MeiraGTx (MGTX) 10-Q 7 Nov 19 2019 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2019	Oct. 31, 2019
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Interactive Data Current	Yes
Trading Symbol	MGTX
Entity Registrant Name	MeiraGTx Holdings plc
Entity Central Index Key	0001735438
Current Fiscal Year End Date	--12-31
Entity Shell Company	false
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		36,571,722
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Current Reporting Status	Yes
Entity Address, State or Province	NY
Title of 12(b) Security	Ordinary Shares
Security Exchange Name	NASDAQ

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)	Sep. 30, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 253,330,623	$ 68,080,175
Prepaid expenses	6,248,981	1,937,785
Other current assets	11,509,144	4,634,105
Total Current Assets	271,088,748	74,652,065
Right-of-use assets	28,801,757
Property and equipment, net	16,899,147	22,014,237
Security deposits	839,149	105,085
Restricted cash	123,376	123,376
TOTAL ASSETS	317,752,177	96,894,763
CURRENT LIABILITIES:
Accounts payable	3,798,441	3,042,861
Accrued expenses	9,346,895	11,991,697
Lease obligations, current	2,028,689	27,199
Deferred revenue - related party, current	24,115,777
Other current liabilities		437,053
Total Current Liabilities	39,289,802	15,498,810
Deferred revenue - related party	62,837,715
Lease obligations	20,600,077	7,097
Deferred rent		201,264
Asset retirement obligations	131,213	128,119
TOTAL LIABILITIES	122,858,807	15,835,290
COMMITMENTS
SHAREHOLDERS' EQUITY:
Ordinary Shares, $0.00003881 par value, 1,288,327,750 authorized 36,571,722 issued and outstanding at September 30, 2019 27,386,632 issued and outstanding at December 31, 2018	1,420	1,064
Capital in excess of par value	390,053,479	229,054,460
Accumulated other comprehensive income	2,393,372	293,666
Accumulated deficit	(197,554,901)	(148,289,717)
Total Shareholders' Equity	194,893,370	81,059,473
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 317,752,177	$ 96,894,763

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
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	36,571,722	27,386,632
Common stock, shares outstanding	36,571,722	27,386,632

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
License revenue - related party	$ 3,582,586		$ 6,349,222
Operating expenses:
General and administrative	9,874,810	$ 6,629,052	31,811,456	$ 35,129,120
Research and development	4,614,446	8,109,160	27,362,432	22,827,176
Total operating expenses	14,489,256	14,738,212	59,173,888	57,956,296
Loss from operations	(10,906,670)	(14,738,212)	(52,824,666)	(57,956,296)
Other non-operating income (expense):
Foreign currency gain (loss)	115,470	(677,488)	3,117,047	(2,425,488)
Change in fair value of warrant liability				(1,514,775)
Other income				83,075
Interest income	959	264	40,686	50,926
Interest expense	(9,283)	(9,508)	(28,311)	(46,571)
Loss before income taxes	(10,799,524)	(15,424,944)	(49,695,244)	(61,809,129)
Benefit for income taxes	338,670	0	430,060	0
Net loss	(10,460,854)	(15,424,944)	(49,265,184)	(61,809,129)
Other comprehensive income:
Foreign currency translation, net of tax of $338,670 and $0 for the three-month periods ended September 30, 2019 and 2018, respectively and $430,060 and $0 for the nine-month periods ended September 30, 2019 and 2018, respectively	1,653,507	508,758	2,099,706	1,730,000
Total comprehensive loss	(8,807,347)	(14,916,186)	(47,165,478)	(60,079,129)
Net loss	(10,460,854)	(15,424,944)	(49,265,184)	(61,809,129)
Accretion on convertible preferred C shares and warrants				(1,806,512)
Adjusted net loss	$ (10,460,854)	$ (15,424,944)	$ (49,265,184)	$ (63,615,641)
Basic and diluted adjusted net loss per ordinary share	$ (0.30)	$ (0.59)	$ (1.53)	$ (3.89)
Weighted-average number of ordinary shares outstanding	34,663,623	26,340,450	32,111,733	16,355,849

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Parenthetical) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Foreign currency translation, tax	$ 338,670	$ 0	$ 430,060	$ 0

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS EQUITY	USD ($)shares	LicenseAgreement [Member]USD ($)shares	LicenseAgreement [Member]GBP (£)shares	Private Placement [Member]USD ($)	Public Placement [Member]USD ($)	Ordinary shares [Member]USD ($)shares	Ordinary shares [Member]Private Placement [Member]USD ($)shares	Ordinary shares [Member]Public Placement [Member]USD ($)shares	Capital in Excess of Par Value [Member]USD ($)	Capital in Excess of Par Value [Member]Private Placement [Member]USD ($)	Capital in Excess of Par Value [Member]Public Placement [Member]USD ($)	Accumulated Other Comprehensive Income (Loss) [Member]USD ($)	Accumulated Deficit [Member]USD ($)	A Ordinary Shares [Member]USD ($)shares	Convertible Preferred C Shares [Member]USD ($)shares	Convertible Preferred C Shares [Member]Accounts Payable [Member]USD ($)shares	Convertible Preferred C Shares [Member]LicenseAgreement [Member]USD ($)shares	Convertible Preferred C Shares [Member]SalesAgreement [Member]USD ($)shares
Temporary equity, ending Balance at Dec. 31, 2017															$ 51,338,631
Temporary equity, ending Balance, Shares at Dec. 31, 2017 | shares															5,005,935
Beginning Balance at Dec. 31, 2017	$ (47,365,265)								$ 20,080,713			$ (2,022,477)	$ (65,423,843)	$ 342
Beginning Balance, Shares at Dec. 31, 2017 | shares														8,826,190
Accretion of warrants issued in connection with convertible preferred C shares	(570,273)								(570,273)						$ 570,273
Issuance of convertible preferred C shares, net of issuance costs																$ 1,356,129	$ 140,000	$ 43,851,602
Sale of ordinary shares in connection with private placement and public offering, net of issuance costs, Shares | shares																129,419	13,360	4,212,453
Accretion of warrants issued in connection with convertible preferred C shares	(94,445)								(94,445)						94,445
Share-based compensation	4,275,735								4,275,713					$ 22
Share-based compensation, Shares | shares														550,162
Foreign currency translation, net of income taxes	(757,765)											(757,765)
Net loss	(16,403,353)												(16,403,353)
Ending Balance at Mar. 31, 2018	(60,915,366)								23,691,708			(2,780,242)	(81,827,196)	$ 364	$ 97,351,080
Ending Balance, Shares at Mar. 31, 2018 | shares														9,376,352	9,361,167
Temporary equity, ending Balance at Dec. 31, 2017															$ 51,338,631
Temporary equity, ending Balance, Shares at Dec. 31, 2017 | shares															5,005,935
Beginning Balance at Dec. 31, 2017	(47,365,265)								20,080,713			(2,022,477)	(65,423,843)	$ 342
Beginning Balance, Shares at Dec. 31, 2017 | shares														8,826,190
Foreign currency translation, net of income taxes	1,730,000
Net loss	(61,809,129)
Ending Balance at Sep. 30, 2018	96,344,071								223,868,465			(292,477)	(127,232,972)	$ 1,055	$ 0
Ending Balance, Shares at Sep. 30, 2018 | shares														27,184,132	0
Beginning Balance at Mar. 31, 2018	(60,915,366)								23,691,708			(2,780,242)	(81,827,196)	$ 364	$ 97,351,080
Beginning Balance, Shares at Mar. 31, 2018 | shares														9,376,352	9,361,167
Sale of convertible preferred C shares, net of issuance costs															$ 12,307,517
Sale of convertible preferred C shares, net of issuance costs, Shares | shares															1,212,671
Sale of ordinary shares in connection with private placement and public offering, net of issuance costs	65,458,470								65,458,276					$ 194
Sale of ordinary shares in connection with private placement and public offering, net of issuance costs, Shares | shares														5,000,000
Conversion of convertible preferred C shares into A ordinary shares	120,520,391								120,519,945					$ 446	$ (120,520,391)
Conversion of convertible preferred C shares into A ordinary shares, shares | shares														11,501,432	(11,501,432)
Exercise of warrants	4,194,408								4,194,408						$ 9,720,000
Exercise of warrants, Share | shares															927,594
Accretion of warrants issued in connection with convertible preferred C shares	(666,567)								(666,567)						$ 666,567
Accretion of warrants issued in connection with convertible preferred C shares	(475,227)								(475,227)						475,227
Share-based compensation	8,357,821								8,357,770					$ 51
Share-based compensation, Shares | shares														1,306,348
Foreign currency translation, net of income taxes	1,979,007											1,979,007
Net loss	(29,980,832)												(29,980,832)
Ending Balance at Jun. 30, 2018	108,472,105								221,080,313			(801,235)	(111,808,028)	$ 1,055	$ 0
Ending Balance, Shares at Jun. 30, 2018 | shares														27,184,132	0
Additional issuance costs in connection with A ordinary shares issued	(134,205)								(134,205)
Share-based compensation	2,922,357								2,922,357
Foreign currency translation, net of income taxes	508,758											508,758
Net loss	(15,424,944)												(15,424,944)
Ending Balance at Sep. 30, 2018	96,344,071								223,868,465			(292,477)	(127,232,972)	$ 1,055	$ 0
Ending Balance, Shares at Sep. 30, 2018 | shares														27,184,132	0
Beginning Balance at Dec. 31, 2018	81,059,473					$ 1,064			229,054,460			293,666	(148,289,717)
Beginning Balance, Shares at Dec. 31, 2018 | shares						27,386,632
Issuance of ordinary shares in connection with a license agreement	1,966,340					$ 6			1,966,334
Issuance of ordinary shares in connection with a license agreement, shares | shares						158,832
Sale of ordinary shares in connection with private placement and public offering, net of issuance costs				$ 77,573,047			$ 225			$ 77,572,822
Sale of ordinary shares in connection with private placement and public offering, net of issuance costs, Shares | shares							5,797,102
Share-based compensation	2,934,991								2,934,991
Foreign currency translation, net of income taxes	(1,133,683)											(1,133,683)
Net loss	(17,981,918)												(17,981,918)
Ending Balance at Mar. 31, 2019	$ 144,418,250					$ 1,295			311,528,607			(840,017)	(166,271,635)
Ending Balance, Shares at Mar. 31, 2019 | shares	33,342,566
Beginning Balance at Dec. 31, 2018	$ 81,059,473					$ 1,064			229,054,460			293,666	(148,289,717)
Beginning Balance, Shares at Dec. 31, 2018 | shares						27,386,632
Issuance of ordinary shares in connection with a license agreement		$ 1,966,000	£ 1,500,000
Exercised stock options, shares | shares	9,349
Issuance of ordinary shares in connection with a license agreement, shares | shares		158,832	158,832			158,832
Foreign currency translation, net of income taxes	$ 2,099,706
Net loss	(49,265,184)
Ending Balance at Sep. 30, 2019	$ 194,893,370					$ 1,420			390,053,479			2,393,372	(197,554,901)
Ending Balance, Shares at Sep. 30, 2019 | shares	36,571,722
Beginning Balance at Mar. 31, 2019	$ 144,418,250					$ 1,295			311,528,607			(840,017)	(166,271,635)
Beginning Balance, Shares at Mar. 31, 2019 | shares	33,342,566
Exercised stock options	$ 1,267								1,267
Exercised stock options, shares | shares						225
Share-based compensation	4,386,123								4,386,123
Foreign currency translation, net of income taxes	1,579,882											1,579,882
Net loss	(20,822,412)												(20,822,412)
Ending Balance at Jun. 30, 2019	129,563,110					$ 1,295			315,915,997			739,865	(187,094,047)
Ending Balance, Shares at Jun. 30, 2019 | shares						33,342,791
Exercised stock options	53,344								53,344
Exercised stock options, shares | shares						9,124
Sale of ordinary shares in connection with private placement and public offering, net of issuance costs					$ 70,157,212			$ 124			$ 70,157,088
Sale of ordinary shares in connection with private placement and public offering, net of issuance costs, Shares | shares								3,200,000
Issuance of ordinary shares in connection with payables	421,500					$ 1			421,499
Issuance of ordinary shares in connection with payables (shares) | shares						19,807
Share-based compensation	3,505,551								3,505,551
Foreign currency translation, net of income taxes	1,653,507											1,653,507
Net loss	(10,460,854)												(10,460,854)
Ending Balance at Sep. 30, 2019	$ 194,893,370					$ 1,420			$ 390,053,479			$ 2,393,372	$ (197,554,901)
Ending Balance, Shares at Sep. 30, 2019 | shares	36,571,722

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS EQUITY (Parenthetical) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Foreign currency translation, net of income tax	$ 338,670		$ 0
Private Placement [Member]
Payments of Stock Issuance Costs		$ 2,426,953
Public Placement [Member]
Payments of Stock Issuance Costs	$ 5,042,795
IPO [Member]
Payments of Stock Issuance Costs			$ 9,541,530

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Cash flows from operating activities:
Net loss			$ (49,265,184)	$ (61,809,129)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Ordinary shares issued in connection with license agreements			1,966,340	137,658
Share-based compensation expense			10,826,665	15,555,913
Foreign currency (gain) loss	$ (115,470)	$ 677,488	(3,117,047)	2,425,488
Depreciation			1,569,098	1,549,686
Amortization of interest on asset retirement obligation			7,861	10,918	$ (38,301)
Change in fair value of warrant liability				1,514,775
Benefit for income taxes			(430,060)
(Increase) decrease in operating assets:
Prepaid expenses			(4,413,356)	(112,440)
Other current assets			(6,358,738)	239,627
Security deposits			(745,275)	(180,980)
Increase (decrease) in operating liabilities:
Accounts payable			1,415,012	(2,337,302)
Accrued expenses			(2,428,405)	(3,496,882)
Other current liabilities			(436,161)
Due to Kadmon				(861,030)
Deferred revenue			93,120,824
Lease obligations			304,713
Deferred rent				(55,460)
Net cash provided by (used in) operating activities			42,016,287	(47,419,158)
Cash flows from investing activities:
Purchase of property and equipment			(4,230,740)	(2,372,622)
Net cash used in investing activities			(4,230,740)	(2,372,622)
Cash flows from financing activities:
Payments on lease obligations - financing leases			(17,923)	(23,772)
Exercise of warrants				9,720,000
Exercise of share options			54,611
Proceeds from the sale of ordinary shares			155,200,007	69,750,000
Payment of note payable				(1,442,009)
Net cash provided by financing activities			147,766,947	130,047,495
Net increase in cash, cash equivalents and restricted cash			185,552,494	80,255,715
Effect of exchange rate changes on cash			(302,046)	(243,719)
Cash, cash equivalents and restricted cash at beginning of period			68,203,551	8,672,014	8,672,014
Cash, cash equivalents and restricted cash at end of period	$ 253,453,999	$ 88,684,010	253,453,999	88,684,010	$ 68,203,551
Supplemental disclosure of non-cash transactions:
Lease obligations for right-of-use asset			22,932,582
Issuance of shares in connection with payables			421,500	1,356,129
Reclassification of warrant liability upon exercise of warrants				4,194,408
Supplemental disclosure of cash flow information:
Cash paid for interest			1,219	31,531
Ordinary shares [Member]
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Share-based compensation expense				6,456,215
Cash flows from financing activities:
Issuance costs in connection			$ (7,469,748)	(4,115,843)
Supplemental disclosure of non-cash transactions:
Issuance costs in connection with sale				309,892
Convertible Preferred C Shares [Member]
Cash flows from financing activities:
Issuance costs in connection				(690,475)
Proceeds from the sale of convertible preferred C shares, net of issuance costs				56,849,594
Supplemental disclosure of non-cash transactions:
Conversion of convertible preferred C shares into ordinary shares				$ 120,520,391

Organization and Basis of Prese

Organization and Basis of Presentation	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Organization and Basis of Presentation	1. Organization and Basis of Presentation: The Company MeiraGTx Holdings plc and subsidiaries (the “Company” or “Meira Holdings”), an exempted company incorporated under the laws of the Cayman Islands, is a clinical-stage biotech company developing novel gene therapy treatments for a wide range of inherited and acquired disorders for which there are few or no effective treatments available. The Company is focused on developing therapies for ocular diseases, including inherited retinal d iseases Basis of Presentation The accompanying condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Interim Financial Statements The accompanying condensed consolidated financial statements have been prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q Regulation S-X. Form 10-K “Form 10-K”). Liquidity The Company has not yet achieved profitable operations. There is no assurance that profitable operations, if ever achieved, could be sustained on a continuing basis. In addition, development activities, clinical and preclinical testing, and commercialization of the Company’s product candidates will require significant additional financing. The Company’s accumulated deficit at September 30, 2019 totaled $197,554,901, and management expects to incur substantial losses in future periods. The success of the Company is subject to certain risks and uncertainties, including among others, uncertainty of product development; competition in the Company’s field of use; uncertainty of capital availability; uncertainty in the Company’s ability to enter into agreements with collaborative partners; dependence on third parties; and dependence on key personnel. For the nine-months ended September 30, 2019, the Company generated $42,016,287 of positive cash flows from operations. However, prior to the nine-months ended September 30, 2019, the Company did not generate positive 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 September 30, 2019, the Company had cash and cash equivalents in the amount of $253,330,623, 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”). Under the terms of the Collaboration Agreement, the Company received an upfront payment of $100,000,000. The Company will also receive 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 September 30, 2019 will be sufficient to cover its expenses for at least the next twelve months from the date of issuance of these condensed consolidated financial statements. Risks and Uncertainties The Company operates in an industry that is subject to intense competition, government regulation and rapid technological change. The Company’s operations are subject to significant risk and uncertainties including financial, operational, technological, regulatory and other risks, including the potential risk of business failure. The Company’s capital resources and operations to date have been funded primarily with the proceeds from the Collaboration Agreement, private and public equity offerings and the IPO. 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.

Summary of Significant Accounti

Summary of Significant Accounting Policies and Recent Accounting Pronouncements	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies and Recent Accounting Pronouncements	2. Summary of Significant Accounting Policies and Recent Accounting Pronouncements: Certain of the Company’s significant accounting policies are described below. All of the Company’s significant accounting policies are disclosed in the notes to the audited consolidated financial statements as of and for the year ended December 31, 2018 included in the Company’s Form 10-K. Since Consolidation The accompanying condensed consolidated financial statements include the accounts of Meira Holdings and its wholly owned subsidiaries: MeiraGTx Limited, a limited company under the laws of England and Wales; MeiraGTx, LLC, a Delaware corporation; MeiraGTx UK II Limited, a limited company under the laws of England and Wales (“Meira UK II”); BRI-Alzan, MeiraGTx B.V., a Netherlands corporation; MeiraGTx Neurosciences, Inc., a Delaware corporation; and MeiraGTx UK Limited, a limited company under the laws of England and Wales. All intercompany balances and transactions between the consolidated companies have been eliminated in consolidation. Use of Estimates Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these condensed consolidated financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. This process may result in actual results differing materially from those estimated amounts used in the preparation of the financial statements if these results differ from historical experience, or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made. In preparing these condensed consolidated financial statements, management used significant estimates in the following areas, among others: collaboration revenue (as disclosed in Note 8), the accounting for research and development costs, warrants, share-based compensation, leases and accrued expenses. 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 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: Description September 30, Significant Significant Other Significant Restricted cash $ 123,376 $ 123,376 $ — $ — Asset retirement obligations $ 131,213 $ — $ — $ 131,213 Fair Value Measurement Using: Description December 31, Significant Significant Other Significant Restricted cash $ 123,376 $ 123,376 $ — $ — Asset retirement obligations $ 128,119 $ — $ — $ 128,119 Net Loss per Ordinary Share Basic net loss per ordinary share is computed by dividing net loss by the weighted average number of shares of the Company’s ordinary shares assumed to be outstanding during the period of computation. Diluted net loss per ordinary share is computed similar to basic net loss per share except that the denominator is increased to include the number of additional ordinary shares that would have been outstanding if the potential ordinary shares had been issued at the beginning of the year and if the additional ordinary shares were dilutive (treasury stock method) or the two-class Asset Retirement Obligations Accounting for asset retirement obligations requires legal obligations associated with the retirement of long-lived assets to be recognized at fair value when incurred and capitalized as part of the related long-lived asset. In the absence of quoted market prices, the Company estimates the fair value of its asset retirement obligations using Level 3 present value techniques, in which estimates of future cash flows associated with retirement activities are discounted using a credit-adjusted risk-free rate. Asset retirement obligations currently reported as other liabilities on the Condensed Consolidated Balance Sheet were measured during a period of historically low interest rates. The impact on measurements of new asset retirement obligations using different rates in the future may be significant. The Company uses estimates to determine the asset retirement obligations at the end of the lease term and discounts such asset retirement obligations using an estimated discount rate. Interest on the discounted asset retirement obligation is amortized over the term of the lease using the effective interest method and is recorded as interest expense in the condensed consolidated statements of operations and comprehensive loss. The change in asset retirement obligations is as follows: September 30, 2019 December 31, 2018 Balance at beginning of period $ 128,119 $ 178,419 Additional asset retirement obligations during the period — 69,286 Amortization of interest 7,861 (38,301 ) Change in estimate — (99,090 ) Effects of exchange rate (4,767 ) 17,805 Balance at end of period $ 131,213 $ 128,119 Research and Development Research and development costs are charged to expense as incurred. These costs include, but are not limited to, employee-related expenses, including salaries, benefits and travel of the Company’s research and development personnel; expenses incurred under agreements with contract research organizations and investigative sites that conduct clinical and preclinical studies and for the drug product for the clinical studies and preclinical activities; facilities; supplies; rent, insurance, certain legal fees, share-based compensation, depreciation and other costs associated with clinical and preclinical activities and regulatory operations. Research funding under collaboration agreements is recorded as an offset to these costs. Costs for certain development activities, such as Company funded outside research programs, are recognized based on an evaluation of the progress to completion of specific tasks with respect to their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the condensed consolidated financial statements as prepaid expenses or accrued expenses, as the case may be. Collaboration Arrangements The Company evaluates its collaborative arrangements pursuant to ASC 808, Collaborative Arrangements Revenue from Contracts with Customers ASC 808 does not address recognition or measurement matters related to collaborative arrangements. Payments between participants pursuant to a collaborative arrangement that are within the scope of other authoritative accounting literature on income statement classification are accounted for using the relevant provisions of that literature. If the payments are not within the scope of other authoritative accounting literature, the income statement classification for the payments is based on an analogy to authoritative accounting literature or if there is no appropriate analogy, a reasonable, rational and consistently applied accounting policy election. Payments received from a collaboration partner to which this policy applies may include upfront payments in respect of a license of intellectual property, development and commercialization-based milestones, and royalties. Refer to the discussion in Note 8 for further information related to the accounting for the Janssen Collaboration Agreement. Revenue Recognition Arrangements with collaborators may include licenses to intellectual property, research and development services, manufacturing services for clinical and commercial supply, and participation on joint steering committees. The Company evaluates the promised goods or services to determine which promises, or group of promises, represent performance obligations. In contemplation of whether a promised good or service meets the criteria required of a performance obligation, the Company considers the stage of development of the underlying intellectual property, the capabilities and expertise of the customer relative to the underlying intellectual property, and whether the promised goods or services are integral to or dependent on other promises in the contract. When accounting for an arrangement that contains multiple performance obligations, the Company must develop judgmental assumptions, which may include market conditions, reimbursement rates for personnel costs, development timelines and probabilities of regulatory success to determine the stand-alone selling price for each performance obligation identified in the contract. When the Company concludes that a contract should be accounted for as a combined performance obligation and recognized over time, the Company must then determine the period over which revenue should be recognized and the method by which to measure revenue. The Company generally recognizes revenue using a cost-based input method. The Collaboration Agreement with Janssen is accounted for under ASC 808, however, as ASC 808 does not address recognition or measurement matters such as determining the appropriate unit of accounting or when the recognition criteria are met, the Company accounts for the consideration received from Janssen in accordance with ASC 606. it performs the following five steps: i. identify the contract(s) with a customer; ii. identify the performance obligations in the contract; iii. determine the transaction price; iv. allocate the transaction price to the performance obligations within the contract; and v. recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it determines that it is probable it will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be by analogy within the scope of ASC 606, the Company assesses the goods or services promised within the contract to determine whether each promised good or service is a performance obligation. The promised goods or services in the Company’s arrangements typically consist of a license to the Company’s intellectual property and research, development and manufacturing services. The Company may provide options to additional items in such arrangements, which are accounted for as separate contracts when the customer elects to exercise such options, unless the option provides a material right to the customer. Performance obligations are promises in a contract to transfer a distinct good or service to the customer that (i) the customer can benefit from on its own or together with other readily available resources, and (ii) is separately identifiable from other promises in the contract. Goods or services that are not individually distinct performance obligations are combined with other promised goods or services until such combined group of promises meet the requirements of a performance obligation. The Company determines transaction price based on the amount of consideration the Company expects to receive for transferring the promised goods or services in the contract. Consideration may be fixed, variable, or a combination of both. At contract inception for arrangements that include variable consideration, the Company estimates the probability and extent of consideration it expects to receive under the contract utilizing either the most likely amount method or expected amount method, whichever best estimates the amount expected to be received. The Company then considers any constraints on the variable consideration and includes in the transaction price variable consideration to the extent it is deemed probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. The Company then allocates the transaction price to each performance obligation based on the relative standalone selling price and recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) control is transferred to the customer and the performance obligation is satisfied. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company records amounts as accounts receivable when the right to consideration is deemed unconditional. When consideration is received, or such consideration is unconditionally due, from a customer prior to transferring goods or services to the customer under the terms of a contract, a contract liability is recorded as deferred revenue. Amounts received prior to satisfying the revenue recognition criteria are recognized as deferred revenue in the Company’s condensed consolidated balance sheet. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue – related party, current. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue – related party. The Company’s collaboration revenue arrangements include the following: Up-front up-front non-refundable, up-front 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 will record costs associated with the development activities as research and development expenses in the condensed consolidated statement of operations and comprehensive loss consistent with ASC 730, Research and Development 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 License and Collaboration Agreement are generated in the United Kingdom. The following table summarizes non-current September 30, 2019 December 31, 2018 United States $ 13,390,438 $ 454,568 United Kingdom 33,272,991 21,788,130 $ 46,663,429 $ 22,242,698 Accounting Pronouncements Recently Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases 2016-02”). right-of-use initi al right-of-use No. 2018-10, 2016-02 No. 2018-11, 2016-02 right-of-use In October 2016, the FASB issued ASU 2016-16, Income Intra-Entity Transfers of Assets Other than Inventory ASU 2016-16, which ASU 2016-16 did In July 2019, the FASB issued ASU 2019-07, Codification Updates to SEC Sections—Amendments to SEC Paragraphs Pursuant to SEC Final Rule Releases No. 33-10532, 33-10231 33-10442, 2019-07 2019-07 2019-07, 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 held-to-maturity 2016-13 available-for-sale In , the FASB issued ASU 2018-13, Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurements , which changes the fair value measurement disclosure requirements of ASC . The goal of the ASU is to improve the effectiveness of ASC ’s disclosure requirements by providing users of the financial statements with better information about assets and liabilities measured at fair value in the financial statements and notes thereto. The guidance is applicable for fiscal years beginning after December , and interim periods within those years. The Company is currently evaluating the potential impact of the adoption of this standard on its related disclosures. In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808) : Clarifying the Interaction between Topic 808 and Topic 606 2018-18”). 2018-18 are 2018-18,

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2019
Payables and Accruals [Abstract]
Accrued Expenses	3. Accrued Expenses Accrued expenses for the periods presented are comprised of the following: September 30, 2019 December 31, 2018 Clinical Trial Costs $ 5,509,493 $ 4,013,094 Compensation and Benefits 1,216,081 5,731,438 Consulting 1,049,451 821,009 Professional Fees 719,222 914,540 Manufacturing Costs 146,160 — Rent 94,688 122,770 Interest 60,032 40,800 Research and Development 8,145 236,271 Other 543,623 111,775 $ 9,346,895 $ 11,991,697

Share-Based Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	4. Share-Based Compensation 2018 Incentive Award Plan and 2016 Equity Incentive Plan 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 to selected officers, employees and non-employee A summary of the Company’s share option activity related to employees, non-employee non-employee nine -month Number of Options Weighted- Aggregate Outstanding at December 31, 2018 3,254,365 $ 7.64 $ 6,903,313 Granted 500,000 18.44 Exercised (9,349 ) (5.84 ) Forfeited (21,319 ) (9.39 ) Outstanding at September 30, 2019 3,723,697 $ 9.08 $ 26,795,585 Weighted average remaining contractual life of options 9.24 Weighted average remaining contractual life of options 8.60 Options exercisable at December 31, 2018 535,241 $ 5.79 Options exercisable at September 30, 2019 1,098,211 $ 6.11 Weighted average remaining contractual life of options 7.88 Weighted average remaining contractual life of options 7.52 The total fair value of options vested during the three-month periods ended September 30, 2019 and 2018 was $429,647 and $503,828, respectively. The total fair value of options vested during the nine-month periods ended September 30, 2019 and 2018 was $2,718,315 and $1,060,177, respectively. During the three-month periods ended September 30, 2019 and 2018, the Company granted 195,000 and 0 share options, respectively. During the nine-month periods ended September 30, 2019 and 2018, the Company granted 500,000 and 695,685 share options, 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: 2019 2018 Risk-free interest rate 2.03 - 2.55% 2.32% - 2.84% Expected volatility 90% 90% Expected dividend yield 0% 0% Expected life (in years) 6.1 5.5 - 9.5 As of September 30, 2019, the total compensation expense relating to unvested options granted that had not yet been recognized was $18,626,465, which is expected to be realized over a period of 3.75 years. The Company will issue shares upon exercise of options from ordinary shares reserved. The weighted-average grant date fair value of options granted during the nine-month periods ended September 30, 2019 and 2018 was $13.86 and $4.46, respectively. Restricted Ordinary Shares In 2015, in connection with certain service and consulting agreements, certain employees and a consultant were awarded an aggregate of 867,935 restricted ordinary shares of the Company. Such shares were subject to forfeiture over a three-year service period. The shares granted to the consultant and employees were valued at $7.72 and $7.76 per share, respectively, and the related share-based compensation expense was included in loss from operations over the requisite service period. As of September 30, 2019, all such shares are no longer subject to forfeiture as the three-year service period has been completed. 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 S-1 Total compensation expense in connection with the issuance of those restricted ordinary shares, in the amount of $5,587,546 and $3,405,274, of which $3,265,872 and $1,992,182 was share-based, was recorded as general and administrative expense during the three-month periods ended September 30, 2019 and 2018, respectively. Total compensation expense in connection with the issuance of those restricted ordinary shares, in the amount of $11,840,200 and $17,026,140, of which $4,898,808 and $8,523,932 was share-based, was recorded as general and administrative expense during the nine-month periods ended September 30, 2019 and 2018, respectively. A summary of the restricted ordinary shares is as follows: Ordinary Shares $ Value Non-vested 653,174 $ 9,797,610 Vested during nine-month period ended September 30, 2019 (326,586 ) (4,898,790 ) Non-vested 326,588 $ 4,898,820 Ordinary Shares On March 1, 2018, a funding milestone was met under the employment agreements for certain members of senior management. Accordingly, the employees were issued an aggregate of 550,162 fully vested ordinary shares, which represented 3% of the fully-diluted outstanding shares of the Company as of such date. The shares were recorded as share-based compensation in the amount of $3,096,104. Additionally, under the terms of the employment agreements, the Company was required to pay the income taxes incurred by the grantees in connection with the grant of those shares. Total compensation expense in connection with the issuance of those ordinary shares, in the amount of $6,456,215, of which $3,096,104 was share-based, was recorded as general and administrative expense during the nine-month period ended September 30, 2018. During the three-month and nine-month periods ended September 30, 2019 and 2018 the Company recognized total share-based compensation expense in the accompanying condensed consolidated statements of operations and comprehensive loss as follows: Three-month periods ended September 30, 2019 2018 Research and development $ 1,131,659 $ 1,040,499 General and administrative 2,373,892 1,881,858 Total share based compensation $ 3,505,551 $ 2,922,357 Nine-month periods ended September 30, 2019 2018 Research and development $ 2,828,944 $ 2,931,010 General and administrative 7,997,721 12,624,903 Total share based compensation $ 10,826,665 $ 15,555,913 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 three-month and nine-month periods ended September 30, 2019 and 2018.

Ordinary Shares

Ordinary Shares	9 Months Ended
	Sep. 30, 2019
Federal Home Loan Banks [Abstract]
Ordinary Shares	5. Ordinary Shares Private Placement On February 27, 2019, the Company issued 5,797,102 ordinary shares in a private placement for gross proceeds of $80 million, excluding offering costs of approximately $2.4 million. Johnson & Johnson Innovation – JJDC, Inc. (“JJDC”), the investment arm of Johnson and Johnson and owner of Janssen , purchased 2,898,550 of the ordinary shares issued on the same terms and conditions as the other investors in the offering. In connection with the offering, the Company also entered into a registration rights agreement whereby, promptly following the date on which the Company becomes eligible to use a registration statement on Form S-3, S-3 S-3 Public Offering On August 7, 2019, the Company issued 3,200,000 75 5.1 License Agreement As discussed in Note 8, on March 21, 2019, the Company issued 158,832 ordinary shares in connection with a license agreement. In accordance with the license agreement, the cost basis of the shares was based on the closing share price on January 31, 2019.

Net Loss per Ordinary Share

Net Loss per Ordinary Share	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Loss per Share	6. Net Loss per Ordinary The Company computes net loss per share in accordance with ASC 260-10, Earnings per Share Basic and diluted net loss per ordinary share is computed as follows: Three-month periods ended 2019 2018 Net loss - basic and diluted $ (10,460,854 ) $ (15,424,944 ) Weighted-average ordinary shares outstanding: Basic and Diluted 34,663,623 26,340,450 Net loss per share: Basic and Diluted $ (0.30 ) $ (0.59 ) Nine-month periods ended 2019 2018 Net loss - basic and diluted $ (49,265,184 ) $ (61,809,129 ) Accretion of Preferred Shares financing costs — (761,012 ) Accretion of warrant — (1,045,500 ) Adjusted net loss - basic and diluted $ (49,265,184 ) $ (63,615,641 ) Weighted-average ordinary shares outstanding: Basic and Diluted 32,111,733 16,355,849 Adjusted net loss per ordinary share: Basic and Diluted $ (1.53 ) $ (3.89 ) 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: September 30, September 30, Restricted ordinary shares subject to forfeiture 326,588 762,036 Share options 3,723,697 1,629,687 4,050,285 2,391,723

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	7. Income Taxes The Company did not record a provision for income taxes for the three-month and nine-month periods ended September 30, 2019 and 2018, as the Company has generated losses for all periods. The Company periodically evaluates the realizability of its net deferred tax assets based on all available evidence, both positive and negative. The realization of net deferred tax assets is dependent on the Company’s ability to generate sufficient future taxable income during periods prior to the expiration of tax attributes to fully utilize these assets. The Company weighed both positive and negative evidence and determined that there is a continued need for a full valuation allowance on its deferred tax assets in the United States and United Kingdom as of September 30, 2019. Should the Company determine that it would be able to realize its remaining deferred tax assets in the foreseeable future, an adjustment to its remaining deferred tax assets would cause a material increase to income in the period such determination is made. The intraperiod tax allocation guidance requires that we allocate income taxes between continuing operations and other categories of earnings. When we have a year-to-date pre-tax year-to-date pre-tax 740-20-45-7)

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2019
Related Party Transactions [Abstract]
Related Party Transactions	8. Related Party Transactions Collaboration and License Agreements Janssen Pharmaceuticals, Inc. On January 30, 2019, the Company entered into a Collaboration Agreement with Janssen for the research, development and commercialization of gene therapies for the treatment of inherited retinal diseases (“IRD”). Under the agreement, Janssen paid the Company a non-refundable 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 Unless terminated earlier under certain termination clauses, the Collaboration Agreement will continue in effect, on a product-by-product country-by-country non-refundable On February 27, 2019, in connection with a private placement, the Company issued 2,898,550 ordinary shares to JJDC, the investment arm of Johnson and Johnson and owner of Janssen, on the same terms and conditions as the other investors in the offering. After the offering, JJDC became a related party. Clinical IRD Product Candidates Under the Collaboration Agreement, the Company and Janssen will jointly develop Clinical IRD Product Candidates to permit Janssen to commercialize such Clinical IRD Product Candidates under an exclusive license from the Company. In general, the Company will have the primary responsibility to develop each Clinical IRD Product Candidate in accordance with the development plan for each Clinical IRD Product Candidate, including where applicable, conducting any necessary research in order to submit the applicable regulatory filings to regulatory authorities. The Company will manufacture these products in its cGMP manufacturing facility for both clinical and commercial supply. Janssen will pay 100% of the clinical and commercialization costs of the products and the Company is eligible to receive untiered 20% royalties on net sales of products and additional development and commercialization milestones up to $340.0 million. Research IRD Product Candidates Under the Collaboration Agreement, the Company and Janssen will collaborate to develop Research IRD Product Candidates, with Janssen paying for the majority of the research costs. Janssen has the right to exclusively license any product coming out of the collaboration at the time of an investigational new drug application (“IND”) for an additional fee for each Research IRD Product Candidate. Janssen will then pay 100% of the clinical and commercialization costs for these Research IRD Product Candidates and the Company will receive an untiered royalty on net sales in the high teens as well as development milestones for each Research IRD Product Candidate. Revenue Recognition under the Collaboration Agreement The Collaboration Agreement is accounted for under ASC 808, however, ASC 808 does not address recognition or measurement matters. Therefore, the Company will account for the recognition and measurement of consideration under ASC 606. In determining the appropriate amount of revenue to be recognized under ASC 606, the Company performed the following steps: (i) identified the promised goods or services in the contract; (ii) determined whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company evaluated the potential performance obligations in the contract, which included the exclusive license to Clinical IRD Product Candidates, the research, development and manufacturing services (“the services”), and the participation in various joint committees and determined that none of the performance obligations by themselves were distinct. Goods and services that are not distinct are bundled with other goods or services in the contract until a bundle of goods or services that is distinct is created. The services, when combined with the licenses, represent a bundle and should be accounted for as a single performance obligation due to the relevance of the services to the value of the early-stage license and the potential for the intellectual property to be significantly modified during the services period. The Company also evaluated whether or not the right to purchase exclusive option rights for specified Research IRD Product Candidates represents future performance obligations and concluded that these represent a separate buyer decision at market rates, rather than a material right performance obligation. As such, these options have been excluded from the initial allocation of transaction price and the Company will account for these options as separate contracts when and if the Janssen elects to exercise the options. Under ASC 606, the Company recognized collaboration revenue using the cost-to-cost cost-to-cost 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 During the nine months ended September 30, 2019, the Company received a $100.0 million non-refundable non-refundable cost-to-cost Riboswitch Research Collaboration Agreement On October 16, 2018, the Company entered into a Riboswitch research collaboration agreement with Janssen, to develop regulatable gene therapy treatment using the Company’s proprietary riboswitch technology. As part of the agreement, the Company will use its proprietary riboswitch technology to engineer regulatable gene therapy constructs encoding proprietary gene sequences from Janssen. Upon execution of the agreement, Janssen paid the stage 1 fee in the amount of $658,667 and such payment was recorded as deferred revenue – related party. The stage 1 fee was being amortized over the estimated research term of eight months. During the three- month and nine-month periods ended September 30, 2019, the Company amortized $0 and $444,399, respectively, 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 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. Pursuant to the agreement, UCL Consultants Limited provides pre-clinical Total research and development expenses under this agreement for the three-month periods ended September 30, 2019 and 2018 were approximately $72,000 and $137,000, respectively. Total research and development expenses under this agreement for the nine-month periods ended September 30, 2019 and 2018 were approximately $245,000 and $509,000, respectively. Future obligations, under the agreement equal £82,941, or approximately $101,931, through October 2020. The amount due to UCL under this master services agreement at September 30, 2019 and December 31, 2018 is $480,825 and $389,101, respectively, and is included in accounts payable and accrued expenses on the condensed consolidated balance sheets. License Agreement Effective February 4 5 th On January 29, 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 The Company’s obligation to pay UCL Business a share of certain sublicensing revenues, as was provided under the February 4, 2015 agreement, has been removed from each of the stand-alone agreements with respect to the IRD programs listed above. Each of the stand-alone agreements now reflects terms substantially similar to those of the February 4, 2015 agreement. Additionally, under the new stand-alone agreement related to CNGB3 the Company paid UCL Business an upfront payment of £1,500,000, or approximately $1,976,000, and issued 158,832 of the Company’s ordinary shares, which were valued at £1,500,000, or approximately $1,966,000. The Company did not incur any research and development expenses under the agreements during the three-month periods ended September 30, 2019 and 2018. The Company incurred research and development expenses under the agreements in the amount of $4,111,876, inclusive of the amendment payments of approximately $3,942,000, and $219,863 during the nine-month periods ended S eptember Leases ARE Lease Effective July 1, 2016, the Company entered into a non-cancellable (the “ ARE Lease”) ARE-East right-of-use Total rent expense under this operating lease was $121,890 and $121,888 for the three-month periods ended September 30, 2019 and 2018, respectively. Total rent expense under this operating lease was $365,666 and $365,668 for the nine-month periods ended September 30, 2019 and 2018, respectively. As of September 30, 2019, the aggregate future minimum rental payments under this lease are $1,264,493. In connection with the signing of this lease, the Company entered into a standby letter of credit agreement for $122,866, which serves as a security deposit for the premises. The standby letter of credit initially expired on July 7, 2017 , The aggregate future minimum rental payments under this lease as of September 30, 2019 for years ending December 31 are as follows: 2019 $ 136 , 2020 554,432 2021 573,837 Total future rent payments $ 1,264,493 Kadmon Lease The Company is currently leasing office space on a month-to-month During the three-month periods ended September 30, 2019 and 2018, the Company incurred rent charges from Kadmon, in the amount of $145,755 and $140,805, respectively, which are included in loss from operations. During the nine-month periods ended September 30, 2019 and 2018, the Company incurred rent charges from Kadmon, in the amount of $430,649 and $416,479, respectively, which are included in loss from operations. During the three-month periods ended September 30, 2019 and 2018, the Company made cash payments totaling $145,755 and $140,954, respectively, to Kadmon. During the nine-month periods ended September 30, 2019 and 2018, the Company made cash payments totaling $430,649 and $1,284,258, respectively, to Kadmon. The were no amounts due to Kadmon at September 30, 2019 and December 31, 2018.

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Leases	9. Leases We account for leases in accordance with ASC 842. We determine 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) we have the right to control the use of the identified asset. We account for the lease and non-lease From time to time we enter 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 we are the lessee are included in right-of-use Finance leases where we are the lessee are included in ROU assets and lease obligations on our condensed 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 we determined (1) the discount rate we use 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 our leases where we are the lessee do not provide an implicit rate, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. Our incremental borrowing rate for a lease is the rate of interest we would have to pay on a collateralized basis to borrow an amount equal to the lease payments under similar terms. We use the implicit rate when readily determinable. The lease term for all of our leases includes the non-cancellable 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 to us, or we are 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. We have 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. We recognize the lease payments associated with our short-term leases as an expense on a straight-line basis over the lease term. We adopted ASU 2016-02 2018-11, , 2018-01: Land Easement Practical Expedient New York Sublease Effective May 31, 2019, the Company entered into a non-cancelable non-related initial right-of-use right-of-use There were cash payments made under this operating lease for the three-month and nine-month periods ended September 30, 2019. Total rent expense recognized under this operating lease was $ 90,000 Tudor Street Lease Effective June 11, 2019, the Company entered into a non-cancelable non-related The Company has the right to terminate this lease on June 10, 2024 by giving the landlord notice at least six months prior to such date. If the Company does not terminate the lease on June 10, 2024, the annual rent is subject to a one-time adjustment based on the then current market conditions on June 11, 2024. As the Company does not expect to exercise its right to terminate the lease prior to the expiration date, the Company records monthly rent expense on a straight-line basis from June 11, 2019, the date the Company took possession of the leased premises, through June 10, 2029, when the lease is set to terminate. In conjunction with this operating lease, the Company recognized an initial operating lease right-of-use , which is included in right-of-use Total cash payments made under this operating lease w ere Total rent expense recognized under this operating lease was £85,200, or approximately $105,000, for the three-month period ended September 30, 2019. Provost Street Lease On May 29, 2019, Meira UK II entered into an Agreement for Lease with an unrelated third party which provided a license to lease an entire building consisting of five floors of office and laboratory space in London. The leased premises were being renovated by the landlord with such renovations being completed in September 2019. Upon completion of the landlord renovations, the Company entered into a non-cancellable operating lease, which expires on September 8, 2029. The lease provides for quarterly base rent, including a rent holiday at the commencement of the lease, plus operating expenses during the lease term. The Company has the right to terminate this lease on September 8, 2024 by giving the landlord notice at least six months prior to such date. If the Company does not terminate the lease on September 8, 2024, the annual rent is subject to a one-time adjustment based on the then current market conditions on September 9, 2024. As the Company does not expect to exercise its right to terminate the lease prior to the expiration date, the Company records monthly rent expense on a straight-line basis from September 11, 2019, the date the Company took possession of the lease, through September 8, 2029 when the lease is set to terminate. In conjunction with this operating lease, the Company recognized an operating lease right-of-use right-of-use Total cash payments made under this operating lease were £0, for the three-month period ended September 30, 2019. Total rent expense recognized under this operating lease was £0 for the three-month period ended September 30, 2019. We have commitments under operating leases for laboratory and office space. We also have finance leases for manufacturing space and office equipment. Our leases have initial lease terms ranging from 3 years to 108 years. Certain lease agreements contain provisions for future rent increases. Payments due under the lease contracts include fixed payments. As of September 30, 2019, we have short term lease commitments amounting to approximately $100,000 on a monthly basis for three leases for office space that are month-to-month The components of lease cost for the three-month and nine-month periods ended September 30, 2019 are as follows: Three Months 9/30/3019 Nine Months 9/30/2019 Finance lease cost Amortization of right-of-use $ 64,181 $ 218,552 Interest on lease liabilities 606 1,598 Total Finance Lease Cost 64,787 220,150 Operating lease cost 897,310 1,324,474 Short-term lease cost 245,385 904,166 Total lease cost $ 1,207,482 $ 2,448,790 Amounts reported in the condensed consolidated balance sheets for leases where we are the lessee as of the period ended September 30, 2019 were as follows: September 30, Operating leases Right 22,106,415 Capitalized Lease Obligations 22,612,395 Finance leases Right-of-Use 6,695,342 Capitalized Lease Obligations 16,371 Weighted-Average Remaining Lease Term Operating leases 8.1 a Finance leases 107.3 Weighted-Average Discount Rate Operating Leases 8.5 % Finance Leases 6.9 % Other information related to leases as of the three-month and nine-month periods ended September 30, 2019 are as follows: Three Months 9/30/2019 Nine Months 9/30/ 2019 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from finance leases 6,857 20,223 Operating cash flows from operating leases 355,792 847,608 Financing cash flows from finance leases 321 1,313 Right-of-use assets obtained in exchange for lease liabilities Operating leases 5,938,426 22,932,582 Finance leases — — Future minimum lease payments under non-cancellable Operating Leases Finance Leases 2019 853,350 9,572 2020 4,012,039 7,179 2021 4,346,557 — 2022 3,839,442 — 2023 3,908,165 — Thereafter 13,997,959 — Total undiscounted lease payments 30,957,512 16,751 Less: Imputed interest (8,345,117 ) (380 ) Total lease liabilities 22,612,395 16,371

Commitments

Commitments	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments	10. Commitments There were no new material commitments entered into during the nine months ended September 30, 2019.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2019
Subsequent Events [Abstract]
Subsequent Events	11. Subsequent Event s Management has evaluated subsequent events through the date of this filing. Based on its evaluation, there were no subsequent events to report.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies and Recent Accounting Pronouncements (Policies)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Consolidation	Consolidation The accompanying condensed consolidated financial statements include the accounts of Meira Holdings and its wholly owned subsidiaries: MeiraGTx Limited, a limited company under the laws of England and Wales; MeiraGTx, LLC, a Delaware corporation; MeiraGTx UK II Limited, a limited company under the laws of England and Wales (“Meira UK II”); BRI-Alzan, MeiraGTx B.V., a Netherlands corporation; MeiraGTx Neurosciences, Inc., a Delaware corporation; and MeiraGTx UK Limited, a limited company under the laws of England and Wales. All intercompany balances and transactions between the consolidated companies have been eliminated in consolidation.
Use of Estimates	Use of Estimates Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these condensed consolidated financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. This process may result in actual results differing materially from those estimated amounts used in the preparation of the financial statements if these results differ from historical experience, or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made. In preparing these condensed consolidated financial statements, management used significant estimates in the following areas, among others: collaboration revenue (as disclosed in Note 8), the accounting for research and development costs, warrants, share-based compensation, leases and accrued expenses.
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 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: Description September 30, Significant Significant Other Significant Restricted cash $ 123,376 $ 123,376 $ — $ — Asset retirement obligations $ 131,213 $ — $ — $ 131,213 Fair Value Measurement Using: Description December 31, Significant Significant Other Significant Restricted cash $ 123,376 $ 123,376 $ — $ — Asset retirement obligations $ 128,119 $ — $ — $ 128,119
Net Loss per Ordinary Share	Net Loss per Ordinary Share Basic net loss per ordinary share is computed by dividing net loss by the weighted average number of shares of the Company’s ordinary shares assumed to be outstanding during the period of computation. Diluted net loss per ordinary share is computed similar to basic net loss per share except that the denominator is increased to include the number of additional ordinary shares that would have been outstanding if the potential ordinary shares had been issued at the beginning of the year and if the additional ordinary shares were dilutive (treasury stock method) or the two-class
Asset Retirement Obligations	Asset Retirement Obligations Accounting for asset retirement obligations requires legal obligations associated with the retirement of long-lived assets to be recognized at fair value when incurred and capitalized as part of the related long-lived asset. In the absence of quoted market prices, the Company estimates the fair value of its asset retirement obligations using Level 3 present value techniques, in which estimates of future cash flows associated with retirement activities are discounted using a credit-adjusted risk-free rate. Asset retirement obligations currently reported as other liabilities on the Condensed Consolidated Balance Sheet were measured during a period of historically low interest rates. The impact on measurements of new asset retirement obligations using different rates in the future may be significant. The Company uses estimates to determine the asset retirement obligations at the end of the lease term and discounts such asset retirement obligations using an estimated discount rate. Interest on the discounted asset retirement obligation is amortized over the term of the lease using the effective interest method and is recorded as interest expense in the condensed consolidated statements of operations and comprehensive loss. The change in asset retirement obligations is as follows: September 30, 2019 December 31, 2018 Balance at beginning of period $ 128,119 $ 178,419 Additional asset retirement obligations during the period — 69,286 Amortization of interest 7,861 (38,301 ) Change in estimate — (99,090 ) Effects of exchange rate (4,767 ) 17,805 Balance at end of period $ 131,213 $ 128,119
Research and Development	Research and Development Research and development costs are charged to expense as incurred. These costs include, but are not limited to, employee-related expenses, including salaries, benefits and travel of the Company’s research and development personnel; expenses incurred under agreements with contract research organizations and investigative sites that conduct clinical and preclinical studies and for the drug product for the clinical studies and preclinical activities; facilities; supplies; rent, insurance, certain legal fees, share-based compensation, depreciation and other costs associated with clinical and preclinical activities and regulatory operations. Research funding under collaboration agreements is recorded as an offset to these costs. Costs for certain development activities, such as Company funded outside research programs, are recognized based on an evaluation of the progress to completion of specific tasks with respect to their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the condensed consolidated financial statements as prepaid expenses or accrued expenses, as the case may be.
Collaboration Arrangements	Collaboration Arrangements The Company evaluates its collaborative arrangements pursuant to ASC 808, Collaborative Arrangements Revenue from Contracts with Customers ASC 808 does not address recognition or measurement matters related to collaborative arrangements. Payments between participants pursuant to a collaborative arrangement that are within the scope of other authoritative accounting literature on income statement classification are accounted for using the relevant provisions of that literature. If the payments are not within the scope of other authoritative accounting literature, the income statement classification for the payments is based on an analogy to authoritative accounting literature or if there is no appropriate analogy, a reasonable, rational and consistently applied accounting policy election. Payments received from a collaboration partner to which this policy applies may include upfront payments in respect of a license of intellectual property, development and commercialization-based milestones, and royalties. Refer to the discussion in Note 8 for further information related to the accounting for the Janssen Collaboration Agreement.
Revenue Recognition	Revenue Recognition Arrangements with collaborators may include licenses to intellectual property, research and development services, manufacturing services for clinical and commercial supply, and participation on joint steering committees. The Company evaluates the promised goods or services to determine which promises, or group of promises, represent performance obligations. In contemplation of whether a promised good or service meets the criteria required of a performance obligation, the Company considers the stage of development of the underlying intellectual property, the capabilities and expertise of the customer relative to the underlying intellectual property, and whether the promised goods or services are integral to or dependent on other promises in the contract. When accounting for an arrangement that contains multiple performance obligations, the Company must develop judgmental assumptions, which may include market conditions, reimbursement rates for personnel costs, development timelines and probabilities of regulatory success to determine the stand-alone selling price for each performance obligation identified in the contract. When the Company concludes that a contract should be accounted for as a combined performance obligation and recognized over time, the Company must then determine the period over which revenue should be recognized and the method by which to measure revenue. The Company generally recognizes revenue using a cost-based input method. The Collaboration Agreement with Janssen is accounted for under ASC 808, however, as ASC 808 does not address recognition or measurement matters such as determining the appropriate unit of accounting or when the recognition criteria are met, the Company accounts for the consideration received from Janssen in accordance with ASC 606. it performs the following five steps: i. identify the contract(s) with a customer; ii. identify the performance obligations in the contract; iii. determine the transaction price; iv. allocate the transaction price to the performance obligations within the contract; and v. recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it determines that it is probable it will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be by analogy within the scope of ASC 606, the Company assesses the goods or services promised within the contract to determine whether each promised good or service is a performance obligation. The promised goods or services in the Company’s arrangements typically consist of a license to the Company’s intellectual property and research, development and manufacturing services. The Company may provide options to additional items in such arrangements, which are accounted for as separate contracts when the customer elects to exercise such options, unless the option provides a material right to the customer. Performance obligations are promises in a contract to transfer a distinct good or service to the customer that (i) the customer can benefit from on its own or together with other readily available resources, and (ii) is separately identifiable from other promises in the contract. Goods or services that are not individually distinct performance obligations are combined with other promised goods or services until such combined group of promises meet the requirements of a performance obligation. The Company determines transaction price based on the amount of consideration the Company expects to receive for transferring the promised goods or services in the contract. Consideration may be fixed, variable, or a combination of both. At contract inception for arrangements that include variable consideration, the Company estimates the probability and extent of consideration it expects to receive under the contract utilizing either the most likely amount method or expected amount method, whichever best estimates the amount expected to be received. The Company then considers any constraints on the variable consideration and includes in the transaction price variable consideration to the extent it is deemed probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. The Company then allocates the transaction price to each performance obligation based on the relative standalone selling price and recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) control is transferred to the customer and the performance obligation is satisfied. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company records amounts as accounts receivable when the right to consideration is deemed unconditional. When consideration is received, or such consideration is unconditionally due, from a customer prior to transferring goods or services to the customer under the terms of a contract, a contract liability is recorded as deferred revenue. Amounts received prior to satisfying the revenue recognition criteria are recognized as deferred revenue in the Company’s condensed consolidated balance sheet. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue – related party, current. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue – related party. The Company’s collaboration revenue arrangements include the following: Up-front up-front non-refundable, up-front 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 will record costs associated with the development activities as research and development expenses in the condensed consolidated statement of operations and comprehensive loss consistent with ASC 730, Research and Development
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 License and Collaboration Agreement are generated in the United Kingdom. The following table summarizes non-current September 30, 2019 December 31, 2018 United States $ 13,390,438 $ 454,568 United Kingdom 33,272,991 21,788,130 $ 46,663,429 $ 22,242,698
Accounting Pronouncements Recently Adopted	Accounting Pronouncements Recently Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases 2016-02”). right-of-use initi al right-of-use No. 2018-10, 2016-02 No. 2018-11, 2016-02 right-of-use In October 2016, the FASB issued ASU 2016-16, Income Intra-Entity Transfers of Assets Other than Inventory ASU 2016-16, which ASU 2016-16 did In July 2019, the FASB issued ASU 2019-07, Codification Updates to SEC Sections—Amendments to SEC Paragraphs Pursuant to SEC Final Rule Releases No. 33-10532, 33-10231 33-10442, 2019-07 2019-07 2019-07,
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 held-to-maturity 2016-13 available-for-sale In , the FASB issued ASU 2018-13, Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurements , which changes the fair value measurement disclosure requirements of ASC . The goal of the ASU is to improve the effectiveness of ASC ’s disclosure requirements by providing users of the financial statements with better information about assets and liabilities measured at fair value in the financial statements and notes thereto. The guidance is applicable for fiscal years beginning after December , and interim periods within those years. The Company is currently evaluating the potential impact of the adoption of this standard on its related disclosures. In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808) : Clarifying the Interaction between Topic 808 and Topic 606 2018-18”). 2018-18 are 2018-18,

Summary of Significant Accoun_3

Summary of Significant Accounting Policies and Recent Accounting Pronouncements (Tables)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Company's Financial Assets and Liabilities Measured at Fair Value	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: Description September 30, Significant Significant Other Significant Restricted cash $ 123,376 $ 123,376 $ — $ — Asset retirement obligations $ 131,213 $ — $ — $ 131,213 Fair Value Measurement Using: Description December 31, Significant Significant Other Significant Restricted cash $ 123,376 $ 123,376 $ — $ — Asset retirement obligations $ 128,119 $ — $ — $ 128,119
Schedule of change in asset retirement obligations	The change in asset retirement obligations is as follows: September 30, 2019 December 31, 2018 Balance at beginning of period $ 128,119 $ 178,419 Additional asset retirement obligations during the period — 69,286 Amortization of interest 7,861 (38,301 ) Change in estimate — (99,090 ) Effects of exchange rate (4,767 ) 17,805 Balance at end of period $ 131,213 $ 128,119
Summary of Non-Current Assets by Geographical Area	The following table summarizes non-current September 30, 2019 December 31, 2018 United States $ 13,390,438 $ 454,568 United Kingdom 33,272,991 21,788,130 $ 46,663,429 $ 22,242,698

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2019
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses for the periods presented are comprised of the following: September 30, 2019 December 31, 2018 Clinical Trial Costs $ 5,509,493 $ 4,013,094 Compensation and Benefits 1,216,081 5,731,438 Consulting 1,049,451 821,009 Professional Fees 719,222 914,540 Manufacturing Costs 146,160 — Rent 94,688 122,770 Interest 60,032 40,800 Research and Development 8,145 236,271 Other 543,623 111,775 $ 9,346,895 $ 11,991,697

Share-Based Compensation (Table

Share-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2019
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 non-employee nine -month Number of Options Weighted- Aggregate Outstanding at December 31, 2018 3,254,365 $ 7.64 $ 6,903,313 Granted 500,000 18.44 Exercised (9,349 ) (5.84 ) Forfeited (21,319 ) (9.39 ) Outstanding at September 30, 2019 3,723,697 $ 9.08 $ 26,795,585 Weighted average remaining contractual life of options 9.24 Weighted average remaining contractual life of options 8.60 Options exercisable at December 31, 2018 535,241 $ 5.79 Options exercisable at September 30, 2019 1,098,211 $ 6.11 Weighted average remaining contractual life of options 7.88 Weighted average remaining contractual life of options 7.52
Schedule of Grant Date Fair Values of the Stock Option Granted	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: 2019 2018 Risk-free interest rate 2.03 - 2.55% 2.32% - 2.84% Expected volatility 90% 90% Expected dividend yield 0% 0% Expected life (in years) 6.1 5.5 - 9.5
Summary of Restricted Ordinary Shares	A summary of the restricted ordinary shares is as follows: Ordinary Shares $ Value Non-vested 653,174 $ 9,797,610 Vested during nine-month period ended September 30, 2019 (326,586 ) (4,898,790 ) Non-vested 326,588 $ 4,898,820
Schedule of Share Based Compensation Expense	During the three-month and nine-month periods ended September 30, 2019 and 2018 the Company recognized total share-based compensation expense in the accompanying condensed consolidated statements of operations and comprehensive loss as follows: Three-month periods ended September 30, 2019 2018 Research and development $ 1,131,659 $ 1,040,499 General and administrative 2,373,892 1,881,858 Total share based compensation $ 3,505,551 $ 2,922,357 Nine-month periods ended September 30, 2019 2018 Research and development $ 2,828,944 $ 2,931,010 General and administrative 7,997,721 12,624,903 Total share based compensation $ 10,826,665 $ 15,555,913

Net Loss per Ordinary Share (Ta

Net Loss per Ordinary Share (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Net Loss per Share	Basic and diluted net loss per ordinary share is computed as follows: Three-month periods ended 2019 2018 Net loss - basic and diluted $ (10,460,854 ) $ (15,424,944 ) Weighted-average ordinary shares outstanding: Basic and Diluted 34,663,623 26,340,450 Net loss per share: Basic and Diluted $ (0.30 ) $ (0.59 ) Nine-month periods ended 2019 2018 Net loss - basic and diluted $ (49,265,184 ) $ (61,809,129 ) Accretion of Preferred Shares financing costs — (761,012 ) Accretion of warrant — (1,045,500 ) Adjusted net loss - basic and diluted $ (49,265,184 ) $ (63,615,641 ) Weighted-average ordinary shares outstanding: Basic and Diluted 32,111,733 16,355,849 Adjusted net loss per ordinary share: Basic and Diluted $ (1.53 ) $ (3.89 )
Schedule of Antidilutive Securities Excluded from Computation of Earnings per Share	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: September 30, September 30, Restricted ordinary shares subject to forfeiture 326,588 762,036 Share options 3,723,697 1,629,687 4,050,285 2,391,723

Related Party Transactions (Tab

Related Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2019
Schedule of Future Minimum Rental Payments	The aggregate future minimum rental payments under this lease as of September 30, 2019 for years ending December 31 are as follows: 2019 $ 136 , 2020 554,432 2021 573,837 Total future rent payments $ 1,264,493

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Schedule of Components of Lease Cost	The components of lease cost for the three-month and nine-month periods ended September 30, 2019 are as follows: Three Months 9/30/3019 Nine Months 9/30/2019 Finance lease cost Amortization of right-of-use $ 64,181 $ 218,552 Interest on lease liabilities 606 1,598 Total Finance Lease Cost 64,787 220,150 Operating lease cost 897,310 1,324,474 Short-term lease cost 245,385 904,166 Total lease cost $ 1,207,482 $ 2,448,790
Schedule of Condensed Consolidated Balance Sheets for Leases	Amounts reported in the condensed consolidated balance sheets for leases where we are the lessee as of the period ended September 30, 2019 were as follows: September 30, Operating leases Right 22,106,415 Capitalized Lease Obligations 22,612,395 Finance leases Right-of-Use 6,695,342 Capitalized Lease Obligations 16,371 Weighted-Average Remaining Lease Term Operating leases 8.1 a Finance leases 107.3 Weighted-Average Discount Rate Operating Leases 8.5 % Finance Leases 6.9 %
Schedule of Other Information Related to Leases	Other information related to leases as of the three-month and nine-month periods ended September 30, 2019 are as follows: Three Months 9/30/2019 Nine Months 9/30/ 2019 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from finance leases 6,857 20,223 Operating cash flows from operating leases 355,792 847,608 Financing cash flows from finance leases 321 1,313 Right-of-use assets obtained in exchange for lease liabilities Operating leases 5,938,426 22,932,582 Finance leases — —
Schedule of Future Minimum Lease Payments Under Non-cancellable Leases	Future minimum lease payments under non-cancellable Operating Leases Finance Leases 2019 853,350 9,572 2020 4,012,039 7,179 2021 4,346,557 — 2022 3,839,442 — 2023 3,908,165 — Thereafter 13,997,959 — Total undiscounted lease payments 30,957,512 16,751 Less: Imputed interest (8,345,117 ) (380 ) Total lease liabilities 22,612,395 16,371

Organization and Basis of Pre_2

Organization and Basis of Presentation - Additional Information (Detail) - USD ($)	1 Months Ended	9 Months Ended
	Jan. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Schedule Of Description Of Business [Line Items]
Accumulated deficit		$ (197,554,901)		$ (148,289,717)
Cash flows from operations		42,016,287	$ (47,419,158)
Cash and cash equivalents		$ 253,330,623		$ 68,080,175
Collaboration Option And License Agreement [Member] | Minimum [Member] | JJDC [Member]
Schedule Of Description Of Business [Line Items]
Offsetting expense, period		12 months
Collaboration Option And License Agreement [Member] | Janssen Pharmaceuticals Inc [Member]
Schedule Of Description Of Business [Line Items]
Upfront payment	$ 100,000,000	$ 100,000,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Company's Financial Instruments Carried at Fair Value Measurements (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Restricted Cash [Member]
Fair Value, Net Asset (Liability)	$ 123,376	$ 123,376
Restricted Cash [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Net Asset (Liability)	123,376	123,376
Asset Retirement Obligations [Member]
Fair Value, Net Asset (Liability)	131,213	128,119
Asset Retirement Obligations [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Net Asset (Liability)	$ 131,213	$ 128,119

Summary of Significant Accoun_5

Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Additional Information (Detail) - USD ($)	Jan. 01, 2019	Sep. 30, 2019	Dec. 31, 2018
Discount rate	8.00%
Reclassification from property and equipment of fully paid lease	$ 7,321,251
Lease Obligations Non Current	$ 3,716,336	$ 20,600,077	$ 7,097
Janssen Pharmaceuticals Inc [Member]
Percentage of costs payable on annual net sales of licensed product statement		100.00%

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Change in Asset Retirement Obligations (Detail) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Asset Retirement Obligation [Abstract]
Balance at beginning of period	$ 128,119	$ 178,419	$ 178,419
Additional asset retirement obligations during the period			69,286
Amortization of interest	7,861	$ 10,918	(38,301)
Change in estimate			(99,090)
Effects of exchange rate	(4,767)		17,805
Balance at end of period	$ 131,213		$ 128,119

Summary of Significant Accoun_7

Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Summary of Non-Current Assets by Geographical Area (Detail) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Non current assets	$ 46,663,429	$ 22,242,698
United States
Non current assets	13,390,438	454,568
United Kingdom
Non current assets	$ 33,272,991	$ 21,788,130

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Clinical Trial Costs	$ 5,509,493	$ 4,013,094
Compensation and Benefits	1,216,081	5,731,438
Consulting	1,049,451	821,009
Professional Fees	719,222	914,540
Manufacturing Costs	146,160
Rent	94,688	122,770
Interest	60,032	40,800
Research and Development	8,145	236,271
Other	543,623	111,775
Accrued expenses	$ 9,346,895	$ 11,991,697

Share Based Compensation - Addi

Share Based Compensation - Additional Information (Detail) - USD ($)	Jun. 07, 2018	Mar. 01, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of options Vested			$ 429,647	$ 503,828	$ 2,718,315	$ 1,060,177
Share options granted during the period					500,000
Weighted average remaining contractual life of options outstanding					8 years 7 months 6 days		9 years 2 months 26 days
Share based compensation					$ 10,826,665	15,555,913
Excess Tax Benefit from Share-based Compensation, Operating Activities					0	0
Excess Tax Benefit from Share-based Compensation, Financing Activities					$ 0	0
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average remaining contractual life of options outstanding					10 years
Ordinary shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fully-diluted outstanding shares		3.00%
Share based compensation		$ 3,096,104				6,456,215
Ordinary shares, issued		550,162
Ordinary shares [Member] | General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation						3,096,104
Restricted Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares	1,306,348
Ordinary shares forfeiture period								3 years
Ordinary shares awarded, per share	$ 15
Fully-diluted outstanding shares	5.00%
Share based compensation			5,587,546	3,405,274	$ 11,840,200	17,026,140
Restricted Shares [Member] | General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation			3,265,872	$ 1,992,182	4,898,808	$ 8,523,932
Restricted Shares [Member] | Ordinary shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares								867,935
Employee and Non Employee Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unvested options compensation expense			$ 18,626,465		$ 18,626,465
Share options granted during the period			195,000	0	500,000	695,685
Unvested options expected to be realized					3 years 9 months
Weighted average grant date fair value of options granted					$ 13.86	$ 4.46
Consultant [Member] | Restricted Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares awarded, per share				$ 7.72		7.72
Employee [Member] | Restricted Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares awarded, per share				$ 7.76		$ 7.76
First Anniversary [Member]
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 Related to Employees, Non-Employee Members of the Board of Directors and Non-Employee Consultants (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of options, Beginning balance | shares	3,254,365
Number of options, Granted | shares	500,000
Number of options, Exercised | shares	(9,349)
Number of options, Forfeited | shares	(21,319)
Number of options, Ending balance | shares	3,723,697	3,254,365
Weighted average remaining contractual life of options outstanding	8 years 7 months 6 days	9 years 2 months 26 days
Number of options, Options exercisable | shares	1,098,211	535,241
Weighted average remaining contractual life of options exercisable	7 years 6 months 7 days	7 years 10 months 17 days
Weighted- average exercise price, beginning balance | $ / shares	$ 7.64
Weighted- average exercise price, granted | $ / shares	18.44
Weighted- average exercise price, exercised | $ / shares	(5.84)
Weighted- average exercise price, forfeited | $ / shares	(9.39)
Weighted- average exercise price, ending balance | $ / shares	9.08	$ 7.64
Weighted- average exercise price, option exercisable | $ / shares	$ 6.11	$ 5.79
Aggregate Intrinsic Value | $		$ 6,903,313
Aggregate Intrinsic Value, Options Exercisable | $	$ 26,795,585

Share Based Compensation - Sche

Share Based Compensation - Schedule of Grant Date Fair Values of the Stock Option Granted Black Scholes Valuation Model (Detail) - Employee and Non Employee Board of Directors [Member]	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.03%	2.32%
Risk-free interest rate	2.55%	2.84%
Expected volatility	90.00%	90.00%
Expected dividend yield	0.00%	0.00%
Expected life of non-employee options (in years)	6 years 1 month 6 days
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of non-employee options (in years)		5 years 6 months
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of non-employee options (in years)		9 years 6 months

Share Based Compensation - Su_2

Share Based Compensation - Summary of Restricted Ordinary Shares (Detail) - Restricted Shares [Member]	9 Months Ended
	Sep. 30, 2019USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested Ordinary Shares, Beginning Balance | shares	653,174
Vested, Ordinary Shares | shares	(326,586)
Non-vested Ordinary Shares, Ending Balance | shares	326,588
Non-vested Value, Beginning Balance | $	$ 9,797,610
Vested, Value | $	(4,898,790)
Non-vested Value, Ending Balance | $	$ 4,898,820

Share Based Compensation - Sc_2

Share Based Compensation - Schedule of Share Based Compensation Expense (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share Based Compensation Expense [Line Items]
Total share based compensation	$ 3,505,551	$ 2,922,357	$ 10,826,665	$ 15,555,913
Research and Development Expenses [Member]
Share Based Compensation Expense [Line Items]
Total share based compensation	1,131,659	1,040,499	2,828,944	2,931,010
General and Administrative Expense [Member]
Share Based Compensation Expense [Line Items]
Total share based compensation	$ 2,373,892	$ 1,881,858	$ 7,997,721	$ 12,624,903

Ordinary Shares - Additional In

Ordinary Shares - Additional Information (Detail) - USD ($)	Mar. 21, 2019	Feb. 27, 2019	Aug. 07, 2019	Mar. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Class of Stock [Line Items]
Common stock, shares issued					36,571,722		27,386,632
Gross proceeds from public offering					$ 155,200,007	$ 69,750,000
Private Placement [Member]
Class of Stock [Line Items]
Common stock, shares issued		5,797,102
Proceeds from issuance of private placement		$ 80,000,000
Offering costs		$ 2,400,000
IPO [Member]
Class of Stock [Line Items]
Common stock, shares issued			3,200,000
Offering costs			$ 5,100,000
Gross proceeds from public offering			$ 75,000,000
JJDC [Member] | Private Placement [Member]
Class of Stock [Line Items]
Common stock, shares issued		2,898,550
Ordinary shares [Member]
Class of Stock [Line Items]
Issuance of ordinary shares in connection with a license agreement, shares	158,832			158,832	158,832

Net Loss per Ordinary Share - S

Net Loss per Ordinary Share - Schedule of Basic and Diluted Net Loss per Share (Detail) - USD ($)	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net loss—basic and diluted	$ (10,460,854)	$ (20,822,412)	$ (17,981,918)	$ (15,424,944)	$ (29,980,832)	$ (16,403,353)	$ (49,265,184)	$ (61,809,129)
Accretion of Preferred Shares financing costs								(761,012)
Accretion of warrant								(1,045,500)
Adjusted net loss - basic and diluted							$ (49,265,184)	$ (63,615,641)
Weighted-average ordinary shares outstanding:
Basic and Diluted	34,663,623			26,340,450			32,111,733	16,355,849
Adjusted net loss per ordinary share:
Basic and Diluted	$ (0.30)			$ (0.59)			$ (1.53)	$ (3.89)

Net Loss per Ordinary Share -_2

Net Loss per Ordinary Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings per Share (Detail) - shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earning per share, amount	4,050,285	2,391,723
Restricted Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earning per share, amount	326,588	762,036
Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earning per share, amount	3,723,697	1,629,687

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Provision for Income Taxes	$ (338,670)	$ 0	$ (430,060)	$ 0
Benefit For Income Tax [Member]
Deferred State and Local Income Tax Expense (Benefit)	338,670		430,060
Other Comprehensive Income [Member]
Deferred State and Local Income Tax Expense (Benefit)	$ (338,670)		$ (430,060)

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail)	Feb. 04, 2015Program	Jan. 30, 2019USD ($)	Sep. 30, 2019USD ($)shares	Mar. 31, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)shares	Sep. 30, 2019GBP (£)shares	Sep. 30, 2018USD ($)	Oct. 31, 2020USD ($)	Oct. 31, 2020GBP (£)	Sep. 30, 2019GBP (£)shares	Feb. 27, 2019shares	Dec. 31, 2018USD ($)shares
Related Party Transaction [Line Items]
Common stock, shares issued | shares			36,571,722			36,571,722					36,571,722		27,386,632
License revenue - related party			$ 3,582,586			$ 6,349,222
Deferred research funding, amortization period			8 months			8 months	8 months
Research and development expenses			$ 4,614,446		$ 8,109,160	$ 27,362,432		$ 22,827,176
Issuance of ordinary shares in connection with a license agreement				$ 1,966,340
Total charges incurred			145,755		140,805	$ 430,649		416,479
Janssen Pharmaceuticals Inc [Member]
Related Party Transaction [Line Items]
Percentage of costs payable on annual net sales of licensed product statement						100.00%	100.00%
Collaboration Agreement [Member] | Janssen Pharmaceuticals Inc [Member]
Related Party Transaction [Line Items]
Deferred research funding			658,667			$ 658,667
Collaboration Agreement [Member] | Janssen Pharmaceuticals Inc [Member] | Research and Development Expense [Member]
Related Party Transaction [Line Items]
Amortized of deferred research funding			0			444,399
Collaboration Agreement [Member] | Janssen Pharmaceuticals Inc [Member] | Research and Development Expense [Member] | Amortisation Stage Two [Member]
Related Party Transaction [Line Items]
Deferred research funding			328,524			328,524
LicenseAgreement [Member]
Related Party Transaction [Line Items]
Research and development expenses						$ 3,942,000
License agreement amendment description						On January 29, 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.	On January 29, 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.
License arrangement upfront payment						$ 1,976,000	£ 1,500,000
Issuance of ordinary shares in connection with a license agreement, shares | shares						158,832	158,832
Issuance of ordinary shares in connection with a license agreement						$ 1,966,000	£ 1,500,000
Payments for research and development expenses agreement						4,111,876		219,863
Transition Services Agreement with Related Party [Member] | Kadmon [Member]
Related Party Transaction [Line Items]
Cash payment			145,755		140,954	430,649		1,284,258
Clinical Collaborative Arrangement [Member] | Janssen Pharmaceuticals Inc [Member]
Related Party Transaction [Line Items]
Commercial milestone payments		$ 340,000,000
Percentage of royalties payable on annual net sales of licensed product statement		20.00%
Percentage of costs payable on annual net sales of licensed product statement		100.00%
Research Collaborative Arrangement [Member] | Janssen Pharmaceuticals Inc [Member]
Related Party Transaction [Line Items]
Percentage of costs payable on annual net sales of licensed product statement		100.00%
License revenue - related party			3,582,586			6,349,222
Revenue recognized			9,303,405			13,319,084
Deferred revenue associated with the non-refundable upfront fee, expected to be recognized			93,650,778			$ 93,650,778
Deferred revenue associated with the non-refundable upfront fee, expected to be recognition period						7 years 3 months	7 years 3 months
Collaboration Option And License Agreement [Member] | Janssen Pharmaceuticals Inc [Member]
Related Party Transaction [Line Items]
Non-refundable upfront fee received		$ 100,000,000				$ 100,000,000
July 2016 Lease [Member]
Related Party Transaction [Line Items]
Operating lease expiration date						Dec. 31, 2021	Dec. 31, 2021
Operating leases rent expense payment description						The Company records monthly rent expense on a straight-line basis from July 1, 2016 through December 31, 2021.	The Company records monthly rent expense on a straight-line basis from July 1, 2016 through December 31, 2021.
Deferred rent			167,480			$ 167,480							$ 201,264
Operating lease rent expenses			121,890		121,888	365,666		365,668
Aggregate future minimum rental payments under operating lease			1,264,493			1,264,493
Letter of credit outstanding amount			122,866			$ 122,866
Private Placement [Member]
Related Party Transaction [Line Items]
Common stock, shares issued | shares												5,797,102
Private Placement [Member] | JJDC [Member]
Related Party Transaction [Line Items]
Common stock, shares issued | shares												2,898,550
UCL Consultants Limited [Member] | Research Agreement [Member]
Related Party Transaction [Line Items]
Agreement termination notice period						30 days	30 days
Research and development expenses			72,000		$ 137,000	$ 245,000		$ 509,000
Amount due under services agreement			480,825			480,825							$ 389,101
UCL Consultants Limited [Member] | Forecast [Member] | Research Agreement [Member]
Related Party Transaction [Line Items]
Future obligations under agreement									$ 101,931	£ 82,941
UCL Business, PLC [Member] | License Agreements Effective March 15, 2018 [Member] | LicenseAgreement [Member]
Related Party Transaction [Line Items]
Number Of Collaborations Programs | Program	8
Sales milestone payments			$ 48,900,000			48,900,000					£ 39,800,000
Maintenance fee						$ 65,000	£ 50,000

Related Party Transactions - Sc

Related Party Transactions - Schedule of Future Minimum Rental Payments (Detail) - July 2016 Lease [Member]	Sep. 30, 2019USD ($)
Related Party Transaction [Line Items]
2019	$ 136,224
2020	554,432
2021	573,837
Total future rent payments	$ 1,264,493

Leases - Additional Information

Leases - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)	Sep. 30, 2019GBP (£)	Sep. 30, 2019USD ($)	Sep. 30, 2019GBP (£)	Jun. 30, 2019GBP (£)
Lessee, Lease, Description [Line Items]
Short term lease commitments	$ 100,000		$ 100,000
Right-of-Use Asset	22,106,415		22,106,415
Operating lease liability	22,612,395		22,612,395
Operating leases	5,938,426		22,932,582
New York Sublease [Member]
Lessee, Lease, Description [Line Items]
Right-of-Use Asset	12,200,000		12,200,000
Operating lease liability	12,200,000		12,200,000
Rent expense under operating lease agreements	90,000		90,000
Tudor Street Lease [Member]
Lessee, Lease, Description [Line Items]
Right-of-Use Asset | £				£ 4,800,000	£ 1,200,000
Operating lease liability	1,500,000		1,500,000
Operating leases			$ 5,900,000
Operating lease cash payments	52,000	£ 42,600
Rent expense under operating lease agreements	$ 105,000	85,200
Option to terminate			The Company has the right to terminate this lease on June 10, 2024 by giving the landlord notice at least six months prior to such date.
Provost Street Lease [Member]
Lessee, Lease, Description [Line Items]
Operating lease cash payments | £		0
Rent expense under operating lease agreements | £		£ 0
Option to terminate			The Company has the right to terminate this lease on September 8, 2024 by giving the landlord notice at least six months prior to such date.
Minimum [Member]
Lessee, Lease, Description [Line Items]
Lease term			3 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Lease term			108 years

Leases - Schedule of Components

Leases - Schedule of Components of Lease Cost (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Finance Lease Costs [Abstract]
Amortization of right-of-use assets	$ 64,181	$ 218,552
Interest on lease liabilities	606	1,598
Total Finance Lease Cost	64,787	220,150
Operating lease cost	897,310	1,324,474
Short-term lease cost	245,385	904,166
Total lease cost	$ 1,207,482	$ 2,448,790

Leases - Schedule of Condensed

Leases - Schedule of Condensed Consolidated Balance Sheets for Leases (Detail)	Sep. 30, 2019USD ($)
Operating leases
Right of Use Asset	$ 22,106,415
Capitalized Lease Obligations	22,612,395
Finance leases
Right-of-Use Asset	6,695,342
Capitalized Lease Obligations	$ 16,371
Weighted-Average Remaining Lease Term
Operating leases	8 years 1 month 6 days
Finance leases	107 years 3 months 18 days
Weighted-Average Discount Rate
Operating leases	8.50%
Finance leases	6.90%

Leases - Schedule of Other Info

Leases - Schedule of Other Information Related to Leases (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from finance leases	$ 6,857	$ 20,223
Operating cash flows from operating leases	355,792	847,608
Financing cash flows from finance leases	321	1,313
Right-of-use assets obtained in exchange for lease liabilities
Operating leases	5,938,426	22,932,582
Finance leases	$ 0	$ 0

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Lease Payments Under Non-cancellable Leases (Detail)	Sep. 30, 2019USD ($)
Operating Leases
2019	$ 853,350
2020	4,012,039
2021	4,346,557
2022	3,839,442
2023	3,908,165
Thereafter	13,997,959
Total undiscounted lease payments	30,957,512
Less: Imputed interest	(8,345,117)
Total lease obligations	22,612,395
Finance Leases
2019	9,572
2020	7,179
2021	0
2022	0
2023	0
Thereafter	0
Total undiscounted lease payments	16,751
Less: Imputed interest	(380)
Total lease liabilities	$ 16,371