MeiraGTx (MGTX) 10-Q 6 Aug 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Jul. 31, 2020
Document And Entity Information [Abstract]
Entity Registrant Name	MeiraGTx Holdings plc
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Entity File Number	001-38520
Document Period End Date	Jun. 30, 2020
Security Exchange Name	NASDAQ
Entity Address, Address Line One	450 East 29th Street
Entity Address, Address Line Two	14th Floor
Entity Address, City or Town	New York
Entity Address, State or Province	NY
City Area Code	646
Local Phone Number	860-7985
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		37,362,916
Entity Central Index Key	0001735438
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Title of 12(b) Security	Ordinary Shares
Trading Symbol	MGTX

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)	Jun. 30, 2020	Dec. 31, 2019
CURRENT ASSETS:
Cash and cash equivalents	$ 194,811,181	$ 227,233,384
Accounts receivable - related party	24,432,392	23,337,377
Prepaid expenses	7,318,772	4,464,085
Tax incentive receivable	6,777,863	11,974,437
Other current assets	1,868,559	1,970,585
Total Current Assets	235,208,767	268,979,868
Property and equipment, net	27,807,875	23,858,108
Security deposits	705,515	951,138
In-process research and development	774,727	777,655
Restricted cash		123,376
Other assets	194,318	195,053
Right-of-use assets	25,920,174	29,002,448
TOTAL ASSETS	290,611,376	323,887,646
CURRENT LIABILITIES:
Accounts payable	3,089,350	3,759,339
Accrued expenses	18,491,860	18,083,757
Lease obligations, current	2,137,788	1,674,210
Deferred revenue - related party, current	23,003,106	25,678,515
Total Current Liabilities	46,722,104	49,195,821
Deferred revenue - related party	50,691,547	60,535,576
Lease obligations	18,555,378	21,504,340
Asset retirement obligations	1,682,515	1,654,755
Deferred income tax liability	194,318	195,053
TOTAL LIABILITIES	117,845,862	133,085,545
COMMITMENTS
SHAREHOLDERS' EQUITY:
Ordinary Shares, $0.00003881 par value, 1,288,327,750 authorized, 37,362,416 and 36,791,906 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively	1,451	1,429
Capital in excess of par value	414,229,672	395,630,666
Accumulated other comprehensive income (loss)	2,669,474	(1,794,042)
Accumulated deficit	(244,135,083)	(203,035,952)
Total Shareholders' Equity	172,765,514	190,802,101
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 290,611,376	$ 323,887,646

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.00003881	$ 0.00003881
Common stock, shares authorized	1,288,327,750	1,288,327,750
Common stock, shares issued	37,362,416	36,791,906
Common stock, shares outstanding	37,362,416	36,791,906

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
License revenue - related party	$ 2,473,705	$ 1,981,676	$ 6,683,281	$ 2,766,636
Operating expenses:
General and administrative	11,497,270	13,437,171	23,303,404	21,936,646
Research and development	16,202,065	9,771,754	24,285,405	22,747,983
Total operating expenses	27,699,335	23,208,925	47,588,809	44,684,629
Loss from operations	(25,225,630)	(21,227,249)	(40,905,528)	(41,917,993)
Other non-operating income (expense):
Foreign currency (loss) gain	(351,863)	283,175	(1,108,567)	3,001,575
Interest income	193,604	39,726	982,975	39,726
Interest expense	(34,045)	(9,454)	(68,011)	(19,028)
Loss before income taxes	(25,417,934)	(20,913,802)	(41,099,131)	(38,895,720)
Benefit for income taxes		91,390		91,390
Net loss	(25,417,934)	(20,822,412)	(41,099,131)	(38,804,330)
Other comprehensive income:
Foreign currency translation gain, net of tax of $0, for the three-month and six-month periods ended June 30, 2020, and $91,390 for the three-month and six-month periods ended June 30, 2019	517,592	1,579,882	4,463,516	446,199
Total comprehensive loss	(24,900,342)	(19,242,530)	(36,635,615)	(38,358,131)
Net loss	$ (25,417,934)	$ (20,822,412)	$ (41,099,131)	$ (38,804,330)
Basic and diluted net loss per ordinary share	$ (0.69)	$ (0.63)	$ (1.12)	$ (1.26)
Weighted-average number of ordinary shares outstanding	36,969,682	32,827,029	36,797,316	30,814,639

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Parenthetical) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Foreign currency translation, tax	$ 0	$ 91,390	$ 0	$ 91,390

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY - USD ($)	Ordinary Shares [Member]Private Placement [Member]	Ordinary Shares [Member]License Agreement [Member]	Ordinary Shares [Member]	Capital in Excess of Par Value [Member]Private Placement [Member]	Capital in Excess of Par Value [Member]License Agreement [Member]	Capital in Excess of Par Value [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Private Placement [Member]	License Agreement [Member]	Total
Beginning Balance at Dec. 31, 2018			$ 1,064			$ 229,054,460	$ 293,666	$ (148,289,717)			$ 81,059,473
Beginning Balance, Shares at Dec. 31, 2018			27,386,632
Issuance of ordinary shares in connection with a license agreement		$ 6			$ 1,966,334					$ 1,966,340
Issuance of ordinary shares in connection with a license agreement, shares		158,832
Sale of ordinary shares in connection with private placement, net of issuance costs of $2,426,953	$ 225			$ 77,572,822					$ 77,573,047
Sale of ordinary shares in connection with private placement, net of issuance costs, shares	5,797,102
Share-based compensation						2,934,991					2,934,991
Foreign currency translation							(1,133,683)				(1,133,683)
Net loss								(17,981,918)			(17,981,918)
Balance at Mar. 31, 2019			$ 1,295			311,528,607	(840,017)	(166,271,635)			144,418,250
Balance, Shares at Mar. 31, 2019			33,342,566
Beginning Balance at Dec. 31, 2018			$ 1,064			229,054,460	293,666	(148,289,717)			81,059,473
Beginning Balance, Shares at Dec. 31, 2018			27,386,632
Foreign currency translation											446,199
Net loss											(38,804,330)
Balance at Jun. 30, 2019			$ 1,295			315,915,997	739,865	(187,094,047)			129,563,110
Balance, Shares at Jun. 30, 2019			33,342,791
Beginning Balance at Mar. 31, 2019			$ 1,295			311,528,607	(840,017)	(166,271,635)			144,418,250
Beginning Balance, Shares at Mar. 31, 2019			33,342,566
Exercised stock options						1,267					1,267
Exercised stock options, shares			225
Share-based compensation						4,386,123					4,386,123
Foreign currency translation							1,579,882				1,579,882
Net loss								(20,822,412)			(20,822,412)
Balance at Jun. 30, 2019			$ 1,295			315,915,997	739,865	(187,094,047)			129,563,110
Balance, Shares at Jun. 30, 2019			33,342,791
Beginning Balance at Dec. 31, 2019			$ 1,429			395,630,666	(1,794,042)	(203,035,952)			190,802,101
Beginning Balance, Shares at Dec. 31, 2019			36,791,906
Exercised stock options			$ 1			175,076					175,077
Exercised stock options, shares			26,010
Share-based compensation						5,682,881					5,682,881
Foreign currency translation							3,945,924				3,945,924
Net loss								(15,681,197)			(15,681,197)
Balance at Mar. 31, 2020			$ 1,430			401,488,623	2,151,882	(218,717,149)			184,924,786
Balance, Shares at Mar. 31, 2020			36,817,916
Beginning Balance at Dec. 31, 2019			$ 1,429			395,630,666	(1,794,042)	(203,035,952)			$ 190,802,101
Beginning Balance, Shares at Dec. 31, 2019			36,791,906
Exercised stock options, shares											26,010
Foreign currency translation											$ 4,463,516
Net loss											(41,099,131)
Balance at Jun. 30, 2020			$ 1,451			414,229,672	2,669,474	(244,135,083)			172,765,514
Balance, Shares at Jun. 30, 2020			37,362,416
Beginning Balance at Mar. 31, 2020			$ 1,430			401,488,623	2,151,882	(218,717,149)			184,924,786
Beginning Balance, Shares at Mar. 31, 2020			36,817,916
Share-based compensation						5,056,069					5,056,069
Issuance of shares in connection with asset acquisitions			$ 21			7,684,980					7,685,001
Issuance of shares in connection with asset acquisitions, shares			544,500
Foreign currency translation							517,592				517,592
Net loss								(25,417,934)			(25,417,934)
Balance at Jun. 30, 2020			$ 1,451			$ 414,229,672	$ 2,669,474	$ (244,135,083)			$ 172,765,514
Balance, Shares at Jun. 30, 2020			37,362,416

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY (Parenthetical)	3 Months Ended
	Mar. 31, 2019USD ($)
Statement of Stockholders' Equity [Abstract]
Stock issuance costs	$ 2,426,953

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (41,099,131)	$ (38,804,330)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Ordinary shares issued in connection with license agreements		1,966,340
Share-based compensation expense	10,738,950	7,321,114
Foreign currency loss (gain)	1,108,567	(3,001,575)
Depreciation	1,755,739	1,036,283
Lease obligations	142,961	(19,454)
Loss on disposal of equipment, furniture and fixtures	105,716
Gain on termination of lease liability	(143,589)
Amortization of interest on asset retirement obligations	66,385	5,277
Issuance of shares in connection with asset acquisition	7,685,001
Benefit for income taxes		(91,390)
(Increase) decrease in operating assets:
Accounts receivable - related party	(1,136,508)
Prepaid expenses	(3,063,580)	(1,331,780)
Tax incentive receivable	4,628,464
Other current assets	(10,055)	(591,153)
Security deposits	190,839	(245,835)
Increase (decrease) in operating liabilities:
Accounts payable	(704,304)	266,910
Accrued expenses	1,153,994	(2,355,789)
Deferred revenue - related party	(6,683,281)	96,267,249
Net cash (used in) provided by operating activities	(25,263,832)	60,421,867
Cash flows from investing activities:
Purchase of property and equipment	(6,951,980)	(2,206,996)
Net cash used in investing activities	(6,951,980)	(2,206,996)
Cash flows from financing activities:
Payments on lease obligations - financiing leases	(15,881)	(13,365)
Exercise of share options	175,077	1,267
Proceeds from the issuance of ordinary shares		80,000,000
Net cash provided by financing activities	159,196	77,560,949
Net (decrease) increase in cash, cash equivalents and restricted cash	(32,056,616)	135,775,820
Effect of exchange rate changes on cash	(488,963)	417,022
Cash, cash equivalents and restricted cash at beginning of period	227,356,760	68,203,551
Cash, cash equivalents and restricted cash at end of period	194,811,181	204,396,393
Supplemental disclosure of non-cash transactions:
Issuance of shares in connection with asset acquisitions	7,685,001
Issuance of shares in connection with a license agreement		1,966,340
Fixed asset acquisition included in accounts payable and accrued expenses at end of period	161,008	71,473
Lease obligations for right-of-use asset		24,462,830
Supplemental disclosure of cash flow information:
Cash paid for interest	$ 136	991
Ordinary Shares [Member]
Cash flows from financing activities:
Issuance costs in connection with ordinary shares		$ (2,426,953)

Organization and Basis of Prese

Organization and Basis of Presentation	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Organization and Basis of Presentation	MEIRAGTX HOLDINGS PLC AND SUBSIDIARIES NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS 1. Organization and Basis of Presentation: The Company MeiraGTx Holdings plc and subsidiaries (the “Company” or “Meira Holdings”), an exempted company incorporated under the laws of the Cayman Islands, is a vertically integrated, clinical-stage gene therapy company with six programs in clinical development and a broad pipeline of preclinical and research programs. The Company has core capabilities in viral vector design and optimization and gene therapy manufacturing, as well as a potentially transformative gene regulation technology. Led by an experienced management team, the Company has taken a portfolio approach by licensing, acquiring and developing technologies that give depth across both product candidates and indications. The Company’s initial focus is on three distinct areas of unmet medical need: inherited retinal diseases, neurodegenerative diseases and severe forms of xerostomia. Though initially focusing on the eye, central nervous system and salivary gland, the Company intends to expand its focus in the future to develop additional gene therapy treatments for patients suffering from a range of serious diseases. The Company also owns and operates a current good manufacturing practices, or cGMP, multi-product, multi-viral vector manufacturing facility in London, United Kingdom, which includes fill and finish capabilities and can supply the Company’s clinical and potential commercial material. Additionally, on August 4, 2020, the Company entered into agreements to purchase its second cGMP viral vector manufacturing facility and its first cGMP plasmid production facility in Shannon, Ireland to expand its manufacturing and supply chain capabilities. See Note 11, Subsequent Event Basis of Presentation The accompanying condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Interim Financial Statements The accompanying condensed consolidated financial statements have been prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all the information and footnotes required by GAAP for complete consolidated financial statements. In the opinion of management, the condensed consolidated financial statements include all adjustments (consisting of normal recurring accruals) necessary in order to make the condensed consolidated financial statements not misleading. Operating results for the six-month period ended June 30, 2020 are not necessarily indicative of the final results that may be expected for the year ending December 31, 2020. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the notes thereto for the year ended December 31, 2019 included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2019 (the “Form 10-K”). Liquidity The Company has not yet achieved profitable operations. There is no assurance that profitable operations, if ever achieved, could be sustained on a continuing basis. In addition, development activities, clinical and preclinical testing, and commercialization of the Company’s product candidates will require significant additional financing. The Company’s accumulated deficit at June 30, 2020 totaled $244,135,083, and management expects to incur substantial losses in future periods. The success of the Company is subject to certain risks and uncertainties, including, among others: uncertainty of product development; competition in the Company’s field of use; uncertainty of capital availability; uncertainty in the Company’s ability to enter into agreements with collaborative partners; dependence on third parties; and dependence on key personnel. For the six-months ended June 30, 2020, the Company used $25,263,832 in cash flows from operations and there are no assurances that the Company will generate positive cash flows in the future. Additionally, there are no assurances that the Company will be successful in obtaining an adequate level of financing for the development and commercialization of its product candidates. As of June 30, 2020, the Company had cash and cash equivalents in the amount of $194,811,181, which consisted of depository accounts. On January 30, 2019, the Company entered into a collaboration, option and license agreement with Janssen Pharmaceuticals, Inc. (“Janssen”), one of the Janssen Pharmaceuticals Companies of Johnson & Johnson (the “Collaboration Agreement”), for the research, development and commercialization of gene therapies for the treatment of inherited retinal diseases (“IRD”). Under the terms of the Collaboration Agreement, the Company received an upfront payment of $100,000,000. The Company also receives funding for certain research, manufacturing, clinical development and commercialization costs, potential additional milestone payments upon the achievement of such milestones and royalties on future net sales of products. The Company estimates that its cash and cash equivalents on-hand at June 30, 2020 will be sufficient to cover its expenses for at least the next twelve months from the date of issuance of these condensed consolidated financial statements. Risks and Uncertainties The Company operates in an industry that is subject to intense competition, government regulation and rapid technological change. The Company’s operations are subject to significant risk and uncertainties including financial, operational, technological, regulatory and other risks, including the potential risk of business failure. There are also many uncertainties regarding the pandemic caused by the novel coronavirus, or COVID-19, and the Company is closely monitoring the impact of the pandemic on all aspects of its business, including how the pandemic will impact its financial condition, liquidity, operations, clinical studies, employees, vendors, and industry. While the pandemic did not materially affect the Company's financial results and business operations in the six-month period ended June 30, 2020, the Company is unable to predict the impact that COVID-19 will have on its financial position and operating results in future periods due to numerous uncertainties. The Company will continue to assess the evolving impact of the COVID-19 pandemic and will make adjustments to its operations as necessary. The Company’s capital resources and operations to date have been funded primarily with the proceeds from the Collaboration Agreement and private and public equity offerings. In the future, the Company may seek to raise additional capital through equity offerings, debt financings, marketing and distribution arrangements and other collaborations, strategic alliances and licensing arrangements or other sources to enable it to complete the development and potential commercialization of its product candidates. The COVID-19 outbreak and mitigation measures also have had, and may continue to have, an adverse impact on global economic conditions, which could have an adverse effect on the Company’s ability to raise capital when needed.

Summary of Significant Accounti

Summary of Significant Accounting Policies and Recent Accounting Pronouncements	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies and Recent Accounting Pronouncements	2. Summary of Significant Accounting Policies and Recent Accounting Pronouncements: Certain of the Company’s significant accounting policies are described below. All of the Company’s significant accounting policies are disclosed in the notes to the audited consolidated financial statements as of and for the year ended December 31, 2019 included in the Company’s Form 10-K. Since the date of such financial statements, the Company has adopted the new accounting pronouncements which are disclosed further in this note. Consolidation The accompanying condensed consolidated financial statements include the accounts of Meira Holdings and its wholly owned subsidiaries: MeiraGTx Limited, a limited company incorporated under the laws of England and Wales; MeiraGTx, LLC, a Delaware corporation (“Meira LLC”); MeiraGTx UK II Limited, a limited company incorporated under the laws of England and Wales (“Meira UK II”); MeiraGTx Netherlands, B.V., a private company with limited liability incorporated under the laws of the Netherlands (“Meira Netherlands”); BRI-Alzan, Inc., a Delaware corporation (“BRI-Alzan”); MeiraGTx Bio, Inc., a Delaware corporation (“Meira Bio”); MeiraGTx B.V., a private company with limited liability incorporated under the laws of the Netherlands (“Meira B.V.”); MeiraGTx Ireland DAC, a designated activity company incorporated under the laws of Ireland (“Meira Ireland”); MeiraGTx Neurosciences, Inc., a Delaware corporation (“Meira Neuro”); and MeiraGTx UK Limited, a limited company incorporated under the laws of England and Wales (“Meira UK”). All intercompany balances and transactions between the consolidated companies have been eliminated in consolidation. Use of Estimates Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these condensed consolidated financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. This process may result in actual results differing materially from those estimated amounts used in the preparation of the financial statements if these results differ from historical experience, or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made. In preparing these condensed consolidated financial statements, management used significant estimates in the following areas, among others: collaboration revenue, the accounting for research and development costs, share-based compensation, leases, asset retirement obligations and tax incentive receivable. Additionally, the Company has made estimates of the impact of the COVID-19 pandemic within the condensed consolidated financial statements and there may be changes to those estimates in future periods. Actual results may differ from these estimates. Foreign Currency Contracts ​ The Company uses foreign currency forward contracts to protect against changes in anticipated foreign currency cash flows resulting from changes in foreign currency exchange rates, primarily associated with non-functional currency denominated expenses. These instruments are recognized on the balance sheet at their estimated fair value. The Company does not designate its foreign currency forward contracts as part of a hedging transaction. Changes in the fair value are recorded each period within the Company’s condensed consolidated statement of operations and comprehensive loss as a component of net loss. There were no foreign currency forward contracts outstanding as of June 30, 2020. Fair Value Measurements Fair value is defined as the price that would be received upon sale of an asset or paid upon transfer of a liability in an orderly transaction between market participants at the measurement date and in the principal or most advantageous market for that asset or liability. The fair value should be calculated based on assumptions that market participants would use in pricing the asset or liability, not on assumptions specific to the entity. In addition, the fair value of liabilities should include consideration of non-performance risk including the Company’s credit risk. The Company follows ASC Topic 820, Fair Value Measurements and Disclosures ● Level 1: Observable inputs such as quoted prices in active markets for identical assets the reporting entity has the ability to access as of the measurement date; ● Level 2: Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly; and ● Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. The table below represents the values of the Company’s financial assets and liabilities that are required to be measured at fair value on a recurring basis: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement Using: ​ ​ ​ Significant Significant Other Significant ​ ​ June 30, ​ Observable Inputs ​ Observable Inputs ​ Unobservable Description ​ 2020 ​ (Level 1) ​ (Level 2) ​ (Level 3) Asset retirement obligations ​ $ 1,682,515 ​ $ — ​ $ — ​ $ 1,682,515 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement Using: ​ ​ ​ Significant Significant Other Significant ​ ​ December 31, ​ Observable Inputs ​ Observable Inputs ​ Unobservable Description ​ 2019 ​ (Level 1) ​ (Level 2) ​ (Level 3) Restricted cash ​ $ 123,376 ​ $ 123,376 ​ $ — ​ $ — Asset retirement obligations ​ $ 1,654,755 ​ $ — ​ $ — ​ $ 1,654,755 ​ Leases The Company accounts for leases in accordance with ASC 842. The Company determines if an arrangement is a lease at contract inception. A lease exists when a contract conveys the right to control the use of identified property, plant, or equipment for a period of time in exchange for consideration. The definition of a lease embodies two conditions: (1) there is an identified asset in the contract that is land or a depreciable asset (i.e., property, plant, and equipment), and (2) the Company has the right to control the use of the identified asset. The Company accounts for the lease and non-lease components as a single lease component. From time to time the Company enters into direct financing lease arrangements that include a lessee obligation to purchase the leased asset at the end of the lease term, a bargain purchase option, or provides for minimum lease payments with a present value of 90% or more of the fair value of the leased asset at the date of lease inception. Operating leases where the Company is the lessee are included in right-of-use (“ROU”) assets and lease obligations are included on the Company’s consolidated balance sheets. The lease obligations are initially and subsequently measured at the present value of the unpaid lease payments at the lease commencement date and subsequent reporting periods. Finance leases where the Company is the lessee are included in ROU assets and lease obligations on the Company’s consolidated balance sheets. The lease obligations are initially measured in the same manner as for operating leases and are subsequently measured at amortized cost using the effective interest method. Key estimates and judgments include how the Company determined (1) the discount rate used to discount the unpaid lease payments to present value, (2) lease term and (3) lease payments. ASC 842 requires a lessee to discount its unpaid lease payments using the interest rate implicit in the lease or, if that rate cannot be readily determined, its incremental borrowing rate. As most of the Company’s leases where it is the lessee do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The Company’s incremental borrowing rate for a lease is the rate of interest it would have to pay on a collateralized basis to borrow an amount equal to the lease payments under similar terms. The Company uses the implicit rate when readily determinable. The lease term for all of the Company’s leases includes the non-cancellable period of the lease plus any additional periods covered by either a lessee option to extend (or not to terminate) the lease that is reasonably certain to be exercised, or an option to extend (or not to terminate) the lease controlled by the lessor. The ROU asset is initially measured at cost, which comprises the initial amount of the lease liability adjusted for lease payments made at or before the lease commencement date less any lease incentives received. For operating leases, the ROU asset is subsequently measured throughout the lease term at the carrying amount of the lease liability, minus any accrued lease payments, less the unamortized balance of lease incentives received. Lease expense for lease payments is recognized on a straight-line basis over the lease term. For finance leases, the ROU asset is subsequently amortized using the straight-line method from the lease commencement date to the earlier of the end of its useful life or the end of the lease term unless the lease transfers ownership of the underlying asset, or the Company is reasonably certain to exercise an option to purchase the underlying asset. In those cases, the ROU asset is amortized over the useful life of the underlying asset. Amortization of the ROU asset is recognized and presented separately from interest expense on the lease liability. The Company has elected not to recognize ROU assets and lease liabilities for all short-term leases that have a lease term of 12 months or less at lease commencement. Lease payments associated with short-term leases are recognized as an expense on a straight-line basis over the lease term. Asset Retirement Obligations Accounting for asset retirement obligations requires legal obligations associated with the retirement of long-lived assets to be recognized at fair value when incurred and capitalized as part of the related long-lived asset. In the absence of quoted market prices, the Company estimates the fair value of its asset retirement obligations using Level 3 present value techniques, in which estimates of future cash flows associated with retirement activities are discounted using a credit-adjusted risk-free rate. Asset retirement obligations currently reported as other liabilities on the condensed consolidated balance sheet were measured during a period of historically low interest rates. The impact on measurements of new asset retirement obligations using different rates in the future may be significant. The Company uses estimates to determine the asset retirement obligations at the end of the lease term and discounts such asset retirement obligations using an estimated discount rate. Interest on the discounted asset retirement obligation is amortized over the term of the lease using the effective interest method and is recorded as interest expense in the condensed consolidated statements of operations and comprehensive loss. ​ ​ The change in asset retirement obligations is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Six Months Ended June 30, ​ ​ 2020 ​ 2019 Balance at beginning of period $ 1,654,755 $ 128,119 Amortization of interest ​ 66,385 ​ 5,277 Effects of exchange rate ​ (38,625) ​ (550) Balance at end of period ​ $ 1,682,515 ​ $ 132,846 ​ ​ Collaboration Arrangements The Company evaluates its collaborative arrangements pursuant to ASC 808, Collaborative Arrangements Revenue from Contracts with Customers ASC 808 does not address recognition or measurement matters related to collaborative arrangements. Payments between participants pursuant to a collaborative arrangement that are within the scope of other authoritative accounting literature on income statement classification are accounted for using the relevant provisions of that literature. If the payments are not within the scope of other authoritative accounting literature, the income statement classification for the payments is based on an analogy to authoritative accounting literature or if there is no appropriate analogy, a reasonable, rational and consistently applied accounting policy election. Payments received from a collaboration partner to which this policy applies may include upfront payments in respect of a license of intellectual property, development and commercialization-based milestones, and royalties. Refer to the discussion in Note 8 for further information related to the accounting for the Janssen Collaboration Agreement. Revenue Recognition Arrangements with collaborators may include licenses to intellectual property, research and development services, manufacturing services for clinical and commercial supply, and participation on joint steering committees. The Company evaluates the promised goods or services to determine which promises, or group of promises, represent performance obligations. In contemplation of whether a promised good or service meets the criteria required of a performance obligation, the Company considers the stage of development of the underlying intellectual property, the capabilities and expertise of the customer relative to the underlying intellectual property, and whether the promised goods or services are integral to or dependent on other promises in the contract. When accounting for an arrangement that contains multiple performance obligations, the Company must develop judgmental assumptions, which may include market conditions, reimbursement rates for personnel costs, development timelines and probabilities of regulatory success to determine the stand-alone selling price for each performance obligation identified in the contract. When the Company concludes that a contract should be accounted for as a combined performance obligation and recognized over time, the Company must then determine the period over which revenue should be recognized and the method by which to measure revenue. The Company generally recognizes revenue using a cost-based input method. The Collaboration Agreement with Janssen is accounted for under ASC 808, however, as ASC 808 does not address recognition or measurement matters such as determining the appropriate unit of accounting or when the recognition criteria are met, the Company accounts for the consideration received from Janssen in accordance with ASC 606. In accordance with ASC 606, the Company recognizes revenue when its customer or collaborator obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of ASC 606, it performs the following five steps: i. identify the contract(s) with a customer; ii. identify the performance obligations in the contract; iii. determine the transaction price; iv. allocate the transaction price to the performance obligations within the contract; and v. recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it determines that it is probable it will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be by analogy within the scope of ASC 606, the Company assesses the goods or services promised within the contract to determine whether each promised good or service is a performance obligation. The promised goods or services in the Company’s arrangements typically consist of a license to the Company’s intellectual property and research, development and manufacturing services. The Company may provide options to additional items in such arrangements, which are accounted for as separate contracts when the customer elects to exercise such options, unless the option provides a material right to the customer. Performance obligations are promises in a contract to transfer a distinct good or service to the customer that (i) the customer can benefit from on its own or together with other readily available resources, and (ii) is separately identifiable from other promises in the contract. Goods or services that are not individually distinct performance obligations are combined with other promised goods or services until such combined group of promises meet the requirements of a performance obligation. The Company determines transaction price based on the amount of consideration the Company expects to receive for transferring the promised goods or services in the contract. Consideration may be fixed, variable, or a combination of both. At contract inception for arrangements that include variable consideration, the Company estimates the probability and extent of consideration it expects to receive under the contract utilizing either the most likely amount method or expected amount method, whichever best estimates the amount expected to be received. The Company then considers any constraints on the variable consideration and includes in the transaction price variable consideration to the extent it is deemed probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. The Company then allocates the transaction price to each performance obligation based on the relative standalone selling price and recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) control is transferred to the customer and the performance obligation is satisfied. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company records amounts as accounts receivable when the right to consideration is deemed unconditional. When consideration is received, or such consideration is unconditionally due, from a customer prior to transferring goods or services to the customer under the terms of a contract, a contract liability is recorded as deferred revenue. Amounts received prior to satisfying the revenue recognition criteria are recognized as deferred revenue in the Company’s condensed consolidated balance sheet. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue – related party, current. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue – related party. The Company’s collaboration revenue arrangements include the following: Up-front License Fees: If a license is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from nonrefundable, up-front fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone Payments: At the inception of an agreement that includes research and development milestone payments, the Company evaluates each milestone to determine when and how much of the milestone to include in the transaction price. The Company first estimates the amount of the milestone payment that the Company could receive using either the expected value or the most likely amount approach. The Company primarily uses the most likely amount approach as that approach is generally most predictive for milestone payments with a binary outcome. Then, the Company considers whether any portion of that estimated amount is subject to the variable consideration constraint (that is, whether it is probable that a significant reversal of cumulative revenue would not occur upon resolution of the uncertainty.) The Company updates the estimate of variable consideration included in the transaction price at each reporting date which includes updating the assessment of the likely amount of consideration and the application of the constraint to reflect current facts and circumstances. Royalties: For arrangements that include sales-based royalties, including milestone payments based on a level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company will recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any revenue related to sales-based royalties or milestone payments based on the level of sales. Research and Development Services: The Company is incurring research and development costs, with Janssen responsible for up to 100% of the costs, depending on the type of research and development services being performed. The Company records costs associated with the development activities as research and development expenses in the condensed consolidated statements of operations and comprehensive loss consistent with ASC 730, Research and Development Research and Development Research and development costs are charged to expense as incurred. These costs include, but are not limited to, employee-related expenses, including salaries, benefits and travel of the Company’s research and development personnel; expenses incurred under agreements with contract research organizations and investigative sites that conduct clinical and preclinical studies and for the drug product for the clinical studies and preclinical activities; facilities; supplies; rent, insurance, certain legal fees, share-based compensation, depreciation and other costs associated with clinical and preclinical activities and regulatory operations. Research funding under collaboration agreements and refundable research and development credits / tax credits are recorded as an offset to these costs. Costs for certain development activities, such as Company funded outside research programs, are recognized based on an evaluation of the progress to completion of specific tasks with respect to their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the condensed consolidated financial statements as prepaid expenses or accrued expenses, as the case may be. Net Loss per Ordinary Share Basic net loss per ordinary share is computed by dividing net loss by the weighted average number of shares of the Company’s ordinary shares assumed to be outstanding during the period of computation. Diluted net loss per ordinary share is computed similar to basic net loss per share except that the denominator is increased to include the number of additional ordinary shares that would have been outstanding if the potential ordinary shares had been issued at the beginning of the year and if the additional ordinary shares were dilutive (treasury stock method) or the two-class method, whichever is more dilutive. For all periods presented, basic and diluted net loss per ordinary share are the same, as any additional ordinary share equivalents would be anti-dilutive. The following securities are considered to be ordinary share equivalents, but were not included in the computation of diluted net loss per ordinary share because to do so would have been anti-dilutive: ​ ​ ​ ​ ​ ​ ​ June 30, June 30, ​ 2020 2019 Restricted share units ​ 545,000 ​ — Share options 4,976,621 3,547,821 Restricted ordinary shares subject to forfeiture ​ — ​ 435,450 ​ 5,521,621 3,983,271 ​ Segment Information Management has concluded it has a single reporting segment for purposes of reporting financial condition and results of operations. The Company’s license revenue, research funding and deferred revenue from its Collaboration Agreement are generated in the United Kingdom. The following table summarizes non-current assets by geographical area: ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, December 31, ​ ​ 2020 ​ 2019 United States ​ $ 14,726,222 ​ $ 14,354,792 United Kingdom ​ 39,406,645 ​ 39,476,700 Netherlands ​ 1,269,742 ​ 1,076,286 ​ ​ $ 55,402,609 ​ $ 54,907,778 ​ Accounting Pronouncements Recently Adopted In August 2018, the FASB issued ASU 2018-13, Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurements interim periods within those years. The adoption of the provisions of ASU 2018-13 did not have a material impact on the current financial statements. In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 Collaborative Arrangements and , Revenue from Contracts with Customers Recent Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

Asset Acquisition

Asset Acquisition	6 Months Ended
	Jun. 30, 2020
Business Combinations [Abstract]
Asset Acquisition	3. Asset Acquisition On April 9, 2020 (the “Closing Date”), the Company acquired Emrys Bio Inc. (“Emrys”), a pre-clinical biopharmaceutical company developing brain-derived neurotrophic factor gene therapy for treatment of genetic obesity disorders, as well as the development of gene therapy product candidates for other central nervous system diseases. The Company acquired Emrys pursuant to an Agreement and Plan of Merger (the “Emrys Merger Agreement”), dated as of April 9, 2020, by and among the Company, Emrys, and EB Acquisition, Inc., a wholly-owned subsidiary of the Company (“Merger Sub”), the Emrys stockholders and the Emrys stockholder representative, pursuant to which Merger Sub was merged with and into Emrys, with Emrys being the surviving corporation (the “Merger”). As a result of the Merger, Emrys became a wholly-owned subsidiary of the Company and was renamed MeiraGTx Bio, Inc. As part of the entry into the Emrys Merger Agreement, the parties to the Agreement and Plan of Merger (the “Vector Merger Agreement”), dated October 5, 2018, entered into an Amendment and Waiver to the Vector Merger Agreement by and among the Company, VN Acquisition, Inc., VN Acquisition 2, Inc., the former Vector Neurosciences Inc. (“Vector”) stockholders and the Vector stockholder representative, to terminate and waive all milestone payments payable under the Vector Merger Agreement that were otherwise required if specified regulatory milestones were met, In connection with the acquisition of Emrys and the termination and waiver of the milestone and royalty payments otherwise required under the Vector Merger Agreement, the consideration to Emrys selling stockholders consisted of an aggregate of 580,000 of the Company’s ordinary shares of which (i) 232,000 ordinary shares were issued on the Closing Date, (ii) 290,000 restricted ordinary shares were issued on the Closing Date, with 50% of such restricted ordinary shares scheduled to vest on each of the first and second (ii) and (iii) are subject to certain indemnification claims under the Emrys Merger Agreement. Total consideration of $7,685,001 was based on the closing price of the Company’s ordinary shares of $13.25 per share on the Closing Date.

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2020
Payables and Accruals [Abstract]
Accrued Expenses	4. Accrued Expenses Accrued expenses for the periods presented are comprised of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, December 31, ​ ​ 2020 ​ 2019 Clinical trial costs ​ $ 13,277,818 ​ $ 7,788,077 Compensation and benefits ​ ​ 1,028,831 ​ ​ 6,850,335 Fixed assets ​ 869,986 ​ 1,108,362 Manufacturing costs ​ 841,866 ​ — Consulting ​ 734,447 ​ 1,247,989 Professional fees ​ 692,211 ​ 486,743 Rent ​ 523,300 ​ 283,876 Research and development ​ 317,864 ​ — Other ​ 205,537 ​ 318,375 ​ ​ $ 18,491,860 ​ $ 18,083,757 ​

Share-Based Compensation

Share-Based Compensation	6 Months Ended
	Jun. 30, 2020
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	5. Share-Based Compensation Equity Incentive Plans The Company’s 2018 Incentive Award Plan and 2016 Equity Incentive Plan (collectively, the “Plans”) were adopted by the Company’s board of directors and shareholders. Under the Plans, the Company has granted share options and restricted share units (“RSUs”) to selected officers, employees and non-employee consultants. The Company’s board of directors or a committee thereof administers the Plans. Upon the adoption of the 2018 Incentive Award Plan, the Company ceased issuing awards under the 2016 Equity Incentive Plan. Options ​ A summary of the Company’s share option activity related to employees, non-employee members of the board of directors and non-employee consultants as of and for the year-ended December 31, 2019 and the six-month period ended June 30, 2020 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ Weighted- ​ Average ​ ​ ​ ​ ​ ​ Average ​ ​ Remaining ​ ​ ​ ​ Number of ​ Exercise ​ ​ Contractual ​ ​ ​ ​ Options ​ Price ​ ​ Life (years) ​ Outstanding at December 31, 2019 ​ 3,645,360 ​ ​ 9.31 ​ 8.45 years Granted ​ 1,438,500 ​ 18.52 ​ ​ ​ Exercised ​ (26,010) ​ 6.73 ​ ​ ​ Expired ​ ​ — ​ ​ — ​ ​ ​ ​ Forfeited ​ (81,229) ​ 16.96 ​ ​ ​ Outstanding at June 30, 2020 ​ 4,976,621 ​ $ 11.93 ​ ​ 8.24 years Options exercisable at June 30, 2020 ​ 1,990,714 ​ $ 8.89 ​ 7.44 years Aggregate intrinsic value of options outstanding as of June 30, 2020 ​ $ 14,624,869 ​ ​ ​ Aggregate intrinsic value of options exercisable as of June 30, 2020 ​ $ 9,092,153 ​ ​ ​ ​ Options granted under the Plans have a maximum contractual term of ten years. Options granted generally vest 25% on the first anniversary of the date of grant and the balance ratably over the next 36 months. Options granted to directors when they join the board generally vest in 36 The total fair value of options vested during the three-month periods ended June 30, 2020 and 2019 was $3,833,603 and $2,483,808, respectively. The total fair value of options vested during the six-month periods ended June 30, 2020 and 2019 was $5,484,528 The weighted-average grant date fair value of options granted during the six-month periods ended June 30, 2020 and 2019 was $13.85 and $12.70, respectively. The grant date fair values of the share options granted were estimated using the Black-Scholes option valuation model with the following ranges of assumptions: ​ ​ ​ ​ ​ ​ ​ 2020 2019 Risk-free interest rate 0.32 - 2.56% 1.76 - 2.55% Expected volatility 90% 90% Expected dividend yield 0% 0% Expected life (in years) 5.5 6.1 5.5 6.1 ​ As of June 30, 2020, the total compensation expense relating to unvested options granted that had not yet been recognized was $29,117,903, which is expected to be realized over a period of 4.0 ​ Restricted Share Units On January 8, 2020 and March 6, 2020, the Company granted 505,000 and 40,000 RSUs to certain members of senior management and a consultant, respectively. The RSUs were valued at $20.30 and $16.45 per share, respectively, and the related share-based compensation expense, which is recognized ratably over the requisite service period, is included in general and administrative and research and development expenses in the condensed consolidated statements of operations and comprehensive loss. These RSUs vest 50% on the second anniversary of the date of grant and 25% on each For the three-months ended June 30, 2020, total share-based compensation expense recorded in connection with the RSUs was $681,846, of which $640,722 was recorded as general and administrative expense and $41,124 was recorded as research and development expense. For the six-months ended June 30, 2020, total share-based compensation expense recorded in connection with the RSUs was $1,280,141, of which $1,228,051 was recorded as general and administrative expense and $52,090 was recorded as research and development expense. As of June 30, 2020, the total compensation expense relating to unvested RSUs granted that had not yet been recognized was $9,629,359, which is expected to be realized over a period of 3.7 Restricted Ordinary Shares On June 7, 2018, 1,306,348 restricted ordinary shares, which represented 5% of the fully-diluted outstanding shares of the Company as of such date, were issued to certain members of senior management in accordance with their employment agreements. One-third Total compensation expense in connection with the issuance of those restricted ordinary shares, in the amount of $2,969,162 and $4,112,927, of which $1,273,690 and $1,632,930 was share-based, was recorded as general and administrative expense during the three-month periods ended June 30, 2020 and 2019, respectively. Total compensation expense in connection with the issuance of those restricted ordinary shares, in the amount of $6,545,688 and $7,885,577, of which $2,906,620 and $3,265,860 was share-based, was recorded as general and administrative expense during the six-month periods ended June 30, 2020 and 2019, respectively. A summary of the restricted ordinary shares is as follows: ​ ​ ​ ​ ​ ​ ​ ​ Ordinary Shares $ Value Non-vested at December 31, 2019 217,726 ​ $ 3,265,890 Vested during 2020 (217,726) ​ (3,265,890) Non-vested at June 30, 2020 — ​ $ — ​ During the three-month and six-month periods ended June 30, 2020 and 2019 the Company recognized total share-based compensation expense in the accompanying condensed consolidated statements of operations and comprehensive loss as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three-month periods ended June 30, ​ 2020 2019 Research and development ​ $ 1,464,231 ​ $ 862,971 General and administrative ​ 3,591,838 ​ 3,523,152 Total share-based compensation ​ $ 5,056,069 ​ $ 4,386,123 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six-month periods ended June 30, ​ 2020 2019 Research and development ​ $ 2,882,022 ​ $ 1,697,285 General and administrative ​ 7,856,928 ​ 5,623,829 Total share-based compensation ​ $ 10,738,950 ​ $ 7,321,114 ​ The Company does not expect to realize any tax benefits from its share option activity or the recognition of share-based compensation expense because the Company currently has net operating losses and has a full valuation allowance against its deferred tax assets. Accordingly, no amounts related to excess tax benefits have been reported in cash flows from operations or cash flows from financing activities for the six-month periods ended June 30, 2020 and 2019.

Ordinary Shares

Ordinary Shares	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Ordinary Shares	6. Ordinary Shares Private Placement On February 27, 2019, the Company issued 5,797,102 ordinary shares in a private placement for gross proceeds of $80 million, excluding offering costs of approximately $2.4 million. Johnson & Johnson Innovation – JJDC, Inc. (“JJDC”), the investment arm of Johnson and Johnson and owner of Janssen, purchased 2,898,550 of the ordinary shares issued on the same terms and conditions as the other investors in the offering. In connection with the offering, the Company also entered into a registration rights agreement whereby, promptly following the date on which the Company becomes eligible to use a registration statement on Form S-3, but in no event later than July 31, 2019, the Company shall prepare and file a registration statement covering the resale of all of the Registrable Securities, as defined in the agreement. The Company filed the Form S-3 on July 2, 2019 and the Form S-3 was declared effective on July 16, 2019. License Agreement As discussed in Note 8, on March 21, 2019, the Company issued 158,832 ordinary shares in connection with a license agreement. In accordance with the license agreement, the cost basis of the shares was based on the closing share price on January 31, 2019.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	7. Income Taxes The Company did not record a provision for income taxes for the three-month and six-month periods ended June 30, 2020 and 2019, as the Company has generated losses for all periods. The Company periodically evaluates the realizability of its deferred tax assets based on all available evidence, both positive and negative. The realization of deferred tax assets is dependent on the Company’s ability to generate sufficient future taxable income during periods prior to the expiration of tax attributes to fully utilize these assets. The Company weighed both positive and negative evidence and determined that there is a continued need for a full valuation allowance on its deferred tax assets (after consideration of the reversal of the deferred tax liabilities for the ROU assets and fixed assets) in the United States, United Kingdom and Netherlands as of June 30, 2020. Should the Company determine that it would be able to realize its remaining deferred tax assets in the foreseeable future, an adjustment to its remaining deferred tax assets would cause a material increase to income in the period such determination is made. The intraperiod tax allocation guidance required that the Company allocate income taxes between continuing operations and other categories of earnings. When the Company had a year-to-date pre-tax loss from continuing operations and year-to-date pre-tax income in other comprehensive income, applicable GAAP (ASC 740-20-45-7) required that the Company allocate the income tax provision to other categories of earnings (including other comprehensive income), and then record a related tax benefit in operations. For the three and six-month periods ended June 30, 2019, the Company recognized net income from other comprehensive income while sustaining losses from operations. Because of the required allocation, the Company recorded on the condensed consolidated statements of operations and comprehensive loss an income tax benefit of $91,390 for the three and six-month periods ended June 30, 2019, respectively, within “benefit for income taxes” and income tax expense of $91,390 within “other comprehensive income” for the three-month and six-month periods ended June 30, 2019, respectively. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740) – Simplifying the Accounting for Income Taxes ​ New Tax Legislation

Related-Party Transactions

Related-Party Transactions	6 Months Ended
	Jun. 30, 2020
Related Party Transactions [Abstract]
Related-Party Transactions	8. Related-Party Transactions Collaboration and License Agreements Janssen Pharmaceuticals, Inc. On January 30, 2019, the Company entered into a Collaboration Agreement with Janssen for the research, development and commercialization of gene therapies for the treatment of IRDs. Under the agreement, Janssen paid the Company a non-refundable upfront fee of $100.0 million. Janssen and the Company will collaborate to develop the Company’s current clinical programs in retinitis pigmentosa and two genetic forms of achromatopsia, and Janssen has the exclusive right to commercialize these three product candidates (“Clinical IRD Product Candidates”) globally. Pursuant to the Collaboration Agreement, the Company and Janssen also agreed on a research collaboration to develop a pipeline of preclinical inherited retinal disease gene therapy candidates (“Research IRD Product Candidates”). The parties will select and prioritize the Research IRD Product Candidates and Janssen has the right to opt-in for a fee for each of the specified targets (each an “Option Target”) to obtain certain development, manufacturing and commercialization rights for the Research IRD Product Candidates. Unless terminated earlier under certain termination clauses, the Collaboration Agreement will continue in effect, on a product-by-product and country-by-country basis, until such time as the royalty terms expire in such country. The Company has determined enforceable rights exist in the Collaboration Agreement as the termination clauses are substantive termination penalties by way of the non-refundable upfront fee and the reversion of any licensed intellectual property granted to Janssen upon the termination of the agreement. On February 27, 2019, in connection with a private placement, the Company issued 2,898,550 ordinary shares to JJDC, the investment arm of Johnson and Johnson and owner of Janssen, on the same terms and conditions as the other investors in the offering. After the offering, JJDC became a related party. Clinical IRD Product Candidates Under the Collaboration Agreement, the Company and Janssen will jointly develop Clinical IRD Product Candidates to permit Janssen to commercialize such Clinical IRD Product Candidates under an exclusive license from the Company. In general, the Company will have the primary responsibility to develop each Clinical IRD Product Candidate in accordance with the development plan for each Clinical IRD Product Candidate, including where applicable, conducting any necessary research in order to submit the applicable regulatory filings to regulatory authorities. The Company will manufacture these products in its cGMP manufacturing facility for both clinical and commercial supply. Janssen will pay 100% of the clinical and commercialization costs of the products and the Company is eligible to receive untiered 20% royalties on net sales of products and additional development and commercialization milestones up to $340.0 million. Research IRD Product Candidates Under the Collaboration Agreement, the Company and Janssen will collaborate to develop Research IRD Product Candidates, with Janssen paying for the majority of the research costs. Janssen has the right to exclusively license any product coming out of the collaboration at the time of an investigational new drug application (“IND”) for an additional fee for each Research IRD Product Candidate. Janssen will then pay 100% of the clinical and commercialization costs for these Research IRD Product Candidates and the Company will receive an untiered royalty on net sales in the high teens as well as development milestones for each Research IRD Product Candidate. Revenue Recognition under the Collaboration Agreement The Collaboration Agreement is accounted for under ASC 808, however, ASC 808 does not address recognition or measurement matters. Therefore, the Company will account for the recognition and measurement of consideration under ASC 606. In determining the appropriate amount of revenue to be recognized under ASC 606, the Company performed the following steps: (i) identified the promised goods or services in the contract; (ii) determined whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company evaluated the potential performance obligations in the contract, which included the exclusive license to Clinical IRD Product Candidates, the research, development and manufacturing services (“the services”), and the participation in various joint committees and determined that none of the performance obligations by themselves were distinct. Goods and services that are not distinct are bundled with other goods or services in the contract until a bundle of goods or services that is distinct is created. The services, when combined with the licenses, represent a bundle and should be accounted for as a single performance obligation due to the relevance of the services to the value of the early-stage license and the potential for the intellectual property to be significantly modified during the services period. The Company also evaluated whether or not the right to purchase exclusive option rights for specified Research IRD Product Candidates represents future performance obligations and concluded that these represent a separate buyer decision at market rates, rather than a material right performance obligation. As such, these options have been excluded from the initial allocation of transaction price and the Company will account for these options as separate contracts when and if Janssen elects to exercise the options. Under ASC 606, the Company recognized collaboration revenue using the cost-to-cost input method, which it believes best depicts the transfer of control to the customer. Under the cost-to-cost input method, the extent of progress towards completion is measured based on the ratio of actual costs incurred to the total estimated costs expected upon satisfying the combined performance obligation by the potential product candidate. Under this method, revenue is being recorded as a percentage of the estimated transaction price based on the extent of progress towards completion. Under ASC 606, the estimated transaction price includes variable consideration subject to constraints. The Company does not include variable consideration to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will occur when any uncertainty associated with the variable consideration is resolved. The estimate of the Company’s measure of progress and estimate of variable consideration to be included in the transaction price will be updated at each reporting date as a change in estimate. The amount related to the unsatisfied portion will be recognized as that portion is satisfied over time. Under ASC 606 the Company accounts for (i) the licenses it conveyed with respect to the Clinical IRD Product Candidates and (ii) its obligations to perform services as a single performance obligation under the Collaboration Agreement with Janssen on a product candidate basis. Janssen’s right to purchase exclusive options to obtain certain development, manufacturing and commercialization rights are accounted for separately as they do not represent material rights, based on the criteria of ASC 606. Upon the exercise of any purchased option by Janssen, the contract promises associated with an Option Target would use a separate cost-to-cost model for purposes of revenue recognition under ASC 606. During the six months ended June 30, 2019, the Company received a $100.0 million non-refundable upfront fee from Janssen and allocated this amount plus other variable consideration not subject to constraint to each identified performance obligation using a combination of methods allowable under ASC 606. The Company applies the practical expedient in Topic 606 and does not include disclosures regarding amounts for variable consideration allocated to wholly-unsatisfied performance obligations or wholly-unsatisfied distinct goods that form part of a single performance obligation, if any. This variable consideration includes expected reimbursement of research and development costs. During the six-month periods ended June 30, 2020 and 2019, the Company recognized $6,683,281 and $2,766,636, respectively, of the deferred revenue – related party as license revenue. The Company also recognized $10,574,561 and $2,952,121, respectively, during the three-month periods ended June 30, 2020 and 2019 related to the reimbursement of research and development expenses which was recorded as an offset to research and development expenses. The Company also recognized $24,604,578 and $3,989,663, respectively, during the six-month periods ended June 30, 2020 and 2019 related to the reimbursement of research and development expenses which was recorded as an offset to research and development expenses. As of June 30, 2020, the Company expects to recognize the remaining $73,694,653 in deferred revenue associated with the non-refundable upfront fee over the estimated research and development period using the cost-to-cost input method over an estimated period of approximately 4.75 A summary of the deferred revenue recognition is as follows: ​ ​ ​ ​ Non-refundable upfront fee from Janssen $ 100,000,000 Deferred revenue recognized as license revenue during the year ended December 31, 2019 ​ (13,291,956) Effects of exchange rate ​ (493,953) Deferred revenue at December 31, 2019 ​ ​ 86,214,091 Deferred revenue recognized as license revenue during the six months ended June 30, 2020 ​ ​ (6,683,281) Effects of exchange rate ​ ​ (5,836,157) Deferred revenue at June 30, 2020 ​ $ 73,694,653 ​ Riboswitch Research Collaboration Agreement On October 16, 2018, the Company entered into a riboswitch research collaboration agreement with Janssen to develop regulatable gene therapy treatment using the Company’s proprietary riboswitch technology. As part of the agreement, the Company will use its proprietary riboswitch technology to engineer regulatable gene therapy constructs encoding proprietary gene sequences from Janssen. Upon execution of the agreement, Janssen paid the stage 1 fee in the amount of $658,667 and such payment was recorded as deferred revenue – related party. The stage 1 fee was being amortized over the estimated research term of eight months. During the three-month periods ended June 30, 2020 and 2019, the Company amortized $0 and $192,076, respectively, of the deferred revenue, which was recorded as an offset to research and development expenses. During the six-month periods ended June 30, 2020 and 2019, the Company amortized $0 and $444,399, respectively, of the deferred revenue, which was recorded as an offset to research and development expenses. Research Agreement Effective October 23, 2016, the Company entered into a four Total research and development expenses under this agreement for the three-month periods ended June 30, 2020 and 2019 were approximately $101,000 and $85,000, respectively. Total research and development expenses under this agreement for the six-month periods ended June 30, 2020 and 2019 were approximately $203,000 and $173,000, respectively. There are no future obligations under the agreement as of June 30, 2020. The amount due to UCL under the master services agreement at June 30, 2020 and December 31, 2019 is $101,751 and $166,404, respectively, and is included in accounts payable and accrued expenses on the condensed consolidated balance sheets. License Agreement Effective February 4, 2015, the Company entered into an exclusive worldwide license agreement with UCL Business, PLC (“UCL Business”) to develop up to eight programs using certain ocular gene therapy technology. Under the terms of the agreement, the Company had agreed to pay UCL Business certain sales milestone payments, if achieved, in the aggregate amount of £39.8 million, or approximately $48.1 million using the exchange rate at June 30, 2020, and royalties on net sales, as defined upon commercialization. Additionally, the Company is responsible for all patent prosecution and maintenance costs incurred and has also agreed to pay UCL Business an annual maintenance fee of £50,000 , or approximately $62,000 , until the first commercial sale of a product. The agreement terminates upon the later of (i) the last valid claim in a relevant product, (ii) the expiration of regulatory exclusivity to all licensed products, or (iii) the 10 th anniversary of the first commercial sale of a product. On July 28, 2017, March 15, 2018 and September 7, 2018, the Company entered into additional exclusive worldwide license agreements with UCL Business under the same terms as the February 4, 2015 worldwide license agreement. In January and February, 2019, the Company amended and restated the following agreements: (i) the License Agreement, dated February 4, 2015, as amended, between the Company and UCL Business; (ii) the License Agreement, dated July 28, 2017, as amended, between the Company and UCL Business; and (iii) the License Agreement, dated March 15, 2018, between the Company and UCL Business to establish new stand-alone license agreements for the following inherited retinal disease programs: (a) achromatopsia (“ACHM”) caused by mutations in CNGB3 CNGA3 RPE65 The Company’s obligation to pay UCL Business a share of certain sublicensing revenues, as was provided under the February 4, 2015 agreement, has been removed from each of the stand-alone agreements with respect to the IRD programs listed above. Each of the stand-alone agreements now reflects terms substantially similar to those of the February 4, 2015 agreement. Additionally, under the new stand-alone agreement related to CNGB3 the Company paid UCL Business an upfront payment of £1,500,000, or approximately $1,976,000, and issued 158,832 of the Company’s ordinary shares, which were valued at £1,500,000, or approximately $1,966,000. The Company did not incur any research and development expenses under the agreements during the three-month periods ended June 30, 2020 and 2019. The Company incurred research and development expenses under the agreements in the amount of $185,160 and $4,111,876, inclusive of the amendment payments of approximately $3,942,000, during the six-month periods ended June 30, 2020 and 2019, respectively. Leases ARE Lease Effective July 1, 2016, the Company entered into a non-cancellable operating lease (the “ARE Lease”) for laboratory and related office facilities in New York with ARE-East River Science Park, LLC (“ARE”). The ARE Lease provided for monthly base rent and property management fees, including rent escalations and rent holidays, plus operating expenses during the lease term, which was scheduled to expire on December 31, 2021. The Company recorded monthly rent expense on a straight-line basis from July 1, 2016 through February 29, 2020, the date the ARE Lease was terminated as described below. On January 28, 2020, the Company and ARE mutually agreed to terminate the lease with no further obligation for either party effective as of February 29, 2020. Accordingly, the remaining right of use asset and operating lease liability in the amount of Total rent expense under this operating lease was $0 and $121,888 for the three-month periods ended June 30, 2020 and 2019, respectively. Total rent expense under this operating lease was $81,260 and $243,776 for the six-month periods ended June 30, 2020 and 2019, respectively. In connection with the signing of this lease, the Company entered into a standby letter of credit agreement for $122,866, which served as a security deposit for the premises. The standby letter of credit was released in May 2020. Kadmon Lease The Company leases office space on a month-to-month basis from Kadmon Corporation, LLC (“Kadmon”). During the three-month periods ended June 30, 2020 and 2019, the Company incurred rent charges from Kadmon in the amount of $149,435 and $144,101, respectively, which are included in loss from operations. During the six-month periods ended June 30, 2020 and 2019, the Company incurred rent charges from Kadmon in the amount of $295,190 and $284,894, respectively, which are included in loss from operations. During the three-month periods ended June 30, 2020 and 2019, the Company made cash payments totaling $149,435 and $144,101, respectively, to Kadmon. During the six-month periods ended June 30, 2020 and 2019, the Company made cash payments totaling $295,190 and $284,894, respectively, to Kadmon. There were no amounts due to Kadmon at June 30, 2020 and December 31, 2019.

Leases

Leases	6 Months Ended
	Jun. 30, 2020
Leases [Abstract]
Leases	9. Leases The Company has commitments under operating leases for laboratory, warehouse and office space. The Company also has finance leases for manufacturing space and office equipment. The Company’s leases have initial lease terms ranging from 3 years to 108 years. Certain lease agreements contain provisions for future rent increases. Payments due under the lease contracts include fixed payments. Total rent expense recorded under these leases was $901,042 and $102,152 for the three-month periods ended June 30, 2020 and 2019, respectively. Total rent expense under these leases was $1,660,415 and $189,409 for the six-month periods ended June 30, 2020 and 2019, respectively. As of June 30, 2020, the Company has short term lease commitments amounting to approximately $56,000 on a monthly basis for two leases for office space that are month-to-month leases. The components of lease cost for the three-months and six-months ended June 30, 2020 and 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three-month periods ended June 30, ​ ​ 2020 ​ 2019 Finance lease cost ​ ​ Amortization of right-of-use assets ​ $ 71,875 ​ $ 68,956 Interest on lease liabilities ​ 716 ​ 439 Total finance lease cost ​ 72,591 ​ 69,395 Operating lease cost ​ 901,042 ​ 224,040 Short-term lease cost ​ 178,096 ​ 411,931 Total lease cost ​ $ 1,151,729 ​ $ 705,366 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six-month periods ended June 30, ​ ​ 2020 ​ 2019 Finance lease cost ​ ​ ​ Amortization of right-of-use assets ​ $ 145,509 ​ $ 154,371 Interest on lease liabilities ​ 1,558 ​ 992 Total finance lease cost ​ 147,067 ​ 155,363 Operating lease cost ​ 1,741,675 ​ 433,185 Short-term lease cost ​ 339,905 ​ 612,858 Total lease cost ​ $ 2,228,647 ​ $ 1,201,406 ​ ​ Amounts reported in the condensed consolidated balance sheets for leases where the Company is the lessee as of June 30, 2020 and December 31, 2019 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, December 31, ​ ​ ​ 2020 ​ ​ 2019 ​ Operating leases ​ ​ ​ ​ ​ Right-of-use asset ​ $ 19,426,229 ​ ​ $ 21,857,600 ​ Capitalized lease obligations ​ $ 20,661,082 ​ ​ $ 23,127,813 ​ Finance leases ​ ​ ​ ​ Right-of-use asset ​ $ 6,493,945 ​ ​ $ 7,144,848 ​ Capitalized lease obligations ​ $ 32,084 ​ ​ $ 50,737 ​ Weighted-average remaining lease term ​ ​ ​ ​ Operating leases ​ 7.5 years ​ 7.9 years Finance leases ​ 106.5 years ​ 107.0 years Weighted-average discount rate ​ ​ ​ ​ Operating leases ​ 8.6 % ​ 8.5 % Finance leases ​ 8.0 % ​ 7.3 % ​ Other information related to leases for the three-months and six-months ended June 30, 2020 and 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three-month periods ended June 30, ​ ​ ​ 2020 ​ ​ 2019 ​ Cash paid for amounts included in the measurement of lease liabilities ​ Operating cash flows from finance leases $ 5,584 ​ $ 6,741 ​ Operating cash flows from operating leases $ 804,752 ​ $ 270,538 ​ Financing cash flows from finance leases $ 716 ​ $ 349 ​ ​ ​ ​ ​ ​ ​ ​ Right-of-use assets obtained in exchange for lease liabilities ​ ​ Operating leases $ — ​ $ 13,623,007 ​ Finance leases $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six-month periods ended June 30, ​ ​ ​ 2020 ​ ​ 2019 ​ Cash paid for amounts included in the measurement of lease liabilities ​ Operating cash flows from finance leases $ 13,483 ​ $ 13,366 ​ Operating cash flows from operating leases $ 1,541,757 ​ $ 491,816 ​ Financing cash flows from finance leases $ 1,558 ​ $ 992 ​ ​ ​ ​ ​ ​ ​ ​ Right-of-use assets obtained in exchange for lease liabilities ​ ​ Operating leases $ — ​ $ 16,994,156 ​ Finance leases $ — ​ $ — ​ ​ ​ Future minimum lease payments under non-cancellable leases as of June 30, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases Finance Leases 2020 ​ $ 1,862,654 ​ $ 7,861 2021 ​ 3,774,249 ​ 15,723 2022 ​ 3,840,970 ​ 11,792 2023 ​ 3,909,693 ​ — 2024 ​ ​ 3,730,582 ​ ​ — Thereafter ​ 10,494,636 ​ — Total undiscounted lease payments ​ $ 27,612,784 ​ $ 35,376 Less: Imputed interest ​ (6,951,702) ​ (3,292) Total lease liabilities ​ $ 20,661,082 ​ $ 32,084 ​
Leases	The Company has commitments under operating leases for laboratory, warehouse and office space. The Company also has finance leases for manufacturing space and office equipment. The Company’s leases have initial lease terms ranging from 3 years to 108 years. Certain lease agreements contain provisions for future rent increases. Payments due under the lease contracts include fixed payments. Total rent expense recorded under these leases was $901,042 and $102,152 for the three-month periods ended June 30, 2020 and 2019, respectively. Total rent expense under these leases was $1,660,415 and $189,409 for the six-month periods ended June 30, 2020 and 2019, respectively. As of June 30, 2020, the Company has short term lease commitments amounting to approximately $56,000 on a monthly basis for two leases for office space that are month-to-month leases. The components of lease cost for the three-months and six-months ended June 30, 2020 and 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three-month periods ended June 30, ​ ​ 2020 ​ 2019 Finance lease cost ​ ​ Amortization of right-of-use assets ​ $ 71,875 ​ $ 68,956 Interest on lease liabilities ​ 716 ​ 439 Total finance lease cost ​ 72,591 ​ 69,395 Operating lease cost ​ 901,042 ​ 224,040 Short-term lease cost ​ 178,096 ​ 411,931 Total lease cost ​ $ 1,151,729 ​ $ 705,366 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six-month periods ended June 30, ​ ​ 2020 ​ 2019 Finance lease cost ​ ​ ​ Amortization of right-of-use assets ​ $ 145,509 ​ $ 154,371 Interest on lease liabilities ​ 1,558 ​ 992 Total finance lease cost ​ 147,067 ​ 155,363 Operating lease cost ​ 1,741,675 ​ 433,185 Short-term lease cost ​ 339,905 ​ 612,858 Total lease cost ​ $ 2,228,647 ​ $ 1,201,406 ​ ​ Amounts reported in the condensed consolidated balance sheets for leases where the Company is the lessee as of June 30, 2020 and December 31, 2019 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, December 31, ​ ​ ​ 2020 ​ ​ 2019 ​ Operating leases ​ ​ ​ ​ ​ Right-of-use asset ​ $ 19,426,229 ​ ​ $ 21,857,600 ​ Capitalized lease obligations ​ $ 20,661,082 ​ ​ $ 23,127,813 ​ Finance leases ​ ​ ​ ​ Right-of-use asset ​ $ 6,493,945 ​ ​ $ 7,144,848 ​ Capitalized lease obligations ​ $ 32,084 ​ ​ $ 50,737 ​ Weighted-average remaining lease term ​ ​ ​ ​ Operating leases ​ 7.5 years ​ 7.9 years Finance leases ​ 106.5 years ​ 107.0 years Weighted-average discount rate ​ ​ ​ ​ Operating leases ​ 8.6 % ​ 8.5 % Finance leases ​ 8.0 % ​ 7.3 % ​ Other information related to leases for the three-months and six-months ended June 30, 2020 and 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three-month periods ended June 30, ​ ​ ​ 2020 ​ ​ 2019 ​ Cash paid for amounts included in the measurement of lease liabilities ​ Operating cash flows from finance leases $ 5,584 ​ $ 6,741 ​ Operating cash flows from operating leases $ 804,752 ​ $ 270,538 ​ Financing cash flows from finance leases $ 716 ​ $ 349 ​ ​ ​ ​ ​ ​ ​ ​ Right-of-use assets obtained in exchange for lease liabilities ​ ​ Operating leases $ — ​ $ 13,623,007 ​ Finance leases $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six-month periods ended June 30, ​ ​ ​ 2020 ​ ​ 2019 ​ Cash paid for amounts included in the measurement of lease liabilities ​ Operating cash flows from finance leases $ 13,483 ​ $ 13,366 ​ Operating cash flows from operating leases $ 1,541,757 ​ $ 491,816 ​ Financing cash flows from finance leases $ 1,558 ​ $ 992 ​ ​ ​ ​ ​ ​ ​ ​ Right-of-use assets obtained in exchange for lease liabilities ​ ​ Operating leases $ — ​ $ 16,994,156 ​ Finance leases $ — ​ $ — ​ ​ ​ Future minimum lease payments under non-cancellable leases as of June 30, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases Finance Leases 2020 ​ $ 1,862,654 ​ $ 7,861 2021 ​ 3,774,249 ​ 15,723 2022 ​ 3,840,970 ​ 11,792 2023 ​ 3,909,693 ​ — 2024 ​ ​ 3,730,582 ​ ​ — Thereafter ​ 10,494,636 ​ — Total undiscounted lease payments ​ $ 27,612,784 ​ $ 35,376 Less: Imputed interest ​ (6,951,702) ​ (3,292) Total lease liabilities ​ $ 20,661,082 ​ $ 32,084

Commitments

Commitments	6 Months Ended
	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments	10. Commitments There were no new material commitments entered into during the six months ended June 30, 2020.

Subsequent Event

Subsequent Event	6 Months Ended
	Jun. 30, 2020
Subsequent Events [Abstract]
Subsequent Event	11. Subsequent Event On August 4, 2020, Meira Ireland, a wholly-owned subsidiary of the Company, entered into two agreements (the “Agreements”) with Shannon Commercial Enterprises DAC trading as Shannon Commercial Properties, to purchase two properties in the Shannon Free Zone in Shannon, Ireland for an aggregate purchase price of €18 million, or approximately $21.2 million. Upon signing the Agreements, the Company paid a 20% deposit in an aggregate amount of €3,600,000, or approximately $4.3 million, with the balance due at closing. These properties will serve as the Company’s second cGMP viral vector manufacturing facility and its first cGMP plasmid production facility. The closing for each property is expected to occur on or around the date of completion of the building structure on each site, with the first building scheduled to be completed on August 21, 2020 and the second building scheduled to be completed on November 17, 2020. At the closings, Meira Ireland will enter into a lease for each property providing for a long leasehold interest of approximately 191 years. ​ Each Agreement includes customary terms and conditions, including that Meira Ireland will receive liquidated damages under certain circumstances if a building is not completed by November 17, 2020 and that Meira Ireland may terminate an Agreement and receive a refund of its deposit if a building is not completed by August 17, 2021. The leases also include customary terms and conditions, with a nominal annual lease cost and annual maintenance fees of approximately €31,000, or approximately $37,000, in the aggregate, which amount is subject to change depending on the annual maintenance costs within the Shannon Free Zone development.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Consolidation	Consolidation The accompanying condensed consolidated financial statements include the accounts of Meira Holdings and its wholly owned subsidiaries: MeiraGTx Limited, a limited company incorporated under the laws of England and Wales; MeiraGTx, LLC, a Delaware corporation (“Meira LLC”); MeiraGTx UK II Limited, a limited company incorporated under the laws of England and Wales (“Meira UK II”); MeiraGTx Netherlands, B.V., a private company with limited liability incorporated under the laws of the Netherlands (“Meira Netherlands”); BRI-Alzan, Inc., a Delaware corporation (“BRI-Alzan”); MeiraGTx Bio, Inc., a Delaware corporation (“Meira Bio”); MeiraGTx B.V., a private company with limited liability incorporated under the laws of the Netherlands (“Meira B.V.”); MeiraGTx Ireland DAC, a designated activity company incorporated under the laws of Ireland (“Meira Ireland”); MeiraGTx Neurosciences, Inc., a Delaware corporation (“Meira Neuro”); and MeiraGTx UK Limited, a limited company incorporated under the laws of England and Wales (“Meira UK”). All intercompany balances and transactions between the consolidated companies have been eliminated in consolidation.
Use of Estimates	Use of Estimates Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these condensed consolidated financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. This process may result in actual results differing materially from those estimated amounts used in the preparation of the financial statements if these results differ from historical experience, or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made. In preparing these condensed consolidated financial statements, management used significant estimates in the following areas, among others: collaboration revenue, the accounting for research and development costs, share-based compensation, leases, asset retirement obligations and tax incentive receivable. Additionally, the Company has made estimates of the impact of the COVID-19 pandemic within the condensed consolidated financial statements and there may be changes to those estimates in future periods. Actual results may differ from these estimates.
Foreign Currency Contracts	Foreign Currency Contracts ​ The Company uses foreign currency forward contracts to protect against changes in anticipated foreign currency cash flows resulting from changes in foreign currency exchange rates, primarily associated with non-functional currency denominated expenses. These instruments are recognized on the balance sheet at their estimated fair value. The Company does not designate its foreign currency forward contracts as part of a hedging transaction. Changes in the fair value are recorded each period within the Company’s condensed consolidated statement of operations and comprehensive loss as a component of net loss. There were no foreign currency forward contracts outstanding as of June 30, 2020.
Fair Value Measurements	Fair Value Measurements Fair value is defined as the price that would be received upon sale of an asset or paid upon transfer of a liability in an orderly transaction between market participants at the measurement date and in the principal or most advantageous market for that asset or liability. The fair value should be calculated based on assumptions that market participants would use in pricing the asset or liability, not on assumptions specific to the entity. In addition, the fair value of liabilities should include consideration of non-performance risk including the Company’s credit risk. The Company follows ASC Topic 820, Fair Value Measurements and Disclosures ● Level 1: Observable inputs such as quoted prices in active markets for identical assets the reporting entity has the ability to access as of the measurement date; ● Level 2: Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly; and ● Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. The table below represents the values of the Company’s financial assets and liabilities that are required to be measured at fair value on a recurring basis: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement Using: ​ ​ ​ Significant Significant Other Significant ​ ​ June 30, ​ Observable Inputs ​ Observable Inputs ​ Unobservable Description ​ 2020 ​ (Level 1) ​ (Level 2) ​ (Level 3) Asset retirement obligations ​ $ 1,682,515 ​ $ — ​ $ — ​ $ 1,682,515 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement Using: ​ ​ ​ Significant Significant Other Significant ​ ​ December 31, ​ Observable Inputs ​ Observable Inputs ​ Unobservable Description ​ 2019 ​ (Level 1) ​ (Level 2) ​ (Level 3) Restricted cash ​ $ 123,376 ​ $ 123,376 ​ $ — ​ $ — Asset retirement obligations ​ $ 1,654,755 ​ $ — ​ $ — ​ $ 1,654,755 ​
Leases	Leases The Company accounts for leases in accordance with ASC 842. The Company determines if an arrangement is a lease at contract inception. A lease exists when a contract conveys the right to control the use of identified property, plant, or equipment for a period of time in exchange for consideration. The definition of a lease embodies two conditions: (1) there is an identified asset in the contract that is land or a depreciable asset (i.e., property, plant, and equipment), and (2) the Company has the right to control the use of the identified asset. The Company accounts for the lease and non-lease components as a single lease component. From time to time the Company enters into direct financing lease arrangements that include a lessee obligation to purchase the leased asset at the end of the lease term, a bargain purchase option, or provides for minimum lease payments with a present value of 90% or more of the fair value of the leased asset at the date of lease inception. Operating leases where the Company is the lessee are included in right-of-use (“ROU”) assets and lease obligations are included on the Company’s consolidated balance sheets. The lease obligations are initially and subsequently measured at the present value of the unpaid lease payments at the lease commencement date and subsequent reporting periods. Finance leases where the Company is the lessee are included in ROU assets and lease obligations on the Company’s consolidated balance sheets. The lease obligations are initially measured in the same manner as for operating leases and are subsequently measured at amortized cost using the effective interest method. Key estimates and judgments include how the Company determined (1) the discount rate used to discount the unpaid lease payments to present value, (2) lease term and (3) lease payments. ASC 842 requires a lessee to discount its unpaid lease payments using the interest rate implicit in the lease or, if that rate cannot be readily determined, its incremental borrowing rate. As most of the Company’s leases where it is the lessee do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The Company’s incremental borrowing rate for a lease is the rate of interest it would have to pay on a collateralized basis to borrow an amount equal to the lease payments under similar terms. The Company uses the implicit rate when readily determinable. The lease term for all of the Company’s leases includes the non-cancellable period of the lease plus any additional periods covered by either a lessee option to extend (or not to terminate) the lease that is reasonably certain to be exercised, or an option to extend (or not to terminate) the lease controlled by the lessor. The ROU asset is initially measured at cost, which comprises the initial amount of the lease liability adjusted for lease payments made at or before the lease commencement date less any lease incentives received. For operating leases, the ROU asset is subsequently measured throughout the lease term at the carrying amount of the lease liability, minus any accrued lease payments, less the unamortized balance of lease incentives received. Lease expense for lease payments is recognized on a straight-line basis over the lease term. For finance leases, the ROU asset is subsequently amortized using the straight-line method from the lease commencement date to the earlier of the end of its useful life or the end of the lease term unless the lease transfers ownership of the underlying asset, or the Company is reasonably certain to exercise an option to purchase the underlying asset. In those cases, the ROU asset is amortized over the useful life of the underlying asset. Amortization of the ROU asset is recognized and presented separately from interest expense on the lease liability. The Company has elected not to recognize ROU assets and lease liabilities for all short-term leases that have a lease term of 12 months or less at lease commencement. Lease payments associated with short-term leases are recognized as an expense on a straight-line basis over the lease term.
Asset Retirement Obligations	Asset Retirement Obligations Accounting for asset retirement obligations requires legal obligations associated with the retirement of long-lived assets to be recognized at fair value when incurred and capitalized as part of the related long-lived asset. In the absence of quoted market prices, the Company estimates the fair value of its asset retirement obligations using Level 3 present value techniques, in which estimates of future cash flows associated with retirement activities are discounted using a credit-adjusted risk-free rate. Asset retirement obligations currently reported as other liabilities on the condensed consolidated balance sheet were measured during a period of historically low interest rates. The impact on measurements of new asset retirement obligations using different rates in the future may be significant. The Company uses estimates to determine the asset retirement obligations at the end of the lease term and discounts such asset retirement obligations using an estimated discount rate. Interest on the discounted asset retirement obligation is amortized over the term of the lease using the effective interest method and is recorded as interest expense in the condensed consolidated statements of operations and comprehensive loss. ​ ​ The change in asset retirement obligations is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Six Months Ended June 30, ​ ​ 2020 ​ 2019 Balance at beginning of period $ 1,654,755 $ 128,119 Amortization of interest ​ 66,385 ​ 5,277 Effects of exchange rate ​ (38,625) ​ (550) Balance at end of period ​ $ 1,682,515 ​ $ 132,846 ​
Collaboration Arrangements	Collaboration Arrangements The Company evaluates its collaborative arrangements pursuant to ASC 808, Collaborative Arrangements Revenue from Contracts with Customers ASC 808 does not address recognition or measurement matters related to collaborative arrangements. Payments between participants pursuant to a collaborative arrangement that are within the scope of other authoritative accounting literature on income statement classification are accounted for using the relevant provisions of that literature. If the payments are not within the scope of other authoritative accounting literature, the income statement classification for the payments is based on an analogy to authoritative accounting literature or if there is no appropriate analogy, a reasonable, rational and consistently applied accounting policy election. Payments received from a collaboration partner to which this policy applies may include upfront payments in respect of a license of intellectual property, development and commercialization-based milestones, and royalties. Refer to the discussion in Note 8 for further information related to the accounting for the Janssen Collaboration Agreement.
Revenue Recognition	Revenue Recognition Arrangements with collaborators may include licenses to intellectual property, research and development services, manufacturing services for clinical and commercial supply, and participation on joint steering committees. The Company evaluates the promised goods or services to determine which promises, or group of promises, represent performance obligations. In contemplation of whether a promised good or service meets the criteria required of a performance obligation, the Company considers the stage of development of the underlying intellectual property, the capabilities and expertise of the customer relative to the underlying intellectual property, and whether the promised goods or services are integral to or dependent on other promises in the contract. When accounting for an arrangement that contains multiple performance obligations, the Company must develop judgmental assumptions, which may include market conditions, reimbursement rates for personnel costs, development timelines and probabilities of regulatory success to determine the stand-alone selling price for each performance obligation identified in the contract. When the Company concludes that a contract should be accounted for as a combined performance obligation and recognized over time, the Company must then determine the period over which revenue should be recognized and the method by which to measure revenue. The Company generally recognizes revenue using a cost-based input method. The Collaboration Agreement with Janssen is accounted for under ASC 808, however, as ASC 808 does not address recognition or measurement matters such as determining the appropriate unit of accounting or when the recognition criteria are met, the Company accounts for the consideration received from Janssen in accordance with ASC 606. In accordance with ASC 606, the Company recognizes revenue when its customer or collaborator obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of ASC 606, it performs the following five steps: i. identify the contract(s) with a customer; ii. identify the performance obligations in the contract; iii. determine the transaction price; iv. allocate the transaction price to the performance obligations within the contract; and v. recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it determines that it is probable it will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be by analogy within the scope of ASC 606, the Company assesses the goods or services promised within the contract to determine whether each promised good or service is a performance obligation. The promised goods or services in the Company’s arrangements typically consist of a license to the Company’s intellectual property and research, development and manufacturing services. The Company may provide options to additional items in such arrangements, which are accounted for as separate contracts when the customer elects to exercise such options, unless the option provides a material right to the customer. Performance obligations are promises in a contract to transfer a distinct good or service to the customer that (i) the customer can benefit from on its own or together with other readily available resources, and (ii) is separately identifiable from other promises in the contract. Goods or services that are not individually distinct performance obligations are combined with other promised goods or services until such combined group of promises meet the requirements of a performance obligation. The Company determines transaction price based on the amount of consideration the Company expects to receive for transferring the promised goods or services in the contract. Consideration may be fixed, variable, or a combination of both. At contract inception for arrangements that include variable consideration, the Company estimates the probability and extent of consideration it expects to receive under the contract utilizing either the most likely amount method or expected amount method, whichever best estimates the amount expected to be received. The Company then considers any constraints on the variable consideration and includes in the transaction price variable consideration to the extent it is deemed probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. The Company then allocates the transaction price to each performance obligation based on the relative standalone selling price and recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) control is transferred to the customer and the performance obligation is satisfied. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company records amounts as accounts receivable when the right to consideration is deemed unconditional. When consideration is received, or such consideration is unconditionally due, from a customer prior to transferring goods or services to the customer under the terms of a contract, a contract liability is recorded as deferred revenue. Amounts received prior to satisfying the revenue recognition criteria are recognized as deferred revenue in the Company’s condensed consolidated balance sheet. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue – related party, current. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue – related party. The Company’s collaboration revenue arrangements include the following: Up-front License Fees: If a license is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from nonrefundable, up-front fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone Payments: At the inception of an agreement that includes research and development milestone payments, the Company evaluates each milestone to determine when and how much of the milestone to include in the transaction price. The Company first estimates the amount of the milestone payment that the Company could receive using either the expected value or the most likely amount approach. The Company primarily uses the most likely amount approach as that approach is generally most predictive for milestone payments with a binary outcome. Then, the Company considers whether any portion of that estimated amount is subject to the variable consideration constraint (that is, whether it is probable that a significant reversal of cumulative revenue would not occur upon resolution of the uncertainty.) The Company updates the estimate of variable consideration included in the transaction price at each reporting date which includes updating the assessment of the likely amount of consideration and the application of the constraint to reflect current facts and circumstances. Royalties: For arrangements that include sales-based royalties, including milestone payments based on a level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company will recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any revenue related to sales-based royalties or milestone payments based on the level of sales. Research and Development Services: The Company is incurring research and development costs, with Janssen responsible for up to 100% of the costs, depending on the type of research and development services being performed. The Company records costs associated with the development activities as research and development expenses in the condensed consolidated statements of operations and comprehensive loss consistent with ASC 730, Research and Development
Research and Development	Research and Development Research and development costs are charged to expense as incurred. These costs include, but are not limited to, employee-related expenses, including salaries, benefits and travel of the Company’s research and development personnel; expenses incurred under agreements with contract research organizations and investigative sites that conduct clinical and preclinical studies and for the drug product for the clinical studies and preclinical activities; facilities; supplies; rent, insurance, certain legal fees, share-based compensation, depreciation and other costs associated with clinical and preclinical activities and regulatory operations. Research funding under collaboration agreements and refundable research and development credits / tax credits are recorded as an offset to these costs. Costs for certain development activities, such as Company funded outside research programs, are recognized based on an evaluation of the progress to completion of specific tasks with respect to their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the condensed consolidated financial statements as prepaid expenses or accrued expenses, as the case may be.
Net Loss per Ordinary Share	Net Loss per Ordinary Share Basic net loss per ordinary share is computed by dividing net loss by the weighted average number of shares of the Company’s ordinary shares assumed to be outstanding during the period of computation. Diluted net loss per ordinary share is computed similar to basic net loss per share except that the denominator is increased to include the number of additional ordinary shares that would have been outstanding if the potential ordinary shares had been issued at the beginning of the year and if the additional ordinary shares were dilutive (treasury stock method) or the two-class method, whichever is more dilutive. For all periods presented, basic and diluted net loss per ordinary share are the same, as any additional ordinary share equivalents would be anti-dilutive. The following securities are considered to be ordinary share equivalents, but were not included in the computation of diluted net loss per ordinary share because to do so would have been anti-dilutive: ​ ​ ​ ​ ​ ​ ​ June 30, June 30, ​ 2020 2019 Restricted share units ​ 545,000 ​ — Share options 4,976,621 3,547,821 Restricted ordinary shares subject to forfeiture ​ — ​ 435,450 ​ 5,521,621 3,983,271 ​
Segment Information	Segment Information Management has concluded it has a single reporting segment for purposes of reporting financial condition and results of operations. The Company’s license revenue, research funding and deferred revenue from its Collaboration Agreement are generated in the United Kingdom. The following table summarizes non-current assets by geographical area: ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, December 31, ​ ​ 2020 ​ 2019 United States ​ $ 14,726,222 ​ $ 14,354,792 United Kingdom ​ 39,406,645 ​ 39,476,700 Netherlands ​ 1,269,742 ​ 1,076,286 ​ ​ $ 55,402,609 ​ $ 54,907,778 ​
Accounting Pronouncements Recently Adopted	Accounting Pronouncements Recently Adopted In August 2018, the FASB issued ASU 2018-13, Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurements interim periods within those years. The adoption of the provisions of ASU 2018-13 did not have a material impact on the current financial statements. In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 Collaborative Arrangements and , Revenue from Contracts with Customers
Recent Accounting Pronouncements Not Yet Adopted	Recent Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Schedule of Company's Financial Assets and Liabilities Measured at Fair Value	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement Using: ​ ​ ​ Significant Significant Other Significant ​ ​ June 30, ​ Observable Inputs ​ Observable Inputs ​ Unobservable Description ​ 2020 ​ (Level 1) ​ (Level 2) ​ (Level 3) Asset retirement obligations ​ $ 1,682,515 ​ $ — ​ $ — ​ $ 1,682,515 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement Using: ​ ​ ​ Significant Significant Other Significant ​ ​ December 31, ​ Observable Inputs ​ Observable Inputs ​ Unobservable Description ​ 2019 ​ (Level 1) ​ (Level 2) ​ (Level 3) Restricted cash ​ $ 123,376 ​ $ 123,376 ​ $ — ​ $ — Asset retirement obligations ​ $ 1,654,755 ​ $ — ​ $ — ​ $ 1,654,755
Schedule of Change in Asset Retirement Obligations	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Six Months Ended June 30, ​ ​ 2020 ​ 2019 Balance at beginning of period $ 1,654,755 $ 128,119 Amortization of interest ​ 66,385 ​ 5,277 Effects of exchange rate ​ (38,625) ​ (550) Balance at end of period ​ $ 1,682,515 ​ $ 132,846
Schedule of Anti-dilutive Securities Excluded from Computation of Earnings per Share	​ ​ ​ ​ ​ ​ ​ June 30, June 30, ​ 2020 2019 Restricted share units ​ 545,000 ​ — Share options 4,976,621 3,547,821 Restricted ordinary shares subject to forfeiture ​ — ​ 435,450 ​ 5,521,621 3,983,271
Summary of Non-Current Assets by Geographical Area	​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, December 31, ​ ​ 2020 ​ 2019 United States ​ $ 14,726,222 ​ $ 14,354,792 United Kingdom ​ 39,406,645 ​ 39,476,700 Netherlands ​ 1,269,742 ​ 1,076,286 ​ ​ $ 55,402,609 ​ $ 54,907,778

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2020
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, December 31, ​ ​ 2020 ​ 2019 Clinical trial costs ​ $ 13,277,818 ​ $ 7,788,077 Compensation and benefits ​ ​ 1,028,831 ​ ​ 6,850,335 Fixed assets ​ 869,986 ​ 1,108,362 Manufacturing costs ​ 841,866 ​ — Consulting ​ 734,447 ​ 1,247,989 Professional fees ​ 692,211 ​ 486,743 Rent ​ 523,300 ​ 283,876 Research and development ​ 317,864 ​ — Other ​ 205,537 ​ 318,375 ​ ​ $ 18,491,860 ​ $ 18,083,757

Share-Based Compensation (Table

Share-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2020
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Company's Share Option Activity Related to Employees, Non-Employee Members of the Board of Directors and Non-Employee Consultants	A summary of the Company’s share option activity related to employees, non-employee members of the board of directors and non-employee consultants as of and for the year-ended December 31, 2019 and the six-month period ended June 30, 2020 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ Weighted- ​ Average ​ ​ ​ ​ ​ ​ Average ​ ​ Remaining ​ ​ ​ ​ Number of ​ Exercise ​ ​ Contractual ​ ​ ​ ​ Options ​ Price ​ ​ Life (years) ​ Outstanding at December 31, 2019 ​ 3,645,360 ​ ​ 9.31 ​ 8.45 years Granted ​ 1,438,500 ​ 18.52 ​ ​ ​ Exercised ​ (26,010) ​ 6.73 ​ ​ ​ Expired ​ ​ — ​ ​ — ​ ​ ​ ​ Forfeited ​ (81,229) ​ 16.96 ​ ​ ​ Outstanding at June 30, 2020 ​ 4,976,621 ​ $ 11.93 ​ ​ 8.24 years Options exercisable at June 30, 2020 ​ 1,990,714 ​ $ 8.89 ​ 7.44 years Aggregate intrinsic value of options outstanding as of June 30, 2020 ​ $ 14,624,869 ​ ​ ​ Aggregate intrinsic value of options exercisable as of June 30, 2020 ​ $ 9,092,153 ​ ​ ​
Schedule of Grant Date Fair Values of the Stock Options Granted	​ ​ ​ ​ ​ ​ ​ 2020 2019 Risk-free interest rate 0.32 - 2.56% 1.76 - 2.55% Expected volatility 90% 90% Expected dividend yield 0% 0% Expected life (in years) 5.5 6.1 5.5 6.1
Summary of Restricted Ordinary Shares	​ ​ ​ ​ ​ ​ ​ ​ Ordinary Shares $ Value Non-vested at December 31, 2019 217,726 ​ $ 3,265,890 Vested during 2020 (217,726) ​ (3,265,890) Non-vested at June 30, 2020 — ​ $ —
Schedule of Share-Based Compensation Expense	During the three-month and six-month periods ended June 30, 2020 and 2019 the Company recognized total share-based compensation expense in the accompanying condensed consolidated statements of operations and comprehensive loss as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three-month periods ended June 30, ​ 2020 2019 Research and development ​ $ 1,464,231 ​ $ 862,971 General and administrative ​ 3,591,838 ​ 3,523,152 Total share-based compensation ​ $ 5,056,069 ​ $ 4,386,123 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six-month periods ended June 30, ​ 2020 2019 Research and development ​ $ 2,882,022 ​ $ 1,697,285 General and administrative ​ 7,856,928 ​ 5,623,829 Total share-based compensation ​ $ 10,738,950 ​ $ 7,321,114

Related-Party Transactions (Tab

Related-Party Transactions (Tables)	6 Months Ended
	Jun. 30, 2020
Related Party Transactions [Abstract]
Summary of the Deferred Revenue Recognition	​ ​ ​ ​ Non-refundable upfront fee from Janssen $ 100,000,000 Deferred revenue recognized as license revenue during the year ended December 31, 2019 ​ (13,291,956) Effects of exchange rate ​ (493,953) Deferred revenue at December 31, 2019 ​ ​ 86,214,091 Deferred revenue recognized as license revenue during the six months ended June 30, 2020 ​ ​ (6,683,281) Effects of exchange rate ​ ​ (5,836,157) Deferred revenue at June 30, 2020 ​ $ 73,694,653

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2020
Leases [Abstract]
Schedule of Components of Lease Cost	The components of lease cost for the three-months and six-months ended June 30, 2020 and 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three-month periods ended June 30, ​ ​ 2020 ​ 2019 Finance lease cost ​ ​ Amortization of right-of-use assets ​ $ 71,875 ​ $ 68,956 Interest on lease liabilities ​ 716 ​ 439 Total finance lease cost ​ 72,591 ​ 69,395 Operating lease cost ​ 901,042 ​ 224,040 Short-term lease cost ​ 178,096 ​ 411,931 Total lease cost ​ $ 1,151,729 ​ $ 705,366 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six-month periods ended June 30, ​ ​ 2020 ​ 2019 Finance lease cost ​ ​ ​ Amortization of right-of-use assets ​ $ 145,509 ​ $ 154,371 Interest on lease liabilities ​ 1,558 ​ 992 Total finance lease cost ​ 147,067 ​ 155,363 Operating lease cost ​ 1,741,675 ​ 433,185 Short-term lease cost ​ 339,905 ​ 612,858 Total lease cost ​ $ 2,228,647 ​ $ 1,201,406
Schedule of Condensed Consolidated Balance Sheets for Leases	Amounts reported in the condensed consolidated balance sheets for leases where the Company is the lessee as of June 30, 2020 and December 31, 2019 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, December 31, ​ ​ ​ 2020 ​ ​ 2019 ​ Operating leases ​ ​ ​ ​ ​ Right-of-use asset ​ $ 19,426,229 ​ ​ $ 21,857,600 ​ Capitalized lease obligations ​ $ 20,661,082 ​ ​ $ 23,127,813 ​ Finance leases ​ ​ ​ ​ Right-of-use asset ​ $ 6,493,945 ​ ​ $ 7,144,848 ​ Capitalized lease obligations ​ $ 32,084 ​ ​ $ 50,737 ​ Weighted-average remaining lease term ​ ​ ​ ​ Operating leases ​ 7.5 years ​ 7.9 years Finance leases ​ 106.5 years ​ 107.0 years Weighted-average discount rate ​ ​ ​ ​ Operating leases ​ 8.6 % ​ 8.5 % Finance leases ​ 8.0 % ​ 7.3 %
Schedule of Other Information Related to Leases	Other information related to leases for the three-months and six-months ended June 30, 2020 and 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three-month periods ended June 30, ​ ​ ​ 2020 ​ ​ 2019 ​ Cash paid for amounts included in the measurement of lease liabilities ​ Operating cash flows from finance leases $ 5,584 ​ $ 6,741 ​ Operating cash flows from operating leases $ 804,752 ​ $ 270,538 ​ Financing cash flows from finance leases $ 716 ​ $ 349 ​ ​ ​ ​ ​ ​ ​ ​ Right-of-use assets obtained in exchange for lease liabilities ​ ​ Operating leases $ — ​ $ 13,623,007 ​ Finance leases $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six-month periods ended June 30, ​ ​ ​ 2020 ​ ​ 2019 ​ Cash paid for amounts included in the measurement of lease liabilities ​ Operating cash flows from finance leases $ 13,483 ​ $ 13,366 ​ Operating cash flows from operating leases $ 1,541,757 ​ $ 491,816 ​ Financing cash flows from finance leases $ 1,558 ​ $ 992 ​ ​ ​ ​ ​ ​ ​ ​ Right-of-use assets obtained in exchange for lease liabilities ​ ​ Operating leases $ — ​ $ 16,994,156 ​ Finance leases $ — ​ $ — ​
Schedule of Future Minimum Lease Payments Under Non-Cancellable Leases	Future minimum lease payments under non-cancellable leases as of June 30, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases Finance Leases 2020 ​ $ 1,862,654 ​ $ 7,861 2021 ​ 3,774,249 ​ 15,723 2022 ​ 3,840,970 ​ 11,792 2023 ​ 3,909,693 ​ — 2024 ​ ​ 3,730,582 ​ ​ — Thereafter ​ 10,494,636 ​ — Total undiscounted lease payments ​ $ 27,612,784 ​ $ 35,376 Less: Imputed interest ​ (6,951,702) ​ (3,292) Total lease liabilities ​ $ 20,661,082 ​ $ 32,084

Organization and Basis of Pre_2

Organization and Basis of Presentation - Additional Information (Details) - USD ($)	Jan. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Description Of Business [Line Items]
Accumulated deficit		$ (244,135,083)		$ (203,035,952)
Cash flows from operations		(25,263,832)	$ 60,421,867
Cash and cash equivalents		$ 194,811,181	204,396,393	$ 227,356,760	$ 68,203,551
Minimum [Member]
Schedule Of Description Of Business [Line Items]
Offsetting expense, period		12 months
Janssen Pharmaceuticals Inc [Member] | Collaboration Agreement [Member]
Schedule Of Description Of Business [Line Items]
Non-refundable upfront fee received	$ 100,000,000		$ 100,000,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Foreign Currency Contracts And Company's Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Foreign Exchange Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments and Hedges, Assets	$ 0
Fair Value, Measurements, Recurring [Member] | Restricted Cash [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, net asset (liability)		$ 123,376
Fair Value, Measurements, Recurring [Member] | Asset Retirement Obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, net asset (liability)	1,682,515	1,654,755
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Restricted Cash [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, net asset (liability)		123,376
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Asset Retirement Obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, net asset (liability)	$ 1,682,515	$ 1,654,755

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Change in Asset Retirement Obligations (Details) - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Asset Retirement Obligation [Abstract]
Balance at beginning of period	$ 1,654,755	$ 128,119
Amortization of interest	66,385	5,277
Effects of exchange rate	(38,625)	(550)
Balance at end of period	$ 1,682,515	$ 132,846

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Anti-dilutive Securities Excluded from Computation of Earnings per Share (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earning per share, amount	5,521,621	3,983,271
Restricted share units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earning per share, amount	545,000
Share options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earning per share, amount	4,976,621	3,547,821
Restricted ordinary shares subject to forfeiture [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earning per share, amount		435,450

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Summary of Non-Current Assets by Geographical Area (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Operation By Geographical [Line Items]
Non-current assets	$ 55,402,609	$ 54,907,778
United States
Operation By Geographical [Line Items]
Non-current assets	14,726,222	14,354,792
United Kingdom
Operation By Geographical [Line Items]
Non-current assets	39,406,645	39,476,700
Netherlands
Operation By Geographical [Line Items]
Non-current assets	$ 1,269,742	$ 1,076,286

Asset Acquisition (Details)

Asset Acquisition (Details) - Acquisition Of Emrys [Member]	Apr. 09, 2020USD ($)$ / sharesshares
Acquisition
Total consideration | $	$ 7,685,001
Ordinary Shares [Member]
Acquisition
Number of shares issued	580,000
Share price | $ / shares	$ 13.25
On Closing Date [Member] | Ordinary Shares [Member]
Acquisition
Number of shares issued	232,000
On Closing Date [Member] | Restricted ordinary Shares [Member]
Acquisition
Number of shares issued	290,000
Following Closing Date [Member] | Ordinary Shares [Member]
Acquisition
Number of shares issued	58,000
Term of issue of shares	18 months
First Anniversary Of Closing Date [Member] | Restricted ordinary Shares [Member]
Acquisition
Vesting percentage	50.00%
Second Anniversary Of Closing Date [Member] | Restricted ordinary Shares [Member]
Acquisition
Vesting percentage	50.00%

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Clinical trial costs	$ 13,277,818	$ 7,788,077
Compensation and benefits	1,028,831	6,850,335
Fixed assets	869,986	1,108,362
Manufacturing costs	841,866
Consulting	734,447	1,247,989
Professional fees	692,211	486,743
Rent	523,300	283,876
Research and development	317,864
Other	205,537	318,375
Accrued Expenses	$ 18,491,860	$ 18,083,757

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Details)	Mar. 06, 2020$ / sharesshares	Jan. 08, 2020$ / sharesshares	Jun. 07, 2018item$ / sharesshares	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)$ / sharesshares	Jun. 30, 2019USD ($)$ / shares	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average remaining contractual life of options, outstanding						8 years 2 months 27 days		8 years 5 months 12 days
Fair value of options Vested				$ 3,833,603	$ 2,483,808	$ 5,484,528	$ 3,874,750
Weighted average grant date fair value of options granted | $ / shares						$ 13.85	$ 12.70
Share options granted during the period | shares						1,438,500
Share-based compensation						$ 10,738,950	$ 7,321,114
Total share-based compensation				5,056,069	4,386,123	10,738,950	7,321,114
Excess Tax Benefit from Share-based Compensation, Operating Activities						0	0
Excess Tax Benefit from Share-based Compensation, Financing Activities						$ 0	0
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average remaining contractual life of options, outstanding						10 years
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation				3,591,838	3,523,152	$ 7,856,928	5,623,829
Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation				1,464,231	862,971	$ 2,882,022	1,697,285
Restricted ordinary shares subject to forfeiture [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fully-diluted outstanding shares			5.00%
Restricted share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period expected to realize unrecognized compensation expense						3 years 8 months 12 days
Total compensation expense not yet recognized relating to unvested RSUs				9,629,359		$ 9,629,359
Total share-based compensation				681,846		1,280,141
Restricted share units | General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation				640,722		1,228,051
Restricted share units | Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation				41,124		52,090
Share options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unvested options compensation expense not yet recognized				29,117,903		$ 29,117,903
Period expected to realize unrecognized compensation expense						4 years
Senior Management [Member] | Restricted ordinary shares subject to forfeiture [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			33.33%
Ordinary shares awarded, per share | $ / shares			$ 15
Ordinary shares | shares			1,306,348
Number of quarters for vesting | item			8
Share-based compensation				2,969,162	4,112,927	$ 6,545,688	7,885,577
Senior Management [Member] | Restricted ordinary shares subject to forfeiture [Member] | General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation				$ 1,273,690	$ 1,632,930	$ 2,906,620	$ 3,265,860
Senior Management [Member] | Restricted share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share options granted during the period | shares		505,000
Ordinary shares awarded, per share | $ / shares		$ 20.30
Consultant | Restricted share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share options granted during the period | shares	40,000
Ordinary shares awarded, per share | $ / shares	$ 16.45
Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period						36 months
First Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage						25.00%
Second Anniversary [Member] | Restricted share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage						50.00%
Third Anniversary [Member] | Restricted share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage						25.00%
Fourth Anniversary [Member] | Restricted share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage						25.00%
Over Three Years [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period						36 months

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Company's Share Option Activity (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Number of Options
Number of options, Beginning balance	3,645,360
Number of options, Granted	1,438,500
Number of options, Exercised	(26,010)
Number of options, Forfeited	(81,229)
Number of options, Ending balance	4,976,621	3,645,360
Weighted-Average Exercise Price
Weighted-average exercise price, Beginning balance	$ 9.31
Weighted-average exercise price, Granted	18.52
Weighted-average exercise price, Exercised	6.73
Weighted-average exercise price, Forfeited	16.96
Weighted-average exercise price, Ending balance	$ 11.93	$ 9.31
Options additional disclosures
Number of options, Options exercisable	1,990,714
Weighted-average exercise price, Option exercisable	$ 8.89
Weighted-average remaining contractual life of options, outstanding	8 years 2 months 27 days	8 years 5 months 12 days
Weighted-average remaining contractual life of options, exercisable	7 years 5 months 9 days
Aggregate intrinsic value, options outstanding	$ 14,624,869
Aggregate intrinsic value, options exercisable	$ 9,092,153

Share-Based Compensation - Sche

Share-Based Compensation - Schedule of Grant Date Fair Values of the Share Options Granted Black-Scholes Valuation Model (Details) - Share options	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	0.32%	1.76%
Risk-free interest rate, maximum	2.56%	2.55%
Expected volatility	90.00%	90.00%
Expected dividend yield	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of non-employee options (in years)	5 years 6 months	5 years 6 months
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of non-employee options (in years)	6 years 1 month 6 days	6 years 1 month 6 days

Share-Based Compensation - Su_2

Share-Based Compensation - Summary of Restricted Ordinary Shares (Details) - Senior Management [Member] - Restricted ordinary shares subject to forfeiture [Member]	6 Months Ended
	Jun. 30, 2020USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested Ordinary Shares, Beginning Balance | shares	217,726
Vested, Ordinary Shares | shares	(217,726)
Non-vested Value, Beginning Balance | $	$ 3,265,890
Vested, Value | $	$ (3,265,890)

Share-Based Compensation - Sc_2

Share-Based Compensation - Schedule of Share-Based Compensation Expense (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share Based Compensation Expense [Line Items]
Total share-based compensation	$ 5,056,069	$ 4,386,123	$ 10,738,950	$ 7,321,114
General and Administrative Expense [Member]
Share Based Compensation Expense [Line Items]
Total share-based compensation	3,591,838	3,523,152	7,856,928	5,623,829
Research and Development Expenses [Member]
Share Based Compensation Expense [Line Items]
Total share-based compensation	$ 1,464,231	$ 862,971	$ 2,882,022	$ 1,697,285

Ordinary Shares - Additional In

Ordinary Shares - Additional Information (Details) - USD ($) $ in Millions	Mar. 21, 2019	Feb. 27, 2019	Mar. 31, 2019	Jun. 30, 2020	Dec. 31, 2019
Common stock, shares issued				37,362,416	36,791,906
Ordinary Shares [Member] | License Agreement [Member]
Ordinary shares issued in connection with a license agreement (in shares)	158,832		158,832
Private Placement [Member]
Common stock, shares issued		5,797,102
Proceeds from Issuance of Private Placement		$ 80
Offering costs		$ 2.4
JJDC | Private Placement [Member]
Common stock, shares issued		2,898,550

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Benefit for Income Taxes
Income Taxes Disclosure [Line Items]
Deferred State and Local Income Tax Expense (Benefit)	$ 91,390	$ 91,390
Others Comprehensive Income [Member]
Income Taxes Disclosure [Line Items]
Deferred State and Local Income Tax Expense (Benefit)	$ 91,390	$ 91,390

Related-Party Transactions - Co

Related-Party Transactions - Collaboration and License Agreements (Details) - USD ($)	Jan. 30, 2019	Oct. 16, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Feb. 27, 2019
Related Party Transaction [Line Items]
Shares issued to related party			37,362,416		37,362,416		36,791,906
Private Placement [Member]
Related Party Transaction [Line Items]
Shares issued to related party								5,797,102
Clinical IRD Product Candidate development | Maximum [Member]
Related Party Transaction [Line Items]
Additional development and commercialization milestones	$ 340,000,000
Clinical IRD Product Candidate development | Collaboration Agreement [Member]
Related Party Transaction [Line Items]
Royalties receivable, as a percentage	20.00%
JJDC | Private Placement [Member]
Related Party Transaction [Line Items]
Shares issued to related party								2,898,550
Janssen Pharmaceuticals Inc [Member] | Collaboration Agreement [Member]
Related Party Transaction [Line Items]
Non-refundable upfront fee received	$ 100,000,000					$ 100,000,000
Deferred revenue - related party recognized as license revenue			$ 2,473,705	$ 1,981,676	$ 6,683,281	2,766,636	$ 13,291,956
Reimbursement of research and development expenses			10,574,561	2,952,121	24,604,578	$ 3,989,663
Revenue, remaining performance obligation, amount			73,694,653		73,694,653
Estimated period to recognize remaining deferred revenue						4 years 9 months
Deferred revenue - related party			73,694,653		73,694,653		$ 86,214,091
Janssen Pharmaceuticals Inc [Member] | Research, development and commercialization of gene therapies | Collaboration Agreement [Member]
Related Party Transaction [Line Items]
Non-refundable upfront fee received	$ 100,000,000
Janssen Pharmaceuticals Inc [Member] | Clinical IRD Product Candidate development | Collaboration Agreement [Member]
Related Party Transaction [Line Items]
Percentage of clinical and commercialization costs to be paid by related party	100.00%
Janssen Pharmaceuticals Inc [Member] | Research IRD Candidates development | Collaboration Agreement [Member]
Related Party Transaction [Line Items]
Percentage of clinical and commercialization costs to be paid by related party	100.00%
Janssen Pharmaceuticals Inc [Member] | Riboswitch Research | Collaboration Agreement [Member]
Related Party Transaction [Line Items]
Deferred revenue - related party		$ 658,667
Deferred research funding, amortization period		8 months
Janssen Pharmaceuticals Inc [Member] | Riboswitch Research | Collaboration Agreement [Member] | Research and Development Expenses [Member]
Related Party Transaction [Line Items]
Amortization of deferred revenue - related party			$ 0	$ 192,076	$ 0	$ 444,399

Related-Party Transactions - De

Related-Party Transactions - Deferred Revenue (Details) - Janssen Pharmaceuticals Inc [Member] - Collaboration Agreement [Member] - USD ($)	Jan. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
Non-refundable upfront fee from Janssen	$ 100,000,000				$ 100,000,000
Deferred revenue recognized as license revenue during period		$ (2,473,705)	$ (1,981,676)	$ (6,683,281)	$ (2,766,636)	$ (13,291,956)
Effects of exchange rate				(5,836,157)		(493,953)
Deferred revenue		$ 73,694,653		$ 73,694,653		$ 86,214,091

Related-Party Transactions - Re

Related-Party Transactions - Research Agreement (Details) - USD ($)	Oct. 23, 2016	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
Research and development expenses		$ 16,202,065	$ 9,771,754	$ 24,285,405	$ 22,747,983
UCL Consultants Limited | Master Services Agreement [Member]
Related Party Transaction [Line Items]
Term of agreement	4 years
Agreement termination notice period	30 days
Research and development expenses		101,000	$ 85,000	203,000	$ 173,000
Future obligations under agreement		0		0
UCL Consultants Limited | Master Services Agreement [Member] | Accounts Payable And Accrued Expenses
Related Party Transaction [Line Items]
Amount due under services agreement		$ 101,751		$ 101,751		$ 166,404

Related-Party Transactions - Li

Related-Party Transactions - License Agreement (Details)	Mar. 15, 2018USD ($)shares	Mar. 15, 2018GBP (£)shares	Feb. 04, 2015USD ($)Program	Feb. 04, 2015GBP (£)Program	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)
Related Party Transaction [Line Items]
Research and development expenses					$ 16,202,065	$ 9,771,754		$ 24,285,405	$ 22,747,983
License Agreement [Member]
Related Party Transaction [Line Items]
Issuance of ordinary shares in connection with a license agreement							$ 1,966,340
Research and development expenses					0	$ 0		185,160	4,111,876
License Agreement For Inherited Retinal Disease Programs Related To CNGB3 [Member]
Related Party Transaction [Line Items]
Ordinary shares issued in connection with a license agreement (in shares) | shares	158,832	158,832
Issuance of ordinary shares in connection with a license agreement	$ 1,966,000	£ 1,500,000
Research and development expenses								3,942,000	$ 3,942,000
UCL Business, PLC [Member] | License Agreement [Member]
Related Party Transaction [Line Items]
Number of collaborations programs | Program			8	8
Aggregate sales milestone payments payable				£ 39,800,000	$ 48,100,000			$ 48,100,000
Maintenance fee			$ 62,000	£ 50,000
UCL Business, PLC [Member] | License Agreement For Inherited Retinal Disease Programs Related To CNGB3 [Member]
Related Party Transaction [Line Items]
License arrangement upfront payment	$ 1,976,000	£ 1,500,000

Related-Party Transactions - Le

Related-Party Transactions - Leases (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	May 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Operating lease rent expenses	$ 901,042	$ 102,152	$ 1,660,415	$ 189,409
ARE East River Science Park LLC [Member]
Related Party Transaction [Line Items]
Operating lease, right of use asset write-off						$ 825,888
Operating lease liability write-off	969,477		969,477
Net gain on write-off of operating lease right of use asset and liability			143,589
Operating lease rent expenses	0	121,888	81,260	243,776
Letter of credit outstanding amount					$ 122,866
Kadmon Corporation LLC [Member]
Related Party Transaction [Line Items]
Cash payment	149,435	144,101	295,190	284,894
Amount due under services agreement	0		0			$ 0
Kadmon Corporation LLC [Member] | Loss from operations
Related Party Transaction [Line Items]
Operating lease rent expenses	$ 149,435	$ 144,101	$ 295,190	$ 284,894

Leases - Additional Information

Leases - Additional Information (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)lease	Jun. 30, 2019USD ($)
Lessee, Lease, Description [Line Items]
Operating lease rent expenses	$ 901,042	$ 102,152	$ 1,660,415	$ 189,409
Short term lease commitments monthly amount	$ 56,000		$ 56,000
Number of month-to-month leases | lease			2
Minimum [Member]
Lessee, Lease, Description [Line Items]
Lease term			3 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Lease term			108 years

Leases - Schedule of Components

Leases - Schedule of Components of Lease Cost (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Leases [Abstract]
Amortization of right-of-use assets	$ 71,875	$ 68,956	$ 145,509	$ 154,371
Interest on lease liabilities	716	439	1,558	992
Total finance lease cost	72,591	69,395	147,067	155,363
Operating lease cost	901,042	224,040	1,741,675	433,185
Short-term lease cost	178,096	411,931	339,905	612,858
Total lease cost	$ 1,151,729	$ 705,366	$ 2,228,647	$ 1,201,406

Leases - Schedule of Condensed

Leases - Schedule of Condensed Consolidated Balance Sheets for Leases (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Leases [Abstract]
Right-of-use asset	$ 19,426,229	$ 21,857,600
Capitalized lease obligations	20,661,082	23,127,813
Right-of-use asset	6,493,945	7,144,848
Capitalized lease obligations	$ 32,084	$ 50,737
Operating leases	7 years 6 months	7 years 10 months 24 days
Finance leases	106 years 6 months	107 years
Operating leases	8.60%	8.50%
Finance leases	8.00%	7.30%

Leases - Schedule of Other Info

Leases - Schedule of Other Information Related to Leases (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from finance leases	$ 5,584	$ 6,741	$ 13,483	$ 13,366
Operating lease cash payments	804,752	270,538	1,541,757	491,816
Financing cash flows from finance leases	$ 716	349	$ 1,558	992
Right-of-use assets obtained in exchange for lease liabilities
Operating leases		$ 13,623,007		$ 16,994,156

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Lease Payments Under Non-Cancellable Leases (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Operating Leases
2020	$ 1,862,654
2021	3,774,249
2022	3,840,970
2023	3,909,693
2024	3,730,582
Thereafter	10,494,636
Total undiscounted lease payments	27,612,784
Less: Imputed interest	(6,951,702)
Operating lease liability	20,661,082	$ 23,127,813
Finance Leases
2020	7,861
2021	15,723
2022	11,792
2023	0
Thereafter	0
Total undiscounted lease payments	35,376
Less: Imputed interest	(3,292)
Finance lease liability	$ 32,084	$ 50,737

Subsequent Events - Additional

Subsequent Events - Additional Information (Details)	Aug. 04, 2020USD ($)contractproperty	Aug. 04, 2020EUR (€)	Aug. 04, 2020EUR (€)contractproperty	Jun. 30, 2020USD ($)	Dec. 31, 2019USD ($)
Subsequent Event [Line Items]
Security deposits | $				$ 705,515	$ 951,138
Subsequent Event [Member] | Shannon Free Zone [Member] | Meira Ireland [Member]
Subsequent Event [Line Items]
Number of agreements | contract	2		2
Number of properties | property	2		2
Purchase price consideration	$ 21,200,000	€ 18,000,000
Percentage of deposit paid	20	20
Security deposits	$ 4,300,000		€ 3,600,000
Lessee operating lease, renewal term	191 years		191 years
Annual lease cost and annual maintenance fees	$ 37,000	€ 31,000