uniQure (QURE) 10-Q 27 Oct 20 2020 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Oct. 22, 2020
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-36294
Entity Registrant Name	uniQure N.V.
Entity Incorporation, State or Country Code	P7
Entity Address, Address Line One	Paasheuvelweg 25
Entity Address, City or Town	1105 BP Amsterdam
Entity Address, Country	NL
City Area Code	31
Local Phone Number	20-240-6000
Title of 12(b) Security	Ordinary Shares, par value €0.05
Trading Symbol	QURE
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		44,496,141
Entity Central Index Key	0001590560
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 279,493	$ 377,793
Accounts receivable and accrued income from related party	223	947
Prepaid expenses	4,168	4,718
Other current assets and receivables	3,496	748
Total current assets	287,380	384,206
Non-current assets
Property, plant and equipment, net of accumulated depreciation of $33.2 million as of September 30, 2020 and $28.6 million as of December 31, 2019, respectively	29,636	28,771
Operating lease right-of-use assets	26,207	26,797
Intangible assets, net	4,052	5,427
Goodwill	518	496
Restricted cash	2,714	2,933
Total non-current assets	63,127	64,424
Total assets	350,507	448,630
Current liabilities
Accounts payable	2,348	5,681
Accrued expenses and other current liabilities	17,784	12,457
Current portion of operating lease liabilities	5,552	5,865
Current portion of deferred revenue	7,666	7,627
Total current liabilities	33,350	31,630
Non-current liabilities
Long-term debt	35,494	36,062
Operating lease liabilities, net of current portion	30,333	31,133
Deferred revenue, net of current portion	22,413	23,138
Derivative financial instruments related party	547	3,075
Other non-current liabilities	477	534
Total non-current liabilities	89,264	93,942
Total liabilities	122,614	125,572
Commitments and contingencies
Shareholders' equity
Ordinary shares, 0.05 par value: 60,000,000 shares authorized at September 30, 2020 and December 31, 2019 and 44,487,510 and 43,711,954 ordinary shares issued and outstanding at September 30, 2020 and December 31, 2019, respectively	2,694	2,651
Additional paid-in-capital	1,006,898	986,803
Accumulated other comprehensive loss	2,333	(6,689)
Accumulated deficit	(784,032)	(659,707)
Total shareholders' equity	227,893	323,058
Total liabilities and shareholders' equity	$ 350,507	$ 448,630

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) $ in Millions	Sep. 30, 2020USD ($)shares	Sep. 30, 2020€ / shares	Dec. 31, 2019USD ($)shares	Dec. 31, 2019€ / shares
CONSOLIDATED BALANCE SHEETS
Accumulated depreciation | $	$ 33.2		$ 28.6
Ordinary shares, par value (in euros per share) | € / shares		€ 0.05		€ 0.05
Ordinary shares, authorized	60,000,000		60,000,000
Ordinary shares, issued	44,487,510		43,711,954
Ordinary shares, outstanding	44,487,510		43,711,954

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Total revenues	$ 1,789	$ 1,046	$ 3,428	$ 4,656
Operating expenses:
Research and development expenses	(36,302)	(23,554)	(90,716)	(68,245)
Selling, general and administrative expenses	(10,789)	(8,929)	(31,372)	(24,866)
Total operating expenses	(47,091)	(32,483)	(122,088)	(93,111)
Other income	1,032	453	2,558	1,332
Other expense	(220)	(342)	(1,059)	(1,038)
Loss from operations	(44,490)	(31,326)	(117,161)	(88,161)
Interest income	13	868	916	2,038
Interest expense	(942)	(960)	(2,887)	(2,854)
Foreign currency (losses) / gains, net	(8,681)	6,041	(7,724)	7,063
Other non-operating gains / (losses), net	325	1,773	2,531	(861)
Net loss	(53,775)	(23,604)	(124,325)	(82,775)
Other comprehensive income / (loss):
Foreign currency translation adjustments	9,652	(6,164)	9,022	(7,423)
Total comprehensive loss	$ (44,123)	$ (29,768)	$ (115,303)	$ (90,198)
Basic and diluted net loss per ordinary share	$ (1.21)	$ (0.58)	$ (2.80)	$ (2.14)
Weighted average shares used in computing basic and diluted net loss per ordinary share	44,471,844	40,738,938	44,379,924	38,757,898
License revenues from related party
Total revenues	$ 1,776	$ 842	$ 3,353	$ 3,507
Collaboration revenues from related party
Total revenues	$ 13	$ 204	$ 75	$ 1,149

CONSOLIDATED STATEMENTS OF SHAR

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Ordinary shares	Additional paid-in capital	Accumulated other comprehensive (loss)/income	Accumulated deficit	Total
Beginning balance at Dec. 31, 2018	$ 2,299	$ 720,072	$ (7,259)	$ (535,506)	$ 179,606
Beginning balance (in shares) at Dec. 31, 2018	37,351,653
Increase (decrease) in shareholders' equity
Loss for the period				(82,775)	(82,775)
Other comprehensive income (loss)			(7,423)		(7,423)
Follow-on public offering	$ 311	242,480			242,791
Follow-on public offering (in shares)	5,625,000
Hercules warrants exercise	$ 2	1,271			1,273
Hercules warrants exercise (in shares)	37,175
Exercise of share options	$ 20	3,714			3,734
Exercise of share options (in shares)	355,879
Restricted and performance share units distributed during the period	$ 14	(14)
Restricted and performance share units distributed during the period (in shares)	235,692
Share-based compensation expense		12,762			12,762
Issuance of ordinary shares relating to employee stock purchase plan		264			264
Issuance of ordinary shares relating to employee stock purchase plan (in shares)	7,018
Ending balance at Sep. 30, 2019	$ 2,646	980,549	(14,682)	(618,281)	350,232
Ending balance (in shares) at Sep. 30, 2019	43,612,417
Beginning balance at Jun. 30, 2019	$ 2,327	732,924	(8,518)	(594,677)	132,056
Beginning balance (in shares) at Jun. 30, 2019	37,839,833
Increase (decrease) in shareholders' equity
Loss for the period				(23,604)	(23,604)
Other comprehensive income (loss)			(6,164)		(6,164)
Follow-on public offering	$ 311	242,480			242,791
Follow-on public offering (in shares)	5,625,000
Exercise of share options	$ 6	1,172			1,178
Exercise of share options (in shares)	119,225
Restricted and performance share units distributed during the period	$ 2	(2)
Restricted and performance share units distributed during the period (in shares)	26,211
Share-based compensation expense		3,876			3,876
Issuance of ordinary shares relating to employee stock purchase plan		99			99
Issuance of ordinary shares relating to employee stock purchase plan (in shares)	2,148
Ending balance at Sep. 30, 2019	$ 2,646	980,549	(14,682)	(618,281)	350,232
Ending balance (in shares) at Sep. 30, 2019	43,612,417
Increase (decrease) in shareholders' equity
Accumulated deficit					(659,707)
Beginning balance at Dec. 31, 2019	$ 2,651	986,803	(6,689)	(659,707)	$ 323,058
Beginning balance (in shares) at Dec. 31, 2019	43,711,954				43,711,954
Increase (decrease) in shareholders' equity
Loss for the period				(124,325)	$ (124,325)
Other comprehensive income (loss)			9,022		9,022
Exercise of share options	$ 12	3,529			3,541
Exercise of share options (in shares)	211,288
Restricted and performance share units distributed during the period	$ 31	(31)
Restricted and performance share units distributed during the period (in shares)	560,986
Share-based compensation expense		16,450			16,450
Issuance of ordinary shares relating to employee stock purchase plan		147			147
Issuance of ordinary shares relating to employee stock purchase plan (in shares)	3,282
Ending balance at Sep. 30, 2020	$ 2,694	1,006,898	2,333	(784,032)	$ 227,893
Ending balance (in shares) at Sep. 30, 2020	44,487,510				44,487,510
Beginning balance at Jun. 30, 2020	$ 2,692	1,000,389	(7,319)	(730,257)	$ 265,505
Beginning balance (in shares) at Jun. 30, 2020	44,444,405
Increase (decrease) in shareholders' equity
Loss for the period				(53,775)	(53,775)
Other comprehensive income (loss)			9,652		9,652
Exercise of share options		139			139
Exercise of share options (in shares)	7,348
Restricted and performance share units distributed during the period	$ 2	(2)
Restricted and performance share units distributed during the period (in shares)	35,480
Share-based compensation expense		6,372			6,372
Issuance of ordinary shares relating to employee stock purchase plan (in shares)	277
Ending balance at Sep. 30, 2020	$ 2,694	$ 1,006,898	$ 2,333	$ (784,032)	$ 227,893
Ending balance (in shares) at Sep. 30, 2020	44,487,510				44,487,510
Increase (decrease) in shareholders' equity
Accumulated deficit					$ (784,032)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities
Net loss	$ (124,325)	$ (82,775)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	8,354	4,932
Share-based compensation expense	16,450	12,762
Change in fair value of derivative financial instruments	(2,531)	862
Unrealized foreign exchange losses / (gains)	7,758	(6,692)
Changes in operating assets and liabilities:
Accounts receivable and accrued income, prepaid expenses and other current assets and receivables	(1,183)	(2,879)
Accounts payable	(3,724)	(418)
Accrued expenses, other liabilities and operating leases	3,630	4,934
Deferred revenue	(2,082)	(3,403)
Net cash used in operating activities	(97,653)	(72,677)
Cash flows from investing activities
Purchases of intangible assets	(2,314)	(996)
Purchases of property, plant and equipment	(4,475)	(3,688)
Net cash used in investing activities	(6,789)	(4,684)
Cash flows from financing activities
Proceeds from issuance of shares related to employee stock option and purchase plans	3,688	3,998
Proceeds from public offering of shares, net of issuance costs		243,013
Proceeds from exercise of warrants		500
Net cash generated from financing activities	3,688	247,511
Currency effect on cash, cash equivalents and restricted cash	2,235	(1,415)
Net (decrease) / increase in cash, cash equivalents and restricted cash	(98,519)	168,735
Cash, cash equivalents and restricted cash at beginning of period	380,726	237,342
Cash, cash equivalents and restricted cash at the end of period	282,207	406,077
Total cash, cash equivalents and restricted cash	282,207	406,077
Supplemental cash flow disclosures:
Cash paid for interest	(3,342)	(2,330)
Non-cash increases in accounts payables and accrued expenses and other current liabilities related to purchases of intangible assets and property, plant and equipment	$ 116	$ 583

General business information

General business information	9 Months Ended
	Sep. 30, 2020
General business information
General business information	1 ​ uniQure (the “Company”) was incorporated on January 9, 2012 as a private company with limited liability ( besloten vennootschap met beperkte aansprakelijkheid naamloze vennootschap ​ The Company is registered in the trade register of the Chamber of Commerce ( Kamer van Koophandel ​ The Company’s ordinary shares are listed on the Nasdaq Global Select Market and trade under the symbol “QURE”.

Summary of significant accounti

Summary of significant accounting policies	9 Months Ended
	Sep. 30, 2020
Summary of significant accounting policies
Summary of significant accounting policies	​ 2 ​ 2.1 Basis of preparation ​ The Company prepared these unaudited consolidated financial statements in compliance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the SEC regarding interim financial reporting. Any reference in these notes to applicable guidance is meant to refer to authoritative U.S. GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). ​ The unaudited consolidated financial statements are presented in U.S. dollars, except where otherwise indicated. Transactions denominated in currencies other than U.S. dollars are presented in the transaction currency with the U.S. dollar amount included in parenthesis, converted at the foreign exchange rate as of the transaction date. ​ 2.2 Unaudited interim financial information ​ The interim financial statements and related disclosures are unaudited, have been prepared on the same basis as the annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair statement of the financial position, results of operations and changes in financial position for the period presented. ​ Certain information and footnote disclosures normally included in annual financial statements prepared in accordance with U.S. GAAP have been omitted. The results of operations for the nine months ended September 30, 2020, are not necessarily indicative of the results to be expected for the full year ending December 31, 2020 or for any other future year or interim period. The accompanying financial statements should be read in conjunction with the audited financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on March 2, 2020 ​ 2.3 Use of estimates ​ The preparation of the financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. ​ 2.4 Accounting policies ​ The principal accounting policies applied in the preparation of these unaudited consolidated financial statements are described in the Company’s audited financial statements as of and for the year ended December 31, 2019, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on March 2, 2020 ​ 2.5 Recent accounting pronouncements ​ There have been no new accounting pronouncements or changes to accounting pronouncements during the nine months ended September 30, 2020, as compared to the recent accounting pronouncements described in Note 2.3.23 of the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 ​

Collaboration arrangements and

Collaboration arrangements and concentration of credit risk	9 Months Ended
	Sep. 30, 2020
Collaboration arrangements and concentration of credit risk
Collaboration arrangements and concentration of credit risk	3 Collaboration arrangements and concentration of credit risk ​ CSL Behring collaboration ​ On June 24, 2020, uniQure biopharma B.V., a wholly-owned subsidiary of uniQure N.V., entered into a commercialization and license agreement (the “CSL Behring Agreement”) with CSL Behring LLC (“CSL Behring”) pursuant to which CSL Behring will receive exclusive global rights to etranacogene dezaparvovec, the Company’s investigational gene therapy for patients with hemophilia B (the “Product”). ​ Under the terms of the CSL Behring Agreement, the Company will receive a $450 million upfront cash payment upon the closing of the CSL Behring Agreement and be eligible to receive up to $1.6 billion in additional payments based on regulatory and commercial milestones. The CSL Behring Agreement also provides that the Company will be eligible to receive tiered double-digit royalties in a range of up to a low-twenties percent of net sales of the Product based on sales thresholds. Pursuant to the CSL Behring Agreement, the Company will be responsible for the completion of the HOPE-B clinical trial, manufacturing process validation, and the manufacturing supply of the Product until such time that these capabilities may be transferred to CSL Behring or its designated contract manufacturing organization. Concurrently with the execution of the CSL Behring Agreement, the Company and CSL Behring entered into a development and commercial supply agreement, pursuant to which, among other things, the Company will supply the Product to CSL Behring at an agreed-upon price. Clinical development and regulatory activities performed by the Company pursuant to the CSL Behring Agreement will be reimbursed by CSL Behring. CSL Behring will be responsible for global regulatory submissions and commercialization requirements for the Product. Closing of the CSL Behring Agreement is contingent on the successful completion of reviews under antitrust laws in the United States, Australia, and the United Kingdom, which has not occurred to date. Closing of the transaction is dependent on the timing, extent, and result of the regulatory review process. The Company does not believe that the consummation of the transaction will result in a violation of any applicable antitrust laws. However, there can be no assurance that a challenge on antitrust grounds will not be made, or if such a challenge is made, what the result would be. As of September 30, 2020, the Company concluded it has no enforceable right to receive any of the upfront payment, the regulatory and sales milestone payments or the royalties (together “CSL License Revenue”) that it may receive in accordance with the CSL Behring Agreement, as all payments are contingent upon the successful completion of reviews under antitrust laws in the United States, Australia and the United Kingdom. Therefore, the Company determined it will not recognize any revenue in relation to the CSL License Revenue, in accordance with ASC 606. The Company determined that in accordance with Dutch tax law it will recognize the CSL Behring License Revenue as well as the License Fees as taxable results as of the date on which the Company is contractually entitled to receive (or obligated to make) a payment under the CSL Behring Agreement. The Company expects to continue to incur taxable losses in the Netherlands except for the period in which it receives the $450 million upfront payment under the CSL Behring Agreement. In the event that the Company recognizes the $450 million upfront payment in 2020, such payment is expected to be subject to Dutch corporate income tax at a rate of 25.0%. However, the Company does not expect it will be required to pay any income taxes in the period in which it recognizes the $450 million upfront payment as taxable revenue, as such payment is not expected to exceed the net operating losses the Company has carried forward in the Netherlands. The Company has historically recorded a full valuation allowance against its net deferred tax assets. Future taxable income or losses of the Company and a potential reversal of the valuation allowance will be impacted by a variety of factors, of which some are outside of the Company’s control. Such factors include the outcome and timing of the reviews under antitrust laws in the United States, Australia, and the United Kingdom, additional net operating losses the Company may generate in relation to the CSL Behring Agreement, and the amount of License Fees the Company is required to pay. ​ The Company recognizes deferred tax assets to the extent that it determines that these assets are more likely than not to be realized. In making such a determination, the Company weighed all available positive and negative evidence, including future income projections from the CSL Behring Agreement, and concluded that it is more likely than not that the deferred tax assets will not be realized. Accordingly, the Company continued to record a full valuation allowance as of September 30, 2020. ​ Bristol-Myers Squibb collaboration ​ In May 2015, the Company entered into a collaboration and license agreement (the “BMS CLA”) and various related agreements with Bristol-Myers Squibb Company (“BMS”) that provide BMS with exclusive access to the Company’s gene therapy technology platform for the research, development and commercialization of therapeutics aimed at multiple targets in cardiovascular and other diseases (“Collaboration Targets”). The initial four-year research term under the collaboration terminated on May 21, 2019. During the initial research term of the BMS CLA, the Company supported BMS in discovery, non-clinical, analytical and process development efforts in respect of the Collaboration Targets. For any Collaboration Targets that may be advanced, the Company will be responsible for manufacturing of clinical and commercial supplies using the Company’s vector technologies and industrial, proprietary insect-cell based manufacturing platform. BMS reimbursed the Company for all its research and development costs in support of the collaboration during the initial research term, and will lead development, regulatory and commercial activities for any Collaboration Targets that may be advanced. The BMS CLA provides that the Company and BMS may collaborate on up to ten Collaboration Targets in total. As of September 30, 2020, BMS has designated a total of four Collaboration Targets. In February 2019, BMS requested a one-year extension of the research term. In April 2019, following an assessment of the progress of this collaboration and the Company’s expanding proprietary programs, the Company notified BMS that the Company did not intend to agree to an extension of the research term but rather preferred to restructure or amend the collaboration to reduce or eliminate certain of the Company’s obligations under it. ​ The Company has agreed to certain restrictions on its ability to work independently of the collaboration, either directly or indirectly through any affiliate or third party, on certain programs that would be competitive with the collaboration programs. The Company is currently in discussions with BMS potentially to amend the BMS CLA and other related agreements following the expiration of the research term. It is currently uncertain whether a change to the BMS CLA will be agreed and, if agreed, what the specific terms of any such change may be. As a consequence, the Company has not taken into account the impact of such change, if any, on the timing of recognition of the prepaid License Revenue if and when the BMS CLA and other related agreements have been restructured or amended. The final resolution of these discussions may or may not result in material changes to the Company’s collaboration with BMS. The Company agreed, subject to certain conditions, to continue providing limited support of the pre-clinical Collaboration Targets, and any related costs will be reimbursed by BMS during these discussions. The Company evaluated the BMS CLA and determined that its performance obligations are as follows: (i) Providing access to its technology and know-how in the field of gene therapy as well as actively contributing to the target selection, the collaboration as a whole, the development during the target selection, the pre-clinical and the clinical phase through participating in joint steering committee and other governing bodies (“License Revenue”); (ii) Providing pre-clinical Collaboration Target specific, non-clinical, analytical and process development services during the initial research term, which ended on May 21, 2019 (“Collaboration Revenue”); and (iii) Providing clinical and commercial manufacturing services for Collaboration Targets (“Manufacturing Revenue”). To date the Company has not generated any Manufacturing Revenue. ​ Amounts owed by BMS in relation the collaboration services are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2020 2019 ​ ​ (in thousands) Bristol Myers Squibb ​ $ 223 ​ $ 947 Total ​ $ 223 ​ $ 947 ​ License Revenue The Company recognized $1.8 million and $3.4 million of License Revenue for the three and nine months ended September 30, 2020, respectively, compared to $0.8 million and $3.5 million during the same periods in 2019 in relation to a $60.1 million upfront payment recorded on May 21, 2015, as well as $15.0 million received in relation to the designation of the second, third and fourth Collaboration Targets in August 2015 (together “Consideration”). The Company would be entitled to an aggregate $16.5 million in target designation payments upon the selection of the fifth through tenth Collaboration Targets. The Company would also be eligible to receive research, development and regulatory milestone payments of up to $217.0 million for each Collaboration Target, if defined milestones are achieved. The Company would include the variable consideration related to the selection of the fifth to tenth Collaboration Target, or any of the milestones, in the transaction price once it is considered probable that including these payments in the transaction price would not result in the reversal of cumulative revenue recognized. The Company would recognize significant amounts of License Revenue for services performed in prior periods if and when the Company considers this probable. Due to the significant uncertainty surrounding the development of gene-therapy product candidates and the dependence on BMS’s performance and decisions, the Company does not currently consider this probable. Additionally, the Company is eligible to receive net sales-based milestone payments and tiered mid-single to low double-digit royalties on product sales. The royalty term is determined on a licensed-product-by-licensed-product and country-by-country basis and begins on the first commercial sale of a licensed product in a country and ends on the expiration of the last to expire of specified patents or regulatory exclusivity covering such licensed product in such country or, with a customary royalty reduction, ten years after the first commercial sale if there is no such exclusivity. These revenues will be recognized when performance obligations are satisfied. The Company recognizes License Revenue over the expected performance period based on its measure of progress towards the completion of certain activities related to its services. The Company determines such progress by comparing activities performed at the end of each reporting period with total activities expected to be performed. The Company estimates total expected activities using a number of unobservable inputs, such as the probability of BMS designating additional targets, the probability of successfully completing each phase and estimated time required to provide services during the various development stages. If available, the Company uses product candidate-specific research and development plans. Alternatively, the Company assumes that completion of the pre-clinical phase requires an average of four years and that clinical development and commercial launch on average require 8.5 years.

Fair value measurement

Fair value measurement	9 Months Ended
	Sep. 30, 2020
Fair value measurement
Fair value measurement	4 ​ The Company measures certain assets and liabilities at fair value, either upon initial recognition or for subsequent accounting or reporting. U.S. GAAP requires disclosure of methodologies used in determining the reported fair values, and establishes a hierarchy of inputs used when available. The three levels of the fair value hierarchy are described below: ● Level 1 - Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company can access at the measurement date. ● Level 2 - Valuations based on quoted prices for similar assets or liabilities in markets that are not active or models for which the inputs are observable, either directly or indirectly. ● Level 3 - Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and are unobservable. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized as Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. ​ The carrying amount of cash and cash equivalents, accrued income from the related party, prepaid expenses, other assets, accounts payable, accrued expenses and other current liabilities reflected in the Consolidated balance sheets approximate their fair values due to their short-term maturities. The following table sets forth the Company’s assets and liabilities that are required to be measured at fair value on a recurring basis as of September 30, 2020, and December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quoted prices Significant Significant Total Classification in Consolidated ​ ​ ​ (in thousands) ​ ​ At December 31, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash, cash equivalents and restricted cash ​ $ 380,726 ​ $ — ​ $ — ​ $ 380,726 ​ Cash and cash equivalents; restricted cash Total assets ​ $ 380,726 ​ $ — ​ $ — ​ $ 380,726 ​ ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivative financial instruments - related party ​ ​ — ​ ​ — ​ ​ 3,075 ​ ​ 3,075 ​ ​ Total liabilities ​ $ — ​ $ — ​ $ 3,075 ​ $ 3,075 ​ ​ At September 30, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash, cash equivalents and restricted cash ​ $ 282,207 ​ $ — ​ $ — ​ $ 282,207 ​ Cash and cash equivalents; restricted cash Total assets ​ $ 282,207 ​ $ — ​ $ — ​ $ 282,207 ​ ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivative financial instruments - related party ​ $ — ​ $ — ​ $ 547 ​ $ 547 ​ ​ Total liabilities ​ $ — ​ $ — ​ $ 547 ​ $ 547 ​ ​ ​ Changes in Level 3 items during the nine months ended September 30, 2020, are as follows: ​ ​ ​ ​ ​ ​ ​ Derivative ​ ​ financial ​ instruments ​ ​ (in thousands) Balance at December 31, 2019 ​ $ 3,075 Net gains recognized in profit or loss ​ ​ (2,531) Currency translation effects ​ ​ 3 Balance at September 30, 2020 ​ $ 547 ​ ​ ​ ​ ​ BMS warrants ​ The Company issued derivative financial instruments related to its collaboration with BMS. The fair value of the BMS derivative financial instruments (“BMS warrants”) as of September 30, 2020, was $0.5 million compared to a fair value of $3.1 million as of December 31, 2019. Changes in the fair value of the BMS warrants are primarily impacted by changes in the Company’s share price, whereby a decrease in share price generally results in a decrease of the fair value. In addition, the Company revised certain unobservable inputs as well as valuation techniques in March 2020 which resulted in a further decrease in fair value of $0.7 million when compared to December 31, 2019. These BMS warrants are described in more detail below. ​ The Company granted BMS two warrants: ​ ● A warrant allowing BMS to purchase a specific number of the Company’s unregistered ordinary shares such that its ownership will equal 14.9% immediately after such purchase (“1 st warrant”). The 1 st warrant can be exercised on the later of (i) the date on which the Company receives from BMS the Target Designation Fees (as defined in the BMS CLA) associated with the first six new targets (a total of seven Collaboration Targets); and (ii) the date on which BMS designates the sixth new target (the seventh Collaboration Target). ● A warrant allowing BMS to purchase a specific number of the Company’s unregistered ordinary shares such that its ownership will equal 19.9% immediately after such purchase (“2 nd warrant” and together with the 1 st warrant, the “warrants”). The 2 nd warrant can be exercised on the later of (i) the date on which the Company receives from BMS the Target Designation Fees associated with the first nine new targets (a total of ten Collaboration Targets); and (ii) the date on which BMS designates the ninth new target (the tenth Collaboration Target). Pursuant to the terms of the BMS CLA, the exercise price in respect of each warrant is equal to the greater of (i) the product of (A) $33.84 and (B) a compounded annual growth rate of 10% (or approximately $56.41 as of September 30, 2020) and (ii) the product of (A) 1.10 and (B) the VWAP for the 20 trading days ending on the date that is five ​ As of September 30, 2020, BMS had designated a total of four Collaboration Targets, and as such, the warrants were not exercisable. The Company estimated the exercise of warrants to occur within three ​ The significant unobservable inputs that the Company uses to develop Level 3 fair value measurements include the number of ordinary shares outstanding at the time of BMS’s warrant exercises. The number of such ordinary shares outstanding at the time of exercise determines the number of unregistered ordinary shares to be issued in connection with the BMS warrants. ​ The warrants can only be exercised following the occurrence of events contractually defined in the warrant agreements. The probability of the occurrence of these events represent another significant unobservable input used in the calculation of the fair value of the warrants. The Company estimates that the probability of the occurrence of events allowing BMS to exercise the 1 st nd st nd ​

Right-of-use asset and lease li

Right-of-use asset and lease liabilities	9 Months Ended
	Sep. 30, 2020
Right-of-use asset and lease liabilities
Right-of-use asset and lease liabilities	5 Right-of-use assets and lease liabilities ​ The Company’s most significant leases relate to office and laboratory space under the following operating lease agreements: ​ Lexington, Massachusetts / United States ​ In July 2013, the Company entered into a lease for a facility in Lexington, Massachusetts, United States. In November 2018, the term was expanded by five years from 2024 to June 2029. The lease is renewable for two subsequent five-year terms. Additionally, the lease was expanded to include an additional 30,655 square feet within the same facility and for the same term. The lease of the expansion space commenced on June 1, 2019. ​ Amsterdam / The Netherlands ​ In March 2016, the Company entered into a 16-year lease for a facility in Amsterdam, the Netherlands, and amended this agreement in June 2016. The lease for this facility terminates in February 2032, with an option ​ On December 1, 2017, the Company entered into an agreement to sub-lease three of the seven floors of its Amsterdam facility for a ten-year term ending on December 31, 2027, with an option ​ The table below presents the components of the Company’s lease costs for the periods indicated: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, Nine months ended September 30, ​ 2020 2019 2020 2019 ​ ​ (in thousands) ​ (in thousands) Operating lease cost ​ $ 1,317 ​ $ 1,264 ​ $ 3,896 ​ $ 3,183 Variable lease cost ​ ​ 155 ​ ​ 131 ​ ​ 453 ​ ​ 313 Sublease income ​ ​ (222) ​ ​ (260) ​ ​ (679) ​ ​ (792) Total lease cost ​ $ 1,250 ​ $ 1,135 ​ $ 3,670 ​ $ 2,704 ​ ​ The table below presents the lease-related assets and liabilities recorded on the Consolidated balance sheets for the periods indicated. ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ ​ 2020 ​ 2019 ​ ​ (in thousands) Assets ​ ​ ​ ​ ​ ​ Operating lease right-of-use assets ​ $ 26,207 ​ ​ 26,797 Liabilities ​ ​ ​ ​ ​ ​ Current ​ ​ ​ ​ ​ ​ Current operating lease liabilities ​ ​ 5,552 ​ ​ 5,865 Non-current ​ ​ ​ ​ ​ ​ Non-current operating lease liabilities ​ ​ 30,333 ​ ​ 31,133 Total lease liabilities ​ $ 35,885 ​ ​ 36,998 ​ Other information ​ The weighted-average remaining lease term as of September 30, 2020 is 9.6 years, compared to 10.3 years as of December 31, 2019 and the weighted-average discount rate as of September 30, 2020 is 11.35%, compared to 11.33% as of December 31, 2019. The Company derived the weighted-average discount rate, adjusted for differences such as in the term and payment patterns, from the Company’s loan from Hercules Capital which was refinanced immediately prior to the January 1, 2019 adoption date in December 2018. ​ Cash paid for amounts included in the measurement of lease liabilities for the periods indicated below was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, Nine months ended September 30, ​ 2020 2019 2020 2019 ​ (in thousands) ​ (in thousands) Operating cash flows for operating leases 1) $ 1,401 ​ $ 1,761 ​ $ 4,556 ​ $ 3,777 ​ ( 1) ​ The Company did not obtain any right-of-use assets in exchange for lease obligations in the three and nine months ended September 30, 2020. Besides the initial recognition of operating right-of-use assets of $19.0 million upon adoption of the new lease standards on January 1, 2019, the Company obtained $0.4 million and $9.0 million of additional right-of-use assets in exchange for lease obligations in the three and nine months ended September 30, 2019, respectively. ​ Undiscounted cash flows ​ The table below reconciles the undiscounted cash flows as of September 30, 2020, for each of the first five years and the total of the remaining years to the operating lease liabilities recorded on the Consolidated balance sheet as of September 30, 2020. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Lexington ​ Amsterdam 1) ​ Other 1) ​ Total ​ (in thousands) 2020 (three months remaining) $ 848 ​ $ 494 ​ $ — ​ $ 1,342 2021 ​ 3,455 ​ ​ 1,978 ​ ​ 148 ​ ​ 5,581 2022 ​ 3,552 ​ ​ 1,978 ​ ​ — ​ ​ 5,530 2023 ​ 3,650 ​ ​ 1,978 ​ ​ — ​ ​ 5,628 2024 ​ 4,146 ​ ​ 1,978 ​ ​ — ​ ​ 6,124 Thereafter ​ 20,745 ​ ​ 13,678 ​ ​ — ​ ​ 34,423 Total lease payments $ 36,396 ​ $ 22,084 ​ $ 148 ​ $ 58,628 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less: amount of lease payments representing interest payments ​ (13,180) ​ ​ (9,558) ​ ​ (5) ​ ​ (22,743) Present value of lease payments ​ 23,216 ​ ​ 12,526 ​ ​ 143 ​ ​ 35,885 Less: current operating lease liabilities ​ (3,431) ​ ​ (1,978) ​ ​ (143) ​ ​ (5,552) Non-current operating lease liabilities $ 19,785 ​ $ 10,548 ​ $ — ​ $ 30,333 ​ ( 1)

Accrued expenses and other curr

Accrued expenses and other current liabilities	9 Months Ended
	Sep. 30, 2020
Accrued expenses and other current liabilities
Accrued expenses and other current liabilities	6 Accrued expenses and other current liabilities ​ Accrued expenses and other current liabilities include the following items: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2020 2019 ​ ​ (in thousands) Accruals for services provided by vendors-not yet billed ​ $ 9,206 ​ $ 5,425 Personnel related accruals and liabilities ​ ​ 8,578 ​ ​ 7,032 Total ​ $ 17,784 ​ $ 12,457 ​

Long-term debt

Long-term debt	9 Months Ended
	Sep. 30, 2020
Long-term debt
Long-term debt	7 Long-term debt ​ On June 14, 2013, the Company entered into a venture debt loan facility with Hercules Growth Capital, Inc. (“Hercules”), which was amended and restated on June 26, 2014, and again on May 6, 2016 (“2016 Amended Facility”). On December 6, 2018, the Company signed an amendment to the Second Amended and Restated Loan and Security Agreement that both refinanced the then-existing $20 million 2016 Amended Facility and provided an additional unconditional commitment of $15 million as well as a conditional commitment of $15 million that expired on June 30, 2020 (the “2018 Amended Facility”). At signing of the 2018 Amended Facility, the Company drew down an additional $15 million for a total of $35 million outstanding. The 2018 Amended Facility extended the loan’s maturity date from May 1, 2020 until June 1, 2023. The interest-only period was initially extended from November 2018 to January 1, 2021 and was further extended to January 1, 2022 as a result of meeting the provision in the 2018 Amended Facility of raising more than $90.0 million in equity financing in September 2019. The Company is required to repay the facility in equal monthly installments of principal and interest between the end of the interest-only period and the maturity date. The interest rate continues to be adjustable and is the greater of (i) 8.85% and (ii) 8.85% plus the prime rate less 5.50% per annum. Under the 2018 Amended Facility, the Company paid a facility fee of 0.50% of the $35 million outstanding as of signing and owes a back-end fee of 4.95% of the outstanding debt. In addition, in May 2020 the Company paid a back-end fee of $1.0 million in relation to the 2016 Amended Facility. The amortized cost (including interest due presented as part of accrued expenses and other current liabilities) of the 2018 Amended Facility was $35.8 million as of September 30, 2020, compared to $36.3 million as of December 31, 2019, and is recorded net of discount and debt issuance costs. The foreign currency gain on the loan in the three and nine months ended September 30, 2020, was $1.5 million and $1.5 million compared to a foreign currency loss of $1.5 million and $1.7 million during the same periods in 2019. Interest expense associated with the 2018 Amended Facility during the three and nine months ended September 30, 2020 was $0.9 million and $2.7 million, respectively, compared to $0.9 million and $2.8 million during the same periods in 2019. As a covenant in the 2018 Amended Facility, the Company has periodic reporting requirements and is required to keep a minimum cash balance deposited in bank accounts in the United States, equivalent to the lesser of (i) 65% of the outstanding balance of principal due or (ii) 100% of worldwide cash and cash equivalents. This restriction on cash and cash equivalents only relates to the location of the cash and cash equivalents, and such cash and cash equivalents can be used at the discretion of the Company. In combination with other covenants, the 2018 Amended Facility restricts the Company’s ability to, among other things, incur future indebtedness and obtain additional debt financing, to make investments in securities or in other companies, to transfer assets, to perform certain corporate changes, to make loans to employees, officers and directors, and to make dividend payments and other distributions. The Company secured the facilities by directly or indirectly pledging its total assets of $350.6 million with the exception of $98.0 million of cash and cash equivalents and other current assets held by uniQure N.V. The 2018 Amended Facility contains provisions that include the occurrence of a material adverse effect, as defined therein, which would entitle Hercules to declare all principal, interest and other amounts owed by the Company immediately due and payable. As of September 30, 2020, the Company was in compliance with all covenants and provisions. ​

Share-based compensation

Share-based compensation	9 Months Ended
	Sep. 30, 2020
Share-based compensation
Share-based compensation	8 ​ The Company’s share-based compensation plans include the 2014 Amended and Restated Share Option Plan (the “2014 Plan”) and inducement grants under Rule 5653(c)(4) of the Nasdaq Global Select Market with terms similar to the 2014 Plan (together the “2014 Plans”). At the annual general meeting of shareholders in June 2018, the Company’s shareholders approved amendments of the 2014 Plan, increasing the shares authorized for issuance by 3,000,000 to a total of 8,601,471. ​ a) 2014 Plans ​ Share-based compensation expense recognized by classification included in the Consolidated statements of operations and comprehensive loss in relation to the 2014 Plans for the periods indicated below was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, ​ Nine months ended September 30, ​ 2020 2019 ​ 2020 ​ 2019 ​ ​ (in thousands) ​ (in thousands) Research and development ​ $ 3,906 ​ $ 1,922 ​ $ 9,177 ​ $ 6,021 Selling, general and administrative ​ ​ 2,457 ​ ​ 1,936 ​ ​ 7,240 ​ ​ 6,691 Total ​ $ 6,363 ​ $ 3,858 ​ $ 16,417 ​ $ 12,712 ​ ​ Share-based compensation expense recognized by award type for the periods indicated below was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, ​ Nine months ended September 30, ​ 2020 2019 ​ 2020 ​ 2019 ​ ​ (in thousands) ​ (in thousands) Award type ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Share options ​ $ 3,994 ​ $ 2,025 ​ $ 8,948 ​ $ 6,105 Restricted share units (“RSUs”) ​ ​ 1,525 ​ ​ 1,075 ​ ​ 5,178 ​ ​ 3,000 Performance share units (“PSUs”) ​ ​ 844 ​ ​ 758 ​ ​ 2,291 ​ ​ 3,607 Total ​ $ 6,363 ​ $ 3,858 ​ $ 16,417 ​ $ 12,712 ​ As of September 30, 2020, the unrecognized share-based compensation expense related to unvested awards under the 2014 Plans were: ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized Weighted average ​ share-based remaining ​ ​ compensation ​ period for ​ ​ expense ​ recognition ​ ​ (in thousands) ​ (in years) Award type ​ ​ ​ ​ ​ Share options ​ $ 25,848 ​ 2.94 Restricted share units ​ ​ 16,351 ​ 2.25 Performance share units ​ ​ 2,462 ​ 1.17 Total ​ $ 44,661 ​ 2.59 ​ The Company satisfies the exercise of share options and vesting of RSUs and PSUs through newly issued ordinary shares. ​ Share options ​ The following table summarizes option activity for the nine months ended September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ Options ​ ​ Number of ​ Weighted average ​ ordinary shares exercise price ​ ​ ​ ​ ​ ​ Outstanding at December 31, 2019 ​ 2,683,104 ​ $ 21.29 Granted ​ 620,077 ​ $ 49.74 Forfeited ​ (145,460) ​ $ 40.59 Expired ​ (275) ​ $ 35.24 Exercised ​ (211,288) ​ $ 16.75 Outstanding at September 30, 2020 ​ 2,946,158 ​ $ 26.64 Thereof, fully vested and exercisable at September 30, 2020 ​ 1,718,941 ​ $ 16.55 Thereof, outstanding and expected to vest after September 30, 2020 ​ 1,227,217 ​ $ 40.79 ​ ​ ​ ​ ​ ​ ​ Total weighted average grant date fair value of options issued during the period (in $ millions) ​ ​ ​ $ 17.4 Proceeds from option sales during the period (in $ millions) ​ ​ ​ $ 3.5 ​ Share options are priced on the date of grant and, except for certain grants made to non-executive directors, vest over a period of four years, the first 25% vests after one year from the grant date and the remainder vests in equal quarterly installments, over years two, three and four. Any options that vest must be exercised by the tenth anniversary of the grant date. The fair value of each option issued is estimated at the respective grant date using the Hull & White option pricing model with the following weighted-average assumptions: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, Nine months ended September 30, Assumptions 2020 2019 2020 2019 Expected volatility ​ 70% ​ 75% ​ 70% ​ 75% Expected terms ​ 10 years ​ 10 years ​ 10 years ​ 10 years Risk free interest rate ​ 0.84% ​ 1.92% ​ 0.76% - 1.44% ​ 1.92% - 2.87% Expected dividend yield ​ 0% ​ 0% ​ 0% ​ 0% ​ Restricted share units (“RSUs”) ​ The following table summarizes the RSUs activity for the nine months ended September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ RSU ​ ​ Weighted average ​ ​ Number of ​ grant-date fair ​ ​ ordinary shares ​ value Non-vested at December 31, 2019 ​ 370,830 ​ $ 28.62 Granted ​ 362,699 ​ $ 48.20 Vested ​ (206,881) ​ $ 24.18 Forfeited ​ (66,457) ​ $ 46.03 Non-vested at September 30, 2020 ​ 460,191 ​ $ 43.53 ​ ​ ​ ​ ​ ​ Total weighted average grant date fair value of RSUs granted during the period (in $ millions) ​ ​ ​ $ 17.5 ​ RSUs vest over one ​ Performance share units (“PSUs”) ​ The following table summarizes the PSUs activity for the nine months ended September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ PSU ​ ​ Weighted average ​ ​ Number of ​ grant-date fair ​ ​ ordinary shares ​ value Non-vested at December 31, 2019 ​ 479,422 ​ $ 21.17 Granted ​ 91,003 ​ $ 57.56 Vested ​ (354,105) ​ $ 17.44 Forfeited ​ (3,706) ​ $ 57.56 Non-vested at September 30, 2020 ​ 212,614 ​ $ 42.32 ​ ​ ​ ​ ​ ​ Total weighted average grant date fair value of PSUs granted during the period (in $ millions) ​ ​ ​ $ 5.2 ​ In January 2019, the Company awarded PSUs to its executives and certain other members of senior management. These PSUs were earned as of January 2020 based on an assessment by the Company’s board of directors of the level of achievement of agreed upon performance targets through December 31, 2019. PSUs vest after three years. ​ b) Employee Share Purchase Plan (“ESPP”) ​ In June 2018, the Company’s shareholders adopted and approved an ESPP allowing the Company to issue up to 150,000 ordinary shares. The ESPP is intended to qualify under Section 423 of the Internal Revenue Code of 1986. Under the ESPP, employees are eligible to purchase ordinary shares through payroll deductions, subject to any plan limitations. The purchase price of the ordinary shares on each purchase date is equal to 85% of the lower of the closing market price on the offering date and the closing market price on the purchase date of each three-month offering period. During the nine months ended September 30, 2020, 3,282 ordinary shares were issued under the ESPP compared to 7,018 during the same period in 2019. As of September 30, 2020, a total of 134,925 ordinary shares remains available for issuance under the ESPP plan compared to a total of 140,391 as of September 30, 2019.

Income taxes

Income taxes	9 Months Ended
	Sep. 30, 2020
Income taxes
Income taxes	9 Income taxes ​ Deferred tax assets and deferred tax liabilities are recognized based on the expected future tax consequences of temporary differences between the financial statement carrying amounts and the income tax basis of assets and liabilities, using current statutory rates. A valuation allowance is recorded against deferred tax assets if it is more likely than not that some or all the deferred tax assets will not be realized. The Company reassessed the need for a full valuation allowance in conjunction with entering into the CSL Behring Agreement. Closing of the CSL Behring Agreement is contingent on the successful completion of reviews under the antitrust laws in the United States, Australia, and the United Kingdom, which has not occurred to date. Closing of the transaction is dependent on the timing, extent and result of the regulatory review process. In its assessment of whether or not it was more likely than not that the Company’s deferred tax assets will be realized, the Company considered all relevant facts and circumstances, including in particular similar regulatory reviews as well as the three-year cumulative losses reported by the Company. The Company concluded that it should continue to record a full valuation allowance as of September 30, 2020. As of December 31, 2019, the Company’s valuation allowance amounted to $109.9 million. ​

Basic and diluted earnings per

Basic and diluted earnings per share	9 Months Ended
	Sep. 30, 2020
Basic and diluted earnings per share
Basic and diluted earnings per share	10 ​ Diluted earnings per share are calculated by adjusting the weighted average number of ordinary shares outstanding, assuming conversion of all potentially dilutive ordinary shares. As the Company has incurred a loss, all potentially dilutive ordinary shares would have an antidilutive effect, if converted, and thus have been excluded from the computation of loss per share. The shares are presented without giving effect to the application of the treasury method or exercise prices that would be above the share price as of September 30, 2020 and September 30, 2019, respectively. In addition, the BMS warrants were not exercisable as of these dates since this would have required the prior designation of Collaboration Targets by BMS. This would generally result in a lower number of potentially dilutive ordinary shares as some stock option grants as well as the BMS warrants would have been excluded. ​ The potentially dilutive ordinary shares are summarized below: ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ 2020 2019 ​ ​ (ordinary shares) BMS warrants ​ 8,071,000 ​ 8,890,000 Stock options under 2014 Plans ​ 2,946,158 ​ 2,860,605 Non-vested RSUs and earned PSUs ​ 672,805 ​ 867,007 Stock options under previous option plan ​ 14,000 ​ 14,000 Employee share purchase plan ​ 1,997 ​ 1,020 Total potential dilutive ordinary shares ​ 11,705,960 ​ 12,632,632 ​

Subsequent events

Subsequent events	9 Months Ended
	Sep. 30, 2020
Subsequent events
Subsequent events	11 ​ None.

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	9 Months Ended
	Sep. 30, 2020
Summary of significant accounting policies
Basis of preparation	2.1 Basis of preparation ​ The Company prepared these unaudited consolidated financial statements in compliance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the SEC regarding interim financial reporting. Any reference in these notes to applicable guidance is meant to refer to authoritative U.S. GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). ​ The unaudited consolidated financial statements are presented in U.S. dollars, except where otherwise indicated. Transactions denominated in currencies other than U.S. dollars are presented in the transaction currency with the U.S. dollar amount included in parenthesis, converted at the foreign exchange rate as of the transaction date.
Unaudited interim financial information	2.2 Unaudited interim financial information ​ The interim financial statements and related disclosures are unaudited, have been prepared on the same basis as the annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair statement of the financial position, results of operations and changes in financial position for the period presented. ​ Certain information and footnote disclosures normally included in annual financial statements prepared in accordance with U.S. GAAP have been omitted. The results of operations for the nine months ended September 30, 2020, are not necessarily indicative of the results to be expected for the full year ending December 31, 2020 or for any other future year or interim period. The accompanying financial statements should be read in conjunction with the audited financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on March 2, 2020
Use of estimates	2.3 Use of estimates ​ The preparation of the financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates.
Accounting policies	2.4 Accounting policies ​ The principal accounting policies applied in the preparation of these unaudited consolidated financial statements are described in the Company’s audited financial statements as of and for the year ended December 31, 2019, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on March 2, 2020
Recent accounting pronouncements	2.5 Recent accounting pronouncements ​ There have been no new accounting pronouncements or changes to accounting pronouncements during the nine months ended September 30, 2020, as compared to the recent accounting pronouncements described in Note 2.3.23 of the Company’s Annual Report on Form 10-K for the year ended December 31, 2019

Collaboration arrangements an_2

Collaboration arrangements and concentration of credit risk (Tables)	9 Months Ended
	Sep. 30, 2020
Collaboration arrangements and concentration of credit risk
Schedule of amounts owed in relation to collaboration	​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2020 2019 ​ ​ (in thousands) Bristol Myers Squibb ​ $ 223 ​ $ 947 Total ​ $ 223 ​ $ 947

Fair value measurement (Tables)

Fair value measurement (Tables)	9 Months Ended
	Sep. 30, 2020
Fair value measurement
Schedule of assets and liabilities measured at fair value on recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quoted prices Significant Significant Total Classification in Consolidated ​ ​ ​ (in thousands) ​ ​ At December 31, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash, cash equivalents and restricted cash ​ $ 380,726 ​ $ — ​ $ — ​ $ 380,726 ​ Cash and cash equivalents; restricted cash Total assets ​ $ 380,726 ​ $ — ​ $ — ​ $ 380,726 ​ ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivative financial instruments - related party ​ ​ — ​ ​ — ​ ​ 3,075 ​ ​ 3,075 ​ ​ Total liabilities ​ $ — ​ $ — ​ $ 3,075 ​ $ 3,075 ​ ​ At September 30, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash, cash equivalents and restricted cash ​ $ 282,207 ​ $ — ​ $ — ​ $ 282,207 ​ Cash and cash equivalents; restricted cash Total assets ​ $ 282,207 ​ $ — ​ $ — ​ $ 282,207 ​ ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivative financial instruments - related party ​ $ — ​ $ — ​ $ 547 ​ $ 547 ​ ​ Total liabilities ​ $ — ​ $ — ​ $ 547 ​ $ 547 ​ ​
Schedule of changes in Level 3 items	​ ​ ​ ​ ​ ​ ​ Derivative ​ ​ financial ​ instruments ​ ​ (in thousands) Balance at December 31, 2019 ​ $ 3,075 Net gains recognized in profit or loss ​ ​ (2,531) Currency translation effects ​ ​ 3 Balance at September 30, 2020 ​ $ 547

Right-of-use asset and lease _2

Right-of-use asset and lease liabilities (Tables)	9 Months Ended
	Sep. 30, 2020
Right-of-use asset and lease liabilities
Schedule of lease cost, balance sheet and cash flow information	The table below presents the components of the Company’s lease costs for the periods indicated: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, Nine months ended September 30, ​ 2020 2019 2020 2019 ​ ​ (in thousands) ​ (in thousands) Operating lease cost ​ $ 1,317 ​ $ 1,264 ​ $ 3,896 ​ $ 3,183 Variable lease cost ​ ​ 155 ​ ​ 131 ​ ​ 453 ​ ​ 313 Sublease income ​ ​ (222) ​ ​ (260) ​ ​ (679) ​ ​ (792) Total lease cost ​ $ 1,250 ​ $ 1,135 ​ $ 3,670 ​ $ 2,704 ​ ​ The table below presents the lease-related assets and liabilities recorded on the Consolidated balance sheets for the periods indicated. ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ ​ 2020 ​ 2019 ​ ​ (in thousands) Assets ​ ​ ​ ​ ​ ​ Operating lease right-of-use assets ​ $ 26,207 ​ ​ 26,797 Liabilities ​ ​ ​ ​ ​ ​ Current ​ ​ ​ ​ ​ ​ Current operating lease liabilities ​ ​ 5,552 ​ ​ 5,865 Non-current ​ ​ ​ ​ ​ ​ Non-current operating lease liabilities ​ ​ 30,333 ​ ​ 31,133 Total lease liabilities ​ $ 35,885 ​ ​ 36,998 ​ Other information ​ The weighted-average remaining lease term as of September 30, 2020 is 9.6 years, compared to 10.3 years as of December 31, 2019 and the weighted-average discount rate as of September 30, 2020 is 11.35%, compared to 11.33% as of December 31, 2019. The Company derived the weighted-average discount rate, adjusted for differences such as in the term and payment patterns, from the Company’s loan from Hercules Capital which was refinanced immediately prior to the January 1, 2019 adoption date in December 2018. ​ Cash paid for amounts included in the measurement of lease liabilities for the periods indicated below was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, Nine months ended September 30, ​ 2020 2019 2020 2019 ​ (in thousands) ​ (in thousands) Operating cash flows for operating leases 1) $ 1,401 ​ $ 1,761 ​ $ 4,556 ​ $ 3,777
Schedule of undiscounted cash flows and minimum lease payments	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Lexington ​ Amsterdam 1) ​ Other 1) ​ Total ​ (in thousands) 2020 (three months remaining) $ 848 ​ $ 494 ​ $ — ​ $ 1,342 2021 ​ 3,455 ​ ​ 1,978 ​ ​ 148 ​ ​ 5,581 2022 ​ 3,552 ​ ​ 1,978 ​ ​ — ​ ​ 5,530 2023 ​ 3,650 ​ ​ 1,978 ​ ​ — ​ ​ 5,628 2024 ​ 4,146 ​ ​ 1,978 ​ ​ — ​ ​ 6,124 Thereafter ​ 20,745 ​ ​ 13,678 ​ ​ — ​ ​ 34,423 Total lease payments $ 36,396 ​ $ 22,084 ​ $ 148 ​ $ 58,628 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less: amount of lease payments representing interest payments ​ (13,180) ​ ​ (9,558) ​ ​ (5) ​ ​ (22,743) Present value of lease payments ​ 23,216 ​ ​ 12,526 ​ ​ 143 ​ ​ 35,885 Less: current operating lease liabilities ​ (3,431) ​ ​ (1,978) ​ ​ (143) ​ ​ (5,552) Non-current operating lease liabilities $ 19,785 ​ $ 10,548 ​ $ — ​ $ 30,333 ​ ( 1)

Accrued expenses and other cu_2

Accrued expenses and other current liabilities (Tables)	9 Months Ended
	Sep. 30, 2020
Accrued expenses and other current liabilities
Schedule of accrued expenses and other current liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2020 2019 ​ ​ (in thousands) Accruals for services provided by vendors-not yet billed ​ $ 9,206 ​ $ 5,425 Personnel related accruals and liabilities ​ ​ 8,578 ​ ​ 7,032 Total ​ $ 17,784 ​ $ 12,457

Share-based compensation (Table

Share-based compensation (Tables)	9 Months Ended
	Sep. 30, 2020
Share-based compensation
Schedule of share-based compensation expense by classification included in consolidated statements of operations and comprehensive loss	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, ​ Nine months ended September 30, ​ 2020 2019 ​ 2020 ​ 2019 ​ ​ (in thousands) ​ (in thousands) Research and development ​ $ 3,906 ​ $ 1,922 ​ $ 9,177 ​ $ 6,021 Selling, general and administrative ​ ​ 2,457 ​ ​ 1,936 ​ ​ 7,240 ​ ​ 6,691 Total ​ $ 6,363 ​ $ 3,858 ​ $ 16,417 ​ $ 12,712
Schedule of share-based compensation expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, ​ Nine months ended September 30, ​ 2020 2019 ​ 2020 ​ 2019 ​ ​ (in thousands) ​ (in thousands) Award type ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Share options ​ $ 3,994 ​ $ 2,025 ​ $ 8,948 ​ $ 6,105 Restricted share units (“RSUs”) ​ ​ 1,525 ​ ​ 1,075 ​ ​ 5,178 ​ ​ 3,000 Performance share units (“PSUs”) ​ ​ 844 ​ ​ 758 ​ ​ 2,291 ​ ​ 3,607 Total ​ $ 6,363 ​ $ 3,858 ​ $ 16,417 ​ $ 12,712
Schedule of unrecognized compensation cost related to unvested awards	​ ​ ​ ​ ​ ​ ​ ​ Unrecognized Weighted average ​ share-based remaining ​ ​ compensation ​ period for ​ ​ expense ​ recognition ​ ​ (in thousands) ​ (in years) Award type ​ ​ ​ ​ ​ Share options ​ $ 25,848 ​ 2.94 Restricted share units ​ ​ 16,351 ​ 2.25 Performance share units ​ ​ 2,462 ​ 1.17 Total ​ $ 44,661 ​ 2.59
Schedule of weighted-average assumptions for fair value of option issued	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, Nine months ended September 30, Assumptions 2020 2019 2020 2019 Expected volatility ​ 70% ​ 75% ​ 70% ​ 75% Expected terms ​ 10 years ​ 10 years ​ 10 years ​ 10 years Risk free interest rate ​ 0.84% ​ 1.92% ​ 0.76% - 1.44% ​ 1.92% - 2.87% Expected dividend yield ​ 0% ​ 0% ​ 0% ​ 0%
Summary of RSUs activity	​ ​ ​ ​ ​ ​ ​ ​ ​ RSU ​ ​ Weighted average ​ ​ Number of ​ grant-date fair ​ ​ ordinary shares ​ value Non-vested at December 31, 2019 ​ 370,830 ​ $ 28.62 Granted ​ 362,699 ​ $ 48.20 Vested ​ (206,881) ​ $ 24.18 Forfeited ​ (66,457) ​ $ 46.03 Non-vested at September 30, 2020 ​ 460,191 ​ $ 43.53 ​ ​ ​ ​ ​ ​ Total weighted average grant date fair value of RSUs granted during the period (in $ millions) ​ ​ ​ $ 17.5
Summary of PSUs activity	​ ​ ​ ​ ​ ​ ​ ​ ​ PSU ​ ​ Weighted average ​ ​ Number of ​ grant-date fair ​ ​ ordinary shares ​ value Non-vested at December 31, 2019 ​ 479,422 ​ $ 21.17 Granted ​ 91,003 ​ $ 57.56 Vested ​ (354,105) ​ $ 17.44 Forfeited ​ (3,706) ​ $ 57.56 Non-vested at September 30, 2020 ​ 212,614 ​ $ 42.32 ​ ​ ​ ​ ​ ​ Total weighted average grant date fair value of PSUs granted during the period (in $ millions) ​ ​ ​ $ 5.2
2014 Plan
Share-based compensation
Summary of option activity	​ ​ ​ ​ ​ ​ ​ ​ ​ Options ​ ​ Number of ​ Weighted average ​ ordinary shares exercise price ​ ​ ​ ​ ​ ​ Outstanding at December 31, 2019 ​ 2,683,104 ​ $ 21.29 Granted ​ 620,077 ​ $ 49.74 Forfeited ​ (145,460) ​ $ 40.59 Expired ​ (275) ​ $ 35.24 Exercised ​ (211,288) ​ $ 16.75 Outstanding at September 30, 2020 ​ 2,946,158 ​ $ 26.64 Thereof, fully vested and exercisable at September 30, 2020 ​ 1,718,941 ​ $ 16.55 Thereof, outstanding and expected to vest after September 30, 2020 ​ 1,227,217 ​ $ 40.79 ​ ​ ​ ​ ​ ​ ​ Total weighted average grant date fair value of options issued during the period (in $ millions) ​ ​ ​ $ 17.4 Proceeds from option sales during the period (in $ millions) ​ ​ ​ $ 3.5 ​

Basic and diluted earnings pe_2

Basic and diluted earnings per share (Tables)	9 Months Ended
	Sep. 30, 2020
Basic and diluted earnings per share
Schedule of potential dilutive common shares	​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ 2020 2019 ​ ​ (ordinary shares) BMS warrants ​ 8,071,000 ​ 8,890,000 Stock options under 2014 Plans ​ 2,946,158 ​ 2,860,605 Non-vested RSUs and earned PSUs ​ 672,805 ​ 867,007 Stock options under previous option plan ​ 14,000 ​ 14,000 Employee share purchase plan ​ 1,997 ​ 1,020 Total potential dilutive ordinary shares ​ 11,705,960 ​ 12,632,632

Collaboration arrangements an_3

Collaboration arrangements and concentration of credit risk - BMS collaboration - Narrative (Details) $ in Thousands	Jun. 24, 2020USD ($)	May 21, 2015USD ($)	Feb. 28, 2019	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)item	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Collaboration arrangements
Revenue				$ 1,789	$ 1,046	$ 3,428	$ 4,656
CSL Behring collaboration
Collaboration arrangements
Upfront cash to receive upon the closing of the agreement	$ 450,000					450,000
Regulatory and commercial milestone payments received	$ 1,600,000
CSL Behring collaboration | Transaction Payment Received in 2020
Collaboration arrangements
Upfront cash to receive upon the closing of the agreement						$ 450,000
Tax rate enacted in the Netherlands						25.00%
CSL Behring collaboration | Transaction payment received thereafter
Collaboration arrangements
Upfront cash to receive upon the closing of the agreement						$ 450,000
License revenues from related party
Collaboration arrangements
Revenue				1,776	842	3,353	3,507
Collaboration revenues from related party
Collaboration arrangements
Revenue				$ 13	$ 204	75	$ 1,149
BMS arrangement
Collaboration arrangements
Revenue						$ 223		$ 947
BMS arrangement | Bristol Myers Squibb
Collaboration arrangements
Initial research term						4 years
Number of potential targets included in collaborative agreement | item						10
Extension for research term			1 year
Number of collaboration targets | item						4
License revenue | Bristol Myers Squibb
Collaboration arrangements
Upfront payment recorded		$ 60,100
Expected completion of pre-clinical phase						4 years
Average period for completion of clinical development and commercial launch						8 years 6 months
License revenue | Bristol Myers Squibb | Second, Third, and Fourth Targets Selection
Collaboration arrangements
Target designation payment received		$ 15,000
License revenue | Bristol Myers Squibb | Fifth through Tenth Targets Selection
Collaboration arrangements
Milestone payments to be received upon achievement						$ 16,500
License revenue | Bristol Myers Squibb | Other Selected Targets
Collaboration arrangements
Milestone payments to be received upon achievement						$ 217,000
License revenue | License revenues from related party
Collaboration arrangements
Royalty term after the first commercial sale						10 years

Collaboration arrangements an_4

Collaboration arrangements and concentration of credit risk - Amounts owed by BMS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Number of ordinary shares held	44,487,510		44,487,510		43,711,954
Amounts owed in relation to the collaboration services	$ 223		$ 223		$ 947
Total revenues	1,789	$ 1,046	3,428	$ 4,656
BMS arrangement
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues			223		947
BMS arrangement | Bristol Myers Squibb
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Amounts owed in relation to the collaboration services	$ 223		$ 223		$ 947

Fair value measurement - Assets

Fair value measurement - Assets and liabilities measured on a recurring basis (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	$ 282,207	$ 380,726
Total assets	282,207	380,726
Liabilities, Fair Value Disclosure [Abstract]
Total liabilities	547	3,075
Related party
Liabilities, Fair Value Disclosure [Abstract]
Derivative financial instruments	547	3,075
Fair value hierarchy Level 1
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	282,207	380,726
Total assets	282,207	380,726
Level 3
Liabilities, Fair Value Disclosure [Abstract]
Total liabilities	547	3,075
Level 3 | Related party
Liabilities, Fair Value Disclosure [Abstract]
Derivative financial instruments	$ 547	$ 3,075

Fair value measurement - Change

Fair value measurement - Changes in Level 3 items (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)
Changes in Level 3 liabilities
Beginning Balance	$ 3,100
Ending Balance	500
Derivative financial instruments | Level 3
Changes in Level 3 liabilities
Beginning Balance	3,075
Net losses recognized in profit or loss	(2,531)
Currency translation effects	(3)
Ending Balance	$ 547

Fair value measurement - BMS wa

Fair value measurement - BMS warrants - Narrative (Details) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)item$ / shares	Dec. 31, 2019USD ($)	Apr. 06, 2015$ / shares
Collaboration arrangements
Number of warrant types	2
Fair value of derivative financial instruments | $	$ 0.5	$ 3.1
BMS Warrants
Collaboration arrangements
Exercise price in respect of each warrant | $ / shares	$ 56.41		$ 33.84
Number of trading days used to calculate Volume Weighted Average Price ("VWAP")	20 days
Number of days prior to purchase or exercise used to calculate Volume Weighted Average Price ("VWAP")	5 days
Compounded annual growth rate used to determine fair value of exercise price	10.00%
BMS Warrants | Minimum
Collaboration arrangements
Period in which the exercise of warrants is expected to occur after balance sheet date (in years)	3 years
BMS Warrants | Maximum
Collaboration arrangements
Period in which the exercise of warrants is expected to occur after balance sheet date (in years)	5 years
BMS First Warrant | Minimum
Collaboration arrangements
Probability of the occurrence of events allowing warrant exercises	0.00%
BMS First Warrant | Maximum
Collaboration arrangements
Probability of the occurrence of events allowing warrant exercises	44.00%
BMS First Warrant | Weighted average input
Collaboration arrangements
Probability of the occurrence of events allowing warrant exercises	24.00%
BMS Second Warrant | Minimum
Collaboration arrangements
Probability of the occurrence of events allowing warrant exercises	0.00%
BMS Second Warrant | Maximum
Collaboration arrangements
Probability of the occurrence of events allowing warrant exercises	11.00%
BMS Second Warrant | Weighted average input
Collaboration arrangements
Probability of the occurrence of events allowing warrant exercises	5.00%
uniQure N.V. | Bristol Myers Squibb | First Six New Targets Or Designation Of Sixth Target
Collaboration arrangements
Ownership percentage required per agreement	14.90%
uniQure N.V. | Bristol Myers Squibb | First Nine New Targets Or Designation Of Ninth Target
Collaboration arrangements
Ownership percentage required per agreement	19.90%
BMS arrangement | BMS Warrants
Collaboration arrangements
Additional change in fair value of derivatives | $	$ (0.7)
BMS arrangement | Bristol Myers Squibb
Collaboration arrangements
Number of potential targets included in collaborative agreement	10
Number of Collaboration Targets	4
Number of Collaboration Targets actually are designated	4
BMS arrangement | Bristol Myers Squibb | First Six New Targets Or Designation Of Sixth Target
Collaboration arrangements
Number of potential targets included in collaborative agreement	7
Number of Collaboration Targets	6
BMS arrangement | Bristol Myers Squibb | First Nine New Targets Or Designation Of Ninth Target
Collaboration arrangements
Number of potential targets included in collaborative agreement	10
Number of Collaboration Targets	9

Right-of-use asset and lease _3

Right-of-use asset and lease liabilities - Narrative (Details) € in Millions, $ in Millions	1 Months Ended	9 Months Ended
	Nov. 30, 2018item	Sep. 30, 2020USD ($)	Sep. 30, 2020EUR (€)	Dec. 31, 2019	Jun. 30, 2019ft²	Dec. 01, 2017	Jun. 30, 2016	Mar. 31, 2016
Leases
Area of facility (in square feet) | ft²					30,655
Weighted-average remaining lease term, Operating leases		9 years 7 months 6 days	9 years 7 months 6 days	10 years 3 months 18 days
Weighted-average discount rate, Operating leases		11.35%	11.35%	11.33%
Lexington
Leases
Lease term (in years)	5 years
Number of subsequent renewals | item	2
Renewal term (in years)	5 years
Amsterdam
Leases
Lease term (in years)						10 years		16 years
Renewal term (in years)							5 years
Minimum rentals to be received		$ 6.4	€ 5.5

Right-of-use asset and lease _4

Right-of-use asset and lease liabilities - Operating lease liabilities (Details) $ in Thousands	Dec. 01, 2017floor	Feb. 29, 2020floor	Dec. 31, 2017floor	Sep. 30, 2020USD ($)$ / €	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)$ / €	Sep. 30, 2019USD ($)	Dec. 31, 2017floor	Dec. 31, 2019USD ($)	Jan. 01, 2019USD ($)
Components of lease cost
Operating lease cost				$ 1,317	$ 1,264	$ 3,896	$ 3,183
Variable lease cost				155	131	453	313
Sublease income				(222)	(260)	(679)	(792)
Total lease cost				1,250	1,135	3,670	2,704
Incentive payments					500		500
Assets
Operating lease right-of-use assets				26,207		26,207			$ 26,797	$ 19,000
Right-of-use assets in exchange for lease obligations					400		9,000
Current liabilities
Current operating lease liability				5,552		5,552			5,865
Non-current liabilities
Non-current operating lease liability				30,333		30,333			31,133
Total lease liabilities				$ 35,885		$ 35,885			$ 36,998
Weighted-average remaining lease term, Operating leases				9 years 7 months 6 days		9 years 7 months 6 days			10 years 3 months 18 days
Weighted-average discount rate, Operating leases				11.35%		11.35%			11.33%
Supplemental cash flow information related to leases
Cash paid for amounts included in the measurement of lease liabilities, Operating cash flows for operating leases				$ 1,401	1,761	$ 4,556	3,777
Right-of-use asset obtained in exchange for lease obligation
Right-of-use assets in exchange for lease obligations					$ 400		$ 9,000
Undiscounted Cash Flows
2020 (three months remaining)				1,342		1,342
2021				5,581		5,581
2022				5,530		5,530
2023				5,628		5,628
2024				6,124		6,124
Thereafter				34,423		34,423
Total minimum lease payments				58,628		58,628
Less: amount of lease payments representing interest				(22,743)		(22,743)
Total lease liabilities				35,885		35,885			$ 36,998
Less: current obligations under operating leases				(5,552)		(5,552)			(5,865)
Non-current operating lease liability				$ 30,333		$ 30,333			$ 31,133
Exchange rate (in USD per Euro) | $ / €				1.17		1.17
Lexington
Current liabilities
Current operating lease liability				$ 3,431		$ 3,431
Non-current liabilities
Non-current operating lease liability				19,785		19,785
Total lease liabilities				23,216		23,216
Undiscounted Cash Flows
2020 (three months remaining)				848		848
2021				3,455		3,455
2022				3,552		3,552
2023				3,650		3,650
2024				4,146		4,146
Thereafter				20,745		20,745
Total minimum lease payments				36,396		36,396
Less: amount of lease payments representing interest				(13,180)		(13,180)
Total lease liabilities				23,216		23,216
Less: current obligations under operating leases				(3,431)		(3,431)
Non-current operating lease liability				19,785		$ 19,785
Amsterdam
Components of lease cost
Lessee, option to extend						true
Number of floor of the facility | floor	7
Number of floors to sub-lease | floor			3					3
Number of floor to take back from the sub-lease | floor		1
Lessor, option to extend						true
Current liabilities
Current operating lease liability				1,978		$ 1,978
Non-current liabilities
Non-current operating lease liability				10,548		10,548
Total lease liabilities				12,526		12,526
Undiscounted Cash Flows
2020 (three months remaining)				494		494
2021				1,978		1,978
2022				1,978		1,978
2023				1,978		1,978
2024				1,978		1,978
Thereafter				13,678		13,678
Total minimum lease payments				22,084		22,084
Less: amount of lease payments representing interest				(9,558)		(9,558)
Total lease liabilities				12,526		12,526
Less: current obligations under operating leases				(1,978)		(1,978)
Non-current operating lease liability				10,548		10,548
Other
Current liabilities
Current operating lease liability				143		143
Non-current liabilities
Total lease liabilities				143		143
Undiscounted Cash Flows
2021				148		148
Total minimum lease payments				148		148
Less: amount of lease payments representing interest				(5)		(5)
Total lease liabilities				143		143
Less: current obligations under operating leases				$ (143)		$ (143)

Accrued expenses and other cu_3

Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accrued expenses and other current liabilities
Accruals for services provided by vendors-not yet billed	$ 9,206	$ 5,425
Personnel related accruals and liabilities	8,578	7,032
Total	$ 17,784	$ 12,457

Long-term debt (Details)

Long-term debt (Details) - USD ($) $ in Millions	Dec. 06, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	May 31, 2020	Dec. 31, 2019
2016 Amended Facility | Hercules | Second Amended and Restated Loan and Security Agreement [Member]
Long-term Debt
Outstanding debt	$ 20
Back-end fees due						$ 1
2018 Amended Facility | Hercules
Long-term Debt
Aggregate amount of Equity Financing				$ 90
Foreign currency loss					$ 1.7
Foreign currency gain		$ 1.5	$ 1.5	1.5
2018 Amended Facility | Hercules | Second Amended and Restated Loan and Security Agreement [Member]
Long-term Debt
Outstanding debt	$ 35	35		35			$ 35
Interest rate (as a percent)	8.85%
Back-end fee (as a percent)	4.95%
Borrowing capacity subject to discretion		15		$ 15
Additional unconditional borrowing capacity	$ 15
Proceeds from loan increment	$ 15
Facility fee (as a percent)	0.50%
2018 Amended Facility | Prime Rate | Hercules | Second Amended and Restated Loan and Security Agreement [Member]
Long-term Debt
Variable interest rate basis	8.85%
Discount rate (as a percent)	5.50%
Venture debt loan facility | 2018 Amended Facility
Long-term Debt
Minimum cash and cash equivalents in U.S. bank accounts				65.00%
Assets pledged to secure facilities by directly or indirectly				$ 350.6
Assets not being pledged to secure facilities by directly or indirectly				98
Aggregate maturities of loan
Long-term debt		35.8		35.8			$ 36.3
Venture debt loan facility | 2018 Amended Facility | Hercules
Long-term Debt
Interest expense recorded		$ 0.9	$ 0.9	$ 2.7	$ 2.8

Share-based compensation - Summ

Share-based compensation - Summary of share-based compensation expense and unrecognized costs (Details) - 2014 Plan - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Share-based compensation
Authorized shares	8,601,471
Increase in authorized shares	3,000,000
Share-based compensation expense		$ 6,363	$ 3,858	$ 16,417	$ 12,712
Unrecognized compensation costs		44,661		$ 44,661
Weighted-average remaining period for recognition (in years)				2 years 7 months 2 days
Research and development expenses
Share-based compensation
Share-based compensation expense		3,906	1,922	$ 9,177	6,021
Selling, general and administrative expense
Share-based compensation
Share-based compensation expense		2,457	1,936	7,240	6,691
Share options
Share-based compensation
Share-based compensation expense		$ 3,994	2,025	$ 8,948	6,105
Outstanding of fully vested share options		2,946,158		2,946,158		2,683,104
Unrecognized compensation costs		$ 25,848		$ 25,848
Weighted-average remaining period for recognition (in years)				2 years 11 months 8 days
Restricted share units ("RSUs")
Share-based compensation
Share-based compensation expense		1,525	1,075	$ 5,178	3,000
Unrecognized compensation costs		16,351		$ 16,351
Weighted-average remaining period for recognition (in years)				2 years 3 months
Performance share units ("PSUs")
Share-based compensation
Share-based compensation expense		844	$ 758	$ 2,291	$ 3,607
Unrecognized compensation costs		$ 2,462		$ 2,462
Weighted-average remaining period for recognition (in years)				1 year 2 months 1 day

Share-based compensation - Opti

Share-based compensation - Option activity and weighted-average assumptions (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Weighted average exercise price
Total weighted average grant date fair value of options issued during the period (in $ millions)				$ 17.4
Proceeds from option sales during the period (in $ millions)				$ 3.5
2014 Plan
Weighted-average assumptions used to estimate fair value of share options granted during year
Increase in authorized shares	3,000,000
2014 Plan | Share options
Options
Outstanding at beginning of year (in shares)				2,683,104
Granted (in shares)				620,077
Forfeited (in shares)				(145,460)
Expired (in shares)				(275)
Exercised (in shares)				(211,288)
Outstanding at end of year (in shares)		2,946,158		2,946,158
Thereof, fully vested and exercisable at end of period (in shares)		1,718,941		1,718,941
Thereof, outstanding and expected to vest at end of period (in shares)		1,227,217		1,227,217
Weighted average exercise price
Outstanding at beginning of year (in dollars per share)				$ 21.29
Granted (in dollars per share)				49.74
Forfeited (in dollars per share)				40.59
Expired (in dollars per share)				35.24
Exercised (in dollars per share)				16.75
Outstanding at end of year (in dollars per share)		$ 26.64		26.64
Thereof, fully vested and exercisable at end of year (in dollars per share)		$ 16.55		16.55
Outstanding and expected to vest at end of year (in dollars per share)				$ 40.79
Weighted-average assumptions used to estimate fair value of share options granted during year
Expected volatility (as a percent)		70.00%	75.00%	70.00%	75.00%
Expected terms (in years)		10 years	10 years	10 years	10 years
Risk free interest rate, minimum (as a percent)		0.84%	1.92%	0.76%	1.92%
Risk free interest rate, maximum (as a percent)				1.44%	2.87%
Expected dividend (as a percent)		0.00%	0.00%	0.00%	0.00%
2014 Plan | Non-executive directors
Weighted average exercise price
Vesting percentage per year				25.00%
Vesting period (in years)				4 years
2014 Plan | One year from grant date
Weighted average exercise price
Vesting period (in years)				1 year

Share-based compensation - RSU

Share-based compensation - RSU activity (Details) - 2014 Plan - $ / shares	1 Months Ended	9 Months Ended
	Mar. 31, 2017	Sep. 30, 2020
Non-executive directors
Other disclosure
Vesting period (in years)		4 years
Restricted share units ("RSUs")
Number of shares
Non-vested at beginning of year (in shares)		370,830
Restricted stock granted (in shares)		362,699
Vested (in shares)		(206,881)
Forfeited (in shares)		(66,457)
Non-vested at end of year (in shares)		460,191
Weighted average grant-date fair value
Non-vested at beginning of year (in dollars per share)		$ 28.62
Granted (in dollars per share)		48.20
Vested (in dollars per share)		24.18
Forfeited (in dollars per share)		46.03
Non-vested at end of year (in dollars per share)		43.53
Restricted share units ("RSUs") | Non-executive directors
Other disclosure
Vesting period (in years)	1 year
Restricted share units ("RSUs") | Directors and Officers
Weighted average grant-date fair value
Granted (in dollars per share)		$ 17,500,000
Minimum | Restricted share units ("RSUs")
Other disclosure
Vesting period (in years)		1 year
Maximum | Restricted share units ("RSUs")
Other disclosure
Vesting period (in years)		3 years

Share-based compensation - PSU

Share-based compensation - PSU activity (Details) - Performance share units ("PSUs") $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)$ / sharesshares
Other disclosure
Vesting period (in years)	3 years
2014 Plan
Number of shares
Non-vested at beginning of year (in shares) | shares	479,422
Restricted stock granted (in shares) | shares	91,003
Vested (in shares) | shares	(354,105)
Forfeited (in shares) | shares	(3,706)
Non-vested at end of year (in shares) | shares	212,614
Weighted average grant-date fair value
Non-vested at beginning of year (in dollars per share) | $ / shares	$ 21.17
Granted (in dollars per share) | $ / shares	57.56
Vested (in dollars per share) | $ / shares	17.44
Forfeited (in dollars per share) | $ / shares	57.56
Non-vested at end of year (in dollars per share) | $ / shares	$ 42.32
Other disclosure
Total weighted average grant date fair value of RSUs granted during the period (in millions) | $	$ 5.2

Share-based compensation - Empl

Share-based compensation - Employee Share Purchase Plan - Narrative (Details) - ESPP - Employee Stock [Member] - shares	1 Months Ended	9 Months Ended
	Jun. 30, 2018	Sep. 30, 2020	Sep. 30, 2019
Share-based compensation
Ordinary shares available for issue	150,000	134,925	140,391
Discounted rate for purchase of shares	85.00%
Number of shares issued		3,282	7,018

Income taxes - Significant comp

Income taxes - Significant components of deferred taxes (Details) $ in Millions	Dec. 31, 2019USD ($)
Deferred tax assets:
Valuation allowance	$ 109.9

Basic and diluted earnings pe_3

Basic and diluted earnings per share (Details) - shares	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Basic and diluted earnings per share
Total potential dilutive ordinary shares	11,705,960	12,632,632
BMS Warrants | Bristol Myers Squibb
Basic and diluted earnings per share
Total potential dilutive ordinary shares	8,071,000	8,890,000
Stock options | 2014 Plan
Basic and diluted earnings per share
Total potential dilutive ordinary shares	2,946,158	2,860,605
Stock options | Previous option plan
Basic and diluted earnings per share
Total potential dilutive ordinary shares	14,000	14,000
Stock options | ESPP
Basic and diluted earnings per share
Total potential dilutive ordinary shares	1,997	1,020
Non-vested and earned RSUs and PSUs
Basic and diluted earnings per share
Total potential dilutive ordinary shares	672,805	867,007