Rocket Pharmaceuticals (RCKT) 10-Q 8 May 20 2020 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	May 04, 2020
Cover [Abstract]
Entity Registrant Name	ROCKET PHARMACEUTICALS, INC.
Entity Central Index Key	0001281895
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		55,157,035
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Entity Address, State or Province	NY

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 190,520	$ 185,383
Investments	85,375	118,732
Prepaid expenses and other assets	3,910	3,639
Total current assets	279,805	307,754
Property and equipment, net	11,140	29,521
Goodwill	30,815	30,815
Restricted cash	1,525	1,525
Deposits	455	455
Operating right-of-use assets	1,470	2,051
Finance lease right-of-use asset	47,541	0
Total assets	372,751	372,121
Current liabilities:
Accounts payable and accrued expenses	18,819	17,352
Operating lease liabilities, current	817	957
Finance lease liabilities, current	1,478	0
Total current liabilities	21,114	18,309
Convertible notes, net of unamortized discount	45,794	45,049
Operating lease liabilities, non-current	917	1,443
Finance lease liabilities, non-current	18,852	0
Other liabilities	23	23
Total liabilities	86,700	64,824
Commitments and contingencies (Note 11)
Stockholders' equity:
Common stock, $0.01 par value, 120,000,000 shares authorized; 55,157,035 and 54,773,061 shares issued and 55,126,474 and 54,769,030 shares outstanding at March 31, 2020 and December 31, 2019, respectively	551	548
Treasury stock, at cost, 30,561 and 4,031 common shares at March 31, 2020 and December 31, 2019, respectively	(429)	(53)
Additional paid-in capital	493,811	489,925
Accumulated other comprehensive loss (income)	(75)	20
Accumulated deficit	(207,807)	(183,143)
Total stockholders' equity	286,051	307,297
Total liabilities and stockholders' equity	372,751	372,121
Series A Convertible Preferred Shares [Member]
Stockholders' equity:
Preferred stock	0	0
Series B Convertible Preferred Shares [Member]
Stockholders' equity:
Preferred stock	$ 0	$ 0

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Stockholders' equity:
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	120,000,000	120,000,000
Common stock, shares issued (in shares)	55,157,035	54,773,061
Common stock, shares outstanding (in shares)	55,126,474	54,769,030
Treasury stock, at cost (in shares)	30,561	4,031
Series A Convertible Preferred Shares [Member]
Stockholders' equity:
Preferred stock, shares authorized (in shares)	300,000	300,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Series B Convertible Preferred Shares [Member]
Stockholders' equity:
Preferred stock, shares authorized (in shares)	300,000	300,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0

Consolidated Statements of Oper

Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Consolidated Statements of Operations (Unaudited) [Abstract]
Revenue	$ 0	$ 0
Operating expenses:
Research and development	16,957	15,137
General and administrative	7,163	3,808
Total operating expenses	24,120	18,945
Loss from operations	(24,120)	(18,945)
Research and development incentives	0	250
Interest expense	(1,573)	(1,604)
Interest and other income net	967	601
Accretion of discount on investments	62	247
Net loss	$ (24,664)	$ (19,451)
Net loss per share attributable to common stockholders - basic and diluted (in dollars per share)	$ (0.45)	$ (0.43)
Weighted-average common shares outstanding - basic and diluted (in shares)	54,883,120	45,122,815

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Consolidated Statements of Comprehensive Loss (Unaudited) [Abstract]
Net loss	$ (24,664)	$ (19,451)
Other comprehensive loss
Net unrealized gain (loss) on investments	(95)	38
Total comprehensive loss	$ (24,759)	$ (19,413)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Treasury Stock [Member]	Additional Paid in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Total
Beginning Balance at Dec. 31, 2018	$ 452	$ (668)	$ 300,253	$ (127)	$ (105,873)	$ 194,037
Beginning Balance (in shares) at Dec. 31, 2018	45,194,736
Issuance of common stock pursuant to exercise of stock options	$ 0	0	0	0	0	0
Issuance of common stock pursuant to exercise of stock options (in shares)	19,701
Stock repurchase	$ 0	(725)	(2)	0	0	(727)
Stock repurchase (in shares)	0
Retirement of treasury stock	$ (1)	1,393	(1,392)	0	0	0
Retirement of treasury stock (in shares)	(100,000)
Unrealized comprehensive gain (loss) on marketable securities	$ 0	0	0	38	0	38
Stock-based compensation	0	0	3,180	0	0	3,180
Net loss	0	0	0	0	(19,451)	(19,451)
Ending Balance at Mar. 31, 2019	$ 451	0	302,039	(89)	(125,324)	177,077
Ending Balance (in shares) at Mar. 31, 2019	45,114,437
Beginning Balance at Dec. 31, 2019	$ 548	(53)	489,925	20	(183,143)	307,297
Beginning Balance (in shares) at Dec. 31, 2019	54,773,061
Issuance of common stock pursuant to exercise of stock options	$ 3	0	(3)	0	0	0
Issuance of common stock pursuant to exercise of stock options (in shares)	386,974
Common stock repurchase	$ 0		(72)	0	0	(72)
Common stock repurchase (in shares)	(3,000)
Sale of treasury stock	$ 0	53	0	0	0	53
Sale of treasury stock (in shares)	0
Issuance of treasury stock pursuant to exercise of stock options	$ 0	(429)	0	0	0	(429)
Issuance of treasury stock pursuant to exercise of stock options (in shares)	0
Unrealized comprehensive gain (loss) on marketable securities	$ 0	0	0	(95)	0	(95)
Stock-based compensation	0	0	3,961	0	0	3,961
Net loss	0	0	0	0	(24,664)	(24,664)
Ending Balance at Mar. 31, 2020	$ 551	$ (429)	$ 493,811	$ (75)	$ (207,807)	$ 286,051
Ending Balance (in shares) at Mar. 31, 2020	55,157,035

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating Activities:
Net loss	$ (24,664)	$ (19,451)
Adjustments to reconcile net loss to net cash used in operating activities:
Accretion of discount on convertible notes	844	850
Increase in lease liability	0	190
Depreciation expense	118	102
Write down of property and equipment	63	0
Stock-based compensation	3,961	3,180
Accretion of discount on investments	(63)	(247)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(271)	(307)
Accounts payable and accrued expenses	(1,932)	(84)
Operating lease liabilities	(452)	(210)
Finance lease liability	151	0
Net cash used in operating activities	(22,245)	(15,977)
Investing activities:
Purchases of investments	(23,481)	0
Proceeds from maturities of investments	56,805	29,935
Payments made to acquire right of use asset	(530)	0
Purchases of property and equipment	(5,207)	(760)
Purchases of internal use software	(88)	0
Net cash provided by investing activities	27,499	29,175
Financing activities:
Proceeds from sale of treasury stock	53	0
Common stock repurchase	(72)	0
Convertible notes refinancing costs to the lender	(98)	0
Net cash used in financing activities	(117)	0
Net change in cash, cash equivalents and restricted cash	5,137	13,198
Cash, cash equivalents and restricted cash at beginning of period	186,908	112,791
Cash, cash equivalents and restricted cash at end of period	192,045	125,989
Supplemental disclosure of non-cash financing and investing activities:
Accrued purchases of property and equipment	2,796	4,392
Accrued purchases of internal use software	174	0
Retirement of treasury stock	72	1,395
Witholding tax payable on shares witheld in treasury stock	429	0
Unrealized (loss) gain on investments	(95)	38
Finance lease right of use asset and lease liability	20,179	0
Reclassification of construction in process of finance right of use asset	26,465	0
Supplemental cash flow information:
Cash paid for interest	$ 1,495	$ 1,495

Nature of Business

Nature of Business	3 Months Ended
	Mar. 31, 2020
Nature of Business [Abstract]
Nature of Business	1. Nature of Business Rocket Pharmaceuticals, Inc., together with its subsidiaries (collectively “Rocket”, the “Company” or “we”) is a clinical-stage, multi-platform biotechnology company focused on the development of first, only and best-in-class gene therapies, with direct on-target mechanism of action and clear clinical endpoints, for rare and devastating diseases. The Company has three clinical-stage ex vivo ” in vivo

Risks and Liquidity

Risks and Liquidity	3 Months Ended
	Mar. 31, 2020
Risks and Liquidity [Abstract]
Risks and Liquidity	2. Risks and Liquidity The Company has not generated any revenue and has incurred losses since inception. The Company’s operations are subject to certain risks and uncertainties, including, among others, uncertainty of drug candidate development, technological uncertainty, uncertainty regarding patents and proprietary rights, lack of commercial manufacturing experience, a lack of marketing or sales capability or experience, dependency on key personnel, compliance with government regulations and the need to obtain additional financing. In addition, there are possible additional delays that could result from the COVID-19 situation. Drug candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure and extensive compliance-reporting capabilities. The Company’s product candidates are in the development and clinical stages. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, that any products developed will obtain necessary government approval or that any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. The Company’s consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities in the ordinary course of business. The Company has experienced negative cash flows from operations and had an accumulated deficit of $207.8 million as of March 31, 2020. As of March 31, 2020, the Company had $275.9 million of cash, cash equivalents and investments. Rocket expects such resources will be sufficient to fund its operating expenses and capital expenditure requirements into 2022. In the longer term, the future viability of the Company is dependent on its ability to generate cash from operating activities or to raise additional capital to finance its operations. The Company’s failure to raise capital as and when needed could have a negative impact on its financial condition and ability to pursue its business strategies.

Basis of Presentation, Principl

Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2020
Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies [Abstract]
Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies	3. Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited interim consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements for the year ended December 31, 2019 included in the Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 6, 2020 (“2019 Form 10-K”). The unaudited interim consolidated financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of March 31, 2020 and the results of its operations and its cash flows for the three months ended March 31, 2020 and 2019. The financial data and other information disclosed in these consolidated notes related to the three months ended March 31, 2020 and 2019 are unaudited. The results for the three months ended March 31, 2020 are not necessarily indicative of results to be expected for the year ending December 31, 2020 and any other interim periods or any future year or period. Principles of Consolidation The consolidated financial statements represent the consolidation of the accounts of the Company and its subsidiaries in conformity with accounting principles generally accepted in the United States (“US GAAP”). All intercompany accounts have been eliminated in consolidation. Use of Estimates The preparation of the consolidated financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these consolidated financial statements include but are not limited to goodwill impairment, the accrual of research and development (“R&D”) expenses, the valuation of equity transactions and stock-based awards. Changes in estimates and assumptions are reflected in reported results in the period in which they become known. Actual results could differ from those estimates. Significant Accounting Policies The significant accounting policies used in the preparation of these consolidated financial statements for the three months ended March 31, 2020 are consistent with those disclosed in Note 3 to the consolidated financial statements in the 2019 Form 10-K, except as noted below. Cash, Cash Equivalents and Restricted Cash Cash, cash equivalents and restricted cash consists of bank deposits, certificates of deposit and money market accounts with financial institutions. Cash equivalents are carried at cost which approximates fair value due to their short-term nature and which the Company believes do not have a material exposure to credit risk. The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents. The Company’s cash and cash equivalent accounts, at times, may exceed federally insured limits. The Company has not experienced any losses in such accounts. Restricted cash consists of deposits collateralizing letters of credit issued by a bank in connection with the Company’s finance and operating leases (see Note 11 “Commitments and Contingencies” for additional disclosures) and a deposit collateralizing a letter of credit issued by a bank supporting the Company’s Corporate Credit Card. Cash, cash equivalents and restricted cash consist of the following: March 31, 2020 December 31, 2019 Cash and cash equivalents $ 190,520 $ 185,383 Restricted cash 1,525 1,525 $ 192,045 $ 186,908 Recent Accounting Pronouncements In August 2018, the FASB issued ASU 2018-13 (“ASU 2018-13”), Fair Value Measurement - Disclosure Framework (Topic 820). The updated guidance improves the disclosure requirements on fair value measurements. The updated guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted for any removed or modified disclosures. The Company adopted this guidance on January 1, 2020. The adoption of ASU 2018-13 had no impact on the Company as the Company does not have Level 3 investments. There were no other recent accounting standards that impacted the Company for the three months ended March 31, 2020.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2020
Fair Value of Financial Instruments [Abstract]
Fair Value of Financial Instruments	4. Fair Value of Financial Instruments Items measured at fair value on a recurring basis are the Company’s investments. The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy: Fair Value Measurements as of March 31, 2020 Using: Level 1 Level 2 Level 3 Total Assets: Money market mutual funds (included in cash and cash equivalents) $ 106,221 $ - $ - $ 106,221 Cash 7,552 - - 7,552 113,773 - - 113,773 United States Treasury securities 43,135 - - 43,135 Corporate Bonds - 36,240 - 36,240 Municipal Bonds - 6,000 - 6,000 Investments 43,135 42,240 - 85,375 $ 156,908 $ 42,240 $ - $ 199,148 Fair Value Measurements as of December 31, 2019 Using: Level 1 Level 2 Level 3 Total Assets: Money market mutual funds (included in cash and cash equivalents) $ 72,114 $ - $ - $ 72,114 Cash 7,542 - - 7,542 79,656 - - 79,656 United States Treasury securities 75,464 - - 75,464 Government Bonds - 8,000 - 8,000 Corporate Bonds - 29,268 - 29,268 Municipal Bonds - 6,000 - 6,000 Investments 75,464 43,268 - 118,732 $ 155,120 $ 43,268 $ - $ 198,388 The Company classifies its money market mutual funds and U.S. Treasury securities as Level 1 assets under the fair value hierarchy, as these assets have been valued using quoted market prices in active markets without any valuation adjustment. The Company classifies its Government, Corporate and Municipal Bonds as Level 2 assets as these assets are not traded in an active market and have been valued through a third-party pricing service based on quoted prices for similar assets. The fair value of the 2021 Convertible Notes as of March 31, 2020 was $11.4 million. The fair value of the 2022 Convertible Notes as of March 31, 2020 was $33.9 million (see Note 7).

Property and Equipment

Property and Equipment	3 Months Ended
	Mar. 31, 2020
Property and Equipment [Abstract]
Property and Equipment	5. Property and Equipment The Company’s property and equipment consisted of the following: March 31, 2020 December 31, 2019 Laboratory equipment $ 9,724 $ 1,910 Computer equipment 179 179 Furniture and fixtures 1,743 273 Leasehold improvements 29 29 Internal use software 488 226 Construction costs in progress - 27,809 12,163 30,426 Less: accumulated depreciation (1,023 ) (905 ) $ 11,140 $ 29,521 Construction costs in progress as of December 31, 2019 comprised costs associated with the build out of the Company’s research, manufacturing and office facilities in Cranbury, NJ. See Note 11 “Commitments and Contingencies” for the treatment of construction costs as part of the right of use asset as of March 31, 2020. During the three months ended March 31, 2020 and 2019, the Company recognized $0.1 million of depreciation expense.

Accounts Payable and Accrued Ex

Accounts Payable and Accrued Expenses	3 Months Ended
	Mar. 31, 2020
Accounts Payable and Accrued Expenses [Abstract]
Accounts Payable and Accrued Expenses	6. Accounts Payable and Accrued Expenses At March 31, 2020 and December 31, 2019, the Company’s accounts payable and accrued expenses consisted of the following: March 31, 2020 December 31, 2019 Research and development $ 12,142 $ 7,418 Property and equipment 2,796 4,424 Bonus 790 2,459 Accrued interest 500 1,241 Government grant payable 569 562 Professional fees 531 553 Accrued vacation 275 129 Internal use software 174 226 Debt exchange fees 283 - Other 759 340 $ 18,819 $ 17,352

Convertible Notes

Convertible Notes	3 Months Ended
	Mar. 31, 2020
Convertible Notes [Abstract]
Convertible Notes	7. Convertible Notes On January 4, 2018, in connection with its reverse merger with Inotek Pharmaceuticals, Corporation (“Inotek”), the Company assumed the obligations of Inotek under its outstanding convertible notes, with an aggregate principal value of $52.0 million, (the “2021 Convertible Notes”). The 2021 Convertible Notes were issued in 2016 and mature on August 1, 2021 (the “Maturity Date”). The 2021 Convertible Notes are unsecured, and accrue interest at a rate of 5.75% per annum and interest is payable semi-annually on February 1 and August 1 of each year. Each holder of the 2021 Convertible Notes (“Holder”) has the option until the close of business on the second business day immediately preceding the Maturity Date to convert all, or any portion, of the 2021 Convertible Notes held by it at a conversion rate of 31.1876 shares of the Company’s common stock per $1.00 principal amount of 2021 Convertible Notes (the “Conversion Rate”) which is $32.08 per share. The Conversion Rate is subject to adjustment from time to time upon the occurrence of certain events, including the issuance of stock dividends and payment of cash dividends. The Company, at its option, may redeem for cash all or any portion of the 2021 Convertible Notes if the last reported sale price of a share of the Company’s common stock is equal to or greater than 200% of the Conversion Rate for the 2021 Convertible Notes then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period (including the last trading day of such period) ending within the five trading days immediately preceding the date on which the Company provides notice of redemption, at a redemption price equal to 100% of the principal amount of the 2021 Convertible Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. The 2021 Convertible Notes are considered a hybrid financial instrument consisting of a fixed interest rate “host” and various embedded features that required evaluation as potential embedded derivatives under FASB ASC 815, Derivatives and Hedging Convertible Notes Exchange Agreement On February 20, 2020, the Company entered into separate, privately negotiated exchange agreements (the “Exchange Agreements”) with certain holders of the 2021 Convertible Notes. Pursuant to the Exchange Agreements, the Company exchanged approximately $39.35 million aggregate principal amount of the 2021 Convertible Notes (which represents approximately 76% of the aggregate outstanding principal amount of the 2021 Convertible Notes) for (a) approximately $39.35 million aggregate principal amount of 6.25% Convertible Senior Notes due August 2022 (the “2022 Convertible Notes”) (an exchange ratio equal to 1.00 2022 Convertible Note per exchanged 2021 Convertible Note) and (b) $119,416 in cash to pay the accrued and unpaid interest on the exchanged 2021 Convertible Notes from February 1, 2020, to February 20, 2020, the closing date of the exchange transactions. The 2022 Convertible Notes were issued in private placements. Upon completion of the exchange transactions, approximately $12.65 million aggregate principal amount of the 2021 Convertible Notes remained outstanding. The conversion rate for the 2022 Convertible Notes is initially 31.1876 shares of the Company’s common stock per $1,000 principal amount of 2022 Convertible Notes, which is equivalent to an initial conversion price of approximately $32.06 per share of common stock, and is subject to adjustment under the terms of the 2022 Convertible Notes. The Company may redeem for cash all or any portion of the 2022 Convertible Notes, at its option, if the last reported sale price of its common stock is equal to or greater than 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period (including the last trading day of such period) ending within the five trading days immediately preceding the date on which the Company provides written notice of redemption. The 2022 Convertible Notes Indenture contains customary terms and covenants and events of default. As of March 31, 2020, the stated interest rate was 6.25%, and the effective interest rate was 15.3%. Additionally, the Company repurchased 3,000 shares of its common stock that have been retired at an aggregate amount of $71,670 from certain shareholders of the 2021 Convertible Notes participating in the exchange transactions in privately negotiated, private transactions. The exchange transactions were accounted for as a modification of the 2021 Convertibles Notes and have been accounted for based on ASC 470-50 Modifications and Extinguishments. The table below summarizes the carrying value of the 2021 Convertible Notes as of March 31, 2020: Principal amount $ 12,650 Discount (1,451 ) Carrying value as of March 31, 2020 $ 11,199 Accretion of the 2021 Convertible Notes discount was $0.6 million and $0.9 million for the three months ended March 31, 2020 and 2019, respectively. The table below summarizes the carrying value of the 2022 Convertible Notes as of March 31, 2020: Principal amount $ 39,350 Discount (4,755 ) Carrying value as of March 31, 2020 $ 34,595 Accretion of the 2022 Convertible Notes discount was $0.2 million for the three months ended March 31, 2020.

Stock Based Compensation

Stock Based Compensation	3 Months Ended
	Mar. 31, 2020
Stock Based Compensation [Abstract]
Stock Based Compensation	8. Stock Based Compensation Stock Option Valuation The weighted average assumptions that the Company used in the Black-Scholes pricing model to determine the fair value of the stock options granted to employees, non-employees and directors were as follows: Three Months Ended March 31, 2020 2019 Risk-free interest rate 1.48 % 2.61 % Expected term (in years) 5.87 5.77 Expected volatility 77.75 % 74.60 % Expected dividend yield 0.00 % 0.00 % Exercise price $ 22.47 $ 14.61 Fair value of common stock $ 22.47 $ 14.61 The Company recognizes compensation expense for only the portion of awards that are expected to vest. The following table summarizes stock option activity for the three months ended March 31, 2020 under the Second Amended and Restated 2014 Stock Option and Incentive Plan: Number of Shares Weighted Average Exercise Price Weighted Average Contractual Term (Years) Aggregate Intrinsic Value Outstanding as of December 31, 2019 9,763,541 $ 5.96 6.96 $ 164,021 Granted 1,188,306 22.47 9.86 Exercised (384,453 ) 1.30 6,766 Forfeited (28,504 ) 17.39 Outstanding as of March 31, 2020 10,538,890 $ 7.96 7.09 $ 80,643 Options vested and exercisable as of March 31, 2020 7,572,141 $ 4.09 6.27 $ 78,872 Options unvested as of March 31, 2020 2,966,749 $ 17.85 9.18 The weighted average grant-date fair value per share of stock options granted during the three months ended March 31, 2020 and 2019 was $15.03 and $9.60, respectively. The total fair value of options vested during the three months ended March 31, 2020 and 2019 was $17.3 million and $20.5 million, respectively. Stock-Based Compensation Three Months Ended March 31, 2020 2019 Research and development $ 1,735 $ 1,565 General and administrative 2,226 1,615 Total share based compensation expense $ 3,961 $ 3,180 As of March 31, 2020, the Company had an aggregate of $33.0 million of unrecognized stock-based compensation expense, which is expected to be recognized over the weighted average period of 2.15 years.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2020
Stockholders' Equity [Abstract]
Stockholders' Equity	9. Stockholders’ Equity The Company has 14,102 warrants outstanding as of March 31, 2020, convertible into 14,102 shares of common stock at an exercise price of $24.82 per share, and expiring on June 28, 2023. On December 12, 2019, the Company recorded treasury stock of $0.1 million for shares withheld to pay the payroll tax liability of an option exercise which was remitted in in January 2020. As of March 31, 2020, the Company recorded treasury stock of $0.4 million for the shares withheld to pay the payroll tax liability of an option exercise.

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2020
Net Loss Per Share [Abstract]
Net Loss Per Share	10. Net Loss Per Share Basic and diluted net loss per share attributable to common stockholders was calculated as follows: Three Months Ended March 31, 2020 2019 Numerator: Net loss attributable to common stockholders $ (24,664 ) $ (19,451 ) Denominator: Weighted-average common shares outstanding - basic and diluted 54,883,120 45,122,815 Net loss per share attributable to common stockholders - basic and diluted $ (0.45 ) $ (0.43 ) The Company excluded the following potential shares of common stock, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect: Three Months Ended March 31, 2020 2019 Shares issuable upon conversion of the 2021 Convertible Notes 394,327 1,620,848 Shares issuable upon conversion of the 2022 Convertible Notes 1,226,621 - Warrants exercisable for common shares 14,102 14,102 Options to purchase common shares 10,538,890 9,392,821 12,173,940 11,027,771

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies The Company determines if an arrangement is a lease at inception. Operating leases are included in the Company’s consolidated balance sheet as right-of-use assets from operating leases, current operating lease liabilities and long-term operating lease liabilities. Finance leases are included in the consolidated balance sheet as right-of-use assets from finance leases, and finance lease liabilities, non-current. Certain of the Company’s lease agreements contain renewal options; however, the Company does not recognize right-of-use assets or lease liabilities for renewal periods unless it is determined that the Company is reasonably certain of renewing the lease at inception or when a triggering event occurs. As the Company’s leases do not provide an implicit rate, the Company estimated the incremental borrowing rate in calculating the present value of the lease payments using an estimate of the Company’s collateralized borrowing rate for debt with a similar term. The Company has utilized its incremental borrowing rate based on the long-term borrowing costs of comparable companies in the biotechnology industry. Since the Company elected to account for each lease component and its associated non-lease components as a single combined lease component, all contract consideration was allocated to the combined lease component. Some of the Company’s lease agreements contain rent escalation clauses (including index-based escalations). The Company recognizes the minimum rental expense on a straight-line basis based on the fixed components of a lease arrangement. The Company will amortize this expense over the term of the lease beginning with the lease commencement date. Variable lease components represent amounts that are not fixed in nature and are not tied to an index or rate, and are recognized as incurred. Finance Lease The Company has a lease for a facility in Cranbury, New Jersey, consisting of 103,720 square feet of space including areas for offices, process development, research and development laboratories and 50,000 square feet will be dedicated to AAV Current Good Manufacturing Practice (cGMP) manufacturing to support the Company’s pipeline. A smaller area within this facility was originally leased in August 2018, and the lease was amended in June 2019 to include the full building (such lease, as amended, the “NJ Lease Agreement”). The NJ Lease Agreement has a term of 15 years from September 1, 2019, with an option to renew for two consecutive five-year renewal terms. Estimated rent payments for the NJ Lease Agreement are $1.2 million per annum, payable in monthly installments, depending upon the nature of the leased space, and subject to annual base rent increases of 3%. The total commitment under the NJ Lease Agreement is estimated to be approximately $29.3 million over the 15-year term of the NJ Lease Agreement. The Company paid a cash security deposit of $0.3 million to the landlord in connection with the NJ Lease Agreement which has been reflected in deposits in the consolidated balance sheets as of March 31, 2020 and December 31, 2019. The Company entered into the lease prior to the building being available for use as the building construction was not complete. The lease payment date started on September 1, 2019. At that time and as of December 31, 2019, the Company determined the lease commencement date had not occurred since the landlord improvements had not been completed. The lease payments were recorded as prepaid rent. The Company determined the lease commencement was reached on March 15, 2020 when the construction of all landlord owned improvements had been substantially completed and when the Company began including its leasehold improvements and move equipment into the space. Upon commencement of the NJ Lease Agreement, the Company recognized total right-of-use assets of $47.7 million, with a corresponding lease liability of $20.2 million. The Company reclassified $26.5 million of construction costs in progress and $1.1 million of prepaid rent as part of the right of use asset upon the lease commencement date. The total restricted cash balance for the Company’s operating leases at March 31, 2020 and December 31, 2019 was $1.0 million and $1.0 million, respectively. Operating Leases On March 31, 2016, the Company entered into a lease agreement for its office and laboratory space at the Alexandria Center for Life Sciences in New York, New York with an initial term ending on July 31, 2022 (the “NY Lease Agreement”). In connection with the NY Lease Agreement, the Company established an irrevocable standby letter of credit (“ARE LOC”) with a bank. The ARE LOC, in which the landlord is the beneficiary, serves as the Company’s security deposit on the lease. The Company has a certificate of deposit with a bank as collateral for the ARE LOC which is classified as restricted cash in the consolidated balance sheets. On June 28, 2018, the Company entered into Amendment No.1 to the NY Lease Agreement, whereby the landlord agreed to relieve the Company of its obligations under the lease for a portion of the leased space upon the takeover of the space by a replacement tenant. The Company agreed to extend the lease for the remaining laboratory space by one additional year until July 2022. In October 2018, the Company provided a new letter of credit for $0.08 million (the “New ARE LOC”) relating to the remaining lab space and the existing ARE LOC of $0.2 million was released back to the Company. The New ARE LOC expires and is automatically renewed April 8 of each succeeding calendar year until October 29, 2020, unless written notice is provided no later than 90 days before the then existing expiration date. On March 12, 2020, the Company entered into Amendment No. 2 to the NY Lease Agreement, which terminates the lease effective as of April 30, 2020 (“ARE Lease Termination). In conjunction with the Amendment No. 2 to the NY Lease Agreement, the Company paid a termination payment of $75,771. On April 22, 2020, the Company entered into Amendment No. 3 to the NY Lease Agreement that extended the termination date to May 31, 2020. In conjunction with the ARE Lease Termination, the Company reduced the ROU Asset by $0.5 million and ROU liability by $0.4 million. On June 7, 2018, the Company entered into a three year lease agreement for office space in the Empire State Building in New York, NY (the “ESB Lease Agreement”). In connection with the ESB Lease Agreement, the Company established an irrevocable standby letter of credit (the “Empire LOC”) with a bank for $0.9 million which expires on June 30, 2020 and is renewed automatically for a one year period until its expiration date of July 31, 2021. The Empire LOC serves as the Company’s security deposit on the lease in which the landlord is the beneficiary. The Company has a certificate of deposit of $0.9 million with a bank as collateral for the Empire LOC which is classified as part of restricted cash in the consolidated balance sheets as of March 31, 2020. On January 4, 2018, in connection with the Reverse Merger, the Company assumed an operating lease for Inotek’s former headquarters in Lexington, Massachusetts, with a term ending in February 2023. In July 2018, the Company signed an agreement to sublease a portion of the Lexington, Massachusetts space and in September 2018, the Company signed an agreement to sublease the remaining portion of the Lexington, Massachusetts space. Rental income received under the sublease agreement totaled $0.1 million and $0.1 million for the three months ended March 31, 2020 and 2019, respectively. Rent expense was $0.3 million and $0.2 million for the three months ended March 31, 2020 and 2019, respectively. Lease cost March 31, 2020 Operating lease cost $ 258 Finance lease cost Amortization of right of use assets 162 Interest on lease liablities 151 Total lease cost $ 571 The following table summarizes the maturity of the Company’s operating lease liabilities on an undiscounted cash flow basis and a reconciliation to the operating and finance lease liabilities as of March 31, 2020: Maturity of operating lease liabilities March 31, 2020 2020 $ 690 2021 682 2022 445 2023 75 Total lease payments $ 1,892 Less: interest (158 ) Total operating lease liabilities $ 1,734 Maturity of finance lease liability March 31, 2020 2020 $ 1,070 2021 1,644 2022 1,689 2023 1,736 2024 1,791 Thereafter 48,767 Total lease payments $ 56,697 Less: interest (36,367 ) Total finance lease liability $ 20,330 Leases March 31, 2020 Operating right-of-use assets $ 1,470 Operating current lease liabilities 817 Operating noncurrent lease liabilities 917 Total operating lease liabilities $ 1,734 Finance right-of-use assets $ 47,541 Finance current lease liability 1,478 Finance noncurrent lease liability 18,852 Total finance lease liability $ 20,330 Other information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 340 Cash flows from finance lease - Weighted-average remaining lease term - operating leases 2.4 years Weighted-average remaining lease term - finance lease 24 years Weighted-average discount rate - operating leases 7.77 % Weighted-average discount rate - finance lease 8.96 % Litigation From time to time, the Company may be subject to other various legal proceedings and claims that arise in the ordinary course of its business activities. Although the results of litigation and claims cannot be predicted with certainty, the Company does not believe it is party to any other claim or litigation the outcome of which, if determined adversely to the Company, would individually or in the aggregate be reasonably expected to have a material adverse effect on its business. Regardless of the outcome, litigation can have an adverse impact on the Company because of defense and settlement costs, diversion of management resources and other factors. Indemnification Arrangements Pursuant to its bylaws and as permitted under Delaware law, the Company has indemnification obligations to directors, officers, employees or agents of the Company or anyone serving in these capacities. The maximum potential amount of future payments the Company could be required to pay is unlimited. The Company has insurance that reduces its monetary exposure and would enable it to recover a portion of any future amounts paid. As a result, the Company believes that the estimated fair value of these indemnification commitments is minimal. Throughout the normal course of business, the Company has agreements with vendors that provide goods and services required by the Company to run its business. In some instances, vendor agreements include language that requires the Company to indemnify the vendor from certain damages caused by the Company’s use of the vendor’s goods and/or services. The Company has insurance that would allow it to recover a portion of any future amounts that could arise from these indemnifications. As a result, the Company believes that the estimated fair value of these indemnification commitments is minimal.

Agreements Related to Intellect

Agreements Related to Intellectual Property	3 Months Ended
	Mar. 31, 2020
Agreements Related to Intellectual Property [Abstract]
Agreements Related to Intellectual Property	12. Agreements Related to Intellectual Property The Company has various license and research and collaboration arrangements. The transactions principally resulted in the acquisition of rights to intellectual property which is in the preclinical phase and has not been tested for safety or feasibility. In all cases, the Company did not acquire tangible assets, processes, protocols or operating systems. The Company expenses the acquired intellectual property rights as of the acquisition date on the basis that the cost of intangible assets purchased from others for use in research and development activities has no alternative future uses.

Strategic Research Collaboratio

Strategic Research Collaboration	3 Months Ended
	Mar. 31, 2020
Strategic Research Collaboration [Abstract]
Strategic Research Collaboration	13. Strategic Research Collaboration On May 16, 2018, the Company and the Stanford University School of Medicine (“Stanford University”) entered into a strategic collaboration agreement to support the advancement of FA and PKD gene therapy research. Under the terms of the collaboration agreement, Stanford University is the lead clinical trial research center in the U.S. for the FA registrational trial and is the lead U.S. site for PKD clinical trials. The project will also separately evaluate the potential for non-myeloablative, non-genotoxic antibody-based conditioning regimens as a future development possibility that may be applied across bone marrow-derived disorders. In addition, the Company agreed to support expansion of Stanford University’s Laboratory for Cell and Gene Therapy (“LCGM”) in order to further enhance the development of the Company’s internal pipeline. The Company agreed to contribute up to $3.5 million for the LCGM expansion of which 40% or $1.4 million was due upon execution of the collaboration agreement and the remaining $2.1 million balance is due upon the achievement of certain milestones. In January 2019, the Company and Stanford University signed a Clinical Trial Agreement for the treatment of FA and upon signing of the Clinical Trial Agreement, the second milestone of $1.4 million for the LGCM became due and was expensed and paid. During the three months ended March 31, 2020, the last milestone under the Stanford Agreement was met and the Company accrued the final milestone payment of $0.7 million as of March 31, 2020.

CIRM Grant

CIRM Grant	3 Months Ended
	Mar. 31, 2020
CIRM Grant [Abstract]
CIRM Grant	14. CIRM Grant On April 30, 2019, the California Institute for Regenerative Medicine (“CIRM”) awarded the Company up to $6.5 million under a CLIN2 grant award to support the clinical development of gene therapy for LAD-I. Proceeds from the grant will help fund clinical trial costs as well as manufactured drug product for Phase I/II patients enrolled at the U.S. clinical site, University of California, Los Angeles (“UCLA”) Mattel Children’s Hospital, led by principal investigator Donald Kohn, M.D., UCLA Professor of Microbiology, Immunology and Molecular Genetics, Pediatrics (Hematology/Oncology), Molecular and Medical Pharmacology and member of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA. In 2019, we received the first two grants from CIRM of $1.2 million, based on eligible costs incurred under the grant. The CIRM grant reimbursements are accrued as an offset against R&D expenses as reimbursable expenses are incurred. No CIRM grants have been received or costs incurred relating to the next milestone for the three months ended March 31, 2020.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	15. Related Party Transactions During March 2018, the Company entered into a consulting agreement with a member of the Board of Directors for strategic and corporate consulting services to be provided to the Company. This agreement was terminated in 2019. The Company incurred expenses of $0 and $4,000 during the three months ended March 31, 2020 and 2019, respectively relating to services provided under this consulting agreement. T he Company entered into a agreement with a member of the Board of Directors for business development consulting services. Payments for the services under the agreement are $27,500 per quarter, and the Company may terminate the agreement with 14 days’ notice. The Company incurred expenses of $27,500 during the three months ended March 31, 2020 and 2019, relating to services provided under this agreement.

401(k) Savings Plan

401(k) Savings Plan	3 Months Ended
	Mar. 31, 2020
401(k) Savings Plan [Abstract]
401(k) Savings Plan	16. 401(k) Savings Plan The Company has a defined contribution savings plan (the “Plan”) under Section 401(k) of the Internal Revenue Code of 1986. This Plan covers substantially all employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. Company contributions to the Plan may be made at the discretion of the Company’s Board of Directors. The Company has elected to the safe harbor match of 4% of employee contributions to the Plan, subject to certain limitations. The Company’s matching contribution for the three months ended March 31, 2020 and 2019 was $99,563 and $81,624, respectively.

Basis of Presentation, Princi_2

Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited interim consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements for the year ended December 31, 2019 included in the Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 6, 2020 (“2019 Form 10-K”). The unaudited interim consolidated financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of March 31, 2020 and the results of its operations and its cash flows for the three months ended March 31, 2020 and 2019. The financial data and other information disclosed in these consolidated notes related to the three months ended March 31, 2020 and 2019 are unaudited. The results for the three months ended March 31, 2020 are not necessarily indicative of results to be expected for the year ending December 31, 2020 and any other interim periods or any future year or period.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements represent the consolidation of the accounts of the Company and its subsidiaries in conformity with accounting principles generally accepted in the United States (“US GAAP”). All intercompany accounts have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these consolidated financial statements include but are not limited to goodwill impairment, the accrual of research and development (“R&D”) expenses, the valuation of equity transactions and stock-based awards. Changes in estimates and assumptions are reflected in reported results in the period in which they become known. Actual results could differ from those estimates.
Significant Accounting Policies	Significant Accounting Policies The significant accounting policies used in the preparation of these consolidated financial statements for the three months ended March 31, 2020 are consistent with those disclosed in Note 3 to the consolidated financial statements in the 2019 Form 10-K, except as noted below.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash Cash, cash equivalents and restricted cash consists of bank deposits, certificates of deposit and money market accounts with financial institutions. Cash equivalents are carried at cost which approximates fair value due to their short-term nature and which the Company believes do not have a material exposure to credit risk. The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents. The Company’s cash and cash equivalent accounts, at times, may exceed federally insured limits. The Company has not experienced any losses in such accounts. Restricted cash consists of deposits collateralizing letters of credit issued by a bank in connection with the Company’s finance and operating leases (see Note 11 “Commitments and Contingencies” for additional disclosures) and a deposit collateralizing a letter of credit issued by a bank supporting the Company’s Corporate Credit Card. Cash, cash equivalents and restricted cash consist of the following: March 31, 2020 December 31, 2019 Cash and cash equivalents $ 190,520 $ 185,383 Restricted cash 1,525 1,525 $ 192,045 $ 186,908
Recent Accounting Pronouncements	Recent Accounting Pronouncements In August 2018, the FASB issued ASU 2018-13 (“ASU 2018-13”), Fair Value Measurement - Disclosure Framework (Topic 820). The updated guidance improves the disclosure requirements on fair value measurements. The updated guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted for any removed or modified disclosures. The Company adopted this guidance on January 1, 2020. The adoption of ASU 2018-13 had no impact on the Company as the Company does not have Level 3 investments. There were no other recent accounting standards that impacted the Company for the three months ended March 31, 2020.

Basis of Presentation, Princi_3

Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2020
Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies [Abstract]
Cash, Cash Equivalents and Restricted Cash	Restricted cash consists of deposits collateralizing letters of credit issued by a bank in connection with the Company’s finance and operating leases (see Note 11 “Commitments and Contingencies” for additional disclosures) and a deposit collateralizing a letter of credit issued by a bank supporting the Company’s Corporate Credit Card. Cash, cash equivalents and restricted cash consist of the following: March 31, 2020 December 31, 2019 Cash and cash equivalents $ 190,520 $ 185,383 Restricted cash 1,525 1,525 $ 192,045 $ 186,908

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value of Financial Instruments [Abstract]
Fair Value of Financial Instruments Measured on Recurring Basis	Items measured at fair value on a recurring basis are the Company’s investments. The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy: Fair Value Measurements as of March 31, 2020 Using: Level 1 Level 2 Level 3 Total Assets: Money market mutual funds (included in cash and cash equivalents) $ 106,221 $ - $ - $ 106,221 Cash 7,552 - - 7,552 113,773 - - 113,773 United States Treasury securities 43,135 - - 43,135 Corporate Bonds - 36,240 - 36,240 Municipal Bonds - 6,000 - 6,000 Investments 43,135 42,240 - 85,375 $ 156,908 $ 42,240 $ - $ 199,148 Fair Value Measurements as of December 31, 2019 Using: Level 1 Level 2 Level 3 Total Assets: Money market mutual funds (included in cash and cash equivalents) $ 72,114 $ - $ - $ 72,114 Cash 7,542 - - 7,542 79,656 - - 79,656 United States Treasury securities 75,464 - - 75,464 Government Bonds - 8,000 - 8,000 Corporate Bonds - 29,268 - 29,268 Municipal Bonds - 6,000 - 6,000 Investments 75,464 43,268 - 118,732 $ 155,120 $ 43,268 $ - $ 198,388

Property and Equipment (Tables)

Property and Equipment (Tables)	3 Months Ended
	Mar. 31, 2020
Property and Equipment [Abstract]
Property and Equipment	The Company’s property and equipment consisted of the following: March 31, 2020 December 31, 2019 Laboratory equipment $ 9,724 $ 1,910 Computer equipment 179 179 Furniture and fixtures 1,743 273 Leasehold improvements 29 29 Internal use software 488 226 Construction costs in progress - 27,809 12,163 30,426 Less: accumulated depreciation (1,023 ) (905 ) $ 11,140 $ 29,521

Accounts Payable and Accrued _2

Accounts Payable and Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2020
Accounts Payable and Accrued Expenses [Abstract]
Accounts Payable and Accrued Expenses	At March 31, 2020 and December 31, 2019, the Company’s accounts payable and accrued expenses consisted of the following: March 31, 2020 December 31, 2019 Research and development $ 12,142 $ 7,418 Property and equipment 2,796 4,424 Bonus 790 2,459 Accrued interest 500 1,241 Government grant payable 569 562 Professional fees 531 553 Accrued vacation 275 129 Internal use software 174 226 Debt exchange fees 283 - Other 759 340 $ 18,819 $ 17,352

Convertible Notes (Tables)

Convertible Notes (Tables)	3 Months Ended
	Mar. 31, 2020
2021 Convertible Notes [Member]
Debt Instrument [Line Items]
Carrying Value of Convertible Notes	The table below summarizes the carrying value of the 2021 Convertible Notes as of March 31, 2020: Principal amount $ 12,650 Discount (1,451 ) Carrying value as of March 31, 2020 $ 11,199
2022 Convertible Notes [Member]
Debt Instrument [Line Items]
Carrying Value of Convertible Notes	The table below summarizes the carrying value of the 2022 Convertible Notes as of March 31, 2020: Principal amount $ 39,350 Discount (4,755 ) Carrying value as of March 31, 2020 $ 34,595

Stock Based Compensation (Table

Stock Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2020
Stock Based Compensation [Abstract]
Weighted-Average Assumptions for Stock Options	The weighted average assumptions that the Company used in the Black-Scholes pricing model to determine the fair value of the stock options granted to employees, non-employees and directors were as follows: Three Months Ended March 31, 2020 2019 Risk-free interest rate 1.48 % 2.61 % Expected term (in years) 5.87 5.77 Expected volatility 77.75 % 74.60 % Expected dividend yield 0.00 % 0.00 % Exercise price $ 22.47 $ 14.61 Fair value of common stock $ 22.47 $ 14.61
Stock Option Activity	The following table summarizes stock option activity for the three months ended March 31, 2020 under the Second Amended and Restated 2014 Stock Option and Incentive Plan: Number of Shares Weighted Average Exercise Price Weighted Average Contractual Term (Years) Aggregate Intrinsic Value Outstanding as of December 31, 2019 9,763,541 $ 5.96 6.96 $ 164,021 Granted 1,188,306 22.47 9.86 Exercised (384,453 ) 1.30 6,766 Forfeited (28,504 ) 17.39 Outstanding as of March 31, 2020 10,538,890 $ 7.96 7.09 $ 80,643 Options vested and exercisable as of March 31, 2020 7,572,141 $ 4.09 6.27 $ 78,872 Options unvested as of March 31, 2020 2,966,749 $ 17.85 9.18
Stock-Based Compensation Expense	Stock-Based Compensation Three Months Ended March 31, 2020 2019 Research and development $ 1,735 $ 1,565 General and administrative 2,226 1,615 Total share based compensation expense $ 3,961 $ 3,180

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2020
Net Loss Per Share [Abstract]
Basic and Diluted Net Loss Per Share	Basic and diluted net loss per share attributable to common stockholders was calculated as follows: Three Months Ended March 31, 2020 2019 Numerator: Net loss attributable to common stockholders $ (24,664 ) $ (19,451 ) Denominator: Weighted-average common shares outstanding - basic and diluted 54,883,120 45,122,815 Net loss per share attributable to common stockholders - basic and diluted $ (0.45 ) $ (0.43 )
Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share	The Company excluded the following potential shares of common stock, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect: Three Months Ended March 31, 2020 2019 Shares issuable upon conversion of the 2021 Convertible Notes 394,327 1,620,848 Shares issuable upon conversion of the 2022 Convertible Notes 1,226,621 - Warrants exercisable for common shares 14,102 14,102 Options to purchase common shares 10,538,890 9,392,821 12,173,940 11,027,771

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies [Abstract]
Lease Cost	Lease cost March 31, 2020 Operating lease cost $ 258 Finance lease cost Amortization of right of use assets 162 Interest on lease liablities 151 Total lease cost $ 571
Maturities of Operating Lease Liabilities	The following table summarizes the maturity of the Company’s operating lease liabilities on an undiscounted cash flow basis and a reconciliation to the operating and finance lease liabilities as of March 31, 2020: Maturity of operating lease liabilities March 31, 2020 2020 $ 690 2021 682 2022 445 2023 75 Total lease payments $ 1,892 Less: interest (158 ) Total operating lease liabilities $ 1,734
Maturity of Finance Lease Liability	Maturity of finance lease liability March 31, 2020 2020 $ 1,070 2021 1,644 2022 1,689 2023 1,736 2024 1,791 Thereafter 48,767 Total lease payments $ 56,697 Less: interest (36,367 ) Total finance lease liability $ 20,330
Balance Sheet Information Related to Leases	Leases March 31, 2020 Operating right-of-use assets $ 1,470 Operating current lease liabilities 817 Operating noncurrent lease liabilities 917 Total operating lease liabilities $ 1,734 Finance right-of-use assets $ 47,541 Finance current lease liability 1,478 Finance noncurrent lease liability 18,852 Total finance lease liability $ 20,330
Lease Related to Cash Flow Information, Lease Term and Discount Rate	Other information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 340 Cash flows from finance lease - Weighted-average remaining lease term - operating leases 2.4 years Weighted-average remaining lease term - finance lease 24 years Weighted-average discount rate - operating leases 7.77 % Weighted-average discount rate - finance lease 8.96 %

Nature of Business (Details)

Nature of Business (Details)	3 Months Ended
	Mar. 31, 2020Program
Programs in Clinical Testing [Abstract]
Number of clinical-stage programs currently enrolling patients	3

Risks and Liquidity (Details)

Risks and Liquidity (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Risks and Liquidity [Abstract]
Accumulated deficit	$ (207,807)	$ (183,143)
Cash, cash equivalents and investments	$ 275,900

Basis of Presentation, Princi_4

Basis of Presentation, Principles of Consolidation and Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and cash equivalents	$ 190,520	$ 185,383
Restricted cash	1,525	1,525
Total	$ 192,045	$ 186,908	$ 125,989	$ 112,791

Fair Value of Financial Instr_3

Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
2021 Convertible Notes [Member]
Additional Information in Fair Value Disclosure [Abstract]
Fair value convertible note	$ 11,400
2022 Convertible Notes [Member]
Additional Information in Fair Value Disclosure [Abstract]
Fair value convertible note	33,900
Recurring [Member]
Assets [Abstract]
Cash and cash equivalents	113,773	$ 79,656
Recurring [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	199,148	198,388
Recurring [Member] | Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	106,221	72,114
Recurring [Member] | Cash [Member]
Assets [Abstract]
Cash and cash equivalents	7,552	7,542
Recurring [Member] | United States Treasury Securities [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	43,135	75,464
Recurring [Member] | Government Bonds [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments		8,000
Recurring [Member] | Corporate Bonds [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	36,240	29,268
Recurring [Member] | Municipal Bonds [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	6,000	6,000
Recurring [Member] | Investments [Member] | Short-term Investments [Member]
Assets [Abstract]
Investments	85,375	118,732
Recurring [Member] | Level 1 [Member]
Assets [Abstract]
Cash and cash equivalents	113,773	79,656
Recurring [Member] | Level 1 [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	156,908	155,120
Recurring [Member] | Level 1 [Member] | Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	106,221	72,114
Recurring [Member] | Level 1 [Member] | Cash [Member]
Assets [Abstract]
Cash and cash equivalents	7,552	7,542
Recurring [Member] | Level 1 [Member] | United States Treasury Securities [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	43,135	75,464
Recurring [Member] | Level 1 [Member] | Government Bonds [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments		0
Recurring [Member] | Level 1 [Member] | Corporate Bonds [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	0	0
Recurring [Member] | Level 1 [Member] | Municipal Bonds [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	0	0
Recurring [Member] | Level 1 [Member] | Investments [Member] | Short-term Investments [Member]
Assets [Abstract]
Investments	43,135	75,464
Recurring [Member] | Level 2 [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Recurring [Member] | Level 2 [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	42,240	43,268
Recurring [Member] | Level 2 [Member] | Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Recurring [Member] | Level 2 [Member] | Cash [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Recurring [Member] | Level 2 [Member] | United States Treasury Securities [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	0	0
Recurring [Member] | Level 2 [Member] | Government Bonds [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments		8,000
Recurring [Member] | Level 2 [Member] | Corporate Bonds [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	36,240	29,268
Recurring [Member] | Level 2 [Member] | Municipal Bonds [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	6,000	6,000
Recurring [Member] | Level 2 [Member] | Investments [Member] | Short-term Investments [Member]
Assets [Abstract]
Investments	42,240	43,268
Recurring [Member] | Level 3 [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Recurring [Member] | Level 3 [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	0	0
Recurring [Member] | Level 3 [Member] | Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Recurring [Member] | Level 3 [Member] | Cash [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Recurring [Member] | Level 3 [Member] | United States Treasury Securities [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	0	0
Recurring [Member] | Level 3 [Member] | Government Bonds [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments		0
Recurring [Member] | Level 3 [Member] | Corporate Bonds [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	0	0
Recurring [Member] | Level 3 [Member] | Municipal Bonds [Member] | Short-term Investments [Member]
Assets [Abstract]
Fair value of financial instruments	0	0
Recurring [Member] | Level 3 [Member] | Investments [Member] | Short-term Investments [Member]
Assets [Abstract]
Investments	$ 0	$ 0

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Property and Equipment [Abstract]
Property and equipment, Gross	$ 12,163		$ 30,426
Less: accumulated depreciation	(1,023)		(905)
Property and equipment, net	11,140		29,521
Depreciation expense	118	$ 102
Laboratory Equipment [Member]
Property and Equipment [Abstract]
Property and equipment, Gross	9,724		1,910
Computer Equipment [Member]
Property and Equipment [Abstract]
Property and equipment, Gross	179		179
Furniture and Fixtures [Member]
Property and Equipment [Abstract]
Property and equipment, Gross	1,743		273
Leasehold Improvements [Member]
Property and Equipment [Abstract]
Property and equipment, Gross	29		29
Internal use Software [Member]
Property and Equipment [Abstract]
Property and equipment, Gross	488		226
Construction Costs in Progress [Member]
Property and Equipment [Abstract]
Property and equipment, Gross	$ 0		$ 27,809

Accounts Payable and Accrued _3

Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accounts Payable and Accrued Expenses [Abstract]
Research and development	$ 12,142	$ 7,418
Property and equipment	2,796	4,424
Bonus	790	2,459
Accrued interest	500	1,241
Government grant payable	569	562
Professional fees	531	553
Accrued vacation	275	129
Internal use software	174	226
Debt exchange fees	283	0
Other	759	340
Total	$ 18,819	$ 17,352

Convertible Notes (Details)

Convertible Notes (Details)	Feb. 20, 2020USD ($)Note$ / sharesshares	Mar. 31, 2020USD ($)$ / shares	Mar. 31, 2019USD ($)	Dec. 31, 2019USD ($)	Jan. 04, 2018USD ($)
Debt [Abstract]
Aggregate amount of common stock shares repurchased		$ 72,000
Cost associated with exchange transactions		1,600,000
Convertible notes refinancing costs to the lender		98,000	$ 0
Carrying value of convertible notes [Abstract]
Carrying value as of March 31, 2020		45,794,000		$ 45,049,000
Accretion of discount on convertible notes		$ 844,000	850,000
2021 Convertible Notes [Member]
Debt [Abstract]
Debt instrument maturity date		Aug. 1, 2021
Convertible senior notes, interest rate, stated percentage		5.75%
Debt conversion ratio		31.1876
Conversion price (in dollars per share) | $ / shares		$ 32.08
Conversion per principal amount of debt		$ 1
Percentage of common stock conversion price		200.00%
Number of trading days immediately preceding notice of redemption		5 days
Redemption price percentage		100.00%
Effective interest rate		15.30%
Debt instrument, aggregate principal amount exchanged	$ 39,350,000
Debt instrument, percentage of aggregate outstanding principal	76.00%
Accrued and unpaid interest amount to pay in cash	$ 119,416
Number of common stock shares repurchased (in shares) | shares	3,000
Aggregate amount of common stock shares repurchased	$ 71,670,000
Carrying value of convertible notes [Abstract]
Principal amount		$ 12,650,000			$ 52,000,000
Discount		(1,451,000)
Carrying value as of March 31, 2020	$ 12,650,000	11,199,000
Accretion of discount on convertible notes		$ 600,000	$ 900,000
2022 Convertible Notes [Member]
Debt [Abstract]
Convertible senior notes, interest rate, stated percentage	6.25%	6.25%
Debt conversion ratio	31.1876
Conversion price (in dollars per share) | $ / shares	$ 32.06
Conversion per principal amount of debt	$ 1,000
Percentage of common stock conversion price	130.00%
Number of trading days immediately preceding notice of redemption	5 days
Effective interest rate		15.30%
Number of notes issued | Note	1
Carrying value of convertible notes [Abstract]
Principal amount	$ 39,350,000	$ 39,350,000
Discount		(4,755,000)
Carrying value as of March 31, 2020		34,595,000
Accretion of discount on convertible notes		$ 200,000

Stock Based Compensation, Share

Stock Based Compensation, Share Option Valuation (Details) - Stock Options [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Stock Option Activity [Roll Forward]
Outstanding at beginning of period (in shares)	9,763,541
Granted (in shares)	1,188,306
Exercised (in shares)	(384,453)
Forfeited (in shares)	(28,504)
Outstanding at end of period (in shares)	10,538,890		9,763,541
Options vested and exercisable at end of period (in shares)	7,572,141
Options unvested at ending of period (in shares)	2,966,749
Weighted Average Exercise Price [Abstract]
Outstanding at beginning of period (in dollars per share)	$ 5.96
Granted (in dollars per share)	22.47
Exercised (in dollars per share)	1.30
Forfeited (in dollars per share)	17.39
Outstanding at end of period (in dollars per share)	7.96		$ 5.96
Options vested and exercisable at end of period (in dollars per share)	4.09
Options unvested at ending (in dollars per share)	$ 17.85
Weighted-Average Remaining Contractual Term [Abstract]
Outstanding	7 years 1 month 2 days		6 years 11 months 16 days
Granted	9 years 10 months 10 days
Options vested and exercisable	6 years 3 months 7 days
Options unvested	9 years 2 months 5 days
Aggregate Intrinsic Value [Abstract]
Outstanding at beginning of period	$ 164,021
Exercised	6,766
Outstanding at end of period	80,643		$ 164,021
Options vested and exercisable	$ 78,872
Weighted average grant date fair value of shares granted (in dollars per share)	$ 15.03	$ 9.60
Total fair value of options vested	$ 17,300	$ 20,500
Employees and Directors [Member]
Weighted-Average Assumptions [Abstract]
Risk-free interest rate	1.48%	2.61%
Expected term	5 years 10 months 13 days	5 years 9 months 7 days
Expected volatility	77.75%	74.60%
Expected dividend yield	0.00%	0.00%
Exercise price (in dollars per share)	$ 22.47	$ 14.61
Fair value of common stock (in dollars per share)	$ 22.47	$ 14.61

Stock Based Compensation, Sha_2

Stock Based Compensation, Share-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Stock-Based Compensation Expense [Abstract]
Total share based compensation expense	$ 3,961	$ 3,180
Unrecognized share-based compensation cost	$ 33,000
Weighted average period expected to recognize unrecognized share-based compensation cost	2 years 1 month 24 days
Research and Development [Member]
Stock-Based Compensation Expense [Abstract]
Total share based compensation expense	$ 1,735	1,565
General and Administrative [Member]
Stock-Based Compensation Expense [Abstract]
Total share based compensation expense	$ 2,226	$ 1,615

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Dec. 12, 2019
Shareholders' Equity Disclosure [Abstract]
Warrants outstanding (in shares)	14,102
Exercise price of warrants (in dollars per share)	$ 24.82
Warrants expiry date	Jun. 28, 2023
Treasury stock	$ (429)	$ (53)	$ (100)
Warrants Exercisable for Common Shares [Member]
Shareholders' Equity Disclosure [Abstract]
Number of shares issuable on exercise of warrants outstanding (in shares)	14,102

Net Loss Per Share (Details)

Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net loss attributable to common stockholders	$ (24,664)	$ (19,451)
Denominator:
Weighted-average common shares outstanding - basic and diluted (in shares)	54,883,120	45,122,815
Net loss per share attributable to common stockholders - basic and diluted (in dollars per share)	$ (0.45)	$ (0.43)
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Securities excluded from computation of diluted net loss per share (in shares)	12,173,940	11,027,771
Shares Issuable upon Conversion of the 2021 Convertible Notes [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Securities excluded from computation of diluted net loss per share (in shares)	394,327	1,620,848
2022 Convertible Notes [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Securities excluded from computation of diluted net loss per share (in shares)	1,226,621	0
Warrants Exercisable for Common Shares [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Securities excluded from computation of diluted net loss per share (in shares)	14,102	14,102
Options to Purchase Common Shares [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Securities excluded from computation of diluted net loss per share (in shares)	10,538,890	9,392,821

Commitments and Contingencies_2

Commitments and Contingencies (Details)	Apr. 22, 2020USD ($)	Mar. 12, 2020USD ($)	Mar. 31, 2020USD ($)ft²LeaseAgreement	Mar. 31, 2019USD ($)	Mar. 15, 2020USD ($)	Dec. 31, 2019USD ($)	Oct. 31, 2018USD ($)	Jun. 07, 2018USD ($)
Finance Lease [Abstract]
Reclassification of construction costs in progress to right-of-use assets					$ 26,500,000
Reclassification of prepaid rent to right-of-use assets					1,100,000
Restricted cash			$ 1,525,000			$ 1,525,000
Operating Leases [Abstract]
Decrease in operating lease liabilities			(452,000)	$ (210,000)
Rent expense			300,000	200,000
Lease cost [Abstract]
Operating lease cost			258,000
Finance lease cost [Abstract]
Amortization of right of use assets			162,000
Interest on lease liabilities			151,000
Total lease cost			571,000
Maturities of operating lease liabilities [Abstract]
2020			690,000
2021			682,000
2022			445,000
2023			75,000
Total lease payments			1,892,000
Less: interest			(158,000)
Total operating lease liabilities			1,734,000
Maturity of finance lease liabilities
2020			1,070,000
2021			1,644,000
2022			1,689,000
2023			1,736,000
2024			1,791,000
Thereafter			48,767,000
Total lease payments			56,697,000
Less: interest			(36,367,000)
Total finance lease liability			20,330,000		20,200,000
Lease assets and liabilities [Abstract]
Operating right-of-use assets			1,470,000			2,051,000
Operating current lease liabilities			817,000			957,000
Operating noncurrent lease liabilities			917,000			1,443,000
Total operating lease liabilities			1,734,000
Finance right-of-use assets			47,541,000		47,700,000	0
Finance current lease liability			1,478,000			0
Finance noncurrent lease liability			18,852,000			0
Total finance lease liability			20,330,000		$ 20,200,000
Cash paid for amounts included in the measurement of lease liabilities [Abstract]
Operating cash flows from operating leases			340,000
Cash flows from finance lease			$ 0
Weighted-average remaining lease term - operating leases			2 years 4 months 24 days
Weighted-average remaining lease term - finance lease			2 years 4 months 24 days
Weighted-average discount rate - operating leases			7.77%
Weighted-average discount rate - finance lease			8.96%
NJ Lease Agreement [Member]
Finance Lease [Abstract]
Area of lease | ft²			103,720
Term of finance lease agreement			15 years
Number of options to renew lease agreement | LeaseAgreement			2
Term of renewal of finance lease agreement			5 years
Estimated rent payments			$ 1,200,000
Percentage of annual increase in base rent			3.00%
Cash security deposit			$ 300,000			300,000
Maturity of finance lease liabilities
Total lease payments			$ 29,300,000
AAV Current Good Manufacturing Practice (cGMP) [Member]
Finance Lease [Abstract]
Area of lease | ft²			50,000
Property Subject to Operating Lease [Member]
Finance Lease [Abstract]
Restricted cash			$ 1,000,000			$ 1,000,000
NY Lease Agreement [Member]
Operating Leases [Abstract]
Term of lease agreement			1 year
Letter of credit			$ 200,000				$ 80,000
Letter of credit expiration date			Oct. 29, 2020
Number of days written notice			90 days
Termination payment		$ 75,771
Lease expiration date			Feb. 28, 2023
NY Lease Agreement [Member] | Subsequent Event [Member]
Operating Leases [Abstract]
Decrease in ROU Assets	$ (500,000)
Decrease in operating lease liabilities	$ (400,000)
Empire State Building, L.L.C [Member]
Operating Leases [Abstract]
Term of lease agreement			3 years
Letter of credit								$ 900,000
Term of renewal lease agreement			1 year
Letter of credit expiration date			Jun. 30, 2020
Lease expiration date			Jul. 31, 2021
Certificate of deposit								$ 900,000
Lexington Massachusetts Lease [Member]
Operating Leases [Abstract]
Lease expiration date			Feb. 28, 2023
Rental income received under sublease agreement			$ 100,000	$ 100,000

Strategic Research Collaborat_2

Strategic Research Collaboration (Details) - USD ($) $ in Millions	May 16, 2018	Jan. 31, 2019	Mar. 31, 2020
Collaboration Agreement [Abstract]
Funding in strategic research collaboration	$ 3.5
Percentage of funding due upon execution of the agreement	40.00%
Funding in strategic research collaboration	$ 1.4	$ 1.4
Remaining funding due upon the execution of the agreement	$ 2.1
Milestone payment made during period			$ 0.7

CIRM Grant (Details)

CIRM Grant (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Apr. 30, 2019
Additional Information of CIRM Grant [Abstract]
Grant award for clinical development support			$ 6.5
Receivable of offset grants against expenses	$ 0	$ 1.2

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Member of the Board of Directors - One [Member]
Related Party Transaction [Abstract]
Related party expenses	$ 0	$ 4,000
Member of the Board of Directors - Two [Member]
Related Party Transaction [Abstract]
Related party expenses	27,500	$ 27,500
Business development consulting services expense (per quarter)	$ 27,500
Termination notice period for business development consulting services agreement	14 days

401(k) Savings Plan (Details)

401(k) Savings Plan (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
401(k) Savings Plan [Abstract]
Percentage of matching employee contributions	4.00%
Matching employee contributions	$ 99,563	$ 81,624