Rocket Pharmaceuticals (RCKT) 10-K 1 Mar 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Feb. 22, 2021	Jun. 30, 2020
Cover page.
Entity Registrant Name	Rocket Pharmaceuticals, Inc.
Entity Central Index Key	0001281895
Current Fiscal Year End Date	--12-31
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Document Transition Report	false
Entity File Number	001-36829
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3475813
Entity Address, Address Line One	9 Cedarbrook Drive
Entity Address, City or Town	Cranbury
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	08512
City Area Code	646
Local Phone Number	440-9100
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	RCKT
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 734.6
Entity Common Stock, Shares Outstanding		61,778,289

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 297,098	$ 185,383
Investments	185,621	118,732
Prepaid expenses and other assets	4,626	3,639
Total current assets	487,345	307,754
Property and equipment, net	19,206	29,521
Goodwill	30,815	30,815
Restricted cash	1,568	1,525
Deposits	455	455
Operating lease right-of-use assets	914	2,051
Finance lease right-of-use asset	50,521	0
Total assets	590,824	372,121
Current liabilities:
Accounts payable and accrued expenses	25,472	17,352
Convertible notes, net of unamortized discount, current	4,875	0
Operating lease liabilities, current	626	957
Finance lease liabilities, current	1,644	0
Total current liabilities	32,617	18,309
Convertible notes, net of unamortized discount, non-current	35,066	45,049
Operating lease liabilities, non-current	498	1,443
Finance lease liabilities, non-current	18,988	0
Other liabilities	136	23
Total liabilities	87,305	64,824
Commitments and contingencies (Note 12)
Stockholders' equity:
Common stock, $0.01 par value, 120,000,000 shares authorized; 60,996,367 and 54,773,061 shares issued and 60,996,367 and 54,769,030 shares outstanding at December 31, 2020 and December 31, 2019, respectively	610	548
Treasury stock, at cost, 0 and 4,031 common shares at December 31, 2020 and December 31, 2019, respectively	0	(53)
Additional paid-in capital	825,794	489,925
Accumulated other comprehensive income (loss)	(42)	20
Accumulated deficit	(322,843)	(183,143)
Total stockholders' equity	503,519	307,297
Total liabilities and stockholders' equity	590,824	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 (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Shareholders' 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)	60,996,367	54,773,061
Common stock, shares outstanding (in shares)	60,996,367	54,769,030
Treasury stock, at cost (in shares)	0	4,031
Series A Convertible Preferred Shares [Member]
Shareholders' 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]
Shareholders' 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 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Consolidated Statements of Operations [Abstract]
Revenue	$ 0	$ 0	$ 0
Operating expenses:
Research and development	106,382	58,623	53,270
General and administrative	27,921	17,528	17,886
Total operating expenses	134,303	76,151	71,156
Loss from operations	(134,303)	(76,151)	(71,156)
Research and development incentives	0	250	186
Interest expense	(6,967)	(5,958)	(6,039)
Interest and other income net	2,150	3,414	1,690
(Amortization of premium) accretion of discount on investments - net	(580)	1,175	801
Net loss	$ (139,700)	$ (77,270)	$ (74,518)
Net loss per share attributable to common stockholders - basic and diluted (in dollars per share)	$ (2.52)	$ (1.58)	$ (1.89)
Weighted-average common shares outstanding - basic and diluted (in shares)	55,380,740	49,010,358	39,377,666

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Consolidated Statements of Comprehensive Loss [Abstract]
Net loss	$ (139,700)	$ (77,270)	$ (74,518)
Other comprehensive loss
Net unrealized (loss) gain on investments	(62)	147	(127)
Total comprehensive loss	$ (139,762)	$ (77,123)	$ (74,645)

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Preferred Stock [Member]Series A Convertible Preferred Shares [Member]	Preferred Stock [Member]Series B Convertible Preferred Shares [Member]	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, 2017	$ 16,060	$ 25,406	$ 68	$ 0	$ 5,340	$ 0	$ (31,355)	$ 15,519
Beginning Balance (in shares) at Dec. 31, 2017	128,738	126,909	6,795,627
Conversion of convertible securities into common shares	$ (16,060)	$ (25,406)	$ 194	0	41,272	0	0	0
Conversion of convertible securities into common shares (in shares)	(128,738)	(126,909)	19,475,788
Exchange of common shares in connection with the Reverse Merger			$ 68	0	85,992	0	0	86,060
Exchange of common shares in connection with the Reverse Merger (in shares)			6,805,608
Issuance of common stock, net of issuance costs			$ 115	0	153,907	0	0	154,022
Issuance of common stock, net of issuance costs (in shares)			11,475,242
Issuance of common stock pursuant to settlement of restricted stock units			$ 3	0	(3)	0	0	0
Issuance of common stock pursuant to settlement of restricted stock units (in shares)			271,718
Issuance of common stock pursuant to exercise of stock options			$ 4	0	144	0	0	148
Issuance of common stock pursuant to exercise of stock options (in shares)			370,753
Stock repurchase			$ 0	(668)	0	0	0	(668)
Stock repurchase (in shares)			0
Unrealized comprehensive gain (loss) on investments			$ 0	0	0	(127)	0	(127)
Share-based compensation			0	0	13,601	0	0	13,601
Net loss			0	0	0	0	(74,518)	(74,518)
Ending Balance at Dec. 31, 2018	$ 0	$ 0	$ 452	(668)	300,253	(127)	(105,873)	194,037
Ending Balance (in shares) at Dec. 31, 2018	0	0	45,194,736
Issuance of common stock, net of issuance costs			$ 96	0	177,664	0	0	177,760
Issuance of common stock, net of issuance costs (in shares)			9,568,000
Issuance of common stock pursuant to exercise of stock options			$ 1	0	30	0	0	31
Issuance of common stock pursuant to exercise of stock options (in shares)			110,325
Stock repurchase			$ 0	(725)		0	0	(726)
Stock repurchase					(1)
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)
Sale of treasury stock			$ 0	344	0	0	0	344
Sale of treasury stock (in shares)			0
Issuance of treasury stock pursuant to exercise of stock options			$ 0	(397)	0	0	0	(397)
Issuance of treasury stock pursuant to exercise of stock options (in shares)			0
Unrealized comprehensive gain (loss) on investments			$ 0	0	0	147	0	147
Share-based compensation			0	0	13,371	0	0	13,371
Net loss			0	0	0	0	(77,270)	(77,270)
Ending Balance at Dec. 31, 2019			$ 548	(53)	489,925	20	(183,143)	307,297
Ending Balance (in shares) at Dec. 31, 2019			54,773,061
Conversion of convertible securities into common shares			$ 3	0	7,626	0	0	7,629
Conversion of convertible securities into common shares (in shares)			298,562
Issuance of common stock, net of issuance costs			$ 53	0	280,710	0	0	280,763
Issuance of common stock, net of issuance costs (in shares)			5,339,286
Issuance of common stock pursuant to exercise of stock options			$ 6	0	2,552	0	0	2,558
Issuance of common stock pursuant to exercise of stock options (in shares)			586,857
Issuance of common stock pursuant to exercise of warrant (in shares)			1,601
Issuance of warrants					26,562			26,562
Stock repurchase			$ 0	$ 0		0	0	(72)
Stock repurchase					(72)
Stock repurchase (in shares)				(3,000)
Sale of treasury stock			$ 0	$ 667	(76)	0	0	591
Sale of treasury stock (in shares)			0
Issuance of treasury stock pursuant to exercise of stock options			$ 0	(614)	0	0	0	(614)
Issuance of treasury stock pursuant to exercise of stock options (in shares)			0
Unrealized comprehensive gain (loss) on investments			$ 0	0	0	(62)	0	(62)
Share-based compensation			0	0	18,567	0	0	18,567
Net loss			0	0	0	0	(139,700)	(139,700)
Ending Balance at Dec. 31, 2020			$ 610	$ 0	$ 825,794	$ (42)	$ (322,843)	$ 503,519
Ending Balance (in shares) at Dec. 31, 2020			60,996,367

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Consolidated Statements of Stockholders' Equity [Abstract]
Issuance of common shares, issuance costs	$ 9.3

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities:
Net loss	$ (139,700)	$ (77,270)	$ (74,518)
Adjustments to reconcile net loss to net cash used in operating activities:
Accretion of discount on convertible notes	2,758	3,602	3,059
Depreciation and amortization expense	1,145	426	330
Write down of property and equipment	419	0	0
Stock-based compensation	18,567	13,371	13,601
Expense in Connection with Warrant Issue	26,562	0	0
Loss on disposal of property and equipment	0	0	317
Accretion of discount (amortization of premium) on investments, net	580	(1,066)	(801)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(1,517)	(917)	(1,505)
Accounts payable and accrued expenses	11,015	(2,722)	5,890
Operating lease liabilities	(139)	(87)	(161)
Finance lease liability	5,557	0	0
Other long term liabilities	113	0	0
Net cash used in operating activities	(74,640)	(64,663)	(53,788)
Investing activities:
Cash acquired in connection with the Reverse Merger	0	0	76,348
Purchases of investments	(209,343)	(184,298)	(141,087)
Proceeds from maturities of investments	141,811	168,556	61,276
Payments made to acquire right of use asset	(8,452)	0	0
Proceeds from sale of property and equipment	0	0	20
Purchases of property and equipment	(20,607)	(23,269)	(1,453)
Payment of security deposit	0	0	(376)
Net cash used in investing activities	(96,591)	(39,011)	(5,272)
Financing activities:
Issuance of common stock, net of issuance costs	280,763	177,760	154,022
Issuance of common stock, pursuant to exercise of stock options	2,558	31	148
Common stock repurchase	(72)	0	0
Treasury stock repurchase	0	0	(668)
Proceeds from sale of treasury stock	591	344	0
Payment of withholding tax on option exercise	(614)	(344)	0
Convertible notes refinancing costs to the lender	(237)	0	0
Net cash provided by financing activities	282,989	177,791	153,502
Net change in cash, cash equivalents and restricted cash	111,758	74,117	94,442
Cash, cash equivalents and restricted cash at beginning of period	186,908	112,791	18,349
Cash, cash equivalents and restricted cash at end of period	298,666	186,908	112,791
Supplemental disclosure of non-cash financing and investing activities:
Accrued purchases of property and equipment	1,456	4,424	0
Accrued purchases of internal use software	300	226	0
Treasury stock purchases paid in prior year	0	726	0
Retirement of treasury stock	0	1,393	0
Witholding tax payable on shares witheld in treasury stock	0	53	0
Conversion of convertible preferred stock into common stock	0	0	41,466
Conversion of convertible notes into common stock	7,629	0	0
Unrealized (loss) gain on investments	(62)	147	(127)
Finance lease right of use asset and lease liability	20,179	0	0
Reclassification of construction in process to finance right of use asset	26,465	0	0
Supplemental cash flow information:
Cash paid for interest	2,960	2,990	4,485
Cash paid for income taxes	$ 0	$ 26	$ 2

Nature of Business and Basis of

Nature of Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2020
Nature of Business and Basis of Presentation [Abstract]
Nature of Business and Basis of Presentation	1. Nature of Business and Basis of Presentation Rocket Pharmaceuticals, Inc. (“Rocket” or the “Company”) is ex vivo ” in vivo .

Risks and Liquidity

Risks and Liquidity	12 Months Ended
	Dec. 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. Operations of the Company are subject to certain risks and uncertainties, including, among others, uncertainty of drug candidate development, technological uncertainty, uncertainty regarding patents and proprietary rights, having no commercial manufacturing experience, marketing or sales capability or experience, dependency on key personnel, compliance with government regulations and the need to obtain additional financing. 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 stage. 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 $322.8 million as of December 31, 2020. As of December 31, 2020, the Company has $482.7 million of cash, cash equivalents and investments. During the year ended December 31, 2020, the Company received net proceeds of $280.8 million from a public offering of 5,339,286 shares of common stock. Rocket expects such resources will be sufficient to fund its operating expenses and capital expenditure requirements into the second half of 2023. 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. Regarding the Company’s 2021 and 2022 Convertible Notes, the Company’s stock price is currently above the conversion price and the convertible noteholders have the option to convert the Convertible Notes to common stock or the Company has the option to redeem the convertible notes. If the noteholders either do not convert to common stock or the Company does not require conversion of the convertible notes and if the Company's share price were to go below the conversion price, as defined, (see Note 7), the Company would be required to repay the 2022 Convertible Notes payable upon maturity of the notes or refinance the convertibles notes upon maturity. The Company has previously refinanced the convertible notes in fiscal 2020 prior to maturity.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Summary of Significant Accounting Policies [Abstract]
Summary of Significant Accounting Policies	3. Summary of Significant Accounting Policies 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 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. 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 operating leases (see Note 12 “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: December 31, 2020 December 31, 2019 Cash and cash equivalents $ 297,098 $ 185,383 Restricted cash 1,568 1,525 $ 298,666 $ 186,908 Government Grants Research and development expense is presented net of reimbursements from the California Institute for Regenerative Medicine (“CIRM”), which are recognized over the period necessary to match the reimbursement with the related costs when it is probable that the Company has complied with the CIRM conditions and will receive the reimbursement. During the years ended December 31, 2020, 2019, and 2018, the Company offset $3.6 million, $1.2 million and $0 of CIRM grant funds against research and development (“R&D”) expenses (See Note 15 “CIRM Grant” for additional disclosure) Concentrations of credit risk and off-balance sheet risk Financial instruments that subject the Company to credit risk primarily consist of cash and cash equivalents and available-for-sale securities. The Company maintains its cash and cash equivalent balances with high-quality financial institutions and, consequently, the Company believes that such funds are subject to minimal credit risk. The Company’s marketable securities consist of U.S. Treasury securities, and Corporate, Government Municipal and Agency Bonds. The Company has adopted an investment policy that limits the amounts the Company may invest in any one type of investment and requires all investments held by the Company to be at least AA+/Aa1 rated, thereby reducing credit risk exposure. Investments Investments consist of investments in United States Treasury securities and Corporate, Municipal and Agency Bonds. Management determines the appropriate classification of these securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. The Company classifies its investments as available-for-sale pursuant to Financial Accounting Standards Board (“FASB”) Accounting Standard Codification (“ASC”) 320, Investments—Debt and Equity Securities Goodwill Business combinations are accounted for under the acquisition method. The total cost of an acquisition is allocated to the underlying identifiable net assets, based on their respective estimated fair values as of the acquisition date. Determining the fair value of assets acquired and liabilities assumed requires management’s judgment and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash inflows and outflows, discount rates, asset lives and market multiples, among other items. Assets acquired and liabilities assumed are recorded at their estimated fair values. The excess of the purchase price over the estimated fair values of the net assets acquired is recorded as goodwill. Goodwill is tested for impairment annually as of December 31, or more frequently when events or changes in circumstances indicate that the asset might be impaired. Examples of such events or circumstances include, but are not limited to, a significant adverse change in legal or business climate, an adverse regulatory action or unanticipated competition. The Company has one segment and one reporting unit and as such review’s goodwill for impairment at the consolidated level. When testing goodwill, the Company has the option to first assess qualitative factors for reporting units that carry goodwill. The qualitative assessment includes assessing the totality of relevant events and circumstances that affect the fair value or carrying value of the reporting unit. These events and circumstances include macroeconomic conditions, industry and competitive environment conditions, overall financial performance, reporting unit specific events and market considerations. The Company also considers recent valuations of the reporting unit, including the magnitude of the difference between the most recent fair value estimate and the carrying value, as well as both positive and adverse events and circumstances, and the extent to which each of the events and circumstances identified may affect the comparison of a reporting unit’s fair value with its carrying value. If the qualitative assessment results in a conclusion that it is more likely than not that the fair value of a reporting unit exceeds the carrying value, then no further testing is performed for that reporting unit. As of January 1, 2018, the Company early adopted ASU No. 2017-04, “Intangibles- Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment”, an amendment to simplify the subsequent quantitative measurement of goodwill by eliminating step two from the goodwill impairment test. An entity will recognize an impairment charge for the amount by which the carrying amount of a reporting unit exceeds its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. An entity still has the option to perform the qualitative test for a reporting unit to determine if the quantitative impairment test is necessary. The Company performed the qualitative assessment of its goodwill and determined that it is more likely than not that the fair value of a reporting unit exceeds the carrying value of the reporting unit. As a result, the Company has determined there was no goodwill impairment as of and for the years ended December 31, 2020, 2019 and 2018 Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the useful life of the asset. The estimated useful lives are three Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the asset’s carrying amount may not be recoverable. The Company conducted our long-lived asset impairment analyses in accordance with ASC 360-10-15, Impairment or Disposal of Long-Lived Assets.”ASC 360-10-15 requires us to group assets and liabilities at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities and evaluate the asset group against the sum of the undiscounted future cash flows. If the undiscounted cash flows do not indicate the carrying amount of the asset is recoverable, an impairment charge is measured as the amount by which the carrying amount of the asset group exceeds its fair value based on discounted cash flow analysis or appraisals. There is no impairment of long-lived assets as of and for the years ended December 31, 2020, 2019 and 2018. Fair Value Measurements The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. FASB ASC 820, Fair Value Measurements and Disclosures Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly. Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The fair value of the Company’s financial instruments, including cash and cash equivalents, restricted cash, deposits, accounts payable and accrued expenses approximate their respective carrying values due to the short-term nature of these instruments. Research and Development Expenses R&D costs, which include salaries and staff costs, license costs, manufacturing and development costs, clinical trial expenses, regulatory and scientific consulting fees, as well as contract research, and stock-based compensation expense, are accounted for in accordance with ASC Topic 730, Research and Development (“ASC 730”). The Company does not currently have any commercial biopharmaceutical products and does not expect to have any for several years, if at all. Accordingly, R&D costs are expensed as incurred. While certain of the Company’s R&D costs may have future benefits, the policy of expensing all R&D expenditures is predicated on the fact that the Company has no history of successful commercialization of product candidates to base any estimate of the number of future periods that would be benefited. Foreign Currency Transactions Certain transactions during the years ended December 31, 2020, 2019 and 2018 are denominated in Euros and British pounds. Gains and losses on foreign currency transactions were not significant for the years ended December 31, 2020, 2019 and 2018. Treasury Stock The Company records treasury stock at cost. Stock-Based Compensation The Company issues stock-based awards to employees and non-employees, generally in the form of stock options and restricted stock units. The Company accounts for its stock-based compensation awards in accordance with FASB ASC Topic 718, Compensation—Stock Compensation (“ASC 718”). ASC 718 requires all stock-based payments, including grants of stock options and restricted stock units and modifications to existing stock options, to be recognized in the consolidated statements of operations and comprehensive loss based on their fair values. The Company measures the compensation expense of employee and nonemployee services received in exchange for an award of equity instruments based on the fair value of the award on the grant date. That cost is recognized on a straight-line basis over the period during which the employee and nonemployee is required to provide service in exchange for the award. The fair value of options on the date of grant is calculated using the Black-Scholes option pricing model based on key assumptions such as stock price, expected volatility and expected term. The Company’s estimates of these assumptions are primarily based on the trading price of the Company’s stock, historical data, peer company data and judgment regarding future trends and factors. The Company classifies stock-based compensation expense in its consolidated statement of operations in the same manner in which the award recipient’s payroll costs and services are classified or in which the award recipient’s service payments are classified. The Company recognizes compensation expense for at least the portion of awards that are vested. Forfeitures are accounted for as they occur. Effective July 1, 2018, the Company adopted ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting NYC Biotechnology Tax Credit Program New York City allowed investors and owners of emerging technology companies focused on biotechnology to claim a tax credit against the General Corporation Tax and Unincorporated Business Tax for amounts paid or incurred for certain facilities, operations, and employee training in New York City. The credit was recognized as research and development incentives when approved by New York City of the eligibility for the credit and the credit amount. During the years ended December 31, 2020, 2019 and 2018, the Company recorded research and development incentive income of $ , $ million, and $ million, respectively. Income Taxes The Company accounts for income taxes under the asset and liability method. The Company recognizes deferred tax assets and liabilities for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases, as well as for operating loss and tax credit carry-forwards. The Company measures deferred tax assets and liabilities using enacted tax rates expected to apply to taxable income in the years in which the Company expects to recover or settle those temporary differences. The Company recognizes the effect of a change in tax rates on deferred tax assets and liabilities in the results of operations in the period that includes the enactment date. The Company reduces the measurement of a deferred tax asset, if necessary, by a valuation allowance if it is more likely than not that the Company will not realize some or all of the deferred tax asset. The Company’s deferred tax assets relate primarily to its net operating loss carryforwards and other balance sheet differences. In accordance with ASC 740 “Income Taxes”, the Company recorded a full valuation allowance to fully offset the net deferred tax asset because it is not more likely than not that the Company will realize future benefits associated with these deferred tax assets at December 31, 2020 and 2019. The Company accounts for uncertainty in income taxes recognized in the financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. Net Loss Per Share The Company calculates net loss per share in accordance with FASB ASC 260, Earnings per Share. Segment Reporting Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one operating segment. Comprehensive Loss Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions, and other events and circumstances from non-owner sources and consists of net loss and changes in unrealized gains and losses on investments. 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. 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. Accounting Standards Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 362): Measurement of Credit Losses on Financial Statements (“ASU 2016-13”). The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. It also limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The targeted transition relief standard allows filers an option to irrevocably elect the fair value option of ASC 825-10, Financial Instruments-Overall, applied on an instrument-by-instrument basis for eligible instruments. The new standard will be effective beginning January 1, 2021. The Company is currently evaluating the potential impact ASU 2016-13, and related updates, will have on its financial position and results of operations upon adoption, however ASU 2016-13 is not expected to have a material impact.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 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 December 31, 2020 Using: Level 1 Level 2 Level 3 Total Assets: Cash and cash equivalents: Money market mutual funds $ 193,312 $ - $ - $ 193,312 United States Treasury securities 62,497 - - 62,497 Corporate Bonds - 501 - 501 Agency Bonds - 8,015 - 8,015 255,809 8,516 - 264,325 Investments: United States Treasury securities 112,328 - - 112,328 Corporate Bonds - 63,710 - 63,710 Municipal Bonds - 6,000 - 6,000 Agency Bonds - 3,583 - 3,583 112,328 73,293 - 185,621 $ 368,137 $ 81,809 $ - $ 449,946 Fair Value Measurements as of December 31, 2019 Using: Level 1 Level 2 Level 3 Total Assets: Cash and cash equivalents: Money market mutual funds $ 72,114 $ - $ - $ 72,114 Cash 7,542 - - 7,542 79,656 - - 79,656 Investments: 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 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, Municipal and Agency 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 and 2022 Convertible Notes as of December 31, 2020 was $9.5 million and $65.6 million, respectively (see Note 7).

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2020
Property and Equipment, Net [Abstract]
Property and Equipment, Net	5. Property and Equipment, Net The Company’s property and equipment consisted of the following: December 31, 2020 December 31, 2019 Laboratory equipment $ 7,807 $ 1,910 Machinery and equipment 9,933 - Computer equipment 218 179 Furniture and fixtures 1,880 273 Leasehold improvements 29 29 Internal use software 1,385 226 Construction costs in progress - 27,809 21,252 30,426 Less: accumulated depreciation and amortization (2,046 ) (905 ) $ 19,206 $ 29,521 Construction costs in progress as of December 31, 2019 was comprised of costs associated with the build out of the Company’s research, manufacturing and office facility in Cranbury, NJ. See Note 12 “Commitments and Contingencies” for the treatment of construction costs as part of the right of use asset as of December 31, 2020. Depreciation and amortization during the years ended December 31, 2020, 2019, and 2018 was $1.1 million, $0.4 million and $0.3 million, respectively.

Accounts Payable and Accrued Ex

Accounts Payable and Accrued Expenses	12 Months Ended
	Dec. 31, 2020
Accounts Payable and Accrued Expenses [Abstract]
Accounts Payable and Accrued Expenses	6. Accounts Payable and Accrued Expenses At December 31, 2020 and 2019, the Company’s accounts payable and accrued expenses consisted of the following: December 31, 2020 December 31, 2019 Research and development $ 14,962 $ 7,418 Property and equipment 1,456 4,424 Employee compensation 4,875 2,588 Accrued interest 1,122 1,241 Government grant payable 590 562 Professional fees 1,332 553 Internal use software 300 226 Other 835 340 $ 25,472 $ 17,352

Convertible Notes Payable

Convertible Notes Payable	12 Months Ended
	Dec. 31, 2020
Convertible Notes Payable [Abstract]
Convertible Notes Payable	7. Convertible Notes Payable 2021 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 amount 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 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 2022 Convertible Notes On February 20, 2020 and June 5, 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, on February 20, 2020, the Company exchanged approximately $39.35 million aggregate principal amount of the 2021 Convertible Notes (representing 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 Also pursuant to the Exchange Agreements, on June 12, 2020, the Company exchanged $7.5 million aggregate principal amount of the 2021 Convertible Notes for (a) $7.5 million aggregate principal amount of its newly issued 6.25% Convertible Senior Notes due 2022 (an exchange ratio equal to 1.00 2022 Convertible Notes per exchanged 2021 Convertible Notes) and (b) approximately $11 to pay the accrued and unpaid interest on the exchanged 2021 Convertible Notes from, and including, February 1, 2020, to, but excluding, the closing date of the exchange transaction, adjusted to take into account the unearned accrued interest on the 2022 Convertible Notes from, and including, February 20, 2020, to the closing date of the exchange transaction. The 2022 Convertible Notes were issued in a private placement exempt from registration in reliance on Section 4(a)(2) of the Securities Act of 1933, as amended. The 2022 Convertible Notes issued in the exchange transaction were issued as additional notes pursuant to the Indenture, dated as of August 5, 2016, between the Company and Wilmington Trust, National Association, as trustee, as supplemented by the Second Supplemental Indenture, dated as of February 20, 2020, governing the 2022 Convertible Notes. The conversion rate for the 2022 Convertible Notes is initially 31.1876 shares of the Company’s common stock per 1.00 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 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. In December, 2020, $8.5 million principal amount, representing a carrying value of $7.6 million of the 2022 Convertible Notes were converted into 298,562 shares of common stock. The table below summarizes the carrying value of the 2021 Convertible Notes as of December 31, 2020: December 31, 2020 December 31, 2019 Principal amount $ 5,150 $ 52,000 Discount (275 ) (6,951 ) Carrying value as of December 31, 2020 $ 4,875 $ 45,049 Accretion of the 2021 Convertible Notes discount was $1.3 million, $3.6 million, and $3.1 million for the years ended December 31, 2020, 2019, and 2018, respectively. The table below summarizes the carrying value of the 2022 Convertible Notes as of December 31, 2020: December 31, 2020 Principal amount $ 38,350 Discount (3,284 ) Carrying value as of December 31, 2020 $ 35,066 Accretion of the 2022 Convertible Notes discount was $1.5 million for the year ended December 31, 2020.

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2020
Stockholders' Equity [Abstract]
Shareholders' Equity	8. Stockholders’ Equity Common Stock The Company is currently authorized to issue up to shares of $ par value common stock. All issued shares of common stock are entitled to vote on a 1 share/ vote basis. Second Amended and Restated 2014 Stock Option and Incentive Plan In March 2018, Rocket’s board of directors approved the Second Amended and Restated 2014 Stock Option and Incentive Plan (the “Revised 2014 Plan”) which was approved by the Company’s shareholders at the Annual Meeting held on June 25, 2018. Treasury Stock In January 2019, the total of 100,000 of treasury stock shares were retired and the total of $1.3 million was reclassified to additional paid in capital. On December 12, 2019, the Company recorded treasury stock of $ million for shares withheld to pay the payroll tax liability of an option exercise . The related payroll tax liability is included in the consolidated balance sheets as of December 31, 2019 within accounts payable and accrued expenses. During fiscal 2020, the Company recorded treasury stock for shares withheld to pay the payroll tax liability of option exercises which were remitted prior to December 31, 2020. Public Offerings On April 18, 2019, the Company completed a public offering of 5,175,000 shares of common stock, which includes the full exercise of the underwriters’ option to purchase an additional 675,000 shares of our common stock, at a public offering price of $17.50 per share. The gross proceeds to Rocket from the April 2019 public offering were approximately $90.6 million, after deducting $4.5 million of offering costs, commissions, legal and other expenses for net proceeds from the offering of $86.1 million. On December 10, 2019, the Company completed a public offering of 4,393,000 shares of common stock, which includes the full exercise of the underwriters’ option to purchase an additional 573,000 shares of our common stock, at a public offering price of $22.25 per share. The gross proceeds to Rocket from the December 2019 public offering were approximately $99.7 million, net of $6.1 million of offering costs, commissions, legal and other expenses for net proceeds from the offering of $91.7 million. On December 14, 2020, the Company completed a public offering of shares of common stock, which includes the full exercise of the underwriters’ option to purchase an additional shares of our common stock, at a public offering price of $ per share. The gross proceeds to Rocket from the public offering were approximately $ million, net of $ million of offering costs, commissions, legal and other expenses for net proceeds from the offering of $

Stock-Based Awards

Stock-Based Awards	12 Months Ended
	Dec. 31, 2020
Stock-Based Awards [Abstract]
Stock-Based Awards	9. Stock-Based Awards Stock Option Valuation Effective July 1, 2018, the Company adopted ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting Years Ended December 31, 2020 2019 2018 Risk-free interest rate 1.00 % 2.26 % 2.64 % Expected term (in years) 5.84 5.81 5.85 Expected volatility 76.98 % 75.71 % 87.70 % Expected dividend yield 0.00 % 0.00 % 0.00 % Exercise price $ 22.96 $ 14.47 $ 17.82 Fair value of common stock $ 22.96 $ 14.47 $ 17.98 The following table summarizes stock option activity for the years ended December 31, 2020 and 2019, under the Revised 2014 Plan: Number of Shares Weighted Average Exercise Price Weighted Average Contractual Term (Years) Aggregate Intrinsic Value Outstanding as of December 31, 2018 8,615,997 $ 4.48 7.51 $ 94,474 Granted 1,706,116 14.47 9.29 Exercised (110,325 ) 2.31 1,429 Cancelled (448,247 ) 10.83 Outstanding as of December 31, 2019 9,763,541 $ 5.95 6.96 $ 164,021 Granted 2,193,546 22.96 8.97 Exercised (586,857 ) 4.82 13,494 Cancelled (319,299 ) 15.82 Outstanding as of December 31, 2020 11,050,931 $ 9.10 6.55 $ 504,079 Options vested and exercisable as of December 31, 2020 8,244,686 $ 4.98 5.70 $ 409,530 Options unvested as of December 31, 2020 2,806,245 $ 21.15 9.04 The weighted average grant-date fair value per share of stock options granted during the years ended December 31, 2020, 2019 and 2018 was $15.10, $9.58, and $ , The total fair value of options vested during the years ended December 31, 2020 and 2019 was $15.6 million and $63.1 million, respectively. Stock-Based Compensation Stock-based compensation expense recognized by award type is as follows: Years Ended December 31, 2020 2019 2018 Stock options $ 18,527 $ 13,371 $ 13,601 Restricted stock units 40 - - Total share based compensation expense $ 18,567 $ 13,371 $ 13,601 Stock-based compensation expense by classification included within the consolidated statements of operations and comprehensive loss was as follows: Years Ended December 31, 2020 2019 2018 Research and development $ 7,355 $ 6,153 $ 7,375 General and administrative 11,211 7,218 6,226 Total share based compensation expense $ 18,567 $ 13,371 $ 13,601 In addition, the Company issued warrants to a related party for $26.6 million (see Note 16- Related Party Transactions). As of December 31, 2020, the Company had an aggregate of $30.4 million of unrecognized stock-based compensation expense, which is expected to be recognized over the weighted average period of 2.1 year s. Restricted Stock The following table summarizes our RSU activity for the year ended December 31, 2020: Number of Shares Weighted Average Grant Date Fair Value Unvested as of December 31, 2019 - - Granted 20,000 $ 25.06 Unvested as of December 31, 2020 20,000 The intrinsic vested during the years ended December 31, 2020 and 2019 was $ million and $ . As of December 31, 2020, there was approximately $ million of unrecognized compensation cost granted. This amount is expected to be recognized over a weighted average period of Warrants During the year ended December 31, 2020, 7,051 of warrants were exercised into 1,601 shares of common stock. The Company has warrants outstanding as of December 31, 2020, convertible into 7,051 and 603,386 of common shares at an exercise price of $24.82 and $57.11 per share, which expire on June 28, 2023 and December 21, 2030, respectively.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 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: For the Years Ended December 31, 2020 2019 2018 Numerator: Net loss attributable to common stockholders $ (139,700 ) $ (77,270 ) $ (74,518 ) Denominator: Weighted-average common shares outstanding - basic and diluted 55,380,740 49,010,358 39,377,666 Net loss per share attributable to common stockholders - basic and diluted $ (2.52 ) $ (1.58 ) $ (1.89 ) 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: For the Years Ended December 31, 2020 2019 2018 Shares issuable upon conversion of the 2021 Convertible Notes 160,536 1,620,948 1,620,948 Shares issuable upon conversion of the 2022 Convertible Notes 1,195,449 - - Warrants exercisable for common shares 610,437 14,102 14,102 Options to purchase common shares 11,050,931 9,608,537 8,615,997 13,017,353 11,243,587 10,251,047

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Taxes [Abstract]
Income Taxes	11. Income Taxes No provision for federal or state income taxes was recorded during the years ended December 31, 2020, 2019 and 2018, as the Company incurred operating losses and maintains a full valuation allowance against its net deferred tax assets. A reconciliation of income tax benefit computed at the statutory federal income tax rate to income taxes as reflected in the financial statements is as follows: For the years ended December 31, 2020 2019 2018 U.S. federal tax at statutory rate 21.0 % 21.0 % 21.0 % Change in state tax apportionment 0.1 % (17.4 )% 15.8 % Stock compensation 0.9 % (0.7 )% 0.0 % Section 382 limitation 0.0 % 0.0 % (38.7 )% Valuation allowance (35.0 )% (5.1 )% 3.5 % Tax credits 13.5 % 0.0 % 0.0 % Other (0.5 )% 2.1 % (1.6 )% Effective tax rate 0 % 0 % 0 % The significant components of the Company’s deferred income tax assets and liabilities after applying the enacted corporate tax rates are as follows: At December 31, 2020 2019 2018 Deferred income tax assets (liabilities) Net operating losses (“NOL”) $ 42,613 $ 18,471 $ 27,825 R&D Credits 21,359 2,517 575 Capitalized research and development costs 23,179 27,652 17,098 Other 1,189 643 1,385 Stock-based compensation 7,406 3,896 4,563 Debt discount (748 ) (1,460 ) (3,652 ) Warrants 5,585 - - Valuation allowance (100,583 ) (51,719 ) (47,794 ) Net deferred income tax asset $ - $ - $ - As of December 31, 2020, the Company had federal and state net operating loss carryforwards of approximately $194.3 million and $26.0 million, respectively, which begin to expire in 2025 2035 2038 As required by ASC 740, Income Taxes Under Internal Revenue Code Section 382, if a corporation undergoes an “ownership change,” the corporation’s ability to use its pre-change NOL carryforwards and other pre-change tax attributes to offset its post-change income may be limited. The Company has completed a study to assess whether an ownership change has occurred or whether there have been multiple ownership changes since the Company became a “loss corporation” as defined in Section 382. The Company experienced multiple ownership changes occurring in 2005, 2007, 2015, and 2018. The ownership change has and will continue to subject our pre-ownership change net operating loss carryforwards to an annual limitation, which will significantly restrict our ability to use them to offset taxable income in periods following the ownership change. In general, the annual use limitation equals the aggregate value of our stock at the time of the ownership change multiplied by a specified tax-exempt interest rate. As a result of the ownership change, the Company is limited to an approximate $ million annual limitation on our ability to utilize our pre-merger NOL’s and R&D Credits. Due to this limitation, approximately $ million of the $ million pre-merger Federal NOL will expire unutilized as the cumulative limitation amount over a carryforward period is $ million. Additionally, $ million of Federal R&D Credits will expire unutilized. As a result, the Company has reduced its deferred tax assets related to the Federal NOL and Federal R&D Credits by an aggregate of $ million which is offset by the corresponding decrease in the valuation allowance. . The calculation of our tax liabilities involves dealing with uncertainties in the application of complex tax laws and regulations for both federal taxes and the many states in which Rocket operates or does business in. ASC 740 states that a tax benefit from an uncertain tax position may be recognized when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, on the basis of the technical merits. The Company records uncertain tax positions as liabilities in accordance with ASC 740 and adjusts these liabilities when our judgment changes as a result of the evaluation of new information not previously available. Because of the complexity of some of these uncertainties, the ultimate resolution may result in a payment that is materially different from our current estimate of the unrecognized tax benefit liabilities. These differences will be reflected as increases or decreases to income tax expense in the period in which new information is available. As of December 31, 2020 and 2019 the Company has not recorded any uncertain tax positions in its financial statements. The Company recognizes interest and penalties related to unrecognized tax benefits on the income tax expense line in the accompanying consolidated statement of operations. As of December 31, 2020, 2019 and 2018, no accrued interest or penalties are included on the related tax liability line in the consolidated balance sheets. This Company in currently being audited by New York City for the 2017 tax year. There are no proposed adjustments at this time.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies [Abstract]
Commitments and Contingencies	12. Commitments and Contingencies The Company adopted ASU 2016-02, Leases In adopting ASU 2016-02, the Company elected the available package of practical expedients which allows the Company to not reassess previous accounting conclusions around whether arrangements are or contain leases, the classification of leases, and the treatment of initial direct costs. The Company also made an accounting policy election to utilize the short-term lease exemption, whereby leases with a term of 12 months or less will not follow the recognition and measurement requirements of the new standard. Upon adoption, the Company recognized total right-of-use assets of $2.6 million, with corresponding liabilities of $3.1 million on the 2019 consolidated balance sheets, including the reclassification of $0.5 million from deferred rent to right-of-use assets. The Company determines if an arrangement is a lease at inception. Operating leases are included in our balance sheet as right-of-use assets from operating leases, current operating lease liabilities and long-term operating lease liabilities. 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. 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 Rocket has entered into 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 dedicated to AAV Current Good Manufacturing Practice (cGMP) manufacturing to support the Company’s pipeline, to commence later in 2021. 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 Company began making lease payments 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. Prior to the lease commencement date, the lease payments were recorded as prepaid rent. The Company determined the lease commencement date 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 on the balance sheet 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 of March 15, 2020. Since the lease commencement date, the Company reclassified an additional $4.5 million bringing the aggregate reclassification to $32.1 million of construction costs in progress as part of the right of use asset. 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 lease is estimated to be approximately $29.3 million over the 15-year term of the lease. 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 December 31, 2020 and 2019. The Company entered into the lease prior to the building being available for use as the building construction was not complete. The total restricted cash balance for the Company’s operating and finance leases at December 31, 2020 and 2019 was $1.1 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 (the “NY Lease Agreement”). Effective May 31, 2020 the Company terminated the lease and recorded a loss on lease termination of for the year ended December 31, 2020 On June 7, 2018, the Company entered into a three-year lease agreement for office space in the Empire State Building (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 December 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 Rent expense was $1.1 million, $0.9 million, and $0.8 million for the years ended December 31, 2020, 2019 and 2018, respectively. Lease cost December 31, 2020 Operating lease cost $ 813 Finance lease cost Amortization of right of use assets 1,711 Interest on lease liablities 1,522 Total lease cost $ 4,046 The following table summarizes the maturity of the Company’s lease liabilities on an undiscounted cash flow basis and a reconciliation to the operating lease liabilities recognized on the Company’s balance sheet as of December 31, 2020: Maturity of operating lease liabilities December 31, 2020 2021 682 2022 445 2023 75 Total lease payments $ 1,202 Less: interest (78 ) Total operating lease liabilities $ 1,124 Maturity of finance lease liability December 31, 2020 2021 1,644 2022 1,689 2023 1,736 2024 1,791 Thereafter 48,768 Total lease payments $ 55,628 Less: interest (34,996 ) Total finance lease liability $ 20,632 Leases December 31, 2020 Operating right-of-use assets $ 914 Operating current lease liabilities 626 Operating noncurrent lease liabilities 498 Total operating lease liabilities $ 1,124 Finance right-of-use assets $ 50,521 Finance current lease liability 1,644 Finance noncurrent lease liability 18,988 Total finance lease liability $ 20,632 Other information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 898 Cash flows from finance lease $ 1,070 Weighted-average remaining lease term - operating leases 1.8 years Weighted-average remaining lease term - finance lease 23.7 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 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	12 Months Ended
	Dec. 31, 2020
Agreements Related to Intellectual Property [Abstract]
Agreements Related to Intellectual Property	13. Agreements Related to Intellectual Property The Company, directly and through its subsidiary Spacecraft , LLC, 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. Contract Research and Collaboration Agreement with Lund University and J. Richter In August 2016, Rocket entered into a research and collaboration agreement with Lund University and Johan Richter, M.D., Ph.D. under which Dr. Richter grants to Rocket an exclusive, perpetual, sublicensable, worldwide license to certain intellectual property rights of Dr. Richter relating to lentiviral-mediated gene transfer to treat IMO. In exchange for the license, Rocket is obligated to make an up-front payment, certain clinical and commercial milestone payments, royalty payments (on net sales of products covered by a valid claim within the licensed intellectual property) and sublicense revenue payments to Dr. Richter. Under the terms of the agreement, Lund University and Dr. Richter are obligated to perform contract research for Rocket regarding the use of lentiviral-mediated gene transfer to treat IMO. Intellectual property resulting from the contract research created by Dr. Richter is included in the license described above and also subject to an option for Rocket to purchase ownership of such rights. Intellectual property created by Lund University in conducting such research is non-exclusively licensed to Rocket for non-commercial use and also subject to an option for Rocket to purchase or license such intellectual property under commercially reasonable terms. Rocket is obligated to pay for the contract research according to an agreed budget in quarterly installments in advance. As consideration for an option to acquire rights from Lund University on commercially reasonable terms and conditions, Rocket paid Lund University an upfront license fee of €0.02 million (approximately $0.02 million), which was expensed as research and development costs. Rocket is obligated to make aggregate milestone payments of up to €0.1 million (approximately $0.1 million) to Lund University and Dr. Richter upon the achievement of specified development and regulatory milestones. With respect to any commercialized products covered by the Lund University agreement, Rocket is obligated to pay a low single digit percentage royalty on net sales, subject to specified adjustments, by Rocket or its sublicensees or affiliates. In the event that Rocket enters into a sublicense agreement with a sublicensee, Rocket will be obligated to pay a portion of any consideration received from such sublicensees in specified circumstances. The research and collaboration agreement had an initial term of months and was amended to extend the term multiple times. In January the research and collaboration agreement was extended until License Agreement for Danon Disease with UCSD In February 2017, the Company entered into a License Agreement with The Regents of the University of California, represented by its San Diego campus (“UCSD”), under which UCSD granted us an exclusive, sublicensable, worldwide license to certain intellectual property rights for the treatment of lysosomal storage diseases, including Danon disease. In exchange for the license, the Company became obligated to make an up-front payment, certain clinical and commercial milestone payments, royalty payments (on net sales of products covered by a valid claim within the licensed intellectual property), maintenance fees and sublicense revenue payments. The upfront license fee of $0.05 million was expensed as research and development costs. The Company is obligated to make aggregate milestone payments of up to $1.5 million to UCSD upon the achievement of specified development and regulatory milestones for the treatment of Danon disease. A reduced schedule of milestone payments applies to achieving the same milestones for additional indications. With respect to any commercialized products covered by the agreement, the Company is obligated to pay a low single digit percentage royalty on net sales, subject to specified adjustments. If it enters into a sublicense agreement with a sublicensee, it will be obligated to pay a portion of any consideration received from such sublicensees in specified circumstances. The Company is also subject to certain diligence milestones for development of a product using the intellectual property licensed from UCSD under this agreement. The term of the license agreement with UCSD is through the expiration of the licensed patents, some of which are still in the pending application phase. REGENXBIO, Inc. License On November 19, 2018, the Company entered into a license agreement with REGENXBIO Inc. (“RGNX”), pursuant to which the Company obtained an exclusive license for all U.S. patents and patent applications related to RGNX’s NAV AAV-9 vector for the treatment of Danon disease in humans by in vivo Under the terms of the license agreement, the Company is obligated to use commercially reasonable efforts to develop, commercialize, market, promote and sell products incorporating the Licensed Patents (“Licensed Products”). Unless the license agreement is terminated earlier as provided below, the license from RGNX expires on a country-by-country, Licensed Product-by-Licensed Product basis until the later of the expiration date of the last to expire of the last valid claim of the applicable Licensed Patent or ten years after the first commercial sale of a Licensed Product in such country. The license agreement provides that RGNX may terminate the agreement upon a material breach by the Company if the Company does not cure such breach within a specified notice period if the Company commences a challenge against RGNX or certain of its licensors to declare or render invalid or unenforceable the licensed patents or upon the Company’s bankruptcy or insolvency. The Company may terminate the agreement in its entirety or terminate one or more of the licensed vectors at any time upon six months’ notice. The Company’s Option Right expires four years from the date of the license agreement. In consideration for the rights granted to the Company under the license agreement, the Company made an upfront payment to RGNX of $ million included as research and development expenses. A fee of $ million per additional vector would be due if the Company exercises its Option Right to purchase additional vectors. The license agreement provides for royalties payable to RGNX in the high-single digits to low-teens on net sales levels of Licensed Products during the royalty term. If successful, the Company will be required to make milestone payments to RGNX of up to $ million for each Licensed Product upon the achievement of specified clinical development and regulatory milestones in the U.S. and European Union. In addition, the Company shall pay RGNX of the payment fees received from a priority review voucher issued in connection with or otherwise related to a Licensed Product. These royalty obligations are subject to specified reductions if additional licenses from third parties are required. The Company must also pay RGNX a portion of all non-royalty sublicense income (if any) received from sublicensees. The Company paid a $ million license fee payment under the RGNX agreement upon the dosing of the first Danon patient in 2019. additional milestones were achieved and related payments made during the year ended December

Strategic Research Collaboratio

Strategic Research Collaboration	12 Months Ended
	Dec. 31, 2020
Strategic Research Collaboration [Abstract]
Strategic Research Collaboration	14. 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 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 was due upon execution of the collaboration agreement and the remaining $ 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 for the LGCM became due and was expensed and paid. During the year ended December 31, 2020, the remaining milestone under this collaboration agreement was met and the Company expensed and paid the final milestone payment of $ million

CIRM Grant

CIRM Grant	12 Months Ended
	Dec. 31, 2020
CIRM Grant [Abstract]
CIRM Grant	15. CIRM Grant On April 30, 2019, the California Institute for Regenerative Medicine (“CIRM”) awarded the Company In 2019, the Company received the first grants from CIRM in the aggregate of $ 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. During the year ended December 31, 2020, the Company met the next CIRM milestone and recorded a receivable, included in prepaid and other assets in the consolidated balance sheet, and a reduction of research and development expenses of $ million. The Company received the $ million cash advance on January 4, 2021. On November 12, 2020, the CIRM awarded Rocket up to $ million under a CLIN2 grant award to support the clinical development of its lentiviral vector (LVV)-based gene therapy, RP-L401, for the treatment of IMO. The Company received a $ million cash advance on January 4, 2021 related to the CIRM IMO award and recorded a receivable, included in prepaid and other assets in the consolidated balance sheet, and a reduction of research and development expenses of $ million

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	16. Related Party Transactions During April 2018, the Company entered into an agreement with a member of the Board of Directors for business development consulting services. Payments for the services under the agreement are $ per quarter, and the Company may terminate the agreement with days’ notice. The Company incurred expenses for all of the years ended December 31, 2020, 2019 and 2018, relating to services provided under this agreement. In June 2020, the Company entered into a consulting agreement with a member of the Board of Directors for pipeline development, new asset evaluation, and corporate strategy. In lieu of cash for services to be provided under the consulting agreement during its term, the Company granted the board member option to purchase common stock with a fair value of $ million. In October 2020, the Company entered into a consulting agreement with the spouse of one of the Company’s executive officers for information technology advisory services. In exchange for the services provided under the agreement, the Company granted restricted stock units which vest over a period. On December 21, 2020, the Company entered into a consulting agreement with a related party. Pursuant to the consulting agreement, the related party provides certain business development and asset identification consulting services to the Company. The term of the consulting agreement is three years and may be terminated with 60 days’ notice by either party. In exchange for the business development services to be provided under the agreement, the Company issued a warrant exercisable for 603,386 shares of Common Stock. Pursuant to the consulting agreement, the related party is entitled to receive additional warrants exercisable for common stock upon identification of new assets for the Company to in-license. The Company recorded a non-cash R&D expense of $26.6 million in 2020 related to the issuance of the Common Stock warrant. The fair value of the warrant was calculated using the Black-Scholes fair value pricing model with the following inputs: Year Ended December 31, 2020 Risk-free interest rate 0.95 % Expected term (in years) 10.00 Expected volatility 74.20 % Expected dividend yield 0.00 % Exercise price $ 57.11 Fair value of common stock $ 57.11

401(k) Savings Plan

401(k) Savings Plan	12 Months Ended
	Dec. 31, 2020
401(k) Savings Plan [Abstract]
401(k) Savings Plan	17. 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 match 4% of employee contributions to the Plan, subject to certain limitations. The Company’s matching contribution for the years ended December 31, 2020, 2019, and 2018 was $0.3 million, $0.2 million, and $0.1 million, respectively.

Selected Quarterly Financial In

Selected Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2020
Selected Quarterly Financial Information (Unaudited) [Abstract]
Selected Quarterly Financial Information (Unaudited)	18. Selected Quarterly Financial Information (Unaudited) The following table presents selected consolidated statements of operations data for each quarter for the fiscal years ended December and (unaudited, in thousand s, except for per share data) : 2020 First quarter Second quarter Third quarter Fourth quarter Total Total revenues $ - $ - $ - $ - $ - Total operating expenses 24,120 23,559 27,387 59,237 134,303 Loss from operations (24,120 ) (23,559 ) (27,387 ) (59,237 ) (134,303 ) Net loss (24,664 ) (25,040 ) (29,080 ) (60,916 ) (139,700 ) Net loss per share attributable to common stockholders - basic and diluted $ (0.45 ) $ (0.45 ) $ (0.53 ) $ (1.09 ) $ (2.52 ) 2019 First quarter Second quarter Third quarter Fourth quarter Total Total revenues $ - $ - $ - $ - $ - Total operating expenses 18,945 18,392 19,165 19,649 76,151 Loss from operations (18,945 ) (18,392 ) (19,165 ) (19,649 ) (76,151 ) Net loss (19,451 ) (18,680 ) (19,284 ) (19,855 ) (77,270 ) Net loss per share attributable to common stockholders - basic and diluted $ (0.43 ) $ (0.38 ) $ (0.38 ) $ (0.39 ) $ (1.58 )

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Summary of Significant Accounting Policies [Abstract]
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 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.
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 operating leases (see Note 12 “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: December 31, 2020 December 31, 2019 Cash and cash equivalents $ 297,098 $ 185,383 Restricted cash 1,568 1,525 $ 298,666 $ 186,908
Government Grants	Government Grants Research and development expense is presented net of reimbursements from the California Institute for Regenerative Medicine (“CIRM”), which are recognized over the period necessary to match the reimbursement with the related costs when it is probable that the Company has complied with the CIRM conditions and will receive the reimbursement. During the years ended December 31, 2020, 2019, and 2018, the Company offset $3.6 million, $1.2 million and $0 of CIRM grant funds against research and development (“R&D”) expenses (See Note 15 “CIRM Grant” for additional disclosure)
Concentrations of Credit Risk and Off-balance Sheet Risk	Concentrations of credit risk and off-balance sheet risk Financial instruments that subject the Company to credit risk primarily consist of cash and cash equivalents and available-for-sale securities. The Company maintains its cash and cash equivalent balances with high-quality financial institutions and, consequently, the Company believes that such funds are subject to minimal credit risk. The Company’s marketable securities consist of U.S. Treasury securities, and Corporate, Government Municipal and Agency Bonds. The Company has adopted an investment policy that limits the amounts the Company may invest in any one type of investment and requires all investments held by the Company to be at least AA+/Aa1 rated, thereby reducing credit risk exposure.
Investments	Investments Investments consist of investments in United States Treasury securities and Corporate, Municipal and Agency Bonds. Management determines the appropriate classification of these securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. The Company classifies its investments as available-for-sale pursuant to Financial Accounting Standards Board (“FASB”) Accounting Standard Codification (“ASC”) 320, Investments—Debt and Equity Securities
Goodwill	Goodwill Business combinations are accounted for under the acquisition method. The total cost of an acquisition is allocated to the underlying identifiable net assets, based on their respective estimated fair values as of the acquisition date. Determining the fair value of assets acquired and liabilities assumed requires management’s judgment and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash inflows and outflows, discount rates, asset lives and market multiples, among other items. Assets acquired and liabilities assumed are recorded at their estimated fair values. The excess of the purchase price over the estimated fair values of the net assets acquired is recorded as goodwill. Goodwill is tested for impairment annually as of December 31, or more frequently when events or changes in circumstances indicate that the asset might be impaired. Examples of such events or circumstances include, but are not limited to, a significant adverse change in legal or business climate, an adverse regulatory action or unanticipated competition. The Company has one segment and one reporting unit and as such review’s goodwill for impairment at the consolidated level. When testing goodwill, the Company has the option to first assess qualitative factors for reporting units that carry goodwill. The qualitative assessment includes assessing the totality of relevant events and circumstances that affect the fair value or carrying value of the reporting unit. These events and circumstances include macroeconomic conditions, industry and competitive environment conditions, overall financial performance, reporting unit specific events and market considerations. The Company also considers recent valuations of the reporting unit, including the magnitude of the difference between the most recent fair value estimate and the carrying value, as well as both positive and adverse events and circumstances, and the extent to which each of the events and circumstances identified may affect the comparison of a reporting unit’s fair value with its carrying value. If the qualitative assessment results in a conclusion that it is more likely than not that the fair value of a reporting unit exceeds the carrying value, then no further testing is performed for that reporting unit. As of January 1, 2018, the Company early adopted ASU No. 2017-04, “Intangibles- Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment”, an amendment to simplify the subsequent quantitative measurement of goodwill by eliminating step two from the goodwill impairment test. An entity will recognize an impairment charge for the amount by which the carrying amount of a reporting unit exceeds its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. An entity still has the option to perform the qualitative test for a reporting unit to determine if the quantitative impairment test is necessary. The Company performed the qualitative assessment of its goodwill and determined that it is more likely than not that the fair value of a reporting unit exceeds the carrying value of the reporting unit. As a result, the Company has determined there was no goodwill impairment as of and for the years ended December 31, 2020, 2019 and 2018
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the useful life of the asset. The estimated useful lives are three
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the asset’s carrying amount may not be recoverable. The Company conducted our long-lived asset impairment analyses in accordance with ASC 360-10-15, Impairment or Disposal of Long-Lived Assets.”ASC 360-10-15 requires us to group assets and liabilities at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities and evaluate the asset group against the sum of the undiscounted future cash flows. If the undiscounted cash flows do not indicate the carrying amount of the asset is recoverable, an impairment charge is measured as the amount by which the carrying amount of the asset group exceeds its fair value based on discounted cash flow analysis or appraisals. There is no impairment of long-lived assets as of and for the years ended December 31, 2020, 2019 and 2018.
Fair Value Measurements	Fair Value Measurements The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. FASB ASC 820, Fair Value Measurements and Disclosures Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly. Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The fair value of the Company’s financial instruments, including cash and cash equivalents, restricted cash, deposits, accounts payable and accrued expenses approximate their respective carrying values due to the short-term nature of these instruments.
Research and Development Expenses	Research and Development Expenses R&D costs, which include salaries and staff costs, license costs, manufacturing and development costs, clinical trial expenses, regulatory and scientific consulting fees, as well as contract research, and stock-based compensation expense, are accounted for in accordance with ASC Topic 730, Research and Development (“ASC 730”). The Company does not currently have any commercial biopharmaceutical products and does not expect to have any for several years, if at all. Accordingly, R&D costs are expensed as incurred. While certain of the Company’s R&D costs may have future benefits, the policy of expensing all R&D expenditures is predicated on the fact that the Company has no history of successful commercialization of product candidates to base any estimate of the number of future periods that would be benefited.
Foreign Currency Transactions	Foreign Currency Transactions Certain transactions during the years ended December 31, 2020, 2019 and 2018 are denominated in Euros and British pounds. Gains and losses on foreign currency transactions were not significant for the years ended December 31, 2020, 2019 and 2018.
Treasury Stock	Treasury Stock The Company records treasury stock at cost.
Stock-Based Compensation	Stock-Based Compensation The Company issues stock-based awards to employees and non-employees, generally in the form of stock options and restricted stock units. The Company accounts for its stock-based compensation awards in accordance with FASB ASC Topic 718, Compensation—Stock Compensation (“ASC 718”). ASC 718 requires all stock-based payments, including grants of stock options and restricted stock units and modifications to existing stock options, to be recognized in the consolidated statements of operations and comprehensive loss based on their fair values. The Company measures the compensation expense of employee and nonemployee services received in exchange for an award of equity instruments based on the fair value of the award on the grant date. That cost is recognized on a straight-line basis over the period during which the employee and nonemployee is required to provide service in exchange for the award. The fair value of options on the date of grant is calculated using the Black-Scholes option pricing model based on key assumptions such as stock price, expected volatility and expected term. The Company’s estimates of these assumptions are primarily based on the trading price of the Company’s stock, historical data, peer company data and judgment regarding future trends and factors. The Company classifies stock-based compensation expense in its consolidated statement of operations in the same manner in which the award recipient’s payroll costs and services are classified or in which the award recipient’s service payments are classified. The Company recognizes compensation expense for at least the portion of awards that are vested. Forfeitures are accounted for as they occur. Effective July 1, 2018, the Company adopted ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting
NYC Biotechnology Tax Credit Program	NYC Biotechnology Tax Credit Program New York City allowed investors and owners of emerging technology companies focused on biotechnology to claim a tax credit against the General Corporation Tax and Unincorporated Business Tax for amounts paid or incurred for certain facilities, operations, and employee training in New York City. The credit was recognized as research and development incentives when approved by New York City of the eligibility for the credit and the credit amount. During the years ended December 31, 2020, 2019 and 2018, the Company recorded research and development incentive income of $ , $ million, and $ million, respectively.
Income Taxes	Income Taxes The Company accounts for income taxes under the asset and liability method. The Company recognizes deferred tax assets and liabilities for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases, as well as for operating loss and tax credit carry-forwards. The Company measures deferred tax assets and liabilities using enacted tax rates expected to apply to taxable income in the years in which the Company expects to recover or settle those temporary differences. The Company recognizes the effect of a change in tax rates on deferred tax assets and liabilities in the results of operations in the period that includes the enactment date. The Company reduces the measurement of a deferred tax asset, if necessary, by a valuation allowance if it is more likely than not that the Company will not realize some or all of the deferred tax asset. The Company’s deferred tax assets relate primarily to its net operating loss carryforwards and other balance sheet differences. In accordance with ASC 740 “Income Taxes”, the Company recorded a full valuation allowance to fully offset the net deferred tax asset because it is not more likely than not that the Company will realize future benefits associated with these deferred tax assets at December 31, 2020 and 2019. The Company accounts for uncertainty in income taxes recognized in the financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.
Net Loss Per Share	Net Loss Per Share The Company calculates net loss per share in accordance with FASB ASC 260, Earnings per Share.
Segment Reporting	Segment Reporting Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one operating segment.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions, and other events and circumstances from non-owner sources and consists of net loss and changes in unrealized gains and losses on investments.
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. 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. Accounting Standards Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 362): Measurement of Credit Losses on Financial Statements (“ASU 2016-13”). The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. It also limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The targeted transition relief standard allows filers an option to irrevocably elect the fair value option of ASC 825-10, Financial Instruments-Overall, applied on an instrument-by-instrument basis for eligible instruments. The new standard will be effective beginning January 1, 2021. The Company is currently evaluating the potential impact ASU 2016-13, and related updates, will have on its financial position and results of operations upon adoption, however ASU 2016-13 is not expected to have a material impact.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
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 operating leases (see Note 12 “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: December 31, 2020 December 31, 2019 Cash and cash equivalents $ 297,098 $ 185,383 Restricted cash 1,568 1,525 $ 298,666 $ 186,908

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 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 December 31, 2020 Using: Level 1 Level 2 Level 3 Total Assets: Cash and cash equivalents: Money market mutual funds $ 193,312 $ - $ - $ 193,312 United States Treasury securities 62,497 - - 62,497 Corporate Bonds - 501 - 501 Agency Bonds - 8,015 - 8,015 255,809 8,516 - 264,325 Investments: United States Treasury securities 112,328 - - 112,328 Corporate Bonds - 63,710 - 63,710 Municipal Bonds - 6,000 - 6,000 Agency Bonds - 3,583 - 3,583 112,328 73,293 - 185,621 $ 368,137 $ 81,809 $ - $ 449,946 Fair Value Measurements as of December 31, 2019 Using: Level 1 Level 2 Level 3 Total Assets: Cash and cash equivalents: Money market mutual funds $ 72,114 $ - $ - $ 72,114 Cash 7,542 - - 7,542 79,656 - - 79,656 Investments: 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 75,464 43,268 - 118,732 $ 155,120 $ 43,268 $ - $ 198,388

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2020
Property and Equipment, Net [Abstract]
Property and Equipment	The Company’s property and equipment consisted of the following: December 31, 2020 December 31, 2019 Laboratory equipment $ 7,807 $ 1,910 Machinery and equipment 9,933 - Computer equipment 218 179 Furniture and fixtures 1,880 273 Leasehold improvements 29 29 Internal use software 1,385 226 Construction costs in progress - 27,809 21,252 30,426 Less: accumulated depreciation and amortization (2,046 ) (905 ) $ 19,206 $ 29,521

Accounts Payable and Accrued _2

Accounts Payable and Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2020
Accounts Payable and Accrued Expenses [Abstract]
Accounts Payable and Accrued Expenses	At December 31, 2020 and 2019, the Company’s accounts payable and accrued expenses consisted of the following: December 31, 2020 December 31, 2019 Research and development $ 14,962 $ 7,418 Property and equipment 1,456 4,424 Employee compensation 4,875 2,588 Accrued interest 1,122 1,241 Government grant payable 590 562 Professional fees 1,332 553 Internal use software 300 226 Other 835 340 $ 25,472 $ 17,352

Convertible Notes Payable (Tabl

Convertible Notes Payable (Tables)	12 Months Ended
	Dec. 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 December 31, 2020: December 31, 2020 December 31, 2019 Principal amount $ 5,150 $ 52,000 Discount (275 ) (6,951 ) Carrying value as of December 31, 2020 $ 4,875 $ 45,049
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 December 31, 2020: December 31, 2020 Principal amount $ 38,350 Discount (3,284 ) Carrying value as of December 31, 2020 $ 35,066

Stock-Based Awards (Tables)

Stock-Based Awards (Tables)	12 Months Ended
	Dec. 31, 2020
Stock-Based Awards [Abstract]
Weighted-Average Assumptions for Stock Options	Improvements to Nonemployee Share-Based Payment Accounting Years Ended December 31, 2020 2019 2018 Risk-free interest rate 1.00 % 2.26 % 2.64 % Expected term (in years) 5.84 5.81 5.85 Expected volatility 76.98 % 75.71 % 87.70 % Expected dividend yield 0.00 % 0.00 % 0.00 % Exercise price $ 22.96 $ 14.47 $ 17.82 Fair value of common stock $ 22.96 $ 14.47 $ 17.98
Stock Option Activity	The following table summarizes stock option activity for the years ended December 31, 2020 and 2019, under the Revised 2014 Plan: Number of Shares Weighted Average Exercise Price Weighted Average Contractual Term (Years) Aggregate Intrinsic Value Outstanding as of December 31, 2018 8,615,997 $ 4.48 7.51 $ 94,474 Granted 1,706,116 14.47 9.29 Exercised (110,325 ) 2.31 1,429 Cancelled (448,247 ) 10.83 Outstanding as of December 31, 2019 9,763,541 $ 5.95 6.96 $ 164,021 Granted 2,193,546 22.96 8.97 Exercised (586,857 ) 4.82 13,494 Cancelled (319,299 ) 15.82 Outstanding as of December 31, 2020 11,050,931 $ 9.10 6.55 $ 504,079 Options vested and exercisable as of December 31, 2020 8,244,686 $ 4.98 5.70 $ 409,530 Options unvested as of December 31, 2020 2,806,245 $ 21.15 9.04
Stock-Based Compensation Expense by Award Type	Stock-based compensation expense recognized by award type is as follows: Years Ended December 31, 2020 2019 2018 Stock options $ 18,527 $ 13,371 $ 13,601 Restricted stock units 40 - - Total share based compensation expense $ 18,567 $ 13,371 $ 13,601
Stock-Based Compensation Expense	Stock-based compensation expense by classification included within the consolidated statements of operations and comprehensive loss was as follows: Years Ended December 31, 2020 2019 2018 Research and development $ 7,355 $ 6,153 $ 7,375 General and administrative 11,211 7,218 6,226 Total share based compensation expense $ 18,567 $ 13,371 $ 13,601
RSU Activity	The following table summarizes our RSU activity for the year ended December 31, 2020: Number of Shares Weighted Average Grant Date Fair Value Unvested as of December 31, 2019 - - Granted 20,000 $ 25.06 Unvested as of December 31, 2020 20,000

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 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: For the Years Ended December 31, 2020 2019 2018 Numerator: Net loss attributable to common stockholders $ (139,700 ) $ (77,270 ) $ (74,518 ) Denominator: Weighted-average common shares outstanding - basic and diluted 55,380,740 49,010,358 39,377,666 Net loss per share attributable to common stockholders - basic and diluted $ (2.52 ) $ (1.58 ) $ (1.89 )
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: For the Years Ended December 31, 2020 2019 2018 Shares issuable upon conversion of the 2021 Convertible Notes 160,536 1,620,948 1,620,948 Shares issuable upon conversion of the 2022 Convertible Notes 1,195,449 - - Warrants exercisable for common shares 610,437 14,102 14,102 Options to purchase common shares 11,050,931 9,608,537 8,615,997 13,017,353 11,243,587 10,251,047

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Taxes [Abstract]
Reconciliation of Income Tax Benefit Computed at Statutory Federal Income Tax Rate to Income Taxes	A reconciliation of income tax benefit computed at the statutory federal income tax rate to income taxes as reflected in the financial statements is as follows: For the years ended December 31, 2020 2019 2018 U.S. federal tax at statutory rate 21.0 % 21.0 % 21.0 % Change in state tax apportionment 0.1 % (17.4 )% 15.8 % Stock compensation 0.9 % (0.7 )% 0.0 % Section 382 limitation 0.0 % 0.0 % (38.7 )% Valuation allowance (35.0 )% (5.1 )% 3.5 % Tax credits 13.5 % 0.0 % 0.0 % Other (0.5 )% 2.1 % (1.6 )% Effective tax rate 0 % 0 % 0 %
Deferred Tax Assets and Liabilities	The significant components of the Company’s deferred income tax assets and liabilities after applying the enacted corporate tax rates are as follows: At December 31, 2020 2019 2018 Deferred income tax assets (liabilities) Net operating losses (“NOL”) $ 42,613 $ 18,471 $ 27,825 R&D Credits 21,359 2,517 575 Capitalized research and development costs 23,179 27,652 17,098 Other 1,189 643 1,385 Stock-based compensation 7,406 3,896 4,563 Debt discount (748 ) (1,460 ) (3,652 ) Warrants 5,585 - - Valuation allowance (100,583 ) (51,719 ) (47,794 ) Net deferred income tax asset $ - $ - $ -

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies [Abstract]
Lease Cost	Rent expense was $1.1 million, $0.9 million, and $0.8 million for the years ended December 31, 2020, 2019 and 2018, respectively. Lease cost December 31, 2020 Operating lease cost $ 813 Finance lease cost Amortization of right of use assets 1,711 Interest on lease liablities 1,522 Total lease cost $ 4,046
Maturities of Operating Lease Lease Liabilities	The following table summarizes the maturity of the Company’s lease liabilities on an undiscounted cash flow basis and a reconciliation to the operating lease liabilities recognized on the Company’s balance sheet as of December 31, 2020: Maturity of operating lease liabilities December 31, 2020 2021 682 2022 445 2023 75 Total lease payments $ 1,202 Less: interest (78 ) Total operating lease liabilities $ 1,124
Maturity of Finance Lease Liability	Maturity of finance lease liability December 31, 2020 2021 1,644 2022 1,689 2023 1,736 2024 1,791 Thereafter 48,768 Total lease payments $ 55,628 Less: interest (34,996 ) Total finance lease liability $ 20,632
Balance Sheet Information Related to Leases	Leases December 31, 2020 Operating right-of-use assets $ 914 Operating current lease liabilities 626 Operating noncurrent lease liabilities 498 Total operating lease liabilities $ 1,124 Finance right-of-use assets $ 50,521 Finance current lease liability 1,644 Finance noncurrent lease liability 18,988 Total finance lease liability $ 20,632
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 $ 898 Cash flows from finance lease $ 1,070 Weighted-average remaining lease term - operating leases 1.8 years Weighted-average remaining lease term - finance lease 23.7 years Weighted-average discount rate - operating leases 7.77 % Weighted-average discount rate - finance lease 8.96 %

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Fair Value of Warrant	The fair value of the warrant was calculated using the Black-Scholes fair value pricing model with the following inputs: Year Ended December 31, 2020 Risk-free interest rate 0.95 % Expected term (in years) 10.00 Expected volatility 74.20 % Expected dividend yield 0.00 % Exercise price $ 57.11 Fair value of common stock $ 57.11

Selected Quarterly Financial _2

Selected Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Selected Quarterly Financial Information (Unaudited) [Abstract]
Selected Quarterly Financial Information (Unaudited)	The following table presents selected consolidated statements of operations data for each quarter for the fiscal years ended December and (unaudited, in thousand s, except for per share data) : 2020 First quarter Second quarter Third quarter Fourth quarter Total Total revenues $ - $ - $ - $ - $ - Total operating expenses 24,120 23,559 27,387 59,237 134,303 Loss from operations (24,120 ) (23,559 ) (27,387 ) (59,237 ) (134,303 ) Net loss (24,664 ) (25,040 ) (29,080 ) (60,916 ) (139,700 ) Net loss per share attributable to common stockholders - basic and diluted $ (0.45 ) $ (0.45 ) $ (0.53 ) $ (1.09 ) $ (2.52 ) 2019 First quarter Second quarter Third quarter Fourth quarter Total Total revenues $ - $ - $ - $ - $ - Total operating expenses 18,945 18,392 19,165 19,649 76,151 Loss from operations (18,945 ) (18,392 ) (19,165 ) (19,649 ) (76,151 ) Net loss (19,451 ) (18,680 ) (19,284 ) (19,855 ) (77,270 ) Net loss per share attributable to common stockholders - basic and diluted $ (0.43 ) $ (0.38 ) $ (0.38 ) $ (0.39 ) $ (1.58 )

Nature of Business and Basis _2

Nature of Business and Basis of Presentation (Details)	12 Months Ended
	Dec. 31, 2020Program
Nature of Business and Basis of Presentation [Abstract]
Number of clinical-stage programs	4

Risks and Liquidity (Details)

Risks and Liquidity (Details) - USD ($) $ in Thousands	Dec. 14, 2020	Dec. 10, 2019	Apr. 18, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Risks and Liquidity [Abstract]
Accumulated deficit				$ (322,843)	$ (183,143)
Cash, cash equivalents and investments				$ 482,700
Common Stock [Member]
Shareholders' Equity Disclosure [Abstract]
Common stock shares issued (in shares)				5,339,286	9,568,000	11,475,242
IPO [Member] | Common Stock [Member]
Shareholders' Equity Disclosure [Abstract]
Net proceeds, offering amount				$ 280,800
Common stock shares issued (in shares)	5,339,286	4,393,000	5,175,000	5,339,286

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)Segment	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and cash equivalents	$ 297,098	$ 185,383
Restricted cash	1,568	1,525
Total	298,666	186,908	$ 112,791	$ 18,349
Government Grants [Abstract]
Receivable of offset grants against expenses	3,600	1,200	0
Investments [Abstract]
Realized gains (losses) on investment	0	0	0
Unrealized gain on investments	$ (62)	147	(127)
Goodwill [Abstract]
Number of operating segment | Segment	1
Number of reporting unit | Segment	1
Goodwill impairment	$ 0	0	0
Impairment of Long-Lived Assets [Abstract]
Impairment of long-lived assets	0	0	0
NYC Biotechnology Tax Credit Program [Abstract]
Research and development incentive income	$ 0	$ 300	$ 200
Internal use Software [Member]
Property and Equipment [Abstract]
Estimated useful lives	6 years
Minimum [Member]
Property and Equipment [Abstract]
Estimated useful lives	3 years
Maximum [Member]
Property and Equipment [Abstract]
Estimated useful lives	15 years

Fair Value of Financial Instr_3

Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
2021 Convertible Notes [Member]
Additional Information in Fair Value Disclosure [Abstract]
Fair value convertible note	$ 9,500
2022 Convertible Notes [Member]
Additional Information in Fair Value Disclosure [Abstract]
Fair value convertible note	65,600
Recurring [Member]
Assets [Abstract]
Cash and cash equivalents	264,325	$ 79,656
Investments	185,621	118,732
Fair value of financial instruments	449,946	198,388
Recurring [Member] | Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	193,312	72,114
Recurring [Member] | Cash [Member]
Assets [Abstract]
Cash and cash equivalents		7,542
Recurring [Member] | United States Treasury Securities [Member]
Assets [Abstract]
Cash and cash equivalents	62,497
Investments	112,328	75,464
Recurring [Member] | Government Bonds [Member]
Assets [Abstract]
Investments		8,000
Recurring [Member] | Corporate Bonds [Member]
Assets [Abstract]
Cash and cash equivalents	501
Investments	63,710	29,268
Recurring [Member] | Municipal Bonds [Member]
Assets [Abstract]
Investments	6,000	6,000
Recurring [Member] | Agency Bonds [Member]
Assets [Abstract]
Cash and cash equivalents	8,015
Investments	3,583
Recurring [Member] | Level 1 [Member]
Assets [Abstract]
Cash and cash equivalents	255,809	79,656
Investments	112,328	75,464
Fair value of financial instruments	368,137	155,120
Recurring [Member] | Level 1 [Member] | Money Market Mutual Funds [Member]
Assets [Abstract]
Cash and cash equivalents	193,312	72,114
Recurring [Member] | Level 1 [Member] | Cash [Member]
Assets [Abstract]
Cash and cash equivalents		7,542
Recurring [Member] | Level 1 [Member] | United States Treasury Securities [Member]
Assets [Abstract]
Cash and cash equivalents	62,497
Investments	112,328	75,464
Recurring [Member] | Level 1 [Member] | Government Bonds [Member]
Assets [Abstract]
Investments		0
Recurring [Member] | Level 1 [Member] | Corporate Bonds [Member]
Assets [Abstract]
Cash and cash equivalents	0
Investments	0	0
Recurring [Member] | Level 1 [Member] | Municipal Bonds [Member]
Assets [Abstract]
Investments	0	0
Recurring [Member] | Level 1 [Member] | Agency Bonds [Member]
Assets [Abstract]
Cash and cash equivalents	0
Investments	0
Recurring [Member] | Level 2 [Member]
Assets [Abstract]
Cash and cash equivalents	8,516	0
Investments	73,293	43,268
Fair value of financial instruments	81,809	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
Recurring [Member] | Level 2 [Member] | United States Treasury Securities [Member]
Assets [Abstract]
Cash and cash equivalents	0
Investments	0	0
Recurring [Member] | Level 2 [Member] | Government Bonds [Member]
Assets [Abstract]
Investments		8,000
Recurring [Member] | Level 2 [Member] | Corporate Bonds [Member]
Assets [Abstract]
Cash and cash equivalents	501
Investments	63,710	29,268
Recurring [Member] | Level 2 [Member] | Municipal Bonds [Member]
Assets [Abstract]
Investments	6,000	6,000
Recurring [Member] | Level 2 [Member] | Agency Bonds [Member]
Assets [Abstract]
Cash and cash equivalents	8,015
Investments	3,583
Recurring [Member] | Level 3 [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Investments	0	0
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
Recurring [Member] | Level 3 [Member] | United States Treasury Securities [Member]
Assets [Abstract]
Cash and cash equivalents	0
Investments	0	0
Recurring [Member] | Level 3 [Member] | Government Bonds [Member]
Assets [Abstract]
Investments		0
Recurring [Member] | Level 3 [Member] | Corporate Bonds [Member]
Assets [Abstract]
Cash and cash equivalents	0
Investments	0	0
Recurring [Member] | Level 3 [Member] | Municipal Bonds [Member]
Assets [Abstract]
Investments	0	$ 0
Recurring [Member] | Level 3 [Member] | Agency Bonds [Member]
Assets [Abstract]
Cash and cash equivalents	0
Investments	$ 0

Property and Equipment, Net (De

Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property and Equipment [Abstract]
Property and equipment, gross	$ 21,252	$ 30,426
Less: accumulated depreciation and amortization	(2,046)	(905)
Property and equipment, net	19,206	29,521
Depreciation and amortization	1,145	426	$ 330
Laboratory Equipment [Member]
Property and Equipment [Abstract]
Property and equipment, gross	7,807	1,910
Machinery and Equipment [Member]
Property and Equipment [Abstract]
Property and equipment, gross	9,933	0
Computer Equipment [Member]
Property and Equipment [Abstract]
Property and equipment, gross	218	179
Furniture and Fixtures [Member]
Property and Equipment [Abstract]
Property and equipment, gross	1,880	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	1,385	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	Dec. 31, 2020	Dec. 31, 2019
Accounts Payable and Accrued Expenses [Abstract]
Research and development	$ 14,962	$ 7,418
Property and equipment	1,456	4,424
Employee compensation	4,875	2,588
Accrued interest	1,122	1,241
Government grant payable	590	562
Professional fees	1,332	553
Internal use software	300	226
Other	835	340
Total	$ 25,472	$ 17,352

Convertible Notes Payable (Deta

Convertible Notes Payable (Details)	Jun. 12, 2020USD ($)	Feb. 20, 2020USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2020USD ($)d$ / shares	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Jan. 04, 2018USD ($)
Debt [Abstract]
Convertible notes refinancing costs to the lender				$ 237,000	$ 0	$ 0
Conversion of convertible notes into common stock				7,629,000	0	0
Carrying value of convertible notes [Abstract]
Carrying value			$ 35,066,000	35,066,000	45,049,000
Accretion of debt discount				$ 2,758,000	3,602,000	3,059,000
2021 Convertible Notes [Member]
Debt [Abstract]
Debt instrument maturity date				Aug. 1, 2021
Convertible senior notes, interest rate, stated percentage	6.25%		5.75%	5.75%
Debt conversion ratio				31.1876
Conversion per principal amount of debt			$ 1,000	$ 1,000
Convertible Note exchange	1
Conversion price (in dollars per share) | $ / shares			$ 32.08	$ 32.08
Percentage of common stock conversion price				200.00%
Number of trading days, not consecutive | d				20
Number of consecutive trading days | d				30
Number of trading days immediately preceding notice of redemption				5 days
Redemption price percentage				100.00%
Effective interest rate			15.30%	15.30%
Debt instrument, aggregate principal amount exchanged	$ 7,500,000	$ 39,350,000
Debt instrument, percentage of aggregate outstanding principal		76.00%
Accrued and unpaid interest	11,000	$ 100,000
Number of common stock shares repurchased (in shares) | shares		3,000
Aggregate amount of common stock shares repurchased		$ 72,000
Cost associated with exchange transactions	300,000	$ 1,600,000
Carrying value of convertible notes [Abstract]
Principal amount	7,500,000		$ 5,150,000	$ 5,150,000	52,000,000		$ 52,000,000
Discount			(275,000)	(275,000)	(6,951,000)
Carrying value			$ 4,875,000	4,875,000	45,049,000
Accretion of debt discount				$ 1,300,000	$ 3,600,000	$ 3,100,000
2022 Convertible Notes [Member]
Debt [Abstract]
Debt instrument maturity date				Aug. 31, 2022
Convertible senior notes, interest rate, stated percentage		6.25%	6.25%	6.25%
Debt conversion ratio		31.1876
Conversion per principal amount of debt		$ 1,000
Convertible Note exchange		1
Conversion price (in dollars per share) | $ / shares		$ 32.06
Percentage of common stock conversion price		130.00%
Number of trading days, not consecutive | d				20
Number of consecutive trading days | d				30
Number of trading days immediately preceding notice of redemption				5 days
Effective interest rate			15.30%	15.30%
Convertible notes refinancing costs to the lender	$ 100,000	$ 100,000
Conversion of convertible notes into common stock, principal amount			$ 8,500,000
Conversion of convertible notes into common stock			$ 7,600,000
Convertible Notes converted into shares of common stock (in shares) | shares			298,562
Carrying value of convertible notes [Abstract]
Principal amount		$ 39,350,000	$ 38,350,000	$ 38,350,000
Discount			(3,284,000)	(3,284,000)
Carrying value			$ 35,066,000	35,066,000
Accretion of debt discount				$ 1,500,000

Shareholders' Equity (Details)

Shareholders' Equity (Details) $ / shares in Units, $ in Thousands	Dec. 14, 2020USD ($)$ / sharesshares	Dec. 12, 2019USD ($)	Dec. 10, 2019USD ($)$ / sharesshares	Apr. 18, 2019USD ($)$ / sharesshares	Jan. 31, 2019USD ($)shares	Dec. 31, 2020USD ($)Vote$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)shares
Common Stock [Abstract]
Common stock, shares authorized (in shares) | shares						120,000,000	120,000,000
Common stock, par value (in dollars per share) | $ / shares						$ 0.01	$ 0.01
Number of voting right for each share | Vote						1
Treasury Stock [Abstract]
Retirement of treasury stock (in shares) | shares					100,000
Retirement of treasury stock					$ 1,300		$ 0
Shares withheld to pay the payroll tax liability						$ 614	344	$ 0
Public Offering [Abstract]
Net proceeds from offering						$ 280,763	$ 177,760	$ 154,022
Common Stock [Member]
Treasury Stock [Abstract]
Retirement of treasury stock (in shares) | shares							100,000
Retirement of treasury stock							$ 1
Public Offering [Abstract]
Common stock shares issued (in shares) | shares						5,339,286	9,568,000	11,475,242
Common Stock [Member] | Public Offering [Member]
Public Offering [Abstract]
Common stock shares issued (in shares) | shares	5,339,286		4,393,000	5,175,000		5,339,286
Share price (in dollars per share) | $ / shares	$ 56		$ 22.25	$ 17.50
Gross proceeds, offering amount	$ 299,000		$ 99,700	$ 90,600
Offering costs	18,200		6,100	4,500
Net proceeds from offering	$ 280,800		$ 91,700	$ 86,100
Common Stock [Member] | Exercise of Underwriters' Option [Member]
Public Offering [Abstract]
Common stock shares issued (in shares) | shares	696,428		573,000	675,000
Treasury Stock [Member]
Treasury Stock [Abstract]
Retirement of treasury stock							$ (1,393)
Shares withheld to pay the payroll tax liability		$ 100
Additional Paid-In Capital [Member]
Treasury Stock [Abstract]
Retirement of treasury stock							$ 1,392

Stock-Based Awards, Stock Optio

Stock-Based Awards, Stock Option Valuation (Details) - Stock Options [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Option Activity [Roll Forward]
Outstanding at beginning of period (in shares)	9,763,541	8,615,997
Granted (in shares)	2,193,546	1,706,116
Exercised (in shares)	(586,857)	(110,325)
Cancelled (in shares)	(319,299)	(448,247)
Outstanding at end of period (in shares)	11,050,931	9,763,541	8,615,997
Options vested and exercisable at end of period (in shares)	8,244,686
Options unvested at end of period (in shares)	2,806,245
Weighted Average Exercise Price [Abstract]
Outstanding at beginning of period (in dollars per share)	$ 5.95	$ 4.48
Granted (in dollars per share)	22.96	14.47
Exercised (in dollars per share)	4.82	2.31
Cancelled (in dollars per share)	15.82	10.83
Outstanding at end of period (in dollars per share)	9.10	$ 5.95	$ 4.48
Options vested and exercisable at end of period (in dollars per share)	4.98
Options unvested at end of period (in dollars per share)	$ 21.15
Weighted-Average Remaining Contractual Term [Abstract]
Outstanding	6 years 6 months 18 days	6 years 11 months 15 days	7 years 6 months 3 days
Granted	8 years 11 months 19 days	9 years 3 months 14 days
Options vested and exercisable	5 years 8 months 12 days
Options unvested	9 years 14 days
Aggregate Intrinsic Value [Abstract]
Outstanding at beginning of period	$ 164,021	$ 94,474
Exercised	13,494	1,429
Outstanding at end of period	504,079	$ 164,021	$ 94,474
Options vested and exercisable	$ 409,530
Weighted average grant date fair value of shares granted (in dollars per share)	$ 15.10	$ 9.58	$ 13.21
Total fair value of options vested	$ 15,600	$ 63,100
Employees and Directors [Member]
Fair Value Assumptions [Abstract]
Risk-free interest rate	1.00%	2.26%	2.64%
Expected term	5 years 10 months 2 days	5 years 9 months 21 days	5 years 10 months 6 days
Expected volatility	76.98%	75.71%	87.70%
Expected dividend yield	0.00%	0.00%	0.00%
Exercise price (in dollars per share)	$ 22.96	$ 14.47	$ 17.82
Fair value of common stock (in dollars per share)	$ 22.96	$ 14.47	$ 17.98

Stock-Based Awards, Stock-Based

Stock-Based Awards, Stock-Based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock-Based Compensation [Abstract]
Share based compensation expense	$ 18,567	$ 13,371	$ 13,601
Expense in connection with warrant issue	26,562	0	0
Unrecognized share-based compensation cost	$ 30,400
Weighted average period expected to recognize unrecognized share-based compensation cost	2 years 1 month 6 days
Research and Development [Member]
Stock-Based Compensation [Abstract]
Share based compensation expense	$ 7,355	6,153	7,375
General and Administrative [Member]
Stock-Based Compensation [Abstract]
Share based compensation expense	11,211	7,218	6,226
Common Stock Warrant [Member]
Stock-Based Compensation [Abstract]
Expense in connection with warrant issue	26,600
Stock Options [Member]
Stock-Based Compensation [Abstract]
Share based compensation expense	18,527	13,371	13,601
Restricted Stock Units [Member]
Stock-Based Compensation [Abstract]
Share based compensation expense	40	$ 0	$ 0
Unrecognized share-based compensation cost	$ 500
Weighted average period expected to recognize unrecognized share-based compensation cost	2 years 9 months 18 days

Stock-Based Awards, Restricted

Stock-Based Awards, Restricted Stock Units (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Weighted Average Grant Date Fair Value [Abstract]
Unrecognized share-based compensation cost	$ 30.4
Weighted average period expected to recognize unrecognized share-based compensation cost	2 years 1 month 6 days
Restricted Stock Units (RSU) [Member]
Number of Shares [Roll Forward]
Unvested, beginning balance (in shares)	0
Granted (in shares)	20,000
Unvested, ending balance (in shares)	20,000	0
Weighted Average Grant Date Fair Value [Abstract]
Unvested (in dollars per share)		$ 0
Granted (in dollars per share)	$ 25.06
Intrinsic value	$ 0.5	$ 0
Unrecognized share-based compensation cost	$ 0.5
Weighted average period expected to recognize unrecognized share-based compensation cost	2 years 9 months 18 days

Stock-Based Awards, Warrants (D

Stock-Based Awards, Warrants (Details)	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Warrants [Abstract]
Number of warrants exercised (in shares)	7,051
Common Stock [Member]
Warrants [Abstract]
Issuance of common stock pursuant to exercise of warrant (in shares)	1,601
Warrant One [Member]
Warrants [Abstract]
Warrants outstanding (in shares)	7,051
Exercise price of warrants (in dollars per share) | $ / shares	$ 24.82
Warrants expiry date	Jun. 28, 2023
Warrant Two [Member]
Warrants [Abstract]
Warrants outstanding (in shares)	603,386
Exercise price of warrants (in dollars per share) | $ / shares	$ 57.11
Warrants expiry date	Dec. 21, 2030

Net Loss Per Share (Details)

Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator [Abstract]
Net loss attributable to common stockholders									$ (139,700)	$ (77,270)	$ (74,518)
Denominator [Abstract]
Weighted-average common shares outstanding - basic and diluted (in shares)									55,380,740	49,010,358	39,377,666
Net loss per share attributable to common stockholders - basic and diluted (in dollars per share)	$ (1.09)	$ (0.53)	$ (0.45)	$ (0.45)	$ (0.39)	$ (0.38)	$ (0.38)	$ (0.43)	$ (2.52)	$ (1.58)	$ (1.89)
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Warrants exercisable for common shares									610,437	14,102	14,102
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements									11,050,931	9,608,537	8,615,997
Weighted Average Number Diluted Shares Outstanding									13,017,353	11,243,587	10,251,047
Convertible Notes 2021 [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Shares issuable upon conversion of Convertible Notes									160,536	1,620,948	1,620,948
Convertible Notes 2022 [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Shares issuable upon conversion of Convertible Notes									1,195,449	0	0

Income Taxes, Net Loss by Juris

Income Taxes, Net Loss by Jurisdiction (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Federal [Member]
Details of Income Taxes [Abstract]
Provision for income taxes	$ 0	$ 0	$ 0
State [Member]
Details of Income Taxes [Abstract]
Provision for income taxes	$ 0	$ 0	$ 0

Income Taxes, Reconciliation Be

Income Taxes, Reconciliation Between Effective Tax Rates and Statutory Rates (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Income Tax Benefit Computed at Statutory Federal Income Tax Rate to Income Taxes [Abstract]
U.S. federal tax at statutory rate	21.00%	21.00%	21.00%
Change in state tax apportionment	0.10%	(17.40%)	15.80%
Stock compensation	0.90%	(0.70%)	0.00%
Section 382 limitation	0.00%	0.00%	(38.70%)
Valuation allowance	(35.00%)	(5.10%)	3.50%
Tax credits	13.50%	0.00%	0.00%
Other	(0.50%)	2.10%	(1.60%)
Effective tax rate	0.00%	0.00%	0.00%

Income Taxes, Deferred Tax Asse

Income Taxes, Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred income tax assets (liabilities) [Abstract]
Net operating losses ("NOL")	$ 42,613	$ 18,471	$ 27,825
R&D Credits	21,359	2,517	575
Capitalized research and development costs	23,179	27,652	17,098
Other	1,189	643	1,385
Stock-based compensation	7,406	3,896	4,563
Debt discount	(748)	(1,460)	(3,652)
Warrants	5,585	0	0
Valuation allowance	(100,583)	(51,719)	(47,794)
Net deferred income tax asset	$ 0	$ 0	$ 0

Income Taxes, NOL Carryforwards

Income Taxes, NOL Carryforwards and Tax Credits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Abstract]
R&D Credits	$ 21,359	$ 2,517	$ 575
Increase in valuation allowance	48,900	3,900
Annual limitations under section 382 of IRC	1,700
Uncertain Tax Positions [Abstract]
Uncertain tax positions	0	0
Income Tax Penalties and Interest Accrued [Abstract]
Accrued interest or penalties	0	$ 0	$ 0
Income tax adjustments from prior periods	0
Federal [Member]
Operating Loss Carryforwards [Abstract]
NOL carryforwards	$ 194,300			$ 127,100
NOL carryforwards, expiration date	Dec. 31, 2025
Net operating loss not subject to expiration	$ 160,200
R&D Credits	$ 21,400
Tax credit, expiration date	Dec. 31, 2038
Net operating loss, subject to expiration	$ 34,100			$ 93,000
Cumulative limitation period	20 years
Federal [Member] | Research and Development [Member]
Tax Credit Carryforward [Abstract]
Tax credit carryforwards, subject to expiration	$ 4,900
State [Member]
Operating Loss Carryforwards [Abstract]
NOL carryforwards	$ 26,000
NOL carryforwards, expiration date	Dec. 31, 2035

Commitments and Contingencies_2

Commitments and Contingencies (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Operating lease, right-of-use assets	$ 914	$ 2,051
Operating lease, liability	$ 1,124
ASU 2016-02 [Member]
Leases [Abstract]
Operating lease, right-of-use assets			$ 2,600
Operating lease, liability			3,100
Reclassification of deferred rent to right-of-use assets			$ 500

Commitments and Contingencies,

Commitments and Contingencies, Finance Lease (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)ft²	Mar. 15, 2020USD ($)	Dec. 31, 2019USD ($)
Finance Lease [Abstract]
Finance lease, right-of-use assets	$ 50,521		$ 0
Finance lease, liability	20,632
Total lease payments	55,628
Cash security deposit	455		455
Restricted cash	1,568		1,525
Operating and Finance Leases [Member]
Finance Lease [Abstract]
Restricted cash	$ 1,100		1,000
NJ Lease Agreement [Member]
Finance Lease [Abstract]
Area of lease | ft²	103,720
Finance lease, right-of-use assets		$ 47,700
Finance lease, liability		20,200
Reclassification of construction costs in progress to right-of-use assets	$ 4,500	26,500
Reclassification of prepaid rent to right-of-use assets		$ 1,100
Aggregate amount for reclassification of construction costs in progress to right-of-use assets	32,100
Estimated rent payments	$ 1,200
Percentage of annual increase in base rent	3.00%
Total lease payments	$ 29,300
Term of finance lease agreement	15 years
Cash security deposit	$ 300		$ 300
AAV Current Good Manufacturing Practice (cGMP) [Member]
Finance Lease [Abstract]
Area of lease | ft²	50,000

Commitments and Contingencies_3

Commitments and Contingencies, Operating Leases (Details) - USD ($) $ in Millions	May 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jun. 07, 2018
Operating Leases [Abstract]
Rent expense		$ 1.1	$ 0.9	$ 0.8
NY Lease Agreement [Member]
Operating Leases [Abstract]
Lease expiration date		Jul. 31, 2022
Loss on lease termination	$ (76)
ESB Lease Agreement [Member]
Operating Leases [Abstract]
Lease expiration date		Jul. 31, 2021
Term of lease agreement		3 years
Letter of credit expiration date		Jun. 30, 2020
Letter of credit					$ 0.9
LOC automatic renewal period		1 year
Certificate of deposit		$ 0.9
Inotek Lexington Massachusetts Lease Agreement [Member]
Operating Leases [Abstract]
Lease expiration date		Feb. 28, 2023
Rental income received under sublease agreement		$ 0.4	$ 0.3	$ 0.1

Commitments and Contingencies_4

Commitments and Contingencies, Details of Operating and Finance Lease (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lease cost [Abstract]
Operating lease cost	$ 813
Finance lease cost [Abstract]
Amortization of right of use assets	1,711
Interest on lease liabilities	1,522
Total lease cost	4,046
Maturities of operating lease liabilities [Abstract]
2021	682
2022	445
2023	75
Total lease payments	1,202
Less: interest	(78)
Total operating lease liabilities	1,124
Maturity of finance lease liability [Abstract]
2021	1,644
2022	1,689
2023	1,736
2024	1,791
Thereafter	48,768
Total lease payments	55,628
Less: interest	(34,996)
Total finance lease liability	20,632
Lease assets and liabilities [Abstract]
Operating right-of-use assets	914	$ 2,051
Operating current lease liabilities	626	957
Operating noncurrent lease liabilities	498	1,443
Total operating lease liabilities	1,124
Finance lease, right-of-use assets	50,521	0
Finance current lease liability	1,644	0
Finance noncurrent lease liability	18,988	$ 0
Total finance lease liability	20,632
Cash paid for amounts included in the measurement of lease liabilities [Abstract]
Operating cash flows from operating leases	898
Cash flows from finance lease	$ 1,070
Weighted-average remaining lease term - operating leases	1 year 9 months 18 days
Weighted-average remaining lease term - finance lease	23 years 8 months 12 days
Weighted-average discount rate - operating leases	7.77%
Weighted-average discount rate - finance lease	8.96%

Agreements Related to Intelle_2

Agreements Related to Intellectual Property (Details) € in Thousands, $ in Thousands, $ / Vector in Millions	1 Months Ended				12 Months Ended
	Jan. 31, 2021	Feb. 28, 2017USD ($)	Aug. 31, 2016EUR (€)	Aug. 31, 2016USD ($)	Dec. 31, 2020USD ($)PatentMilestone$ / Vector	Aug. 31, 2016USD ($)
Contract Research and Collaboration Agreement with Lund University and J. Richter [Member]
License Agreement [Abstract]
Research and development costs			€ 20	$ 20
Term of agreement					24 months
Contract Research and Collaboration Agreement with Lund University and J. Richter [Member] | Maximum [Member]
License Agreement [Abstract]
Potential future obligation			€ 100			$ 100
Contract Research and Collaboration Agreement with Lund University and J. Richter [Member] | Subsequent Event [Member]
License Agreement [Abstract]
Agreement expiration date	Jul. 31, 2021
License Agreement for Danon Disease [Member]
License Agreement [Abstract]
Research and development costs		$ 50
License Agreement for Danon Disease [Member] | Maximum [Member]
License Agreement [Abstract]
Potential future obligation		$ 1,500
REGENXBIO, Inc. License [Member]
License Agreement [Abstract]
Research and development costs					$ 7,000
Potential future obligation					$ 13,000
Term of agreement					10 years
Termination notice period					6 months
Number of patents | Patent					2
Options right expiry term					4 years
Fee payable (per additional vector) | $ / Vector					2
Royalties payable on fees received					20.00%
Payment for License Fee					$ 1,000
Number of additional milestones achieved | Milestone					0

Strategic Research Collaborat_2

Strategic Research Collaboration (Details) - USD ($) $ in Millions	May 16, 2018	Jan. 31, 2019	Dec. 31, 2020
Collaboration Agreement [Abstract]
Funding in strategic research collaboration	$ 3.5
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) $ in Millions	Jan. 04, 2021USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2020USD ($)Grant	Nov. 12, 2020USD ($)	Apr. 30, 2019USD ($)
CIRM Grant [Abstract]
Grant award for clinical development support				$ 3.7	$ 6.5
Amount received from grant for eligible costs incurred		$ 1.2
Grant receivable included in prepaid and other assets			$ 1.1
Number of grants | Grant			2
Subsequent Event [Member]
CIRM Grant [Abstract]
Amount received from grant for eligible costs incurred	$ 1.1
Grant receivable included in prepaid and other assets	$ 0.9

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 21, 2020
Related Party Transaction [Abstract]
Termination notice period for business development consulting services agreement		60 days
Term of consulting agreement		3 years
Expense in connection with warrant issue		$ 26,562	$ 0	$ 0
Common Stock Warrant [Member]
Related Party Transaction [Abstract]
Expense in connection with warrant issue		$ 26,600
Fair Value Assumptions [Abstract]
Risk-free interest rate		0.95%
Expected term		10 years
Expected volatility		74.20%
Expected dividend yield		0.00%
Exercise price (in dollars per share)		$ 57.11
Fair value of common stock (in dollars per share)		$ 57.11
Restricted Stock Units (RSU) [Member]
Related Party Transaction [Abstract]
Shares granted (in shares)		20,000
Warrants Exercisable for Common Shares [Member]
Related Party Transaction [Abstract]
Warrant issued (in shares)					603,386
Member of the Board of Directors - One [Member]
Related Party Transaction [Abstract]
Business development consulting services expense (per quarter)		$ 28
Termination notice period for business development consulting services agreement		14 days
Related party expenses		$ 100	$ 100	$ 100
Member of the Board of Directors - Two [Member]
Related Party Transaction [Abstract]
Term of consulting agreement		1 year
Number of options granted (in shares)		9,784
Fair value amount of options granted		$ 100
Spouse of Executive officer [Member] | Restricted Stock Units (RSU) [Member]
Related Party Transaction [Abstract]
Shares granted (in shares)	10,000
Vesting period		3 years

401(k) Savings Plan (Details)

401(k) Savings Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
401(k) Savings Plan [Abstract]
Percentage of matching employee contributions	4.00%
Matching employee contributions	$ 0.3	$ 0.2	$ 0.1

Selected Quarterly Financial _3

Selected Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Selected Quarterly Financial Information (Unaudited) [Abstract]
Total Revenue	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Total operating expenses	59,237	27,387	23,559	24,120	19,649	19,165	18,392	18,945	134,303	76,151	71,156
Loss from operations	(59,237)	(27,387)	(23,559)	(24,120)	(19,649)	(19,165)	(18,392)	(18,945)	(134,303)	(76,151)	(71,156)
Net loss	$ (60,916)	$ (29,080)	$ (25,040)	$ (24,664)	$ (19,855)	$ (19,284)	$ (18,680)	$ (19,451)	$ (139,700)	$ (77,270)	$ (74,518)
Net loss per share attributable to common stockholders - basic and diluted (in dollars per share)	$ (1.09)	$ (0.53)	$ (0.45)	$ (0.45)	$ (0.39)	$ (0.38)	$ (0.38)	$ (0.43)	$ (2.52)	$ (1.58)	$ (1.89)