Werewolf Therapeutics (HOWL) 10-Q 12 Aug 21 2021 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2021	Aug. 06, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2021
Entity File Number	001-40366
Entity Registrant Name	WEREWOLF THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-3523180
Entity Address, Address Line One	1030 Massachusetts Avenue
Entity Address, Address Line Two	Suite 210
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02138
City Area Code	617
Local Phone Number	952‑0555(Former name, former address and former fiscal year, if changed since last report)
Entity Shell Company	false
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	HOWL
Security Exchange Name	NASDAQ
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		27,567,728
Entity Central Index Key	0001785530
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 183,233	$ 92,570
Prepaid expenses and other current assets	3,126	344
Total current assets	186,359	92,914
Property and equipment, net	689	651
Restricted cash	1,208	207
Operating lease right of use asset	2,135	2,471
Deferred financing costs	27	155
Total assets	190,418	96,398
Current liabilities:
Accounts payable	3,193	1,021
Accrued expenses and other current liabilities	3,456	3,586
Operating lease liability, current	721	677
Total current liabilities	7,370	5,284
Operating lease liability, net of current portion	1,492	1,864
Other liabilities	0	31
Total liabilities	8,862	7,179
Commitments and contingencies
Stockholders’ equity (deficit):
Preferred stock, $0.0001 par value, 5,000 shares and no shares authorized at June 30, 2021 and December 31, 2020, respectively; no shares issued or outstanding as of June 30, 2021 or December 31, 2020	0	0
Common stock, $0.0001 par value, 200,000 shares and 193,500 shares authorized as of June 30, 2021 and December 31, 2020, respectively; 27,568 and 1,746 shares issued as of June 30, 2021 and December 31, 2020, respectively; 27,134 and 1,184 shares outstanding as of June 30, 2021 and December 31, 2020, respectively	2	2
Additional paid-in capital	402,822	0
Accumulated deficit	(221,268)	(51,865)
Total stockholders’ equity (deficit)	181,556	(51,863)
Total liabilities, redeemable convertible preferred stock, and stockholders’ equity (deficit)	190,418	96,398
Series A Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	0	69,012
Series B Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	$ 0	$ 72,070

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Preferred stock par value (usd per share)	$ 0.0001	$ 0.0001
Preferred stock authorized (shares)	5,000,000	0
Preferred stock issued (shares)	0	0
Preferred stock outstanding (shares)	0	0
Common stock par value (usd per share)	$ 0.0001	$ 0.0001
Common stock authorized (shares)	200,000,000	193,500,000
Common stock issued (shares)	27,568,000	1,746,000
Common stock outstanding (shares)	27,134,000	1,184,000
Series A Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock par value (usd per share)	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock authorized (shares)	0	80,247,000
Redeemable convertible preferred stock issued (shares)	0	80,247,000
Redeemable convertible preferred stock outstanding (shares)	0	80,247,000
Redeemable convertible preferred stock liquidation preference		$ 69,012
Series B Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock par value (usd per share)	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock authorized (shares)	0	78,222,000
Redeemable convertible preferred stock issued (shares)	0	78,222,000
Redeemable convertible preferred stock outstanding (shares)	0	78,222,000
Redeemable convertible preferred stock liquidation preference		$ 72,070

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating expenses:
Research and development	$ 7,265	$ 3,780	$ 12,082	$ 6,543
General and administrative	3,691	1,285	6,326	2,416
Total operating expenses	10,956	5,065	18,408	8,959
Operating loss	(10,956)	(5,065)	(18,408)	(8,959)
Other income:
Change in fair value of preferred stock tranche liability	0	7,301	0	7,301
Interest income	51	24	84	91
Other expense	(16)	(3)	(32)	(3)
Total other income	35	7,322	52	7,389
Net (loss) income	(10,921)	2,257	(18,356)	(1,570)
Accretion of redeemable convertible preferred stock to redemption value	(56,926)	(31)	(151,942)	(31)
Net (loss) income attributable to common stockholders	(67,847)	2,226	(170,298)	(1,601)
Net (loss) income attributable to common stockholders	$ (67,847)	$ 2,226	$ (170,298)	$ (1,601)
Net (loss) income per share attributable to common stockholders, basic
Net (loss) income per share attributable to common stockholders, basic (usd per share)	$ (3.82)	$ 2.35	$ (17.86)	$ (1.80)
Net (loss) income per share attributable to common stockholders, diluted (usd per share)	$ (3.82)	$ 0.22	$ (17.86)	$ (1.80)
Weighted-average common shares outstanding, basic
Weighted average common shares outstanding, basic (shares)	17,750	947	9,535	891
Weighted average common shares outstanding, diluted (shares)	17,750	10,327	9,535	891

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders’ (Deficit) Equity (unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Redeemable Convertible Preferred StockSeries A Redeemable Convertible Preferred Stock	Redeemable Convertible Preferred StockSeries B Redeemable Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Redeemable convertible preferred stock outstanding, beginning balance (shares) at Dec. 31, 2019				48,675	0
Redeemable convertible preferred stock outstanding, beginning balance at Dec. 31, 2019				$ 34,073	$ 0
Redeemable convertible preferred stock outstanding, ending balance (shares) at Mar. 31, 2020				48,675	0
Redeemable convertible preferred stock outstanding, ending balance at Mar. 31, 2020				$ 34,073	$ 0
Stockholders' equity, beginning balance (shares) at Dec. 31, 2019						1,737
Stockholders' equity, beginning balance at Dec. 31, 2019	$ (24,304)					$ 2	$ 102	$ (24,408)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	57						57
Net loss	(3,827)							(3,827)
Stockholders' equity, ending balance (shares) at Mar. 31, 2020						1,737
Stockholders' equity, ending balance at Mar. 31, 2020	(28,074)					$ 2	159	(28,235)
Redeemable convertible preferred stock outstanding, beginning balance (shares) at Dec. 31, 2019				48,675	0
Redeemable convertible preferred stock outstanding, beginning balance at Dec. 31, 2019				$ 34,073	$ 0
Redeemable convertible preferred stock outstanding, ending balance (shares) at Jun. 30, 2020				80,246	0
Redeemable convertible preferred stock outstanding, ending balance at Jun. 30, 2020				$ 56,173	$ 0
Stockholders' equity, beginning balance (shares) at Dec. 31, 2019						1,737
Stockholders' equity, beginning balance at Dec. 31, 2019	(24,304)					$ 2	102	(24,408)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(1,570)
Stockholders' equity, ending balance (shares) at Jun. 30, 2020						1,737
Stockholders' equity, ending balance at Jun. 30, 2020	(25,627)					$ 2	349	(25,978)
Redeemable convertible preferred stock outstanding, beginning balance (shares) at Mar. 31, 2020				48,675	0
Redeemable convertible preferred stock outstanding, beginning balance at Mar. 31, 2020				$ 34,073	$ 0
Increase (Decrease) in Temporary Equity [Roll Forward]
Accretion of redeemable convertible preferred stock to redemption value				$ 31	$ 0
Issuance of Series A Preferred Stock, net of issuance costs (shares)				31,571
Issuance of Series A Preferred Stock, net of issuance costs of $31				$ 22,069
Redeemable convertible preferred stock outstanding, ending balance (shares) at Jun. 30, 2020				80,246	0
Redeemable convertible preferred stock outstanding, ending balance at Jun. 30, 2020				$ 56,173	$ 0
Stockholders' equity, beginning balance (shares) at Mar. 31, 2020						1,737
Stockholders' equity, beginning balance at Mar. 31, 2020	(28,074)					$ 2	159	(28,235)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	221						221
Accretion of redeemable convertible preferred stock to redemption value	(31)						(31)	0
Net loss	2,257							2,257
Stockholders' equity, ending balance (shares) at Jun. 30, 2020						1,737
Stockholders' equity, ending balance at Jun. 30, 2020	(25,627)					$ 2	349	(25,978)
Redeemable convertible preferred stock outstanding, beginning balance (shares) at Dec. 31, 2020		80,247	78,222	80,247	78,222
Redeemable convertible preferred stock outstanding, beginning balance at Dec. 31, 2020		$ 69,012	$ 72,070	$ 69,012	$ 72,070
Increase (Decrease) in Temporary Equity [Roll Forward]
Accretion of redeemable convertible preferred stock to redemption value				$ 49,753	$ 45,263
Redeemable convertible preferred stock outstanding, ending balance (shares) at Mar. 31, 2021				80,247	78,222
Redeemable convertible preferred stock outstanding, ending balance at Mar. 31, 2021				$ 118,765	$ 117,333
Stockholders' equity, beginning balance (shares) at Dec. 31, 2020						1,746
Stockholders' equity, beginning balance at Dec. 31, 2020	(51,863)					$ 2	0	(51,865)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	539						539
Exercise of common stock options (shares)						14
Exercise of common stock options	21						21
Accretion of redeemable convertible preferred stock to redemption value	(95,016)						(560)	(94,456)
Net loss	(7,435)							(7,435)
Stockholders' equity, ending balance (shares) at Mar. 31, 2021						1,760
Stockholders' equity, ending balance at Mar. 31, 2021	(153,754)					$ 2	0	(153,756)
Redeemable convertible preferred stock outstanding, beginning balance (shares) at Dec. 31, 2020		80,247	78,222	80,247	78,222
Redeemable convertible preferred stock outstanding, beginning balance at Dec. 31, 2020		$ 69,012	$ 72,070	$ 69,012	$ 72,070
Redeemable convertible preferred stock outstanding, ending balance (shares) at Jun. 30, 2021		0	0	0	0
Redeemable convertible preferred stock outstanding, ending balance at Jun. 30, 2021		$ 0	$ 0	$ 0	$ 0
Stockholders' equity, beginning balance (shares) at Dec. 31, 2020						1,746
Stockholders' equity, beginning balance at Dec. 31, 2020	$ (51,863)					$ 2	0	(51,865)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (shares)	42
Net loss	$ (18,356)
Stockholders' equity, ending balance (shares) at Jun. 30, 2021						27,568
Stockholders' equity, ending balance at Jun. 30, 2021	181,556					$ 2	402,822	(221,268)
Redeemable convertible preferred stock outstanding, beginning balance (shares) at Mar. 31, 2021				80,247	78,222
Redeemable convertible preferred stock outstanding, beginning balance at Mar. 31, 2021				$ 118,765	$ 117,333
Increase (Decrease) in Temporary Equity [Roll Forward]
Accretion of redeemable convertible preferred stock to redemption value				$ 29,619	$ 27,307
Redeemable convertible preferred stock outstanding, ending balance (shares) at Jun. 30, 2021		0	0	0	0
Redeemable convertible preferred stock outstanding, ending balance at Jun. 30, 2021		$ 0	$ 0	$ 0	$ 0
Stockholders' equity, beginning balance (shares) at Mar. 31, 2021						1,760
Stockholders' equity, beginning balance at Mar. 31, 2021	(153,754)					$ 2	0	(153,756)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	781						781
Exercise of common stock options (shares)						28
Exercise of common stock options	131						131
Accretion of redeemable convertible preferred stock to redemption value	(56,926)						(335)	(56,591)
Issuance of common stock from initial public offering, net of issuance costs (shares)						7,500
Issuance of common stock from initial public offering, net of issuance costs	109,221						109,221
Conversion of redeemable convertible preferred stock to common stock upon closing of initial public offering (shares)				80,247	78,222	18,280
Conversion of redeemable convertible preferred stock to common stock upon closing of initial public offering	293,024			$ 148,384	$ 144,640		293,024
Net loss	(10,921)							(10,921)
Stockholders' equity, ending balance (shares) at Jun. 30, 2021						27,568
Stockholders' equity, ending balance at Jun. 30, 2021	$ 181,556					$ 2	$ 402,822	$ (221,268)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders’ (Deficit) Equity (unaudited) (Parentheticals) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Statement of Stockholders' Equity [Abstract]
Issuance costs	$ 2,379	$ 31

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating activities:
Net loss	$ (18,356)	$ (1,570)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	1,320	278
Depreciation expense	101	65
Non-cash lease expense	336	308
Change in fair value of preferred stock tranche liability	0	(7,301)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(2,691)	55
Accounts payable	1,864	578
Accrued expenses and other current liabilities	(1)	128
Right of use assets and operating lease liability	(328)	(221)
Other liabilities	(31)	(14)
Net cash used in operating activities	(17,786)	(7,694)
Investing activities:
Purchases of property and equipment	(124)	(494)
Net cash used in investing activities	(124)	(494)
Financing activities:
Proceeds from issuance of Series A redeemable convertible preferred stock	0	22,100
Proceeds from initial public offering of common stock	111,600	0
Payment of equity issuance costs	(2,087)	(26)
Proceeds from stock option exercises	152	0
Net cash provided by financing activities	109,665	22,074
Net increase in cash and cash equivalents	91,755	13,886
Cash, cash equivalents and restricted cash—beginning of period	92,777	18,104
Cash, cash equivalents and restricted cash—end of period	184,532	31,990
Non-cash investing and financing activities:
Non-cash accretion of Series A and Series B redeemable convertible preferred stock	151,942	31
Issuance costs in accounts payable and accrued expenses	318	59
Purchases of property and equipment in accounts payable and accrued expenses	$ 15	$ 26

Description of Business, Organi

Description of Business, Organization, and Liquidity	6 Months Ended
	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business, Organization, and Liquidity	Description of Business, Organization, and Liquidity Werewolf Therapeutics, Inc. (“Werewolf” or the “Company”) was incorporated in the state of Delaware in October 2017. The Company is an innovative biopharmaceutical company pioneering the development of therapeutics engineered to stimulate the body’s immune system for the treatment of cancer. The Company’s headquarters are located in Cambridge, Massachusetts. Since inception, the Company has devoted substantially all of its time and efforts to performing research and development activities, raising capital and recruiting management and technical staff to support these operations. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry including, but not limited to, technical risks associated with the successful research, development and manufacturing of product candidates, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Current and future programs will require significant 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 and infrastructure. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. On May 4, 2021, the Company closed its initial public offering (“IPO”) of 7,500,000 shares of the Company’s common stock at a public offering price of $16.00 per share. The gross proceeds from the IPO were $120.0 million and the net proceeds were approximately $109.2 million, after deducting underwriting discounts and commissions and other offering expenses payable by the Company. Upon completion of the Company’s IPO, all of the Company’s then outstanding preferred stock was automatically converted into an aggregate of 18,279,712 shares of common stock. The Company had cash and cash equivalents of $183.2 million at June 30, 2021. The Company expects that its cash and cash equivalents will enable it to fund its operating expenses and capital expenditure requirements for at least twelve months from the filing date of this Quarterly Report on Form 10-Q. However, additional funding will be necessary beyond this point to fund future preclinical and clinical activities. The Company expects to finance its future cash needs through a combination of equity or debt financings, collaboration agreements, strategic alliances and licensing arrangements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying condensed consolidated financial statements as of June 30, 2021, and for the three and six months ended June 30, 2021 and 2020, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and generally accepted accounting principles in the United States of America (“GAAP”) as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”) for condensed consolidated financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these condensed consolidated financial statements reflect all normal recurring adjustments which are necessary for a fair presentation of the Company’s financial position and results of its operations, as of and for the periods presented. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s final prospectus for its IPO dated April 29, 2021 and filed with the SEC pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended (the “Prospectus”). The information presented in the condensed consolidated financial statements and related notes as of June 30, 2021, and for the three and six months ended June 30, 2021 and 2020, is unaudited. The December 31, 2020 condensed consolidated balance sheet included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including notes, required by GAAP for complete financial statements. Interim results for the three and six months ended June 30, 2021 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2021, or any future period. The accompanying condensed consolidated financial statements include the accounts of Werewolf Therapeutics, Inc. and its wholly-owned subsidiary, Werewolf Therapeutics Mass Securities, Inc. All intercompany transactions and balances have been eliminated in consolidation. Summary of Significant Accounting Policies The significant accounting policies and estimates used in the preparation of the condensed consolidated financial statements are described in the Company’s audited financial statements for the year ended December 31, 2020, and the notes thereto, which are included in the Prospectus. There have been no material changes in the Company’s significant accounting policies during the six months ended June 30, 2021. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates which include, but are not limited to, the fair values of common stock and redeemable convertible preferred stock, the fair value of the warrant liabilities, and the fair value of the preferred stock tranche rights. Actual results could differ from those estimates. Recent Accounting Pronouncements In October 2020, the FASB issued ASU 2020-10, Codification Improvements , which updates various codification topics by clarifying or improving disclosure requirements to align with the SEC’s regulations. The Company adopted ASU 2020-10 as of the reporting period beginning January 1, 2021 and the adoption did not have material impact on the Company’s condensed consolidated balance sheets, condensed consolidated statements of operations or related disclosures. In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments . This guidance amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses for most financial assets and certain other instruments that aren’t measured at fair value through net income. The Company has adopted the new guidance effective January 1, 2021 and the adoption did not have any material impact on the Company’s condensed consolidated balance sheets, condensed consolidated statements of operations or related disclosures.

Financial Instruments and Fair

Financial Instruments and Fair Value Measurements	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Financial Instruments and Fair Value Measurements	Financial Instruments and Fair Value Measurements Fair value is an exit price, representing the amount that would be received from the sale of an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value is determined based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs reflect certain market assumptions. As a basis for considering such assumptions, GAAP establishes a three-tier value hierarchy, which prioritizes the inputs used to develop the assumptions and for measuring fair value as follows: (Level 1) observable inputs such as quoted prices in active markets for identical assets; (Level 2) inputs other than the quoted prices in active markets that are observable either directly or indirectly; and (Level 3) unobservable inputs in which there is little or no market data, which requires the Company to develop its own assumptions. This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value. The Company measures the fair value of money market funds based on quoted prices in active markets for identical securities. The carrying amounts reflected in the condensed consolidated balance sheets for cash, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values, due to their short-term nature. Assets measured at fair value on a recurring basis as of June 30, 2021 were as follows (in thousands): Quoted Price in Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Assets: Money market funds $ 183,233 $ — $ — $ 183,233 Total assets $ 183,233 $ — $ — $ 183,233 Assets measured at fair value on a recurring basis as of December 31, 2020 were as follows (in thousands): Quoted Price in Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Assets: Money market funds $ 92,570 $ — $ — $ 92,570 Total assets $ 92,570 $ — $ — $ 92,570 There were no changes in valuation techniques during the three or six months ended June 30, 2021. There were no liabilities measured at fair value on a recurring basis as of June 30, 2021 or December 31, 2020. Preferred Stock Tranche Liability — During 2019, the Company issued 48,675,140 shares of Series A redeemable convertible preferred stock (“Series A Preferred Stock”) which contained the preferred stock tranche liability. The fair value of the preferred stock tranche liability was $7.8 million upon issuance and was remeasured to $7.3 million as of December 31, 2019. The preferred stock tranche liability was settled in June 2020 upon the closing of the second tranche of the Series A Preferred Stock.

Restricted Cash

Restricted Cash	6 Months Ended
	Jun. 30, 2021
Cash and Cash Equivalents [Abstract]
Restricted Cash	Restricted CashThe Company maintained restricted cash of $1.3 million and $0.2 million at June 30, 2021 and December 31, 2020, respectively. At June 30, 2021, $0.1 million of the Company’s restricted cash balance is included within “Prepaid expenses and other current assets” in the accompanying condensed consolidated balance sheets. These amounts are comprised solely of letters of credit required pursuant to the Company’s leased office spaces.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	6 Months Ended
	Jun. 30, 2021
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities as of June 30, 2021 and December 31, 2020 were comprised as follows (in thousands): June 30, December 31, Manufacturing $ 1,375 $ 1,741 Employee compensation and benefits 1,000 990 Professional fees 416 654 Contract research 635 107 Other 30 94 Total accrued expenses and other current liabilities $ 3,456 $ 3,586

Term Loan

Term Loan	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Term Loan	Term Loan In May 2020, the Company entered into a Loan and Security Agreement (the “Loan Agreement”) with Pacific Western Bank (“PWB”). Under the terms of the Loan Agreement, PWB made available a term loan up to $6.0 million (“Term Loan A”). Based on the satisfaction of certain conditions defined in the Loan Agreement, PWB is also obligated to make available an additional term loan in the amount of up to $8.0 million until November 29, 2021 (“Term Loan B”, or collectively with Term Loan A, the “Term Loans”). The Company satisfied the conditions to draw Term Loan B in June 2020. Although Term Loan A was made available to the Company at the closing date, the Company elected to forgo making a draw, thereby incurring a delayed draw fee of $25,000 with PWB. As of June 30, 2021, the Company had not drawn down any Term Loans and had no outstanding borrowings under the Loan Agreement. The Term Loans will bear interest on the outstanding daily balance at a floating annual rate equal to greater of: (i) 1.75% above the prime rate then in effect or (ii) 5.00%. If the prime rate changes throughout the term, the interest rate will be adjusted effective on the date of the prime rate change. All interest chargeable under the Loan Agreement is computed on a 360-day year for the actual number of days elapsed, with interest payable monthly. The Company is obligated to pay PWB a fee of 5.00% of the amount drawn under the Term Loans upon the occurrence of the Company achieving certain conditions defined in the Loan Agreement (the “Success Fee”). The Success Fee will survive ten years from the date of payment of the Term Loan in full, such that, if the Loan Agreement is terminated prior to the payment of the Success Fee, the Company will remain obligated to pay the Success Fee upon the occurrence of a Success Fee Event (as described in the Loan Agreement). The Company determined that the Success Fee constitutes a freestanding financial instrument and should be accounted for as a liability in connection with ASC 480— Distinguishing Liabilities from Equity. The Company determined that the fair value of the Success Fee was immaterial at both issuance and as of June 30, 2021. Borrowings under the Loan Agreement are secured by the Company’s personal property (exclusive of any intellectual property) and are subject to acceleration in the event of default. In the event of a late payment or default, the Company is obligated to pay a fee equal to 5.0% of such unpaid amounts. In connection with the Loan Agreement, the Company is required to comply with certain covenants, which among other things, restrict the Company from (i) effectuating a merger or consolidation with or into any other business organization, (ii) paying dividends or making certain other distributions and (iii) making investments in any entities or instruments other than certain investments specified in the Loan Agreement. In addition, the Loan Agreement contains standard affirmative covenants, including with respect to the issuance of audited consolidated financial statements, insurance, and maintenance of good standing and government compliance in the Company’s state of formation. The Company is also required to maintain unrestricted cash balances of at least 2.5 times its monthly cash burn, and has covenanted not to make any capital expenditures in excess of $0.4 million in the aggregate in any fiscal year without the prior written consent of PWB. In December 2020, the Loan Agreement was amended to allow the Company to make investments in its subsidiary, Werewolf Therapeutics Mass Securities, Inc., subject to certain conditions described in the Loan Agreement. In February 2021, the Loan Agreement was amended such that the Company may not make any capital expenditures in excess of $2.0 million in the aggregate in 2021 and $0.5 million in the aggregate in any fiscal year thereafter without the prior written consent of PWB.

Common and Preferred Stock

Common and Preferred Stock	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Common and Preferred Stock	Common and Preferred Stock Common Stock The Company is authorized to issue 200.0 million shares of common stock. Common stockholders are entitled to dividends if and when declared by the Company’s board of directors. As of June 30, 2021, no dividends on common stock had been declared by the Company. The Company had reserved shares of common stock for issuance as follows (in thousands): As of June 30, As of December 31, 2021 2020 Redeemable convertible preferred stock outstanding — 18,280 Options issued and outstanding 2,884 2,059 Warrants issued and outstanding 59 59 Total 2,943 20,398 Redeemable Convertible Preferred Stock The Company’s Series A and Series B redeemable convertible preferred stock, together referred to as “Preferred Stock,” was classified as temporary equity on the accompanying condensed consolidated balance sheets in accordance with authoritative guidance for the classification and measurement of redeemable securities as the preferred stock was redeemable upon the occurrence of a deemed liquidation event. Upon completion of the Company’s IPO, all of the Company’s then outstanding preferred stock was automatically converted into an aggregate of 18.3 million shares of common stock. Series A Preferred Stock The Series A Preferred Stock shares were issued at various closing dates between 2019 and 2020 for a purchase price of $0.70 per share. The shares were issued in exchange for cash proceeds of $44.0 million, net of issuance costs of $0.2 million, and the exchange of approximately $12.0 million in outstanding convertible notes, including accrued interest. Tranche Rights Issued with Series A Preferred Stock Included in the terms of the Series A Preferred Stock purchase agreement (the “Series A Stock Purchase Agreement”) were certain tranche rights (the “Tranche Rights”). The Tranche Rights obligated the Series A Preferred Stock investors to purchase, and the Company to sell, an additional 31,571,425 shares of Series A Preferred Stock for a purchase price of $0.70 per share (the “Second Closing”) on November 1, 2020 or based on the election of each investor prior to the Second Closing. On May 12, 2020, the Series A Stock Purchase Agreement was amended such that the Second Closing would occur on June 1, 2020 or on an earlier date at the election of each investor. The Company concluded that the Tranche Rights met the definition of a freestanding financial instrument, as the Tranche Rights were legally detachable and separately exercisable from the Series A Preferred Stock. Therefore, the Company allocated the net proceeds between the Tranche Rights and the Series A Preferred Stock. The trigger for the Second Closing was based on the passage of time or the election of the holders of Series A Preferred Stock. Based on the contractual terms, and the fact that the issuance was based on an event that was not within the control of the Company (i.e., written consent or passage of time), the Tranche Rights imposed an obligation on the Company to issue shares. Since the Series A Preferred Stock was contingently redeemable, the Tranche Rights were classified as a liability under ASC 480, Distinguishing Liabilities from Equity , and were initially recorded at fair value. The Tranche Rights were measured at fair value at each reporting period. Since the Tranche Rights were subject to fair value accounting, the Company allocated the proceeds to the Tranche Rights based on the fair value at the date of issuance with the remaining proceeds being allocated to the Series A Preferred Stock. The estimated fair value of the Tranche Rights was determined using a probability-weighted present value model that considered the probability of closing a tranche, the estimated future value of Series A redeemable convertible preferred stock at each closing and the investment required at each closing. Future values were converted to present value using a discount rate appropriate for probability-adjusted cash flows. The Tranche Rights were initially recorded as a liability of $7.8 million. The Company remeasured the liability on each subsequent balance sheet date and prior to settlement and issuance of shares in connection with the Second Closing, which occurred on June 1, 2020. Series B Preferred Stock The Series B Preferred Stock shares were issued for a purchase price of $0.92 per share. The issuance resulted in cash proceeds of $71.8 million, net of issuance costs of $0.3 million. Redemption: Upon certain change in control events that are outside of the Company’s control, including liquidation, sale or transfer of control of the Company, the Preferred Stock was contingently redeemable. In addition, the Preferred Stock was redeemable at any time on or after the fifth anniversary of the original issue date. The Preferred Stock was redeemable at a price equal to the greater of (i) the original issue price of $0.70 per share for Series A Preferred stock and the original issue price of $0.92 per share for Series B Preferred Stock, respectively, or (ii) the fair market value of the Series A Preferred Stock and Series B Preferred Stock, as applicable, as of the redemption request date. As the Preferred Stock approached becoming redeemable due to the passage of time, the Company recorded changes in the redemption value and accreted the Preferred Stock immediately to redemption value as it occurred. Preferred Stock The Company is authorized to issue 5.0 million shares of undesignated preferred stock in one or more series. As of June 30, 2021, no shares of preferred stock were issued or outstanding.

Stock-based Compensation

Stock-based Compensation	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Stock-based Compensation	Stock-based Compensation 2017 Stock Incentive Plan In December 2017, the Company adopted the 2017 Stock Incentive Plan (the “2017 Plan”), as amended and restated, under which it could grant incentive stock options (“ISOs”), non-qualified stock options, restricted stock awards (“RSAs”), restricted stock units (“RSUs”), stock appreciation rights and other stock-based awards to eligible employees, officers, directors and consultants. The terms of stock options and restricted stock awards, including vesting requirements, are determined by the board of directors, subject to the provisions of the Plan. 2021 Stock Incentive Plan In April 2021, the board of directors adopted and the Company’s stockholders approved the 2021 Stock Incentive Plan (the “2021 Plan”), which became effective immediately prior to the effectiveness of the Company’s IPO. Upon the adoption of the 2021 Plan, no further awards will be made under the 2017 Plan. The 2021 Plan provides for the grant of ISOs, non-qualified stock options, RSAs, RSUs, stock appreciation rights and other stock-based awards. The Company’s employees, officers, directors, consultants and advisors are eligible to receive awards under the 2021 Plan. The terms of awards, including vesting requirements, are determined by the board of directors, subject to the provisions of the 2021 Plan. The Company initially registered 3,352,725 shares of common stock under the 2021 Plan pursuant,to a Registration Statement on Form S-8 filed with the SEC on April 30, 2021, which was comprised of (i) 2,843,116 shares of common stock reserved for issuance under the 2021 Plan, (ii) 31,884 shares of common stock originally reserved for issuance under the 2017 Plan that became available for issuance under the 2021 Plan upon the completion of the Company’s IPO, and (iii) 477,725 shares of unvested restricted stock subject to repurchase by us that may become issuable under the 2021 Stock Incentive Plan following such repurchase. The 2021 Plan also provides that an additional number of shares will be added annually to the shares authorized for issuance under the 2021 Plan on the first day of each fiscal year, beginning with the fiscal year ending December 31, 2022 and continuing until, and including, the fiscal year ended December 31, 2031. The number of shares added each year will be equal to the lesser of (i) 5% of the number of outstanding common stock on such date and (ii) such amount as determined by the board of directors. As of June 30, 2021, there were 2,361,250 shares available for future issuance under the 2021 Plan. 2021 Employee Stock Purchase Plan In April 2021, the board of directors adopted and the Company’s stockholders approved the 2021 Employee Stock Purchase Plan (the “2021 ESPP”), which became effective immediately prior to the effectiveness of the Company’s IPO. The Company initially reserved 244,000 shares of common stock for future issuance under the 2021 ESPP. The 2021 ESPP provides that an additional number of shares will automatically be added to the shares reserved for issuance on the first day of each fiscal year, beginning with the fiscal year ending December 31, 2022 and continuing for each fiscal year until, and including, the fiscal year ending on December 31, 2032. The number of shares added each year will be equal to the lowest of (i) 488,000 shares of common stock, (ii) 1% of the number of shares of outstanding common stock on such date, and (iii) such amount as determined by the board of directors. No offering periods under the 2021 ESPP had been initiated as of June 30, 2021. Stock-Based Compensation Expense Total stock-based compensation expense recognized in the condensed consolidated statements of operations for the three and six months ended June 30, 2021 and 2020 was as follows (in thousands): Three Months Ended Six Months Ended 2021 2020 2021 2020 Research and development $ 212 $ 36 $ 352 $ 71 General and administrative 569 185 968 207 Total stock-based compensation $ 781 $ 221 $ 1,320 $ 278 Restricted Stock Activity The Company may, at its discretion, repurchase unvested shares of restricted stock issued pursuant to the 2017 Plan at the initial purchase price if the employees or non-employees terminate their service relationship with the Company. The shares are recorded in stockholders’ deficit as they vest. The following table summarizes restricted stock award activity during the six months ended June 30, 2021 (in thousands, except per share amounts): Shares/Units Weighted-Average Unvested at December 31, 2020 562 $ 1.54 Granted — $ — Vested (128) $ 1.54 Forfeited — $ — Unvested at June 30, 2021 434 $ 1.54 As of June 30, 2021, there was unrecognized stock-based compensation expense related to unvested restricted stock awards of $0.7 million, which the Company expects to recognize over a weighted-average period of approximately 1.8 years. The aggregate fair value of restricted stock awards that vested during the three months ended June 30, 2021 and 2020, based upon the fair values of the stock underlying the restricted stock awards on the day of vesting, was $0.8 million and $0.3 million, respectively.The aggregate fair value of restricted stock awards that vested during the six months ended June 30, 2021 and 2020, based upon the fair values of the stock underlying the restricted stock awards on the day of vesting, was $1.1 million and $0.4 million, respectively. Stock Option Activity The fair value of stock options granted during the three and six months ended June 30, 2021 and 2020 was calculated on the date of grant using the following weighted-average assumptions: Three Months Ended Six Months Ended 2021 2020 2021 2020 Risk-free interest rate 1.1 % 0.4 % 1.0 % 0.5 % Expected term (in years) 6.0 6.1 6.0 6.1 Dividend yield — % — % — % — % Expected volatility 78.9 % 88.7 % 79.3 % 88.5 % Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted during the three months ended June 30, 2021 and 2020 was $10.80 and $1.14 per share, respectively. The weighted-average grant date fair value of stock options granted during the six months ended June 30, 2021 and 2020 was $8.15 and $1.14 per share, respectively. The following table summarizes stock option activity during the six months ended June 30, 2021 (in thousands, except per share amounts): Options Outstanding Number of Options Weighted-Average Exercise Price Weighted-Average Remaining Outstanding at December 31, 2020 2,059 $ 3.79 9.76 Granted 907 $ 12.04 Exercised (42) $ 3.64 Cancelled (40) $ 9.82 Outstanding, June 30, 2021 2,884 $ 6.30 9.42 Exercisable at June 30, 2021 108 $ 3.86 8.91 The aggregate intrinsic fair value of stock options exercised during the three and six months ended June 30, 2021 was $0.2 million and $0.3 million, respectively. There were no stock options exercised during the three or six months ended June 30, 2020. As of June 30, 2021, there was unrecognized stock-based compensation expense related to unvested stock options of $11.2 million, which the Company expects to recognize over a weighted-average period of approximately 3.4 years.

Related Parties

Related Parties	6 Months Ended
	Jun. 30, 2021
Related Party Transactions [Abstract]
Related Parties	Related Parties For the three and six months ended June 30, 2020, the Company recorded $6,700 and $14,300, respectively, of general and administrative expense in the accompanying condensed consolidated statements of operations related to the MPM Capital management services. The Company did not incur any expense with MPM Capital for the three or six months ended June 30, 2021. In December 2019, the Company entered into a consulting agreement with Briggs Morrison, M.D., a member of the Company’s board of directors, for the provision of consulting, advisory and related services. Pursuant to the consulting agreement, in December 2019, the Company issued Dr. Morrison a stock option grant for 46,570 shares of common stock at an aggregate grant date fair value of $50,000, and agreed to reimburse certain of Dr. Morrison’s expenses in connection with the performance of services under the agreement. The stock

Net (Loss) Income Attributable

Net (Loss) Income Attributable to Common Stockholders per Share	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Net (Loss) Income Attributable to Common Stockholders per Share	Net (Loss) Income Attributable to Common Stockholders per Share Basic net (loss) income per share is calculated based on the weighted-average number of shares of common stock outstanding during the period, excluding the outstanding stock options and restricted stock awards that have been issued but are not yet vested. Diluted net (loss) income per share is calculated based upon the weighted-average number of shares of common stock outstanding during the period plus the dilutive impact of weighted-average common-equivalent stock outstanding during the period. The potentially dilutive shares of common stock resulting from the assumed exercise of outstanding stock options and the assumed vesting of the restricted stock awards were determined under the treasury stock method. The following table summarizes the calculation of basic and diluted net (loss) income attributable to common stockholders per share (in thousands, except per share amounts): Three Months Ended Six Months Ended 2021 2020 2021 2020 Net (loss) income attributable to common stockholders $ (67,847) $ 2,226 $ (170,298) $ (1,601) Weighted-average common shares outstanding, basic 17,750 947 9,535 891 Dilutive effect of redeemable convertible preferred stock (as converted) — 9,257 — — Dilutive effect of outstanding stock options — — — — Dilutive effect of unvested restricted common stock — 64 — — Dilutive effect of warrants to purchase common stock — 59 — — Weighted-average common shares outstanding, diluted 17,750 10,327 9,535 891 Net (loss) income per share attributable to common stockholders, basic $ (3.82) $ 2.35 $ (17.86) $ (1.80) Net (loss) income per share attributable to common stockholders, diluted $ (3.82) $ 0.22 $ (17.86) $ (1.80) The following table sets forth the outstanding shares of common stock equivalents, presented based on amounts outstanding at each period end, which were excluded from the calculation of diluted net (loss) income attributable to common stockholders per share because their effect would be anti-dilutive, including the preferred shares that were outstanding as of June 30, 2020 that would have been issued under the if-converted method (in thousands): June 30, 2021 2020 Redeemable convertible preferred stock (as converted) — 9,257 Outstanding stock options 2,884 402 Unvested restricted common stock 436 699 Warrants to purchase common stock 59 59 Total 3,379 10,417

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	The accompanying condensed consolidated financial statements as of June 30, 2021, and for the three and six months ended June 30, 2021 and 2020, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and generally accepted accounting principles in the United States of America (“GAAP”) as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”) for condensed consolidated financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these condensed consolidated financial statements reflect all normal recurring adjustments which are necessary for a fair presentation of the Company’s financial position and results of its operations, as of and for the periods presented. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s final prospectus for its IPO dated April 29, 2021 and filed with the SEC pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended (the “Prospectus”).
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates which include, but are not limited to, the fair values of common stock and redeemable convertible preferred stock, the fair value of the warrant liabilities, and the fair value of the preferred stock tranche rights. Actual results could differ from those estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In October 2020, the FASB issued ASU 2020-10, Codification Improvements , which updates various codification topics by clarifying or improving disclosure requirements to align with the SEC’s regulations. The Company adopted ASU 2020-10 as of the reporting period beginning January 1, 2021 and the adoption did not have material impact on the Company’s condensed consolidated balance sheets, condensed consolidated statements of operations or related disclosures. In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments . This guidance amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses for most financial assets and certain other instruments that aren’t measured at fair value through net income. The Company has adopted the new guidance effective January 1, 2021 and the adoption did not have any material impact on the Company’s condensed consolidated balance sheets, condensed consolidated statements of operations or related disclosures.

Financial Instruments and Fai_2

Financial Instruments and Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Assets Measured at Fair Value on a Recurring Basis	Assets measured at fair value on a recurring basis as of June 30, 2021 were as follows (in thousands): Quoted Price in Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Assets: Money market funds $ 183,233 $ — $ — $ 183,233 Total assets $ 183,233 $ — $ — $ 183,233 Assets measured at fair value on a recurring basis as of December 31, 2020 were as follows (in thousands): Quoted Price in Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Assets: Money market funds $ 92,570 $ — $ — $ 92,570 Total assets $ 92,570 $ — $ — $ 92,570

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	6 Months Ended
	Jun. 30, 2021
Payables and Accruals [Abstract]
Accrued Expenses	Accrued expenses and other current liabilities as of June 30, 2021 and December 31, 2020 were comprised as follows (in thousands): June 30, December 31, Manufacturing $ 1,375 $ 1,741 Employee compensation and benefits 1,000 990 Professional fees 416 654 Contract research 635 107 Other 30 94 Total accrued expenses and other current liabilities $ 3,456 $ 3,586

Common and Preferred Stock (Tab

Common and Preferred Stock (Tables)	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Schedule of Common Stock Reserved for Issuance	The Company had reserved shares of common stock for issuance as follows (in thousands): As of June 30, As of December 31, 2021 2020 Redeemable convertible preferred stock outstanding — 18,280 Options issued and outstanding 2,884 2,059 Warrants issued and outstanding 59 59 Total 2,943 20,398

Stock-based Compensation (Table

Stock-based Compensation (Tables)	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Stock-based Compensation Expense Recognized	Total stock-based compensation expense recognized in the condensed consolidated statements of operations for the three and six months ended June 30, 2021 and 2020 was as follows (in thousands): Three Months Ended Six Months Ended 2021 2020 2021 2020 Research and development $ 212 $ 36 $ 352 $ 71 General and administrative 569 185 968 207 Total stock-based compensation $ 781 $ 221 $ 1,320 $ 278
Restricted Stock Awards Activity	The following table summarizes restricted stock award activity during the six months ended June 30, 2021 (in thousands, except per share amounts): Shares/Units Weighted-Average Unvested at December 31, 2020 562 $ 1.54 Granted — $ — Vested (128) $ 1.54 Forfeited — $ — Unvested at June 30, 2021 434 $ 1.54
Weighted -average Valuation Assumptions	The fair value of stock options granted during the three and six months ended June 30, 2021 and 2020 was calculated on the date of grant using the following weighted-average assumptions: Three Months Ended Six Months Ended 2021 2020 2021 2020 Risk-free interest rate 1.1 % 0.4 % 1.0 % 0.5 % Expected term (in years) 6.0 6.1 6.0 6.1 Dividend yield — % — % — % — % Expected volatility 78.9 % 88.7 % 79.3 % 88.5 %
Summary of Stock Option Activity	The following table summarizes stock option activity during the six months ended June 30, 2021 (in thousands, except per share amounts): Options Outstanding Number of Options Weighted-Average Exercise Price Weighted-Average Remaining Outstanding at December 31, 2020 2,059 $ 3.79 9.76 Granted 907 $ 12.04 Exercised (42) $ 3.64 Cancelled (40) $ 9.82 Outstanding, June 30, 2021 2,884 $ 6.30 9.42 Exercisable at June 30, 2021 108 $ 3.86 8.91

Net (Loss) Income Attributabl_2

Net (Loss) Income Attributable to Common Stockholders per Share (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Schedule of Calculation of Basic and Diluted Net (Loss) Income per Share	The following table summarizes the calculation of basic and diluted net (loss) income attributable to common stockholders per share (in thousands, except per share amounts): Three Months Ended Six Months Ended 2021 2020 2021 2020 Net (loss) income attributable to common stockholders $ (67,847) $ 2,226 $ (170,298) $ (1,601) Weighted-average common shares outstanding, basic 17,750 947 9,535 891 Dilutive effect of redeemable convertible preferred stock (as converted) — 9,257 — — Dilutive effect of outstanding stock options — — — — Dilutive effect of unvested restricted common stock — 64 — — Dilutive effect of warrants to purchase common stock — 59 — — Weighted-average common shares outstanding, diluted 17,750 10,327 9,535 891 Net (loss) income per share attributable to common stockholders, basic $ (3.82) $ 2.35 $ (17.86) $ (1.80) Net (loss) income per share attributable to common stockholders, diluted $ (3.82) $ 0.22 $ (17.86) $ (1.80)
Schedule of Antidilutive Securities Excluded from Computation of (Loss) Income per Share	The following table sets forth the outstanding shares of common stock equivalents, presented based on amounts outstanding at each period end, which were excluded from the calculation of diluted net (loss) income attributable to common stockholders per share because their effect would be anti-dilutive, including the preferred shares that were outstanding as of June 30, 2020 that would have been issued under the if-converted method (in thousands): June 30, 2021 2020 Redeemable convertible preferred stock (as converted) — 9,257 Outstanding stock options 2,884 402 Unvested restricted common stock 436 699 Warrants to purchase common stock 59 59 Total 3,379 10,417

Description of Business, Orga_2

Description of Business, Organization, and Liquidity (Details) - USD ($) $ / shares in Units, $ in Thousands	May 04, 2021	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Subsidiary, Sale of Stock [Line Items]
Proceeds from initial public offering of common stock			$ 111,600	$ 0
Cash and cash equivalents		$ 183,233	$ 183,233		$ 92,570
Common Stock
Subsidiary, Sale of Stock [Line Items]
Aggregate shares converted (shares)		18,280,000
IPO
Subsidiary, Sale of Stock [Line Items]
Proceeds from initial public offering of common stock	$ 120,000
Net proceeds from the IPO	$ 109,200
Aggregate shares converted (shares)	18,279,712
IPO | Common Stock
Subsidiary, Sale of Stock [Line Items]
Shares issued in IPO (shares)	7,500,000
Price per share (in usd per share)	$ 16
Aggregate shares converted (shares)	18,300,000

Financial Instruments and Fai_3

Financial Instruments and Fair Value Measurements (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 30, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Redeemable convertible preferred stock issued (shares)			48,675,140
Preferred stock tranche liability			$ 7,300,000	$ 7,800,000
Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	$ 183,233,000	$ 92,570,000
Liabilities measured at fair value on recurring basis	0	0
Money market funds | Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market funds	183,233,000	92,570,000
Quoted Price in Active Markets (Level 1) | Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	183,233,000	92,570,000
Quoted Price in Active Markets (Level 1) | Money market funds | Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market funds	183,233,000	92,570,000
Significant Other Observable Inputs (Level 2) | Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0	0
Significant Other Observable Inputs (Level 2) | Money market funds | Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market funds	0	0
Significant Unobservable Inputs (Level 3) | Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0	0
Significant Unobservable Inputs (Level 3) | Money market funds | Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market funds	$ 0	$ 0

Restricted Cash (Details)

Restricted Cash (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Abstract]
Non-current restricted cash	$ 1.3	$ 0.2
Restricted cash included in "Prepaid expenses and other current assets"	$ 0.1

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Manufacturing	$ 1,375	$ 1,741
Employee compensation and benefits	1,000	990
Professional fees	416	654
Contract research	635	107
Other	30	94
Total accrued expenses and other current liabilities	$ 3,456	$ 3,586

Term Loan (Details)

Term Loan (Details) - Term loan - USD ($)	1 Months Ended	14 Months Ended
	May 31, 2020	Jun. 30, 2021	Feb. 28, 2021	Jun. 30, 2020
Term Loan A
Debt Instrument [Line Items]
Term loan available	$ 6,000,000
Delayed draw fee	$ 25,000
Term Loan B
Debt Instrument [Line Items]
Term loan available				$ 8,000,000
the Term Loans
Debt Instrument [Line Items]
Drawings on Term Loans		$ 0
Outstanding borrowings		0
Floating rate spread in effect (greater than) (percent)	5.00%
Success Fee (percent)	5.00%
Success Fee survival term	10 years
Default payment fee (percent)	5.00%
Unrestricted cash balance ratio to monthly cash burn	2.5
Maximum annual capital expenditures	$ 400,000
Capacity available to draw on the Term Loans		$ 14,000,000
the Term Loans | In FY 2021
Debt Instrument [Line Items]
Maximum annual capital expenditures			$ 2,000,000
the Term Loans | After FY 2021
Debt Instrument [Line Items]
Maximum annual capital expenditures			$ 500,000
the Term Loans | Prime Rate
Debt Instrument [Line Items]
Floating rate spread in effect (greater than) (percent)	1.75%

Common and Preferred Stock (Det

Common and Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	May 04, 2021	Jun. 01, 2020	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 30, 2019
Class of Stock [Line Items]
Common stock authorized (shares)			200,000,000	200,000,000		193,500,000
Common stock available for issuance (shares)			2,943,000	2,943,000		20,398,000
Issuance costs				$ 2,087	$ 26
Convertible notes exchanged upon issuance of preferred stock shares			$ 293,024
Preferred stock tranche liability							$ 7,300	$ 7,800
Preferred stock authorized (shares)			5,000,000	5,000,000		0
Preferred stock issued (shares)			0	0		0
Preferred stock outstanding (shares)			0	0		0
Common Stock
Class of Stock [Line Items]
Aggregate shares converted (shares)			18,280,000
IPO
Class of Stock [Line Items]
Aggregate shares converted (shares)	18,279,712
IPO | Common Stock
Class of Stock [Line Items]
Aggregate shares converted (shares)	18,300,000
Price per share (in usd per share)	$ 16
Additional shares issued in IPO (shares)	7,500,000
Redeemable convertible preferred stock outstanding
Class of Stock [Line Items]
Common stock available for issuance (shares)			0	0		18,280,000
Options issued and outstanding
Class of Stock [Line Items]
Common stock available for issuance (shares)			2,884,000	2,884,000		2,059,000
Warrants issued and outstanding
Class of Stock [Line Items]
Common stock available for issuance (shares)			59,000	59,000		59,000
Series A Preferred Stock
Class of Stock [Line Items]
Price per share (in usd per share)						$ 0.70
Series A Preferred Stock | IPO
Class of Stock [Line Items]
Price per share (in usd per share)						$ 0.70
Proceeds from issuance of preferred stock						$ 44,000
Issuance costs						200
Convertible notes exchanged upon issuance of preferred stock shares						$ 12,000
Series A Redeemable Convertible Preferred Stock | Second Closing
Class of Stock [Line Items]
Additional shares issued in IPO (shares)		31,571,425
Purchase price per share (in usd per share)		$ 0.70
Preferred stock tranche liability		$ 7,800
Series B Preferred Stock
Class of Stock [Line Items]
Price per share (in usd per share)						$ 0.92
Series B Preferred Stock | IPO
Class of Stock [Line Items]
Price per share (in usd per share)						$ 0.92
Proceeds from issuance of preferred stock						$ 71,800
Issuance costs						$ 300

Stock-based Compensation - Narr

Stock-based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock available for issuance (shares)		2,943,000		2,943,000		20,398,000
Weighted-average grant date fair value of awards (in usd per share)		$ 10,800,000	$ 1,140,000	$ 8,150,000	$ 1,140,000
Aggregate intrinsic fair value of options exercised		$ 0.2	$ 0	$ 0.3	$ 0
Share-based compensation expense not yet recognized		$ 11.2		$ 11.2
2021 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Maximum number of shares to be added annually, as a percentage of outstanding shares (percent)	5.00%
2017 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock available for issuance (shares)		2,361,250		2,361,250
Common Stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (shares)	3,352,725
Common Stock | 2021 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (shares)	2,843,116
Common Stock | 2017 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (shares)	31,884
Unvested restricted common stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense not yet recognized		$ 0.7		$ 0.7
Share-based compensation not yet recognized, recognition period				1 year 9 months 18 days
Aggregate fair value of awards that vested		$ 0.8	$ 0.3	$ 1.1	$ 0.4
Unvested restricted common stock | 2021 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (shares)	477,725
Stock options
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation not yet recognized, recognition period				3 years 4 months 24 days
Employee stock | 2021 Stock Employee Stock Purchase Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (shares)	244,000
Employee stock | 2021 Stock Employee Stock Purchase Plan | Minimum
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Maximum number of shares to be added annually, as a percentage of outstanding shares (percent)	1.00%
Maximum number of shares to be added annually, as a percentage of outstanding shares (shares)	488,000

Stock-based Compensation - Expe

Stock-based Compensation - Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 781	$ 221	$ 1,320	$ 278
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	212	36	352	71
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 569	$ 185	$ 968	$ 207

Stock-based Compensation - Rest

Stock-based Compensation - Restricted Stock Award Activity (Details) - Unvested restricted common stock shares in Thousands	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Shares/Units
Unvested at beginning of period (shares) | shares	562
Granted (shares) | shares	0
Vested (shares) | shares	(128)
Forfeited (shares) | shares	0
Unvested at end of period (shares) | shares	434
Weighted-Average Grant Date Fair Value Per Share
Weighted Average Grant Date Fair Value - Unvested at beginning of period (in usd per share) | $ / shares	$ 1.54
Weighted Average Grant Date Fair Value - Granted (in usd per share) | $ / shares	0
Weighted Average Grant Date Fair Value - Vested (in usd per share) | $ / shares	1.54
Weighted Average Grant Date Fair Value - Forfeited (in usd per share) | $ / shares	0
Weighted Average Grant Date Fair Value - Unvested at end of period (in usd per share) | $ / shares	$ 1.54

Stock-based Compensation - Weig

Stock-based Compensation - Weighted Average Assumptions (Details) - Stock options	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Risk-free interest rate	1.10%	0.40%	1.00%	0.50%
Expected term (in years)	6 years	6 years 1 month 6 days	6 years	6 years 1 month 6 days
Dividend yield	0.00%	0.00%	0.00%	0.00%
Expected volatility	78.90%	88.70%	79.30%	88.50%

Stock-based Compensation - Stoc

Stock-based Compensation - Stock Option Activity (Details) shares in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2021$ / sharesshares	Jun. 30, 2021$ / sharesshares
Number of Options
Outstanding at beginning of period (shares) | shares	2,059	2,059
Granted (shares) | shares		907
Exercised (shares) | shares		(42)
Cancelled (shares) | shares		(40)
Outstanding at end of period (shares) | shares		2,884
Exercisable at end of period (shares) | shares		108
Weighted-Average Exercise Price
Weighted-Average Exercise Price - Outstanding at beginning of period (in usd per share) | $ / shares	$ 3.79	$ 3.79
Weighted-Average Exercise Price - Granted (in usd per share) | $ / shares		12.04
Weighted-Average Exercise Price - Exercised (in usd per share) | $ / shares		3.64
Weighted-Average Exercise Price - Cancelled (in usd per share) | $ / shares		9.82
Weighted-Average Exercise Price - Outstanding at end of period (in usd per share) | $ / shares		6.30
Weighted-Average Exercise Price - Exercisable at end of period (in usd per share) | $ / shares		$ 3.86
Weighted-Average Remaining Contractual Life (in years)
Weighted Average Remaining Contractual Life - Outstanding	9 years 9 months 3 days	9 years 5 months 1 day
Weighted Average Remaining Contractual Life - Exercisable		8 years 10 months 28 days

Related Parties (Details)

Related Parties (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Dec. 31, 2019	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Related Party Transaction [Line Items]
Options granted (shares)				907,000
Exercise price (in usd per share)				$ 12.04
Total stock-based compensation		$ 781,000	$ 221,000	$ 1,320,000	$ 278,000
MPM Capital | Management Services
Related Party Transaction [Line Items]
General and administrative expenses		0	6,700	0	14,300
Director | Briggs Morrison, M.D. | Consulting, Advisory and Related Services
Related Party Transaction [Line Items]
Options granted (shares)	46,570
Grant date fair value	$ 50,000
Exercise price (in usd per share)	$ 1.56
Director | Briggs Morrison, M.D. | Consulting, Advisory and Related Services | Options issued and outstanding
Related Party Transaction [Line Items]
Vesting period	4 years
Total stock-based compensation		$ 17,300	$ 3,100	$ 20,400	$ 6,200
Director | Briggs Morrison, M.D. | Consulting, Advisory and Related Services | Options issued and outstanding | Monthly installments
Related Party Transaction [Line Items]
Shares underlying stock options scheduled to vest in monthly installments (percent)	2.0833%

Net (Loss) Income Attributabl_3

Net (Loss) Income Attributable to Common Stockholders per Share - Antidilutive Shares (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net (loss) income attributable to common stockholders	$ (67,847)	$ 2,226	$ (170,298)	$ (1,601)
Net (loss) income attributable to common stockholders	$ (67,847)	$ 2,226	$ (170,298)	$ (1,601)
Weighted average common shares outstanding, basic (shares)	17,750	947	9,535	891
Dilutive effect of redeemable convertible preferred stock (as converted)	0	9,257	0	0
Dilutive effect of warrants to purchase common stock	0	59	0	0
Weighted average common shares outstanding, diluted (shares)	17,750	10,327	9,535	891
Net (loss) income per share attributable to common stockholders, basic (usd per share)	$ (3.82)	$ 2.35	$ (17.86)	$ (1.80)
Net (loss) income per share attributable to common stockholders, diluted (usd per share)	$ (3.82)	$ 0.22	$ (17.86)	$ (1.80)
Options issued and outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive effect of stock options and unvested restricted common stock	0	0	0	0
Unvested restricted common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive effect of stock options and unvested restricted common stock	0	64	0	0

Net (Loss) Income Attributabl_4

Net (Loss) Income Attributable to Common Stockholders per Share - Antidilutive Shares (Details) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	3,379,000	10,417,000
Redeemable convertible preferred stock (as converted)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	0	9,257,000
Options issued and outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	2,884,000	402,000
Unvested restricted common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	436,000	699,000
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	59,000	59,000