Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2018	Mar. 15, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Trading Symbol	MGTX
Entity Registrant Name	MeiraGTx Holdings plc
Entity Central Index Key	0001735438
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		33,183,734
Entity Public Float			$ 154.6

CONSOLIDATED BALANCE SHEETS - USD ($)	Dec. 31, 2018	Dec. 31, 2017
CURRENT ASSETS:
Cash and cash equivalents	$ 68,080,175	$ 8,548,638
Prepaid expenses	1,937,785	1,961,243
Other current assets	4,634,105	965,233
Total Current Assets	74,652,065	11,475,114
Property, plant and equipment, net	22,014,237	14,255,729
Security deposits	105,085
Restricted cash	123,376	123,376
TOTAL ASSETS	96,894,763	25,854,219
CURRENT LIABILITIES:
Accounts payable	3,042,861	7,055,380
Accrued expenses	11,991,697	9,332,944
Note payable		1,442,009
Warrant liability		2,679,633
Capitalized lease obligation-current portion	27,199	30,850
Due to Kadmon	0	861,030
Other current liabilities	437,053
Total Current Liabilities	15,498,810	21,401,846
Capitalized lease obligation	7,097	34,298
Deferred rent	201,264	266,290
Asset retirement obligation	128,119	178,419
TOTAL LIABILITIES	15,835,290	21,880,853
COMMITMENTS
Convertible Preferred C Shares 0 and 5,005,935 outstanding at December 31, 2018 and December 31, 2017, respectively (liquidation preference of $52,455,700 at December 31, 2017)		51,338,631
SHAREHOLDERS' EQUITY (DEFICIT):
Ordinary Shares, $0.00003881 nominal value, 1,288,327,750 authorized 27,386,632 issued and outstanding at December 31, 2018 8,826,190 issued and 8,714,563 issued and outstanding at December 31, 2017	1,064	342
Capital in excess of nominal value	229,054,460	20,080,713
Accumulated other comprehensive income (loss)	293,666	(2,022,477)
Accumulated deficit	(148,289,717)	(65,423,843)
Total Shareholders' Equity (Deficit)	81,059,473	(47,365,265)
TOTAL LIABILITIES, CONVERTIBLE PREFERRED C SHARES AND SHAREHOLDERS' EQUITY (DEFICIT)	$ 96,894,763	$ 25,854,219

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred Stock, Shares Outstanding	0	5,005,935
Preferred Stock, Liquidation Preference, Value		$ 52,455,700
Common stock, par value	$ 0.00003881	$ 0.00003881
Common stock, shares authorized	1,288,327,750	1,288,327,750
Common stock, shares issued	27,386,632	8,826,190
Common stock, shares outstanding	27,386,632	8,714,563

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating expenses:
General and administrative	$ 44,483,938	$ 9,325,017
Research and development	33,620,223	22,359,712
Total operating expenses	78,104,161	31,684,729
Loss from operations	(78,104,161)	(31,684,729)
Other non-operating income (expense):
Other income	83,075
Foreign currency (loss) gain	(3,824,383)	1,676,117
Convertible note inducement expense		(553,500)
Change in fair value of warrant liability	(1,514,775)	(465,633)
Interest income	53,408	26,073
Interest expense	(33,429)	(42,863)
Loss before income taxes	(83,340,265)	(31,044,535)
Benefit for income taxes	474,391	0
Net loss	(82,865,874)	(31,044,535)
Other comprehensive income (loss):
Foreign currency translation, net of tax of $474,391 and $0 in 2018 and 2017, respectively	2,316,143	(1,361,365)
Total comprehensive loss	(80,549,731)	(32,405,900)
Net loss	(82,865,874)	(31,044,535)
Accretion on convertible preferred C shares and warrants	(1,806,512)	(806,963)
Adjusted net loss	$ (84,672,386)	$ (31,851,498)
Basic and diluted net loss per ordinary share	$ (4.47)	$ (3.72)
Weighted-average number of ordinary shares outstanding	18,948,520	8,572,315

CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED C SHARES AND SHAREHOLDERS' EQUITY (DEFICIT) - USD ($)	Total	Vector Neurosciences Acquisition [Member]	IPO [Member]	Ordinary shares [Member]	Ordinary shares [Member] Vector Neurosciences Acquisition [Member]	Ordinary shares [Member] IPO [Member]	Capital in Excess of Nominal Value [Member]	Capital in Excess of Nominal Value [Member] Vector Neurosciences Acquisition [Member]	Capital in Excess of Nominal Value [Member] IPO [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Convertible Preferred C Shares [Member]	Convertible Preferred C Shares [Member] Accounts Payable [Member]	Convertible Preferred C Shares [Member] License Agreement [Member]	Convertible Preferred C Shares [Member] Sales Agreement [Member]
Temporary equity, beginning Balance at Dec. 31, 2016												$ 32,833,660
Beginning Balance at Dec. 31, 2016	$ (17,139,083)			$ 342			$ 17,900,995			$ (661,112)	$ (34,379,308)
Temporary equity, beginning Balance, Shares at Dec. 31, 2016												1,574,739
Beginning Balance, Shares at Dec. 31, 2016				8,818,461
Exercised stock options	$ 9,950						9,950
Exercised stock options, shares	1,288			1,288
Issuance of A ordinary shares in connection with a license agreement	$ 17,000						17,000
Issuance of A ordinary shares in connection with a license agreement, shares				6,441
Extinguishment of convertible preferred C shares, net of unaccreted issuance costs	33,115,157						33,115,157					$ (33,115,157)
Extinguishment of convertible preferred C shares, net of unaccreted issuance costs, shares												(1,584,469)
Issuance of convertible preferred C shares in connection with extinguishment	(33,206,360)						(33,206,360)					$ 33,206,360
Issuance of convertible preferred C shares in connection with extinguishment, shares												3,168,929
Conversion of convertible preferred C shares into A ordinary shares												$ 2,500,000
Conversion of convertible preferred C shares into A ordinary shares, shares												238,579
Issuance of convertible preferred C shares, net of warrants and issuance costs												$ 15,198,008
Issuance of convertible preferred C shares, net of warrants and issuance costs, shares												1,608,157
Accretion of issuance costs on convertible preferred C shares	(100,760)						(100,760)
Accretion of warrants issued in connection with convertible preferred C shares	(615,000)						(615,000)
Accretion of issuance costs on convertible preferred C shares												$ 100,760
Accretion of warrants issued in connection with convertible preferred C shares												615,000
Share-based compensation	2,959,731						2,959,731
Foreign currency translation, net of income taxes	(1,361,365)									(1,361,365)
Net loss	(31,044,535)										(31,044,535)
Temporary equity, beginning Balance at Dec. 31, 2017												$ 51,338,631
Ending Balance at Dec. 31, 2017	$ (47,365,265)			$ 342			20,080,713			(2,022,477)	(65,423,843)
Temporary equity, beginning Balance, Shares at Dec. 31, 2017	5,005,935											5,005,935
Ending Balance, Shares at Dec. 31, 2017				8,826,190
Issuance of convertible preferred C shares, net of issuance costs													$ 1,356,129	$ 140,000	$ 56,159,119
Sale of ordinary shares in initial public offering, net of issuance costs			$ 65,192,378			$ 194			$ 65,192,184
Issuance of shares, net of issuance costs, shares						5,000,000							129,419	13,360	5,425,124
Conversion of convertible preferred C shares into A ordinary shares	$ 120,520,391			$ 446			120,519,945					$ (120,520,391)
Conversion of convertible preferred C shares into A ordinary shares, shares				11,501,432								(11,501,432)
Accretion of issuance costs on convertible preferred C shares	(761,012)						(761,012)
Accretion of warrants issued in connection with convertible preferred C shares	(1,045,500)						(1,045,500)
Accretion of issuance costs on convertible preferred C shares												$ 761,012
Accretion of warrants issued in connection with convertible preferred C shares												1,045,500
Exercise of warrants	4,194,408						4,194,408					$ 9,720,000
Exercise of warrants, Share												927,594
Issuance of ordinary shares in connection with Vector Neurosciences acquisition		$ 2,990,250			$ 9			$ 2,990,241
Issuance of ordinary shares in connection with Vector Neurosciences acquisition, Shares					202,500
Share-based compensation	17,883,554			$ 73			17,883,481
Share-based compensation, Shares				1,856,510
Foreign currency translation, net of income taxes	2,316,143									2,316,143
Net loss	(82,865,874)										(82,865,874)
Ending Balance at Dec. 31, 2018	$ 81,059,473			$ 1,064			$ 229,054,460			$ 293,666	$ (148,289,717)
Temporary equity, beginning Balance, Shares at Dec. 31, 2018	0
Ending Balance, Shares at Dec. 31, 2018				27,386,632

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss	$ (82,865,874)	$ (31,044,535)
Adjustments to reconcile net loss to net cash used in operating activities:
Preferred C shares issued in connection with a license agreement	140,000
Issuance of shares for services		17,000
Share-based compensation expense	17,883,554	2,959,731
Foreign currency loss (gain)	3,824,383	(1,676,117)
Depreciation	2,053,220	679,177
Amortization of interest on asset retirement obligation	(38,301)	19,313
Change in fair value of warrant liability	1,514,775	465,633
Convertible note inducement expense		553,500
Issuance of shares for acquired research and development expense	2,990,250
Issuance of note payable in connection with lease termination		1,442,009
Benefit for income taxes	(474,391)	0
(Increase) in operating assets:
Prepaid expenses	(35,465)	(669,756)
Other current assets	(3,684,465)	(493,424)
Security deposits	(115,573)
Increase (decrease) in operating liabilities:
Accounts payable	(2,119,493)	4,728,491
Accrued expenses	2,529,568	4,969,619
Due to Kadmon	(861,030)	317,992
Other liabilities	436,161
Deferred rent	(65,189)	(324,019)
Net cash used in operating activities	(58,887,870)	(18,055,386)
Cash flows from investing activities:
Purchase of property, plant and equipment	(11,258,479)	(10,535,717)
Net cash used in investing activities	(11,258,479)	(10,535,717)
Cash flows from financing activities:
Payments on capitalized lease obligation	(30,852)	(24,388)
Exercise of warrants	9,720,000
Proceeds from the sale of ordinary shares	69,750,000
Proceeds from the sale of convertible preferred C shares	56,849,594	16,854,653
(Payment) issuance of note payable	(1,442,009)	2,500,000
Proceeds from excercised stock options		9,950
Net cash provided by financing activities	130,040,415	19,340,215
Net increase (decrease) in cash, cash equivalents and restricted cash	59,894,066	(9,250,888)
Effect of exchange rate changes on cash	(362,529)	1,417
Cash, cash equivalents and restricted cash at beginning of year	8,672,014	17,921,485
Cash, cash equivalents and restricted cash at end of year	68,203,551	8,672,014
Supplemental disclosure of non-cash transactions:
Fixed asset acquisition included in accounts payable and accrued expenses at end of year	293,051	415,650
Issuance of convertible preferred C shares in connection with payables	1,356,129
Conversion of convertible preferred C shares into ordinary shares	120,520,391
Reclassification of warrant liability upon exercise of warrants	4,194,408
Capitalized lease obligation for equipment purchase		78,063
Asset retirement obligation in connection with a lease	(29,804)	(75,011)
Supplemental disclosure of cash flow information:
Cash paid for interest	34,546	20,894
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 shares	(4,115,843)
Supplemental disclosure of non-cash transactions:
Issuance costs in connection with sale of ordinary shares in accounts payable and accrued expenses at end of period	441,779
Convertible Preferred C Shares [Member]
Cash flows from financing activities:
Issuance costs in connection with shares	$ (690,475)
Supplemental disclosure of non-cash transactions:
Conversion of note payable into convertible preferred C shares		$ 2,500,000

Principal Business Activity

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Principal Business Activity

1.	Principal Business Activity:

The Company

MeiraGTx Holdings plc (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”).

Reorganization and Initial Public Offering

We commenced operations as MeiraGTx Limited, a private limited company incorporated under the laws of England and Wales in 2015. On May 28, 2018, the Board of Directors of MeiraGTx Limited approved the Reorganization Transactions, effective June 7, 2018, pursuant to which the Board of Directors approved the transfer of the shares held by each of the MeiraGTx Limited’s shareholders for the equivalent class and number of shares issued by Meira Holdings. On June 7, 2018, the Company completed its initial public offering (“IPO”), selling 5,000,000 ordinary shares (“Ordinary Shares”) at a public offering price of $15.00 per share, and receiving $65.2 million in net proceeds, after deducting underwriting discounts and commissions and offering expenses payable by us.

Reverse Share Split

On June 7, 2018 MeiraGTx Limited’s Board of Directors and shareholders approved a 1:3.881 reverse share split. All share information presented in these financial statements and accompanying footnotes have been retroactively adjusted to reflect the decreased number of shares resulting from this action.

Basis of Presentation

The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”).

Liquidity

The Company has not yet achieved profitable operations. There is no assurance that profitable operations, if ever achieved, could be sustained on a continuing basis. In addition, development activities, clinical and preclinical testing, and commercialization of the Company’s product candidates will require significant additional financing. The Company’s accumulated deficit at December 31, 2018 totaled $(148,289,717), 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. The Company has not generated positive cash flows from operations, and there are no assurances that the Company will be successful in obtaining an adequate level of financing for the development and commercialization of its product candidates.

As of December 31, 2018, the Company had cash and cash equivalents in the amount of $68,080,175, which consisted of depository accounts. On January 30, 2019, the Company entered into a collaboration, option and license agreement with Janssen Pharmaceuticals, Inc., one of the Janssen Pharmaceuticals Companies of Johnson & Johnson (the “Collaboration Agreement”). Under the terms of the Collaboration Agreement, the Company will receive an upfront payment of $100 million. The Company will also receive research 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. On February 27, 2019, the Company issued 5,797,102 ordinary shares in an $80 million private placement led by JJDC, Inc., the investment arm of Johnson & Johnson, (the “Private Placement”) for net proceeds of $77.4 million. The Company estimates that its cash and cash equivalents on hand at December 31, 2018 as well as proceeds from the Collaboration Agreement and the Private Placement will be sufficient to cover its expenses for at least the next twelve months from the date of issuance of these 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 limited capital resources and operations to date have been funded primarily with the proceeds from 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 Accounting Policies

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.	Summary of Significant Accounting Policies:

Consolidation

The accompanying consolidated financial statements include the accounts of Meira Holdings and its wholly owned subsidiaries:

MeiraGTx Limited, a limited company under the laws of England and Wales (“Meira Limited);

MeiraGTx, LLC, a Delaware corporation (“Meira LLC”);

BRI-Alzan, Inc., a Delaware corporation (“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 consolidated financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. This process may result in actual results differing materially from those estimated amounts used in the preparation of the financial statements if these results differ from historical experience, or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made. In preparing these consolidated financial statements, management used significant estimates in the following areas, among others: valuation of A ordinary shares (“A Ordinary Shares”) issued prior to the Company’s initial public offering, the accounting for research and development costs, warrants, share-based compensation and accrued expenses.

Subsequent Events

The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The Company evaluated all events and transactions through March 26, 2019, the date these consolidated financial statements were issued. See Note 18 for additional information.

Cash and Cash Equivalents

The Company considers all highly liquid instruments with an original maturity of 90 days or less at the time of purchase to be cash equivalents. Cash and cash equivalents consist of deposits that are readily convertible into cash.

Warrant Liability

During 2017, the Company issued warrants to purchase Convertible Preferred C Shares (the “Preferred Shares”) to certain investors. Due to the potential redemption feature of the underlying Preferred Shares, the warrants had been classified as a liability. Liability accounting requires that the fair value of warrants be remeasured each reporting period with changes recorded in the statements of operations and comprehensive loss. These Preferred Shares warrants remained outstanding until their exercise in June 2018, at which time the warrant liability was remeasured to fair value and reclassified to additional paid-in capital.

Financial Instruments

The carrying value of prepaid expenses, other current assets, accounts payable, accrued expenses, notes payable and amounts due to an affiliate reported in the consolidated balance sheets equal or approximate fair value due to their short maturities.

Fair Value Measurements

Fair value is defined as the price that would be received upon sale of an asset or paid upon transfer of a liability in an orderly transaction between market participants at the measurement date and in the principal or most advantageous market for that asset or liability. The fair value should be calculated based on assumptions that market participants would use in pricing the asset or liability, not on assumptions specific to the entity. In addition, the fair value of liabilities should include consideration of non-performance risk including our own credit risk.

The Company follows ASC Topic 820, Fair Value Measurements and Disclosures, or ASC 820, for application to financial assets and liabilities. In addition to defining fair value, the standard expands the disclosure requirements around fair value and establishes a fair value hierarchy for valuation inputs. The hierarchy prioritizes the inputs into three levels based on the extent to which inputs used in measuring fair value are observable in the market. Each fair value measurement is reported in one of the three levels which are determined by the lowest level input that is significant to the fair value measurement in its entirety. These levels are:

•

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	December 31, 2018		Significant Observable Inputs (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable (Level 3)
Restricted cash	$	123,376	$	123,376	$	—	$	—


	Fair Value Measurement Using:
Description	December 31, 2017		Significant Observable Inputs (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable (Level 3)
Restricted cash	$	123,376	$	123,376	$	—	$	—

Warrants	$	2,679,633	$	—	$	—	$	2,679,633

The table below represents a rollforward of the assets and liabilities that are required to be measured at fair value on a recurring basis from December 31, 2016 to December 31, 2018:


	Significant Observable Inputs (Level 1)			Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Balance as of December 31, 2016	$	444,844		$	—	$	—
Cash released from restriction		(321,468	)		—		—
Fair value of warrants issued		—			—		2,214,000
Change in fair value of warrants		—			—		465,633

Balance as of December 31, 2017		123,376			—		2,679,633
Change in fair value of warrants							1,514,775
Exercise of warrants		—			—		(4,194,408	)

Balance as of December 31, 2018	$	123,376		$	—	$	—

The warrants were classified as liabilities because the underlying Preferred Shares had a redemption feature in the event of a change of control of the Company. On June 5, 2018, the warrants were exercised at which time the warrant liability was determined to be $4,194,408, which represented the difference in the market value of the Preferred Shares and the exercise price of the warrants. This resulted in an increase of the warrant liability in the amount of $1,514,775 for the year ended December 31, 2018. The related warrant liability of $4,194,408 was reclassified as Capital in Excess of Nominal Value at such time.

The fair values of the warrants were estimated using the Black-Scholes valuation model with the following assumptions:


	June 4, 2018			December 31, 2017			September 21, 2017
Risk-free interest rate		1.77	%		1.72	%		1.38	%
Expected volatility		80	%		80	%		80	%
Expected dividend yield		0			0			0
Expected life		1 day			9 months			18 months

For the unobservable inputs for the warrants, the expected volatility was determined at each measurement date by taking an average of the volatility of other publicly-traded peer biotechnology companies. The expected life was determined at each measurement date based upon the Company’s estimate of the time until the Company has a conversion event, as described in Note 12.

The fair value of the Preferred Shares were based upon recent issuances of the Company’s Preferred Shares on or about those dates.

The estimated fair values of the Company’s warrants were not necessarily indicative of the amounts that would have been realized in a current market exchange. The determination of the fair value of the warrants were sensitive to changes in the assumptions used and a change in those inputs could result in a significantly higher or lower fair value measurement. If the volatility were to increase or the expected life were to increase, the fair value of the warrant would increase. Conversely, if the volatility were to decrease or the expected life were to decrease, the fair value of the warrant would decrease.

Convertible Preferred C Shares

The Preferred Shares were not redeemable, except in the event of a change of control which was outside the control of the Company and required shareholder approval. The redemption value of the Preferred Shares upon a change in control is equal to its liquidation value described below.

The Company is accounting for its Preferred Shares under the requirements of ASC 480, Distinguishing Liabilities from Equity, which establishes standards for how an issuer classifies and measures certain financial instruments with characteristics of both liabilities and equity. The carrying value of the Preferred Shares is presented as temporary equity and is increased by periodic accretions so that the carrying amount will equal the redemption amount at the estimated date that the Preferred Shares will be converted into Ordinary Shares. These increases are affected through charges against additional paid-in capital, to the extent it is available, or accumulated deficit. For all Preferred Shares issuance, the difference between the amount invested by the holders of the Preferred Shares, net of issuance costs and the initial fair value of warrants issued in connection with the Preferred Shares (if applicable), and the liquidation value of the Preferred Shares is recorded as accretion over the estimated life of the Preferred Shares. The accretion is added to net loss to arrive at the net loss available to Ordinary Shareholders in the calculation of loss per Ordinary Share.

Concentrations of Credit Risk

The Company maintains its cash and cash equivalents primarily in depository and money market accounts within two large financial institutions in the United States and one large financial institution in the United Kingdom. Cash balances deposited at these major financial banking institutions exceed the insured limit. The Company has not experienced any losses on its bank deposits and believes these deposits do not expose the Company to any significant credit risk.

Property, Plant and Equipment, Net

Property, plant and equipment are stated at cost, net of accumulated depreciation. Depreciation is calculated using the straight-line method over the estimated useful lives of the respective assets. Leasehold improvements are depreciated over the lesser of their useful lives or the life of the lease (see Note 5).

The estimated useful lives of the asset categories are set forth in the table below:


Asset Category	Useful Lives
Computer and office equipment		3 years
Laboratory equipment		5 years
Manufacturing equipment		7 years
Furniture and fixtures		5 years
Capitalized leasehold interest		25 years
Leasehold improvements		lesser of useful life or remaining term of lease

Expenditures for leasehold improvements are capitalized, and expenditures for maintenance and repairs are expensed to operations as incurred.

ASC Topic 360, Property, Plant and Equipment, addresses the financial accounting and reporting for impairment or disposal of long-lived assets. The Company reviews the recorded values of long-lived assets for impairment whenever events or changes in business circumstances indicate that the carrying amount of an asset or group of assets may not be fully recoverable. The Company recorded no impairment charges in 2018 or 2017.

Net Loss per Ordinary Share

Basic net loss per Ordinary Share is computed by dividing net loss by the weighted average number of shares of the Company’s Ordinary Shares assumed to be outstanding during the period of computation. Diluted net loss per ordinary share is computed similar to basic net loss per share except that the denominator is increased to include the number of additional Ordinary Shares that would have been outstanding if the potential ordinary shares had been issued at the beginning of the year and if the additional Ordinary Shares were dilutive (treasury stock method) or the two-class method, whichever is more dilutive. For all periods presented, basic and diluted net loss per Ordinary Share are the same, as any additional Ordinary Share equivalents would be anti-dilutive (see Note 13).

Income Taxes

Income taxes are recorded in accordance with ASC Topic 740, Income Taxes, or ASC 740, which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Realization of net deferred tax assets is dependent on future taxable income. Valuation allowances are provided, if based upon the weight of available evidence, it is more likely than not that some, or all, of the deferred tax assets will not be realized. Realization of net deferred tax assets is dependent on future taxable income (see Note 14).

The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. As of December 31, 2018 and 2017, the Company does not have any significant uncertain tax positions.

The Company is required to estimate income taxes in each of the jurisdictions in which it operates.

The Company’s reserves related to taxes are based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is more likely than not to be realized. As of December 31, 2018, the Company had no unrecognized tax benefits or related interest and penalties accrued.

In the United States, on December 22, 2017, the “Tax Cuts and Jobs Act” (the “Act”) was signed into law. Substantially all of the provisions of the Act are effective for taxable years beginning after December 31, 2017. The Act includes significant changes to the Internal Revenue Code of 1986 (as amended, the “Code”), including amendments which significantly change the taxation of individuals, and business entities. The Act contains numerous provisions impacting the Company, the most significant of which reduces the Federal corporate statutory tax rate from 34% to 21%.

The staff of the U.S. Securities and Exchange Commission (“SEC”) has recognized the complexity of reflecting the impacts of the Act, and on December 22, 2017 issued guidance in Staff Accounting Bulletin 118 (“SAB 118”), which clarifies accounting for income taxes under ASC 740 if information is not yet available or complete and provides for up to a one year period in which to complete the required analyses and accounting (the measurement period). SAB 118 describes three scenarios (or “buckets”) associated with a company’s status of accounting for income tax reform: (1) a company is complete with its accounting for certain effects of tax reform, (2) a company is able to determine a reasonable estimate for certain effects of tax reform and records that estimate as a provisional amount, or (3) a company is not able to determine a reasonable estimate and therefore continues to apply ASC 740, based on the provisions of the tax laws that were in effect immediately prior to the Act being enacted.

The various provisions under the Act deemed most relevant to the Company have been considered in preparation of its financial statements as of December 31, 2017. The Company had made a reasonable estimate for certain effects of tax reform and had recorded provisional amounts as part of its income tax provision. To the extent that clarifications or interpretations materialized in the future that would impact upon the effects of the Act incorporated into the December 31, 2017 financial statements, those effects would have been reflected in the future as or if they materialize. As of December 31, 2018, the Company has completed its accounting for all of the tax effects of the Act. Based on the additional analysis performed, no adjustments to the provisional amounts were made in the reporting period which had an impact to the tax provision or consolidated financial statements.

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, other costs associated with clinical and preclinical activities and regulatory operations and acquisition of in-process research and development write-offs. Refundable research and development credits / tax credits received are recorded as an offset to these costs.

Costs for certain development activities, such as Company funded outside research programs, are recognized based on an evaluation of the progress to completion of specific tasks with respect to their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the consolidated financial statements as prepaid or accrued research and development expense, as the case may be.

Share-Based Compensation Expense

Options

The Company grants share options to employees, non-employee members of the Company’s board of directors and non-employee consultants as compensation for services performed. Employee and non-employee members of the board of directors’ awards of share-based compensation are accounted for in accordance with ASC 718, Compensation - Stock Compensation, or ASC 718. ASC 718 requires all share-based payments to employees and non-employee directors, including grants of share options, to be recognized in the Statement of Operations and Comprehensive Loss based on their grant date fair values. The grant date fair value of share options is estimated using the Black-Scholes option valuation model.

Using this model, fair value is calculated based on assumptions with respect to (i) the fair value of the Company’s Ordinary Shares on the grant date; (ii) expected volatility of the Company’s Ordinary Share price, (iii) the periods of time over which employees and members of the Company’s board of directors are expected to hold their options prior to exercise (expected term), (iv) expected dividend yield on the Company’s Ordinary Shares, and (v) risk-free interest rates.

As there had been no public market for the Company’s Ordinary Shares until the Company’s IPO on June 7, 2018, the estimated fair value of the Ordinary Shares until that time had been determined by the Company’s board of directors as of the date of each option grant, with input from management, considering the most recently available third-party valuations of Ordinary Shares and the board of directors’ assessment of additional objective and subjective factors that it believed were relevant and which may have changed from the date of the most recent valuation through the date of the grant. The fair value of Ordinary Shares after the Company’s IPO was determined based upon the closing share price on the date of grant.

The third party estimated the fair value of the equity using a special case of the market approach known as the backsolve method. The backsolve method was used to solve for the implied total equity value based on the Company’s recent Series C financing round. Consideration was given to the rights and preferences of each of the Company’s classes of equity and the expected time to a liquidity event. An option pricing allocation method, or OPM, was selected to allocate the total equity value. The OPM treats ordinary shares and preferred shares as call options on the total equity value of a company, with exercise prices based on the value thresholds at which the allocation among the various holders of a company’s securities changes. Under this method, the Ordinary Shares have value only if the funds available for distribution to shareholders exceeded the value of the Preferred Shares’ liquidation preference at the time of the liquidity event, such as a strategic sale or a merger. These third-party valuations resulted in a valuation of the Company’s Ordinary Shares of $7.57, $2.64 and $5.63 per share as of December 31, 2016, September 15, 2017 and December 31, 2017, respectively.

The assumptions underlying these valuations represented management’s best estimate, which involved inherent uncertainties and the application of management’s judgment. As a result, if the Company had used different assumptions or estimates, the fair value of its Ordinary Shares and its share-based compensation expense could have been materially different.

Since the Company’s Ordinary Shares had not been traded on a public exchange prior to the Company’s IPO and have only been traded on a public exchange for a short period of time since the Company’s IPO, the Company believes that it does not have sufficient company-specific information available to determine the expected term based on its historical data. As a result, the expected term of share options granted to employees and members of the Company’s board of directors is determined using the average of the vesting period and contractual life of the option, an accepted method for the Company’s option grants under the SEC’s Staff Accounting Bulletin No. 107 and No. 110, Share-Based Payment.

Similarly, the Company believes that its future volatility will differ materially during the expected term from the volatility that would be calculated from its historical share prices to date. Consequently, expected volatility is based on an analysis of guideline companies in accordance with ASC 718. The expected dividend yield is zero as the Company has never paid dividends and does not currently anticipate paying any in the foreseeable future. Risk-free interest rates are based on quoted U.S. Treasury rates for securities with maturities approximating the option’s expected term.

The Company accounted for options granted to non-employee consultants under ASC 505-50, Equity-Based Payments to Non-Employees, or ASC 505-50. As such, the Company estimates the fair value of each such option using the Black-Scholes model, with the expected term of share options granted to non-employees initially equal to the options’ maximum contractual life of ten years, at issuance. On each subsequent reporting date until performance is complete, the Company revalued all outstanding options granted to non-employee consultants during the vesting period of each tranche. Under ASC 505-50, upon re-measurement of each award, income or expense is recognized during its vesting term. Compensation cost relating to awards with service-based graded vesting schedules is recognized as general and administrative and research and development expenses in the consolidated statements of operations and comprehensive loss using the straight-line method.

On July 1, 2018, the Company early adopted ASU 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting (“ASU No. 2018-07”) which simplifies the accounting for share-based payments granted to nonemployees for goods and services. The ASU supersedes ASC 505-50 and expands the scope of ASC 718 to include all share-based payment arrangements related to the acquisition of goods and services from both nonemployees and employees. The adoption of ASU No. 2018-17 did not have a material effect on the consolidated financial statements.

Restricted Shares

In connection with certain service agreements and research agreements, the Company has granted restricted Ordinary Shares as compensation. The Ordinary Shares are recognized in the consolidated statements of operations and comprehensive loss based on their grant date fair values. Compensation cost relating to share grants with service-based graded vesting schedules is recognized based on the vesting schedule.

Leases

The Company recognizes rent expense for operating leases on a straight-line basis over the term of the lease, beginning on the date the Company takes possession of the property. Rent expense includes the base amounts stated in the lease agreement as well as the effect of reduced or free rent and rent escalations. At lease inception, the Company determines the lease term by assuming the exercise of those renewal options that are reasonably assured because of the significant economic penalty that exists for not exercising those options. The expected lease term is one of the factors used to determine whether a lease is classified as an operating or capital lease and is used to calculate the straight-line rent expense. The difference between the cash paid to the landlord and the amount recognized as rent expense on a straight-line basis is included in deferred rent and classified within long-term liabilities. Lease incentives made by landlords to or on behalf of the Company for leasehold improvements are recorded as deferred rent and classified as long-term liabilities.

Asset Retirement Obligation

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, we estimate the fair value of our 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 on our Consolidated Balance Sheets were measured during a period of historically low interest rates. The impact on measurements of new asset retirement obligations using different rates in the future may be significant.

The Company uses estimates to determine the amount of the asset retirement obligations at the end of the lease term and discounts such asset retirement obligations using an estimated discount rate. Interest on the discounted asset retirement obligation is amortized over the term of the lease using the effective interest method and is recorded as interest expense in the consolidated statements of operations and comprehensive loss.

The change in asset retirement obligations is as folows:


	For the year ended December 31,
	2018			2017
Balance at beginning of year	$	178,419		$	221,254
Inception of asset retirement obligation		69,286			—
Amortization of interest		(38,301	)		19,313
Change in estimate		(99,090	)		(75,011	)
Effects of exchange rate		17,805			12,863

Balance at end of year	$	128,119		$	178,419

Other Comprehensive Income (Loss)

Other comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. The only component of other comprehensive income (loss) impacting the Company is foreign currency translation.

Foreign Currencies

The Company’s consolidated financial statements are presented in U.S. dollars, the reporting currency of the Company. The financial position and results of operations of Meira UK II and Meira B.V. are measured using the foreign subsidiaries’ local currency as the functional currency. Meira UK II’s cash accounts holding U.S. dollars are remeasured based upon the exchange rate at the date of remeasurement with the resulting gain or loss included in the consolidated statements of operations and comprehensive loss. Expenses of such subsidiaries have been translated into U.S. dollars at average exchange rates prevailing during the period. Assets and liabilities have been translated at the rates of exchange on the consolidated balance sheets dates. The resulting translation gain and loss adjustments are recorded directly as a separate component of shareholders’ equity and as other comprehensive loss on the consolidated statements of operations and comprehensive loss.

Segment Information

Management has concluded it has a single reporting segment for purposes of reporting financial condition and results of operations.

The following table summarizes non-current assets by geographical area:


	December 31, 2018		December 31, 2017
United States	$	454,568	$	436,463
United Kingdom		21,788,130		13,942,642

	$	22,242,698	$	14,379,105

Accounting Pronouncements Recently Adopted

In June 2018, the FASB issued ASU 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, which simplifies the accounting for share-based payments granted to nonemployees for goods and services. The ASU supersedes ASC 505-50 and expands the scope of ASC 718 to include all share-based payment arrangements related to the acquisition of goods and services from both nonemployees and employees. As a result, most of the guidance in ASC 718 associated with employee share-based payments, including most of its requirements related to classification and measurement, applies to nonemployee share-based payment arrangements. ASU 2018-07 generally requires an entity to use a modified retrospective transition approach, with a cumulative-effect adjustment to retained earnings as of the beginning of the period of adoption, for all (1) liability-classified nonemployee awards that have not been settled as of the adoption date and (2) equity-classified nonemployee awards for which a measurement date has not been established. The guidance is applicable to public business entities for fiscal years beginning after December 15, 2019 and interim periods within those years. Early adoption is permitted, and the Company adopted ASU No. 2018-07 on July 1, 2018, which did not have a material effect on the consolidated financial statements.

In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805), Clarifying the Definition of a Business, or ASU 2017-01, that clarifies the definition of a business to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. ASU 2017-01 requires an entity to evaluate if substantially all of the fair value of the gross assets acquired or disposed of is concentrated in a single identifiable asset or a group of similar identifiable assets; if so, the set of transferred assets and activities is not a business. ASU 2017-01 also requires a business to include at least an input and one substantive process that together significantly contribute to the ability to create output and removes the evaluation of whether a market participant could replace missing elements. ASU 2017-01 should be applied prospectively and is effective for annual periods beginning after December 15, 2017 and interim periods within those annual periods. The adoption of ASU 2017-01 on January 1, 2018 did not have a material effect on the Company’s financial position, results of operations or cash flows.

In December 2016, the FASB issued ASU No. 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers, or ASU 2016-20, that allows entities not to disclose variable consideration allocated to performance obligations related to either: (1) sales-or usage-based royalties on licenses of intellectual property or (2) variable consideration allocated entirely to a wholly unsatisfied performance obligation or to a wholly unsatisfied promise to transfer a distinct good or service that forms part of a single performance obligation when certain criteria are met. ASU 2016-20 also requires entities that use any of the new or previously existing optional exemptions to expand their qualitative disclosures. It also makes 12 additional technical corrections and improvements to the new revenue standard, ASU 2014-09. The amendments have the same effective date and transition requirements as ASU 2014-09. The adoption of ASU 2016-20 did not have a material effect on its financial position, results of operations or cash flows.

In November 2016, the Financial Accounting Standards Board, or FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230), Restricted Cash (a consensus of the Emerging Issues Task Force), or ASU 2016-18, which changes the presentation of the cash flow statement to include amounts generally described as restricted cash or restricted cash equivalents, together with cash and cash equivalents, when reconciling the beginning-of-period and end-of-period amounts shown on the statement of cash flows. ASU 2016-18 also requires additional disclosures concerning the nature of the restrictions on cash and cash equivalents and a reconciliation between amounts of cash, cash equivalents and restricted cash on the balance sheet and statement of cash flows for each period presented. ASU 2016-18 will be applied retrospectively to all periods presented and is effective for public business entities for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period. Prior to adoption, the Company presented changes in restricted cash as an operating activity in the statement of cash flows. Upon adoption of ASU 2016-18 on January 1, 2018, such changes are now reflected in the beginning and ending balances of cash, cash equivalents and restricted cash for all periods presented.

In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606), Narrow-Scope Improvements and Practical Expedients, or ASU 2016-12, which amends guidance in the new revenue standard, ASU No. 2014-09 Revenue from Contracts with Customers (Topic 606), or ASU 2014-09, on collectability, noncash consideration, presentation of sales tax and transition. The amendments in ASU 2016-12 are effective for annual reporting periods beginning after December 15, 2017 (i.e., January 1, 2018), including interim periods within those reporting periods, which is the same as for ASU 2014-09, as amended by ASU No. 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, or ASU 2015-14. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606), Identifying Performance Obligations and Licensing, or ASU 2016-10, which clarifies the principle for determining whether a good or service is “separately identifiable” from other promises in the contract and, therefore, should be accounted for as a separate performance obligation. In that regard, ASU 2016-10 requires that an entity determine whether its promise is to transfer individual goods or services to the customer, or a combined item (or items) to which the individual goods and services are inputs. In addition, ASU 2016-10 categorizes intellectual property, or IP, into two categories: “functional” and “symbolic.” Functional IP has significant standalone functionality. All other IP is considered symbolic IP. Revenue from licenses of functional IP is generally recognized at a point in time, while revenue from licenses of symbolic IP is recognized over time. ASU 2016-10 has the same effective date and transition requirements as ASU 2014-09, as amended by ASU 2015-14. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606), Principal versus Agent Considerations (Reporting Revenue Gross versus Net), or ASU 2016-08, which clarifies the implementation guidance on principal versus agent considerations contained in ASU 2014-09 by specifying that the determination as to whether an entity that is involved in providing a good or a service to a customer is a principal or an agent is based upon whether the entity controls the good or the service before it is transferred to the customer. ASU 2016-08 has the same effective date and transition requirements as ASU 2014-09, as amended by ASU 2015-14. The adoption of these ASU’s on January 1, 2018 did not have a material effect on the Company’s financial position, results of operations or cash flows.

In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. The new guidance is intended to improve the recognition and measurement of financial instruments by requiring separate presentation of financial assets and financial liabilities by measurement category and form of financial asset (i.e., securities or loans and receivables) within the balance sheet or the accompanying notes to the financial statements, eliminating the requirement for public business entities to disclose the method(s) and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost within the balance sheet, requiring public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes, requiring equity investments (except those accounted for under the equity method of accounting, or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income, and requiring a reporting organization to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk (also referred to as “own credit”) when the organization has elected to measure the liability at fair value in accordance with the fair value option for financial instruments, among others. In February 2018, the FASB issued ASU No. 2018-03, Technical Corrections and Improvements to Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities, which is intended to clarify certain aspects of the guidance issued in ASU 2016-01. The Company adopted these standards effective January 1, 2018, which had no impact on the Company’s consolidated financial statements.

Recent Accounting Pronouncements Not Yet Adopted

In November 2018, the FASB issued Accounting Standards Update No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 (“ASU 2018-18”). The standard amends Accounting Standards Codification 808, Collaborative Agreements and Accounting Standards Codification 606, Revenue from Contracts with Customers, to clarify the interaction between collaborative arrangement participants that should be accounted for as revenue under ASC 606. In transactions when the collaborative arrangement participant is a customer in the context of a unit of account, revenue should be accounted for using the guidance in Topic 606. The amendments in Update No. 2018-18 are effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. The Company is currently evaluating the new guidance included in ASU 2018-18, but does not expect it to have a material impact on its consolidated financial statements.

In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other than Inventory, or ASU 2016-16 which requires that an entity recognize the income tax consequences of an intra-entity transfer of assets other than inventory when the transfer occurs. The guidance must be applied using the modified retrospective basis. The Company does not expect the provisions of ASU 2016-16 to have a material impact on its current financial statements. This update will be effective for the Company at the beginning of fiscal 2019.

In February 2016, the FASB issued ASU No. 2016-02, “Leases” (ASC 842). The amended guidance requires lessees to recognize lease liabilities and right-of-use assets on the balance sheet for all leases with terms longer than 12 months and provides enhanced disclosures on key information of leasing arrangements. In July 2018, further amendments were issued to clarify how to apply certain aspects of the amended lease guidance and to address certain implementation issues. The amended guidance is effective for us commencing in the first quarter of 2019. Early adoption is permitted. We plan to adopt the amended guidance on the effective date and expect to elect the package of practical expedients. We expect the adoption of the amended guidance will materially affect our consolidated balance sheet and that the primary impact will be recognition of minimum commitments at present value of our noncancelable operating leases as lease liabilities and corresponding right-of-use assets. In July 2018, the FASB issued ASU No. 2018-10, which provides narrow amendments to ASU No. 2016-02 to clarify how to apply the rate implicit in the lease, impairment of the net investment in the lease, lessee reassessment of lease classification, variable payments that depend on an index or rate and certain transition adjustments. In July 2018, the FASB also issued ASU No. 2018-11, which provides targeted improvements to ASU No. 2016-02 to provide entities the transition option to not apply the standard in the comparative periods presented in the year of adoption. The Company will adopt the new standard effective January 1, 2019 using the modified retrospective transition method using the practical expedients model and a discount rate in the range of 8% to 10%, and elect to not apply the standard in the comparative periods presented in the year of adoption. We estimate that upon implementation, we will record a right-of-use asset between $3.3 million and $3.6 million and a corresponding liability between $3.6 million and $3.8 million. We are continuing to evaluate the impact that the amended lease guidance will have on our consolidated financial statements, systems, processes and internal controls.

Asset Acquisition

12 Months Ended

Dec. 31, 2018

Revenue Recognition and Deferred Revenue [Abstract]

Asset Acquisition

3.	Asset Acquisition:

On October 5, 2018, the Company entered into an agreement to acquire Vector Neurosciences Inc. (“Vector”) pursuant to an Agreement and Plan of Merger (the “Merger Agreement”) by and among the Company, Vector, VN Acquisition, Inc., a wholly-owned subsidiary of the Company (“Merger Sub 1”), VN Acquisition 2, Inc., a wholly-owned subsidiary of the Company (“Merger Sub 2”), the Vector stockholders named therein and the Vector stockholder representative, pursuant to which Merger Sub 1 was merged with and into Vector, with Vector being the surviving corporation (“Merger 1”) and, immediately following Merger 1, Vector was merged with and into Merger Sub 2, with Merger Sub 2 being the surviving corporation (together with Merger 1, the “Merger”). As a result of the Merger, Vector is a wholly-owned subsidiary of the Company. The Company’s board of directors, Vector’s board of directors and Vector’s stockholders have, in each case, unanimously approved the Merger, the Merger Agreement and the transactions contemplated by the Merger Agreement. The merger consideration to Vector’s stockholders consists of 225,000 shares of the Company’s Ordinary Shares as initial merger consideration, consisting of 202,500 shares which were issued at the closing of the Merger and an additional 22,500 shares to be issued 18 months following the closing, subject to any indemnification claims under the Merger Agreement (See Note 12).

In addition, pursuant to the terms of the Merger Agreement, the Company will issue to Vector’s stockholders additional Ordinary Shares equal to a maximum value of $21,000,000 if specified regulatory milestones are met and will make royalty payments to Vector’s stockholders in an amount equal to a percentage of the value of sales of certain products developed based on the Vector assets, which royalty payments are also payable in Ordinary Shares. The number of Ordinary Shares to be issued in connection with such milestones and royalties will be based on the three-day average closing price of the Company’s Ordinary Shares immediately prior to the date of determination of the value of the payment.

The Company determined this transaction represented an asset acquisition as substantially all of the value was in the intellectual property as defined by ASC 805, Business Combinations (“ASC 805”). The asset acquisition of in process research and development was recorded at a fair value of $2,990,250 as of October 5, 2018. The acquired in process research and development was immediately charged to research and development expense in the consolidated statement of operations and comprehensive loss as of the acquisition date since the Company determined that there was no additional alternative use of these assets. Additionally, under ASC 805, the Company determined that as of the acquisition date and as of December 31, 2018, the contingent milestone payments in the aggregate amount of $21,000,000, and royalty payments have not been resolved and therefore have not been recorded as liability.

Property, Plant and Equipment, net

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment, net

5.	Property, Plant and Equipment, net:

Property, plant and equipment, net at December 31, 2018 and 2017 consist of the following:


	December 31, 2018			December 31, 2017
Leasehold Improvements	$	11,538,377		$	10,873,895
Capitalized Leasehold Interest		7,150,611			—
Manufacturing Equipment		3,779,950			2,477,637
Laboratory Equipment		1,485,544			993,409
Computer and Office Equipment		334,525			276,100
Asset Retirement Obligation		113,678			153,133
Furniture & Fixtures		88,660			93,786

		24,491,345			14,867,960
Less: Accumulated depreciation		(2,477,108	)		(612,231	)

	$	22,014,237		$	14,255,729

In February 2016, the Company sublet a manufacturing facility for a term of 5 years, that included an additional 5-year option. This sub-lease was accounted for as an operating lease. On December 14, 2018, the Company executed a new sub-lease for this manufacturing facility whereby the sub landlords remaining term of 108 years was assigned to the Company. Under the new sub-lease, the Company paid a one-time fee of £5,250,000 (approximately $6,615,000 assuming a rate of $1.26 per GBP on the date of the acquisition) for the assignment and will no longer pay any base rent for the remaining 108 years. The one-time fee and related transaction costs, in the aggregate amount of £5,613,165 (approximately $7,150,611 using a rate of $1.2739 per GBP at December 31, 2018), have been accounted for as a capital lease and recorded as property, plant and equipment. The Company determined that the cost of the new sub-lease would be amortized on a straight-line basis over a 25-year estimated useful life.

In connection with the above-mentioned lease, the Company estimated that it had an asset retirement obligation at the end of the initial five-year lease term in the amount of $306,400. The Company discounted the asset retirement obligation using an 8% discount rate and recorded an asset retirement obligation in the amount of $205,659 as of December 31, 2016, which is included in leasehold improvements and was being depreciated over the five-year term of the lease (see Note 15). As of December 31, 2017, the Company determined that it was probable that it would exercise the additional five-year option provided for in the sub-lease. Therefore, the company remeasured the asset retirement obligation using the remaining eight-year new sub-lease term and recorded a reduction in the asset retirement obligation of $75,011 recorded in leasehold improvements. On December 14, 2018, upon execution of the new sub-lease, the Company remeasured the asset retirement obligation using the remaining 25-year estimated useful life and recorded a reduction in the asset retirement obligation of $99,090 recorded in leasehold improvements.

In connection with two operating leases entered into in July 2018, the Company estimated that it had asset retirement obligations at the end of the eight-year terms in the amount of $140,129. The Company discount the asset retirement obligation using an 8% discount rate and recorded an asset retirement obligation in the aggregate amount of $69,286, which is included in leasehold improvements and is being depreciated over the eight-year term of the lease.

Capitalized leases in the amount of $95,880 are included in computer and office equipment at December 31, 2018 and 2017, and accumulated depreciation of $62,912 and 34,552 at December 31, 2018 and 2017, respectively.

A capitalized lease in the amount of $7,150,611 is included in capitalized leasehold interest at December 31, 2018 and accumulated depreciation of $6,928 at December 31, 2018.

Depreciation expense was $2,052,948 and $679,177 for the years ended December 31, 2018 and 2017 respectively.

Accrued Expenses

12 Months Ended

Dec. 31, 2018

Payables and Accruals [Abstract]

Accrued Expenses

7.	Accrued Expenses:

Accrued expenses at December 31, 2018 and 2017 were comprised of the following:


	December 31, 2018		December 31, 2017
Compensation and Benefits	$	5,731,438	$	2,386,903
Clinical Trial Costs		4,013,094		4,859,410
Professional Fees		914,540		231,923
Consulting		821,009		1,220,477
Research and Development		236,271		73,379
Rent		122,770		387,267
Interest		40,800		33,437
Other		111,775		140,148

	$	11,991,697	$	9,332,944

Capitalized Leases

12 Months Ended

Dec. 31, 2018

Text Block [Abstract]

Capitalized Leases

8.	Capitalized Leases:

In 2015, the Company acquired certain office equipment in the amount of $17,817 under a 3-year lease arrangement. The Company determined that the lease should be capitalized since it contained a bargain purchase option for the equipment at the end of the lease term. Total payments under the capital lease amounted to $20,502 and had an interest rate of 9.35%.

In 2017, the Company acquired additional office equipment in the amount of $78,063 under a 3-year lease arrangement. The Company determined that the lease should be capitalized since it contained a bargain purchase option for the equipment at the end of the lease term. Total payments under the capital lease will amount to $86,145 and has an interest rate of 6.90%.

In December 2018, the Company entered into a sub-lease for the remaining term of 108 years (see Note 5). The Company determined that the lease should be capitalized since the lease term exceeded 75% of the estimated 25-year useful life of the leasehold interest. The Company made a one-time upfront payment for the assignment of the lease and will not have any obligation to make future rent payments. The Company capitalized as property, plant and equipment, the initial one-time upfront payment and related transaction costs in the aggregate amount of $7,150,611.

The following is a schedule, by year, of future minimum lease payments under the capital leases together with the present value of the net minimum lease payments as of December 31, 2018:


2019		28,715
2020		7,179

Total minimum lease payments		35,894
Less: amount representing interest		(1,598	)

Present value of net minimum lease payments		34,296
Less: current portion		(27,199	)

Obligations under capital lease, less current portion	$	7,097

Notes Payable

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Notes Payable

9.	Notes Payable

On October 26, 2017, in connection with an amendment and termination of a lease, the Company issued a promissory note in the amount of $1,442,009 to ARE, the landlord and also a related party (see Note 15). The note bears interest at the rate of 5% per annum and was due on December 31, 2018. However, if the Company had sufficient liquidity, as defined in the note, then the note, including accrued interest, would become due and payable at that time. In accordance with the sufficient liquidity provision, the Company repaid the note, plus accrued interest, in the amount of $1,472,433 during the three-month period ended March 31, 2018. The Company recorded interest expense in the consolidated statements of operations and comprehensive loss in connection with the note in the amount of $17,386 and $13,037 for the years ended December 31, 2018 and 2017, respectively.

Collaboration Agreement

12 Months Ended

Dec. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Collaboration Agreement

10.

Collaboration Agreement

On October 16, 2018, the Company entered into a research collaboration agreement with Janssen Pharmaceuticals, Inc., (“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 year ended December 31, 2018, the Company amortized $224,576 of the deferred research funding, which was recorded as an offset to research and development expenses. Deferred research funding in the amount of $434,091 is included as other current liabilities on the consolidated balance sheet at December 31, 2018.

Share-Based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Share-Based Compensation

11.

Share-Based Compensation

2018 and 2016 Equity Incentive Plans

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 consultants. The Company’s board of directors administer the Plans. Options granted under the Plans have a maximum contractual term of ten years. Options granted generally vest 25% on the first anniversary date of grant and the balance ratably over the next 36 months. Options granted to directors generally vest on the first anniversary date of grant. Upon the adoption of the 2018 Incentive Award Plan, the Company ceased issuing awards under the 2016 Equity Incentive Plan.

A summary of the Company’s share option activity related to employees, non-employee members of the board of directors and non-employee consultants as of and for the years ended December 31, 2018 and 2017 is as follows:

STOCK OPTION TABLE


	Number of Options			Weighted- Average Exercise Price			Aggregate Instrinsic Value
Outstanding at December 31, 2016		333,660		$	7.72
Granted		611,933			3.73
Exercised		(1,288	)		(7.57	)
Expired		—			—
Forfeited		(5,668	)		(7.72	)

Outstanding at December 31, 2017		938,637		$	5.12
Granted		2,334,285			8.63
Exercised		—			—
Expired		—			—
Forfeited		(10,557	)		(5.51	)

Outstanding at December 31, 2018		3,262,365		$	7.64		$	6,903,313

Weighted average remaining contractual life of options outstanding as of December 31, 2017 (yrs)		9.09

Weighted average remaining contractual life of options outstanding as of December 31, 2018 (yrs)		9.24

Options exercisable at December 31, 2017		186,394		$	7.72

Options exercisable at December 31, 2018		535,241		$	5.79

Weighted average remaining contractual life of options exercisable as of December 31, 2017 (yrs)		8.21

Weighted average remaining contractual life of options exercisable as of December 31, 2018 (yrs)		7.88

The total fair value of options vested during the years ended December 31, 2018 and 2017 was $1,387,607 and $898,699, respectively.

During the years ended December 31, 2018 and 2017, the Company granted 2,334,285 and 611,933 share options, respectively. The grant date fair values of the stock options granted were estimated using the Black-Scholes option valuation model with the following ranges of assumptions (see Note 2):


	2018	2017
Risk-free interest rate	2.32% - 2.98%	2.28% - 2.51%
Expected volatility	90%	80%
Expected dividend yield	0%	0%
Expected life (in years)	5.5 - 10.0	5.5 - 10.0

As of December 31, 2018 and 2017, the total compensation expense relating to unvested options granted that had not yet been recognized was $17,415,098 and $987,413, respectively which is expected to be realized over a period of 4.0 and 3.42 years, respectively. 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 years ended December 31, 2018 and 2017 was $6.53 and $3.10, 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 December 31, 2018, 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 of such shares vested immediately, with the balance vesting quarterly over the next eight quarters beginning three months after the effectiveness of the Company’s registration statement on Form S-1 filed with the SEC on June 7, 2018 (the “Registration Statement”). The shares were valued at $15.00 per share and the related share-based compensation expense, which is recognized over the requisite service period, is included in general and administrative expenses in the consolidated statements of operations and comprehensive loss. 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 restricted shares. Total compensation expense in connection with the issuance of those restricted Ordinary Shares, in the amount of $20,141,876, of which $10,156,868 was share-based, was recorded as general and administrative expense during the year ended December 31, 2018 (See Note 16).

A summary of the restricted Ordinary Shares is as follows:


	Ordinary Shares			$ Value
Non-vested at December 31, 2016		386,608		$	3,020,191
Vesting during 2017		(280,695	)		(2,154,330	)

Non-vested at December 31, 2017		105,913			865,861
Issued during 2018		1,306,348			19,595,220
Vesting during 2018		(759,087	)		(10,663,471	)

Non-vested at December 31, 2018		653,174		$	9,797,610

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 year ended December 31, 2018.

During the years ended December 31, 2018 and 2017 the Company recognized total share-based compensation expense in the accompanying consolidated statements of operations and comprehensive loss as follows:


	2018		2017
Research and development	$	3,372,054	$	2,374,899
General and administrative		14,511,500		584,832

Total share based compensation	$	17,883,554	$	2,959,731

The Company does not expect to realize any tax benefits from its share option activity or the recognition of share-based compensation expense because the Company currently has net operating losses and has a full valuation allowance against its deferred tax assets. Accordingly, no amounts related to excess tax benefits have been reported in cash flows from operations or cash flows from financing activities for the years ended December 31, 2018 and 2017.

Ordinary Shares, Convertible Preferred C Shares and Shareholders' Deficit

12 Months Ended

Dec. 31, 2018

Federal Home Loan Banks [Abstract]

Ordinary Shares, Convertible Preferred C Shares and Shareholders' Deficit

12.

Ordinary Shares, Convertible Preferred C Shares and Shareholders’ Deficit:

Ordinary Share Issuances

2018

As discussed in Note 11, 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.

In connection with the Company’s initial public offering, on June 7, 2018, the Company issued 5,000,000 Ordinary Shares at an offering price of $15.00 per share for gross proceeds of $75,000,000, excluding offering costs of $9,807,622.

Also, as discussed in Note 11, on June 7, 2018, upon the effectiveness of the Company’s Registration Statement, 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 of such shares vested immediately, with the balance vesting quarterly over the next eight quarters.

On October 5, 2018, in connection with an acquisition, the Company issued 202,500 Ordinary Shares with an additional 22,500 shares to be issued 18 months following the closing, subject to any indemnification claims under the merger agreement.

2017

On July 31, 2017, the Company issued 1,288 Ordinary Shares in connection with the exercise of an option.

On August 16, 2017, the Company issued 6,441 Ordinary Shares in connection with a research agreement.

Convertible Preferred C Shares

Issuances

2018

During the year ended December 31, 2018, the Company issued 5,425,124 Preferred Shares at an offering price of approximately $10.48 per share for gross proceeds of $56,849,611, excluding offering costs of $690,473.

Also, during the year ended December 31, 2018, the Company issued 129,419 Preferred Shares in lieu of payment of accounts payable in the aggregate amount $1,355,097 to certain vendors.

On March 15, 2018, the Company issued 13,360 Preferred Shares in connection with a license agreement.

On June 7, 2018, upon effectiveness of the Company’s Registration Statement on Form S-1, all of the 11,501,432 outstanding Preferred Shares were automatically converted into 11,501,432 Ordinary Shares. In connection with the conversion of the Preferred Shares, $664,718 of unaccredited financing costs were fully accreted.

2017

During the year ended December 31, 2017, the Company issued 9,739 Preferred Shares at an offering price of $20.96 per share and 1,598,418 Preferred Shares at an offering price of $10.48 per share for gross proceeds of $16,854,656, excluding offering costs of $98,804. The net proceeds of the offering were used for working capital, research and development and general corporate purposes.

On November 2, 2017, a note payable to a related party in the amount of $2,500,000 was converted at the rate of $10.48 per share, into 238,579 Preferred Shares (see Note 15).

Warrants

In connection with the issuance of 715,737 Preferred Shares on September 21, 2017, at an offering price of $10.48 per share, the Company issued warrants to purchase 695,696 Preferred Shares at an exercise price of $10.48 per share. The warrants expired on the first of the following to occur:

(i)

an Asset Sale;

(ii)

a Qualified IPO;

(iii)

a Share Sale;

(iv)

the winding up of the Company; or

(v)

On the third anniversary of the date of issuance

The Black-Sholes value of the warrants in the amount of $1,660,500 was accounted for as a warrant liability and a discount to the Preferred Shares at the time of issuance and were being accreted over the expected term of the Preferred Shares (see Note 2).

The Black-Scholes value of the warrants in the amount of $553,500 was recorded as a warrant liability and charged to convertible note inducement expense within the statement operations and comprehensive loss at the time of issuance.

Both of the warrants were revalued under the Black-Scholes valuation model at December 31, 2017, which resulted in an increase of the warrant liability in the amount of $465,633, which was charged to change in fair value of warrant liability within the statement of operations and comprehensive loss.

The warrant liability at December 31, 2017 was $2,679,633.

On June 5, 2018, all of the outstanding warrants to purchase 927,594 Preferred Shares at an exercise price of approximately $10.48 per share were exercised for aggregate cash proceeds of $9,720,000.

Net Loss per Share

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Net Loss per Share

13.

Net Loss per Share

The Company computes net loss per share in accordance with ASC 260-10, Earnings per Share (see Note 2).

Basic and diluted net loss per share is computed as follows:


	2018			2017
Net loss—basic and diluted	$	(82,865,874	)	$	(31,044,535	)
Accretion of Preferred Shares financing costs		(1,806,512	)		(191,963	)
Accretion of warrant		—			(615,000	)

Adjusted net loss—basic and diluted	$	(84,672,386	)	$	(31,851,498	)
Weighted-average ordinary shares outstanding:
Basic and Diluted		18,948,520			8,572,315

Net loss per share:
Basic and Diluted	$	(4.47	)	$	(3.72	)

The following securities are considered to be Ordinary Share equivalents, but were not included in the computation of diluted net loss per Ordinary Share because to do so would have been anti-dilutive:


	December 31, 2018		December 31, 2017
Preferred Shares		—		5,005,934
Restricted Ordinary Shares subject to forfeiture		653,174		105,913
Stock options		3,262,365		938,637
Warrants		—		927,594

		3,915,539		6,978,078

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

14.

Income Taxes:

Since the Company has recurring losses and a valuation allowance against deferred tax assets, there is no tax expense (benefit) for the year ended 2017. For the year ended December 31, 2018, the Company recognized a tax benefit of $(474,391).

The subsidiaries each file separate tax returns in their respective tax jurisdictions.

As of December 31, 2018, the Company had federal and state net operating loss (“NOL”) carryforwards in the United States of approximately $14,210,000 and $14,155,000, respectively, and in the United Kingdom of approximately $94,100,000, which are available to reduce future taxable income. The U.S. federal and state NOL carry forwards incurred prior to January 1, 2018 in the amount of approximately $6.8 million and $6.7 million, respectively, will begin to expire in 2036. The U.S. NOL incurred after December 31, 2018 and the U.K. NOL will be indefinitely carried forward. Also, as of December 31, 2018, the Company had orphan drug and research and development credits in the U.S. in the amount of $1,134,000 which will begin to expire in 2036. The NOL carry forwards are subject to review and possible adjustment by the U.S., U.K. and state tax authorities. NOL carry forwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders, as defined under Sections 382 Internal Revenue Code, as well as CTA 2010 Part 14 under the UK tax rules. This could limit the amount of NOLs that the Company can utilize annually to offset future taxable income or tax liabilities. As of December 31, 2018, the Company has performed such an analysis and determined that there were no limitations in the U.K. However, for U.S. purposes the Company determined that a change of ownership occurred in April 2016. The Company is still in the process of determining the annual limitation on losses that occurred prior to April 2016. Subsequent ownership changes and proposed future changes to the UK (or US) tax rules in respect of the utilization of losses carried forward may further affect the limitation in future years, if any. Additionally, the Company has not undertaken a study on the completeness of the U.S. orphan drug and research and development credit.

The Company’s pre tax earnings from the United Kingdom and United States locations are as follows:


	December 31, 2018			December 31, 2017
United Kingdom	$	(73,359,977	)	$	(26,458,625	)
United States		(9,980,287	)		(4,585,910	)

	$	(83,340,264	)	$	(31,044,535	)

The Company is subject to the corporate tax rate in the U.K. as a Limited U.K. corporation.

The following table summarizes a reconciliation of income tax benefit compared with the amounts at the U.K. statutory income tax rate:


	December 31, 2018					December 31, 2017
Statutory rate		(15,834,650	)	19.00	%		(5,976,073	)	19.25	%
Permanent differences—other		1,438,934		-1.73	%		654,648		-2.11	%
RTP and other adjustments		387,509		-0.46	%		(152,948	)	0.49	%
U.K. tax credit		1,707,489		-2.05	%		539,136		-1.74	%
U.S. tax credit		(436,250	)	0.52	%		(363,665	)	1.17	%
Foreign tax rate differential		(171,693	)	0.21	%		(673,619	)	2.17	%
State and local rate, net of federal tax		(1,159,522	)	1.39	%		(446,683	)	1.44	%
UK Rate Change (17% at expected DTA turn)		1,104,863		-1.33	%		482,351		-1.55	%
U.S. state rate change		(6,496	)	0.01	%		993,998		-3.20	%
Change in valuation allowance		12,495,426		-14.99	%		4,942,855		-15.92	%

Actual income tax benefit effective tax rate		(474,391	)	0.57	%		—		0.00	%

The Expense/(Benefit) for income taxes from continuing operations consists of the following:


	December 31, 2018			December 31, 2017
Current Tax Expense/(Benefit)
United Kingdom		—			—
United States		—			—

Total Current		—			—
Deferred Tax Expense/(Benefit)
United Kingdom	$	(8,888,096	)	$	(3,759,109	)
United States		(3,606,275	)		(1,183,746	)

Total Deferred		(12,494,371	)		(4,942,855	)
Change in Valuation Allowance		12,019,880			4,942,855

Total Income Tax Expense/(Benefit)	$	(474,391	)	$	—

Income tax (benefit) expense for each year is allocated to continuing operations, discontinued operations, extraordinary items, other comprehensive income, the cumulative effects of accounting changes, and other charges or credits recorded directly to shareholders’ equity. ASC 740-20-45 Income Taxes, Intraperiod Tax Allocation, Other Presentation Matters includes an exception to the general principle of intraperiod tax allocations. The codification source states that the tax effect of pretax income or loss from continuing operations generally should be determined by a computation that considers only the tax effects of items that are included in continuing operations. The exception to that incremental approach is that all items (i.e. other comprehensive income, discontinued operations, etc.) be considered in determining the amount of tax benefit that results from a loss from continuing operations and that benefit should be allocated to continuing operations. That is, when a company has a current period loss from continuing operations, management must consider income recorded in other categories in determining the tax benefit that is allocated to continuing operations. This includes situations in which a company has recorded a full valuation allowance at the beginning and end of the period, and the overall tax provision for the year is zero. The intraperiod tax allocation is performed once the overall tax provision has been computed and allocates that provision to various income statement (continuing operations, discontinued operations), other comprehensive income and balance sheet captions. While the intraperiod tax allocation does not change the overall tax provision, it results in a gross-up of the individual components. The level of application has been applied on the group level.

As the Company experienced a net loss from operations for the year ended December 31, 2018 and other comprehensive income from foreign currency translation adjustments, the Company has allocated income tax expense against the components of other comprehensive income in 2018 using a 17% effective tax rate. Income tax benefit for the year ended December 31, 2018 includes a benefit of $(474,391) due to the required intraperiod tax allocation. Conversely, other comprehensive income for the year ended December 31, 2018 includes income tax expense of $474,391.

Deferred Tax Assets/(Liabilities)


	December 31, 2018
	Total			UK			US
Deferred Tax Assets:
Net operating loss carryforwards	$	20,646,185		$	16,000,329		$	4,645,856
Other		1,414,690			(46,604	)		1,461,294
Tax Credit		1,133,656			—			1,133,656

Deferred tax assets		23,194,531			15,953,725			7,240,806
Less: valuation allowance		(23,194,531	)		(15,953,725	)		(7,240,806	)

Net deferred tax asset	$	—		$	—		$	—


	December 31, 2017
	Total			UK			US
Deferred Tax Assets:
Net operating loss carryforwards	$	9,462,690		$	6,909,754		$	2,552,937
Other		539,008			152,554			386,454
Tax Credit		697,406			—			697,406

Deferred tax assets		10,699,105			7,062,308			3,636,797
Less: valuation allowance		(10,699,105	)		(7,062,308	)		(3,636,797	)

Net deferred tax asset	$	—		$	—		$	—

ASC 740 requires a valuation allowance to reduce the deferred tax assets reported if, based on the weight of available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. After consideration of all the evidence, both positive and negative, the Company has recorded a full valuation allowance against its deferred tax assets at December 31, 2018 and 2017 because the Company’s management has determined that is it more likely than not that these assets will not be fully realized.

Changes to the U.K. and U.S. corporation tax rates have been announced which will impact future accounting periods. In his budget of July 8, 2015, the Chancellor of the Exchequer announced a reduction in the U.K. corporation tax rate to 19% for the financial year beginning April 1, 2017 and a further reduction to 18% for the financial year beginning April 1, 2020. These changes received Royal Assent on November 18, 2015. The U.K. Finance Act 2016 provides for a further reduction in the corporation tax rate to 17% for the Financial Year beginning April 1, 2020. This change was enacted on September 15, 2016. As the Company does not expect to be able to utilize its NOL’s in the U.K. prior to its financial year beginning on January 1, 2021, if at all, the deferred tax has been calculated using a tax rate of 17%.

In the United States, the corporation tax rate was reduced to 21% for the financial year beginning January 1, 2018. As these changes were enacted prior to the December 31, 2017 balance sheet date, deferred tax has been calculated accordingly in these consolidated financial statements, which represented a decrease in the prior years deferred tax assets of approximately $994,000.

The Company will recognize interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2018 and 2017, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company’s statements of operations and comprehensive loss.

The Company files income tax returns in the United States, United Kingdom and the Netherlands, and various state jurisdictions. For the US, the statute of examination is open for tax years 2015, 2016, 2017 and 2018. For the UK and the Netherlands, the statute of examination is open for tax years 2017 and 2018.

MeiraGTx Holdings plc is a UK tax resident with no earnings in its foreign subsidiaries and the Company does not expect any temporary basis difference in its investment in these subsidiaries to reverse in the foreseeable future. Therefore, the Company has not recorded deferred taxes on the outside basis difference in its foreign subsidiaries. It is not probable to compute the amounts, if any.

Related Party Transactions

12 Months Ended

Dec. 31, 2018

Related Party Transactions

15.

Related Party Transactions:

Transition Services Agreement

Effective April 24, 2015, the Company entered into a transition services agreement (the “TSA”) with Kadmon, which owned 12.9% of the Company at December 31, 2018, whereby Kadmon would provide office and laboratory facilities as well as certain other personnel support activities to the Company. Under the agreement, the Company is charged for (i) rent based upon the square footage of the office and laboratory facilities used by the Company (ii) other personnel support activities based upon the hours of the personnel providing the support activities, and (iii) and other direct costs incurred by Kadmon on behalf of the Company, plus a 7% administrative fee. The TSA terminated on April 24, 2018 and the Company is currently leasing office space on a month to month basis from Kadmon.

During the years ended December 31, 2018 and 2017, the Company incurred the following charges in connection with the TSA which are included in loss from operations:


	2018		2017
Rent	$	557,698	$	548,229
Personnel		6,493		39,721
Other		6,334		5,983

Total charges incurred	$	570,525	$	593,933

During the year ended December 31, 2018 and 2017, the Company made cash payments totaling $1,431,555 and $275,941, respectively.

The amount due to Kadmon at December 31, 2018 and 2017 is $0 and $861,030, respectively, and is disclosed as Due to Kadmon on the Company’s consolidated balance sheets.

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 research and development under the direction of the Company. In connection with the agreement, the Company issued several work orders during the years ended December 31, 2016 and 2017 in the aggregate amounts of £1,402,202, or approximately $1,885,000, based upon the average exchange rates during the years ended December 31, 2016 and 2017, respectively. Either party may terminate the agreement by giving 30 days written notice. Total research and development expenses under this agreement for the years ended December 31, 2018 and 2017 was approximately $636,000 and $538,000, respectively. Future obligations under the agreement equal £612,382, or approximately $779,685, through October 2020.

The amount due to UCL under the master services agreement at December 31, 2018 and 2017 is $389,101 and $775,315, respectively and is included in accounts payable and accrued expenses on the Company’s consolidated balance sheets.

Effective September 1, 2016, the Company entered into a manufacturing and drug supply agreement with UCL. Pursuant to the agreement, UCL manufactured materials for the Company’s clinical trials under the direction of the Company. The agreement was terminated in January 2018. Total research and development expenses under this agreement for the years ended December 31, 2018 and 2017 was approximately $0 and $1,904,352, respectively.

The amount due to UCL under the manufacturing and drug supply agreement at December 31, 2018 and 2017 is $0 and $2,466,142, respectively and is included in accrued expenses on the balance sheet.

Leases

July 2016 Lease

Effective July 1, 2016, the Company entered into a non-cancellable operating lease for laboratory and related office facilities in New York with ARE, an entity that is under common control by an entity that is a minority shareholder of the Company and whose executive chairman and founder is a director of the Company. The lease provides for monthly base rent and property management fees, including rent escalations and rent holidays, plus operating expenses during the lease term, which expires on December 31, 2021. The Company records monthly rent expense on a straight-line basis from July 1, 2016 through December 31, 2021. As of December 31, 2018 and 2017, the balance of deferred rent, representing the difference between cash rent paid and straight-line rent expense, was $201,264 and $231,276, respectively.

Total rent expense under this operating lease was $487,555 and $487,559 for the years ended December 31, 2018 and 2017, respectively. As of December 31, 2018, the aggregate future minimum rental payments under this lease are $1,663,952.

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 expired on July 7, 2017 and was automatically renewed annually through July 7, 2021. This standby letter of credit is secured with restricted cash in a money market account (see Note 6).

December 2016 Lease

Effective December 15, 2016, the Company entered into another non-cancellable operating lease with ARE, expiring on October 31, 2032, for laboratory and office facilities in New York. The lease provided for monthly base rent, including rent escalations, property management fees and rent holidays, plus operating expenses during the lease term. The Company recorded monthly rent expense on a straight-line basis from December 15, 2016 through October 31, 2032. On October 26, 2017, the lease was amended, whereby the lease would terminate on March 31, 2018 and only base rent and management fees in the aggregate amount of $563,507 would be due from November 1, 2017 through March 31, 2018. Under the amendment, the Company issued a note to ARE in the amount of $1,442,009 (see Note 9), removed the balance of the deferred rent and accrued the future rent payments, all of which were recorded as rent expense at the time of the amendment, in accordance with ASC 420, Exit and Disposal Activities, as the Company had a cease use date as of the date of the amendment.

Total rent expense under this operating lease was $0 and $1,660,806 for the years ended December 31, 2018 and 2017, respectively.

Convertible Note Payable

On May 1, 2017, the Company issued a convertible note in the amount of $2,500,000 to ARE. The note had an interest rate of 10% per annum and was convertible into Preferred Shares at any time at the option of the holder or would automatically convert into Preferred Shares in the event of an equity investment by a mutually agreed upon institutional investor at a price per share equal to the lowest price paid per share by a purchaser of the Company’s Preferred Shares. On November 2, 2017 the note was converted to 238,579 Preferred Shares at $2.70 per share. In accordance with the terms of the convertible note, the accrued interest in the amount of $145,833 was cancelled.

As an inducement to convert the convertible note, the Company issued a warrant to purchase 900,000 Preferred Shares, at an exercise price of $2.70 per share, to the holder of the convertible note, which was expenses in accordance with ASC 470 (see Note 12).

Commitments

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Commitments

16.

Commitments:

Operating Leases

In February 2016, the Company entered into a non-cancellable operating lease, expiring in February 2021, for manufacturing and office facilities in London, UK. The lease provides for an additional five-year term at the Company’s option. The lease provides for monthly base rent, plus operating expenses and real estate taxes during the lease term.

Total rent expense under this operating lease was $273,430 and $279,303 for the years ended December 31, 2018 and 2017, respectively.

On October 1, 2017, the Company entered into a one-year non-cancellable operating lease, expiring in September 2018, for office and laboratory facilities in Leiden, Netherlands. The lease provides for monthly base rent plus operating expenses during the lease term. The lease provides for successive one-year extensions up to a maximum of four extensions. Total rent expense under this operating lease was $9,313 and $5,273 for the years ended December 31, 2018 and 2017, respectively.

In June 2017, the Company entered into two non-cancellable operating leases, expiring in July 2018, for office and laboratory facilities in London, UK. The lease provides for monthly base rent, rent holidays plus operating expenses and real estate taxes during the lease term. The Company records monthly rent expense on a straight-line basis from June 1, 2017 through July 23, 2018. As of December 31, 2018, the balance of deferred lease obligation, representing the difference between cash rent paid and straight-line rent expense, was $0. Total rent expense under theses operating leases was $73,846 and $85,222 for the years ended December 31, 2018 and 2017, respectively.

On July 27, 2018 the two leases for office and laboratory facilities in London, UK expired. Effective July 27, 2018, the Company entered into two new non-cancellable operating leases for the same office and laboratory facilities in London. The leases provide for annual base rent in the aggregate amount of approximately $363,000, plus operating expenses, through May 31, 2022, at which time the annual base rent will be revalued based on market rates at that time. The leases expire on May 24, 2027. Total rent expense under these operating leases was $148,561 and $0 for the years ended December 31, 2018 and 2017, respectively.

The aggregate future minimum rental payments under these operating leases are as follows:


2019	$	353,782
2020	$	350,284
2021	$	350,284
2022	$	350,284
2023	$	350,284
Thereafter	$	1,196,805


Total future rent payments	$	2,951,723

The aggregate future minimum rental payments of all leases, including those discussed in Note 15 are as follows:


2019	$	889,465
2020	$	904,716
2021	$	924,121
2022	$	350,284
2023	$	350,284
Thereafter	$	1,196,805


Total future rent payments	$	4,615,675

Service Agreements

On April 27, 2015, the Company entered into service agreements with a senior officer and a greater than 5% shareholder of the Company. Under the terms of the agreements, the employees will receive aggregate compensation of £300,000, which has been increased to a maximum aggregate amount of £410,000 per annum, or approximately $522,000 using exchange rates as of December 31, 2018. The agreements also provide for contributions to a defined contribution pension plan to be set up by the Company and a discretionary bonus. The agreements may be terminated at any time by either party by giving twelve-months’ notice, or the Company may terminate the officer’s employment effective immediately upon notice, and within 28 days making payment in lieu of notice consisting of a sum equivalent to the officer’s annual salary for the relevant period. For the years ended December 31, 2018 and 2017, the Company recorded £1,001,000 and £724,000 or approximately $1,334,000 and $933,000, respectively, using the average exchange rates during the years ended December 31, 2018 and 2017, respectively, in research and development costs under these agreements. Future obligations to be paid under these agreements equal £150,333, or approximately $192,000, using exchange rates as of December 31, 2018.

In connection with the service agreements, on April 24, 2015, the employees were awarded, under a share award agreement (the “Share Award Agreement”), an aggregate of 2,704,800 restricted Ordinary Shares and 750 B ordinary shares, which B ordinary shares have been converted into Ordinary Shares, of the Company. Under the Share Award Agreement, such shares are subject to forfeiture ratably over a period of three years if the employee’s do not remain an employee or consultant to the Company. The shares were valued at $7.76 per share and, in accordance with ASC 718, were charged to operations as share-based compensation ratably over the forfeiture period.

Employment Agreements

In February 2016, the Company entered into three-year employment agreements with certain senior officers of the Company. Under the terms of the agreements, which automatically renew for successive one-year terms, the employees will receive annual compensation in the aggregate amount of $710,000, which has been increased to a maximum aggregate amount of $1,075,000. The employment agreements also provide for an annual guaranteed cash bonus targeted at 100% of annual compensation. The agreements also provide for discretionary annual performance bonuses targeted to be not less than 50-60% of the employee’s base salary and grants of restricted stock. In January 2018 the Company’s compensation committee approved a discretionary bonus in the aggregate amount of $1,196,000. This discretionary bonus and the guaranteed bonus for 2017, in the amount of $850,000, were subject to compensation committee approval and meeting certain future funding conditions. On February 28, 2018, the funding conditions were met. The senior officers were granted their guaranteed and discretionary bonuses for the year ended December 31, 2018, in the aggregate amount of $3,415,000, which was paid in January 2019.

Additionally, the agreements provided for equity incentives of up to an aggregate maximum of 8.0% of the Company’s fully diluted outstanding shares upon the attainment of certain milestones. On March 1, 2018, a funding milestone was met. Accordingly, the employees were issued an aggregate of 3% of the fully-diluted outstanding shares of the Company as of such date. On June 7, 2018, an additional milestone was met. Accordingly, the employees were issued an aggregate of 5% of the fully-diluted outstanding shares of the Company as of such date (see Note 11).

The employees are also entitled to participate in all incentive and deferred compensation and employee benefit programs available to employees and executive officers of the Company. Future obligations to be paid under these agreements equal $1,258,750, as of December 31, 2018.

Consulting and other Agreements

Effective September 28, 2015, the Company entered into a three-year consulting agreement with a consultant to provide ongoing strategic advice and to serve on the Company’s board of directors. In connection with the agreement, the Company issued 662,910 restricted Ordinary Shares. Under the consulting agreement, such shares were subject to forfeiture ratably over a period of three years if the consultant does not remain a consultant to the Company. The shares were valued at $7.72 per share and were charged to general and administrative expenses upon the expiration of each forfeiture period. For the years ended December 31, 2018 and 2017, the Company recorded $263,970 and $351,960, respectively, in general and administrative expense under this agreement. There are no future obligations to be paid under the agreement.

Research Agreements

On April 24, 2015, the Company entered into a cooperative research and development agreement (CRADA) with the U.S. Department of Health & Human Services, as represented by the National Institute of Dental and Craniofacial Research (NIDCR) and Institute or Center of the National Institutes of Health (NIH). The CRADA provided for quarterly payments of $21,250 for three years through April 30, 2017 and a cost per patient for each patient enrolled in the Company’s xerostomia clinical trial. The CRADA was amended on March 25, 2016 to extend the term through March 25, 2021 and to extend the annual payments throughout the revised term. Research and development expenses under the CRADA for the years ended December 31, 2018 and 2017 were $111,938 and $115,374, respectively. Future obligations to be paid under the CRADA, as amended, through March 25, 2021 equal $191,250.

On March 22, 2016, the Company entered into another CRADA with the NIDCR and NIH for the treatment of Sjögren’s syndrome associated salivary hypofunction. The CRADA provides for quarterly payments of $104,500 for the first three years of the agreement plus a cost per patient for each patient enrolled in a clinical trial. The costs associated with years four and five of the Sjögren’s syndrome CRADA will be determined at a later date. Total research and development expenses under this agreement for each of the years ended December 31, 2018 and 2017 were $418,000. There are no future obligations to be paid under the agreement.

Effective December 5, 2016, the Company entered into a three-year research collaboration agreement with Cornell University. Pursuant to the agreement, Cornell University provides research and development under the direction of the Company. In connection with the agreement, in July 2017, the Company issued 25,000 Ordinary Shares to Cornell University, which were recorded as research and development expenses in the amount of $17,000. The Company amended this agreement, effective June 12, 2017, to add a second three-year research collaboration project through September 2019. The Company further amended this agreement, effective October 18, 2018 to include additional costs related to the research. Total research and development expenses under this agreement, as amended, for the years ended December 31, 2018 and 2017 were $1,625,152 and $1,029,904, respectively. Future obligations to be paid under the agreement through December 5, 2019 equal $2,002,228.

On February 14, 2017, the Company entered into a one-year research collaboration agreement with Cornell University in the amount of $679,473. On August 24, 2017, the agreement was amended to add an additional study in the amount of $182,520. Total research and development expenses under this agreement for the years ended December 31, 2018 and 2017 were $143,073 and $698,307, respectively.

License Agreements

Effective February 4, 2015, the Company entered into an exclusive worldwide license agreement with UCL Business, PLC (“UCL Business”) to develop up to eight programs using certain ocular gene therapy technology. Under the terms of the agreement, as amended, the Company will pay UCL Business certain sales milestone payments, if achieved, in the aggregate amount of £39.8 million, or approximately $50.7 million using the exchange rate at December 31, 2018, and royalties on net sales, as defined upon commercialization. Additionally, the Company is responsible for all patent prosecution and maintenance costs incurred and will also pay UCL Business an annual maintenance fee of £50,000, or approximately $64,000, until the first commercial sale of a product. The agreement will terminate upon the later of (i) the last valid claim in a relevant product, (ii) the expiration of regulatory exclusivity to all licensed products, or (iii) the 10^th anniversary of the first commercial sale of a product. Total research and development expenses under the agreement for the years ended December 31, 2018 and 2017 were $75,073 and $73,250, respectively.

Effective July 28, 2017, the Company entered into another exclusive worldwide license agreement with UCL Business for an additional program using certain ocular gene therapy technology. The Company will pay UCL Business certain milestone payments, royalties and annual maintenance fees under the same terms and conditions as the license dated February 4, 2015. Total research and development expenses under the agreement for the years ended December 31, 2018 and 2017 were $66,630 and $82,260, respectively.

Effective March 15, 2018, the Company entered into another exclusive worldwide license agreement with UCL Business for an additional program using certain ocular gene therapy technology. The Company will pay UCL Business certain milestone payments, royalties and annual maintenance fees under the same terms and conditions as the license dated February 4, 2015. Total research and development expenses under the agreement for the years ended December 31, 2018 and 2017 were $133,728 and $0, respectively.

On September 7, 2018, the Company entered into an exclusive licensing agreement with the National Institutes of Health for worldwide rights to expanded indications for use of AAV-AQP1 for treatment of xerostomia (dry mouth) and xerophthalmia (dry eye) associated with Sjögren’s syndrome. This agreement expands the Company’s original exclusive licensing agreement with the NIH for exclusive worldwide rights to AAV-AQP1 that was executed as of November 9, 2017. AAV-AQP1 is currently in Phase 1/2 development for treatment of grade 2 or 3 radiation-induced xerostomia. Total research and development expenses under the agreement for the years ended December 31, 2018 and 2017 were $50,000 and $0, respectively.

Effective January 1, 2016, the Company entered into an Agreement (“Agreement”) and Plan of Merger to acquire all of the outstanding shares of BRI-Alzan from the shareholders of BRI-Alzan. In connection with the Agreement, the Company will pay certain development milestone payments if achieved, in the aggregate amount of $4.5 million, and annual royalty payments on annual net sales following the first commercial sale of any product containing the technology acquired. Total research and development expenses under the agreement for the years ended December 31, 2018 and 2017 were $15,000 and $30,000, respectively.

Employee Benefit Plans

12 Months Ended

Dec. 31, 2018

Postemployment Benefits [Abstract]

Employee Benefit Plans

17.

Employee Benefit Plans

United States

On January 1, 2017, Meira LLC adopted a defined contribution retirement plan that complies with Section 401(k) of the Internal Revenue Code. All Meira LLC employees over the age of 21 are eligible to participate in the plan after three consecutive months of service. Employees are able to defer a portion of their pay into the plan on the first day of the month or after the day all age and service requirements have been met. The plan provides for a Company matching contribution. All eligible employees receive an employer matching contribution equal to the lesser of the amount the employee contributes to the plan or 6% of their salary up to the annual IRS limit.

United Kingdom

On August 1, 2016, Meira UK II adopted a defined contribution group personal pension plan that complies with HM Revenue and Customs (HMRC) for tax relief. All Meira UK II employees are eligible to participate in the plan upon joining the company and providing the required services. All eligible employees, if they elect to join the pension scheme, receive an employer pension contribution equal to 7.5% to 10.0% of their pensionable earnings. Currently, employees are not required to contribute, but may make optional contributions up to the annual allowance HMRC limits.

Under the HMRC requirements, current required 6+minimum employer contributions are 5-6% but will rise to 8-9% after April 2019.

During the years ended December 31, 2018 and 2017, employer contributions to all plans were $440,368 and $252,700, respectively.

Subsequent Events

12 Months Ended

Dec. 31, 2018

Subsequent Events [Abstract]

Subsequent Events

18.

Subsequent Events:

Management has evaluated subsequent events through the date these financial statements were issued. Based on our evaluation, the following disclosures have been made:

License Agreement

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, Plc (“UCLB”); (ii) the License Agreement, dated July 28, 2017, as amended, between the Company and UCLB; and (iii) the License Agreement, dated March 15, 2018, between the Company and UCLB to establish new stand-alone license agreements for the following inherited retinal disease programs: (a) achromatopsia (“ACHM”) caused by mutations in CNGB3; (b) ACHM caused by mutations in CNGA3; (c) X-linked retinitis pigmentosa (“XLRP”); and (d) RPE65-mediated IRD.

The Company’s obligation to pay UCLB 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, the new stand-alone agreement related to CNGB3 provides for the Company to pay UCLB an upfront payment of £1,500,000, or approximately $1,976,000, and issue £1,500,000 of the Company’s ordinary shares.

Collaboration Agreement

On January 30, 2019, (the “Agreement Date”), the Company entered into a Collaboration Agreement with Janssen Pharmaceuticals, Inc. (“Janssen”) for the research, development and commercialization of gene therapies for the treatment of inherited retinal diseases (“IRDs”).

Under the terms of the agreement, the Company will receive a $100 million cash upfront payment. 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 products globally. The Company will manufacture these products for commercial supply. Janssen will pay 100% of the clinical and commercialization costs of the products and the Company is eligible to receive untiered 20 percent royalties on net sales of products and additional development and commercialization milestones of up to $340 million. In addition, the Company and Janssen have entered into a research collaboration in the area of IRDs, 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 IND. Janssen will then pay 100% of the clinical and commercialization costs for these products and the Company will receive an untiered royalty on net sales in the high teens as well as development milestones. In addition, Janssen and the Company have entered into a manufacturing research collaboration to further develop processes for manufacturing AAV viral vectors in which the costs of the research will be shared.

Private Placement

On February 27, 2018, the Company issued 5,797,102 Ordinary Shares in a private placement for gross proceeds of $80 million, excluding offering costs of approximately $2.6 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, but in no event later than July 31, 2019, the Company shall prepare and file a registration statement covering the resale of all of the Registrable Securities, as defined in the agreement. The Company shall use commercially reasonable efforts to have the registration statement declared effective as soon as practicable. If the registration statement is not declared effective prior to the 120th day after July 31, 2019 (or the 150th day if the Securities and Exchange Commission reviews such registration statement), then the Company will make pro rata payments in cash to each investor then holding Registrable Securities, as liquidated damages, in an amount equal to 1% of the aggregate amount invested by such investor for each thirty (30)-day period or pro rata for any portion thereof following the date by which such registration statement should have been effective.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Consolidation

Consolidation

The accompanying consolidated financial statements include the accounts of Meira Holdings and its wholly owned subsidiaries:

MeiraGTx Limited, a limited company under the laws of England and Wales (“Meira Limited);

MeiraGTx, LLC, a Delaware corporation (“Meira LLC”);

BRI-Alzan, Inc., a Delaware corporation (“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

Subsequent Events

Subsequent Events

Cash and Cash Equivalents

Cash and Cash Equivalents

Warrant Liability

Warrant Liability

Financial Instruments

Financial Instruments

Fair Value Measurements

Fair Value Measurements

•

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	December 31, 2018		Significant Observable Inputs (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable (Level 3)
Restricted cash	$	123,376	$	123,376	$	—	$	—


	Fair Value Measurement Using:
Description	December 31, 2017		Significant Observable Inputs (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable (Level 3)
Restricted cash	$	123,376	$	123,376	$	—	$	—

Warrants	$	2,679,633	$	—	$	—	$	2,679,633

The table below represents a rollforward of the assets and liabilities that are required to be measured at fair value on a recurring basis from December 31, 2016 to December 31, 2018:


	Significant Observable Inputs (Level 1)			Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Balance as of December 31, 2016	$	444,844		$	—	$	—
Cash released from restriction		(321,468	)		—		—
Fair value of warrants issued		—			—		2,214,000
Change in fair value of warrants		—			—		465,633

Balance as of December 31, 2017		123,376			—		2,679,633
Change in fair value of warrants							1,514,775
Exercise of warrants		—			—		(4,194,408	)

Balance as of December 31, 2018	$	123,376		$	—	$	—

The fair values of the warrants were estimated using the Black-Scholes valuation model with the following assumptions:


	June 4, 2018			December 31, 2017			September 21, 2017
Risk-free interest rate		1.77	%		1.72	%		1.38	%
Expected volatility		80	%		80	%		80	%
Expected dividend yield		0			0			0
Expected life		1 day			9 months			18 months

The fair value of the Preferred Shares were based upon recent issuances of the Company’s Preferred Shares on or about those dates.

Convertible Preferred C Shares

Convertible Preferred C Shares

Concentrations of Credit Risk

Concentrations of Credit Risk

Property, Plant and Equipment, Net

Property, Plant and Equipment, Net

The estimated useful lives of the asset categories are set forth in the table below:


Asset Category	Useful Lives
Computer and office equipment		3 years
Laboratory equipment		5 years
Manufacturing equipment		7 years
Furniture and fixtures		5 years
Capitalized leasehold interest		25 years
Leasehold improvements		lesser of useful life or remaining term of lease

Expenditures for leasehold improvements are capitalized, and expenditures for maintenance and repairs are expensed to operations as incurred.

Net Loss per Ordinary Share

Net Loss per Ordinary Share

Income Taxes

Income Taxes

The Company is required to estimate income taxes in each of the jurisdictions in which it operates.

Research and Development

Research and Development

Share-Based Compensation Expense

Share-Based Compensation Expense

Options

Restricted Shares

Restricted Shares

Leases

Leases

Asset Retirement Obligation

Asset Retirement Obligation

The change in asset retirement obligations is as folows:


	For the year ended December 31,
	2018			2017
Balance at beginning of year	$	178,419		$	221,254
Inception of asset retirement obligation		69,286			—
Amortization of interest		(38,301	)		19,313
Change in estimate		(99,090	)		(75,011	)
Effects of exchange rate		17,805			12,863

Balance at end of year	$	128,119		$	178,419

Other Comprehensive Income (Loss)

Other Comprehensive Income (Loss)

Foreign Currencies

Foreign Currencies

Segment Information

Segment Information

Management has concluded it has a single reporting segment for purposes of reporting financial condition and results of operations.

The following table summarizes non-current assets by geographical area:


	December 31, 2018		December 31, 2017
United States	$	454,568	$	436,463
United Kingdom		21,788,130		13,942,642

	$	22,242,698	$	14,379,105

Accounting Pronouncements Recently Adopted

Accounting Pronouncements Recently Adopted

Recent Accounting Pronouncements Not Yet Adopted

Recent Accounting Pronouncements Not Yet Adopted

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

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	December 31, 2018		Significant Observable Inputs (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable (Level 3)
Restricted cash	$	123,376	$	123,376	$	—	$	—


	Fair Value Measurement Using:
Description	December 31, 2017		Significant Observable Inputs (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable (Level 3)
Restricted cash	$	123,376	$	123,376	$	—	$	—

Warrants	$	2,679,633	$	—	$	—	$	2,679,633

Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis

The table below represents a rollforward of the assets and liabilities that are required to be measured at fair value on a recurring basis from December 31, 2016 to December 31, 2018:


	Significant Observable Inputs (Level 1)			Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Balance as of December 31, 2016	$	444,844		$	—	$	—
Cash released from restriction		(321,468	)		—		—
Fair value of warrants issued		—			—		2,214,000
Change in fair value of warrants		—			—		465,633

Balance as of December 31, 2017		123,376			—		2,679,633
Change in fair value of warrants							1,514,775
Exercise of warrants		—			—		(4,194,408	)

Balance as of December 31, 2018	$	123,376		$	—	$	—

Fair Values of Warrants Estimated by Using Black-Scholes Valuation Model

The fair values of the warrants were estimated using the Black-Scholes valuation model with the following assumptions:


	June 4, 2018			December 31, 2017			September 21, 2017
Risk-free interest rate		1.77	%		1.72	%		1.38	%
Expected volatility		80	%		80	%		80	%
Expected dividend yield		0			0			0
Expected life		1 day			9 months			18 months

Schedule Of Estimated Useful Lives Of Assets

The estimated useful lives of the asset categories are set forth in the table below:


Asset Category	Useful Lives
Computer and office equipment		3 years
Laboratory equipment		5 years
Manufacturing equipment		7 years
Furniture and fixtures		5 years
Capitalized leasehold interest		25 years
Leasehold improvements		lesser of useful life or remaining term of lease

Schedule of change in asset retirement obligations

The change in asset retirement obligations is as folows:


	For the year ended December 31,
	2018			2017
Balance at beginning of year	$	178,419		$	221,254
Inception of asset retirement obligation		69,286			—
Amortization of interest		(38,301	)		19,313
Change in estimate		(99,090	)		(75,011	)
Effects of exchange rate		17,805			12,863

Balance at end of year	$	128,119		$	178,419

Summary of Non-Current Assets by Geographical Area

The following table summarizes non-current assets by geographical area:


	December 31, 2018		December 31, 2017
United States	$	454,568	$	436,463
United Kingdom		21,788,130		13,942,642

	$	22,242,698	$	14,379,105

Prepaid Expenses (Tables)

12 Months Ended

Dec. 31, 2018

Other Income and Expenses [Abstract]

Summary of Prepaid Expenses

Prepaid expenses at December 31, 2018 and 2017 consist of the following:


	December 31, 2018		December 31, 2017
Insurance	$	623,314	$	163,284
Clinical Trial Costs		373,723		839,644
Research and Development		352,658		624,348
Other		330,233		160,595
Dues and License Fees		169,073		145,594
Rent		88,784		27,778

	$	1,937,785	$	1,961,243

Property, Plant and Equipment, net (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Equipment, Net

Property, plant and equipment, net at December 31, 2018 and 2017 consist of the following:


	December 31, 2018			December 31, 2017
Leasehold Improvements	$	11,538,377		$	10,873,895
Capitalized Leasehold Interest		7,150,611			—
Manufacturing Equipment		3,779,950			2,477,637
Laboratory Equipment		1,485,544			993,409
Computer and Office Equipment		334,525			276,100
Asset Retirement Obligation		113,678			153,133
Furniture & Fixtures		88,660			93,786

		24,491,345			14,867,960
Less: Accumulated depreciation		(2,477,108	)		(612,231	)

	$	22,014,237		$	14,255,729

Capitalized Leases (Tables)

12 Months Ended

Dec. 31, 2018

Text Block [Abstract]

Schedule of Future Minimum Lease Payments

The following is a schedule, by year, of future minimum lease payments under the capital leases together with the present value of the net minimum lease payments as of December 31, 2018:


2019		28,715
2020		7,179

Total minimum lease payments		35,894
Less: amount representing interest		(1,598	)

Present value of net minimum lease payments		34,296
Less: current portion		(27,199	)

Obligations under capital lease, less current portion	$	7,097

Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

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

STOCK OPTION TABLE


	Number of Options			Weighted- Average Exercise Price			Aggregate Instrinsic Value
Outstanding at December 31, 2016		333,660		$	7.72
Granted		611,933			3.73
Exercised		(1,288	)		(7.57	)
Expired		—			—
Forfeited		(5,668	)		(7.72	)

Outstanding at December 31, 2017		938,637		$	5.12
Granted		2,334,285			8.63
Exercised		—			—
Expired		—			—
Forfeited		(10,557	)		(5.51	)

Outstanding at December 31, 2018		3,262,365		$	7.64		$	6,903,313

Weighted average remaining contractual life of options outstanding as of December 31, 2017 (yrs)		9.09

Weighted average remaining contractual life of options outstanding as of December 31, 2018 (yrs)		9.24

Options exercisable at December 31, 2017		186,394		$	7.72

Options exercisable at December 31, 2018		535,241		$	5.79

Weighted average remaining contractual life of options exercisable as of December 31, 2017 (yrs)		8.21

Weighted average remaining contractual life of options exercisable as of December 31, 2018 (yrs)		7.88

Schedule of Grant Date Fair Values of the Stock Option Granted

The grant date fair values of the stock options granted were estimated using the Black-Scholes option valuation model with the following ranges of assumptions (see Note 2):


	2018	2017
Risk-free interest rate	2.32% - 2.98%	2.28% - 2.51%
Expected volatility	90%	80%
Expected dividend yield	0%	0%
Expected life (in years)	5.5 - 10.0	5.5 - 10.0

Summary of Restricted Ordinary Shares

A summary of the restricted Ordinary Shares is as follows:


	Ordinary Shares			$ Value
Non-vested at December 31, 2016		386,608		$	3,020,191
Vesting during 2017		(280,695	)		(2,154,330	)

Non-vested at December 31, 2017		105,913			865,861
Issued during 2018		1,306,348			19,595,220
Vesting during 2018		(759,087	)		(10,663,471	)

Non-vested at December 31, 2018		653,174		$	9,797,610

Schedule of Share Based Compensation Expense


	2018		2017
Research and development	$	3,372,054	$	2,374,899
General and administrative		14,511,500		584,832

Total share based compensation	$	17,883,554	$	2,959,731

Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Schedule of Basic and Diluted Net Loss per Share

Basic and diluted net loss per share is computed as follows:


	2018			2017
Net loss—basic and diluted	$	(82,865,874	)	$	(31,044,535	)
Accretion of Preferred Shares financing costs		(1,806,512	)		(191,963	)
Accretion of warrant		—			(615,000	)

Adjusted net loss—basic and diluted	$	(84,672,386	)	$	(31,851,498	)
Weighted-average ordinary shares outstanding:
Basic and Diluted		18,948,520			8,572,315

Net loss per share:
Basic and Diluted	$	(4.47	)	$	(3.72	)

Schedule of Antidilutive Securities Excluded from Computation of Earnings per Share


	December 31, 2018		December 31, 2017
Preferred Shares		—		5,005,934
Restricted Ordinary Shares subject to forfeiture		653,174		105,913
Stock options		3,262,365		938,637
Warrants		—		927,594

		3,915,539		6,978,078

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of Company's Pre Tax Earnings

The Company’s pre tax earnings from the United Kingdom and United States locations are as follows:


	December 31, 2018			December 31, 2017
United Kingdom	$	(73,359,977	)	$	(26,458,625	)
United States		(9,980,287	)		(4,585,910	)

	$	(83,340,264	)	$	(31,044,535	)

Schedule of Reconciliation of Income Tax Benefit with Amounts at the U.K. Statutory Income Tax Rate

The following table summarizes a reconciliation of income tax benefit compared with the amounts at the U.K. statutory income tax rate:


	December 31, 2018					December 31, 2017
Statutory rate		(15,834,650	)	19.00	%		(5,976,073	)	19.25	%
Permanent differences—other		1,438,934		-1.73	%		654,648		-2.11	%
RTP and other adjustments		387,509		-0.46	%		(152,948	)	0.49	%
U.K. tax credit		1,707,489		-2.05	%		539,136		-1.74	%
U.S. tax credit		(436,250	)	0.52	%		(363,665	)	1.17	%
Foreign tax rate differential		(171,693	)	0.21	%		(673,619	)	2.17	%
State and local rate, net of federal tax		(1,159,522	)	1.39	%		(446,683	)	1.44	%
UK Rate Change (17% at expected DTA turn)		1,104,863		-1.33	%		482,351		-1.55	%
U.S. state rate change		(6,496	)	0.01	%		993,998		-3.20	%
Change in valuation allowance		12,495,426		-14.99	%		4,942,855		-15.92	%

Actual income tax benefit effective tax rate		(474,391	)	0.57	%		—		0.00	%

Schedule of Expense/(Benefit) for Income Taxes from Continuing Operations

The Expense/(Benefit) for income taxes from continuing operations consists of the following:


	December 31, 2018			December 31, 2017
Current Tax Expense/(Benefit)
United Kingdom		—			—
United States		—			—

Total Current		—			—
Deferred Tax Expense/(Benefit)
United Kingdom	$	(8,888,096	)	$	(3,759,109	)
United States		(3,606,275	)		(1,183,746	)

Total Deferred		(12,494,371	)		(4,942,855	)
Change in Valuation Allowance		12,019,880			4,942,855

Total Income Tax Expense/(Benefit)	$	(474,391	)	$	—

Schedule of Deferred Tax Assets and Liabilities

Deferred Tax Assets/(Liabilities)


	December 31, 2018
	Total			UK			US
Deferred Tax Assets:
Net operating loss carryforwards	$	20,646,185		$	16,000,329		$	4,645,856
Other		1,414,690			(46,604	)		1,461,294
Tax Credit		1,133,656			—			1,133,656

Deferred tax assets		23,194,531			15,953,725			7,240,806
Less: valuation allowance		(23,194,531	)		(15,953,725	)		(7,240,806	)

Net deferred tax asset	$	—		$	—		$	—


	December 31, 2017
	Total			UK			US
Deferred Tax Assets:
Net operating loss carryforwards	$	9,462,690		$	6,909,754		$	2,552,937
Other		539,008			152,554			386,454
Tax Credit		697,406			—			697,406

Deferred tax assets		10,699,105			7,062,308			3,636,797
Less: valuation allowance		(10,699,105	)		(7,062,308	)		(3,636,797	)

Net deferred tax asset	$	—		$	—		$	—

Commitments (Tables)

12 Months Ended

Dec. 31, 2018

Schedule of Future Minimum Rental Payments

The aggregate future minimum rental payments of all leases, including those discussed in Note 15 are as follows:


2019	$	889,465
2020	$	904,716
2021	$	924,121
2022	$	350,284
2023	$	350,284
Thereafter	$	1,196,805


Total future rent payments	$	4,615,675

July 27, 2018 Lease [Member]

Schedule of Future Minimum Rental Payments

The aggregate future minimum rental payments under these operating leases are as follows:


2019	$	353,782
2020	$	350,284
2021	$	350,284
2022	$	350,284
2023	$	350,284
Thereafter	$	1,196,805


Total future rent payments	$	2,951,723

Principal Business Activity - Additional Information (Detail)					12 Months Ended
	Feb. 27, 2019 USD ($) shares	Jan. 30, 2019 USD ($)	Jun. 07, 2018 USD ($) $ / shares shares	Mar. 01, 2018 shares	Dec. 31, 2018 USD ($) shares	Feb. 27, 2018 shares	Dec. 31, 2017 USD ($) shares
Schedule Of Description Of Business [Line Items]
Reverse share split ratio			0.257
Accumulated deficit					$ (148,289,717)		$ (65,423,843)
Cash and cash equivalents					$ 68,080,175		$ 8,548,638
Common stock, shares issued \| shares					27,386,632		8,826,190
Proceeds from the sale of ordinary shares					$ 69,750,000
Private Placement [Member]
Schedule Of Description Of Business [Line Items]
Common stock, shares issued \| shares						5,797,102
JJDC [Member] \| Private Placement [Member]
Schedule Of Description Of Business [Line Items]
Common stock, shares issued \| shares						2,898,550
Subsequent Event [Member] \| Collaboration Option And License Agreement [Member] \| JJDC [Member] \| Private Placement [Member]
Schedule Of Description Of Business [Line Items]
Common stock, shares issued \| shares	5,797,102
Proceeds from the sale of ordinary shares	$ 80,000,000
Proceeds from issuance of common stock, net	$ 77,400,000
Subsequent Event [Member] \| Collaboration Option And License Agreement [Member] \| Janssen Pharmaceuticals Inc [Member]
Schedule Of Description Of Business [Line Items]
Upfront payment		$ 100,000,000
Minimum [Member] \| Collaboration Option And License Agreement [Member] \| JJDC [Member]
Schedule Of Description Of Business [Line Items]
Offsetting expense, period					12 months
Ordinary shares [Member]
Schedule Of Description Of Business [Line Items]
Ordinary shares, issued \| shares			5,000,000	550,162
Ordinary shares, offering price \| $ / shares			$ 15.00
Proceeds from issuance initial public offering net			$ 65,200,000

Summary of Significant Accounting Policies - Company's Financial Assets and Liabilities Measured at Fair Value (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Restricted Cash [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, net asset (liability)	$ 123,376	$ 123,376
Warrants [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, net asset (liability)		2,679,633
Fair Value, Inputs, Level 1 [Member] \| Restricted Cash [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, net asset (liability)	$ 123,376	123,376
Fair Value, Inputs, Level 3 [Member] \| Warrants [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, net asset (liability)		$ 2,679,633

Summary of Significant Accounting Policies - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value of warrants	$ 1,514,775	$ 465,633
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning balance		444,844
Cash released from restriction		(321,468)
Ending balance	123,376	123,376
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of warrants issued		2,214,000
Change in fair value of warrants	1,514,775	465,633
Exercise of warrants	$ (4,194,408)
Ending balance		$ 2,679,633

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019	Jun. 05, 2018	Sep. 15, 2017	Dec. 31, 2016
Warrant liability		$ 2,679,633		$ 4,194,408
Change in fair value of warrants	$ 1,514,775	465,633
Exercise of warrants liability	4,194,408
Impairment charges	0	0
Liability for uncertainty in income taxes	0	$ 0
Unrecognized tax benefits, income tax penalties and interest accrued	$ 0
Statutory tax rate	19.00%	19.25%
Minimum [Member] \| Subsequent Event [Member]
Discount rate			8.00%
Operating lease right-of-use asset			$ 3,300,000
Operating lease liability			$ 3,600,000
Maximum [Member] \| Subsequent Event [Member]
Discount rate			10.00%
Operating lease right-of-use asset			$ 3,600,000
Operating lease liability			$ 3,800,000
Valuation Technique, Option Pricing Model [Member]
Pricing valuation of ordinary share		$ 5.63			$ 2.64	$ 7.57
Federal [Member]
Statutory tax rate	21.00%	34.00%
Capital in Excess of Nominal Value [Member]
Exercise of warrants liability	$ 4,194,408

Summary of Significant Accounting Policies - Fair Values of Warrants Estimated by Using Black-Scholes Valuation Model (Detail) - Warrants [Member]			12 Months Ended
	Jun. 04, 2018	Sep. 21, 2017	Dec. 31, 2017
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Risk-free interest rate	1.77%	1.38%	1.72%
Expected volatility	80.00%	80.00%	80.00%
Expected dividend yield	0.00%	0.00%	0.00%
Expected life	1 day	18 months	9 months

Summary of Significant Accounting Policies - Schedule Of Estimated Useful Lives Of Assets (Detail)	12 Months Ended
	Dec. 31, 2018
Computer Equipment And Software [Member]
Depreciation Amortization Impairment [Line Items]
Estimated useful life (years)	3 years
Laboratory Equipment [Member]
Depreciation Amortization Impairment [Line Items]
Estimated useful life (years)	5 years
Manufacturing Equipment [Member]
Depreciation Amortization Impairment [Line Items]
Estimated useful life (years)	7 years
Furniture & Fixtures [Member]
Depreciation Amortization Impairment [Line Items]
Estimated useful life (years)	5 years
Capitalized Leasehold Interest [Member]
Depreciation Amortization Impairment [Line Items]
Estimated useful life (years)	25 years
Leasehold Improvements [Member]
Depreciation Amortization Impairment [Line Items]
Estimated useful life (years)	lesser of useful life or remaining term of lease

Summary of Significant Accounting Policies - Schedule of Change in Asset Retirement Obligations (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Asset Retirement Obligation [Abstract]
Balance at beginning of year	$ 178,419	$ 221,254
Inception of asset retirement obligation	69,286
Amortization of interest	(38,301)	19,313
Change in estimate	(99,090)	(75,011)
Effects of exchange rate	17,805	12,863
Balance at end of year	$ 128,119	$ 178,419

Asset Acquisition - Additional Information (Detail) - USD ($)		12 Months Ended
	Oct. 05, 2018	Dec. 31, 2018
Acquisition Date [Line Items]
Fair value of asset acquisition in process R&D	$ 2,990,250
Contingent milestone payment		$ 21,000,000
Vector Neurosciences Inc [Member]
Acquisition Date [Line Items]
Number of shares issued as initial merger consideration	225,000
Agreement date	Oct. 05, 2018
Period of shares issued as initial merger consideration	18 months
Vector Neurosciences Inc [Member] \| Maximum [Member]
Acquisition Date [Line Items]
Value of stockholders additional ordinary shares	$ 21,000,000
Vector Neurosciences Inc [Member] \| Issued at Closing of Merger [Member]
Acquisition Date [Line Items]
Number of shares issued as initial merger consideration	202,500
Vector Neurosciences Inc [Member] \| Issued Following Closing of Merger [Member]
Acquisition Date [Line Items]
Number of shares issued as initial merger consideration	22,500

Prepaid Expenses - Summary of Prepaid Expenses (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Insurance	$ 623,314	$ 163,284
Clinical Trial Costs	373,723	839,644
Research and Development	352,658	624,348
Other	330,233	160,595
Dues and License Fees	169,073	145,594
Rent	88,784	27,778
Total	$ 1,937,785	$ 1,961,243

Property, Plant and Equipment, Net - Schedule of Property, Plant and Equipment, Net (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 24,491,345	$ 14,867,960
Less: Accumulated depreciation	(2,477,108)	(612,231)
Property, plant and equipment, net	22,014,237	14,255,729
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	11,538,377	10,873,895
Capitalized Leasehold Interest [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,150,611
Manufacturing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	3,779,950	2,477,637
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,485,544	993,409
Computer and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	334,525	276,100
Asset Retirement Obligation [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	113,678	153,133
Furniture & Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 88,660	$ 93,786

Property, Plant & Equipment, Net - Additional Information (Detail)				1 Months Ended	12 Months Ended
	Dec. 14, 2018 USD ($)	Dec. 14, 2018 GBP (£)	Jul. 31, 2018 Lease	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2018 GBP (£)	Feb. 29, 2016 USD ($)
Property, Plant and Equipment [Line Items]
Asset retirement obligations, noncurrent				$ 140,129	$ 140,129
Asset retirement obligation				128,119	128,119	$ 178,419	$ 221,254
Number of operating leases \| Lease			2
Capitalized lease obligation				7,097	7,097	34,298
Depreciation expense					2,053,220	679,177
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Asset retirement obligation				69,286	69,286
Capitalized Leasehold Interest [Member]
Property, Plant and Equipment [Line Items]
Capital lease obligations				7,150,611	7,150,611
Accumulated depreciation				6,928	6,928
Computer and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Capitalized lease obligation				95,880	95,880	95,880
Accumulated depreciation				$ 62,912	$ 62,912	$ 34,552
Operating Sublease [Member]
Property, Plant and Equipment [Line Items]
Lessee operating Lease, term of contract	108 years	108 years		108 years	108 years			108 years	5 years
Payment of operating lease base rent	$ 6,615,000	£ 5,250,000
Lessee operating Lease, additional term of lease									5 years
Capital lease obligations				$ 7,150,611	$ 7,150,611			£ 5,613,165
Capital lease assets amortization period	25 years	25 years		25 years
Exchange rate	1.2600	1.2600		1.2739	1.2739			1.2739
Asset retirement obligations, noncurrent									$ 306,400
Asset retirement obligations, discounted rate							8.00%
Asset retirement obligation remeasurement period						8 years
Operating Sublease [Member] \| Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Asset retirement obligation							$ 205,659
Asset retirement obligation recorded in leasehold improvements	$ (99,090)					$ (75,011)

Restricted Cash - Additional Information (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Other Noncurrent Liabilities [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 123,376	$ 123,376

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Compensation and Benefits	$ 5,731,438	$ 2,386,903
Clinical Trial Costs	4,013,094	4,859,410
Professional Fees	914,540	231,923
Consulting	821,009	1,220,477
Research and Development	236,271	73,379
Rent	122,770	387,267
Interest	40,800	33,437
Other	111,775	140,148
Accrued expenses	$ 11,991,697	$ 9,332,944

Capitalized Leases - Additional Information (Detail)		1 Months Ended	12 Months Ended
Capitalized Leases - Additional Information (Detail)	Dec. 14, 2018	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2018 GBP (£)	Feb. 29, 2016
Operating Sublease [Member]
Lessee operating Lease, renewal term	108 years	108 years			108 years	5 years
Capitalized lease, leasehold percentage		75.00%
Capital lease assets amortization period	25 years	25 years
Capital lease obligations		$ 7,150,611			£ 5,613,165
Office Equipment [Member]
Assets acquired			$ 78,063	$ 17,817
Lease arrangement period			3 years	3 years
Capital lease amount			$ 86,145	$ 20,502
Capital lease interest rate			6.90%	9.35%

Capitalized Leases - Schedule of Future Minimum Lease Payments (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Leases [Abstract]
2019	$ 28,715
2020	7,179
Total minimum lease payments	35,894
Less: amount representing interest	(1,598)
Present value of net minimum lease payments	34,296
Less: current portion	(27,199)	$ (30,850)
Obligations under capital lease, less current portion	7,097	$ 34,298
Present value of net minimum lease payments	$ 34,296

Notes Payable - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Oct. 26, 2017
Debt Disclosure [Abstract]
Promissory note issued				$ 1,442,009
Promissory note rate of interest		5.00%
Promissory note expiration due date		Dec. 31, 2018
Repayment of promissory note	$ 1,472,433
Interest expense		$ 33,429	$ 42,863

Collaboration Agreement - Additional Information (Detail) - Janssen Pharmaceuticals Inc [Member] - Collaboration Agreement [Member]	12 Months Ended
	Dec. 31, 2018 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred research funding	$ 658,667
Deferred research funding, amortization period	8 months
Research and Development Expenses [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amortized of deferred research funding	$ 224,576
Other Current Liabilities [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred research funding	$ 434,091

Share based Compensation - Additional Information (Detail) - USD ($)			12 Months Ended
	Jun. 07, 2018	Mar. 01, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average remaining contractual life of options outstanding			9 years 2 months 26 days	9 years 1 month 2 days
Fair value of options Vested			$ 1,387,607	$ 898,699
Share options granted during the period			2,334,285	611,933
Fully-diluted outstanding shares	5.00%
Share based compensation			$ 17,883,554	$ 2,959,731
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]
Ordinary shares awarded, per share	$ 15.00
Fully-diluted outstanding shares		3.00%
Share based compensation		$ 3,096,104	$ 6,456,215
Ordinary shares, issued	5,000,000	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		1,306,348
Ordinary shares forfeiture period					3 years
Ordinary shares awarded, per share	$ 15.00
Fully-diluted outstanding shares	5.00%
Share based compensation			$ 20,141,876
Restricted Shares [Member] \| General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation			$ 10,156,868
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			2,334,285	611,933
Total unvested options compensation expense			$ 17,415,098	$ 987,413
Unvested options expected to be realized			4 years	3 years 5 months 1 day
Weighted average grant date fair value of options granted			$ 6.53	$ 3.10
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 - Summary of Company's Share Option Activity Related to Employees, Non-Employee Members of the Board of Directors and Non-Employee Consultants (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of options, Beginning balance	938,637	333,660
Number of options, Granted	2,334,285	611,933
Number of options, Exercised		1,288
Number of options, Expired	0	0
Number of options, Forfeited	(10,557)	(5,668)
Number of options, Ending balance	3,262,365	938,637
Weighted- average exercise price, beginning balance	$ 5.12	$ 7.72
Weighted average remaining contractual life of options outstanding	9 years 2 months 26 days	9 years 1 month 2 days
Weighted- average exercise price, granted	$ 8.63	$ 3.73
Number of options, Options exercisable	535,241	186,394
Weighted- average exercise price, exercised		$ 7.57
Weighted average remaining contractual life of options Exercisable	7 years 10 months 17 days	8 years 2 months 15 days
Weighted- average exercise price, expired	$ 0	$ 0
Weighted- average exercise price, forfeited	(5.51)	(7.72)
Weighted- average exercise price, ending balance	7.64	5.12
Weighted- average exercise price, option Exercisable	$ 5.79	$ 7.72
Aggregate Intrinsic Value	$ 6,903,313
Aggregate Intrinsic Value, Options Exercisable	$ 0	$ 0

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]	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.32%	2.28%
Risk-free interest rate	2.98%	2.51%
Expected volatility	90.00%	80.00%
Expected dividend yield	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of non-employee options (in years)	5 years 6 months	5 years 6 months
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of non-employee options (in years)	10 years	10 years

Share Based Compensation - Summary of Restricted Ordinary Shares (Detail) - Restricted Shares [Member] - USD ($)		12 Months Ended
	Jun. 07, 2018	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested Ordinary Shares, Beginning Balance		105,913	386,608
Issued, Ordinary Shares	1,306,348	1,306,348
Issued, Value		$ 19,595,220
Vesting, Ordinary Shares		(759,087)	(280,695)
Non-vested Ordinary Shares, Ending Balance		653,174	105,913
Non-vested Value, Beginning Balance		$ 865,861	$ 3,020,191
Vesting, Value		(10,663,471)	(2,154,330)
Non-vested Value, Ending Balance		$ 9,797,610	$ 865,861

Share Based Compensation - Schedule of Share Based Compensation Expense (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Expense [Line Items]
Total share based compensation	$ 17,883,554	$ 2,959,731
Research and Development Expenses [Member]
Share Based Compensation Expense [Line Items]
Total share based compensation	3,372,054	2,374,899
General and Administrative Expense [Member]
Share Based Compensation Expense [Line Items]
Total share based compensation	$ 14,511,500	$ 584,832

Ordinary Shares, Convertible Preferred C Shares and Shareholders' Deficit - Additional Information (Detail) - USD ($)										12 Months Ended
	Oct. 05, 2018	Jun. 07, 2018	Jun. 05, 2018	Mar. 15, 2018	Mar. 01, 2018	Nov. 02, 2017	Sep. 21, 2017	Aug. 16, 2017	Jul. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015
Percentage of fully diluted shares		5.00%
Stock issued during period, shares, stock options exercised											1,288
Gross proceeds from preferred shares										$ 56,849,594	$ 16,854,653
Conversion of note payable into convertible preferred C shares, shares						238,579
Preferred share conversion value		$ 664,718								1,806,512	191,963
Conversion of note payable into convertible preferred C shares						$ 2,500,000				$ 120,520,391
Preferred shares, purchase			927,594				695,696
Preferred shares, exercise price			$ 10.48				$ 10.48			$ 2.70
Accretion of warrants issued in connection with convertible preferred shares							$ 1,660,500			$ (1,045,500)	(615,000)
Convertible note inducement expense											553,500
Change in fair value of warrant liability										1,514,775	465,633
Warrant liability			$ 4,194,408								$ 2,679,633
Preferred shares, value			$ 9,720,000							$ 9,720,000
Vector Neurosciences Inc [Member]
Number of shares issued as initial merger consideration	225,000
Period of shares issued as initial merger consideration	18 months
Vector Neurosciences Inc [Member] \| Issued at Closing of Merger [Member]
Number of shares issued as initial merger consideration	202,500
Vector Neurosciences Inc [Member] \| Issued Following Closing of Merger [Member]
Number of shares issued as initial merger consideration	22,500
Restricted Shares [Member]
Ordinary shares, offering price		$ 15.00
Ordinary shares		1,306,348								1,306,348
Percentage of fully diluted shares		5.00%
Ordinary shares [Member]
Ordinary shares, issued		5,000,000			550,162
Ordinary shares, offering price		$ 15.00
Proceeds from issuance initial public offering		$ 75,000,000
Offering costs		$ 9,807,622								$ 4,115,843
Percentage of fully diluted shares					3.00%
Stock issued during period, shares, stock options exercised									1,288		1,288
Conversion of note payable into convertible preferred C shares, shares		11,501,432								11,501,432
Conversion of note payable into convertible preferred C shares										$ 446
Ordinary shares [Member] \| Research Agreement [Member]
Ordinary shares, issued								6,441
Ordinary shares [Member] \| Restricted Shares [Member]
Ordinary shares												867,935
Preferred Shares [Member]
Ordinary shares, issued							715,737			5,425,124
Ordinary shares, offering price							$ 10.48			$ 10.48
Offering costs										$ 690,473	$ 98,804
Gross proceeds from preferred shares										56,849,611	$ 16,854,656
Conversion of note payable into convertible preferred C shares, shares						238,579
Conversion rate of note payable into convertible preferred shares						10.48
Preferred Shares [Member] \| Issued at Closing of Merger [Member]
Ordinary shares, issued											9,739
Ordinary shares, offering price											$ 20.96
Preferred Shares [Member] \| Issued Following Closing of Merger [Member]
Ordinary shares, issued											1,598,418
Ordinary shares, offering price											$ 10.48
Convertible Preferred C Shares [Member]
Offering costs										$ 690,475
Conversion of note payable into convertible preferred C shares, shares										(11,501,432)	238,579
Conversion of note payable into convertible preferred C shares										$ (120,520,391)	$ 2,500,000
Preferred shares, purchase										927,594
Convertible Preferred C Shares [Member] \| License Agreement [Member]
Ordinary shares, issued				13,360						13,360
Convertible Preferred C Shares [Member] \| Payments In Lieu [Member]
Ordinary shares, issued										129,419
Shares issued, value										$ 1,355,097

Net Loss per Share - Schedule of Basic and Diluted Net Loss per Share (Detail) - USD ($)		12 Months Ended
	Jun. 07, 2018	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net loss-basic and diluted		$ (82,865,874)	$ (31,044,535)
Accretion of Preferred Shares financing costs	$ (664,718)	(1,806,512)	(191,963)
Accretion of warrant			(615,000)
Adjusted net loss-basic and diluted		$ (84,672,386)	$ (31,851,498)
Weighted-average ordinary shares outstanding:
Basic and Diluted		18,948,520	8,572,315
Net loss per share:
Basic and Diluted		$ (4.47)	$ (3.72)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Net Loss per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earning per share, amount	3,915,539	6,978,078
Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earning per share, amount		5,005,934
Restricted Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earning per share, amount	653,174	105,913
Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earning per share, amount	3,262,365	938,637
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 Information (Detail) - USD ($)			12 Months Ended
	Apr. 01, 2020	Apr. 01, 2017	Dec. 31, 2018	Dec. 31, 2017
Income Taxes Disclosure [Line Items]
Income tax expense (benefit)			$ (474,391)	$ 0
Federal net operating loss carryforwards			14,210,000	6,800,000
State net operating loss carryforwards			14,155,000	$ 6,700,000
Foreign net operating loss carryforwards			$ 94,100,000
Income tax operating loss carryforward expiration date			2036	2036
Deferred tax assets, tax credit carryforwards, orphan drug and research and development			$ 1,133,656	$ 697,406
Deferred tax assets, tax credit carryforwards, expiration year			2036
Provision for valuation allowance			$ 0
Foreign currency translation, tax			$ 474,391	$ 0
Foreign tax rate differential			17.00%
Foreign tax rate differential		19.00%	0.21%	2.17%
Effective income tax rate reconciliation, at federal statutory Income tax rate, percent			19.00%	19.25%
Decrease in the prior years deferred tax assets			$ 994,000
Federal [Member]
Income Taxes Disclosure [Line Items]
Deferred tax assets, tax credit carryforwards, orphan drug and research and development			$ 1,133,656	$ 697,406
Effective income tax rate reconciliation, at federal statutory Income tax rate, percent			21.00%	34.00%
Scenario, Forecast [Member]
Income Taxes Disclosure [Line Items]
Foreign tax rate differential	17.00%
Foreign tax rate differential	18.00%

Income Taxes - Summary of Company's Pre Tax Earnings (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Before Income Taxes [Line Items]
Total	$ (82,865,874)	$ (31,044,535)
U.K. [Member]
Income Before Income Taxes [Line Items]
Total	(73,359,977)	(26,458,625)
Federal [Member]
Income Before Income Taxes [Line Items]
Total	$ (9,980,287)	$ (4,585,910)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Income Taxes - Summary of Reconciliation of Income Tax Benefit with Amounts at the U.K. Statutory Income Tax Rate (Detail) - USD ($)		12 Months Ended
	Apr. 01, 2017	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Statutory rate		$ (15,834,650)	$ (5,976,073)
Permanent differences-other		1,438,934	654,648
RTP and other adjustments		387,509	(152,948)
U.K. tax credit		1,707,489	539,136
U.S. tax credit		(436,250)	(363,665)
Foreign tax rate differential		(171,693)	(673,619)
State and local rate, net of federal tax		(1,159,522)	(446,683)
UK Rate Change (17% at expected DTA turn)		1,104,863	482,351
U.S. state rate change		(6,496)	993,998
Change in valuation allowance		12,495,426	4,942,855
Actual income tax benefit effective tax rate		$ (474,391)	$ 0
Statutory rate		19.00%	19.25%
Permanent differences-other		(1.73%)	(2.11%)
RTP and other adjustments		(0.46%)	0.49%
U.K. tax credit		(2.05%)	(1.74%)
U.S. tax credit		0.52%	1.17%
Foreign tax rate differential	19.00%	0.21%	2.17%
State and local rate, net of federal tax		1.39%	1.44%
UK Rate Change (17% at expected DTA turn)		(1.33%)	(1.55%)
U.S. state rate change		0.01%	(3.20%)
Change in valuation allowance		(14.99%)	(15.92%)
Actual income tax benefit effective tax rate		0.57%	0.00%

Income Taxes - Schedule of Expense/(Benefit) for Income Taxes from Continuing Operations (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Current Tax Expense/(Benefit)
United Kingdom	$ 0	$ 0
United States	0	0
Total Current	0	0
Deferred Tax Expense/(Benefit)
United Kingdom	(8,888,096)	(3,759,109)
United States	(3,606,275)	(1,183,746)
Total Deferred	(12,494,371)	(4,942,855)
Change in valuation allowance	12,495,426	4,942,855
Actual income tax benefit effective tax rate	$ (474,391)	$ 0

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets:
Net operating loss carryforwards	$ 20,646,185	$ 9,462,690
Other	1,414,690	539,008
Tax Credit	1,133,656	697,406
Deferred tax assets	23,194,531	10,699,105
Less: valuation allowance	(23,194,531)	(10,699,105)
Net deferred tax asset	0	0
U.K. [Member]
Deferred Tax Assets:
Net operating loss carryforwards	16,000,329	6,909,754
Other	(46,604)	152,554
Deferred tax assets	15,953,725	7,062,308
Less: valuation allowance	(15,953,725)	(7,062,308)
Net deferred tax asset	0	0
Federal [Member]
Deferred Tax Assets:
Net operating loss carryforwards	4,645,856	2,552,937
Other	1,461,294	386,454
Tax Credit	1,133,656	697,406
Deferred tax assets	7,240,806	3,636,797
Less: valuation allowance	(7,240,806)	(3,636,797)
Net deferred tax asset	$ 0	$ 0

Related Party Transactions - Additional Information (Detail)				5 Months Ended	12 Months Ended
	Nov. 02, 2017 USD ($) $ / shares shares	May 01, 2017 USD ($)	Apr. 24, 2015	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($)	Dec. 31, 2017 GBP (£)	Oct. 31, 2020 USD ($)	Oct. 31, 2020 GBP (£)	Jun. 05, 2018 $ / shares	Oct. 26, 2017 USD ($)	Sep. 21, 2017 $ / shares
Related Party Transaction [Line Items]
Amount due under services agreement					$ 0	$ 861,030
Related party transaction amounts of work orders issued					570,525	593,933
Research and development expenses					33,620,223	22,359,712
Aggregate future minimum rental payments under operating lease					$ 4,615,675
Promissory note issued											$ 1,442,009
Convertible notes payable, interest rate		10.00%
Conversion of note payable into convertible preferred shares \| shares	238,579
Conversion rate of note payable into convertible preferred shares \| $ / shares	$ 2.70
Accrued interest cancelled	$ 145,833
Warrant to purchase preferred shares \| shares					900,000
Warrant exercise price \| $ / shares					$ 2.70					$ 10.48		$ 10.48
ARE [Member]
Related Party Transaction [Line Items]
Note payable to related party, amount		$ 2,500,000
Transition Services Agreement with Related Party [Member] \| Kadmon [Member]
Related Party Transaction [Line Items]
Percentage of administrative fees			7.00%
Services termination date			Apr. 24, 2018
Ownership percentage by related party			12.90%
Cash payment					$ 1,431,555	275,941
July 2016 Lease [Member]
Related Party Transaction [Line Items]
Operating lease expiration date					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.
Deferred rent					$ 201,264	231,276
Operating lease rent expenses					487,555	487,559
Aggregate future minimum rental payments under operating lease					1,663,952
Letter of credit outstanding amount					$ 122,866
December 2016 [Member]
Related Party Transaction [Line Items]
Operating lease expiration date					Oct. 31, 2032
Operating leases rent expense payment description					The Company recorded monthly rent expense on a straight-line basis from December 15, 2016 through October 31, 2032.
Operating lease rent expenses					$ 0	1,660,806
Operating lease termination date					Mar. 31, 2018
Base rent and management fees				$ 563,507
Promissory note issued											$ 1,442,009
UCL Consultants Limited [Member] \| Research Agreement [Member]
Related Party Transaction [Line Items]
Amount due under services agreement					$ 389,101	775,315
Related party transaction amounts of work orders issued						1,885,000	£ 1,402,202
Agreement termination notice period					30 days
Research and development expenses					$ 636,000	538,000
UCL Consultants Limited [Member] \| Manufacturing Agreement [Member]
Related Party Transaction [Line Items]
Amount due under services agreement					0	2,466,142
Research and development expenses					$ 0	$ 1,904,352
Agreement termination date					2018-01
UCL Consultants Limited [Member] \| Scenario, Forecast [Member] \| Research Agreement [Member]
Related Party Transaction [Line Items]
Future obligations under agreement								$ 779,685	£ 612,382

Related Party Transactions - Incurred Charges included in Loss from Operations (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Total charges incurred	$ 570,525	$ 593,933
Rent [Member]
Related Party Transaction [Line Items]
Total charges incurred	557,698	548,229
Personnel [Member]
Related Party Transaction [Line Items]
Total charges incurred	6,493	39,721
Other [Member]
Related Party Transaction [Line Items]
Total charges incurred	$ 6,334	$ 5,983

Commitments - Additional Information (Detail)												1 Months Ended			12 Months Ended
Commitments - Additional Information (Detail)	Mar. 25, 2021 USD ($)	Jul. 27, 2018 USD ($) Lease	Jun. 07, 2018 $ / shares shares	Mar. 01, 2018	Aug. 24, 2017 USD ($)	Dec. 05, 2016 USD ($) shares	Mar. 22, 2016 USD ($)	Sep. 28, 2015 $ / shares shares	Apr. 24, 2015 $ / shares shares	Feb. 04, 2015 EUR (€) Program	Feb. 04, 2015 USD ($) Program	Dec. 31, 2018 EUR (€)	Apr. 30, 2017 USD ($)	Feb. 14, 2017 USD ($)	Dec. 31, 2018 EUR (€) Lease shares	Dec. 31, 2018 USD ($) Lease shares	Jan. 31, 2018 USD ($)	Dec. 31, 2017 EUR (€) shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2015	Dec. 05, 2019 USD ($)	Dec. 31, 2018 USD ($)	Oct. 01, 2017	Jan. 01, 2016 USD ($)
Other Commitments [Line Items]
Research and development expenses																$ 33,620,223			$ 22,359,712
General and administrative expense																$ 44,483,938			$ 9,325,017
Ordinary share \| shares															2,334,285	2,334,285		611,933	611,933
Service Agreements [Member]
Other Commitments [Line Items]
Employees aggregate compensation \| €															€ 300,000
Research and development expenses															1,001,000	$ 1,334,000		€ 724,000	$ 933,000
Future obligations under agreement												€ 150,333			€ 150,333							$ 192,000
Employment Agreements [Member]
Other Commitments [Line Items]
Employees aggregate compensation																	$ 710,000
Future obligations under agreement																						1,258,750
Agreegate discretionary bonus																3,415,000	$ 1,196,000		850,000
Employee agreement description																	The employment agreements also provide for an annual guaranteed cash bonus targeted at 100% of annual compensation. The agreements also provide for discretionary annual performance bonuses targeted to be not less than 50-60% of the employee's base salary and grants of restricted stock.
Employment agreement term																	3 years
Percentage of fully-diluted outstanding shares			5.00%	3.00%
Consulting And Other Agreements [Member]
Other Commitments [Line Items]
General and administrative expense																263,970			351,960
Research Agreement One [Member]
Other Commitments [Line Items]
Research and development expenses																$ 418,000			418,000
Consulting agreement term							5 years
Quarterly payment received for Research and development agreement							$ 104,500
Restricted Shares [Member]
Other Commitments [Line Items]
Employees share award \| shares			1,306,348												1,306,348	1,306,348
Employees share award, per share \| $ / shares			$ 15.00
Ordinary shares forfeiture period																				3 years
Restricted Shares [Member] \| Service Agreements [Member]
Other Commitments [Line Items]
Employees share award \| shares									2,704,800
Employees share award, per share \| $ / shares									$ 7.76
Ordinary shares forfeiture period									3 years
Restricted Shares [Member] \| Consulting And Other Agreements [Member]
Other Commitments [Line Items]
Employees share award \| shares								662,910
Ordinary shares forfeiture period								3 years
Restricted Shares [Member] \| Director [Member] \| Consulting And Other Agreements [Member]
Other Commitments [Line Items]
Consulting agreement term								3 years
Maximum [Member] \| Service Agreements [Member]
Other Commitments [Line Items]
Employees aggregate compensation															€ 410,000	$ 522,000
Maximum [Member] \| Employment Agreements [Member]
Other Commitments [Line Items]
Employees aggregate compensation																	$ 1,075,000
Percentage of fully-diluted outstanding shares															8.00%	8.00%
General and Administrative Expense [Member] \| Restricted Shares [Member] \| Consulting And Other Agreements [Member]
Other Commitments [Line Items]
Employees share award, per share \| $ / shares								$ 7.72
U.S. Department Of Health And Human Services [Member] \| Research Agreement [Member]
Other Commitments [Line Items]
Research and development expenses																$ 111,938			115,374
Quarterly payment received for Research and development agreement													$ 21,250
Agreement amended date									Mar. 25, 2016
Agreement expiration date									Apr. 30, 2017
Research agreement payment received period									3 years
Cornell University [Member] \| Research Agreement [Member]
Other Commitments [Line Items]
Research and development expenses																143,073			698,307
Agreement amended date						Jun. 12, 2017
Research and collaboration agreement period						3 years
Ordinary share \| shares						25,000
Research and collaboration agreement period														1 year
Research and collaboration agreement amount														$ 679,473
Cornell University [Member] \| Issued at Closing of Merger [Member] \| Research Agreement [Member]
Other Commitments [Line Items]
Research and development expenses						$ 17,000										1,625,152			1,029,904
Cornell University [Member] \| Issued Following Closing of Merger [Member] \| Research Agreement [Member]
Other Commitments [Line Items]
Research and development amended agreement amount					$ 182,520
National Institutes of Health [Member] \| License Agreement [Member]
Other Commitments [Line Items]
Research and development expenses																50,000			0
BRI-Alzan [Member] \| License Agreement [Member]
Other Commitments [Line Items]
Research and development expenses																15,000			30,000
Sales milestone payments																								$ 4,500,000
Scenario, Forecast [Member] \| U.S. Department Of Health And Human Services [Member] \| Research Agreement [Member]
Other Commitments [Line Items]
Future obligations under agreement	$ 191,250
Agreement expiration date	Mar. 25, 2021
Scenario, Forecast [Member] \| Cornell University [Member] \| Research Agreement [Member]
Other Commitments [Line Items]
Future obligations under agreement																					$ 2,002,228
License Agreements Effective February 4, 2015 [Member] \| UCL Business, PLC [Member] \| License Agreement [Member]
Other Commitments [Line Items]
Research and development expenses																75,073			73,250
Number of collaborations programs \| Program										8	8
Sales milestone payments										€ 39,800,000												50,700,000
Maintenance fee										€ 50,000	$ 64,000
License Agreement Effective July 28, 2017 [Member] \| UCL Business, PLC [Member] \| License Agreement [Member]
Other Commitments [Line Items]
Research and development expenses																66,630			82,260
License Agreements Effective March 15, 2018 [Member] \| UCL Business, PLC [Member] \| License Agreement [Member]
Other Commitments [Line Items]
Research and development expenses																133,728			0
July 27, 2018 Lease [Member] \| London UK [Member]
Other Commitments [Line Items]
Operating lease rent expense																148,561			0
Annual base rent		$ 363,000
Operating lease termination date		May 24, 2027
Number of leases expired \| Lease		2
Number of new leases \| Lease		2
February,2016 Lease [Member] \| London UK [Member]
Other Commitments [Line Items]
Operating lease expiration												2021-02
Operating lease rent expense																$ 273,430			279,303
October 1,2017 Lease [Member] \| Leiden Netherland [Member]
Other Commitments [Line Items]
Operating lease expiration															2018-09	2018-09
Operating lease rent expense																$ 9,313			5,273
Term of non-cancellable operating lease															1 year	1 year
October 1,2017 Lease [Member] \| Leiden Netherland [Member] \| Minimum [Member]
Other Commitments [Line Items]
Operating lease, renewal Term																							1 year
October 1,2017 Lease [Member] \| Leiden Netherland [Member] \| Maximum [Member]
Other Commitments [Line Items]
Operating lease, renewal Term																							4 years
June 2017 Lease [Member] \| London UK [Member]
Other Commitments [Line Items]
Operating lease expiration															2018-07	2018-07
Operating lease rent expense																$ 73,846			$ 85,222
Deferred rent																						$ 0
Operating leases rent expense payment description															The Company records monthly rent expense on a straight-line basis from June 1, 2017 through July 23, 2018.	The Company records monthly rent expense on a straight-line basis from June 1, 2017 through July 23, 2018.
Number of non cancellable operating leases \| Lease															2	2

Commitments - Schedule of Future Minimum Rental Payments (Detail) - USD ($)	Dec. 31, 2018	Jul. 27, 2018
Operating Leased Assets [Line Items]
2019	$ 889,465
2020	904,716
2021	924,121
2022	350,284
2023	350,284
Thereafter	1,196,805
Total future rent payments	$ 4,615,675
July 27, 2018 Lease [Member]
Operating Leased Assets [Line Items]
2019		$ 353,782
2020		350,284
2021		350,284
2022		350,284
2023		350,284
Thereafter		1,196,805
Total future rent payments		$ 2,951,723

Employee Benefit Plans - Additional Information (Detail) - USD ($)					12 Months Ended
	May 01, 2019	Apr. 30, 2019	Jan. 01, 2017	Aug. 01, 2016	Dec. 31, 2018	Dec. 31, 2017
United States
Compensation And Retirement Disclosure [Line Items]
Defined contribution plan, annual contributions per employee, percent			6.00%
United States \| Minimum [Member]
Compensation And Retirement Disclosure [Line Items]
Defined contribution plan employee eligibility age			21 years
United Kingdom [Member]
Compensation And Retirement Disclosure [Line Items]
Defined benefit plan, plan assets, contributions by employer					$ 440,368	$ 252,700
United Kingdom [Member] \| Minimum [Member]
Compensation And Retirement Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent				7.50%
United Kingdom [Member] \| Maximum [Member]
Compensation And Retirement Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent				10.00%
United Kingdom [Member] \| Scenario, Forecast [Member] \| Minimum [Member]
Compensation And Retirement Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent	8.00%	5.00%
United Kingdom [Member] \| Scenario, Forecast [Member] \| Maximum [Member]
Compensation And Retirement Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent	9.00%	6.00%

Subsequent Events - Additional Information (Detail)	Jul. 31, 2019	Jan. 30, 2019 USD ($)	Jan. 29, 2019 USD ($) shares	Jan. 29, 2019 GBP (£) shares	Feb. 27, 2018 USD ($) shares	Dec. 31, 2018 shares	Dec. 31, 2017 shares
Subsequent Event [Line Items]
Common stock, shares issued \| shares						27,386,632	8,826,190
Private Placement [Member]
Subsequent Event [Line Items]
Common stock, shares issued \| shares					5,797,102
Proceeds from issuance of private placement \| $					$ 80,000,000
Offering costs \| $					$ 2,600,000
JJDC [Member] \| Private Placement [Member]
Subsequent Event [Line Items]
Common stock, shares issued \| shares					2,898,550
Subsequent Event [Member] \| Private Placement [Member]
Subsequent Event [Line Items]
Registration Payment Arrangement Liquidated Damages Percent	1.00%
Subsequent Event [Member] \| License Agreement [Member]
Subsequent Event [Line Items]
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, Plc (“UCLB”); (ii) the License Agreement, dated July 28, 2017, as amended, between the Company and UCLB; and (iii) the License Agreement, dated March 15, 2018, between the Company and UCLB 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, Plc (“UCLB”); (ii) the License Agreement, dated July 28, 2017, as amended, between the Company and UCLB; and (iii) the License Agreement, dated March 15, 2018, between the Company and UCLB to establish new stand-alone license agreements for the following inherited retinal disease programs: (a) achromatopsia (“ACHM”) caused by mutations in CNGB3; (b) ACHM caused by mutations in CNGA3; (c) X-linked retinitis pigmentosa (“XLRP”); and (d) RPE65-mediated IRD.
License arrangement upfront payment			$ 1,976,000	£ 1,500,000
Common stock, shares issued \| shares			1,500,000	1,500,000
Subsequent Event [Member] \| Collaboration Agreement [Member] \| Janssen Pharmaceuticals Inc [Member]
Subsequent Event [Line Items]
Upfront payment \| $		$ 100,000,000
Commercial milestone payments \| $		$ 340,000,000
Subsequent Event [Member] \| Clinical Collaborative Arrangement [Member] \| Janssen Pharmaceuticals Inc [Member]
Subsequent Event [Line Items]
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%

Summary of Significant Accounting Policies - Summary of Non-Current Assets by Geographical Area (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Operation By Geographical [Line Items]
Non current assets	$ 22,242,698	$ 14,379,105
United States
Operation By Geographical [Line Items]
Non current assets	454,568	436,463
United Kingdom
Operation By Geographical [Line Items]
Non current assets	$ 21,788,130	$ 13,942,642

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Parenthetical) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Foreign currency translation, tax	$ 474,391	$ 0