Tcr2 Therapeutics (TCRR) 10-Q 13 May 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 03, 2021
Cover [Abstract]
Entity Shell Company	false
Title of 12(b) Security	Common Stock, $0.0001 Par Value
City Area Code	617
Entity Address, Address Line One	100 Binney Street
Entity Incorporation, State or Country Code	DE
Entity File Number	001-38811
Document Transition Report	false
Document Quarterly Report	true
Entity Registrant Name	TCR2 Therapeutics Inc.
Entity Central Index Key	0001750019
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Document Type	10-Q
Amendment Flag	false
Entity Emerging Growth Company	true
Entity Small Business	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		38,162,452
Entity Tax Identification Number	47-4152751
Entity Address, Address Line Two	Suite 710
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
Local Phone Number	949-5200
Trading Symbol	TCRR
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes

Unaudited Consolidated Balance

Unaudited Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 218,276	$ 94,155
Investments	115,005	133,831
Prepaid expenses and other current assets	9,690	7,552
Total current assets	342,971	235,538
Property and equipment, net	51,842	10,013
Restricted cash	1,141	583
Deferred offering costs	225	61
Total assets	396,179	246,195
Liabilities and stockholders’ equity
Accounts payable	3,830	2,448
Accrued expenses and other current liabilities	4,577	6,392
Lease financing obligation	2,114
Total current liabilities	10,521	8,840
Lease financing obligation, excluding current portion	35,011
Other liabilities	892	807
Total liabilities	46,424	9,647
Commitments and contingencies (Note 7)
Stockholders’ equity
Preferred stock, $0.0001 par value; 10,000,000 shares authorized, no shares issued or outstanding as of March 31, 2021 and December 31, 2020, respectively.
Common stock, $0.0001 par value; 150,000,000 shares authorized; 38,159,202 and 24,050,936 shares issued; 38,159,202 and 23,981,109 shares outstanding as of March 31, 2021 and December 31, 2020, respectively.	4	3
Additional paid-in capital	621,022	486,197
Accumulated other comprehensive income	(44)	63
Accumulated deficit	(271,227)	(249,715)
Total stockholders’ equity	349,755	236,548
Total liabilities and stockholders’ equity	$ 396,179	$ 246,195

Unaudited Consolidated Balanc_2

Unaudited Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Preferred stock, par value (USD per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (shares)	10,000,000	10,000,000
Preferred stock, shares issued (shares)	0	0
Preferred stock, shares outstanding (shares)	0	0
Common stock, par value (USD per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (shares)	150,000,000	150,000,000
Common stock, shares issued (shares)	38,159,202	24,050,936
Common stock, shares outstanding (shares)	38,159,202	23,981,109

Unaudited Consolidated Statemen

Unaudited Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating expenses
Research and development	$ 15,924	$ 11,955
General and administrative	5,668	4,271
Total operating expenses	21,592	16,226
Loss from operations	(21,592)	(16,226)
Interest income, net	116	747
Loss before income tax expense	(21,476)	(15,479)
Income tax expense	36	27
Net loss	$ (21,512)	$ (15,506)
Per share information
Net loss per share of common stock, basic and diluted	$ (0.58)	$ (0.65)
Weighted average shares outstanding, basic and diluted	37,062,604	24,011,843

Unaudited Consolidated Statem_2

Unaudited Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (21,512)	$ (15,506)
Unrealized loss on investments, net	(107)	(604)
Comprehensive loss	$ (21,619)	$ (16,110)

Unaudited Consolidated Statem_3

Unaudited Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2019	$ 160,449	$ 2	$ 342,896	$ (182,591)	$ 142
Beginning balance (shares) at Dec. 31, 2019		23,981,109
Reclassification of shares issued and previously subject to repurchase	13		13
Reclassification of shares issued and previously subject to repurchase (shares)		17,456
Exercise of stock options	$ 185		185
Exercise of stock options (shares)	44,428	57,904
Stock-based compensation expense	$ 2,055		2,055
Unrealized loss on investments, net	(604)				(604)
Net loss	(15,506)			(15,506)
Ending balance at Mar. 31, 2020	146,592	$ 2	345,149	(198,097)	(462)
Ending balance (shares) at Mar. 31, 2020		24,056,469
Beginning balance at Dec. 31, 2020	$ 236,548	$ 3	486,197	(249,715)	63
Beginning balance (shares) at Dec. 31, 2020	23,981,109	33,516,795
Issuance of common stock, net of issuance costs	$ 131,330	$ 1	131,329
Issuance of common stock, net of issuance costs (shares)	0	4,590,164
Exercise of stock options	$ 376		376
Exercise of stock options (shares)	44,239	52,243
Stock-based compensation expense	$ 3,120		3,120
Unrealized loss on investments, net	(107)				(107)
Net loss	(21,512)			(21,512)
Ending balance at Mar. 31, 2021	$ 349,755	$ 4	$ 621,022	$ (271,227)	$ (44)
Ending balance (shares) at Mar. 31, 2021	38,159,202	38,159,202

Unaudited Consolidated Statem_4

Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities
Net loss	$ (21,512)	$ (15,506)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation and amortization	513	306
Stock-based compensation expense	3,120	2,055
Accretion on investments	164	(164)
Deferred tax liabilities	36	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,136)	(1,589)
Accounts payable	1,684	603
Accrued expenses and other liabilities	(1,767)	(2,115)
Cash used in operating activities	(19,898)	(16,410)
Investing activities
Purchases of equipment	(1,491)	(504)
Purchases of investments	(40,732)	(47,956)
Proceeds from sale or maturity of investments	59,287	30,617
Cash used in investing activities	17,064	(17,843)
Financing activities
Proceeds from public offering of common stock, net of issuance costs	131,330	0
Proceeds from the exercise of stock options	376	185
Payments on lease financing obligation	(4,029)	0
Deferred offering costs	(164)	(135)
Cash provided by financing activities	127,513	50
Net change in cash, cash equivalents, and restricted cash	124,679	(34,203)
Cash, cash equivalents, and restricted cash at beginning of year	94,738	65,713
Cash, cash equivalents, and restricted cash at end of period	219,417	31,510
Supplemental disclosure of noncash activities
Property and equipment additions in accounts payable	309	93
Assets acquired with lease finance obligation	$ 41,154	$ 0

Organization and Description of

Organization and Description of Business	3 Months Ended
	Mar. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Description of Business	1. Organization and Description of Business TCR 2 2 2 Shelf registration statement On March 16, 2021, the Company filed an automatic shelf registration statement on Form S-3 (the Shelf), with the Securities and Exchange Commission (SEC), which covers the offering, issuance and sale of an indeterminate amount Equity offering On July 31, 2020, the Company closed a public offering of its common stock pursuant to which it issued and sold 9,200,000 shares of its common stock at a price to the public of $15.50 per share. The aggregate net proceeds received by the Company from the offering were approximately $133.6 million after deducting $9.0 million relating to underwriting discounts and commissions and offering expenses. On January 22, 2021, the Company closed a public offering of its common stock pursuant to which it issued and sold 4,590,164 shares of its common stock at a price to the public of $30.50 per share. The aggregate net proceeds received by the Company from the offering were approximately $131.3 million after deducting $8.7 million relating to underwriting discounts and commissions and offering expenses.

Liquidity

Liquidity	3 Months Ended
	Mar. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Liquidity	2. Liquidity The Company’s operations to date have focused on organization and staffing, business planning, raising capital, acquiring technology and assets, manufacturing, conducting preclinical studies and clinical activities. The Company does not have any product candidates approved for sale and has not generated any revenue from product sales. The Company’s product candidates are subject to long development cycles and the Company may be unsuccessful in its efforts to develop, obtain regulatory approval for or market its product candidates. The Company is subject to a number of risks including, but not limited to, the need to obtain adequate additional funding for the ongoing and planned clinical development of its product candidates. Because of the numerous risks and uncertainties associated with pharmaceutical products and development, the Company is unable to accurately predict the timing or amount of funds required to complete development of its product candidates, and costs could exceed the Company’s expectations for a number of reasons, including reasons beyond the Company’s control. The Company is also subject to a number of other risks including possible failure of preclinical studies or clinical trials, the need to obtain marketing approval for its product candidates, the development of new technological innovations by competitors, the need to successfully commercialize and gain market acceptance of any of the Company’s products that are approved and uncertainty around intellectual property matters. If the Company does not successfully commercialize any of its products, it will be unable to generate product revenue or achieve profitability. The Company expects to continue to generate losses for the foreseeable future. The Company expects that its cash, cash equivalents and investments as of March 31, 2021 of $333.3 million will be sufficient to fund its operating expenses and capital expenditure requirements through at least 12 months from the date of issuance of these unaudited consolidated financial statements .

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	3. Summary of Significant Accounting Policies Principles of consolidation and basis of presentation The unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and in accordance with Article 10 of Regulation S-X of the SEC, and reflect the financial position, results of operations and cash flows of the Company's business. Accordingly, they do not include all of the disclosures required by U.S. GAAP for a complete set of annual audited financial statements. All significant intercompany accounts and transactions are eliminated in consolidation. The unaudited consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. The accompanying financial information should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company's Annual Report on Form 10-K filed with the SEC on March 16, 2021 for the year ended December 31, 2020 (the 2020 Form 10-K). In the opinion of the Company's management, all adjustments (consisting of normal and recurring adjustments) considered necessary for a fair statement of the results for the interim periods presented have been included. Use of estimates The preparation of the accompanying unaudited consolidated financial statements in conformity with U.S. 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 unaudited consolidated financial statements and reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these unaudited consolidated financial statements include, but are not limited to, the fair value of the royalty transfer agreement obligations, and the fair value of stock-based compensation awards granted under the Company’s equity-based compensation plans. Due to the uncertainty of factors surrounding the estimates or judgments used in the preparation of the unaudited consolidated financial statements, actual results may materially vary from these estimates. Estimates and assumptions are periodically reviewed and the effects of revisions are reflected in the consolidated financial statements in the period they are determined to be necessary. Concentrations of credit risk and of manufacturing risk Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash, cash equivalents and investments. The Company’s cash, cash equivalents and investments are held by financial institutions in the United States. Amounts on deposit may at times exceed federally insured limits. Management believes that the financial institutions are financially sound, and accordingly, minimal credit risk exists with respect to the financial institutions. As of March 31, 2021, the Company has manufacturing arrangements with vendors for the supply of materials for use in preclinical and clinical studies. If the Company were to experience any disruptions in the party’s ability or willingness to continue to provide manufacturing services, the Company may experience significant delays in its product development timelines and may incur substantial costs to secure alternative sources of manufacturing. Fair value of financial instruments As of March 31, 2021 and December 31, 2020, the Company’s financial instruments consist of money market funds, U.S. Treasury securities, and corporate bonds and are included in investments. The carrying value of investments is the estimated fair value. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Cash equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. As of March 31, 2021 and December 31, 2020, cash equivalents consisted of U.S treasuries, corporate bonds, and government-backed money market funds. Investments As of March 31, 2021, all investments were classified as available-for-sale and were carried at their estimated fair value. Unrealized gains and losses are recorded as a component of accumulated other comprehensive income (loss) until realized. The Company determines the appropriate classification of its investments in debt securities at the time of purchase and re-evaluates such determination at each balance sheet date. The Company periodically reviews its investments in debt securities for impairment and adjusts these investments to their fair value when a decline in market value is deemed to be other than temporary. If losses on these securities are considered to be other than temporary, the loss is recognized in earnings. The Company classifies its available-for-sale marketable securities as current or non-current based on each instrument’s underlying effective maturity date and for which the Company has the intent and ability to hold the investment for a period of greater than 12 months. Marketable securities with maturities of less than 12 months are classified as current and are included in investments in the consolidated balance sheets. Marketable securities with maturities greater than 12 months for which the Company has the intent and ability to hold the investment for greater than 12 months are classified as non-current and are included in investments, non-current in the consolidated balance sheets. Restricted cash Cash accounts that are restricted as to withdrawal or usage are presented as restricted cash. Restricted cash includes amounts held as a security deposit in the form of a letter of credit for the Company’s leased facilities. Construction in progress The Company currently applies build-to-suit accounting and is the deemed accounting owner of its leased site in Rockville, Maryland (Rockville). The Company establishes assets and liabilities for the estimated construction costs incurred under lease arrangements where it is considered the owner for accounting purposes only, to the extent it is involved in the construction of structural improvements or takes construction risk prior to commencement of a lease. Upon occupancy of facilities under build-to-suit leases, the Company assesses whether these arrangements qualify for sales recognition under the sale-leaseback accounting guidance under ASC 840, Leases. If the Company continues to be the deemed owner, for accounting purposes, the facilities are accounted for as financing obligations. Construction in progress also includes direct costs related to the construction of various property and equipment, including leasehold improvements. Such costs are not depreciated until the asset is completed and placed into service. Stock-based compensation The Company measures stock-based awards at grant-date fair value and records compensation expense on a straight-line basis over the requisite service period, which is generally the vesting period of the respective award. Generally, the Company issues awards with only service-based vesting conditions. The Company accounts for forfeitures as they occur. For stock-based awards granted to non-employees, compensation expense is recognized over the period during which services are rendered by such non-employees until completed. Stock-options exercised prior to vesting are subject to repurchase by the Company until vested at the lesser of the initial exercise price and the fair market value of the Company’s common stock at the time of repurchase. The proceeds from the shares subject to repurchase are classified as a liability and reclassified to equity as the shares vest. Estimating the fair value of stock options and warrants requires the input of subjective assumptions, including the expected life of the instrument and stock price volatility. The Company uses the Black-Scholes option pricing model to value its stock option awards and warrants. As a result, if factors change and management uses different assumptions, stock-based compensation expense could be materially different for future awards. The Company classifies stock-based compensation expense in its statements of operations in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified. Research and development expenses Research and development costs are expensed as incurred and consist primarily of funds paid for employee wages and funds paid to third parties for the provision of services for product candidate development, clinical and preclinical development and related supply and manufacturing costs, and regulatory compliance costs. At the end of the reporting period, the Company compares payments made to third party service providers to the estimated progress toward completion of the research or development objectives. Such estimates are subject to change as additional information becomes available. Depending on the timing of payments to the service providers and the progress that the Company estimates has been made as a result of the service provided, the Company may record net prepaid or accrued expense relating to these costs. Upfront milestone payments made to third parties who perform research and development services on the Company’s behalf are expensed as services are rendered. Income taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A reduction in the carrying value of the deferred tax assets is required when it is not more likely than not that such deferred tax assets are not realizable. Net loss per share Basic and diluted net loss per common share is determined by dividing net loss attributable to common stockholders by the weighted-average shares of common stock outstanding during the period. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive shares of common stock are not assumed to have been issued if their effect is anti-dilutive. Therefore, the weighted-average shares used to calculate both basic and diluted loss per share are the same. The following potentially dilutive securities, on an as converted basis, have been excluded from the computation of diluted weighted-average shares outstanding as of March 31, 2021 and 2020, as they would be antidilutive: As of March 31, 2021 2020 Stock options outstanding 5,084,972 4,149,748 Common stock warrants 203,676 203,676 Employee stock purchase plan 1,573 2,980 Total 5,290,221 4,356,404 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 (which excludes investments from owners). The Company’s only element of other comprehensive loss is unrealized gains and losses on investments. Reconciliation of cash, cash equivalents and restricted cash as presented in the statements of cash flows The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the unaudited consolidated balance sheets to the total of the same such amounts shown in the unaudited consolidated statements of cash flows for the three months ended March 31, 2021 and 2020. As of March 31, 2021 2020 Cash and cash equivalents $ 218,276 $ 31,093 Restricted cash 1,141 417 Cash, cash equivalents and restricted cash shown in the statements of cash flows $ 219,417 $ 31,510 JOBS Act accounting election The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the JOBS Act). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it is (i) no longer an emerging growth company or (ii) affirmatively and irrevocably opt out of the extended transition period provided in the JOBS Act. As a result, these consolidated financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates. Recently issued accounting pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) which will require lessees to record most operating leases on their balance sheets but recognize the expenses in the statements of operations in a manner similar to current practice. Under the new standard, lessees will be required to recognize a lease liability for the obligation to make lease payments, and an asset for the right to use the underlying asset for the lease term, for all leases with terms longer than 12 months. Leases will be classified as finance or operating, with classification affecting the pattern and classification of expense recognition in the statements of operations. Expenses related to operating leases will be recognized on a straight-line basis, while those determined to be financing leases will be recognized following a front-loaded expense profile, in which interest and amortization are presented separately in the statements of operations. The principal effect on the Company’s financial statements will be an increase in assets and liabilities. The standard will be effective for public business entities for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. For all other entities and emerging growth companies, the amendments are effective for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. The Company is currently evaluating its date of adoption of the new standard and is required to adopt no later than January 1, 2022. A modified retrospective transition approach is required, applying the new standard to all leases existing at the date of initial application. An entity may choose to apply the standard either (1) on the date of adoption, or effective date, or (2) the beginning of the earliest comparative period presented in its financial statements. The standard includes a number of practical expedients that the Company is evaluating and may elect to apply. Early adoption is permitted. The Company expects that the adoption of the new leasing standard will result in the recognition of material right-of-use assets and lease liabilities on the consolidated balance sheets but does not expect it to have a material impact on its results of operations or cash flows.

Investments and Fair Value Meas

Investments and Fair Value Measurements	3 Months Ended
	Mar. 31, 2021
Fair Value And Debt Securities Available For Sale [Abstract]
Investments and Fair Value Measurements	4. Investments and Fair Value Measurements As of March 31, 2021, investments were comprised of the following: Amortized Cost Unrealized Gains Unrealized Losses Fair Value Corporate bonds $ 49,064 $ - $ (56 ) $ 49,008 U.S. Treasury securities 65,985 12 - 65,997 Total $ 115,049 $ 12 $ (56 ) $ 115,005 As of December 31, 2020, investments were comprised of the following: Amortized Cost Unrealized Gains Unrealized Losses Fair Value Corporate bonds $ 34,801 $ 60 $ - $ 34,861 U.S. Treasury securities 98,967 3 - 98,970 Total $ 133,768 $ 63 $ - $ 133,831 The amortized cost and estimated fair value of marketable securities, by contractual maturity: March 31, 2021 Amortized Cost Fair Value Due within one year or less $ 115,049 $ 115,005 December 31, 2020 Amortized Cost Fair Value Due within one year or less $ 133,768 $ 133,831 The Company follows FASB’s accounting guidance on fair value measurements for financial assets and liabilities measured on a recurring basis. Fair value is defined as the price at which an asset could be exchanged in a current transaction between knowledgeable, willing parties. Where available, fair value is based on observable market prices, or parameters derived from such prices. Where observable prices or inputs are not available, valuation models are applied. This hierarchy requires the use of observable market data when available and to minimize the use of unobservable inputs when determining fair value. These valuation techniques involve some level of management estimation and judgment. The degree of management estimation and judgment is dependent on the price transparency for the instruments, or market, and the instruments’ complexity. The guidance requires fair value measurements to be classified and disclosed in one of the following three categories: Level 1—Quoted prices (unadjusted in active markets for identical assets or liabilities) Level 2—Inputs other than quoted prices in active markets that are observable either directly or indirectly Level 3—Unobservable inputs in which there is little or no market data, which require the Company to develop its own assumptions As of March 31, 2021, the Company has classified assets measured at fair value on a recurring basis as follows: Fair Value Measurement Based on Amortized Quoted Prices in Active Market Significant Other Observable Inputs Significant Unobservable Inputs Cost Fair Value (Level 1) (Level 2) (Level 3) Cash equivalents (1) $ 208,776 $ 208,776 $ 208,776 $ - $ - Corporate bonds 49,064 49,008 - 49,008 - U.S. Treasury securities 65,985 65,997 - 65,997 - Total $ 323,825 $ 323,781 $ 208,776 $ 115,005 $ - As of December 31, 2020, the Company has classified assets measured at fair value on a recurring basis as follows: Fair Value Measurement Based on Amortized Quoted Prices in Active Market Significant Other Observable Inputs Significant Unobservable Inputs Cost Fair Value (Level 1) (Level 2) (Level 3) Cash equivalents (1) $ 89,319 $ 89,319 $ 89,319 $ - $ - Corporate bonds 34,801 34,861 - 34,861 - U.S. Treasury securities 98,967 98,970 - 98,970 - Total $ 223,087 $ 223,150 $ 89,319 $ 133,831 $ - (1)

Property and Equipment

Property and Equipment	3 Months Ended
	Mar. 31, 2021
Property Plant And Equipment [Abstract]
Property and Equipment	5. Property and Equipment Property and equipment, net, consisted of: As of March 31, 2021 December 31, 2020 Laboratory equipment $ 9,718 $ 8,566 Computer hardware and equipment 109 109 Furniture and fixtures 432 432 Leasehold improvements 551 320 Assets not placed in service (1) 43,874 3,320 54,684 12,747 Less: accumulated depreciation (2,842 ) (2,734 ) $ 51,842 $ 10,013 (1) During the first quarter of 2021, the Company signed a lease for a manufacturing facility in Rockville, Maryland. The Company is deemed for accounting purposes to be the owner of the Rockville facility. Depreciation expense was $513 and $306 for the three months ended March 31, 2021 and 2020, respectively.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	3 Months Ended
	Mar. 31, 2021
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	6. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of: As of March 31, 2021 December 31, 2020 Employee compensation and related benefits $ 1,663 $ 3,808 Professional fees 439 224 Contract manufacturing organization fees 897 582 Contract research organization fees 913 487 University partnerships - 183 Property received not yet invoiced 216 385 Other 449 723 $ 4,577 $ 6,392

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Leases The Company recognizes rent expense on a straight-line basis over the lease period and has accrued for rent expense incurred but not yet paid. Landlord allowances for tenant improvements are deferred and recognized as a reduction to rent expense on a straight-line basis and over the remaining lease term. Corporate headquarters and lab facility, Cambridge, Massachusetts In March 2018, the Company entered into a lease for office and laboratory facilities that expires in July 2025. Under the terms of the lease, the Company placed a $290 letter of credit into a restricted cash account as security for the facility. Catapult manufacturing facility, Stevenage, United Kingdom In December 2018, the Company signed a collaboration agreement (the Collaboration Agreement) with Cell Therapy Catapult Limited (Catapult) to establish the Company's manufacturing process in Catapult’s GMP manufacturing facility in the United Kingdom. The initial term of the Collaboration Agreement is three years which began March 1, 2019. The Company can terminate the Collaboration Agreement earlier with 12 months’ notice and continued payment for contributions during the 12-month termination period. The Collaboration Agreement provides for Catapult to provide identified space, called a module. The agreement calls for the Company to pay certain amounts for use of the module, operating and overhead expenses. The Company has concluded that the Collaboration Agreement contains an embedded lease as the Company has the right to operate the module in a manner it determines. The Company also concluded that it is not the deemed accounting owner during modification of the module nor does the agreement represent a capital lease under ASC 840, “Leases”. As a result, the embedded lease portion of the Collaboration Agreement will be accounted for as an operating lease. The Company determined the amounts to be representative of rent to be £300 per year based on the relative selling prices of the services being provided. This amount will be amortized annually on a straight-line basis as rent expense over the term of the embedded lease, commencing March 1, 2019. Office space, Cambridge, Massachusetts In September 2019, the Company entered into a lease for office facilities that expires in August 2024. Under the terms of the lease, the Company placed a $127 letter of credit into a restricted cash account as security for the facility. Lab facility, Cambridge Massachusetts In November 2020, the Company entered into a lease for office and laboratory facilities that expires in December 2023. Under the terms of the lease, the Company placed $166 letter of credit into a restricted cash account as security for the facility. Manufacturing facility, Waltham, Massachusetts In November 2020, the Company entered into a manufacturing agreement with ElevateBio LLC (ElevateBio) which includes identified space dedicated to the Company. The Company has determined the agreement contains an embedded lease. The Company also concluded that it is not the deemed accounting owner during modification of the dedicated space nor does the agreement represent a capital lease under ASC 840, “Leases”. As a result, the embedded lease portion of the ElevateBio agreement will be accounted for as an operating lease. Rockville facility In March 2021, the Company entered into a lease for a new manufacturing facility. The landlord built an approximately 85,000 square foot rental building in Rockville, Maryland and leased the facility to the Company as a manufacturing facility for an initial term of 15 years through June 2036. The Company also has an option to extend the term of the lease for two consecutive terms of five years each. Because the Company is involved in the construction project and is responsible for paying a significant portion of the costs of normal finish work and structural elements of the facility, the Company is deemed for accounting purposes to be the owner of the building during the construction period under build to suit lease accounting guidance under ASC 840, Leases. Therefore, the Company recorded project construction costs during the construction period incurred by the landlord as a construction-in-progress asset and a related construction financing obligation on its consolidated balance sheets. The following table presents future minimum rent payments under non-cancellable operating leases with initial terms in excess of one year and future payments to be made related to the Rockville facility as of March 31, 2021: As of March 31, 2021 Operating Lease Obligations Rockville Facility Total 2021 $ 4,094 $ 1,397 $ 5,491 2022 4,144 3,386 7,530 2023 3,690 3,453 7,143 2024 2,538 3,813 6,351 2025 1,054 4,201 5,255 Thereafter - 52,471 52,471 Total minimum payments required $ 15,520 $ 68,721 $ 84,241 Rent expense was $1,285 and $875 for the three months ended March 31, 2021 and 2020, respectively. Litigation The Company is not currently party to any material legal proceedings. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses as incurred the costs related to such legal proceedings. Royalty transfer agreement In connection with the sale of Series A redeemable convertible preferred stock, certain investors are entitled to receive, in the aggregate, a royalty from the Company equal to one percent at the time of the Series A preferred stock financing. The Company has elected to account for this liability at fair value with changes recognized in the statements of operations . Given the early - stage nature of the underlying technology and inherent risks associated with obtaining regulatory approval and achieving commercialization, the Company ascribed no value to the royalty agreement at inception and as of March 31, 2021 and December 31, 2020 . The Company currently does not have any net sales or license income and as a result has paid no royalties under this obligation for the three months ended March 31, 2021 and 2020 nor has the Company accrued any liability as of March 31, 2021 or December 31, 2020 .

Common Stock and Preferred Stoc

Common Stock and Preferred Stock	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Common Stock and Preferred Stock	8. Common Stock and Preferred Stock Common stock Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Preferred stock The Board of Directors or any authorized committee thereof is expressly authorized, to the fullest extent permitted by law, to provide by resolution or resolutions for, out of the unissued shares of Undesignated Preferred Stock, the issuance of the shares of Undesignated Preferred Stock in one or more series of such stock, and by filing a certificate of designations pursuant to applicable law of the State of Delaware, to establish or change from time to time the number of shares of each such series, and to fix the designations, powers, including voting powers, full or limited, or no voting powers, preferences and the relative, participating, optional or other special rights of the shares of each series and any qualifications, limitations and restrictions thereof. As of March 31, 2021, there are no preferred shares issued.

Stock-based Compensation

Stock-based Compensation	3 Months Ended
	Mar. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	9. Stock-based Compensation In February 2019, the Company’s Board of Directors and stockholders approved the 2018 Stock Option and Incentive Plan (the 2018 Plan), which replaced the 2015 Stock Option and Grant Plan (the 2015 Plan). The shares under the 2015 Plan which were not issued were rolled into the 2018 Plan. The 2018 Plan provides for the grant of incentive stock options, nonstatutory stock options, restricted stock awards, restricted stock units, stock appreciation rights and other stock-based awards. The Company’s officers, employees, directors, and other key persons (including consultants) are eligible to receive awards under the 2018 Plan. The maximum number of authorized shares to be issued under the 2018 Plan is 7,394,606 shares of common stock. The number of shares of common stock reserved for issuance under the 2018 Plan shall be cumulatively increased on January 1, 2020 and each January 1 thereafter by 4% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year or a lesser number of shares determined by the Company's Board of Directors. The amount, terms of grants, and exercisability provisions are determined and set by the Compensation Committee of the Company’s Board of Directors. The term of the options may be up to 10 years, and options are exercisable in cash or as otherwise determined by the Board of Directors. As of March 31, 2021, there were 1,923,103 shares of common stock available for future issuance under the 2018 Plan. Generally, options and restricted stock awards vest over a four-year The Company recorded stock-based compensation expense in the following expense categories of its accompanying unaudited consolidated statements of operations for the three months ended March 31, 2021 and 2020: For the Three Months Ended March 31, 2021 2020 Research and development $ 1,380 $ 812 General and administrative 1,740 1,243 $ 3,120 $ 2,055 Stock options During the three months ended March 31, 2020, there were 42,180 grants of stock options, 45,313 options forfeited, and 44,428 options exercised, respectively. The following table summarizes the activity related to stock option grants to employees and non-employees for the three months ended March 31, 2021: Shares Weighted Average Exercise Price Per Share Weighted Average Remaining Contractual Life (in Years) Balance as of December 31, 2020 5,011,349 $ 14.99 8.4 Granted 137,868 23.68 Exercised (44,239 ) 5.79 Forfeited (20,006 ) 18.45 Balance as of March 31, 2021 5,084,972 $ 15.29 8.2 Exercisable as of March 31, 2021 2,153,958 $ 8.96 7.4 Vested and expected to vest as of March 31, 2021 5,084,972 15.29 As of March 31, 2021, there was $36.2 million The fair value of options is estimated using the Black-Scholes option pricing model, which takes into account inputs such as the exercise price, the value of the underlying common stock at the grant date, expected term, expected volatility, risk-free interest rate and dividend yield. The fair value of each grant of options for the three months ended March 31, 2021 and 2020 was determined using the methods and assumptions discussed below: ▪ The expected term of employee options is determined using the “simplified” method, as prescribed in the SEC Staff Accounting Bulletin (SAB) No. 107, whereby the expected life equals the arithmetic average of the vesting term and the original contractual term of the option due to the Company’s lack of sufficient historical data. The expected term of non-employee options is equal to the contractual term. ▪ The expected volatility was based on the historical stock volatility of several comparable publicly traded companies over a period of time equal to the expected term of the options, as we do not have sufficient trading history to use the volatility of our own common stock. ▪ The estimated annual dividend yield is 0% because the Company has not historically paid and does not expect for the foreseeable future to pay, a dividend on its common stock. ▪ The Company is traded on the Nasdaq Select Market. Fair value is determined by the stock price quoted on Nasdaq. The grant date fair value of all option grants was estimated at the time of grant using the Black-Scholes option-pricing model using the following weighted-average assumptions: For the Three Months Ended March 31, 2021 2020 Risk-free interest rate 1.0 % 0.7 % Expected term (in years) 6.0 6.1 Expected volatility 76.3 % 71.5 % Annual dividend yield 0 % 0 % Fair value of common stock $ 15.84 $ 5.92 Warrants As of March 31, 2021 and December 31, 2020, there were 203,676 warrants outstanding. During the three months ended March 31, 2021 and 2020, the Company granted no warrants, and there were no forfeitures or exercises. Employee stock purchase plan (ESPP) In February 2019, the Company’s Board of Directors adopted and the Company’s stockholders approved the 2018 Employee Stock Purchase Plan (2018 ESPP). The 2018 ESPP enables eligible employees to purchase shares of the Company's common stock at the end of each six-month During the three months ended March 31, 2021 and 2020, there were 8,004 shares and 13,476 shares issued under the 2018 ESPP, respectively.

Related party transactions

Related party transactions	3 Months Ended
	Mar. 31, 2021
Related Party Transactions [Abstract]
Related party transactions	10. Related party transactions Manufacturing agreement During November 2020, the Company entered into a manufacturing partnership with ElevateBio. Dr. Ansbert Gadicke is a member of the board of directors at the Company and ElevateBio. The agreement is to establish a manufacturing partnership with ElevateBio for production of the Company’s clinical trial products. During the three-months ended March 31, 2021, the Company has incurred $721 in expenses and has incurred additional costs of $108 for equipment owned by the Company for use by ElevateBio. Consulting arrangement On October 1, 2015, the Company entered into a consulting agreement with Dr. Patrick Baeuerle. Pursuant to the consulting agreement, Dr. Baeuerle agreed to perform such consulting, advisory and related services to and for the Company as may be reasonably requested. In exchange, the Company agreed to pay Dr. Baeuerle a consulting fee of €15 per month. On November 1, 2016, the Company amended the consulting agreement to revise Dr. Baeuerle’s consulting fee to be €3 per month. Dr. Baeuerle is also eligible for an annual bonus equal to 33% of the annual fees paid under the consulting agreement, subject to the discretion of the Company's Board of Directors based on Dr. Baeuerle’s performance and the Company's performance. The term of the agreement is one year, and automatically extends for additional one-year $18

Subsequent event

Subsequent event	3 Months Ended
	Mar. 31, 2021
Subsequent Events [Abstract]
Subsequent event	11. Subsequent event On March 6, 2020, the Company entered into an Open Market Sale Agreement SM 415(a)(4) Securities Act

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Principles of consolidation and basis of presentation	Principles of consolidation and basis of presentation The unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and in accordance with Article 10 of Regulation S-X of the SEC, and reflect the financial position, results of operations and cash flows of the Company's business. Accordingly, they do not include all of the disclosures required by U.S. GAAP for a complete set of annual audited financial statements. All significant intercompany accounts and transactions are eliminated in consolidation. The unaudited consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. The accompanying financial information should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company's Annual Report on Form 10-K filed with the SEC on March 16, 2021 for the year ended December 31, 2020 (the 2020 Form 10-K). In the opinion of the Company's management, all adjustments (consisting of normal and recurring adjustments) considered necessary for a fair statement of the results for the interim periods presented have been included.
Use of estimates	Use of estimates The preparation of the accompanying unaudited consolidated financial statements in conformity with U.S. 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 unaudited consolidated financial statements and reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these unaudited consolidated financial statements include, but are not limited to, the fair value of the royalty transfer agreement obligations, and the fair value of stock-based compensation awards granted under the Company’s equity-based compensation plans. Due to the uncertainty of factors surrounding the estimates or judgments used in the preparation of the unaudited consolidated financial statements, actual results may materially vary from these estimates. Estimates and assumptions are periodically reviewed and the effects of revisions are reflected in the consolidated financial statements in the period they are determined to be necessary.
Concentrations of credit risk and of manufacturing risk	Concentrations of credit risk and of manufacturing risk Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash, cash equivalents and investments. The Company’s cash, cash equivalents and investments are held by financial institutions in the United States. Amounts on deposit may at times exceed federally insured limits. Management believes that the financial institutions are financially sound, and accordingly, minimal credit risk exists with respect to the financial institutions. As of March 31, 2021, the Company has manufacturing arrangements with vendors for the supply of materials for use in preclinical and clinical studies. If the Company were to experience any disruptions in the party’s ability or willingness to continue to provide manufacturing services, the Company may experience significant delays in its product development timelines and may incur substantial costs to secure alternative sources of manufacturing.
Fair value of financial instruments	Fair value of financial instruments As of March 31, 2021 and December 31, 2020, the Company’s financial instruments consist of money market funds, U.S. Treasury securities, and corporate bonds and are included in investments. The carrying value of investments is the estimated fair value. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date.
Cash equivalents	Cash equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. As of March 31, 2021 and December 31, 2020, cash equivalents consisted of U.S treasuries, corporate bonds, and government-backed money market funds.
Investments	Investments As of March 31, 2021, all investments were classified as available-for-sale and were carried at their estimated fair value. Unrealized gains and losses are recorded as a component of accumulated other comprehensive income (loss) until realized. The Company determines the appropriate classification of its investments in debt securities at the time of purchase and re-evaluates such determination at each balance sheet date. The Company periodically reviews its investments in debt securities for impairment and adjusts these investments to their fair value when a decline in market value is deemed to be other than temporary. If losses on these securities are considered to be other than temporary, the loss is recognized in earnings. The Company classifies its available-for-sale marketable securities as current or non-current based on each instrument’s underlying effective maturity date and for which the Company has the intent and ability to hold the investment for a period of greater than 12 months. Marketable securities with maturities of less than 12 months are classified as current and are included in investments in the consolidated balance sheets. Marketable securities with maturities greater than 12 months for which the Company has the intent and ability to hold the investment for greater than 12 months are classified as non-current and are included in investments, non-current in the consolidated balance sheets.
Restricted cash	Restricted cash Cash accounts that are restricted as to withdrawal or usage are presented as restricted cash. Restricted cash includes amounts held as a security deposit in the form of a letter of credit for the Company’s leased facilities.
Construction in progress	Construction in progress The Company currently applies build-to-suit accounting and is the deemed accounting owner of its leased site in Rockville, Maryland (Rockville). The Company establishes assets and liabilities for the estimated construction costs incurred under lease arrangements where it is considered the owner for accounting purposes only, to the extent it is involved in the construction of structural improvements or takes construction risk prior to commencement of a lease. Upon occupancy of facilities under build-to-suit leases, the Company assesses whether these arrangements qualify for sales recognition under the sale-leaseback accounting guidance under ASC 840, Leases. If the Company continues to be the deemed owner, for accounting purposes, the facilities are accounted for as financing obligations. Construction in progress also includes direct costs related to the construction of various property and equipment, including leasehold improvements. Such costs are not depreciated until the asset is completed and placed into service.
Stock-based compensation	Stock-based compensation The Company measures stock-based awards at grant-date fair value and records compensation expense on a straight-line basis over the requisite service period, which is generally the vesting period of the respective award. Generally, the Company issues awards with only service-based vesting conditions. The Company accounts for forfeitures as they occur. For stock-based awards granted to non-employees, compensation expense is recognized over the period during which services are rendered by such non-employees until completed. Stock-options exercised prior to vesting are subject to repurchase by the Company until vested at the lesser of the initial exercise price and the fair market value of the Company’s common stock at the time of repurchase. The proceeds from the shares subject to repurchase are classified as a liability and reclassified to equity as the shares vest. Estimating the fair value of stock options and warrants requires the input of subjective assumptions, including the expected life of the instrument and stock price volatility. The Company uses the Black-Scholes option pricing model to value its stock option awards and warrants. As a result, if factors change and management uses different assumptions, stock-based compensation expense could be materially different for future awards. The Company classifies stock-based compensation expense in its statements of operations in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.
Research and development expenses	Research and development expenses Research and development costs are expensed as incurred and consist primarily of funds paid for employee wages and funds paid to third parties for the provision of services for product candidate development, clinical and preclinical development and related supply and manufacturing costs, and regulatory compliance costs. At the end of the reporting period, the Company compares payments made to third party service providers to the estimated progress toward completion of the research or development objectives. Such estimates are subject to change as additional information becomes available. Depending on the timing of payments to the service providers and the progress that the Company estimates has been made as a result of the service provided, the Company may record net prepaid or accrued expense relating to these costs. Upfront milestone payments made to third parties who perform research and development services on the Company’s behalf are expensed as services are rendered.
Income taxes	Income taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A reduction in the carrying value of the deferred tax assets is required when it is not more likely than not that such deferred tax assets are not realizable.
Net loss per share	Net loss per share Basic and diluted net loss per common share is determined by dividing net loss attributable to common stockholders by the weighted-average shares of common stock outstanding during the period. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive shares of common stock are not assumed to have been issued if their effect is anti-dilutive. Therefore, the weighted-average shares used to calculate both basic and diluted loss per share are the same. The following potentially dilutive securities, on an as converted basis, have been excluded from the computation of diluted weighted-average shares outstanding as of March 31, 2021 and 2020, as they would be antidilutive: As of March 31, 2021 2020 Stock options outstanding 5,084,972 4,149,748 Common stock warrants 203,676 203,676 Employee stock purchase plan 1,573 2,980 Total 5,290,221 4,356,404
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 (which excludes investments from owners). The Company’s only element of other comprehensive loss is unrealized gains and losses on investments.
Reconciliation of cash, cash equivalents and restricted cash as presented in the statements of cash flows	Reconciliation of cash, cash equivalents and restricted cash as presented in the statements of cash flows The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the unaudited consolidated balance sheets to the total of the same such amounts shown in the unaudited consolidated statements of cash flows for the three months ended March 31, 2021 and 2020. As of March 31, 2021 2020 Cash and cash equivalents $ 218,276 $ 31,093 Restricted cash 1,141 417 Cash, cash equivalents and restricted cash shown in the statements of cash flows $ 219,417 $ 31,510
JOBS Act accounting election	JOBS Act accounting election The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the JOBS Act). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it is (i) no longer an emerging growth company or (ii) affirmatively and irrevocably opt out of the extended transition period provided in the JOBS Act. As a result, these consolidated financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates.
Recently issued and adopted accounting pronouncements	Recently issued accounting pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) which will require lessees to record most operating leases on their balance sheets but recognize the expenses in the statements of operations in a manner similar to current practice. Under the new standard, lessees will be required to recognize a lease liability for the obligation to make lease payments, and an asset for the right to use the underlying asset for the lease term, for all leases with terms longer than 12 months. Leases will be classified as finance or operating, with classification affecting the pattern and classification of expense recognition in the statements of operations. Expenses related to operating leases will be recognized on a straight-line basis, while those determined to be financing leases will be recognized following a front-loaded expense profile, in which interest and amortization are presented separately in the statements of operations. The principal effect on the Company’s financial statements will be an increase in assets and liabilities. The standard will be effective for public business entities for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. For all other entities and emerging growth companies, the amendments are effective for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. The Company is currently evaluating its date of adoption of the new standard and is required to adopt no later than January 1, 2022. A modified retrospective transition approach is required, applying the new standard to all leases existing at the date of initial application. An entity may choose to apply the standard either (1) on the date of adoption, or effective date, or (2) the beginning of the earliest comparative period presented in its financial statements. The standard includes a number of practical expedients that the Company is evaluating and may elect to apply. Early adoption is permitted. The Company expects that the adoption of the new leasing standard will result in the recognition of material right-of-use assets and lease liabilities on the consolidated balance sheets but does not expect it to have a material impact on its results of operations or cash flows.
Fair value measurement	The Company follows FASB’s accounting guidance on fair value measurements for financial assets and liabilities measured on a recurring basis. Fair value is defined as the price at which an asset could be exchanged in a current transaction between knowledgeable, willing parties. Where available, fair value is based on observable market prices, or parameters derived from such prices. Where observable prices or inputs are not available, valuation models are applied. This hierarchy requires the use of observable market data when available and to minimize the use of unobservable inputs when determining fair value. These valuation techniques involve some level of management estimation and judgment. The degree of management estimation and judgment is dependent on the price transparency for the instruments, or market, and the instruments’ complexity. The guidance requires fair value measurements to be classified and disclosed in one of the following three categories: Level 1—Quoted prices (unadjusted in active markets for identical assets or liabilities) Level 2—Inputs other than quoted prices in active markets that are observable either directly or indirectly Level 3—Unobservable inputs in which there is little or no market data, which require the Company to develop its own assumptions

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Schedule of Dilutive Securities Not Included in Diluted Per Share Calculations	The following potentially dilutive securities, on an as converted basis, have been excluded from the computation of diluted weighted-average shares outstanding as of March 31, 2021 and 2020, as they would be antidilutive: As of March 31, 2021 2020 Stock options outstanding 5,084,972 4,149,748 Common stock warrants 203,676 203,676 Employee stock purchase plan 1,573 2,980 Total 5,290,221 4,356,404
Schedule of Restricted Cash and Cash Equivalents	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the unaudited consolidated balance sheets to the total of the same such amounts shown in the unaudited consolidated statements of cash flows for the three months ended March 31, 2021 and 2020. As of March 31, 2021 2020 Cash and cash equivalents $ 218,276 $ 31,093 Restricted cash 1,141 417 Cash, cash equivalents and restricted cash shown in the statements of cash flows $ 219,417 $ 31,510

Investments and Fair Value Me_2

Investments and Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value And Debt Securities Available For Sale [Abstract]
Summary of Amortized Cost and Fair Values of Investment Securities Available-for-sale	As of March 31, 2021, investments were comprised of the following: Amortized Cost Unrealized Gains Unrealized Losses Fair Value Corporate bonds $ 49,064 $ - $ (56 ) $ 49,008 U.S. Treasury securities 65,985 12 - 65,997 Total $ 115,049 $ 12 $ (56 ) $ 115,005 As of December 31, 2020, investments were comprised of the following: Amortized Cost Unrealized Gains Unrealized Losses Fair Value Corporate bonds $ 34,801 $ 60 $ - $ 34,861 U.S. Treasury securities 98,967 3 - 98,970 Total $ 133,768 $ 63 $ - $ 133,831
Summary of Maturities	The amortized cost and estimated fair value of marketable securities, by contractual maturity: March 31, 2021 Amortized Cost Fair Value Due within one year or less $ 115,049 $ 115,005 December 31, 2020 Amortized Cost Fair Value Due within one year or less $ 133,768 $ 133,831
Summary of Classified Assets Measured at Fair Value on a Recurred Basis	As of March 31, 2021, the Company has classified assets measured at fair value on a recurring basis as follows: Fair Value Measurement Based on Amortized Quoted Prices in Active Market Significant Other Observable Inputs Significant Unobservable Inputs Cost Fair Value (Level 1) (Level 2) (Level 3) Cash equivalents (1) $ 208,776 $ 208,776 $ 208,776 $ - $ - Corporate bonds 49,064 49,008 - 49,008 - U.S. Treasury securities 65,985 65,997 - 65,997 - Total $ 323,825 $ 323,781 $ 208,776 $ 115,005 $ - As of December 31, 2020, the Company has classified assets measured at fair value on a recurring basis as follows: Fair Value Measurement Based on Amortized Quoted Prices in Active Market Significant Other Observable Inputs Significant Unobservable Inputs Cost Fair Value (Level 1) (Level 2) (Level 3) Cash equivalents (1) $ 89,319 $ 89,319 $ 89,319 $ - $ - Corporate bonds 34,801 34,861 - 34,861 - U.S. Treasury securities 98,967 98,970 - 98,970 - Total $ 223,087 $ 223,150 $ 89,319 $ 133,831 $ - (1)

Property and Equipment (Tables)

Property and Equipment (Tables)	3 Months Ended
	Mar. 31, 2021
Property Plant And Equipment [Abstract]
Summary of Property and Equipment	Property and equipment, net, consisted of: As of March 31, 2021 December 31, 2020 Laboratory equipment $ 9,718 $ 8,566 Computer hardware and equipment 109 109 Furniture and fixtures 432 432 Leasehold improvements 551 320 Assets not placed in service (1) 43,874 3,320 54,684 12,747 Less: accumulated depreciation (2,842 ) (2,734 ) $ 51,842 $ 10,013 (1) During the first quarter of 2021, the Company signed a lease for a manufacturing facility in Rockville, Maryland. The Company is deemed for accounting purposes to be the owner of the Rockville facility.

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2021
Payables And Accruals [Abstract]
Summary of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of: As of March 31, 2021 December 31, 2020 Employee compensation and related benefits $ 1,663 $ 3,808 Professional fees 439 224 Contract manufacturing organization fees 897 582 Contract research organization fees 913 487 University partnerships - 183 Property received not yet invoiced 216 385 Other 449 723 $ 4,577 $ 6,392

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Rental Payments under Non-cancellable Operating Leases	The following table presents future minimum rent payments under non-cancellable operating leases with initial terms in excess of one year and future payments to be made related to the Rockville facility as of March 31, 2021: As of March 31, 2021 Operating Lease Obligations Rockville Facility Total 2021 $ 4,094 $ 1,397 $ 5,491 2022 4,144 3,386 7,530 2023 3,690 3,453 7,143 2024 2,538 3,813 6,351 2025 1,054 4,201 5,255 Thereafter - 52,471 52,471 Total minimum payments required $ 15,520 $ 68,721 $ 84,241

Stock-based Compensation (Table

Stock-based Compensation (Tables)	3 Months Ended
	Mar. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Stock-based Compensation Expense	The Company recorded stock-based compensation expense in the following expense categories of its accompanying unaudited consolidated statements of operations for the three months ended March 31, 2021 and 2020: For the Three Months Ended March 31, 2021 2020 Research and development $ 1,380 $ 812 General and administrative 1,740 1,243 $ 3,120 $ 2,055
Schedule of Stock Option Activity	The following table summarizes the activity related to stock option grants to employees and non-employees for the three months ended March 31, 2021: Shares Weighted Average Exercise Price Per Share Weighted Average Remaining Contractual Life (in Years) Balance as of December 31, 2020 5,011,349 $ 14.99 8.4 Granted 137,868 23.68 Exercised (44,239 ) 5.79 Forfeited (20,006 ) 18.45 Balance as of March 31, 2021 5,084,972 $ 15.29 8.2 Exercisable as of March 31, 2021 2,153,958 $ 8.96 7.4 Vested and expected to vest as of March 31, 2021 5,084,972 15.29
Schedule of Weighted-Average Assumptions	The grant date fair value of all option grants was estimated at the time of grant using the Black-Scholes option-pricing model using the following weighted-average assumptions: For the Three Months Ended March 31, 2021 2020 Risk-free interest rate 1.0 % 0.7 % Expected term (in years) 6.0 6.1 Expected volatility 76.3 % 71.5 % Annual dividend yield 0 % 0 % Fair value of common stock $ 15.84 $ 5.92

Organization and Description _2

Organization and Description of Business - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 22, 2021	Jul. 31, 2020	Mar. 31, 2021
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock, net of issuance costs (shares)			0
Equity Offering
Subsidiary Sale Of Stock [Line Items]
Shares sold during public offering (shares)	4,590,164	9,200,000
Share price (USD per share)	$ 30.50	$ 15.50
Proceeds from issuance of common stock after underwriting discounts and commissions and estimated offering expenses	$ 131.3	$ 133.6
Underwriting discounts, commissions and estimated offering expenses	$ 8.7	$ 9

Liquidity - Narrative (Details)

Liquidity - Narrative (Details)	Mar. 31, 2021USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Cash, cash equivalents and investments	$ 333,300

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Schedule of Dilutive Securities Not Included in Diluted Per Share Calculations (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	5,290,221	4,356,404
Stock options outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	5,084,972	4,149,748
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	203,676	203,676
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	1,573	2,980

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Reconciliation of Cash and Cash Equivalents and Restricted Cash as presented in the Statements of Cash Flows (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cash and cash equivalents	$ 218,276	$ 94,155	$ 31,093
Restricted cash	1,141	583	417
Cash, cash equivalents and restricted cash shown in the statements of cash flows	$ 219,417	$ 94,738	$ 31,510	$ 65,713

Investments and Fair Value Me_3

Investments and Fair Value Measurements - Summary of Amortized Cost and Fair Values of Investment Securities Available-for-sale (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 115,049	$ 133,768
Unrealized Gains	12	63
Unrealized Losses	(56)	0
Fair Value	115,005	133,831
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	49,064	34,801
Unrealized Gains	0	60
Unrealized Losses	(56)	0
Fair Value	49,008	34,861
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	65,985	98,967
Unrealized Gains	12	3
Unrealized Losses	0	0
Fair Value	$ 65,997	$ 98,970

Investments and Fair Value Me_4

Investments and Fair Value Measurements - Summary of Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Amortized Cost
Due within one year or less	$ 115,049	$ 133,768
Fair Value
Due within one year or less	$ 115,005	$ 133,831

Investments and Fair Value Me_5

Investments and Fair Value Measurements - Summary of Classified Assets Measured at Fair Value on a Recurred Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 218,276	$ 94,155	$ 31,093
Available-for-sale securities, amortized cost	115,049	133,768
Fair Value	115,005	133,831
Fair Value, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	208,776	89,319
Cash equivalents, fair value	208,776	89,319
Available-for-sale securities, amortized cost	323,825	223,087
Available-for-sale securities, fair value	323,781	223,150
Fair Value, Recurring | Fair Value, Inputs, Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value	208,776	89,319
Available-for-sale securities, fair value	208,776	89,319
Fair Value, Recurring | Fair Value, Inputs, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value	0	0
Available-for-sale securities, fair value	115,005	133,831
Fair Value, Recurring | Fair Value, Inputs, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value	0	0
Available-for-sale securities, fair value	0	0
Fair Value, Recurring | Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, amortized cost	49,064	34,801
Fair Value	49,008	34,861
Fair Value, Recurring | Corporate bonds | Fair Value, Inputs, Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Recurring | Corporate bonds | Fair Value, Inputs, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	49,008	34,861
Fair Value, Recurring | Corporate bonds | Fair Value, Inputs, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Recurring | U.S. Treasury securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, amortized cost	65,985	98,967
Fair Value	65,997	98,970
Fair Value, Recurring | U.S. Treasury securities | Fair Value, Inputs, Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Recurring | U.S. Treasury securities | Fair Value, Inputs, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	65,997	98,970
Fair Value, Recurring | U.S. Treasury securities | Fair Value, Inputs, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	$ 0	$ 0

Property and Equipment - Summar

Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 54,684	$ 12,747
Less: accumulated depreciation		(2,842)	(2,734)
Property and equipment, net		51,842	10,013
Laboratory equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross		9,718	8,566
Computer hardware and equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross		109	109
Furniture and fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross		432	432
Leasehold improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross		551	320
Assets Not Placed In Service
Property Plant And Equipment [Line Items]
Property and equipment, gross	[1]	$ 43,874	$ 3,320
[1]	During the first quarter of 2021, the Company signed a lease for a manufacturing facility in Rockville, Maryland. The Company is deemed for accounting purposes to be the owner of the Rockville facility.

Property and Equipment - Narrat

Property and Equipment - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Property Plant And Equipment [Abstract]
Depreciation expense	$ 513	$ 306

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Employee compensation and related benefits	$ 1,663	$ 3,808
Professional fees	439	224
Contract manufacturing organization fees	897	582
Contract research organization fees	913	487
University partnerships		183
Property received not yet invoiced	216	385
Other	449	723
Accrued expenses and other current liabilities	$ 4,577	$ 6,392

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) £ in Thousands	1 Months Ended					3 Months Ended		9 Months Ended	12 Months Ended
	Mar. 31, 2021USD ($)ft²	Nov. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2018	Mar. 31, 2018USD ($)	Mar. 31, 2021USD ($)ft²	Mar. 31, 2020USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2020USD ($)	Mar. 31, 2021GBP (£)ft²
Other Commitments [Line Items]
Lease facility expiration date		2023-12	2024-08		2025-07
Restricted cash		$ 166,000	$ 127,000		$ 290,000			$ 127,000
Initial term				3 years
Termination period notice requirement				12 months
Termination period				12 months
Operating lease liability per year | £										£ 300
Rent expense						$ 1,285,000	$ 875,000
Royalty payments, percentage of net sales						1.00%
Royalty payments, percentage of license income						1.00%
Royalty agreement value	$ 0					$ 0			$ 0
Royalties paid						0	$ 0	$ 0
Accrued liabilities	$ 0					0			0
Global Net Sales
Other Commitments [Line Items]
Revenue						0			0
Intellectual License Income
Other Commitments [Line Items]
Revenue						$ 0			$ 0
Rockville Facility
Other Commitments [Line Items]
Lease facility expiration date	2036-06
Area of building | ft²	85,000					85,000				85,000
Initial term	15 years					15 years				15 years
Lessee, Operating Lease, Existence of Option to Extend [true false]	true
Lessee, Operating Lease, Option to Extend	The Company also has an option to extend the term of the lease for two consecutive terms of five years each.

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Future Minimum Rental Payments under Non-cancellable Operating Leases (Details) $ in Thousands	Mar. 31, 2021USD ($)
Lessee Lease Description [Line Items]
2021	$ 5,491
2022	7,530
2023	7,143
2024	6,351
2025	5,255
Thereafter	52,471
Total minimum payments required	84,241
Operating Lease Obligations
Lessee Lease Description [Line Items]
2021	4,094
2022	4,144
2023	3,690
2024	2,538
2025	1,054
Total minimum payments required	15,520
Rockville Facility
Lessee Lease Description [Line Items]
2021	1,397
2022	3,386
2023	3,453
2024	3,813
2025	4,201
Thereafter	52,471
Total minimum payments required	$ 68,721

Common Stock and Preferred St_2

Common Stock and Preferred Stock - Narrative (Details)	Mar. 31, 2021vote
Equity [Abstract]
Votes per each common stock share	1

Stock-based Compensation - Narr

Stock-based Compensation - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended
	Feb. 28, 2019	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		4 years
Stock options granted (in shares)		137,868	42,180
Stock options forfeited (in shares)		20,006	45,313
Stock options exercised (in shares)		44,239	44,428
Unrecognized compensation costs		$ 36,200,000
Unrecognized compensation cost, period of recognition		3 years 1 month 6 days
Annual dividend yield		0.00%	0.00%
Employee stock purchase plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase price of common stock, percentage of fair market value	85.00%
Stock purchase offering period		6 months
Maximum stock purchase value per employee, percent of eligible compensation	15.00%
Maximum stock purchase value per employee	$ 25,000
ESPP shares issued (in shares)		8,004	13,476
Common stock warrants
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants outstanding (in shares)		203,676		203,676
Warrants granted (in shares)		0	0
Warrants forfeited (in shares)		0	0
Warrants exercised (in shares)		0	0
2018 Stock Option and Incentive Plan | Stock options outstanding
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized (in shares)		7,394,606
Shares available for issuance as a percentage of outstanding shares, maximum		4.00%
Term of options		10 years
2018 Stock Option and Incentive Plan | Employee stock purchase plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for issuance (in shares)		1,923,103

Stock-based Compensation - Stoc

Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 3,120	$ 2,055
Research and Development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	1,380	812
General and Administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 1,740	$ 1,243

Stock-based Compensation - St_2

Stock-based Compensation - Stock Option Activity (Details) - $ / shares	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding, beginning balance (in shares)	5,011,349
Options granted (in shares)	137,868	42,180
Options exercised (in shares)	(44,239)	(44,428)
Options forfeited (in shares)	(20,006)	(45,313)
Options outstanding, ending balance (in shares)	5,084,972		5,011,349
Options exercisable (in shares)	2,153,958
Options vested and expected to vest (in shares)	5,084,972
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Options outstanding, weighted average exercise price per share, beginning balance (in dollars per share)	$ 14.99
Options granted, weighted average exercise price per share (in dollars per share)	23.68
Options exercised, weighted average exercise price per share (in dollars per share)	5.79
Options forfeited, weighted average exercise price per share (in dollars per share)	18.45
Options outstanding, weighted average exercise price per share, ending balance (in dollars per share)	15.29		$ 14.99
Options exercisable, weighted average exercise price per share, ending balance (in dollars per share)	8.96
Options vested and expected to vest, weighted average exercise price per share, ending balance (in dollars per share)	$ 15.29
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options outstanding, weighted average remaining contractual life (in years)	8 years 2 months 12 days		8 years 4 months 24 days
Options exercisable, weighted average remaining contractual life (in years)	7 years 4 months 24 days

Stock-based Compensation - St_3

Stock-based Compensation - Stock Options Valuation Assumptions (Details) - $ / shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rate	1.00%	0.70%
Expected term (in years)	6 years	6 years 1 month 6 days
Expected volatility	76.30%	71.50%
Annual dividend yield	0.00%	0.00%
Fair value of common stock	$ 15.84	$ 5.92

Related party transactions - Na

Related party transactions - Narrative (Details) € in Thousands, $ in Thousands	Nov. 01, 2016EUR (€)	Oct. 01, 2015EUR (€)	Mar. 31, 2021USD ($)	Mar. 31, 2020USD ($)
MPM Capital | TCR2 Therapeutics Inc.
Related Party Transaction [Line Items]
Shareholder ownership, percentage			5.00%
Dr Ansbert Gadicke | Director | Elevate Bio
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions			$ 721
Related Party Transaction Expenses From Transactions With Related Party			108
Dr. Patrick Baeuerle | Director | Consulting Agreement, Monthly Fee
Related Party Transaction [Line Items]
Related party transaction, amount of transaction | €	€ 3	€ 15
Dr. Patrick Baeuerle | Director | Consulting Agreement
Related Party Transaction [Line Items]
Related party transaction, eligible bonus as percentage of annual fees		33.00%
Related party transaction, term of agreement		1 year
Related party transaction, term of agreement, extension option		1 year
Dr. Patrick Baeuerle | Director | Consulting Agreement, Fees
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions			$ 18	$ 18

Subsequent Event - Narrative (D

Subsequent Event - Narrative (Details)	1 Months Ended
	Apr. 30, 2021USD ($)
Sales Agreement | Subsequent Event | Maximum
Subsequent Event [Line Items]
offering price	$ 100,000,000