MeiraGTx (MGTX) 10-Q 14 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 30, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Trading Symbol	MGTX
Entity Registrant Name	MeiraGTx Holdings plc
Entity Central Index Key	0001735438
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		33,342,566
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)	Mar. 31, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 227,275,139	$ 68,080,175
Prepaid expenses	1,765,209	1,937,785
Other current assets	2,117,334	4,634,105
Total Current Assets	231,157,682	74,652,065
Property and equipment, net	15,858,667	22,014,237
Security deposits	107,593	105,085
Restricted cash	123,376	123,376
Right-of-use assets	10,606,985
TOTAL ASSETS	257,854,303	96,894,763
CURRENT LIABILITIES:
Accounts payable	3,382,373	3,042,861
Accrued expenses	7,996,329	11,991,697
Lease obligations, current	679,025	27,199
Deferred revenue, related party, current	20,951,000
Other current liabilities	195,618	437,053
Total Current Liabilities	33,204,345	15,498,810
Deferred revenue - related party	77,186,561
Lease obligations	2,911,331	7,097
Deferred rent		201,264
Asset retirement obligations	133,816	128,119
TOTAL LIABILITIES	113,436,053	15,835,290
COMMITMENTS
SHAREHOLDERS' EQUITY:
Ordinary Shares, $0.00003881 nominal value, 1,288,327,750 authorized 33,342,566 issued and outstanding at March 31, 2019 27,386,632 issued and outstanding at December 31, 2018	1,295	1,064
Capital in excess of nominal value	311,528,607	229,054,460
Accumulated other comprehensive (loss) income	(840,017)	293,666
Accumulated deficit	(166,271,635)	(148,289,717)
Total Shareholders' Equity	144,418,250	81,059,473
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 257,854,303	$ 96,894,763

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 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	33,342,566	27,386,632
Common stock, shares outstanding	33,342,566	27,386,632

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
License revenue - related party	$ 784,960
Operating expenses:
General and administrative	8,499,475	$ 11,122,016
Research and development	12,976,229	6,927,322
Total operating expenses	21,475,704	18,049,338
Loss from operations	(20,690,744)	(18,049,338)
Other non-operating income (expense):
Foreign currency gain	2,718,400	978,624
Change in fair value of warrant liability		669,408
Interest income		25,308
Interest expense	(9,574)	(27,355)
Net loss	(17,981,918)	(16,403,353)
Other comprehensive (loss):
Foreign currency translation	(1,133,683)	(757,765)
Total comprehensive loss	(19,115,601)	(17,161,118)
Net loss	(17,981,918)	(16,403,353)
Accretion on convertible preferred C shares and warrants		(664,718)
Adjusted net loss	$ (17,981,918)	$ (17,068,071)
Basic and diluted adjusted net loss per ordinary share	$ (0.62)	$ (1.91)
Weighted-average number of ordinary shares outstanding	28,776,915	8,927,433

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS EQUITY	USD ($)	License Agreement [Member]GBP (£)shares	License Agreement [Member]USD ($)shares	Private Placement [Member]USD ($)	Ordinary shares [Member]USD ($)shares	Ordinary shares [Member]Private Placement [Member]USD ($)shares	Capital in Excess of Nominal Value [Member]USD ($)	Capital in Excess of Nominal Value [Member]Private 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]License Agreement [Member]USD ($)shares	Convertible Preferred C Shares [Member]Sales Agreement [Member]USD ($)shares
Temporary equity, beginning Balance at Dec. 31, 2017												$ 51,338,631
Issuance of convertible preferred C shares, net of issuance costs													$ 1,356,129	$ 140,000	$ 43,851,602
Temporary equity, beginning Balance, Shares at Dec. 31, 2017 | shares												5,005,935
Accretion of issuance costs on convertible preferred C shares												$ 94,445
Accretion of warrants issued in connection with convertible preferred C shares												570,273
Temporary equity, ending Balance at Mar. 31, 2018												$ 97,351,080
Temporary equity, ending Balance, Shares at Mar. 31, 2018 | shares												9,361,167
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 issuance costs on convertible preferred C shares	(94,445)						(94,445)
Accretion of warrants issued in connection with convertible preferred C shares	(570,273)						(570,273)
Issuance of shares, net of issuance costs, Shares | shares													129,419	13,360	4,212,453
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
Ending Balance, Shares at Mar. 31, 2018 | shares											9,376,352
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	£ 1,500,000	$ 1,966,000		$ 6		1,966,334
Issuance of ordinary shares in connection with a license agreement, shares | shares		158,832	158,832		158,832
Sale of ordinary shares in connection with private placement, net of issuance costs				$ 77,573,047		$ 225		$ 77,572,822
Issuance of shares, 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

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS EQUITY (Parenthetical)	3 Months Ended
	Mar. 31, 2019USD ($)
Private Placement [Member]
Sale of ordinary shares in connection with private placement, issuance costs	$ 2,426,953

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Cash flows from operating activities:
Net loss	$ (17,981,918)	$ (16,403,353)
Adjustments to reconcile net loss to net cash used in operating activities:
Shares issued in connection with license agreements	1,966,340	140,000
Share-based compensation expense	2,934,991	4,275,735
Foreign currency gain	(2,718,400)	(978,624)
Depreciation	499,641	458,836
Amortization of interest on asset retirement obligation	2,639	3,678	$ (38,301)
Change in fair value of warrant liability		(669,408)
(Increase) in operating assets:
Prepaid expenses	188,044	(821,062)
Other current assets	2,523,388	153,773
Security deposits	130,949
Increase (decrease) in operating liabilities:
Accounts payable	304,716	171,045
Accrued expenses	(4,124,797)	(2,846,292)
Due to Kadmon		(854,537)
Other liabilities	(252,322)
Deferred revenue	98,692,719
Deferred rent		(25,760)
Net cash provided by (used in) operating activities	82,165,990	(17,395,969)
Cash flows from investing activities:
Purchase of property, plant and equipment	(1,115,233)	(1,210,452)
Net cash used in investing activities	(1,115,233)	(1,210,452)
Cash flows from financing activities:
Payments on lease obligations - financing leases	(6,624)	(7,779)
Proceeds from the sale of ordinary shares	80,000,000
Proceeds from the sale of convertible preferred C shares, net of issuance costs		43,851,602
Payment of note payable		(1,442,009)
Net cash provided by financing activities	77,566,423	42,401,814
Net increase in cash, cash equivalents and restricted cash	158,617,180	23,795,393
Effect of exchange rate changes on cash	577,784	12,820
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	227,398,515	32,480,227	$ 68,203,551
Supplemental disclosure of non-cash transactions:
Fixed asset acquisition included in accounts payable and accrued expenses at end of period	236,535	(811,095)
Issuance of convertible preferred C shares in connection with payables		1,356,129
Lease obligations for right-of-use asset	10,930,367
Supplemental disclosure of cash flow information:
Cash paid for interest	553	31,531
Ordinary shares [Member]
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense		$ 6,456,215
Cash flows from financing activities:
Issuance costs in connection with ordinary shares	$ (2,426,953)

Organization and Basis of Prese

Organization and Basis of Presentation	3 Months Ended
	Mar. 31, 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”), a limited company 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 no effective treatments available. The Company is focused on developing therapies for ocular diseases, including rare inherited blindness as well as Xerostomia following radiation treatment for head and neck cancers and neurodegenerative diseases such as amyothrophic lateral sclerosis (“ALS”) and Parkinson’s disease (“PD”). 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 S-X. 10-K 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 March 31, 2019 totaled $166,271,635, 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 quarter ended March 31, 2019, the Company generated $82,165,990 of positive cash flows from operations. However, prior to the quarter ended March 31, 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 March 31, 2019, the Company had cash and cash equivalents in the amount of $227,275,139, 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 March 31, 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 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	3 Months Ended
	Mar. 31, 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 (“Meira Limited); MeiraGTx, LLC, a Delaware corporation (“Meira LLC”); BRI-Alzan, (“BRI-Alzan”); MeiraGTx B.V., a Netherlands corporation (“Meira BV”); MeiraGTx Neurosciences, Inc., a Delaware corporation (“Meira Neuro”); MeiraGTx UK II Limited, (“Meira UK II”), a limited company under the laws of England and Wales; and MeiraGTx UK Limited (“Meira UK”), 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 March 31, Significant Significant Other Significant Restricted cash $ 123,376 $ 123,376 $ — $ — Fair Value Measurement Using: Description December 31, Significant Significant Other Significant Restricted cash $ 123,376 $ 123,376 $ — $ — 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: March 31, 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 2,639 (38,301 ) Change in estimate — (99,090 ) Effects of exchange rate 3,058 17,805 Balance at end of period $ 133,816 $ 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 manufacture 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 Agreements. 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, Collaborative Arrangements Revenue from Contracts with Customers 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, non-current. The Company’s collaboration revenue arrangement includes 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 50% to 100%, 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. The reimbursement of the research and development costs by Janssen is representative of the joint risk sharing nature of the arrangement. The Company considered the guidance is ASC 808 and will recognize the payments received from Janssen as a reduction to research and development expense when the related costs are incurred. For the three months ended March 31, 2019, the Company recognized the reimbursement to be received from Janssen in the amount of $1,037,542. 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 March 31, 2019 December 31, 2018 United States $ 1,643,688 $ 454,568 United Kingdom 25,052,933 21,788,130 $ 26,696,621 $ 22,242,698 Accounting Pronouncements Recently Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases 2016-02”). right-of-use 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 Recent Accounting Pronouncements Not Yet Adopted In August 2018, the FASB issued ASU 2018-13, Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurements, In November 2018, the FASB issued ASU No. 2018-18, Clarifying the Interaction between Topic 808 and Topic 606 2018-18”). Collaborative Agreements and Accounting Standards Codification 606, Revenue from Contracts with Customers 2018-18 are 2018-18,

Accrued Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2019
Payables and Accruals [Abstract]
Accrued Expenses	3. Accrued Expenses Accrued expenses for the periods presented are comprised of the following: March 31, 2019 December 31, 2018 Clinical Trial Costs $ 4,705,140 $ 4,013,094 Consulting 1,297,704 821,009 Professional Fees 909,668 914,540 Compensation and Benefits 323,111 5,731,438 Research and Development 286,230 236,271 Rent 217,899 122,770 Interest 47,180 40,800 Other 209,397 111,775 $ 7,996,329 $ 11,991,697

Share-Based Compensation

Share-Based Compensation	3 Months Ended
	Mar. 31, 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 (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 Number of Options Weighted- Aggregate Outstanding at December 31, 2018 3,262,365 $ 7.64 $ 6,903,313 Granted 50,000 9.64 Exercised — — Expired — — Forfeited — — Outstanding at March 31, 2019 3,312,365 $ 7.72 $ 32,004,958 Weighted average remaining contractual life of options outstanding as of December 31, 2018 (yrs) 9.24 Weighted average remaining contractual life of options outstanding as of March 31, 2019 (yrs) 9.64 Options exercisable at December 31, 2018 535,241 $ 5.79 Options exercisable at March 31, 2019 857,791 $ 5.68 Weighted average remaining contractual life of options exercisable as of December 31, 2018 (yrs) 7.88 Weighted average remaining contractual life of options exercisable as of March 31, 2019 (yrs) 8.02 The total fair value of options vested during the three-month periods ended March 31, 2019 and 2018 was $1,390,942 and $309,147, respectively. During the three-month periods ended March 31, 2109 and 2018, the Company granted 50,000 and 533,358 share options. 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 2.51% 2.76% - 2.81% Expected volatility 90% 90% Expected dividend yield 0% 0% Expected life (in years) 5.5 - 10.0 7.9 - 9.8 As of March 31, 2019, the total compensation expense relating to unvested options granted that had not yet been recognized was $16,550,086, which is expected to be realized over a period of 4.0 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 three-month periods ended March 31, 2019 and 2018 was $9.64 and $4.35, 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 were included in loss from operations over the requisite service period. As of March 31, 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 A summary of the restricted ordinary shares is as follows: Ordinary Shares $ Value Non-vested 653,174 $ 9,797,610 Vested during three-month period ended March 31, 2019 (108,862 ) (1,632,930 ) Non-vested 544,312 $ 8,164,680 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 three-month period ended March 31, 2018. During the three-month periods ended March 31, 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 March 31, 2019 2018 Research and development $ 834,314 $ 842,961 General and administrative 2,100,677 3,432,774 Total share based compensation $ 2,934,991 $ 4,275,735 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 periods ended March 31, 2019 and 2018.

Ordinary Shares

Ordinary Shares	3 Months Ended
	Mar. 31, 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., the investment arm of Johnson and Johnson, led the offering and 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, (30)-day 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 Share

Net Loss per Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Net Loss per Share	6. Net Loss per Share 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 March 31, 2019 2018 Net loss—basic and diluted $ (17,981,918 ) $ (16,403,353 ) Accretion of Preferred Shares financing costs — (94,445 ) Accretion of warrant — (570,273 ) Adjusted net loss—basic and diluted $ (17,981,918 ) $ (17,068,071 ) Weighted-average ordinary shares outstanding: Basic and Diluted 28,776,915 8,927,433 Adjusted net loss per ordinary share: Basic and Diluted $ (0.62 ) $ (1.91 ) 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: March 31, 2019 March 31, 2018 Preferred Shares — 9,361,167 Restricted ordinary shares subject to forfeiture 544,312 37,270 Share options 3,312,365 1,614,346 Warrants — 927,594 3,856,677 11,940,377

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	7. Income Taxes The Company did not record a provision for income taxes for the three-month periods ended March 31, 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 March 31, 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.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 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. Under the agreement, Janssen paid the Company a non-refundable upfront fee of $100.0 million. Janssen and the Company will collaborate to develop the Company’s current clinical programs in Retinitis Pigmentosa and two genetic forms of Achromatopsia and Janssen has the exclusive right to commercialize these three (3) product candidates (“Clinical IRD Product Candidates”) globally. Pursuant to the Collaboration Agreement, the Company and Janssen also agreed on a research collaboration to develop a pipeline of preclinical inherited retinal disease gene therapy candidates (“Research IRD Product Candidates”). The parties will select and prioritize the Research IRD Product Candidates and Janssen has the right to opt-in for a fee for each of the specified targets (each an “Option Target”) to obtain certain development, manufacturing and commercialization rights for the Research IRD Product Candidates. Unless terminated earlier under certain termination clauses, the Collaboration Agreement will continue in effect, on a product-by-product and country-by-country basis, until such time as the royalty terms expires in such country. The Company has determined enforceable rights exist in the Collaboration Agreement as the termination clauses are substantive termination penalties by way of the non-refundable upfront fee and the reversion of any licensed intellectual property granted to Janssen upon the termination of the agreement. On February 27, 2019, in connection with a private placement, the Company issued 2,898,550 ordinary shares to Johnson & Johnson Innovation – JJDC, Inc. (“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 MeiraGTx. In general, MeiraGTx 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 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 $340,000,000. Research IRD Product Candidates Under the Collaboration Agreement, the Company and Janssen may potentially 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— 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 three months ended March 31, 2019, the Company received a $100.0 million non-refundable upfront fee from Janssen and allocated this amount plus other variable consideration not subject to constraint to each identified performance obligation using a combination of methods allowable under ASC 606. The Company applies the practical expedient in Topic 606 and does not include disclosures regarding amounts for variable consideration allocated to wholly-unsatisfied performance obligations or wholly-unsatisfied distinct goods that form part of a single performance obligation, if any. This variable consideration includes expected reimbursement of research and development costs. During the three months ended March 31, 2019, the Company amortized $784,960 of the related party deferred revenue The Company also recognized $1,037,542, related to the reimbursement of research and development expenses which was recorded as an offset to research and development expenses. As of March 31, 2019, the Company expects to recognize the remaining $99,215,040 in deferred revenue associated with the non-refundable upfront fee over the estimated research and development period using the cost-to-cost input method over an estimated period of approximately 7.75 years. 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 research funding. The stage 1 fee is being amortized over the estimated research term of eight months. During the three months ended March 31, 2019, the Company amortized $238,473 of the deferred research funding, which was recorded as an offset to research and development expenses. Deferred research funding in the amount of $195,618 is included as other current liabilities on the condensed consolidated balance sheet at March 31, 2019. Research Agreement Effective October 23, 2016, the Company entered into a four-year master services agreement with UCL Consultants Limited, an entity affiliated with University College of London (“UCL”), which is a shareholder of the Company. Pursuant to the agreement, UCL Consultants Limited provides pre-clinical Total research and development expenses under this agreement for the three-month periods ended March 31, 2019 and 2018 were approximately $88,000 and $189,000, respectively. Future obligations, under the agreement equal £240,093, or approximately $313,000, through October 2020. The amount due to UCL under the master services agreement at March 31, 2019 and December 31, 2018 is $465,724 and $389,101, respectively, and is included in accounts payable and accrued expenses on the condensed consolidated balance sheets. License Agreement Effective March 15, 2018, the Company entered into an exclusive worldwide license agreement with UCL Business, PLC (“UCL Business”), to develop up to eight programs using certain ocular gene therapy technology. Under the terms of the agreement, the Company had agreed to pay UCL Business certain sales milestone payments, if achieved, in the aggregate amount of £39.8 million, or approximately $51.9 million using the exchange rate at March 31, 2019, and royalties on net sales, as defined upon commercialization. Additionally, the Company is responsible for all patent prosecution and maintenance costs incurred and has also agreed to pay UCL Business an annual maintenance fee of £50,000, or approximately $65,000, until the first commercial sale of a product. The agreement terminated upon the later of (i) the last valid claim in a relevant product, (ii) the expiration of regulatory exclusivity to all licensed products, or (iii) the 10 th On 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. Each of the stand-alone agreements now reflects terms substantially similar to those of the March 15, 2018 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 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 $79,739 during the three-month periods ended March 31, 2019 and 2018, respectively. Leases ARE Lease Effective July 1, 2016, the Company entered into a non-cancellable right-of-use Total rent expense under this operating lease was $121,888 and $121,890 for the three-month periods ended March 31, 2019 and 2018, respectively. As of March 31, 2019, the aggregate future minimum rental payments under this lease are $1,532,335. 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 expires on July 7, 2017 and is automatically renewed annually through July 7, 2021. This standby letter of credit is secured with restricted cash in a money market account. The aggregate future minimum rental payments under this lease as of March 31, 2019 are as follow: 2019 $ 404,066 2020 554,432 2021 573,837 Total future rent payments $ 1,532,335 Kadmon Lease The Company is currently leasing office space on a month to month basis from Kadmon. During the three-month periods ended March 31, 2019 and 2018, the Company incurred the following charges from Kadmon, which are included in loss from operations: 2019 2018 Rent $ 140,793 $ 136,353 Personnel — 6,493 Total charges incurred $ 140,793 $ 142,846 During the three-month periods ended March 31, 2019 and 2018, the Company made cash payments totaling $140,793 and $997,417, respectively, to Kadmon. The were no amounts due to Kadmon at March 31, 2019 and December 31, 2018.

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases	9. Leases We account for leases in accordance with ASC Topic 842, Leases 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 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 March 31, 2019, we have short term lease commitments amounting to approximately $20,000 on a monthly basis for two leases for office space that are month-to-month The components of lease cost for the quarter ended March 31, 2019 are as follows: Three Months 31, 2019 Finance lease cost Amortization of right-of-use $ 85,415 Interest on lease liabilities 553 85,968 Operating lease cost 6,625 Short-term lease cost 128,485 Total lease cost $ 221,078 Amounts reported in the condensed consolidated balance sheets for leases where we are the lessee as of the quarter ended March 31, 2019 were as follows: March 31, 2019 Operating leases Right-of-Use $ 3,371,149 Lease Obligations $ 3,562,686 Finance leases Right-of-Use Asset $ 7,262,218 Lease Obligations $ 27,670 Weighted-average remaining lease term Operating leases 6.4 years Finance leases 107.8 year Weighted-average discount rate Operating leases 8.0 % Finance leases 6.9 % Other information related to leases as of the quarter ended March 31, 2019 are as follows: Three Months 31, 2019 Cash paid for amounts included in the measurement of lease obligations Operating cash flows from finance leases $ 6,625 Operating cash flows from operating leases 221,278 Financing cash flows from finance leases 553 Right-of-use Operating leases $ 3,371,149 Finance leases — Future minimum lease payments under non-cancellable Operating Leases Finance Leases 2019 $ 673,048 $ 21,536 2020 913,075 7,097 2021 932,480 — 2022 358,643 — 2023 358,643 — Thereafter 1,225,365 — Total undiscounted lease payments $ 4,461,254 $ 28,633 Less: Imputed interest (898,568 ) (963 ) Total lease obligations $ 3,562,686 $ 27,670

Commitments

Commitments	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments	10. Commitments: There were no new material commitments entered into during the three months ended March 31, 2019.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	11. Subsequent Events: 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)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Liquidity	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 March 31, 2019 totaled $166,271,635, 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 quarter ended March 31, 2019, the Company generated $82,165,990 of positive cash flows from operations. However, prior to the quarter ended March 31, 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 March 31, 2019, the Company had cash and cash equivalents in the amount of $227,275,139, 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 March 31, 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.
The Company	The Company MeiraGTx Holdings plc and subsidiaries (the “Company” or “Meira Holdings”), a limited company 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 no effective treatments available. The Company is focused on developing therapies for ocular diseases, including rare inherited blindness as well as Xerostomia following radiation treatment for head and neck cancers and neurodegenerative diseases such as amyothrophic lateral sclerosis (“ALS”) and Parkinson’s disease (“PD”).
Basis of Presentation	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	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 S-X. 10-K 10-K”).
Risks and Uncertainties	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 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.
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 (“Meira Limited); MeiraGTx, LLC, a Delaware corporation (“Meira LLC”); BRI-Alzan, (“BRI-Alzan”); MeiraGTx B.V., a Netherlands corporation (“Meira BV”); MeiraGTx Neurosciences, Inc., a Delaware corporation (“Meira Neuro”); MeiraGTx UK II Limited, (“Meira UK II”), a limited company under the laws of England and Wales; and MeiraGTx UK Limited (“Meira UK”), 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 March 31, Significant Significant Other Significant Restricted cash $ 123,376 $ 123,376 $ — $ — Fair Value Measurement Using: Description December 31, Significant Significant Other Significant Restricted cash $ 123,376 $ 123,376 $ — $ —
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: March 31, 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 2,639 (38,301 ) Change in estimate — (99,090 ) Effects of exchange rate 3,058 17,805 Balance at end of period $ 133,816 $ 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 manufacture 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 Agreements.
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, Collaborative Arrangements Revenue from Contracts with Customers 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, non-current. The Company’s collaboration revenue arrangement includes 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 50% to 100%, 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. The reimbursement of the research and development costs by Janssen is representative of the joint risk sharing nature of the arrangement. The Company considered the guidance is ASC 808 and will recognize the payments received from Janssen as a reduction to research and development expense when the related costs are incurred. For the three months ended March 31, 2019, the Company recognized the reimbursement to be received from Janssen in the amount of $1,037,542.
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 March 31, 2019 December 31, 2018 United States $ 1,643,688 $ 454,568 United Kingdom 25,052,933 21,788,130 $ 26,696,621 $ 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 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
Recent Accounting Pronouncements Not Yet Adopted	Recent Accounting Pronouncements Not Yet Adopted In August 2018, the FASB issued ASU 2018-13, Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurements, In November 2018, the FASB issued ASU No. 2018-18, Clarifying the Interaction between Topic 808 and Topic 606 2018-18”). Collaborative Agreements and Accounting Standards Codification 606, Revenue from Contracts with Customers 2018-18 are 2018-18,

Summary of Significant Accoun_3

Summary of Significant Accounting Policies and Recent Accounting Pronouncements (Tables)	3 Months Ended
	Mar. 31, 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 March 31, Significant Significant Other Significant Restricted cash $ 123,376 $ 123,376 $ — $ — Fair Value Measurement Using: Description December 31, Significant Significant Other Significant Restricted cash $ 123,376 $ 123,376 $ — $ —
Schedule of change in asset retirement obligations	The change in asset retirement obligations is as follows: March 31, 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 2,639 (38,301 ) Change in estimate — (99,090 ) Effects of exchange rate 3,058 17,805 Balance at end of period $ 133,816 $ 128,119
Summary of Non-Current Assets by Geographical Area	The following table summarizes non-current March 31, 2019 December 31, 2018 United States $ 1,643,688 $ 454,568 United Kingdom 25,052,933 21,788,130 $ 26,696,621 $ 22,242,698

Accrued Expenses (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2019
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses for the periods presented are comprised of the following: March 31, 2019 December 31, 2018 Clinical Trial Costs $ 4,705,140 $ 4,013,094 Consulting 1,297,704 821,009 Professional Fees 909,668 914,540 Compensation and Benefits 323,111 5,731,438 Research and Development 286,230 236,271 Rent 217,899 122,770 Interest 47,180 40,800 Other 209,397 111,775 $ 7,996,329 $ 11,991,697

Share-Based Compensation (Table

Share-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 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 Number of Options Weighted- Aggregate Outstanding at December 31, 2018 3,262,365 $ 7.64 $ 6,903,313 Granted 50,000 9.64 Exercised — — Expired — — Forfeited — — Outstanding at March 31, 2019 3,312,365 $ 7.72 $ 32,004,958 Weighted average remaining contractual life of options outstanding as of December 31, 2018 (yrs) 9.24 Weighted average remaining contractual life of options outstanding as of March 31, 2019 (yrs) 9.64 Options exercisable at December 31, 2018 535,241 $ 5.79 Options exercisable at March 31, 2019 857,791 $ 5.68 Weighted average remaining contractual life of options exercisable as of December 31, 2018 (yrs) 7.88 Weighted average remaining contractual life of options exercisable as of March 31, 2019 (yrs) 8.02
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 2.51% 2.76% - 2.81% Expected volatility 90% 90% Expected dividend yield 0% 0% Expected life (in years) 5.5 - 10.0 7.9 - 9.8
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 three-month period ended March 31, 2019 (108,862 ) (1,632,930 ) Non-vested 544,312 $ 8,164,680
Schedule of Share Based Compensation Expense	During the three-month periods ended March 31, 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 March 31, 2019 2018 Research and development $ 834,314 $ 842,961 General and administrative 2,100,677 3,432,774 Total share based compensation $ 2,934,991 $ 4,275,735

Net Loss per Share (Tables)

Net Loss per Share (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2019 2018 Net loss—basic and diluted $ (17,981,918 ) $ (16,403,353 ) Accretion of Preferred Shares financing costs — (94,445 ) Accretion of warrant — (570,273 ) Adjusted net loss—basic and diluted $ (17,981,918 ) $ (17,068,071 ) Weighted-average ordinary shares outstanding: Basic and Diluted 28,776,915 8,927,433 Adjusted net loss per ordinary share: Basic and Diluted $ (0.62 ) $ (1.91 )
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: March 31, 2019 March 31, 2018 Preferred Shares — 9,361,167 Restricted ordinary shares subject to forfeiture 544,312 37,270 Share options 3,312,365 1,614,346 Warrants — 927,594 3,856,677 11,940,377

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
	Mar. 31, 2019
Incurred Charges Included in Loss from Operations	During the three-month periods ended March 31, 2019 and 2018, the Company incurred the following charges from Kadmon, which are included in loss from operations: 2019 2018 Rent $ 140,793 $ 136,353 Personnel — 6,493 Total charges incurred $ 140,793 $ 142,846
July 2016 Lease [Member]
Schedule of Future Minimum Rental Payments	The aggregate future minimum rental payments under this lease as of March 31, 2019 are as follow: 2019 $ 404,066 2020 554,432 2021 573,837 Total future rent payments $ 1,532,335

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Schedule of Components of Lease Cost	The components of lease cost for the quarter ended March 31, 2019 are as follows: Three Months 31, 2019 Finance lease cost Amortization of right-of-use $ 85,415 Interest on lease liabilities 553 85,968 Operating lease cost 6,625 Short-term lease cost 128,485 Total lease cost $ 221,078
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 quarter ended March 31, 2019 were as follows: March 31, 2019 Operating leases Right-of-Use $ 3,371,149 Lease Obligations $ 3,562,686 Finance leases Right-of-Use Asset $ 7,262,218 Lease Obligations $ 27,670 Weighted-average remaining lease term Operating leases 6.4 years Finance leases 107.8 year Weighted-average discount rate Operating leases 8.0 % Finance leases 6.9 %
Schedule of Other Information Related to Leases	Other information related to leases as of the quarter ended March 31, 2019 are as follows: Three Months 31, 2019 Cash paid for amounts included in the measurement of lease obligations Operating cash flows from finance leases $ 6,625 Operating cash flows from operating leases 221,278 Financing cash flows from finance leases 553 Right-of-use Operating leases $ 3,371,149 Finance leases —
Schedule of Future Minimum Lease Payments Under Non-cancellable Leases	Future minimum lease payments under non-cancellable Operating Leases Finance Leases 2019 $ 673,048 $ 21,536 2020 913,075 7,097 2021 932,480 — 2022 358,643 — 2023 358,643 — Thereafter 1,225,365 — Total undiscounted lease payments $ 4,461,254 $ 28,633 Less: Imputed interest (898,568 ) (963 ) Total lease obligations $ 3,562,686 $ 27,670

Organization and Basis of Pre_2

Organization and Basis of Presentation - Additional Information (Detail) - USD ($)	Jan. 30, 2019	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Schedule Of Description Of Business [Line Items]
Accumulated deficit		$ (166,271,635)		$ (148,289,717)
Cash flows from operations		82,165,990	$ (17,395,969)
Cash and cash equivalents		227,275,139		$ 68,080,175
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
Collaboration Option And License Agreement [Member] | Minimum [Member] | JJDC [Member]
Schedule Of Description Of Business [Line Items]
Offsetting expense, period		12 months

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] - Restricted Cash [Member] - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, net asset (liability)	$ 123,376	$ 123,376
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, net asset (liability)	$ 123,376	$ 123,376

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Change in Asset Retirement Obligations (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 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	2,639	$ 3,678	(38,301)
Change in estimate			(99,090)
Effects of exchange rate	3,058		17,805
Balance at end of period	$ 133,816		$ 128,119

Summary of Significant Accoun_6

Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Additional Information (Detail) - USD ($)	Jan. 01, 2019	Mar. 31, 2019
Discount rate	8.00%
Right-of-use asset	$ 10,836,319	$ 10,606,985
Lease obligation	3,716,336
Reclassification from property and equipment of fully paid lease	$ 7,321,251
Janssen Pharmaceuticals Inc [Member]
Reimbursement of revenue recognized to be received		$ 1,037,542
Janssen Pharmaceuticals Inc [Member] | Minimum [Member]
Percentage of costs payable on annual net sales of licensed product statement		50.00%
Janssen Pharmaceuticals Inc [Member] | Maximum [Member]
Percentage of costs payable on annual net sales of licensed product statement		100.00%

Summary of Significant Accoun_7

Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Summary of Non-Current Assets by Geographical Area (Detail) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Operation By Geographical [Line Items]
Non current assets	$ 26,696,621	$ 22,242,698
United States
Operation By Geographical [Line Items]
Non current assets	1,643,688	454,568
United Kingdom
Operation By Geographical [Line Items]
Non current assets	$ 25,052,933	$ 21,788,130

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Clinical Trial Costs	$ 4,705,140	$ 4,013,094
Consulting	1,297,704	821,009
Professional Fees	909,668	914,540
Compensation and Benefits	323,111	5,731,438
Research and Development	286,230	236,271
Rent	217,899	122,770
Interest	47,180	40,800
Other	209,397	111,775
Accrued expenses	$ 7,996,329	$ 11,991,697

Share based Compensation - Addi

Share based Compensation - Additional Information (Detail) - USD ($)	Jun. 07, 2018	Mar. 01, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average remaining contractual life of options outstanding			9 years 7 months 20 days		9 years 2 months 26 days
Fair value of options Vested			$ 1,390,942	$ 309,147
Share options granted during the period			50,000
Share based compensation			$ 2,934,991	4,275,735
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			$ 3,772,650
Restricted Shares [Member] | General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation			$ 1,632,930
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]
Share options granted during the period			50,000	533,358
Total unvested options compensation expense			$ 16,550,086
Unvested options expected to be realized			4 years
Weighted average grant date fair value of options granted			$ 9.64	$ 4.35
Consultant [Member] | Restricted Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares awarded, per share				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
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) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of options, Beginning balance	3,262,365
Number of options, Granted	50,000
Number of options, Exercised	0
Number of options, Expired	0
Number of options, Forfeited	0
Number of options, Ending balance	3,312,365	3,262,365
Weighted average remaining contractual life of options outstanding	9 years 7 months 20 days	9 years 2 months 26 days
Number of options, Options exercisable	857,791	535,241
Weighted average remaining contractual life of options exercisable	8 years 7 days	7 years 10 months 17 days
Weighted- average exercise price, beginning balance	$ 7.64
Weighted- average exercise price, granted	9.64
Weighted- average exercise price, exercised	0
Weighted- average exercise price, expired	0
Weighted- average exercise price, forfeited	0
Weighted- average exercise price, ending balance	7.72	$ 7.64
Weighted- average exercise price, option exercisable	$ 5.68	$ 5.79
Aggregate Intrinsic Value	$ 32,004,958	$ 6,903,313
Aggregate Intrinsic Value, Options Exercisable	$ 0	$ 0

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]	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.51%	2.76%
Risk-free interest rate		2.81%
Expected volatility	90.00%	90.00%
Expected dividend yield	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of non-employee options (in years)	5 years 6 months	7 years 10 months 24 days
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of non-employee options (in years)	10 years	9 years 9 months 18 days

Share Based Compensation - Su_2

Share Based Compensation - Summary of Restricted Ordinary Shares (Detail) - Restricted Shares [Member]	3 Months Ended
	Mar. 31, 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	(108,862)
Non-vested Ordinary Shares, Ending Balance | shares	544,312
Non-vested Value, Beginning Balance | $	$ 9,797,610
Vested, Value | $	(1,632,930)
Non-vested Value, Ending Balance | $	$ 8,164,680

Share Based Compensation - Sc_2

Share Based Compensation - Schedule of Share Based Compensation Expense (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share Based Compensation Expense [Line Items]
Total share based compensation	$ 2,934,991	$ 4,275,735
Research and Development Expenses [Member]
Share Based Compensation Expense [Line Items]
Total share based compensation	834,314	842,961
General and Administrative Expense [Member]
Share Based Compensation Expense [Line Items]
Total share based compensation	$ 2,100,677	$ 3,432,774

Ordinary Shares - Additional In

Ordinary Shares - Additional Information (Detail) - USD ($) $ in Millions	Jul. 31, 2019	Mar. 21, 2019	Feb. 27, 2019	Mar. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Common stock, shares issued				33,342,566	27,386,632
Private Placement [Member]
Class of Stock [Line Items]
Common stock, shares issued			5,797,102
Proceeds from issuance of private placement			$ 80
Offering costs			$ 2.4
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
Scenario, Forecast [Member] | Private Placement [Member]
Class of Stock [Line Items]
Registration Payment Arrangement Liquidated Damages Percent	1.00%

Net Loss per Share - Schedule o

Net Loss per Share - Schedule of Basic and Diluted Net Loss per Share (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net loss-basic and diluted	$ (17,981,918)	$ (16,403,353)
Accretion of Preferred Shares financing costs		(94,445)
Accretion of warrant		(570,273)
Adjusted net loss-basic and diluted	$ (17,981,918)	$ (17,068,071)
Weighted-average ordinary shares outstanding:
Basic and Diluted	28,776,915	8,927,433
Adjusted net loss per ordinary share:
Basic and Diluted	$ (0.62)	$ (1.91)

Net Loss per Share - Schedule_2

Net Loss per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings per Share (Detail) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earning per share, amount	3,856,677	11,940,377
Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earning per share, amount		9,361,167
Restricted Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earning per share, amount	544,312	37,270
Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earning per share, amount	3,312,365	1,614,346
Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earning per share, amount		927,594

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Provision for Income Taxes	$ 0	$ 0

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail)	Jan. 30, 2019USD ($)	Mar. 15, 2018Program	Mar. 31, 2019GBP (£)shares	Mar. 31, 2019USD ($)shares	Mar. 31, 2018USD ($)	Oct. 31, 2020GBP (£)	Oct. 31, 2020USD ($)	Mar. 31, 2019USD ($)shares	Feb. 27, 2019shares	Dec. 31, 2018USD ($)shares	Jul. 27, 2018USD ($)
Related Party Transaction [Line Items]
Common stock, shares issued | shares			33,342,566					33,342,566		27,386,632
License revenue - related party				$ 784,960
Research and development expenses				12,976,229	$ 6,927,322
Amount due under services agreement								$ 0		$ 0
Issuance of ordinary shares in connection with a license agreement				1,966,340
Janssen Pharmaceuticals Inc [Member]
Related Party Transaction [Line Items]
Revenue recognized				$ 1,037,542
Collaboration Agreement [Member] | Janssen Pharmaceuticals Inc [Member]
Related Party Transaction [Line Items]
Deferred research funding								658,667
Deferred research funding, amortization period			8 months	8 months
Collaboration Agreement [Member] | Janssen Pharmaceuticals Inc [Member] | Research and Development Expenses [Member]
Related Party Transaction [Line Items]
Amortized of deferred research funding				$ 238,473
Collaboration Agreement [Member] | Janssen Pharmaceuticals Inc [Member] | Other Current Liabilities [Member]
Related Party Transaction [Line Items]
Deferred research funding								195,618
Transition Services Agreement with Related Party [Member] | Kadmon [Member]
Related Party Transaction [Line Items]
Cash payment				140,793	997,417
License Agreement [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			£ 1,500,000	$ 1,976,000
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			£ 1,500,000	$ 1,966,000
Payments for research and development expenses agreement				4,111,876	79,739
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				784,960
Revenue recognized				$ 1,037,542
Deferred revenue associated with the non-refundable upfront fee, expected to be recognized								99,215,040
Deferred revenue associated with the non-refundable upfront fee, expected to be recognition period			7 years 9 months	7 years 9 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								191,531		201,264
Operating lease rent expenses				$ 121,888	121,890
Aggregate future minimum rental payments under operating lease								1,532,335			$ 1,532,335
Letter of credit outstanding amount								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				$ 88,000	$ 189,000
Amount due under services agreement								465,724		$ 389,101
UCL Consultants Limited [Member] | Scenario, Forecast [Member] | Research Agreement [Member]
Related Party Transaction [Line Items]
Future obligations under agreement						£ 240,093	$ 313,000
UCL Business, PLC [Member] | License Agreements Effective March 15, 2018 [Member] | License Agreement [Member]
Related Party Transaction [Line Items]
Number of collaborations programs | Program		8
Sales milestone payments			£ 39,800,000					$ 51,900,000
Maintenance fee			£ 50,000	$ 65,000

Related Party Transactions - Sc

Related Party Transactions - Schedule of Future Minimum Rental Payments (Detail) - July 2016 Lease [Member] - USD ($)	Mar. 31, 2019	Jul. 27, 2018
Related Party Transaction [Line Items]
2019		$ 404,066
2020		554,432
2021		573,837
Total future rent payments	$ 1,532,335	$ 1,532,335

Related Party Transactions - In

Related Party Transactions - Incurred Charges included in Loss from Operations (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Related Party Transaction [Line Items]
Total charges incurred	$ 140,793	$ 142,846
Rent [Member]
Related Party Transaction [Line Items]
Total charges incurred	$ 140,793	136,353
Personnel [Member]
Related Party Transaction [Line Items]
Total charges incurred		$ 6,493

Leases - Additional Information

Leases - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2019USD ($)
Lessee, Lease, Description [Line Items]
Short term lease commitments	$ 20,000
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)	3 Months Ended
	Mar. 31, 2019USD ($)
Finance lease cost
Amortization of right-of-use assets	$ 85,415
Interest on lease liabilities	553
Finance lease cost	85,968
Operating lease cost	6,625
Short-term lease cost	128,485
Total lease cost	$ 221,078

Leases - Schedule of Condensed

Leases - Schedule of Condensed Consolidated Balance Sheets for Leases (Detail)	Mar. 31, 2019USD ($)
Operating leases
Right-of-Use Asset	$ 3,371,149
Lease Obligations	3,562,686
Finance leases
Right-of-Use Asset	7,262,218
Lease Obligations	$ 27,670
Weighted-average remaining lease term
Operating leases	6 years 4 months 24 days
Finance leases	107 years 9 months 18 days
Weighted-average discount rate
Operating leases	8.00%
Finance leases	6.90%

Leases - Schedule of Other Info

Leases - Schedule of Other Information Related to Leases (Detail)	3 Months Ended
	Mar. 31, 2019USD ($)
Cash paid for amounts included in the measurement of lease obligations
Operating cash flows from finance leases	$ 6,625
Operating cash flows from operating leases	221,278
Financing cash flows from finance leases	553
Right-of-use assets obtained in exchange for lease obligations
Operating leases	3,371,149
Finance leases	$ 0

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Lease Payments Under Non-cancellable Leases (Detail)	Mar. 31, 2019USD ($)
Operating Leases
2019	$ 673,048
2020	913,075
2021	932,480
2022	358,643
2023	358,643
Thereafter	1,225,365
Total undiscounted lease payments	4,461,254
Less: Imputed interest	(898,568)
Total lease obligations	3,562,686
Finance Leases
2019	21,536
2020	7,097
2021	0
2022	0
2023	0
Thereafter	0
Total undiscounted lease payments	28,633
Less: Imputed interest	(963)
Total lease obligations	$ 27,670