MeiraGTx (MGTX) 10-K 11 Mar 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Mar. 08, 2021	Jun. 30, 2020
Document And Entity Information [Abstract]
Entity Registrant Name	MeiraGTx Holdings plc
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Entity File Number	001-38520
Document Period End Date	Dec. 31, 2020
Entity Incorporation, State or Country Code	E9
Entity Tax Identification Number	98-1448305
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
Entity Address, Postal Zip Code	10016
City Area Code	646
Local Phone Number	860-7985
Trading Symbol	MGTX
Entity Well-known Seasoned Issuer	No
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-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		44,264,150
Entity Central Index Key	0001735438
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Amendment Flag	false
ICFR Auditor Attestation Flag	false
Title of 12(b) Security	Ordinary Shares, $0.00003881 par value per share
Entity Public Float			$ 284,754,241

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($)	Dec. 31, 2020	Dec. 31, 2019
CURRENT ASSETS:
Cash and cash equivalents	$ 209,520,355	$ 227,233,384
Accounts receivable - related party	38,479,371	23,337,377
Prepaid expenses	7,081,747	4,464,085
Tax incentive receivable	12,930,062	11,974,437
Other current assets	4,564,441	1,970,585
Total Current Assets	272,575,976	268,979,868
Property and equipment, net	44,041,903	23,858,108
Intangible assets, net	2,119,011
In-process research and development	852,085	777,655
Security deposits	812,344	951,138
Restricted cash		123,376
Other assets	213,722	195,053
Right-of-use assets	43,082,359	29,002,448
TOTAL ASSETS	363,697,400	323,887,646
CURRENT LIABILITIES:
Accounts payable	7,134,204	3,759,339
Accrued expenses	20,860,820	18,083,757
Lease obligations, current	2,582,999	1,674,210
Deferred revenue - related party, current	23,544,583	25,678,515
Other current liabilities	24,453
Total Current Liabilities	54,147,059	49,195,821
Deferred revenue - related party	49,297,194	60,535,576
Lease obligations	19,665,841	21,504,340
Asset retirement obligations	1,814,338	1,654,755
Deferred income tax liability	213,722	195,053
TOTAL LIABILITIES	125,138,154	133,085,545
COMMITMENTS
SHAREHOLDERS' EQUITY:
Ordinary Shares, $0.00003881 par value, 1,288,327,750 authorized, 44,189,150 and 36,791,906 shares issued and outstanding at December 31, 2020 and 2019, respectively	1,716	1,429
Capital in excess of par value	504,482,392	395,630,666
Accumulated other comprehensive loss	(4,896,906)	(1,794,042)
Accumulated deficit	(261,027,956)	(203,035,952)
Total Shareholders' Equity	238,559,246	190,802,101
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 363,697,400	$ 323,887,646

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 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	44,189,150	36,791,906
Common stock, shares outstanding	44,189,150	36,791,906

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
License revenue - related party	$ 15,562,985	$ 13,291,956
Operating expenses:
General and administrative	44,206,921	46,684,297
Research and development	33,910,481	24,875,659
Total operating expenses	78,117,402	71,559,956
Loss from operations	(62,554,417)	(58,268,000)
Other non-operating income (expense):
Foreign currency gain	3,426,152	3,199,774
Interest income	1,275,464	370,603
Interest expense	(139,203)	(48,612)
Net loss	(57,992,004)	(54,746,235)
Other comprehensive loss:
Foreign currency translation	(3,102,864)	(2,087,708)
Total comprehensive loss	(61,094,868)	(56,833,943)
Net loss	$ (57,992,004)	$ (54,746,235)
Basic and diluted net loss per ordinary share	$ (1.54)	$ (1.65)
Weighted-average number of ordinary shares outstanding	37,724,189	33,161,860

CONSOLIDATED STATEMENT OF SHARE

CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY - USD ($)	Ordinary Shares [Member]Public Placement [Member]	Ordinary Shares [Member]Public and Private Placements [Member]	Ordinary Shares [Member]At-the-market offering [Member]	Ordinary Shares [Member]License Agreement [Member]	Ordinary Shares [Member]Vector Neurosciences Acquisition [Member]	Ordinary Shares [Member]Accounts Payable [Member]	Ordinary Shares [Member]	Capital in Excess of Par Value [Member]Public Placement [Member]	Capital in Excess of Par Value [Member]Public and Private Placements [Member]	Capital in Excess of Par Value [Member]At-the-market offering [Member]	Capital in Excess of Par Value [Member]License Agreement [Member]	Capital in Excess of Par Value [Member]Vector Neurosciences Acquisition [Member]	Capital in Excess of Par Value [Member]Accounts Payable [Member]	Capital in Excess of Par Value [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Public Placement [Member]	Public and Private Placements [Member]	At-the-market offering [Member]	License Agreement [Member]	Vector Neurosciences Acquisition [Member]	Accounts Payable [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 payables						$ 1							$ 421,499									$ 421,500
Issuance of ordinary shares in connection with payables, shares						19,807
Exercise of share options							$ 5							557,601									$ 557,606
Exercise of share options, shares							134,533																134,533
Issuance of shares in connection with a license agreement				$ 6							$ 1,966,334									$ 1,966,340
Issuance of shares in connection with a license agreement, shares				158,832
Issuance of shares, net of issuance costs		$ 349							$ 147,701,806									$ 147,702,155
Issuance of shares, net of issuance costs, shares		8,997,102
Share-based compensation							$ 4							15,928,966									$ 15,928,970
Share-based compensation, shares							95,000
Foreign currency translation															(2,087,708)								(2,087,708)
Net loss																(54,746,235)							(54,746,235)
Balance at Dec. 31, 2019							$ 1,429							395,630,666	(1,794,042)	(203,035,952)							190,802,101
Balance, Shares at Dec. 31, 2019							36,791,906
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
Exercise of share options							$ 4							840,754									$ 840,758
Exercise of share options, shares							109,296																109,296
Issuance of shares, net of issuance costs	$ 223		$ 39					$ 69,251,915		$ 12,657,497							$ 69,252,138		$ 12,657,536
Issuance of shares, net of issuance costs, shares	5,750,000		993,448
Share-based compensation														18,416,580									$ 18,416,580
Foreign currency translation															(3,102,864)								(3,102,864)
Net loss																(57,992,004)							(57,992,004)
Balance at Dec. 31, 2020							$ 1,716							$ 504,482,392	$ (4,896,906)	$ (261,027,956)							$ 238,559,246
Balance, Shares at Dec. 31, 2020							44,189,150

CONSOLIDATED STATEMENT OF SHA_2

CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY (Parenthetical) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Stock issuance costs	$ 5,141,012	$ 7,497,852
Public Placement [Member]
Stock issuance costs	4,635,362
Public and Private Placements [Member]
Stock issuance costs		$ 7,497,852
At-the-market offering [Member]
Stock issuance costs	$ 505,650

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (57,992,004)	$ (54,746,235)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Ordinary shares issued in connection with license agreement		1,966,334
Share-based compensation expense	18,416,580	15,928,970
Foreign currency gain	(3,426,152)	(3,199,774)
Depreciation and amortization	4,171,626	2,238,560
Net change in right-of-use assets and liabilities	(387,180)	1,107,805
Loss on disposal of equipment, furniture and fixtures	212,994
Gain on termination of lease liability	(143,590)
Amortization of interest on asset retirement obligations	136,069	20,621
Issuance of shares in connection with asset acquisition	7,685,001
(Increase) decrease in operating assets:
Accounts receivable - related party	(15,401,913)	(23,886,573)
Prepaid expenses	(2,366,269)	(2,259,984)
Tax incentive receivable	(714,672)	(8,401,283)
Other current assets	(2,520,087)	(178,805)
Security deposits	164,183	(796,753)
Increase (decrease) in operating liabilities:
Accounts payable	1,565,763	(8,681)
Accrued expenses	2,171,273	6,518,766
Other current liabilities	23,564
Deferred revenue - related party	(15,562,985)	85,741,929
Net cash (used in) provided by operating activities	(63,967,799)	20,044,897
Cash flows from investing activities:
Purchase of property and equipment	(20,923,556)	(8,980,425)
Payment for right of use asset	(13,968,492)
Purchase of intangible asset	(2,128,385)
Purchase of Arthrogen, net of acquired cash		(389,656)
Net cash used in investing activities	(37,020,433)	(9,370,081)
Cash flows from financing activities:
Payments on lease obligations - financing leases	(23,049)	(24,857)
Exercise of share options	840,758	557,606
Proceeds from the issuance of ordinary shares	87,050,686	155,200,007
Issuance costs in connection with ordinary shares	(5,141,012)	(7,497,852)
Net cash provided by financing activities	82,727,383	148,234,904
Net (decrease) increase in cash, cash equivalents and restricted cash	(18,260,849)	158,909,720
Effect of exchange rate changes on cash	424,444	243,489
Cash, cash equivalents and restricted cash at beginning of year	227,356,760	68,203,551
Cash, cash equivalents and restricted cash at end of year	209,520,355	227,356,760
Supplemental disclosure of non-cash transactions:
Issuance of shares in connection with asset acquisition	7,685,001	421,500
Issuance of shares in connection with a license agreement		1,966,334
Fixed asset acquisition included in accounts payable and accrued expenses at end of period	1,615,127	1,519,454
Issuance of shares in connection with payables	7,685,001	421,500
Right-of-use assets obtained in exchange for lease liabilities	1,889,065	23,324,609
Reclassification of property and equipment to right-of-use asset		7,409,789
Asset retirement obligations in connection with a lease		1,501,290
Supplemental disclosure of cash flow information:
Cash paid for interest	$ 3,134	$ 1,462

Principal Business Activity

Principal Business Activity	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Principal Business Activity	1. Principal Business Activity 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: ocular diseases, including inherited retinal diseases as well as large degenerative 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 (“UK”), 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 acquire its second cGMP viral vector manufacturing facility and its first cGMP plasmid and DNA production facility in Shannon, Ireland to expand its manufacturing and supply chain capabilities. The Company closed on the acquisition of the first building in August 2020 and closed on the acquisition of the second building in January 2021. Acquisitions On April 9, 2020, 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. Emrys was renamed MeiraGTx Bio, Inc. On October 17, 2019, the Company acquired 100% of the outstanding equity of Arthrogen B.V. (“Arthrogen”), biopharmaceutical company developing gene therapy for different indications, using viral mediated gene transfer. Arthrogen specializes in the development of viral gene therapy vectors, in particular adeno-associated virus (AAV-) based therapeutics. Arthrogen was renamed MeiraGTx Netherlands B.V. These acquisitions are part of the Company’s continuing efforts to expand its focus to develop additional gene therapy treatments for patients suffering from a range of serious diseases. (See Note 3 for additional information). Basis of Presentation The accompanying 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”). 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 December 31, 2020 totaled $261,027,956, 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; expanding and protecting the Company’s intellectual property portfolio; dependence on third parties; dependence on key personnel; the COVID-19 pandemic and mitigation measures. For the year ended December 31, 2020, the Company used $63,967,799 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 December 31, 2020, the Company had cash and cash equivalents in the amount of $209,520,355, 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 December 31, 2020 will be sufficient to cover its expenses for at least the next twelve months from the date of issuance of these 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 continues to monitor 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 year ended December 31, 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	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Consolidation The accompanying 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 limited liability company (“Meira LLC”); MeiraGTx UK II Limited, a limited company incorporated under the laws of England and Wales (“Meira UK II”); MeiraGTx Ireland DAC, a designated activity company incorporated under the laws of Ireland (“Meira Ireland”); 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 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 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 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 consolidated financial statements and there may be changes to those estimates in future periods. Actual results may differ from these estimates. Cash and Cash Equivalents The Company considers all highly liquid instruments with an original maturity of 90 days or less at the time of purchase to be cash equivalents. Cash and cash equivalents consist of checking and money market accounts that are readily convertible into cash. Financial Instruments The carrying value of accounts receivable-related party, tax incentive receivable, other current assets, and accounts payable reported in the consolidated balance sheets equal or approximate fair value due to their short maturities. Tax Incentive Receivable Meira UK II is eligible to participate in a UK research and development tax incentive programs under which it is eligible to receive a cash refund from Her Majesty’s Revenue & Customs (“HMRC”) for a percentage of the qualified research and development costs expended by Meira UK II under the small and medium sized enterprises (“SME”) program and the research and development expenditures credit (“RDEC”) program. The SME cash refund is available to companies with less than 500 employees and annual aggregate revenue of less than 100.0 million euro or total aggregate assets less than 86.0 million euro during the reimbursable period. The Company’s estimate of the amount of cash refund it expects to receive related to the SME and RDEC programs is included in tax incentive receivable in the accompanying consolidated balance sheets and such amounts are recorded as a reduction of research and development expense in the statements of operations. During the years ended December 31, 2020 and 2019, the Company recorded reductions to research and development expenses of $5.3 million and $12.0 million, respectively. In addition, the Company incurs Value Added Tax (“VAT”) on services provided by UK, Netherlands and Ireland vendors, which it is entitled to reclaim. The Company’s estimate of the amount of cash refund it expects to receive related to VAT was $4.0 million and $1.8 million as of December 31, 2020 and 2019, respectively, which is included in other current assets in the accompanying consolidated balance sheet. 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. 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 consolidated statement of operations and comprehensive loss as a component of net loss. There were no foreign currency forward contracts outstanding as of December 31, 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 own 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 ​ ​ December 31, ​ Observable Inputs ​ Observable Inputs ​ Unobservable Description ​ 2020 ​ (Level 1) ​ (Level 2) ​ (Level 3) Asset retirement obligations ​ $ 1,814,338 ​ $ — ​ $ — ​ $ 1,814,338 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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 ​ ​ Concentrations of Credit Risk The Company maintains its cash and cash equivalents primarily in depository and money market accounts within two large financial institutions in the United States and one large financial institution in the United Kingdom and Ireland. Cash balances deposited at these major financial banking institutions exceed the insured limit. The Company has not experienced any losses on its bank deposits and believes these deposits do not expose the Company to any significant credit risk. Intangible Assets Intangible assets consist of purchased rights to licensed technology as it relates to the Company’s manufacturing processes and has future alternative in the Company’s operations. The licensed technology is being amortized on a straight-line basis over 7 years, which represents the estimated periods of benefit and the expected pattern of consumption (see Note 6). Property, Plant and Equipment, Net Property, plant and equipment are stated at cost, net of accumulated depreciation. Depreciation is calculated using the straight-line method over the estimated useful lives of the respective assets. Leasehold improvements are depreciated over the lesser of their useful lives or the life of the lease (see Note 5). The estimated useful lives of the asset categories are as follows: ​ ​ ​ ​ Asset Category Useful Lives Computer and office equipment 3 years Laboratory equipment 5 years Manufacturing equipment 7 years Furniture and fixtures 5 years Leasehold improvements lesser of useful life or remaining term of lease ​ Expenditures for leasehold improvements are capitalized, and expenditures for maintenance and repairs are expensed to operations as incurred. ASC Topic 360, Property, Plant and Equipment 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 of . Asset retirement obligations currently reported on the Company’s consolidated balance sheets 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 consolidated statements of operations and comprehensive loss. The change in asset retirement obligations is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended December 31, ​ ​ 2020 ​ 2019 Balance at beginning of period $ 1,654,755 $ 128,119 Additional asset retirement obligations during the period ​ — ​ 1,270,262 Amortization of interest ​ 136,069 ​ 20,621 Change in fair value ​ — ​ 255,999 Effects of exchange rate ​ 23,514 ​ (20,246) Balance at end of period ​ $ 1,814,338 ​ $ 1,654,755 ​ Share-Based Compensation Expense Options The Company grants share options to employees, non-employee members of the Company’s board of directors and non-employee consultants as compensation for services performed. Employee and non-employee members of the board of directors’ awards of share-based compensation are accounted for in accordance with ASC 718, Compensation Stock Compensation, . Using this model, fair value is calculated based on assumptions with respect to (i) the fair value of the Company’s ordinary shares on the grant date; (ii) expected volatility of the Company’s ordinary share price, (iii) the periods of time over which the optionees are expected to hold their options prior to exercise (expected term), (iv) expected dividend yield on the Company’s ordinary shares, and (v) risk-free interest rates. As there had been no public market for the Company’s ordinary shares until the Company’s initial public offering (“IPO”) on June 7, 2018, the estimated fair value of the ordinary shares until that time had been determined by the Company’s board of directors as of the date of each option grant, with input from management, considering the most recently available third-party valuations of ordinary shares and the board of directors’ assessment of additional objective and subjective factors that it believed were relevant and which may have changed from the date of the most recent valuation through the date of the grant. The assumptions underlying these valuations represented management’s best estimate, which involved inherent uncertainties and the application of management’s judgment. As a result, if the Company had used different assumptions or estimates, the fair value of its ordinary shares and its share-based compensation expense could have been materially different. The fair value of ordinary shares after the Company’s IPO was determined based upon the closing share price on the date of grant. Since the Company’s ordinary shares had not been traded on a public exchange prior to the Company’s IPO and have only been traded on a public exchange for a short period of time since the Company’s IPO, the Company believes that it does not have sufficient company-specific information available to determine the expected term based on its historical data. As a result, the expected term of share options granted to the optionees is determined using the average of the vesting period and contractual life of the option, an accepted method for the Company’s option grants under the Securities and Exchange Commission’s (“SEC”) Staff Accounting Bulletin No. 107 and No. 110, Share-Based Payment. Similarly, the Company believes that its future volatility could differ materially during the expected term from the volatility that would be calculated from its historical share prices to date. Consequently, expected volatility is based on an analysis of guideline companies in accordance with ASC 718. The expected dividend yield is zero as the Company has never paid dividends and does not currently anticipate paying any in the foreseeable future. Risk-free interest rates are based on quoted U.S. Treasury rates for securities with maturities approximating the option’s expected term. Restricted Shares In connection with certain employment, service and research agreements, the Company has granted restricted ordinary shares as compensation. The ordinary shares are recognized in the consolidated statements of operations and comprehensive loss based on their grant date fair values. Compensation cost relating to share grants with service-based graded vesting schedules is recognized based on the vesting schedule. Restricted Share Units The Company grants restricted share units (“RSUs”) to employees and non-employee consultants as compensation for services performed. Awards of RSUs are accounted for in accordance with ASC 718, Compensation Stock Compensation, . Collaboration Arrangements The Company evaluates its collaborative arrangements pursuant to ASC 808, Collaborative Arrangements Revenue from Contracts with Customers contractual terms of collaborative arrangements and assesses whether the arrangement involves a joint operating activity pursuant to which the Company is an active participant and is exposed to significant risks and rewards with respect to the arrangement. If the Company is an active participant and is exposed to significant risks and rewards with respect to the arrangement, the Company accounts for the arrangement as a collaboration under ASC 808. To date, the Company has entered into two separate collaboration agreements, both of which are with Janssen, which were determined to be within the scope of ASC 808. 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 11 for further information related to the accounting for the 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 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 consolidated statement 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, other costs associated with clinical and preclinical activities and regulatory operations and acquisition of in process research and development write-offs. 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 consolidated financial statements as prepaid or accrued research and development expenses, as the case may be. Foreign Currencies The Company’s consolidated financial statements are presented in U.S. dollars, the reporting currency of the Company. The financial position and results of operations of Meira UK II, Meira Ireland, Meira Netherlands and Meira B.V. are measured using the foreign subsidiaries’ local currency as the functional currency. These entities’ cash accounts holding U.S. dollars are remeasured based upon the exchange rate at the date of remeasurement with the resulting gain or loss included in the consolidated statements of operations and comprehensive loss. Expenses of such subsidiaries have been translated into U.S. dollars at average exchange rates prevailing during the period. Assets and liabilities have been translated at the rates of exchange on the consolidated balance sheet dates. The resulting translation gain and loss adjustments are recorded directly as a separate component of shareholders' equity and as other comprehensive loss on the consolidated statements of operations and comprehensive

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
Acquisitions	3. Acquisitions Emrys Bio Inc. On April 9, 2020 (the “Closing Date”), the Company acquired 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, and to terminate and waive all royalty payments that were otherwise required to be paid under the Vector Merger Agreement. Several of the selling Emrys stockholders were also stockholders of Vector. 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 The Company determined this transaction represented an asset acquisition as substantially all of the value was in the intellectual property as defined by ASC 805, Business Combinations Arthrogen B.V. On October 17, 2019, the Company acquired 100% of the outstanding equity of Arthrogen, a biopharmaceutical company developing gene therapy for different indications, using viral mediated gene transfer. Arthrogen specializes in the development of viral gene therapy vectors, in particular adeno-associated virus (AAV-) based therapeutics. Arthrogen was renamed MeiraGTx Netherlands B.V. The purchase price consideration was €500,000, or approximately $558,335 , and the Company utilized cash on hand. The Company incurred At the time of acquisition, the net assets acquired were comprised of cash and working capital and were recorded at their respective acquisition date fair values. The excess purchase price over the net tangible assets was ascribed to in-process research and development. The acquisition was not significant to the Company’s consolidated financial statements; therefore, pro forma results of the operations related to this business acquisition for the year ended December 31, 2019 have not been presented. The immaterial results of Arthrogen’s operations since October 17, 2019 have been included in the Company’s consolidated financial statements. ​

Prepaid Expenses

Prepaid Expenses	12 Months Ended
	Dec. 31, 2020
Other Income and Expenses [Abstract]
Prepaid Expenses	4. Prepaid Expenses Prepaid expenses at December 31, 2020 and 2019 consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 Insurance ​ $ 2,901,728 ​ $ 1,758,915 Clinical trial costs ​ 1,624,873 ​ 1,349,657 Manufacturing costs ​ 1,395,141 ​ 259,509 Dues and license fees ​ 515,328 ​ 264,123 Rent ​ 169,038 ​ 183,952 Research and development ​ 164,338 ​ 239,161 Other ​ 311,301 ​ 408,768 ​ ​ $ 7,081,747 ​ $ 4,464,085 ​

Property, Plant and Equipment,

Property, Plant and Equipment, net	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment, net	5. Property, Plant and Equipment, net Property, plant and equipment, net at December 31, 2020 and 2019 consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 Leasehold improvements ​ $ 33,776,712 ​ $ 17,557,316 Manufacturing equipment ​ 7,021,162 ​ 5,647,484 Laboratory equipment ​ 7,350,285 ​ 3,700,632 Computer and office equipment ​ 3,712,884 ​ 1,066,984 Furniture and fixtures ​ 567,730 ​ 441,101 ​ ​ 52,428,773 ​ 28,413,517 Less: Accumulated depreciation ​ (8,386,870) ​ (4,555,409) ​ ​ $ 44,041,903 ​ $ 23,858,108 ​ In connection with certain operating leases, the Company has determined that it has asset retirement obligations in the aggregate amount of $3,736,404 at the end of those leases. The Company discounted the asset retirement obligations using an 8% discount rate and recorded an asset retirement obligation in the aggregate amount of $1,643,794, which is included in leasehold improvements and is being depreciated over the term of the respective leases. Capitalized finance leases in the amount of $95,880 are included in computer and office equipment and were fully depreciated as of December 31, 2019. Depreciation expense was $4,171,626 and $2,238,560 for the years ended December 31, 2020 and 2019 respectively.

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2020
Intangible Assets
Intangible Assets	6. Intangible Assets In November 2020, the Company entered into a non-exclusive, royalty-free technology license agreement that required the Company to pay an upfront payment to the licensor of $2.1 million. The Company accounted for the transaction as an asset acquisition and recorded an intangible asset as it was determined to have alternative future uses in connection with the Company’s manufacturing capabilities. The following table presents the details of the Company’s intangible assets as of December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortization ​ Gross Carrying ​ Accumulated ​ ​ ​ Type Period Amount Amortization Net Licensed Technology ​ 7 years ​ $ 2,144,541 ​ $ 25,530 ​ $ 2,119,011 ​ There were no intangible assets as of December 31, 2019. For the year ended December 31, 2020, amortization expense of was recorded as a component of research and development expenses. There was As of December 31, 2020, the expected amortization expense for the next five years and thereafter is as follows: ​ ​ ​ ​ ​ ​ Amortization ​ ​ Expense 2021 ​ $ 306,360 2022 ​ ​ 306,360 2023 ​ ​ 306,360 2024 ​ ​ 306,360 2025 ​ ​ 306,360 Thereafter ​ ​ 587,211 Total amortization ​ $ 2,119,011 ​

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued Expenses	7. Accrued Expenses Accrued expenses at December 31, 2020 and 2019 were comprised of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 Clinical trial costs ​ $ 11,154,015 ​ $ 7,788,077 Compensation and benefits ​ ​ 3,791,303 ​ ​ 6,850,335 Manufacturing costs ​ 1,885,848 ​ 125,717 Professional fees ​ 1,219,116 ​ 486,743 Consulting ​ 1,046,774 ​ 1,247,989 Fixed assets ​ 948,571 ​ 1,108,362 Rent and facilities costs ​ 662,040 ​ 283,876 Other ​ 153,153 ​ 192,658 ​ ​ $ 20,860,820 ​ $ 18,083,757 ​

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2020
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	8. 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. The number of shares available for issuance under the 2018 Incentive Award Plan are increased on January 1 of each calendar year beginning in 2019 and ending in and including 2028, by an amount equal to the lesser of (A) 4% of the ordinary shares outstanding on the final day of the immediately preceding calendar year and (B) a smaller number of shares determined by the Company's board of directors. Under the 2018 Incentive Award Plan the Company initially reserved up to 3,054,996 shares for issuance, which has been increased to 5,620,882 as of December 31, 2020. As of December 31, 2020, 1,584,468 shares remain available for future issuance. In January 2021, the number of shares available for issuance under the 2018 Incentive Award Plan increased by 1,767,566 shares. Also, in January 2021, the Company's board of directors authorized the issuance of 505,000 restricted share units to certain executives and up to 1,303,700 options to certain executives, employees and consultants, in each case, under the 2018 Incentive Award 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 years ended December 31, 2020 and 2019 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ Weighted- ​ Average ​ ​ ​ ​ ​ ​ Average ​ ​ Remaining ​ ​ ​ ​ Number of ​ Exercise ​ ​ Contractual ​ ​ ​ ​ Options ​ Price ​ ​ Life (years) ​ Outstanding at December 31, 2018 ​ 3,254,365 ​ $ 7.64 ​ ​ Granted ​ 551,000 ​ 17.94 ​ ​ Exercised ​ (134,533) ​ 4.14 ​ ​ Expired ​ — ​ — ​ ​ Forfeited ​ (25,472) ​ 9.37 ​ ​ Outstanding at December 31, 2019 ​ 3,645,360 ​ ​ 9.31 ​ 8.45 years Granted ​ 1,666,500 ​ 15.91 ​ ​ ​ Exercised ​ (109,296) ​ 7.69 ​ ​ ​ Expired ​ ​ — ​ ​ — ​ ​ ​ ​ Forfeited ​ (377,793) ​ 15.71 ​ ​ ​ Outstanding at December 31, 2020 ​ 4,824,771 ​ $ 11.85 ​ ​ 7.67 years Options exercisable at December 31, 2020 ​ 2,249,113 ​ $ 8.88 ​ 6.71 years Aggregate intrinsic value of options outstanding as of December 31, 2020 ​ $ 22,338,580 ​ ​ ​ Aggregate intrinsic value of options exercisable as of December 31, 2020 ​ $ 15,365,249 ​ ​ ​ ​ 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 equal monthly installments following the date of grant, and annual options granted to directors generally vest on the earlier of the first anniversary of the date of grant or the day before the Company’s next annual meeting of shareholders after the date of grant. The total fair value of options vested during the years ended December 31, 2020 and 2019 was $8,156,474 The weighted average grant date fair value of options granted during the years ended December 31, 2020 and 2019 was $11.87 and $13.79, 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 (see Note 2): ​ ​ ​ ​ ​ ​ ​ 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 ​ For the years ended December 31, 2020 and 2019, total share-based compensation expense recorded in connection with the options was $12,866,121 and $8,024,476, of which $6,975,323 and $4,338,180 was recoded as general and administrative expense and $5,890,798 and $3,686,296 was recorded as research and development expense, respectively. As of December 31, 2020, the total compensation expense relating to unvested options granted that had not yet been recognized was $22,808,502, which is expected to be realized over a period of 3.9 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 consolidated statements of operations and comprehensive loss. These RSUs vest 50% on the second anniversary of the date of grant and 25% on each of the third and fourth anniversaries of the date of grant. For the year ended December 31, 2020, total share-based compensation expense recorded in connection with the RSUs was $2,643,833, of which $2,509,495 was recoded as general and administrative expense and $134,338 was recorded as research and development expense. As of December 31, 2020, the total compensation expense relating to unvested RSUs granted that had not yet been recognized was $8,265,667, which is expected to be realized over a period of 3.2 years. 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 $6,545,688 and $15,982,670, of which $2,906,626 and $6,531,744 was share-based and $3,639,062 and $9,450,926 was paid in cash, was recorded as general and administrative expense during the years ended December 31, 2020 and 2019, respectively (See Note 12). A summary of the restricted ordinary shares is as follows: ​ ​ ​ ​ ​ ​ ​ ​ Ordinary Shares $ Value Non-vested at December 31, 2018 653,174 ​ $ 9,797,610 Vested during 2019 (435,448) ​ (6,531,720) Non-vested at December 31, 2019 217,726 ​ $ 3,265,890 Vested during 2020 (217,726) ​ (3,265,890) Non-vested at December 31, 2020 — ​ $ — ​ During the years ended December 31, 2020 and 2019 the Company recognized total share-based compensation expense in the accompanying consolidated statements of operations and comprehensive loss as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 2019 Research and development ​ $ 6,025,136 ​ $ 5,059,046 General and administrative ​ 12,391,444 ​ 10,869,924 Total share-based compensation ​ $ 18,416,580 ​ $ 15,928,970 ​ 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 years ended December 31, 2020 and 2019.

Ordinary Shares

Ordinary Shares	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Ordinary Shares	9. Ordinary Shares 2020 Public Offering In November 2020, the Company issued 5,000,000 ordinary shares in a public offering for gross proceeds of $64.3 million. In December 2020, the underwriter exercised its overallotment provision and the Company issued an additional 750,000 ordinary shares for gross proceeds of $9.6 million. Offering costs in connection with both issuances were approximately $4.6 million. At-the-Market Offering In July 2019, the Company entered into an “at-the-market” sales agreement with Chardan Capital Markets, LLC, or Chardan, pursuant to which the Company may sell from time to time, ordinary shares having an aggregate offering price of up to $75.0 million through Chardan, acting as our agent. During the year ended December 31, 2020, the Company raised gross proceeds of $13.2 million, through the sale of 993,448 ordinary shares pursuant to an “at-the-market” equity offering program. Offering costs were approximately $0.5 million. In November 2020, the Company terminated the at-the-market equity program. Acquisitions In April 2020, the Company issued 522,000 ordinary shares in connection with the acquisition of Emrys Bio Inc. In October 2020, the Company issued 22,500 ordinary shares, which represented the holdback shares from a previous acquisition. 2019 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. Public Offering On August 7, 2019, the Company issued 3,200,000 ordinary shares in a public offering for gross proceeds of $75 million, excluding offering costs of approximately $5.1 million. License Agreement As discussed in Note 11, 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. Other Issuances On July 7, 2019, the Company issued 19,807 shares to a vendor in the amount of $421,500, which was recorded as research and development expense. On October 31, 2019, the Company issued 95,000 shares to a consultant in the amount of $1,372,750, which was recorded as research and development expense.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes For the years ended December 31, 2020 and 2019, the Company recognized a tax benefit of $0. As of December 31, 2020, the Company had U.S. federal and state net operating losses (“NOLs”) and foreign carryforward tax losses which are available to reduce future taxable income of: ​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ State/City United Kingdom ​ $ 142,241,850 ​ $ — United States ​ $ 34,743,371 ​ $ 34,366,051 Netherlands ​ $ 26,111,603 ​ $ — Ireland ​ $ 626,498 ​ $ — ​ The U.S. federal and state NOLs incurred prior to January 1, 2018 in the amount of approximately $6.8 million and $6.7 million, respectively, will begin to expire in 2036. The U.S. NOLs incurred after December 31, 2017 and the UK and Ireland carryforward tax losses will be indefinitely carried forward. The Netherlands carryforward tax losses expire after nine years from the date incurred prior to 2019 and six years for tax losses incurred after 2018. The net operating losses incurred in 2011 and earlier have expired as of December 31, 2020. Also, as of December 31, 2020, the Company had orphan drug and research and development credits in the U.S. in the amount of $5,127,849 which will begin to expire 2036 and research and development credits of $1,204,036 in the UK which can be carried forward indefinitely. The NOLs and carryforward tax losses are subject to review and possible adjustment by the U.S., UK, Netherlands, Ireland and state tax authorities. The U.S. NOLs and UK carryforward tax losses may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders, as defined under Section 382 Internal Revenue Code, as well as CTA 2010 Part 14 under the UK tax rules. This could limit the amount of NOLs and carryforward tax losses that the Company can utilize annually to offset future taxable income or tax liabilities. As of December 31, 2019, the Company had performed such an analysis and determined that there were no limitations in the UK. However, for U.S. purposes, the Company determined that a change of ownership occurred in April 2016 and again in June 2018. The Company is still in the process of determining the annual limitation on losses that occurred prior to June 2018. Netherlands has anti-abuse rules that potentially restrict the use of NOLs in certain change of control situations. Subsequent ownership changes and proposed future changes to the UK, the U.S. or the Netherlands tax rules in respect of the utilization of losses carried forward may further affect the limitation in future years, if any. The Company has completed a study on the completeness of the U.S. orphan drug and research and development credit and the results are included in the income tax footnote in 2020. The Company's pre-tax earnings are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 United Kingdom ​ $ (41,372,993) ​ $ (37,993,537) United States ​ (13,472,052) ​ (16,303,213) Netherlands ​ (2,471,442) ​ (449,485) Ireland ​ ​ (675,517) ​ ​ — ​ ​ $ (57,992,004) ​ $ (54,746,235) ​ The Company is subject to the corporate tax rate in the UK as a limited UK corporation. The following table summarizes a reconciliation of income tax benefit compared with the amounts at the UK statutory income tax rate: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ December 31, 2019 ​ Statutory rate ​ (11,018,481) 19.00 % ​ (10,401,785) 19.00 % Permanent differences - other ​ 1,976,028 (3.41) % ​ (411,651) 0.75 % RTP and other adjustment ​ (2,135,978) ​ 3.68 % ​ 3,068,999 ​ (5.61) % State and local rate, net of federal tax ​ (1,478,111) 2.55 % ​ (2,041,097) 3.73 % U.K. tax credit ​ 574,161 ​ (0.99) % ​ 1,278,072 ​ (2.33) % U.S. tax credit ​ (1,242,356) ​ 2.14 % ​ (1,257,481) ​ 2.30 % Foreign tax rate differential ​ (254,199) ​ 0.44 % ​ (347,301) ​ 0.63 % UK rate change (19% & 17% at expected DTA turn) ​ (2,233,752) 3.85 % ​ 362,092 (0.66) % US state rate change ​ 25,041 ​ (0.04) % ​ — ​ - % Change in valuation allowance ​ 15,787,647 (27.22) % ​ 9,750,152 (17.81) % Actual income tax benefit effective tax rate ​ — 0.00 % ​ — 0.00 % ​ The Expense/(Benefit) for income taxes from continuing operations consists of the following: ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 Current Tax Expense/(Benefit) United Kingdom — — United States — — Netherlands — — Ireland ​ — ​ — Total Current — — Deferred Tax Expense/(Benefit) United Kingdom (9,197,319) (3,036,498) United States (5,851,708) (6,631,936) Netherlands (674,817) (81,718) Ireland ​ (63,803) ​ — Total Deferred (15,787,647) (9,750,152) Change in Valuation Allowance 15,787,647 9,750,152 Total Income Tax Expense/(Benefit) — — ​ ​ Deferred Tax Assets/(Liabilities) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 ​ Deferred Tax Assets: ​ ​ ​ ​ ​ ​ ​ Net operating loss carryforwards ​ $ 43,831,308 ​ $ 31,929,792 ​ Lease liability ​ 6,150,436 ​ ​ 6,012,466 ​ R&D credit ​ 5,819,100 ​ ​ 2,635,188 ​ Share-based compensation ​ ​ 5,392,358 ​ ​ 2,831,696 ​ Other ​ 298,462 ​ ​ 374,507 ​ Deferred tax assets ​ 61,491,664 ​ 43,783,649 ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred Tax Liabilities: ​ ​ ​ ​ ​ ​ ​ Indefinite-lived intangibles ​ (173,431) ​ ​ (173,431) ​ Depreciation ​ ​ (2,252,190) ​ ​ (624,361) ​ Right of use assets ​ (5,928,527) ​ ​ (5,635,987) ​ Less: valuation allowance ​ (53,310,947) ​ (37,523,301) ​ Net deferred tax liability ​ $ (173,431) ​ $ (173,431) ​ ​ ASC 740 requires a valuation allowance to reduce the deferred tax assets reported if, based on the weight of available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. After consideration of all the evidence, both positive and negative, the Company has recorded a full valuation allowance, after consideration of the reversal of the deferred tax liabilities for the ROU assets and fixed assets, against its deferred tax assets at December 31, 2020 and 2019 because the Company's management has determined that is it more likely than not that these assets will not be fully realized. Changes to the UK corporation tax rates have been announced which will impact future accounting periods. In his budget of July 8, 2015, the Chancellor of the Exchequer announced a reduction in the UK corporation tax rate to 19% for the financial year beginning April 1, 2017 and a further reduction to 18% for the financial year beginning April 1, 2020. These changes received Royal Assent on November 18, 2015. The UK Finance Act 2016 provides for a further reduction in the corporation tax rate to 17% for the financial year beginning April 1, 2020. This change was enacted on September 15, 2016. The UK had previously enacted its statutory rate to be reduced to 17% as of April 1, 2020, but amending legislation was enacted in 2020 such that this reduction did not take effect. As the Company does not expect to be able to utilize its carryforward tax losses in the UK prior to its financial year beginning on January 1, 2021, if at all, the deferred tax has been calculated using a tax rate of 19%. As of December 31, 2020 and 2019, the Company recorded unrecognized tax positions of $512,785 and zero respectively. The unrecognized tax positions are netted with deferred tax assets above with full valuation allowance. The changes to unrecognized tax positions for 2020 and 2019 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 Unrecognized tax benefits as of January 1 $ — $ — Gross increases/(decreases) related to current year ​ 138,040 ​ — Gross increases/(decreases) related to prior years ​ 374,745 ​ — Foreign currency translation ​ ​ — ​ ​ — Unrecognized tax positions as of December 31 $ 512,785 $ — ​ The Company will recognize interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2020 and 2019, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company's statements of operations and comprehensive loss. The Company files income tax returns in the United States, UK, Netherlands and Ireland and various state jurisdictions. In the U.S., all years remain subject to examination. The earliest year subject to the statute of limitations in the UK is 2018. The statute of limitations in the Netherlands is generally 5 years after the end of the taxable year. In Ireland, the Irish Revenue may undertake an audit of a company’s tax return within a period of four years from the end of the accounting period in which the return is submitted. MeiraGTx Holdings plc is a UK tax resident with no earnings in its foreign subsidiaries and the Company does not expect any temporary basis difference in its investment in these subsidiaries to reverse in the foreseeable future. Therefore, the Company has not recorded deferred taxes on the outside basis difference in its foreign subsidiaries. It is not probable to compute the amounts, if any. New Tax Legislation Many governments have enacted or are currently contemplating economic stimulus and financial aid measures. Many of these measures include deferring the due dates for tax payments, including both income tax and other taxes. The Coronavirus Aid, Relief, and Economic Security Act ("CARES Act") was enacted on March 27, 2020 in the United States to address the economic impacts of the COVID-19 pandemic. The CARES Act includes corporate income tax, payroll tax, and other provisions. While the Company may receive financial, tax, or other benefits under the bill, this legislation did not impact the Company during the year ended December 31, 2020.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	11. 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 IRD. 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 facilities 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 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 year ended December 31, 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 years ended December 31, 2020 and 2019, the Company recognized $15,562,985 and $13,291,956, respectively, of the deferred revenue – related party as license revenue. The Company also recognized $63,003,824 and $27,296,062 during the years ended December 31, 2020 and 2019, respectively, related to the reimbursement of research and development expenses, of which $57,407,089 and $27,296,062, respectively, was recorded as an offset to research and development expenses and $5,596,735 and $0, respectively, was recorded as an offset to prepaid expenses. As of December 31, 2020, the Company expects to recognize the remaining $72,841,777 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 4.5 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 year ended December 31, 2020 ​ ​ (15,562,985) Effects of exchange rate ​ ​ 2,190,671 Deferred revenue at December 31, 2020 ​ $ 72,841,777 ​ ​ 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 year ended December 31, 2019, the Company amortized the remaining $444,399 of the deferred revenue, which was recorded as an offset to research and development expenses. Additionally, the stage two fee, in the amount of $328,524 was recorded and fully amortized during the year ended December 31, 2019. Research Agreement Effective October 23, 2016, the Company entered into a four-year master services agreement with UCL Consultants Limited, an entity affiliated with University College of London (“UCL”), which is a shareholder of the Company. In October 2020, the master services agreement was extended for an additional four years. Pursuant to a task order to the master services agreement, UCL Consultants Limited had provided pre-clinical research and development under the direction of the Company. The services rendered under the task order were completed in 2020. Total research and development expenses under this agreement for the years ended December 31, 2020 and 2019 was approximately $203,000 and $306,000, respectively. There are currently no future obligations under the agreement as of December 31, 2020. The amount due to UCL under the master services agreement at December 31, 2020 and 2019 is $0 and $166,404, respectively, and is included in accounts payable and accrued expenses on the Company’s 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 $54.4 million using the exchange rate at December 31, 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 $66,000, 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 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; (b) ACHM caused by mutations in CNGA3; (c) X-linked retinitis pigmentosa (“XLRP”); and (d) RPE65-mediated IRD. 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. Effective March 23, 2020, the Company entered into another worldwide license agreement with UCL Business, to develop an additional ocular gene therapy technology. Under the terms of the agreement, the Company agreed to pay UCL Business certain development and sales milestone payments, if achieved, in the aggregate amount of $39.25 million and royalties on net sales, as defined upon commercialization. Additionally, the Company is responsible for all patent prosecution and maintenance costs incurred and also agreed to pay UCL Business an upfront payment of $50,000 and an annual maintenance fee of $25,000 until the first commercial sale of a product. The agreement terminates upon the later of (i) the last valid claim in a relevant product, or (ii) the 10th anniversary of the first commercial sale of a product. The Company incurred research and development expenses under the agreements in the amount of $273,180 and $4,271,275, inclusive of the amendment payments of approximately $0, and $3,942,000 during the years ended December 31, 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”), an entity that is under common control by an entity that is a minority shareholder of the Company and whose executive chairman and founder is a director of the Company. 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 $81,260 and $487,555 for the years ended December 31, 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 years ended December 31, 2020 and 2019, the Company incurred rent charges from Kadmon in the amount of $597,740 and $576,404, respectively, which are included in loss from operations. During the years ended December 31, 2020 and 2019, the Company made cash payments totaling $597,740 and $576,404, respectively, to Kadmon. There were no amounts due to Kadmon at December 31, 2020 and 2019.

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	12. Leases The Company has commitments under operating leases for laboratory, warehouse, clinical trial sites 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 191 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 $3,341,535 and $1,776,631 for the years ended December 31, 2020 and 2019, respectively. As of December 31, 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. On August 4, 2020, Meira Ireland entered into two agreements (the “Agreements”) with Shannon Commercial Enterprises DAC trading as Shannon Commercial Properties, to acquire two properties in the Shannon Free Zone in Shannon, Ireland for an aggregate price of €18 million, or approximately $21.2 million. These properties will serve as the Company’s second cGMP viral vector manufacturing facility and its first cGMP plasmid and DNA production facility. The closing for the first building occurred on August 27, 2020. The total cost of the first building, including taxes and legal fees, was €11,890,000, or approximately $13,801,007 , and has been recorded as a right of use asset in the consolidated balance sheets as of December 31, 2020. There is no corresponding lease liability as the Company paid the full cost on the date of the closing. The closing for the second building occurred in January 2021. At the closings, Meira Ireland entered into a lease for each property providing for a long leasehold interest of approximately 191 years. 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. The components of lease cost for the years ended December 31, 2020 and 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 ​ 2019 Finance lease cost ​ ​ ​ Amortization of right-of-use assets ​ $ 519,379 ​ $ 300,229 Interest on lease liabilities ​ 3,081 ​ 2,409 Total finance lease cost ​ 522,460 ​ 302,638 Operating lease cost ​ 3,422,795 ​ 2,384,048 Short-term lease cost ​ 714,172 ​ 1,282,709 Total lease cost ​ $ 4,659,427 ​ $ 3,969,395 ​ Amounts reported in the consolidated balance sheets for leases where the Company is the lessee as of December 31, 2020 and 2019 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ ​ 2020 ​ ​ 2019 ​ Operating leases ​ ​ ​ ​ ​ Right-of-use asset ​ $ 21,485,924 ​ ​ $ 21,857,600 ​ Capitalized lease obligations ​ $ 22,220,515 ​ ​ $ 23,127,813 ​ Finance leases ​ ​ ​ ​ Right-of-use asset ​ $ 21,596,435 ​ ​ $ 7,144,848 ​ Capitalized lease obligations ​ $ 28,325 ​ ​ $ 50,737 ​ Weighted-average remaining lease term ​ ​ ​ ​ Operating leases ​ 7.0 years ​ 7.9 years Finance leases ​ 175.1 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 as of the years ended December 31, 2020 and 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 ​ ​ 2019 ​ Cash paid for amounts included in the measurement of lease liabilities ​ Operating cash flows from finance leases $ 21,604 ​ $ 28,187 ​ Operating cash flows from operating leases $ 3,790,734 ​ $ 1,246,169 ​ Financing cash flows from finance leases $ 3,081 ​ $ 2,355 ​ ​ ​ ​ ​ ​ ​ ​ Right-of-use assets obtained in exchange for lease liabilities ​ ​ Operating leases $ 1,889,065 ​ $ 23,279,980 ​ Finance leases $ — ​ $ 44,629 ​ ​ Future minimum lease payments under non-cancellable leases as of December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases Finance Leases 2021 ​ $ 4,383,995 ​ $ 17,505 2022 ​ ​ 4,475,018 ​ ​ 13,129 2023 ​ 4,566,431 ​ — 2024 ​ 4,405,144 ​ — 2025 ​ 4,381,270 ​ — Thereafter ​ 7,151,280 ​ — Total undiscounted lease payments ​ $ 29,363,138 ​ $ 30,634 Less: Imputed interest ​ (7,142,623) ​ (2,309) Total lease liabilities ​ $ 22,220,515 ​ $ 28,325 ​

Commitments

Commitments	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments	13. Commitments Service Agreements On April 27, 2015, the Company entered into service agreements with two senior officers of the Company. Under the terms of the agreements, the employees will receive aggregate compensation of £300,000 per year, which was increased to a maximum aggregate amount of £430,000 per year, or approximately $587,000 , for the year ended December 31, 2020. The agreements also provide for contributions to a defined contribution pension plan to be set up by the Company and a discretionary bonus. The agreements may be terminated at any time by either party by giving twelve-months’ notice, or the Company may terminate the officer’s employment effective immediately upon notice, and within 28 days after making payment in lieu of notice consisting of a sum equivalent to the officer’s annual salary for the relevant period. In May 2019 one of the senior officers resigned from the Company and in May 2020, the resignation became effective. For the years ended December 31, 2020 and 2019, the Company recorded , respectively, in research and development costs under these agreements. Future obligations to be paid under the remaining agreement equals Employment Agreements In February 2016, the Company entered into three-year employment agreements with certain senior officers of the Company. Under the terms of the agreements, which automatically renew for successive one-year terms, the employees will receive annual compensation in the aggregate amount of $710,000, which has been increased to a maximum aggregate amount of $1,075,000 per year. The employment agreements also provide for an annual guaranteed cash bonus targeted at 100% of annual compensation. The agreements also provide for discretionary annual performance bonuses targeted to be not less than 50-60% of the employee’s base salary and grants of restricted shares. Bonuses granted to the senior officers, which included their guaranteed and discretionary bonuses, for the years ended December 31, 2020 and 2019, in the aggregate amount of $3,300,000 and $5,403,000, respectively. The employees are also entitled to participate in all incentive and deferred compensation and employee benefit programs available to employees and executive officers of the Company. Future obligations to be paid under these employment agreements equal $2,418,750, as of December 31, 2020. Research Agreements Effective December 5, 2016, the Company entered into a three-year research collaboration agreement with Cornell University. Pursuant to the agreement, Cornell University provides research and development under the direction of the Company. In connection with the agreement, in July 2017, the Company issued , to add a second three-year research collaboration project through September 2019. The Company further amended this agreement, effective October 18, 2018 to include additional costs related to the research. Total research and development expenses under this agreement, as amended, for the years ended December 31, 2020 and 2019 were , respectively. There are no future obligations to be paid under the agreements. License Agreements On September 7, 2018, the Company entered into an exclusive licensing agreement with the National Institutes of Health for worldwide rights to expanded indications for use of AAV-AQP1 for treatment of xerostomia (dry mouth) and xerophthalmia (dry eye) associated with Sjögren's syndrome. This agreement expands the Company’s original exclusive licensing agreement with the NIH for exclusive worldwide rights to AAV-AQP1 that was executed as of November 9, 2017. AAV-AQP1 is currently in Phase 1/2 development for treatment of grade 2 or 3 radiation-induced xerostomia. Total research and development expenses under the agreement for the years ended December 31, 2020 and 2019 were Effective January 1, 2016, the Company acquired all of the outstanding shares of BRI-Alzan from the shareholders of BRI-Alzan. In connection with the Agreement, the Company will pay certain development milestone payments if achieved, in the aggregate amount of

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2020
Postemployment Benefits [Abstract]
Employee Benefit Plans	14. Employee Benefit Plans United States On January 1, 2017, Meira LLC adopted a defined contribution retirement plan that complies with Section 401(k) of the Internal Revenue Code. All Meira LLC employees over the age of 21 are eligible to participate in the plan after three consecutive months of service. Employees are able to defer a portion of their pay into the plan on the first day of the month or after the day all age and service requirements have been met. The plan provides for a Company matching contribution. All eligible employees receive an employer matching contribution equal to the lesser of the amount the employee contributes to the plan or 6% of their salary up to the annual IRS limit. United Kingdom On August 1, 2016, Meira UK II adopted a defined contribution group personal pension plan that complies with HMRC for tax relief. All Meira UK II employees are eligible to participate in the plan upon joining the company and providing the required services. All eligible employees, if they elect to join the pension scheme, receive an employer pension contribution equal to 7.5% to 10.0% of their pensionable earnings. Currently, employees are not required to contribute, but may make optional contributions up to the annual allowance HMRC limits. ​ Netherlands Meira Netherlands operates a defined contribution pension. All of its employees participate in the plan. All eligible employees receive an employer pension contribution and are also required to contribute. Ireland On November 20, 2020, MeiraGTx Ireland adopted a defined contribution pension plan. All MeiraGTx Ireland employees are eligible to participate in the plan upon joining the Company. All eligible employees, if they elect to join the pension scheme, receive an employer pension contribution. The Company’s current contribution, exclusive of an employee match, is During the years ended December 31, 2020 and 2019, employer contributions to all plans were $1,089,657 and $604,294, respectively.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	15. Subsequent Events Visiogene LLC On January 4, 2021, the Company and Visiogene LLC (“Visiogene”) entered into a License and Investment Agreement for an exclusive, worldwide license to certain of Visiogene’s intellectual property relating to ocular gene therapy and acquired Visiogene preferred units for total consideration of $5.0 million in cash, with the majority of such payment being allocated toward the research and development of novel products, and the issuance to Visiogene of 75,000 ordinary shares of the Company.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Consolidation	Consolidation The accompanying 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 limited liability company (“Meira LLC”); MeiraGTx UK II Limited, a limited company incorporated under the laws of England and Wales (“Meira UK II”); MeiraGTx Ireland DAC, a designated activity company incorporated under the laws of Ireland (“Meira Ireland”); 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 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 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 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 consolidated financial statements and there may be changes to those estimates in future periods. Actual results may differ from these estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid instruments with an original maturity of 90 days or less at the time of purchase to be cash equivalents. Cash and cash equivalents consist of checking and money market accounts that are readily convertible into cash.
Financial Instruments	Financial Instruments The carrying value of accounts receivable-related party, tax incentive receivable, other current assets, and accounts payable reported in the consolidated balance sheets equal or approximate fair value due to their short maturities.
Tax Incentive Receivable	Tax Incentive Receivable Meira UK II is eligible to participate in a UK research and development tax incentive programs under which it is eligible to receive a cash refund from Her Majesty’s Revenue & Customs (“HMRC”) for a percentage of the qualified research and development costs expended by Meira UK II under the small and medium sized enterprises (“SME”) program and the research and development expenditures credit (“RDEC”) program. The SME cash refund is available to companies with less than 500 employees and annual aggregate revenue of less than 100.0 million euro or total aggregate assets less than 86.0 million euro during the reimbursable period. The Company’s estimate of the amount of cash refund it expects to receive related to the SME and RDEC programs is included in tax incentive receivable in the accompanying consolidated balance sheets and such amounts are recorded as a reduction of research and development expense in the statements of operations. During the years ended December 31, 2020 and 2019, the Company recorded reductions to research and development expenses of $5.3 million and $12.0 million, respectively. In addition, the Company incurs Value Added Tax (“VAT”) on services provided by UK, Netherlands and Ireland vendors, which it is entitled to reclaim. The Company’s estimate of the amount of cash refund it expects to receive related to VAT was $4.0 million and $1.8 million as of December 31, 2020 and 2019, respectively, which is included in other current assets in the accompanying consolidated balance sheet.
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. 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 consolidated statement of operations and comprehensive loss as a component of net loss. There were no foreign currency forward contracts outstanding as of December 31, 2020. Foreign Currencies The Company’s consolidated financial statements are presented in U.S. dollars, the reporting currency of the Company. The financial position and results of operations of Meira UK II, Meira Ireland, Meira Netherlands and Meira B.V. are measured using the foreign subsidiaries’ local currency as the functional currency. These entities’ cash accounts holding U.S. dollars are remeasured based upon the exchange rate at the date of remeasurement with the resulting gain or loss included in the consolidated statements of operations and comprehensive loss. Expenses of such subsidiaries have been translated into U.S. dollars at average exchange rates prevailing during the period. Assets and liabilities have been translated at the rates of exchange on the consolidated balance sheet dates. The resulting translation gain and loss adjustments are recorded directly as a separate component of shareholders' equity and as other comprehensive loss on the consolidated statements of operations and comprehensive loss.
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 own 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 ​ ​ December 31, ​ Observable Inputs ​ Observable Inputs ​ Unobservable Description ​ 2020 ​ (Level 1) ​ (Level 2) ​ (Level 3) Asset retirement obligations ​ $ 1,814,338 ​ $ — ​ $ — ​ $ 1,814,338 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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 ​ ​
Concentrations of Credit Risk	Concentrations of Credit Risk The Company maintains its cash and cash equivalents primarily in depository and money market accounts within two large financial institutions in the United States and one large financial institution in the United Kingdom and Ireland. Cash balances deposited at these major financial banking institutions exceed the insured limit. The Company has not experienced any losses on its bank deposits and believes these deposits do not expose the Company to any significant credit risk.
Intangible Assets	Intangible Assets Intangible assets consist of purchased rights to licensed technology as it relates to the Company’s manufacturing processes and has future alternative in the Company’s operations. The licensed technology is being amortized on a straight-line basis over 7 years, which represents the estimated periods of benefit and the expected pattern of consumption (see Note 6).
Property, Plant and Equipment, Net	Property, Plant and Equipment, Net Property, plant and equipment are stated at cost, net of accumulated depreciation. Depreciation is calculated using the straight-line method over the estimated useful lives of the respective assets. Leasehold improvements are depreciated over the lesser of their useful lives or the life of the lease (see Note 5). The estimated useful lives of the asset categories are as follows: ​ ​ ​ ​ Asset Category Useful Lives Computer and office equipment 3 years Laboratory equipment 5 years Manufacturing equipment 7 years Furniture and fixtures 5 years Leasehold improvements lesser of useful life or remaining term of lease ​ Expenditures for leasehold improvements are capitalized, and expenditures for maintenance and repairs are expensed to operations as incurred. ASC Topic 360, Property, Plant and Equipment
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 of . Asset retirement obligations currently reported on the Company’s consolidated balance sheets 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 consolidated statements of operations and comprehensive loss. The change in asset retirement obligations is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended December 31, ​ ​ 2020 ​ 2019 Balance at beginning of period $ 1,654,755 $ 128,119 Additional asset retirement obligations during the period ​ — ​ 1,270,262 Amortization of interest ​ 136,069 ​ 20,621 Change in fair value ​ — ​ 255,999 Effects of exchange rate ​ 23,514 ​ (20,246) Balance at end of period ​ $ 1,814,338 ​ $ 1,654,755
Share-Based Compensation Expense	​ Share-Based Compensation Expense Options The Company grants share options to employees, non-employee members of the Company’s board of directors and non-employee consultants as compensation for services performed. Employee and non-employee members of the board of directors’ awards of share-based compensation are accounted for in accordance with ASC 718, Compensation Stock Compensation, . Using this model, fair value is calculated based on assumptions with respect to (i) the fair value of the Company’s ordinary shares on the grant date; (ii) expected volatility of the Company’s ordinary share price, (iii) the periods of time over which the optionees are expected to hold their options prior to exercise (expected term), (iv) expected dividend yield on the Company’s ordinary shares, and (v) risk-free interest rates. As there had been no public market for the Company’s ordinary shares until the Company’s initial public offering (“IPO”) on June 7, 2018, the estimated fair value of the ordinary shares until that time had been determined by the Company’s board of directors as of the date of each option grant, with input from management, considering the most recently available third-party valuations of ordinary shares and the board of directors’ assessment of additional objective and subjective factors that it believed were relevant and which may have changed from the date of the most recent valuation through the date of the grant. The assumptions underlying these valuations represented management’s best estimate, which involved inherent uncertainties and the application of management’s judgment. As a result, if the Company had used different assumptions or estimates, the fair value of its ordinary shares and its share-based compensation expense could have been materially different. The fair value of ordinary shares after the Company’s IPO was determined based upon the closing share price on the date of grant. Since the Company’s ordinary shares had not been traded on a public exchange prior to the Company’s IPO and have only been traded on a public exchange for a short period of time since the Company’s IPO, the Company believes that it does not have sufficient company-specific information available to determine the expected term based on its historical data. As a result, the expected term of share options granted to the optionees is determined using the average of the vesting period and contractual life of the option, an accepted method for the Company’s option grants under the Securities and Exchange Commission’s (“SEC”) Staff Accounting Bulletin No. 107 and No. 110, Share-Based Payment. Similarly, the Company believes that its future volatility could differ materially during the expected term from the volatility that would be calculated from its historical share prices to date. Consequently, expected volatility is based on an analysis of guideline companies in accordance with ASC 718. The expected dividend yield is zero as the Company has never paid dividends and does not currently anticipate paying any in the foreseeable future. Risk-free interest rates are based on quoted U.S. Treasury rates for securities with maturities approximating the option’s expected term.
Restricted Shares	Restricted Shares In connection with certain employment, service and research agreements, the Company has granted restricted ordinary shares as compensation. The ordinary shares are recognized in the consolidated statements of operations and comprehensive loss based on their grant date fair values. Compensation cost relating to share grants with service-based graded vesting schedules is recognized based on the vesting schedule. Restricted Share Units The Company grants restricted share units (“RSUs”) to employees and non-employee consultants as compensation for services performed. Awards of RSUs are accounted for in accordance with ASC 718, Compensation Stock Compensation, .
Collaboration Arrangements	Collaboration Arrangements The Company evaluates its collaborative arrangements pursuant to ASC 808, Collaborative Arrangements Revenue from Contracts with Customers contractual terms of collaborative arrangements and assesses whether the arrangement involves a joint operating activity pursuant to which the Company is an active participant and is exposed to significant risks and rewards with respect to the arrangement. If the Company is an active participant and is exposed to significant risks and rewards with respect to the arrangement, the Company accounts for the arrangement as a collaboration under ASC 808. To date, the Company has entered into two separate collaboration agreements, both of which are with Janssen, which were determined to be within the scope of ASC 808. 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 11 for further information related to the accounting for the 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 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 consolidated statement 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, other costs associated with clinical and preclinical activities and regulatory operations and acquisition of in process research and development write-offs. 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 consolidated financial statements as prepaid or accrued research and development expenses, as the case may be.
Income Taxes	Income Taxes Income taxes are recorded in accordance with ASC Topic 740, Income Taxes The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. As of December 31, 2020 and 2019, the Company recorded unrecognized tax positions of $512,785 and $0 , respectively. The Company is required to estimate income taxes in each of the jurisdictions in which it operates.
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 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 ordinary share equivalents 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: ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ 2020 2019 Restricted share units ​ 545,000 ​ — Share options 4,824,771 3,645,360 Restricted ordinary shares subject to forfeiture ​ — ​ 217,726 ​ 5,369,771 3,863,086
Other Comprehensive Loss	Other Comprehensive Loss Other comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. The only component of other comprehensive loss impacting the Company is foreign currency translation.
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: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 United States ​ $ 17,536,207 ​ $ 14,354,792 United Kingdom ​ 44,487,022 ​ 39,476,700 Ireland ​ ​ 27,413,397 ​ ​ — Netherlands ​ 1,684,798 ​ 1,076,286 ​ ​ $ 91,121,424 ​ $ 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 In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 Revenue from Contracts with Customers In August 2018, the FASB issued ASU No. 2018-15, Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. ASU 2018-15 requires that certain implementation costs incurred in a cloud computing arrangement be deferred and recognized over the term of the arrangement. The new standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, and early adoption is permitted. The adoption of ASU 2018-15 on January 1, 2020 did not have a material impact on the current financial statements. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740) – Simplifying the Accounting for Income Taxes . ASU 2019-12 simplifies the accounting for income taxes by removing exceptions within the general principles of Topic 740 regarding the calculation of deferred tax liabilities, the incremental approach for intraperiod tax allocation, and calculating income taxes in an interim period. In addition, the ASU adds clarifications to the accounting for franchise tax (or similar tax), which is partially based on income, evaluating tax basis of goodwill recognized from a business combination and reflecting the effect of any enacted changes in tax laws or rates in the annual effective tax rate computation in the interim period that includes the enactment date. The ASU is effective for fiscal year beginning after December 15, 2020, and will be applied either retrospectively or prospectively based upon the applicable amendments. Early adoption is permitted. The Company has elected to adopt this ASU as of January 1, 2020 on a prospective basis. The adoption of ASU 2019-12 did not have a material impact on the current financial statements.
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)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Schedule of Company's Financial Assets and Liabilities Measured at Fair Value	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement Using: ​ ​ ​ Significant Significant Other Significant ​ ​ December 31, ​ Observable Inputs ​ Observable Inputs ​ Unobservable Description ​ 2020 ​ (Level 1) ​ (Level 2) ​ (Level 3) Asset retirement obligations ​ $ 1,814,338 ​ $ — ​ $ — ​ $ 1,814,338 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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 Estimated Useful Lives of Assets	​ ​ ​ ​ Asset Category Useful Lives Computer and office equipment 3 years Laboratory equipment 5 years Manufacturing equipment 7 years Furniture and fixtures 5 years Leasehold improvements lesser of useful life or remaining term of lease
Schedule of Change in Asset Retirement Obligations	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended December 31, ​ ​ 2020 ​ 2019 Balance at beginning of period $ 1,654,755 $ 128,119 Additional asset retirement obligations during the period ​ — ​ 1,270,262 Amortization of interest ​ 136,069 ​ 20,621 Change in fair value ​ — ​ 255,999 Effects of exchange rate ​ 23,514 ​ (20,246) Balance at end of period ​ $ 1,814,338 ​ $ 1,654,755
Schedule of Anti-dilutive Securities Excluded from Computation of Earnings per Share	​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ 2020 2019 Restricted share units ​ 545,000 ​ — Share options 4,824,771 3,645,360 Restricted ordinary shares subject to forfeiture ​ — ​ 217,726 ​ 5,369,771 3,863,086
Summary of Non-Current Assets by Geographical Area	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 United States ​ $ 17,536,207 ​ $ 14,354,792 United Kingdom ​ 44,487,022 ​ 39,476,700 Ireland ​ ​ 27,413,397 ​ ​ — Netherlands ​ 1,684,798 ​ 1,076,286 ​ ​ $ 91,121,424 ​ $ 54,907,778

Prepaid Expenses (Tables)

Prepaid Expenses (Tables)	12 Months Ended
	Dec. 31, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Summary of Prepaid Expenses	Prepaid expenses at December 31, 2020 and 2019 consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 Insurance ​ $ 2,901,728 ​ $ 1,758,915 Clinical trial costs ​ 1,624,873 ​ 1,349,657 Manufacturing costs ​ 1,395,141 ​ 259,509 Dues and license fees ​ 515,328 ​ 264,123 Rent ​ 169,038 ​ 183,952 Research and development ​ 164,338 ​ 239,161 Other ​ 311,301 ​ 408,768 ​ ​ $ 7,081,747 ​ $ 4,464,085

Property, Plant and Equipment_2

Property, Plant and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Equipment, net	Property, plant and equipment, net at December 31, 2020 and 2019 consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 Leasehold improvements ​ $ 33,776,712 ​ $ 17,557,316 Manufacturing equipment ​ 7,021,162 ​ 5,647,484 Laboratory equipment ​ 7,350,285 ​ 3,700,632 Computer and office equipment ​ 3,712,884 ​ 1,066,984 Furniture and fixtures ​ 567,730 ​ 441,101 ​ ​ 52,428,773 ​ 28,413,517 Less: Accumulated depreciation ​ (8,386,870) ​ (4,555,409) ​ ​ $ 44,041,903 ​ $ 23,858,108

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Intangible Assets
Schedule of Intangible Assets	The following table presents the details of the Company’s intangible assets as of December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortization ​ Gross Carrying ​ Accumulated ​ ​ ​ Type Period Amount Amortization Net Licensed Technology ​ 7 years ​ $ 2,144,541 ​ $ 25,530 ​ $ 2,119,011
Schedule of Amortization Expense	As of December 31, 2020, the expected amortization expense for the next five years and thereafter is as follows: ​ ​ ​ ​ ​ ​ Amortization ​ ​ Expense 2021 ​ $ 306,360 2022 ​ ​ 306,360 2023 ​ ​ 306,360 2024 ​ ​ 306,360 2025 ​ ​ 306,360 Thereafter ​ ​ 587,211 Total amortization ​ $ 2,119,011

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2020
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 Clinical trial costs ​ $ 11,154,015 ​ $ 7,788,077 Compensation and benefits ​ ​ 3,791,303 ​ ​ 6,850,335 Manufacturing costs ​ 1,885,848 ​ 125,717 Professional fees ​ 1,219,116 ​ 486,743 Consulting ​ 1,046,774 ​ 1,247,989 Fixed assets ​ 948,571 ​ 1,108,362 Rent and facilities costs ​ 662,040 ​ 283,876 Other ​ 153,153 ​ 192,658 ​ ​ $ 20,860,820 ​ $ 18,083,757

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 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 years ended December 31, 2020 and 2019 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ Weighted- ​ Average ​ ​ ​ ​ ​ ​ Average ​ ​ Remaining ​ ​ ​ ​ Number of ​ Exercise ​ ​ Contractual ​ ​ ​ ​ Options ​ Price ​ ​ Life (years) ​ Outstanding at December 31, 2018 ​ 3,254,365 ​ $ 7.64 ​ ​ Granted ​ 551,000 ​ 17.94 ​ ​ Exercised ​ (134,533) ​ 4.14 ​ ​ Expired ​ — ​ — ​ ​ Forfeited ​ (25,472) ​ 9.37 ​ ​ Outstanding at December 31, 2019 ​ 3,645,360 ​ ​ 9.31 ​ 8.45 years Granted ​ 1,666,500 ​ 15.91 ​ ​ ​ Exercised ​ (109,296) ​ 7.69 ​ ​ ​ Expired ​ ​ — ​ ​ — ​ ​ ​ ​ Forfeited ​ (377,793) ​ 15.71 ​ ​ ​ Outstanding at December 31, 2020 ​ 4,824,771 ​ $ 11.85 ​ ​ 7.67 years Options exercisable at December 31, 2020 ​ 2,249,113 ​ $ 8.88 ​ 6.71 years Aggregate intrinsic value of options outstanding as of December 31, 2020 ​ $ 22,338,580 ​ ​ ​ Aggregate intrinsic value of options exercisable as of December 31, 2020 ​ $ 15,365,249 ​ ​ ​
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, 2018 653,174 ​ $ 9,797,610 Vested during 2019 (435,448) ​ (6,531,720) Non-vested at December 31, 2019 217,726 ​ $ 3,265,890 Vested during 2020 (217,726) ​ (3,265,890) Non-vested at December 31, 2020 — ​ $ —
Schedule of Share-Based Compensation Expense	During the years ended December 31, 2020 and 2019 the Company recognized total share-based compensation expense in the accompanying consolidated statements of operations and comprehensive loss as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 2019 Research and development ​ $ 6,025,136 ​ $ 5,059,046 General and administrative ​ 12,391,444 ​ 10,869,924 Total share-based compensation ​ $ 18,416,580 ​ $ 15,928,970

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Summary of Net Operating Loss Carryforwards	​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ State/City United Kingdom ​ $ 142,241,850 ​ $ — United States ​ $ 34,743,371 ​ $ 34,366,051 Netherlands ​ $ 26,111,603 ​ $ — Ireland ​ $ 626,498 ​ $ —
Schedule of Company's Pre-Tax Earnings	The Company's pre-tax earnings are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 United Kingdom ​ $ (41,372,993) ​ $ (37,993,537) United States ​ (13,472,052) ​ (16,303,213) Netherlands ​ (2,471,442) ​ (449,485) Ireland ​ ​ (675,517) ​ ​ — ​ ​ $ (57,992,004) ​ $ (54,746,235)
Schedule of Reconciliation of Income Tax Benefit with Amounts at the U.K. Statutory Income Tax Rate	The following table summarizes a reconciliation of income tax benefit compared with the amounts at the UK statutory income tax rate: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ December 31, 2019 ​ Statutory rate ​ (11,018,481) 19.00 % ​ (10,401,785) 19.00 % Permanent differences - other ​ 1,976,028 (3.41) % ​ (411,651) 0.75 % RTP and other adjustment ​ (2,135,978) ​ 3.68 % ​ 3,068,999 ​ (5.61) % State and local rate, net of federal tax ​ (1,478,111) 2.55 % ​ (2,041,097) 3.73 % U.K. tax credit ​ 574,161 ​ (0.99) % ​ 1,278,072 ​ (2.33) % U.S. tax credit ​ (1,242,356) ​ 2.14 % ​ (1,257,481) ​ 2.30 % Foreign tax rate differential ​ (254,199) ​ 0.44 % ​ (347,301) ​ 0.63 % UK rate change (19% & 17% at expected DTA turn) ​ (2,233,752) 3.85 % ​ 362,092 (0.66) % US state rate change ​ 25,041 ​ (0.04) % ​ — ​ - % Change in valuation allowance ​ 15,787,647 (27.22) % ​ 9,750,152 (17.81) % Actual income tax benefit effective tax rate ​ — 0.00 % ​ — 0.00 % ​
Schedule of Expense/(Benefit) for Income Taxes from Continuing Operations	The Expense/(Benefit) for income taxes from continuing operations consists of the following: ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 Current Tax Expense/(Benefit) United Kingdom — — United States — — Netherlands — — Ireland ​ — ​ — Total Current — — Deferred Tax Expense/(Benefit) United Kingdom (9,197,319) (3,036,498) United States (5,851,708) (6,631,936) Netherlands (674,817) (81,718) Ireland ​ (63,803) ​ — Total Deferred (15,787,647) (9,750,152) Change in Valuation Allowance 15,787,647 9,750,152 Total Income Tax Expense/(Benefit) — — ​
Schedule of Deferred Tax Assets and Liabilities	Deferred Tax Assets/(Liabilities) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 ​ Deferred Tax Assets: ​ ​ ​ ​ ​ ​ ​ Net operating loss carryforwards ​ $ 43,831,308 ​ $ 31,929,792 ​ Lease liability ​ 6,150,436 ​ ​ 6,012,466 ​ R&D credit ​ 5,819,100 ​ ​ 2,635,188 ​ Share-based compensation ​ ​ 5,392,358 ​ ​ 2,831,696 ​ Other ​ 298,462 ​ ​ 374,507 ​ Deferred tax assets ​ 61,491,664 ​ 43,783,649 ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred Tax Liabilities: ​ ​ ​ ​ ​ ​ ​ Indefinite-lived intangibles ​ (173,431) ​ ​ (173,431) ​ Depreciation ​ ​ (2,252,190) ​ ​ (624,361) ​ Right of use assets ​ (5,928,527) ​ ​ (5,635,987) ​ Less: valuation allowance ​ (53,310,947) ​ (37,523,301) ​ Net deferred tax liability ​ $ (173,431) ​ $ (173,431) ​ ​
Schedule of Unrecognized Tax Benefits	​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 Unrecognized tax benefits as of January 1 $ — $ — Gross increases/(decreases) related to current year ​ 138,040 ​ — Gross increases/(decreases) related to prior years ​ 374,745 ​ — Foreign currency translation ​ ​ — ​ ​ — Unrecognized tax positions as of December 31 $ 512,785 $ —

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 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 year ended December 31, 2020 ​ ​ (15,562,985) Effects of exchange rate ​ ​ 2,190,671 Deferred revenue at December 31, 2020 ​ $ 72,841,777

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Schedule of Components of Lease Cost	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 ​ 2019 Finance lease cost ​ ​ ​ Amortization of right-of-use assets ​ $ 519,379 ​ $ 300,229 Interest on lease liabilities ​ 3,081 ​ 2,409 Total finance lease cost ​ 522,460 ​ 302,638 Operating lease cost ​ 3,422,795 ​ 2,384,048 Short-term lease cost ​ 714,172 ​ 1,282,709 Total lease cost ​ $ 4,659,427 ​ $ 3,969,395
Schedule of Consolidated Balance Sheets for Leases	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ ​ 2020 ​ ​ 2019 ​ Operating leases ​ ​ ​ ​ ​ Right-of-use asset ​ $ 21,485,924 ​ ​ $ 21,857,600 ​ Capitalized lease obligations ​ $ 22,220,515 ​ ​ $ 23,127,813 ​ Finance leases ​ ​ ​ ​ Right-of-use asset ​ $ 21,596,435 ​ ​ $ 7,144,848 ​ Capitalized lease obligations ​ $ 28,325 ​ ​ $ 50,737 ​ Weighted-average remaining lease term ​ ​ ​ ​ Operating leases ​ 7.0 years ​ 7.9 years Finance leases ​ 175.1 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	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 ​ ​ 2019 ​ Cash paid for amounts included in the measurement of lease liabilities ​ Operating cash flows from finance leases $ 21,604 ​ $ 28,187 ​ Operating cash flows from operating leases $ 3,790,734 ​ $ 1,246,169 ​ Financing cash flows from finance leases $ 3,081 ​ $ 2,355 ​ ​ ​ ​ ​ ​ ​ ​ Right-of-use assets obtained in exchange for lease liabilities ​ ​ Operating leases $ 1,889,065 ​ $ 23,279,980 ​ Finance leases $ — ​ $ 44,629 ​
Schedule of Future Minimum Lease Payments Under Non-Cancellable Leases	​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases Finance Leases 2021 ​ $ 4,383,995 ​ $ 17,505 2022 ​ ​ 4,475,018 ​ ​ 13,129 2023 ​ 4,566,431 ​ — 2024 ​ 4,405,144 ​ — 2025 ​ 4,381,270 ​ — Thereafter ​ 7,151,280 ​ — Total undiscounted lease payments ​ $ 29,363,138 ​ $ 30,634 Less: Imputed interest ​ (7,142,623) ​ (2,309) Total lease liabilities ​ $ 22,220,515 ​ $ 28,325

Principal Business Activity - A

Principal Business Activity - Additional Information (Details) - USD ($)	Jan. 30, 2019	Jan. 01, 2019	Dec. 31, 2020	Dec. 31, 2019	Oct. 17, 2019	Dec. 31, 2018
Schedule Of Description Of Business [Line Items]
Accumulated deficit			$ (261,027,956)	$ (203,035,952)
Cash flows from operations			(63,967,799)	20,044,897
Cash, cash equivalents and restricted cash			$ 209,520,355	227,356,760		$ 68,203,551
Minimum
Schedule Of Description Of Business [Line Items]
Offsetting expense, period			12 months
Arthrogen B.V. [Member]
Schedule Of Description Of Business [Line Items]
Equity acquired					100.00%
Janssen Pharmaceuticals Inc [Member] | Collaboration Agreement [Member]
Schedule Of Description Of Business [Line Items]
Collaboration agreement upfront payment	$ 100,000,000	$ 100,000,000
Janssen Pharmaceuticals Inc [Member] | Collaboration Option And License Agreement [Member]
Schedule Of Description Of Business [Line Items]
Collaboration agreement upfront payment				$ 100,000,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Tax Incentive Receivable (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Tax incentive receivable	$ 12,930,062	$ 11,974,437
Research and Development Expense	33,910,481	24,875,659
Other Current Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Tax incentive receivable	5,300,000	12,000,000
VAT receivable	$ 4,000,000	$ 1,800,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Company's Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Foreign Exchange Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency forward contracts	$ 0
Restricted Cash [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, net asset (liability)		$ 123,376
Asset Retirement Obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, net asset (liability)	1,814,338	1,654,755
Fair Value, Inputs, Level 1 [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] | Asset Retirement Obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, net asset (liability)	$ 1,814,338	$ 1,654,755

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives of Assets (Details)	12 Months Ended
	Dec. 31, 2020
Computer Equipment And Software [Member]
Depreciation Amortization Impairment [Line Items]
Estimated useful life (years)	3 years
Laboratory Equipment [Member]
Depreciation Amortization Impairment [Line Items]
Estimated useful life (years)	5 years
Manufacturing Equipment [Member]
Depreciation Amortization Impairment [Line Items]
Estimated useful life (years)	7 years
Furniture & Fixtures [Member]
Depreciation Amortization Impairment [Line Items]
Estimated useful life (years)	5 years
Leasehold Improvements [Member]
Depreciation Amortization Impairment [Line Items]
Estimated useful life (years)	lesser of useful life or remaining term of lease

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Schedule of Change in Asset Retirement Obligations (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Asset Retirement Obligation [Abstract]
Balance at beginning of period	$ 1,654,755	$ 128,119
Additional asset retirement obligations during the period		1,270,262
Amortization of interest	136,069	20,621
Change in fair value		255,999
Effects of exchange rate	23,514	(20,246)
Balance at end of period	$ 1,814,338	$ 1,654,755

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Impairment charges	$ 0	$ 0
Unrecognized tax positions	512,785	0
Unrecognized tax benefits, income tax penalties and interest accrued	$ 0	$ 0
Measurement Input, Risk Free Interest Rate [Member]
Credit-adjusted risk-free rate	8

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Schedule of Anti-dilutive Securities Excluded from Computation of Earnings per Share (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earning per share, amount	5,369,771	3,863,086
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	4,824,771	3,645,360
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		217,726

Summary of Significant Accou_10

Summary of Significant Accounting Policies - Summary of Non-Current Assets by Geographical Area (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Operation By Geographical [Line Items]
Non-current assets	$ 91,121,424	$ 54,907,778
United States
Operation By Geographical [Line Items]
Non-current assets	17,536,207	14,354,792
United Kingdom
Operation By Geographical [Line Items]
Non-current assets	44,487,022	39,476,700
Ireland
Operation By Geographical [Line Items]
Non-current assets	27,413,397
Netherlands
Operation By Geographical [Line Items]
Non-current assets	$ 1,684,798	$ 1,076,286

Acquisitions - Emrys Bio Inc. (

Acquisitions - Emrys Bio Inc. (Details)	Apr. 09, 2020USD ($)$ / sharesshares
Acquisition
Fair value of asset acquisition in process R&D | $	$ 7,685,001
Acquisition Of Emrys [Member]
Acquisition
Total consideration | $	$ 7,685,001
Ordinary Shares [Member] | Acquisition Of Emrys [Member]
Acquisition
Number of shares issued	580,000
Share price | $ / shares	$ 13.25
On Closing Date [Member] | Ordinary Shares [Member] | Acquisition Of Emrys [Member]
Acquisition
Number of shares issued	232,000
On Closing Date [Member] | Restricted ordinary Shares [Member] | Acquisition Of Emrys [Member]
Acquisition
Number of shares issued	290,000
Following Closing Date [Member] | Ordinary Shares [Member] | Acquisition Of Emrys [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 Of Emrys [Member]
Acquisition
Vesting percentage	50.00%
Second Anniversary Of Closing Date [Member] | Restricted ordinary Shares [Member] | Acquisition Of Emrys [Member]
Acquisition
Vesting percentage	50.00%

Acquisitions - Arthrogen B.V. (

Acquisitions - Arthrogen B.V. (Details) - Arthrogen B.V. [Member]	Oct. 17, 2019EUR (€)	Oct. 17, 2019USD ($)
Acquisition Date [Line Items]
Ownership percentage	100.00%	100.00%
Purchase price consideration	€ 500,000	$ 558,335
Acquisition related costs	€ 94,692	$ 105,740

Prepaid Expenses - Summary of P

Prepaid Expenses - Summary of Prepaid Expenses (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Insurance	$ 2,901,728	$ 1,758,915
Clinical Trial Costs	1,624,873	1,349,657
Manufacturing Costs	1,395,141	259,509
Dues and License Fees	515,328	264,123
Rent	169,038	183,952
Research and Development	164,338	239,161
Other	311,301	408,768
Total	$ 7,081,747	$ 4,464,085

Property, Plant and Equipment_3

Property, Plant and Equipment, net - Schedule of Property, Plant and Equipment, net (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 52,428,773	$ 28,413,517
Less: Accumulated depreciation	(8,386,870)	(4,555,409)
Property, plant and equipment, net	44,041,903	23,858,108
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	33,776,712	17,557,316
Manufacturing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,021,162	5,647,484
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,350,285	3,700,632
Computer and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	3,712,884	1,066,984
Furniture & Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 567,730	$ 441,101

Property, Plant and Equipment_4

Property, Plant and Equipment, net - Additional Information (Details) - USD ($)	Jan. 01, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Asset retirement obligations, discounted rate	8.00%
Asset retirement obligations	$ 3,736,404	$ 1,814,338	$ 1,654,755	$ 128,119
Depreciation expense		4,171,626	2,238,560
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Asset retirement obligations		$ 1,643,794
Computer and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Capital lease obligations			$ 95,880

Intangible Assets (Details)

Intangible Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Nov. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Net	$ 2,119,011		$ 0
Licensed Technology
Finite-Lived Intangible Assets [Line Items]
Amortization Period	7 years
Gross Carrying Amount	$ 2,144,541	$ 2,100,000
Accumulated Amortization	25,530
Net	$ 2,119,011

Intangible Assets - Asset Trans

Intangible Assets - Asset Transaction (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Intangible Assets
Intangible assets	$ 2,119,011	$ 0
Amortization expense	$ 25,530	$ 0

Intangible Assets - Amortizatio

Intangible Assets - Amortization Expense (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Amortization expense
2021	$ 306,360
2022	306,360
2023	306,360
2024	306,360
2025	306,360
Thereafter	587,211
Net	$ 2,119,011	$ 0

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Clinical trial costs	$ 11,154,015	$ 7,788,077
Compensation and benefits	3,791,303	6,850,335
Manufacturing costs	1,885,848	125,717
Professional fees	1,219,116	486,743
Consulting	1,046,774	1,247,989
Fixed assets	948,571	1,108,362
Rent and facilities costs	662,040	283,876
Other	153,153	192,658
Accrued Expenses	$ 20,860,820	$ 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	Jan. 31, 2021shares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance | shares					5,620,882	3,054,996
Additional shares reserved for issuance | shares				1,767,566
Shares available for future issuance | shares					1,584,468
Weighted-average remaining contractual life of options, outstanding					7 years 8 months 1 day	8 years 5 months 12 days
Fair value of options Vested					$ 8,156,474	$ 6,098,621
Weighted average grant date fair value of options granted | $ / shares					$ 11.87	$ 13.79
Share options granted during the period | shares					1,666,500	551,000
Share-based compensation					$ 18,416,580	$ 15,928,970
Total share-based compensation					18,416,580	15,928,970
Excess tax benefits, operating activities					$ 0	0
Maximum
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					$ 12,391,444	10,869,924
Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation					6,025,136	5,059,046
Restricted ordinary shares subject to forfeiture [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares awarded, per share | $ / shares			$ 15
Ordinary shares | shares			1,306,348
Fully-diluted outstanding shares			5.00%
Share-based compensation					6,545,688	15,982,670
Total share-based compensation					2,906,626	6,531,744
Restricted ordinary shares subject to forfeiture [Member] | General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation					3,639,062	9,450,926
Restricted share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unvested options compensation expense not yet recognized					$ 8,265,667
Period expected to realize unrecognized compensation expense					3 years 2 months 12 days
Total share-based compensation					$ 2,643,833
Restricted share units | General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation					2,509,495
Restricted share units | Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation					134,338
Share options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unvested options compensation expense not yet recognized					$ 22,808,502
Period expected to realize unrecognized compensation expense					3 years 10 months 24 days
Total share-based compensation					$ 12,866,121	8,024,476
Share options | General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation					6,975,323	4,338,180
Share options | Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation					$ 5,890,798	$ 3,686,296
Executive Officer [Member] | Restricted ordinary shares subject to forfeiture [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance | shares				505,000
Employee And Consultant [Member] | Share options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance | shares				1,303,700
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%
Number of quarters for vesting | item			8
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 ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Number of Options
Number of options, Beginning balance	3,645,360	3,254,365
Number of options, Granted	1,666,500	551,000
Number of options, Exercised	(109,296)	(134,533)
Number of options, Expired		0
Number of options, Forfeited	(377,793)	(25,472)
Number of options, Ending balance	4,824,771	3,645,360
Weighted-Average Exercise Price
Weighted-average exercise price, Beginning balance	$ 9.31	$ 7.64
Weighted-average exercise price, Granted	15.91	17.94
Weighted-average exercise price, Exercised	7.69	4.14
Weighted-average exercise price, Expired		0
Weighted-average exercise price, Forfeited	15.71	9.37
Weighted-average exercise price, Ending balance	$ 11.85	$ 9.31
Options additional disclosures
Number of options, Options exercisable	2,249,113
Weighted-average exercise price, Option exercisable	$ 8.88
Weighted-average remaining contractual life of options, outstanding	7 years 8 months 1 day	8 years 5 months 12 days
Weighted-average remaining contractual life of options, exercisable	6 years 8 months 15 days
Aggregate intrinsic value, options outstanding	$ 22,338,580
Aggregate intrinsic value, options exercisable	$ 15,365,249

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	12 Months Ended
	Dec. 31, 2020	Dec. 31, 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
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	5 years 6 months	5 years 6 months
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (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) - Restricted ordinary shares subject to forfeiture [Member] - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested Ordinary Shares, Beginning Balance	217,726	653,174
Vested, Ordinary Shares	(217,726)	(435,448)
Non-vested Ordinary Shares, Ending Balance		217,726
Non-vested Value, Beginning Balance	$ 3,265,890	$ 9,797,610
Vested, Value	$ (3,265,890)	(6,531,720)
Non-vested Value, Ending Balance		$ 3,265,890

Share-Based Compensation - Sc_2

Share-Based Compensation - Schedule of Share-Based Compensation Expense (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Expense [Line Items]
Total share-based compensation	$ 18,416,580	$ 15,928,970
General and Administrative Expense [Member]
Share Based Compensation Expense [Line Items]
Total share-based compensation	12,391,444	10,869,924
Research and Development Expenses [Member]
Share Based Compensation Expense [Line Items]
Total share-based compensation	$ 6,025,136	$ 5,059,046

Ordinary Shares - Additional In

Ordinary Shares - Additional Information (Details) - USD ($)	Oct. 31, 2019	Aug. 07, 2019	Jul. 07, 2019	Mar. 21, 2019	Feb. 27, 2019	Dec. 31, 2020	Nov. 30, 2020	Jul. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Oct. 31, 2020	Apr. 30, 2020
Common stock, shares issued						44,189,150			44,189,150	36,791,906
Offering costs									$ 5,141,012	$ 7,497,852
Number of ordinary shares sold									993,448
Proceeds from the issuance of ordinary shares									$ 87,050,686	$ 155,200,007
Ordinary Shares [Member]
Common stock, shares issued											22,500	522,000
Ordinary Shares [Member] | License Agreement [Member]
Ordinary shares issued in connection with a license agreement (in shares)				158,832						158,832
Vendor [Member]
Shares issued			19,807
Net of issuance costs			$ 421,500
Consultant [Member]
Shares issued	95,000
Net of issuance costs	$ 1,372,750
IPO [Member]
Common stock, shares issued		3,200,000
Proceeds from the issuance of ordinary shares		$ 75,000,000
Offering costs		$ 5,100,000
Over-Allotment Option [Member]
Common stock, shares issued						750,000	5,000,000		750,000
Offering costs									$ 4,600,000
Proceeds from the issuance of ordinary shares						$ 9,600,000	$ 64,300,000
At-the-market offering [Member]
Aggregate offer price								$ 75,000,000
Proceeds from issuance of private placement									13,200,000
Offering costs									505,650
Net of issuance costs									$ 12,657,536
At-the-market offering [Member] | Ordinary Shares [Member]
Shares issued									993,448
Net of issuance costs									$ 39
Private Placement [Member]
Offering costs					$ 2,400,000
JJDC [Member] | Private Placement [Member]
Common stock, shares issued					2,898,550
JJDC [Member] | Private Placement [Member] | Collaboration Option And License Agreement [Member]
Common stock, shares issued					5,797,102
Proceeds from the issuance of ordinary shares					$ 80,000,000
JJDC | Private Placement [Member]
Common stock, shares issued					2,898,550

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	Apr. 01, 2020	Apr. 01, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017
Income Taxes Disclosure [Line Items]
Federal net operating loss carryforwards					$ 6,800,000
State net operating loss carryforwards					$ 6,700,000
Deferred tax assets, tax credit carryforwards			$ 5,819,100	$ 2,635,188
Unrecognized tax positions			512,785	0
Unrecognized tax benefits, income tax penalties and interest accrued			$ 0	$ 0
Her Majesty's Revenue and Customs (HMRC) [Member]
Income Taxes Disclosure [Line Items]
Tax rate	18.00%	19.00%	19.00%
Her Majesty's Revenue and Customs (HMRC) [Member] | Tax Year 2020 [Member]
Income Taxes Disclosure [Line Items]
Tax rate	17.00%
United States | Federal [Member]
Income Taxes Disclosure [Line Items]
Deferred tax assets, tax credit carryforwards			$ 5,127,849
United Kingdom | Her Majesty's Revenue and Customs (HMRC) [Member] | Research Tax Credit Carryforward
Income Taxes Disclosure [Line Items]
Deferred tax assets, tax credit carryforwards			$ 1,204,036
Netherlands | Losses incurred prior to 2019
Income Taxes Disclosure [Line Items]
Operating loss carryforwards expiration period			9 years
Netherlands | Losses incurred after 2018
Income Taxes Disclosure [Line Items]
Operating loss carryforwards expiration period			6 years

Income Taxes - Net Operating Lo

Income Taxes - Net Operating Loss Carryforwards (Details)	Dec. 31, 2020USD ($)
Federal [Member] | United States
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 34,743,371
Federal [Member] | United Kingdom
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	142,241,850
Federal [Member] | Netherlands
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	26,111,603
Federal [Member] | Ireland
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	626,498
State [Member] | United States
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 34,366,051

Income Taxes - Summary of Compa

Income Taxes - Summary of Company's Pre-Tax Earnings (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Before Income Taxes [Line Items]
Total	$ (57,992,004)	$ (54,746,235)
Foreign country [Member] | Her Majesty's Revenue and Customs (HMRC) [Member] | United Kingdom
Income Before Income Taxes [Line Items]
Total	(41,372,993)	(37,993,537)
Foreign country [Member] | Tax and Customs Administration, Netherlands [Member] | Netherlands
Income Before Income Taxes [Line Items]
Total	(2,471,442)	(449,485)
Foreign country [Member] | Revenue Commissioners, Ireland [Member] | Ireland
Income Before Income Taxes [Line Items]
Total	(675,517)
Federal [Member] | Internal Revenue Service (IRS) [Member] | United States
Income Before Income Taxes [Line Items]
Total	$ (13,472,052)	$ (16,303,213)

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of Income Tax Benefit with Amounts at the U.K. Statutory Income Tax Rate (Details) - USD ($)	Apr. 01, 2020	Dec. 31, 2020	Dec. 31, 2019
Change in valuation allowance		$ 15,787,647	$ 9,750,152
Total Income Tax Expense (Benefit)		0	0
Her Majesty's Revenue and Customs (HMRC) [Member]
Statutory rate		(11,018,481)	(10,401,785)
Permanent differences - other		1,976,028	(411,651)
RTP and other adjustments		(2,135,978)	3,068,999
State and local rate, net of federal tax		(1,478,111)	(2,041,097)
U.K. Tax credit		574,161	1,278,072
U.S. Tax credit		(1,242,356)	(1,257,481)
Foreign tax rate differential		(254,199)	(347,301)
UK Rate change (19% & 17% at expected DTA turn)		(2,233,752)	362,092
US state rate change		25,041
Change in valuation allowance		$ 15,787,647	$ 9,750,152
Tax rate	17.00%	19.00%	19.00%
Permanent differences-other		(3.41%)	0.75%
RTP and other adjustments		3.68%	(5.61%)
State and local rate, net of federal tax		2.55%	3.73%
U.K. Tax credit		(0.99%)	(2.33%)
U.S. Tax credit		2.14%	2.30%
Foreign tax rate differential		0.44%	0.63%
UK Rate change (19% & 17% at expected DTA turn)		3.85%	(0.66%)
US state rate change		(0.04%)
Change in valuation allowance		(27.22%)	(17.81%)
Actual income tax benefit effective tax rate		0.00%	0.00%
Her Majesty's Revenue and Customs (HMRC) [Member] | Tax Year 2020 [Member]
Tax rate			17.00%

Income Taxes - Schedule of Expe

Income Taxes - Schedule of Expense/(Benefit) for Income Taxes from Continuing Operations (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax Expense/(Benefit)
Total Deferred	$ (15,787,647)	$ (9,750,152)
Change in Valuation Allowance	15,787,647	9,750,152
Total Income Tax Expense (Benefit)	0	0
United Kingdom
Deferred Tax Expense/(Benefit)
Foreign	(9,197,319)	(3,036,498)
United States
Deferred Tax Expense/(Benefit)
United States	(5,851,708)	(6,631,936)
Netherlands
Deferred Tax Expense/(Benefit)
Foreign	(674,817)	$ (81,718)
Ireland
Deferred Tax Expense/(Benefit)
Foreign	$ (63,803)

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax Assets:
Net operating loss carryforwards	$ 43,831,308	$ 31,929,792
Lease liability	6,150,436	6,012,466
R&D credit	5,819,100	2,635,188
Share-based compensation	5,392,358	2,831,696
Other	298,462	374,507
Deferred tax assets	61,491,664	43,783,649
Deferred Tax Liabilities:
Indefinite-lived intangibles	(173,431)	(173,431)
Depreciation	(2,252,190)	(624,361)
Right of use assets	(5,928,527)	(5,635,987)
Less: valuation allowance	(53,310,947)	(37,523,301)
Net deferred tax liability	(173,431)	$ (173,431)
Federal [Member] | United States
Deferred Tax Assets:
R&D credit	$ 5,127,849

Income Taxes - Summary of Unrec

Income Taxes - Summary of Unrecognized Tax Positions (Details)	12 Months Ended
	Dec. 31, 2020USD ($)
Income Tax Uncertainties [Abstract]
Unrecognized tax benefits, beginning balance	$ 0
Gross increases related to current year	138,040
Gross increases related to prior years	374,745
Unrecognized tax benefits, ending balance	$ 512,785

Related Party Transactions - Co

Related Party Transactions - Collaboration and License Agreements (Details) - USD ($)	Jan. 30, 2019	Jan. 01, 2019	Oct. 16, 2018	Jan. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Feb. 27, 2019
Related Party Transaction [Line Items]
Shares issued to related party					44,189,150	36,791,906
Clinical IRD Product Candidate development | Maximum
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]
Collaboration agreement upfront payment	$ 100,000,000	$ 100,000,000
Deferred revenue - related party recognized as license revenue					$ 15,562,985	$ (13,291,956)
Reimbursement of research and development expenses					63,003,824	27,296,062
Deferred revenue - related party					72,841,777	86,214,091
Janssen Pharmaceuticals Inc [Member] | Collaboration Agreement [Member] | Prepaid Expenses [Member]
Related Party Transaction [Line Items]
Reimbursement of research and development expenses					5,596,735	0
Janssen Pharmaceuticals Inc [Member] | Collaboration Agreement [Member] | Research and Development Expenses [Member]
Related Party Transaction [Line Items]
Reimbursement of research and development expenses					$ 57,407,089	27,296,062
Janssen Pharmaceuticals Inc [Member] | Collaboration Option And License Agreement [Member]
Related Party Transaction [Line Items]
Collaboration agreement upfront payment						100,000,000
Janssen Pharmaceuticals Inc [Member] | Research, development and commercialization of gene therapies | Collaboration Option And License Agreement [Member]
Related Party Transaction [Line Items]
Collaboration agreement upfront payment				$ 100,000,000
Janssen Pharmaceuticals Inc [Member] | Clinical IRD Product Candidate development | Collaboration Agreement [Member]
Related Party Transaction [Line Items]
Percentage of costs payable on annual net sales of licensed product statement				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						$ 328,524
Deferred research funding, amortization period			8 months

Related Party Transactions - Pe

Related Party Transactions - Performance Obligation (Details) - Collaboration Agreement [Member] - Janssen Pharmaceuticals Inc [Member] - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01	Dec. 31, 2020USD ($)
Related Party Transaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 72,841,777
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	4 years 6 months

Related Party Transactions - Re

Related Party Transactions - Revenue Recognition (Details) - Janssen Pharmaceuticals Inc [Member] - Collaboration Agreement [Member] - USD ($)	Jan. 30, 2019	Jan. 01, 2019	Dec. 31, 2020	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			$ (15,562,985)	$ 13,291,956
Effects of exchange rate			2,190,671	(493,953)
Deferred revenue			$ 72,841,777	$ 86,214,091

Related Party Transactions - Ri

Related Party Transactions - Riboswitch Research Collaboration Agreement (Details) - Riboswitch Research - Janssen Pharmaceuticals Inc [Member] - Collaboration Agreement [Member] - USD ($)	Oct. 16, 2018	Dec. 31, 2019
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 658,667
Deferred research funding, amortization period	8 months
Research and Development Expenses [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amortized of deferred research funding		$ 444,399

Related Party Transactions - _2

Related Party Transactions - Research Agreement (Details) - USD ($)	Oct. 23, 2016	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Research and development expenses		$ 33,910,481	$ 24,875,659
UCL Consultants Limited | Master Services Agreement [Member]
Related Party Transaction [Line Items]
Term of agreement	4 years
Research and development expenses		203,000	306,000
Future obligations under agreement		0
UCL Consultants Limited | Master Services Agreement [Member] | Accounts Payable And Accrued Expenses
Related Party Transaction [Line Items]
Amount due under services agreement		$ 0	$ 166,404

Related Party Transactions - Li

Related Party Transactions - License Agreement (Details)	Mar. 23, 2020USD ($)	Mar. 15, 2018USD ($)shares	Mar. 15, 2018GBP (£)shares	Feb. 04, 2015USD ($)Program	Feb. 04, 2015GBP (£)Program	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Related Party Transaction [Line Items]
Research and development expenses						$ 33,910,481	$ 24,875,659
License Agreement [Member]
Related Party Transaction [Line Items]
Issuance of shares in connection with a license agreement							1,966,340
Research and development expenses						273,180	4,271,275
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 shares in connection with a license agreement		$ 1,966,000	£ 1,500,000
Research and development expenses						0	$ 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	$ 54,400,000
Maintenance fee				$ 66,000	£ 50,000
License arrangement upfront payment	$ 50,000		£ 1,500,000
Development and sales milestone payments	39,250,000
Prosecution and maintenance costs	$ 25,000
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

Related Party Transactions - Le

Related Party Transactions - Leases (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	May 31, 2020
Related Party Transaction [Line Items]
Operating lease rent expenses	$ 3,341,535	$ 1,776,631
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	969,478
Net gain on write-off of operating lease right of use asset and liability	143,590
Operating lease rent expenses	487,555	81,260
Letter of credit outstanding amount			$ 122,866
Kadmon Corporation LLC [Member]
Related Party Transaction [Line Items]
Cash payment	597,740	576,404
Amount due under services agreement	0	0
Kadmon Corporation LLC [Member] | Loss from operations
Related Party Transaction [Line Items]
Operating lease rent expenses	$ 597,740	$ 576,404

Leases - Additional Information

Leases - Additional Information (Details)	Aug. 04, 2020USD ($)contractproperty	Aug. 04, 2020GBP (£)contractproperty	Dec. 31, 2020USD ($)lease	Dec. 31, 2020GBP (£)lease	Dec. 31, 2019USD ($)	Dec. 31, 2020GBP (£)
Lessee, Lease, Description [Line Items]
Operating lease rent expenses			$ 3,341,535		$ 1,776,631
Short term lease commitments monthly amount			$ 56,000
Number of month-to-month leases | lease			2	2
Capitalized building costs			$ 13,801,007			£ 11,890,000
Annual lease cost and annual maintenance fees			$ 37,000	£ 31,000
Meira Ireland [Member] | Shannon Free Zone [Member]
Lessee, Lease, Description [Line Items]
Number of agreements | contract	2	2
Number of properties | property	2	2
Purchase price consideration	$ 21,200,000	£ 18,000,000
Minimum
Lessee, Lease, Description [Line Items]
Lease term			3 years	3 years
Maximum
Lessee, Lease, Description [Line Items]
Lease term			191 years	191 years

Leases - Schedule of Components

Leases - Schedule of Components of Lease Cost (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Amortization of right-of-use assets	$ 519,379	$ 300,229
Interest on lease liabilities	3,081	2,409
Total finance lease cost	522,460	302,638
Operating lease cost	3,422,795	2,384,048
Short-term lease cost	714,172	1,282,709
Total lease cost	$ 4,659,427	$ 3,969,395

Leases - Schedule of Consolidat

Leases - Schedule of Consolidated Balance Sheets for Leases (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Operating leases
Right-of-use asset	$ 21,485,924	$ 21,857,600
Capitalized lease obligations	$ 22,220,515	$ 23,127,813
Operating Lease, Liability, Statement of Financial Position [Extensible List]	mgtx:LeaseObligationsCurrent mgtx:LeaseObligationsNonCurrent	mgtx:LeaseObligationsCurrent mgtx:LeaseObligationsNonCurrent
Finance Lease
Right-of-use asset	$ 21,596,435	$ 7,144,848
Capitalized lease obligations	$ 28,325	$ 50,737
Weighted-average remaining lease term
Operating leases	7 years	7 years 10 months 24 days
Finance leases	175 years 1 month 6 days	107 years
Weighted-Average Discount Rate
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 ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from finance leases	$ 21,604	$ 28,187
Operating cash flows from operating leases	3,790,734	1,246,169
Financing cash flows from finance leases	3,081	2,355
Right-of-use assets obtained in exchange for lease liabilities
Operating leases	$ 1,889,065	23,279,980
Finance leases		$ 44,629

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Lease Payments Under Non-Cancellable Leases (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Operating Leases
2021	$ 4,383,995
2022	4,475,018
2023	4,566,431
2024	4,405,144
2025	4,381,270
Thereafter	7,151,280
Total undiscounted lease payments	29,363,138
Less: Imputed interest	(7,142,623)
Operating lease liability	22,220,515	$ 23,127,813
Finance Leases
2021	17,505
2022	13,129
Total undiscounted lease payments	30,634
Less: Imputed interest	(2,309)
Finance lease liability	$ 28,325	$ 50,737

Commitments - Additional Inform

Commitments - Additional Information (Details)

Jun. 07, 2018$ / sharesshares

Dec. 05, 2016USD ($)shares

Feb. 04, 2015USD ($)Program

Feb. 04, 2015GBP (£)Program

Feb. 29, 2016USD ($)

Dec. 31, 2020USD ($)shares

Dec. 31, 2020EUR (€)shares

Dec. 31, 2019USD ($)shares

Dec. 31, 2019EUR (€)shares

Jan. 31, 2018

Dec. 31, 2020EUR (€)

Jan. 01, 2016USD ($)

Other Commitments [Line Items]

Rent expense under operating lease agreements

$ 487,555

Research and development expenses

$ 33,910,481

24,875,659

General and administrative expense

$ 44,206,921

$ 46,684,297

Ordinary share | shares

1,666,500

1,666,500

551,000

551,000

Service Agreements [Member]

Other Commitments [Line Items]

Employees aggregate compensation | €

€ 300,000

Research and development expenses

$ 1,278,425

935,958

$ 1,234,000

€ 944,500

Future obligations under agreement

164,000

€ 120,000

Employment Agreements [Member]

Other Commitments [Line Items]

Employees aggregate compensation

$ 710,000

Future obligations under agreement

2,418,750

Aggregate discretionary bonus

3,300,000

5,403,000

Employee agreement description

The employment agreements also provide for an annual guaranteed cash bonus targeted at 100% of annual compensation. The agreements also provide for discretionary annual performance bonuses targeted to be not less than 50-60% of the employee’s base salary and grants of restricted shares.

Employment agreement term

3 years

License Agreement [Member]

Other Commitments [Line Items]

Research and development expenses

273,180

4,271,275

Restricted ordinary shares subject to forfeiture [Member]

Other Commitments [Line Items]

Employees share award | shares

1,306,348

Employees share award, per share | $ / shares

$ 15

Maximum | Service Agreements [Member]

Other Commitments [Line Items]

Employees aggregate compensation

587,000

€ 430,000

Maximum | Employment Agreements [Member]

Other Commitments [Line Items]

Employees aggregate compensation

$ 1,075,000

Cornell University [Member] | Research Agreement [Member]

Other Commitments [Line Items]

Agreement amended date

Jun. 12, 2017

Research and collaboration agreement period

3 years

Ordinary share | shares

6,441

Cornell University [Member] | Issued At Closing of Merger [Member] | Research Agreement [Member]

Other Commitments [Line Items]

Research and development expenses

$ 17,000

379,478

1,756,487

UCL Business, PLC [Member] | License Agreement [Member]

Other Commitments [Line Items]

Number of collaborations programs | Program

8

8

Aggregate sales milestone payments payable

£ 39,800,000

54,400,000

Maintenance fee

$ 66,000

£ 50,000

BRI-Alzan [Member] | License Agreement [Member]

Other Commitments [Line Items]

Research and development expenses

15,000

15,000

Aggregate sales milestone payments payable

$ 4,500,000

License Agreements Effective September 7, 2018 [Member] | National Institutes of Health [Member] | License Agreement [Member]

Other Commitments [Line Items]

Research and development expenses

$ 0

$ 60,000

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Details) - USD ($)	Jan. 01, 2017	Aug. 01, 2016	Dec. 31, 2020	Dec. 31, 2019
Compensation And Retirement Disclosure [Line Items]
Defined benefit plan, plan assets, contributions by employer			$ 1,089,657	$ 604,294
United States
Compensation And Retirement Disclosure [Line Items]
Defined contribution plan, annual contributions per employee, percent	6.00%
United States | Minimum
Compensation And Retirement Disclosure [Line Items]
Defined contribution plan, employee eligibility age	21 years
U.K. | Minimum
Compensation And Retirement Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent		7.50%
U.K. | Maximum
Compensation And Retirement Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent		10.00%
Ireland
Compensation And Retirement Disclosure [Line Items]
Defined contribution plan, employer contribution exclusive of employee match, percent			4.50%

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - Subsequent Event - Visiogene LLC $ in Millions	Jan. 04, 2021USD ($)shares
Subsequent Event [Line Items]
Cash consideration | $	$ 5
Number of ordinary shares | shares	75,000