation (legal or constructive) to pay further amounts if the insurance fund has insufficient assets to pay all employee benefits relating to current and prior service. Based on its characteristics the Company’s post-employment benefit plan is classified as a defined contribution plan. Obligations for contributions to defined contribution plans are expensed as the related service is provided. Prepaid contributions are recognized as an asset.
Leases	Leases Determining whether an Arrangement Contains a Lease At inception of an arrangement, the Company determines whether such an arrangement is or contains a lease. At inception or on reassessment of the arrangement, the Company separates payments and other consideration required by such an arrangement into those for the lease and those for other elements on the basis of their relative fair values. If the Company concludes for a finance lease that it is impracticable to separate the payments reliably, then an asset and a liability are recognized at an amount equal to the fair value of the underlying asset. Subsequently the liability is reduced as payments are made and an imputed finance cost on the liability is recognized using the Company’s incremental borrowing rate. Leased Assets Assets held by the Company under leases that transfer to the Company substantially all of the risks and rewards of ownership are classified as finance leases. The leased assets are measured initially at an amount equal to the lower of their fair value and the present value of the minimum lease payments. Subsequent to initial recognition, the assets are accounted for in accordance with the accounting policy applicable to that asset. Assets held under other leases are classified as operating leases and are not recognized in the Company’s statement of financial position. Lease Payments Payments made under operating leases are recognized in the consolidated statement of profit or loss and comprehensive loss on a straight-line basis over the term of the lease. Lease incentives received are recognized as an integral part of the total lease expense, over the term of the lease. Minimum lease payments made under finance leases are apportioned between the finance expense and the reduction of the outstanding liability. The finance expense is allocated to each period during the lease term so as to produce a constant periodic rate of interest on the remaining balance of the liability.
Finance Income and Finance Expenses	Finance Income and Finance Expenses The Company’s finance income and finance expenses include: • interest and related income; • interest expense and changes in fair value of the forward contract (derivative); • financing costs; and • the foreign currency gain or loss on financial assets and financial liabilities. Interest income or expense is recognized using the effective interest method.

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
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Schedule of Changes in Property, Plant and Equipment	Movements in property, plant and equipment were as follows: Plant and equipment Other fixed assets Total (euros in thousands) Balance as at January 1, 2016 Costs 325 1,220 1,545 Accumulated depreciation (171 ) (1,049 ) (1,220 ) Book value 154 171 325 Changes in book value Additions 330 166 496 Depreciation (56 ) (117 ) (173 ) Disposals (Cost) (6 ) — (6 ) Disposals (Accumulated depreciation) 6 — 6 Balance 274 49 323 Balance as at December 31, 2016 Costs 649 1,386 2,035 Accumulated depreciation (221 ) (1,166 ) (1,387 ) Book value 428 220 648 Changes in book value Additions 663 113 776 Depreciation (186 ) (70 ) (256 ) Disposals (Cost) (51 ) (1,086 ) (1,137 ) Disposals (Accumulated depreciation) 51 1,086 1,137 Balance 477 43 520 Balance as at December 31, 2017 Costs 1,261 413 1,674 Accumulated depreciation (356 ) (150 ) (506 ) Book value 905 263 1,168

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Movements of Intellectual Property Right	The intangible assets relate to acquired intellectual property rights. The movements are as follows: 2017 2016 (euros in thousands) Balance as at January 1 Historical cost 860 860 Accumulated amortization (486 ) (425 ) Book value 374 435 Capital expenditures — — Amortization charge for the year (62 ) (61 ) Book value as at December 31 312 374 Balance as at December 31 Historical cost 860 860 Accumulated amortization (548 ) (486 ) Book value 312 374

Financial assets (Tables)

Financial assets (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Investments	Investments as of December 31, 2017 consist of the following: (euros in thousands) Commercial paper 15,527 U.S. Treasury securities 9,177 Corporate fixed income bonds 7,886 Agency bond 1,453 Investments, current portion 34,043 Corporate fixed income bonds 7,060 Non-current 7,060 Total investments 41,103

Trade and Other Receivables (Ta

Trade and Other Receivables (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Trade and Other Receivables Due Within 1 Year	Balance per December 31 2017 2016 (euros in thousands) Trade receivables 1,594 205 Unbilled receivables 710 — VAT receivable 582 782 Prepaid general expenses 427 382 Prepaid pension costs 838 463 Prepaid share issuance costs — 230 Interest bank 170 32 Other receivables 92 154 4,413 2,248

Other Liabilities and Accruals

Other Liabilities and Accruals (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Short-term and Payable Within 1 Year	Balance per December 31 2017 2016 (euros in thousands) Accrued auditor’s fee 96 282 Personnel 446 220 Research and development costs 5,272 1,256 IP—Legal fee 509 114 Bonuses 1,545 768 Subsidy advance received 224 224 Other accruals 535 786 8,627 3,650

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Movements in Company's Borrowings with Rabobank	Movements in the Company’s borrowings with the Rabobank were as follows: (euros in thousands) Balance December 31, 2016 486 Short term portion December 31, 2016 167 Long term portion December 31, 2016 319 Balance January 1, 2017 486 Repayments (486 ) Balance December 31, 2017 —

Deferred Revenue (Tables)

Deferred Revenue (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Deferred Revenue	Deferred revenue is as follows: Balance per December 31 (euros in thousands) 2017 2016 Deferred revenue—current portion 6,996 1,610 Deferred revenue 130,195 30,206 137,191 31,816

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Number of Share Options Outstanding	The number of options outstanding, by group of employees, was as follows: Group of employees entitled December 31, 2017 December 31, 2016 December 31, 2015 Key management personnel 1,777,437 1,302,417 857,318 All other employees 436,548 92,427 96,371 Total 2,213,985 1,394,844 953,689
Summary of Inputs Used in the Measurement of the Fair Values and the Related Fair Values at the Grant Dates	2017 2016 2015 Key Management All Other Key Management All Other Key All Other € € € € € € Fair value at grant date 9.04 – 16.10 8.94 – 18.02 9.97 – 11.03 5.74 – 5.79 3.98 – 5.76 4.03 – 5.06 Share price at grant date 17.08 – 24.54 13.71 – 27.47 15.24 – 16.85 8.46 – 8.87 6.12 – 7.20 5.94 – 7.20 Exercise price 17.08 – 24.54 13.71 – 27.47 15.24 – 16.85 8.46 – 8.87 1.93 – 7.20 1.93 – 7.20 Expected volatility (weighted-average) 95.05% 94.88% 95.30% 97.15% 94.85% 94.85% Expected life 10 years 10 years 10 years 8 – 10 years 4 years 8 years Expected dividends 0% 0% 0% 0% 0% 0% Risk-free interest rate (based on government bonds) 2.29% – 2.51% 2.24% – 2.62% 1.84% – 1.86% 0.10% – 1.87% 0.16% – 0.70% 0.16% – 0.70%
Summary of Reconciliation of Outstanding Share Options	Reconciliation of outstanding share options and RSU’s 2017 2016 2015 Weighted Number of Weighted Number of Weighted Number of (€) (€) (€) Outstanding at January 1 8.69 1,394,844 5.35 953,689 5.15 192,276 Forfeited during the year 17.27 (58,164 ) 6.07 (31,351 ) 1.93 (1,033 ) Expired during the year 8.67 (762 ) 11.95 (5,454 ) 4.18 (9,216 ) Exercised during the year 2.24 (136,666 ) 1.93 (18,283 ) — — Granted during the year 19.88 1,014,733 14.74 496,243 5.99 771,662 Outstanding at December 31 13.99 2,213,985 8.69 1,394,844 5.35 953,689 Exercisable at December 31 687,070 418,453 157,562
Summary of Reconciliation of RSU's	RSU’s are summarized as follows: 2017 Weighted average exercise price Number of RSU’s (€) Outstanding at January 1 — — Forfeited during the year 20.03 (12,219 ) Expired during the year — — Vested during the year 20.03 (7,331 ) Granted during the year 20.03 214,096 Outstanding at December 31 20.03 194,546

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Revenue	(euros in thousands) 2017 2016 2015 Up-front 6,616 223 223 Collaboration income 5,789 1,109 1,092 Income from grants on research projects 1,195 1,387 662 13,600 2,719 1,977

Total Operating Expenses (Table

Total Operating Expenses (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Total Operating Expenses	2017 2016 2015 (Euros in thousands) Manufacturing costs 13,567 3,162 5,878 IP and license costs 1,858 1,167 1,112 Personnel related R&D 6,673 3,285 2,997 Other research and development costs 12,027 10,810 6,194 Total research and development costs 34,125 18,424 16,181 Management and administration costs 13,697 4,258 768 Litigation costs 1,039 1,490 4,419 Other operating expenses 8,356 6,219 3,648 Total other expenses 9,395 7,709 8,067 Total operating expenses 57,217 30,391 25,016
Breakdown of Other Research and Development Costs	A breakdown of other research and development costs is presented as follows: 2017 2016 2015 (Euros in thousands) Discovery and pre-clinical 2,473 5,185 2,534 Clinical costs 5,919 3,409 1,883 Consumables 2,149 1,055 979 Other research and development costs 1,486 1,161 798 Total other research and development costs 12,027 10,810 6,194
Operating Expenses by Nature	Operating expenses presented by nature are outlined below: 2017 2016 2015 (Euros in thousands) Contract manufacturing 13,567 3,162 5,878 Other external and outsourced costs 22,333 18,885 15,012 Employee costs & related benefits 20,999 8,110 3,933 Depreciation and amortization 318 234 193 Total operating expenses 57,217 30,391 25,016

Employee Benefits (Tables)

Employee Benefits (Tables)	12 Months Ended
	Dec. 31, 2017
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Disclosure of Detailed Information About Employee Benefits	Details of the employee benefits are as follows: 2017 2016 2015 (Euros in thousands) Salaries and wages 9,556 5,166 3,204 WBSO subsidy (3,523 ) (1,721 ) (348 ) Social security premiums 621 382 238 Health insurance 222 27 31 Pension costs 652 507 241 Share-based payment expenses 12,815 3,307 567 Other personnel expense 656 442 — 20,999 8,110 3,933
Schedule of Share-based Compensation Expenses Recognized as Employee Benefit Expenses	Share-based payment expenses (see Note 14) were recognized as employee benefit expenses as follows: (euros in thousands) 2017 2016 2015 Research and development costs 3,245 703 168 Management and administration costs 8,942 2,037 230 Other expenses 628 567 169 12,815 3,307 567

Finance Income and Expense (Tab

Finance Income and Expense (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Finance Income and Expense	2017 2016 2015 (Euros in thousands) Interest and related income 1,112 88 50 Net loss on foreign exchange (19,449 ) (409 ) — Interest and other expenses (10,696 ) (19,235 ) (195 ) Financing costs (190 ) — — (29,223 ) (19,556 ) (145 )

Loss per share (Tables)

Loss per share (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Basic and Diluted Loss per Share	Basic loss per share is calculated by dividing the loss attributable to equity holders of the Company by the weighted average numbers of shares outstanding during the year. 2017 2016 2015 (Euros in thousands, except per share data) Loss attributable to equity holders of the Company (73,000 ) (47,220 ) (23,184 ) Weighted average number of shares 19,196,440 13,236,649 5,871,237 Basic (and diluted) loss per share (€ per share) (3.80 ) (3.57 ) (3.95 )

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Carrying Amount of Financial Assets Represents the Maximum Credit Exposure	The carrying amount of financial assets represents the maximum credit exposure. 2017 2016 (Euros in thousands) Financial Assets Financial asset (derivative) — 11,847 Trade and unbilled receivables 2,283 205 Investments 41,103 — Restricted cash — 167 Cash and cash equivalents 149,678 56,917 193,064 69,136
Summary of Aging of Trade and Unbilled Receivables	The aging of trade and unbilled receivables was as follows: 2017 2016 Balance per December 31 in thousands of euros Neither past due nor impaired 2,283 205 Past due — — 2,283 205
Summary of Contractual Maturities of Financial Liabilities	The amounts are gross and undiscounted, and include estimated interest payments and excluding the impact of netting agreements: December 31, 2017 Carrying amount Total < 12 months 1 - 2 years 2 - 5 years More than 5 years (Euros in thousands) Non-derivative Trade payables 2,855 2,855 2,855 — — — Other liabilities and accruals 6,176 6,176 6,176 — — — 9,031 9,031 9,031 — — — December 31, 2016 Carrying amount Total < 12 months 1 - 2 years 2 - 5 years More than 5 years (Euros in thousands) Non-derivative Secured bank loans 486 526 190 181 155 — Trade payables 2,298 2,298 2,298 — — — Other liabilities and accruals 3,679 3,679 3,679 — — — 6,463 6,503 6,167 181 155 —
Summary of Sensitivity Analysis for Change in Primary Currency Exposures	The following table provides a sensitivity analysis for a change in the primary currency exposure for the Company relating to monetary assets and liabilities denominated in USD as of December 31, 2017. The analysis shows the impact that a change in the exchange rate at that date would have on the Company’s total comprehensive loss: Financial Statement Line Item Exposure Balance (in Effect on profit before tax if USD Effect on profit before tax if USD Cash and cash equivalents 88,538 3,691 (3,691 ) Total investments 47,310 1,972 (1,972 ) Trade and other receivables 2,311 97 (97 ) Trade payables, other liabilities and accruals (1,420 ) (59 ) 59 Net Assets 136,739 5,701 (5,701 )
Summary of Interest Rate Profile of the Company's Interest-bearing Financial Instruments	The interest rate profile of the Company’s interest-bearing financial instruments is as follows: Carrying amount 2017 2016 Balance per December 31 in thousands of euros Fixed-rate instruments Investments 41,103 — Financial liabilities — (486 ) Variable rate instruments Cash and cash equivalents 149,678 56,917

Board Compensation and Key Ma45

Board Compensation and Key Management Personnel (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Profit and Loss Statement for the Remuneration of the Statutory Directors	In 2017, 2016, and 2015 the following amounts were charged to the consolidated statement of profit or loss and comprehensive loss for the remuneration of the statutory directors: December 31, Name Gross Salary Bonus Pension Option cost Total (Amounts in Euros) Ton Logtenberg, CEO 2017 432,782 337,945 51,528 4,675,590 5,497,845 2016 369,204 147,820 17,717 907,236 1,441,977 2015 236,032 89,072 18,591 1,910,204 2,253,899 Shelley Margetson(*), COO 2017 (**) 420,782 — 19,595 451,752 892,129 2016 198,987 84,000 6,152 164,547 453,686 2015 159,749 37,365 13,824 284,938 495,876 (*) Resigned as a statutory director of the Company effective as of May 24, 2017. (**) Gross salary includes severance payments totaling €257,260.
Summary of the Remuneration Received for Key Management Personnel	The remainder of the key management personnel has received the following remuneration for the year 2017. Remuneration 2017 2016 2015 (Amounts in Euros) Short term employment benefits 2,808,998 1,139,763 190,763 Post-employment benefits 108,416 18,720 11,671 Other long term benefits — — — Termination benefits — — — Share based payments 5,171,233 1,195,876 57,065 Total 8,088,647 2,354,359 259,499
Summary of Statement of Profit and Loss for the Remuneration of the(Former) Members of the Supervisory Board	The following amounts were charged to the consolidated statement of profit or loss and comprehensive loss for the remuneration of the members of the Board: December 31, 2017 December 31, 2016 December 31, 2015 Name Cash compensation Option Total Cash compensation Option Total Cash compensation Option Total (Amounts in Euros) (Amounts in Euros) (Amounts in Euros) Mark Iwicki 59,840 120,596 180,436 50,394 183,367 233,761 26,325 115,380 141,705 Wolfgang Berthold 37,530 90,944 128,474 19,850 50,928 70,778 — 15,475 15,475 Lionel Carnot 35,445 61,870 97,315 24,852 66,959 91,811 — — — John de Koning 38,573 113,613 152,186 26,230 37,000 63,230 — — — Anand Mehra 39,615 83,683 123,298 26,938 84,703 111,641 — — — Gregory Perry 41,700 103,169 144,869 28,356 97,365 125,721 — — — Gabriele Dallmann(*) — — — — — — 11,000 5,795 16,795 Gerard van Odijk(*) — — — — — — — 16,298 16,298 Total 252,703 573,875 826,578 176,620 520,322 696,942 37,235 152,948 190,273 (*) former board member
Summary of Average Exercise Price Per Share Held by the Members of the Supervisory Board	As at December 31, members of the Board held the following number of options: December 31, 2017 December 31, 2016 December, 31 2015 Name Number Weighted exercise price Number Weighted exercise price Number Weighted exercise price Mark Iwicki 79,226 € 7.32 73,576 € 6.57 73,576 € 6.57 Wolfgang Berthold 24,040 € 8.90 26,724 € 3.02 14,168 € 1.93 Lionel Carnot 22,650 € 11.80 17,000 € 8.87 — — John de Koning 22,650 € 11.80 17,000 € 8.87 — — Anand Mehra 22,650 € 11.80 17,000 € 8.87 — — Gregory Perry 22,650 € 11.80 17,000 € 8.87 — — Gabriele Dallmann(*) — — 16,828 € 3.24 4,272 € 1.93 Gerard van Odijk(*) — — — — 21,874 € 1.93 Total 193,866 € 9.61 185,128 € 7.21 113,890 € 4.93 (*) former board member

Operating leases (Tables)

Operating leases (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Schedule of Future Minimum Lease Payments Under Lease	Future minimum lease payments under this lease as at December 31, 2017 are payable as follows: Less than one year 602 Between one and five years 1,897 More than five years — Total 2,499

General Information - Additiona

General Information - Additional Information (Detail) € in Thousands, $ in Millions	Feb. 13, 2018USD ($)	Feb. 28, 2018USD ($)	Jan. 31, 2017USD ($)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)	Dec. 31, 2015EUR (€)	Dec. 31, 2014EUR (€)
Disclosure of general information [line items]
Cash and cash equivalents				€ 149,678	€ 56,917	€ 32,851	€ 1,568
Investments				41,103
Proceeds from issuance			$ 80	€ 74,738	€ 50,547	€ 46,478
Potential ordinary share transactions [member]
Disclosure of general information [line items]
Proceeds from issuance | $	$ 55.8	$ 55.8

Basis of Preparation - Addition

Basis of Preparation - Additional Information (Detail) € / shares in Units, $ / shares in Units, € in Thousands, $ in Millions

Feb. 13, 2018USD ($)$ / shares

Jan. 23, 2017EUR (€)

Jan. 23, 2017USD ($)$ / sharesshares

Dec. 20, 2016USD ($)$ / sharesshares

May 26, 2016USD ($)$ / sharesshares

May 06, 2016

Feb. 28, 2018USD ($)

Jan. 31, 2017USD ($)

Dec. 31, 2017EUR (€)

Dec. 31, 2016EUR (€)

Dec. 31, 2015EUR (€)€ / shares

Feb. 13, 2018€ / sharesshares

Jun. 01, 2017USD ($)shares

May 24, 2016shares

Disclosure Of Basis Of Preparation [Line Items]

Statement of IFRS compliance

These consolidated financial statements ("the financial statements") have been prepared in accordance with International Financial Reporting Standards ("IFRS") as issued by the International Accounting Standards Board.

Reverse share split

0.5556

Issue price per share | € / shares

€ 0.09

Aggregate purchase price

$ 80

€ 74,738

€ 50,547

€ 46,478

Description of presentation currency

The financial statements are presented in euros, which is the Company's functional and presentation currency.

Level of rounding used in financial statements

All amounts are rounded to the nearest thousands of euros, except as otherwise indicated.

Potential ordinary share transactions [member]

Disclosure Of Basis Of Preparation [Line Items]

Common shares issued

3,099,997

Issue price per share | € / shares

€ 0.09

Aggregate purchase price | $

$ 55.8

$ 55.8

Purchase price | $ / shares

$ 18

Incyte Corporation [member]

Disclosure Of Basis Of Preparation [Line Items]

Common shares issued

3,200,000

3,200,000

3,200,000

Issue price per share | $ / shares

$ 25

Aggregate purchase price

€ 74,700

$ 80

$ 80

Securities registered | $

$ 250

Purchase price | $ / shares

$ 25

Cowen and Company LLC [member]

Disclosure Of Basis Of Preparation [Line Items]

Common shares issuable

50,000,000

Aggregate compensation payable, percent

3.00%

Initial public offering [member]

Disclosure Of Basis Of Preparation [Line Items]

Common shares issued

5,500,000

Issue price per share | $ / shares

$ 10

Aggregate purchase price | $

$ 53.3

Over allotment option [member]

Disclosure Of Basis Of Preparation [Line Items]

Common shares issued

639,926

Significant Accounting Polici49

Significant Accounting Policies - Additional Information (Detail) € in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017EUR (€)yr	Dec. 31, 2016USD ($)	Dec. 31, 2015EUR (€)
Disclosure of significant accounting policies [line items]
Estimated useful lives	Five years
Cash and cash equivalents, maximum original maturities	3 months
Prepaid share issue related costs	€ 0.2	$ 1.5	€ 0.8
Retirement age	67
Plant and equipment [member]
Disclosure of significant accounting policies [line items]
Estimated useful lives	5 years
Other fixed assets [member]
Disclosure of significant accounting policies [line items]
Estimated useful lives	5 years

New Standards and Interpretat50

New Standards and Interpretations Not Yet Adopted - Additional Information (Detail) - EUR (€) € in Millions	Apr. 08, 2014	Dec. 31, 2018	Dec. 31, 2017
Disclosure of deferred income [line items]
Amortization of additional revenue			€ 8.3
IFRS 15 revenue from contracts with customers [member]
Disclosure of deferred income [line items]
Decrease in Deferred revenue		€ 8.9
Incyte Corporation [member]
Disclosure of deferred income [line items]
Estimated amortization period			21 years
ONO Research and License Agreement [member]
Disclosure of deferred income [line items]
Estimated amortization period	4 years 6 months		4 years 6 months

Segment Reporting - Additional

Segment Reporting - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017Segment
Disclosure of operating segments [abstract]
Number of reportable segment	1

Property, Plant and Equipment -

Property, Plant and Equipment - Schedule of Changes in Property, Plant and Equipment (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment, beginning balance	€ 648	€ 325
Changes in book value
Additions	776	496
Depreciation	(256)	(173)
Disposals (Cost)	(1,137)	(6)
Disposals (Accumulated depreciation)	1,137	6
Change in book value	520	323
Property, plant and equipment, ending balance	1,168	648
Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment, beginning balance	2,035	1,545
Changes in book value
Property, plant and equipment, ending balance	1,674	2,035
Accumulated depreciation and amortisation [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment, beginning balance	(1,387)	1,220
Changes in book value
Property, plant and equipment, ending balance	506	(1,387)
Plant and equipment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment, beginning balance	428	154
Changes in book value
Additions	663	330
Depreciation	(186)	(56)
Disposals (Cost)	(51)	(6)
Disposals (Accumulated depreciation)	51	6
Change in book value	477	274
Property, plant and equipment, ending balance	905	428
Plant and equipment [member] | Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment, beginning balance	649	325
Changes in book value
Property, plant and equipment, ending balance	1,261	649
Plant and equipment [member] | Accumulated depreciation and amortisation [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment, beginning balance	(221)	171
Changes in book value
Property, plant and equipment, ending balance	356	(221)
Other fixed assets [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment, beginning balance	220	171
Changes in book value
Additions	113	166
Depreciation	(70)	(117)
Disposals (Cost)	(1,086)
Disposals (Accumulated depreciation)	1,086
Change in book value	43	49
Property, plant and equipment, ending balance	263	220
Other fixed assets [member] | Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment, beginning balance	1,386	1,220
Changes in book value
Property, plant and equipment, ending balance	413	1,386
Other fixed assets [member] | Accumulated depreciation and amortisation [member]
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment, beginning balance	(1,166)	1,049
Changes in book value
Property, plant and equipment, ending balance	€ 150	€ (1,166)

Intangible Assets - Summary of

Intangible Assets - Summary of Movements of Intellectual Property Right (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about intangible assets [line items]
Intangible assets, beginning balance	€ 374	€ 435
Capital expenditures	0	0
Amortization charge for the year	(62)	(61)
Intangible assets, ending balance	312	374
Gross carrying amount [member]
Disclosure of detailed information about intangible assets [line items]
Intangible assets, beginning balance	860	860
Intangible assets, ending balance	860	860
Accumulated amortization [member]
Disclosure of detailed information about intangible assets [line items]
Intangible assets, beginning balance	(486)	(425)
Intangible assets, ending balance	€ (548)	€ (486)

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017
Copyrights, patents and other industrial property rights, service and operating rights [member]
Disclosure of detailed information about intangible assets [line items]
Economic life of patents, description	On January 23, 2009, the Company purchased the family of patents and future filings based on those patents, entitled “Recombinant production of mixtures of antibodies” from Crucell Holland B.V. The non-provisional filing date for this application was on July 15, 2003 and accordingly applications stemming from that patent family have an approximate economic life of 20 years from that date, not including patent term adjustment, extensions or any related doctrine. As a result, the Company is amortizing the cost over the approximate economic life of 14 years after acquisition of the patent family.

Taxation - Additional Informati

Taxation - Additional Information (Detail) - EUR (€)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Deferred tax assets	€ 0
Income tax expenses	€ 249,000
Netherlands [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Percentage of income tax rate effectively owed	75.00%
Tax rate	5.00%
Estimated effective tax rate	25.00%
Income tax expenses	€ 0
United States [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax rate	40.00%	40.00%
Income tax expenses	€ 200,000	€ 0
Unused tax losses [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax losses carried forward	€ 149,200,000	€ 101,100,000

Financial Assets - Additional I

Financial Assets - Additional Information (Detail) - EUR (€) € in Thousands	Jan. 23, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Disclosure of financial assets [line items]
Fair value of derivative				€ 11,800
Purchases of investments		€ 41,800	€ 41,830
Unrealized exchanges losses		€ (800)	€ 15,767	€ 365
Forward contract [member]
Disclosure of financial assets [line items]
Extinguishment of financial asset	€ 10,700
Change in fair value asset and discount on share	€ 1,100

Financial Assets - Summary of I

Financial Assets - Summary of Investments (Detail) € in Thousands	Dec. 31, 2017EUR (€)
Disclosure of financial assets [line items]
Investments, current portion	€ 34,043
Non-current investments	7,060
Total investments	41,103
Commercial paper [member]
Disclosure of financial assets [line items]
Investments, current portion	15,527
U.S. Treasury securities [member]
Disclosure of financial assets [line items]
Investments, current portion	9,177
Corporate fixed income bonds [member]
Disclosure of financial assets [line items]
Investments, current portion	7,886
Non-current investments	7,060
Agency bond [member]
Disclosure of financial assets [line items]
Investments, current portion	€ 1,453

Trade and Other Receivables - S

Trade and Other Receivables - Summary of Trade and Other Receivables Due Within 1 Year (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016
Subclassifications of assets, liabilities and equities [abstract]
Trade receivables	€ 1,594	€ 205
Unbilled receivables	710
VAT receivable	582	782
Prepaid general expenses	427	382
Prepaid pension costs	838	463
Prepaid share issuance costs		230
Interest bank	170	32
Other receivables	92	154
Total	€ 4,413	€ 2,248

Other Liabilities ans Accruals

Other Liabilities ans Accruals - Summary of Short-term and Payable Within 1 Year (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016
Disclosure of accruals and other payables [Abstract]
Accrued auditor's fee	€ 96	€ 282
Personnel	446	220
Research and development costs	5,272	1,256
IP-Legal fee	509	114
Bonuses	1,545	768
Subsidy advance received	224	224
Other accruals	535	786
Total	€ 8,627	€ 3,650

Borrowings - Additional Informa

Borrowings - Additional Information (Detail) - EUR (€) € in Thousands	Mar. 31, 2017	Jan. 31, 2009	Dec. 29, 2005	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Apr. 01, 2016
Disclosure of detailed information about borrowings [line items]
Total borrowings					€ 486
Repayment of loan in monthly installment		€ 14
Annual interest rate	3.55%						4.45%
Repayment of borrowings	€ 486			€ 486	€ 167	€ 166
Bank borrowings [member]
Disclosure of detailed information about borrowings [line items]
Total borrowings			€ 1,500
Duration of the agreement			12 years

Borrowings - Summary of Movemen

Borrowings - Summary of Movements in the Company's Borrowings With the Rabobank (Detail) - EUR (€) € in Thousands	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016
Borrowings [abstract]
Borrowings		€ 486
Borrowings		486	€ 486		€ 486
Repayments	€ (486)	€ (486)	(167)	€ (166)
Short term borrowings					167
Borrowings			€ 486
Long term borrowings					€ 319

Deferred Revenue - Summary of D

Deferred Revenue - Summary of Deferred Revenue (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016
Disclosure of deferred income [abstract]
Deferred revenue-current portion	€ 6,996	€ 1,610
Deferred revenue	130,195	30,206
Total deferred revenue	€ 137,191	€ 31,816

Deferred Revenue - Additional I

Deferred Revenue - Additional Information (Detail) $ / shares in Units, € in Thousands, $ in Millions	Feb. 28, 2017USD ($)	Jan. 23, 2017EUR (€)shares	Jan. 23, 2017USD ($)shares	Dec. 20, 2016USD ($)$ / sharesshares	Apr. 08, 2014EUR (€)	Jan. 31, 2017USD ($)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)	Dec. 31, 2015EUR (€)	Jun. 01, 2017shares
Disclosure of deferred income [line items]
Total deferred revenue							€ 137,191	€ 31,816
Non-refundable upfront payment received | $	$ 120
Aggregate purchase price						$ 80	€ 74,738	50,547	€ 46,478
Percentage of global development costs							35.00%
Percentage share in profit and losses							50.00%
Sales milestones payment							€ 350,000
Milestone opportunity							€ 2,800,000
Bottom of range [member]
Disclosure of deferred income [line items]
Percentage of royalty payable							6.00%
Royalties percentage							6.00%
Top of range [member]
Disclosure of deferred income [line items]
Percentage of royalty payable							10.00%
Royalties percentage							10.00%
Incyte Corporation [member]
Disclosure of deferred income [line items]
Non-refundable upfront payment receivable | $				$ 120
Common shares issued | shares		3,200,000	3,200,000	3,200,000						3,200,000
Purchase price per share | $ / shares				$ 25
Aggregate purchase price		€ 74,700	$ 80	$ 80
Estimated amortization period							21 years
Incyte collaboration agreement [member]
Disclosure of deferred income [line items]
Total deferred revenue							€ 137,000	31,400
ONO Research and License Agreement [member]
Disclosure of deferred income [line items]
Total deferred revenue							€ 200	€ 400
Estimated amortization period					4 years 6 months		4 years 6 months
Non-refundable upfront payment received					€ 1,000

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Detail) € / shares in Units, $ / shares in Units, $ in Millions	Jan. 23, 2017EUR (€)shares	Jan. 23, 2017USD ($)	Dec. 20, 2016USD ($)shares	Jan. 31, 2017USD ($)	Dec. 31, 2017EUR (€)yrshares	Dec. 31, 2016EUR (€)yrshares	Dec. 31, 2015EUR (€)yr€ / sharesshares	Jun. 01, 2017shares	Jan. 23, 2017$ / shares	Dec. 31, 2016USD ($)yrshares	Dec. 31, 2014
Disclosure of terms and conditions of share-based payment arrangement [line items]
Issue price per share | € / shares							€ 0.09
Aggregate purchase price				$ 80	€ 74,738,000	€ 50,547,000	€ 46,478,000
Issuance costs					200,000		€ 800,000			$ 1.5
Increased capital					12,960	1,645
Increased premium					€ 293,660	€ 33,641
Number of share options exercised					136,666	18,283	0
Weighted average exercise price					€ 2.24	€ 1.93
Number of shares fully issued and paid | shares					143,997	18,283				18,283
Number of Restricted Stock Units vested					7,331
Share conversion basis					One-for-one conversion
Description of share conversion basis					The conversion ratio was a one-for-one conversion, taking into consideration the reverse share split that became effective on May 6, 2016.
Description of depository based exercise price					Prior to the IPO, participants that voluntarily left the Company, except for members of the former Supervisory Board, were required to offer to the foundation the depositary receipts acquired from exercising options against payment of the exercise price or the lower fair market value of the underlying shares.
Description of non-vesting condition					This obligation for a participant to offer depositary receipts to the foundation upon resignation within four years from exercising the options was treated as a non-marketvesting condition.
Period of option to exercise treated as non-vesting condition					Within four years
Number of share options outstanding in share-based payment arrangement					2,213,985	1,394,844	953,689			1,394,844	192,276
Weighted average exercise price					€ 13.99	€ 8.69	€ 5.35
Weighted-average remaining contractual life | yr					8.25	6.68	3.63			6.68
Weighted-average share price at the date of exercise for share options exercised					€ 20.69
Top of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Weighted average exercise price					27.47	€ 16.85	€ 13.50
Bottom of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Weighted average exercise price					€ 1.93	€ 1.93	€ 1.93
Incyte Corporation [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Common shares issued | shares	3,200,000		3,200,000					3,200,000
Issue price per share | $ / shares									$ 25
Aggregate purchase price	€ 74,700,000	$ 80	$ 80
Percentage of pre-transaction issued and outstanding common shares	19.90%	19.90%
Proceeds from net of issuance costs	€ 74,400,000
Issuance costs	200,000
Change in fair value asset and discount on share	1,100,000
Foreign currency translation	400,000
Increased capital	300,000
Increased premium	€ 73,400,000
Two Thousand Ten Option Plan[member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Description of options vested					Options granted under the 2010 Plan are exercisable once vested.
Vesting period					4 years
Percentage of initial vesting period					25.00%
Percentage of remaining vesting options					75.00%
Period of remaining option vesting period					36 monthly installments
Percentage of vesting period					100.00%
Description of option lapse					Options lapse on the eighth anniversary of the date of grant.
Description of depository based exercise price					The 2010 Option Plan was amended such that a participant is no longer required to offer depositary receipts to the foundation upon resignation.
Non-Executive Compensation Program [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Percentage of initial vesting period					33.00%
Percentage of remaining vesting options					67.00%
Period of remaining option vesting period					24 substantially equal monthly installments
Vesting period					Three year period
Period of option will be vested and exercised					12 substantially equal monthly installments
Description of grant award					Following the vesting commencement date, such that the subsequent award shall be fully vested on the first anniversary of the date of grant.
2016 Plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Description of options vested					Options granted under the 2016 Plan are exercisable once vested.
Vesting period					4 years
Percentage of initial vesting period					25.00%
Percentage of remaining vesting options					75.00%
Period of remaining option vesting period					36 monthly installments
Percentage of vesting period					100.00%
Description of option lapse					Options will lapse on the tenth anniversary of the date of grant.
Vesting period of Restricted Stock Units vested					4 years
Number of common share entitled to receive					1
Ordinary shares [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of shares fully issued and paid | shares					19,429,848	16,085,851	337,562			16,085,851
Class C preferred shares [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of shares fully issued and paid | shares							4,149,884
Class B Preferred Shares [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of shares fully issued and paid | shares							3,899,104
Class A Preferred Shares [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of shares fully issued and paid | shares							229,055

Shareholders' Equity - Summary

Shareholders' Equity - Summary of Number of Share Options Outstanding (Detail)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of outstanding share options	2,213,985	1,394,844	953,689	192,276
Key management personnel [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of outstanding share options	1,777,437	1,302,417	857,318
All other employees [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of outstanding share options	436,548	92,427	96,371

Shareholders' Equity - Summar66

Shareholders' Equity - Summary of Inputs Used in the Measurement of the Fair Values and the Related Fair Values at the Grant Dates (Detail) - € / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Key management personnel [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Expected volatility (weighted-average)	95.05%	95.30%	94.85%
Expected life	10 years	10 years	4 years
Expected dividends	0.00%	0.00%	0.00%
Key management personnel [member] | Bottom of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Fair value at grant date	€ 9.04	€ 9.97	€ 3.98
Share price at grant date	17.08	15.24	6.12
Exercise price	€ 17.08	€ 15.24	€ 1.93
Risk-free interest rate (based on government bonds)	2.29%	1.84%	0.16%
Key management personnel [member] | Top of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Fair value at grant date	€ 16.10	€ 11.03	€ 5.76
Share price at grant date	24.54	16.85	7.20
Exercise price	€ 24.54	€ 16.85	€ 7.20
Risk-free interest rate (based on government bonds)	2.51%	1.86%	0.70%
All other employees [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Expected volatility (weighted-average)	94.88%	97.15%	94.85%
Expected life	10 years		8 years
Expected dividends	0.00%	0.00%	0.00%
All other employees [member] | Bottom of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Fair value at grant date	€ 8.94	€ 5.74	€ 4.03
Share price at grant date	13.71	8.46	5.94
Exercise price	€ 13.71	€ 8.46	€ 1.93
Expected life		8 years
Risk-free interest rate (based on government bonds)	2.24%	0.10%	0.16%
All other employees [member] | Top of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Fair value at grant date	€ 18.02	€ 5.79	€ 5.06
Share price at grant date	27.47	8.87	7.20
Exercise price	€ 27.47	€ 8.87	€ 7.20
Expected life		10 years
Risk-free interest rate (based on government bonds)	2.62%	1.87%	0.70%

Shareholders' Equity - Summar67

Shareholders' Equity - Summary of Reconciliation of Outstanding Share Options (Detail)	12 Months Ended
	Dec. 31, 2017€ / shares	Dec. 31, 2016€ / shares	Dec. 31, 2015€ / shares
Disclosure of terms and conditions of share-based payment arrangement [abstract]
Outstanding at January 1	1,394,844	953,689	192,276
Forfeited during the year	(58,164)	(31,351)	(1,033)
Expired during the year	(762)	(5,454)	(9,216)
Exercised during the year	(136,666)	(18,283)	0
Granted during the year	1,014,733	496,243	771,662
Outstanding at December 31	2,213,985	1,394,844	953,689
Exercisable at December 31	687,070	418,453	157,562
Outstanding at January 1	€ 8.69	€ 5.35	€ 5.15
Forfeited during the year	17.27	6.07	1.93
Expired during the year	8.67	11.95	4.18
Exercised during the year	2.24	1.93
Granted during the year	19.88	14.74	5.99
Outstanding at December 31	€ 13.99	€ 8.69	€ 5.35

Shareholders' Equity - Summar68

Shareholders' Equity - Summary of Reconciliation of RSU's (Detail)	12 Months Ended
	Dec. 31, 2017EUR (€)
Disclosure of terms and conditions of share-based payment arrangement [abstract]
Forfeited during the year	€ 20.03
Expired during the year	0
Vested during the year	20.03
Granted during the year	20.03
Outstanding ending balance	€ 20.03
Forfeited during the year	(12,219)
Expired during the year	0
Vested during the year	(7,331)
Granted during the year	214,096
Outstanding ending balance	194,546

Revenue - Summary of Revenue (D

Revenue - Summary of Revenue (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue [line items]
Total Revenue	€ 13,600	€ 2,719	€ 1,977
Up-front payment amortization [member]
Revenue [line items]
Total Revenue	6,616	223	223
Collaboration income [member]
Revenue [line items]
Total Revenue	5,789	1,109	1,092
Income from grants on research projects [member]
Revenue [line items]
Total Revenue	€ 1,195	€ 1,387	€ 662

Revenue - Additional Informatio

Revenue - Additional Information (Detail) € in Thousands	Oct. 16, 2017EUR (€)	Jun. 12, 2017EUR (€)	Mar. 07, 2016EUR (€)	Nov. 30, 2017EUR (€)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)Milestone	Dec. 31, 2015EUR (€)
Revenue [line items]
Revenue					€ 13,600	€ 2,719	€ 1,977
Number of research milestone | Milestone						1
Grant income				€ 200	1,200	€ 1,400	700
Reimbursement of grant		€ 700
Remaining funds	€ 400
Amount remitted to other beneficiaries				€ 200
Collaboration income [member]
Revenue [line items]
Revenue					5,789	1,109	1,092
Incyte collaboration agreement [member]
Revenue [line items]
Up-front payment amortization					6,400
ONO Research and License Agreement [member]
Revenue [line items]
Up-front payment amortization					€ 200	200	200
Revenue			€ 400
Milestone revenue						€ 700	€ 1,100

Total Operating Expenses - Summ

Total Operating Expenses - Summary of Total Operating Expenses (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Operating Expenses [Abstract]
Manufacturing costs	€ 13,567	€ 3,162	€ 5,878
IP and license costs	1,858	1,167	1,112
Personnel related R&D	6,673	3,285	2,997
Other research and development costs	12,027	10,810	6,194
Total research and development costs	34,125	18,424	16,181
Management and administration costs	13,697	4,258	768
Litigation costs	1,039	1,490	4,419
Other operating expenses	8,356	6,219	3,648
Total other expenses	9,395	7,709	8,067
Total operating expenses	€ 57,217	€ 30,391	€ 25,016

Total Operating Expenses - Addi

Total Operating Expenses - Additional Information (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Operating Expenses [Abstract]
Research and development costs	€ 34,125	€ 18,424	€ 16,181
Expenses related to professional fees for consulting, audit, and tax services	4,000	1,700	1,000
General legal, insurance and facility related expenses	3,200	3,900	2,200
Litigation and opposition	1,000	1,500	4,400
Preclinical costs	2,500	5,200	2,500
Clinical costs	5,919	3,409	1,883
IP costs	€ 2,900	€ 2,700	€ 5,500

Total Operating Expenses - Brea

Total Operating Expenses - Breakdown of Other Research and Development Costs (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Operating Expenses [Abstract]
Discovery and pre-clinicalcosts	€ 2,473	€ 5,185	€ 2,534
Clinical costs	5,919	3,409	1,883
Consumables	2,149	1,055	979
Other research and development costs	1,486	1,161	798
Total other research and development costs	€ 12,027	€ 10,810	€ 6,194

Total Operating Expenses - Oper

Total Operating Expenses - Operating Expenses by Nature (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Operating Expenses [Abstract]
Contract manufacturing	€ 13,567	€ 3,162	€ 5,878
Other external and outsourced costs	22,333	18,885	15,012
Employee costs & related benefits	20,999	8,110	3,933
Depreciation and amortization	318	234	193
Total operating expenses	€ 57,217	€ 30,391	€ 25,016

Employee Benefits - Disclosure

Employee Benefits - Disclosure of Detailed Information About Employee Benefits (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Short-term employee benefits expense [abstract]
Salaries and wages	€ 9,556	€ 5,166	€ 3,204
WBSO subsidy	(3,523)	(1,721)	(348)
Social security premiums	621	382	238
Health insurance	222	27	31
Pension costs	652	507	241
Share-based payment expenses	12,815	3,307	567
Other personnel expense	656	442
Total	€ 20,999	€ 8,110	€ 3,933

Employee Benefits - Schedule of

Employee Benefits - Schedule of Share-based Compensation Expenses Recognized as Employee Benefit Expenses (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Share Of Equity Investment [Line Items]
Stock award expense	€ 12,815	€ 3,307	€ 567
Research and development costs [member]
Disclosure Of Share Of Equity Investment [Line Items]
Stock award expense	3,245	703	168
Management and administration costs [member]
Disclosure Of Share Of Equity Investment [Line Items]
Stock award expense	8,942	2,037	230
Other expenses [member]
Disclosure Of Share Of Equity Investment [Line Items]
Stock award expense	€ 628	€ 567	€ 169

Employee Benefits - Additional

Employee Benefits - Additional Information (Detail) € in Millions	12 Months Ended
	Dec. 31, 2017EUR (€)Employees	Dec. 31, 2016EUR (€)Employees	Dec. 31, 2015EUR (€)Employees
Disclosure of employee benefits [line Items]
Received and recognized subsidies | €	€ 3.5	€ 1.7	€ 0.3
Number of employees	21	11
Netherlands [member]
Disclosure of employee benefits [line Items]
Average number of employees	69	45	32
United States [member]
Disclosure of employee benefits [line Items]
Average number of employees	10	2

Finance Income and Expense - Su

Finance Income and Expense - Summary of Finance Income and Expense (Detail) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Rental expenses on real estate [Abstract]
Interest and related income	€ 1,112	€ 88	€ 50
Net loss on foreign exchange	(19,449)	(409)
Interest and other expenses	(10,696)	(19,235)	(195)
Financing costs	(190)
Total	€ (29,223)	€ (19,556)	€ (145)

Finance Income and Expense - Ad

Finance Income and Expense - Additional Information (Detail) € in Thousands, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017USD ($)	Dec. 31, 2017EUR (€)	Mar. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)	Mar. 31, 2016EUR (€)	Dec. 31, 2017USD ($)	Aug. 31, 2017USD ($)	Jan. 23, 2017EUR (€)	Dec. 31, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2015EUR (€)
Disclosure Of Deferred Tax Assets Notional Interest [line Items]
Net loss on foreign exchange		€ 19,449		€ 409
Loss in foreign currency denominated denominated cash, cash equivalents and investments		(14,423)	€ 19,400	€ 6	€ 400
Foreign currency denominated cash and cash equivalent accounts and investment | $	$ 98									$ 49.4
Revaluation of derivative		10,700
Prepaid share issue related costs		200							$ 1.5		€ 800
Incyte Corporation [member]
Disclosure Of Deferred Tax Assets Notional Interest [line Items]
Increase in cash, cash equivalents and investments | $	$ 200
Short-term investments with a one month maturity | $						$ 200
Amount of investment converted to other currency | $							$ 50.3
Net loss on foreign exchange		€ 4,400
Prepaid share issue related costs								€ 200

Loss per Shae - Summary of Basi

Loss per Shae - Summary of Basic and Diluted Loss per Share (Detail) - EUR (€) € / shares in Units, € in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings per share [abstract]
Loss attributable to equity holders of the Company		€ (73,000)	€ (47,220)	€ (23,184)
Weighted average number of shares		19,196,440	13,236,649	5,871,237
Basic (and diluted) loss per share	[1],[2]	€ (3.80)	€ (3.57)	€ (3.95)
[1]	For the periods included in these financial statements, the share options are not included in the diluted loss per share calculation as the Company was loss-making in all these periods. Due to the anti-dilutive nature of the outstanding options, basic and diluted loss per share is equal.
[2]	The basic (and diluted) loss per share is adjusted for the 2015 period based on the reverse share split with reference to note 14 regarding the capital reorganization.

Loss per share - Additional Inf

Loss per share - Additional Information (Detail)	Dec. 31, 2017EUR (€)
Earnings per share [abstract]
Dividend declared	€ 0

Financial Instrument - Summary

Financial Instrument - Summary of Maximum Credit Exposure (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fixed Rate of Instruments [Abstract]
Financial asset (derivative)		€ 11,847
Trade and unbilled receivables	€ 2,283	205
Investments	41,103
Restricted cash		167
Cash and cash equivalents	149,678	56,917	€ 32,851	€ 1,568
Maximum exposure to credit risk	€ 193,064	€ 69,136

Financial Instrument - Addition

Financial Instrument - Additional Information (Detail) - EUR (€)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about financial instruments [abstract]
Remaining fair value of the derivative		€ 11,847,000
Allowance for impairment	€ 0

Financial Instrument - Summar84

Financial Instrument - Summary of Aging of Trade and Unbilled Receivables (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016
Disclosure of financial assets that are either past due or impaired [line items]
Trade and unbilled receivables	€ 2,283	€ 205
Neither past due nor impaired [member]
Disclosure of financial assets that are either past due or impaired [line items]
Trade and unbilled receivables	€ 2,283	€ 205

Financial Instruments - Summary

Financial Instruments - Summary of Maturity Analysis For Nonderivative Financial Liabilities (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016
Non-derivative financial liabilities
Secured bank loans		€ 526
Trade payables	€ 2,855	2,298
Other liabilities and accruals	6,176	3,679
Non-derivative financial liabilities undiscounted cash flows	9,031	6,503
Carrying amount and value [member]
Non-derivative financial liabilities
Secured bank loans		486
Trade payables	2,855	2,298
Other liabilities and accruals	6,176	3,679
Non-derivative financial liabilities undiscounted cash flows	9,031	6,463
Less than one year [member]
Non-derivative financial liabilities
Secured bank loans		190
Trade payables	2,855	2,298
Other liabilities and accruals	6,176	3,679
Non-derivative financial liabilities undiscounted cash flows	€ 9,031	6,167
1-2 years [member]
Non-derivative financial liabilities
Secured bank loans		181
Non-derivative financial liabilities undiscounted cash flows		181
2-5 years [member]
Non-derivative financial liabilities
Secured bank loans		155
Non-derivative financial liabilities undiscounted cash flows		€ 155

Financial Instruments - Summa86

Financial Instruments - Summary of Sensitivity Analysis for Change in Primary Currency Exposure (Detail) - Currency risk [member] € in Thousands	12 Months Ended
	Dec. 31, 2017EUR (€)
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	€ 136,739
Cash and cash equivalents [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	88,538
Investment [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	47,310
Trade and other receivables [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	2,311
Trade payables, other liabilities and accruals [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	(1,420)
USD [member] | 5% increase in functional rate [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	5,701
USD [member] | 5% increase in functional rate [member] | Cash and cash equivalents [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	3,691
USD [member] | 5% increase in functional rate [member] | Investment [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	1,972
USD [member] | 5% increase in functional rate [member] | Trade and other receivables [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	97
USD [member] | 5% increase in functional rate [member] | Trade payables, other liabilities and accruals [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	(59)
USD [member] | 5% decrease in functional rate [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	(5,701)
USD [member] | 5% decrease in functional rate [member] | Cash and cash equivalents [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	(3,691)
USD [member] | 5% decrease in functional rate [member] | Investment [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	(1,972)
USD [member] | 5% decrease in functional rate [member] | Trade and other receivables [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	(97)
USD [member] | 5% decrease in functional rate [member] | Trade payables, other liabilities and accruals [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Balance	€ 59

Financial Instrument - Summar87

Financial Instrument - Summary of Interest Bearing Financial Instruments (Detail) - EUR (€) € in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of interest bearing financial instruments [line Items]
Investments	€ 41,103
Cash and cash equivalents	149,678	€ 56,917	€ 32,851	€ 1,568
Fixed-rate instruments [member]
Disclosure of interest bearing financial instruments [line Items]
Financial liabilities		(486)
Variable rate instruments [member]
Disclosure of interest bearing financial instruments [line Items]
Cash and cash equivalents	€ 149,678	€ 56,917

Board Compensation and Key Ma88

Board Compensation and Key Management Personnel - Summary on Charge to the Profit and Loss Statement (Detail) - EUR (€)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Ton Logtenberg, CEO [member]
Disclosure charged to the profit and loss statement [line Items]
Directors remuneration expense	€ 5,497,845	€ 1,441,977	€ 2,253,899
Ton Logtenberg, CEO [member] | Gross salary [member]
Disclosure charged to the profit and loss statement [line Items]
Directors remuneration expense	432,782	369,204	236,032
Ton Logtenberg, CEO [member] | Bonus [member]
Disclosure charged to the profit and loss statement [line Items]
Directors remuneration expense	337,945	147,820	89,072
Ton Logtenberg, CEO [member] | Pension [member]
Disclosure charged to the profit and loss statement [line Items]
Directors remuneration expense	51,528	17,717	18,591
Ton Logtenberg, CEO [member] | Option cost [member]
Disclosure charged to the profit and loss statement [line Items]
Directors remuneration expense	4,675,590	907,236	1,910,204
Shelley Margetson, COO [member]
Disclosure charged to the profit and loss statement [line Items]
Directors remuneration expense	892,129	453,686	495,876
Shelley Margetson, COO [member] | Gross salary [member]
Disclosure charged to the profit and loss statement [line Items]
Directors remuneration expense	420,782	198,987	159,749
Shelley Margetson, COO [member] | Bonus [member]
Disclosure charged to the profit and loss statement [line Items]
Directors remuneration expense		84,000	37,365
Shelley Margetson, COO [member] | Pension [member]
Disclosure charged to the profit and loss statement [line Items]
Directors remuneration expense	19,595	6,152	13,824
Shelley Margetson, COO [member] | Option cost [member]
Disclosure charged to the profit and loss statement [line Items]
Directors remuneration expense	€ 451,752	€ 164,547	€ 284,938

Board Compensation and Key Ma89

Board Compensation and Key Management Personnel - Summary on Charge to the Profit and Loss Statement (Parenthetical) (Detail) - EUR (€)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure charged to the profit and loss statement [line Items]
Gross salary includes severance payments	€ 9,556,000	€ 5,166,000	€ 3,204,000
Severance costs [member]
Disclosure charged to the profit and loss statement [line Items]
Gross salary includes severance payments	€ 257,260

Board Compensation and Key Ma90

Board Compensation and Key Management Personnel - Additional Information (Detail)	Feb. 15, 2017shares€ / shares	Nov. 01, 2016shares€ / shares	Oct. 27, 2016shares€ / shares	Oct. 05, 2015EUR (€)€ / shares	Dec. 31, 2017shares€ / shares	Dec. 31, 2016shares€ / shares	Dec. 31, 2015shares€ / shares
Disclosure charged to the profit and loss statement [line Items]
Number of options allocated to Chief Medical Officer					1,014,733	496,243	771,662
Number of RSUs granted					214,096
2010 Option plan [member]
Disclosure charged to the profit and loss statement [line Items]
Exercise price per share				€ 1.93
Total amount of reimbursement | €				€ 60,935
Ton Logtenberg, CEO [member]
Disclosure charged to the profit and loss statement [line Items]
Number of options allocated to Chief Medical Officer					377,271
Number of RSUs granted					123,745
Number of options held by the chief executive officers | shares					661,629	376,912	54,866
Average exercise price per share held by the chief executive officers					€ 14.20	€ 2.98	€ 5.35
Number of RSU held					123,745
Shelley Margetson, COO [member]
Disclosure charged to the profit and loss statement [line Items]
Number of options allocated to Chief Medical Officer					59,605
Number of RSUs granted					19,550
Description of vesting period					12-month period following her separation date
Andres Sirulnik Chief Medical Officer [member]
Disclosure charged to the profit and loss statement [line Items]
Number of options allocated to Chief Medical Officer | shares			219,890
Exercise price per share			€ 16.85
John Crowley Chief Financial Officer [member]
Disclosure charged to the profit and loss statement [line Items]
Number of options allocated to Chief Medical Officer | shares		183,241
Exercise price per share		€ 15.24
Peter Silverman Senior Vice President [member]
Disclosure charged to the profit and loss statement [line Items]
Number of options allocated to Chief Medical Officer | shares	50,000
Exercise price per share	€ 24.54

Board Compensation and Key Ma91

Board Compensation and Key Management Personnel - Summary of Related Party (Detail) - EUR (€)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of related party [Abstract]
Short term employment benefits	€ 2,808,998	€ 1,139,763	€ 190,763
Post-employment benefits	108,416	18,720	11,671
Other long term benefits	0	0	0
Termination benefits	0	0	0
Share based payments	5,171,233	1,195,876	57,065
Total	€ 8,088,647	€ 2,354,359	€ 259,499

Board Compensation and Key Ma92

Board Compensation and Key Management Personnel - Summary of Consolidated Statement of Profit and Loss for the Remuneration of the (Former) Members of the Supervisory Board (Detail) - EUR (€)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	€ 826,578	€ 696,942	€ 190,273
Mark Iwicki [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	180,436	233,761	141,705
Wolfgang Berthold [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	128,474	70,778	15,475
Lionel Carnot [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	97,315	91,811
John de Koning [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	152,186	63,230
Anand Mehra [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	123,298	111,641
Gregory Perry [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	144,869	125,721
Gabriele Dallmann [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees			16,795
Gerard van Odijk [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees			16,298
Cash compensation [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	252,703	176,620	37,235
Cash compensation [member] | Mark Iwicki [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	59,840	50,394	26,325
Cash compensation [member] | Wolfgang Berthold [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	37,530	19,850
Cash compensation [member] | Lionel Carnot [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	35,445	24,852
Cash compensation [member] | John de Koning [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	38,573	26,230
Cash compensation [member] | Anand Mehra [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	39,615	26,938
Cash compensation [member] | Gregory Perry [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	41,700	28,356
Cash compensation [member] | Gabriele Dallmann [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees			11,000
Option cost [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	573,875	520,322	152,948
Option cost [member] | Mark Iwicki [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	120,596	183,367	115,380
Option cost [member] | Wolfgang Berthold [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	90,944	50,928	15,475
Option cost [member] | Lionel Carnot [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	61,870	66,959
Option cost [member] | John de Koning [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	113,613	37,000
Option cost [member] | Anand Mehra [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	83,683	84,703
Option cost [member] | Gregory Perry [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees	€ 103,169	€ 97,365
Option cost [member] | Gabriele Dallmann [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees			5,795
Option cost [member] | Gerard van Odijk [member]
Disclosure of options held by the members of supervisory board [line Items]
Remuneration for former employees			€ 16,298

Board Compensation and Key Ma93

Board Compensation and Key Management Personnel - Summary of Average Exercise Price Per Share Held by the Members of the Supervisory Board (Detail)	12 Months Ended
	Dec. 31, 2017shares€ / shares	Dec. 31, 2016shares€ / shares	Dec. 31, 2015shares€ / shares
Disclosure of options held by the members of supervisory board [line Items]
Number of options | shares	193,866	185,128	113,890
Weighted average exercise price | € / shares	€ 9.61	€ 7.21	€ 4.93
Mark Iwicki [member]
Disclosure of options held by the members of supervisory board [line Items]
Number of options | shares	79,226	73,576	73,576
Weighted average exercise price | € / shares	€ 7.32	€ 6.57	€ 6.57
Wolfgang Berthold [member]
Disclosure of options held by the members of supervisory board [line Items]
Number of options | shares	24,040	26,724	14,168
Weighted average exercise price | € / shares	€ 8.90	€ 3.02	€ 1.93
Lionel Carnot [member]
Disclosure of options held by the members of supervisory board [line Items]
Number of options | shares	22,650	17,000
Weighted average exercise price | € / shares	€ 11.80	€ 8.87
John de Koning [member]
Disclosure of options held by the members of supervisory board [line Items]
Number of options | shares	22,650	17,000
Weighted average exercise price | € / shares	€ 11.80	€ 8.87
Anand Mehra [member]
Disclosure of options held by the members of supervisory board [line Items]
Number of options | shares	22,650	17,000
Weighted average exercise price | € / shares	€ 11.80	€ 8.87
Gregory Perry [member]
Disclosure of options held by the members of supervisory board [line Items]
Number of options | shares	22,650	17,000
Weighted average exercise price | € / shares	€ 11.80	€ 8.87
Gabriele Dallmann [member]
Disclosure of options held by the members of supervisory board [line Items]
Number of options | shares		16,828	4,272
Weighted average exercise price | € / shares		€ 3.24	€ 1.93
Gerard van Odijk [member]
Disclosure of options held by the members of supervisory board [line Items]
Number of options | shares			21,874
Weighted average exercise price | € / shares			€ 1.93

Related Party Disclosures - Add

Related Party Disclosures - Additional Information (Detail) - EUR (€) € in Millions	May 24, 2017	Dec. 31, 2017
Disclosure of transactions between related parties [line items]
Percentage of severance payment paid	50.00%
Percentage of severance payment being paid in form of salary continuation over six-month period	50.00%
Accrued severance payment		€ 0.1
Bottom of range [member] | Bay City Capital Cooperatief Uitgesloten Aansprakelijkheid [member]
Disclosure of transactions between related parties [line items]
Ownership interest held by shareholders		5.00%
Bottom of range [member] | Cooperatief LSP Four Uitgesloten Aansprakelijkheid [member]
Disclosure of transactions between related parties [line items]
Ownership interest held by shareholders		5.00%
Bottom of range [member] | Sofinnova Venture Partners Nine Limited Partnership [member]
Disclosure of transactions between related parties [line items]
Ownership interest held by shareholders		5.00%
Top of range [member] | Biophrase BV [member]
Disclosure of transactions between related parties [line items]
Ownership interest held by shareholders		1.00%

Operating Lease - Additional In

Operating Lease - Additional Information (Detail) - University of Utrecht [member] - EUR (€) € in Thousands	Nov. 01, 2016	Dec. 31, 2017	Dec. 31, 2016
Disclosure of operating lease [Line Items]
Rental expense		€ 434
Rent and service charges expense		€ 564	€ 270
Operating lease term of lease agreement	5 years	2 years
Leases expiration period		Fourth quarter of 2021

Operating Leases - Schedule of

Operating Leases - Schedule of Future Minimum Lease Payments Under Lease (Detail) € in Thousands	Dec. 31, 2017EUR (€)
Disclosure of finance lease and operating lease by lessee [line items]
Minimum lease payments payable under non cancellable operating lease	€ 2,499
Less than one year [member]
Disclosure of finance lease and operating lease by lessee [line items]
Minimum lease payments payable under non cancellable operating lease	602
Between one and five years [member]
Disclosure of finance lease and operating lease by lessee [line items]
Minimum lease payments payable under non cancellable operating lease	€ 1,897

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) € / shares in Units, $ / shares in Units, $ in Millions	Mar. 14, 2018EUR (€)	Feb. 13, 2018USD ($)$ / shares	Jan. 08, 2018Program	Feb. 28, 2018USD ($)	Jan. 31, 2017USD ($)	Dec. 31, 2017EUR (€)	Dec. 31, 2016EUR (€)	Dec. 31, 2015EUR (€)€ / shares	Feb. 13, 2018€ / sharesshares
Disclosure of Events After Reporting Period [Line Items]
Issue price per share | € / shares								€ 0.09
Aggregate purchase price					$ 80	€ 74,738,000	€ 50,547,000	€ 46,478,000
Collaboration and license agreement [member] | Top of range [member]
Disclosure of Events After Reporting Period [Line Items]
Number of bispecific Antibody Research Programs | Program			3
Potential ordinary share transactions [member]
Disclosure of Events After Reporting Period [Line Items]
Common shares issued | shares									3,099,997
Issue price per share | € / shares									€ 0.09
Aggregate purchase price | $		$ 55.8		$ 55.8
Purchase price | $ / shares		$ 18
ONO Research and License Agreement [member]
Disclosure of Events After Reporting Period [Line Items]
Upfront non-refundable payment received | €	€ 700,000
Milestone payments received | €	€ 33,700,000