Werewolf Therapeutics (HOWL) 10-Q 10 Jun 21 2021 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2021	Jun. 04, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 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		27,567,644
Entity Central Index Key	0001785530
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 84,602	$ 92,570
Prepaid expenses and other current assets	263	344
Total current assets	84,865	92,914
Property and equipment, net	694	651
Restricted cash	298	207
Operating lease right of use asset	2,305	2,471
Deferred financing costs	1,274	155
Total assets	89,436	96,398
Current liabilities:
Accounts payable	1,800	1,021
Accrued expenses	2,890	3,586
Operating lease liability, current	699	677
Other current liabilities	20	0
Total current liabilities	5,409	5,284
Operating lease liability, net of current portion	1,683	1,864
Other liabilities	0	31
Total liabilities	7,092	7,179
Commitments and contingencies
Stockholders’ deficit:
Common stock, $0.0001 par value, 196,000 shares and 193,500 shares authorized as of March 31, 2021 and December 31, 2020, respectively; 1,760 and 1,746 shares issued and outstanding as of March 31, 2021 and December 31, 2020, respectively	2	2
Additional paid-in capital	0	0
Accumulated deficit	(153,756)	(51,865)
Total stockholders’ deficit	(153,754)	(51,863)
Total liabilities, redeemable convertible preferred stock, and stockholders’ deficit	89,436	96,398
Series A Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	$ 118,765	$ 69,012
Stockholders’ deficit:
Redeemable convertible preferred stock authorized (shares)	80,247,000	80,247,000
Series B Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	$ 117,333	$ 72,070
Stockholders’ deficit:
Redeemable convertible preferred stock authorized (shares)	78,222,173	78,222,000

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Common stock par value (usd per share)	$ 0.0001	$ 0.0001
Common stock authorized (shares)	196,000,000	193,500,000
Common stock issued (shares)	1,760,000	1,746,000
Common stock outstanding (shares)	1,760,000	1,746,000
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)	80,247,000	80,247,000
Redeemable convertible preferred stock issued (shares)	80,246,565	80,247,000
Redeemable convertible preferred stock outstanding (shares)	80,246,565	80,247,000
Redeemable convertible preferred stock liquidation preference	$ 118,765	$ 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)	78,222,173	78,222,000
Redeemable convertible preferred stock issued (shares)	78,222,173	78,222,000
Redeemable convertible preferred stock outstanding (shares)	78,222,173	78,222,000
Redeemable convertible preferred stock liquidation preference	$ 117,333	$ 72,070

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating expenses:
Research and development	$ 4,817	$ 2,763
General and administrative	2,635	1,131
Total operating expenses	7,452	3,894
Operating loss	(7,452)	(3,894)
Other income:
Interest income, net	33	67
Other expense, net	(16)	0
Total other income	17	67
Net loss	(7,435)	(3,827)
Accretion of redeemable convertible preferred stock to redemption value	(95,016)	0
Net loss attributable to common stockholders	(102,451)	(3,827)
Net loss attributable to common stockholders	$ (102,451)	$ (3,827)
Net loss per share attributable to common stockholders, basic and diluted
Net loss per share attributable to common stockholders, basic (usd per share)	$ (83.36)	$ (4.58)
Net loss per share attributable to common stockholders, diluted (usd per share)	$ (83.36)	$ (4.58)
Weighted-average common shares outstanding, basic and diluted
Weighted average common shares outstanding, basic (shares)	1,229	836
Weighted average common shares outstanding, diluted (shares)	1,229	836

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders’ Deficit (unaudited) - USD ($) $ 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				48,675,000	0
Redeemable convertible preferred stock outstanding, beginning balance at Dec. 31, 2019				$ 34,703	$ 0
Redeemable convertible preferred stock outstanding, ending balance (shares) at Mar. 31, 2020				48,675,000	0
Redeemable convertible preferred stock outstanding, ending balance at Mar. 31, 2020				$ 34,703	$ 0
Shares outstanding, beginning balance (shares) at Dec. 31, 2019						1,737,000
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)
Shares outstanding, ending balance (shares) at Mar. 31, 2020						1,737,000
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, 2020		80,247,000	78,222,000	80,247,000	78,222,000
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		80,246,565	78,222,173	80,247,000	78,222,000
Redeemable convertible preferred stock outstanding, ending balance at Mar. 31, 2021		$ 118,765	$ 117,333	$ 118,765	$ 117,333
Shares outstanding, beginning balance (shares) at Dec. 31, 2020						1,746,000
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)	13,000					14,000
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)
Shares outstanding, ending balance (shares) at Mar. 31, 2021						1,760,000
Stockholders' equity, ending balance at Mar. 31, 2021	$ (153,754)					$ 2	$ 0	$ (153,756)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities:
Net loss	$ (7,435)	$ (3,827)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	539	57
Depreciation	39	23
Non-cash lease expense	166	152
Changes in operating assets and liabilities:
Prepaid expenses and other assets	81	23
Accounts payable	724	302
Accrued expenses	(1,331)	(47)
Right of use assets and operating lease liability	(159)	(71)
Other liabilities	50	(11)
Net cash used in operating activities	(7,326)	(3,399)
Investing activities:
Purchases of property and equipment	(13)	(449)
Net cash used in investing activities	(13)	(449)
Financing activities:
Deferred financing costs	(559)	0
Stock option exercise	21	0
Net cash used in financing activities	(538)	0
Net decrease in cash and cash equivalents	(7,877)	(3,848)
Cash, cash equivalents and restricted cash—beginning of period	92,777	18,104
Cash, cash equivalents and restricted cash—end of period	84,900	14,256
Non-cash investing and financing activities:
Non-cash accretion of Series A and Series B redeemable convertible preferred stock	95,016	0
Issuance costs in accounts payable and accrued expenses	560	0
Purchases of property and equipment in accounts payable and accrued expenses	$ 130	$ 66

Description of Business, Organi

Description of Business, Organization, and Liquidity	3 Months Ended
	Mar. 31, 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 $108.9 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 as of March 31, 2021 was automatically converted into an aggregate of 18,279,712 shares of common stock. The Company had cash and cash equivalents of $84.6 million at March 31, 2021. The Company expects that its cash and cash equivalents, including the net proceeds from its IPO, will enable it to fund its operating expenses and capital expenditure requirements for at least twelve months from June 10, 2021, 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	3 Months Ended
	Mar. 31, 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 March 31, 2021, and for the three months ended March 31, 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 March 31, 2021, and for the three months ended March 31, 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 months ended March 31, 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 three months ended March 31, 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	3 Months Ended
	Mar. 31, 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 March 31, 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 $ 84,602 $ — $ — $ 84,602 Total assets $ 84,602 $ — $ — $ 84,602 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 months ended March 31, 2021. There were no liabilities measured at fair value on a recurring basis as of March 31, 2021 or December 31, 2020. Preferred Stock Tranche Liability —

Restricted Cash

Restricted Cash	3 Months Ended
	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
Restricted Cash	Restricted CashThe Company maintained non-current restricted cash of $0.3 million and $0.2 million at March 31, 2021 and December 31, 2020, respectively. This amount is comprised solely of letters of credit required pursuant to the Company’s leased office spaces.

Accrued Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2021
Payables and Accruals [Abstract]
Accrued Expenses	Accrued Expenses Accrued expenses as of March 31, 2021 and December 31, 2020 were comprised as follows (in thousands): March 31, December 31, Manufacturing $ 1,166 $ 1,741 Employee compensation and benefits 381 990 Professional fees 832 654 Contract research 123 107 Other 388 94 Total accrued expenses $ 2,890 $ 3,586

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	3 Months Ended
	Mar. 31, 2021
Temporary Equity Disclosure [Abstract]
Redeemable Convertible Preferred Stock	Redeemable Convertible Preferred Stock The Company’s Series A and Series B redeemable convertible preferred stock, together referred to as “Preferred Stock,” has been 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 as of March 31, 2021 was automatically converted into an aggregate of 18.3 million shares of common stock. Series A Preferred Stock As of March 31, 2021, 80,246,565 shares of Series A Preferred Stock were issued and outstanding. These 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 As of March 31, 2021, 78,222,173 shares of Series B redeemable convertible preferred stock (“Series B Preferred Stock”) were authorized, issued and outstanding. These 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. Rights, preferences, privileges, and restrictions: The holders of Preferred Stock had the rights, preferences, privileges, and restrictions as set forth below: Dividends: The holders of Preferred Stock were entitled to receive non-cumulative dividends when, as and if declared by the Company’s board of directors at a rate of $0.056 per share and $0.0737 per share, respectively. The Company could only declare dividends on the common stock if the holders of Preferred Stock simultaneously received dividends at the same rate and same time as the common stock, with the holders of Preferred Stock participating on an as-if converted basis. No dividends were declared or paid as of March 31, 2021. Voting Rights: The holders of Preferred Stock were entitled to voting rights equal to the number of shares of common stock into which the shares of Preferred Stock were convertible. As long as at least 15,000,000 shares of Preferred Stock remained outstanding, the holders of Series A Preferred Stock, exclusively and as a separate class, were entitled to elect four members of the Company’s board of directors, and the holders of Series B Preferred Stock, exclusively and as a separate class, were entitled to elect two members of the Company’s board of directors. If the holders of the Preferred Stock failed to elect a sufficient number of directors to fulfill directorships for which they were entitled to elect directors, then any directorship would have remained vacant until the holders of Preferred Stock elected a person. The holders of common stock, and any other class or series of voting stock (including Preferred Stock) exclusively and voting together as a single class, were entitled to elect the balance of the total number of directors of the Company. Liquidation Rights: In the event of any liquidation, dissolution or winding up of the Company, whether voluntary or involuntary, the holders of Preferred Stock had liquidation preferences, before any distribution or payment would have been made to holders of common stock, in an amount per share 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) an amount per share that would have been payable had, in the case of the Series A Preferred Stock, all shares of Series A Preferred Stock and, in the case of the Series B Preferred Stock, all shares of Series B Preferred Stock been converted to common stock. If the assets and funds to be distributed among the holders of Preferred Stock were insufficient to permit the payment to such holders, then the entire assets and funds of the Company legally available for distribution would have been distributed ratably among the holders of Preferred Stock in proportion to the preferential amount each such holder was otherwise entitled to receive. Upon completion of the payment of the full liquidation preference of Preferred Stock, the remaining assets of the Company, if any, would have been distributed among the holders of common stock, pro rata based on the number of shares held by each common stockholder. Conversion: Each share of Preferred Stock was convertible into shares of common stock, at the option of the holder, at any time after date of issuance. As of March 31, 2021, each share of Preferred Stock was automatically convertible into the number of shares of common stock determined in accordance with the conversion rate upon the earlier of (i) the closing of a public offering, in which the gross cash proceeds are at least $75.0 million and the initial offering price to the public is at least $24.01 per share (as adjusted for any stock splits, stock dividends, combinations, subdivisions, recapitalizations, reorganizations, reclassifications or the like) or (ii) the occurrence of an event, specified by vote or written consent of the holders of 67% of the Series B Preferred Stock. Redemption: As of March 31, 2021, the Preferred Stock was not redeemable. 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. Protective Provisions:

Term Loan

Term Loan	3 Months Ended
	Mar. 31, 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 (“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 March 31, 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. 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 March 31, 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 Stock

Common Stock	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Common Stock	Common Stock Common stockholders are entitled to dividends if and when declared by the Company’s board of directors subject to the rights of the preferred stockholders. As of March 31, 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 March 31, As of December 31, 2021 2020 Redeemable convertible preferred stock outstanding 18,280 18,280 Options issued and outstanding 2,401 2,059 Warrants issued and outstanding 59 59 Total 20,740 20,398

Stock-based Compensation

Stock-based Compensation	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-based Compensation	Stock-based Compensation In 2017, the Company adopted the 2017 Stock Incentive Plan (the “Plan”), as amended and restated, under which it could grant incentive stock options (“ISOs”), non-qualified stock options, restricted stock awards, restricted stock units, 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. As of March 31, 2021, the maximum number of shares of common stock authorized to be issued under the Plan was 3,728,307 shares, of which 28,893 shares were available for future issuance under the Plan. Stock-Based Compensation Expense Total stock-based compensation expense recognized in the condensed consolidated statements of operations for the three months ended March 31, 2021 and 2020 was as follows (in thousands): Three Months Ended 2021 2020 Research and development $ 140 $ 35 General and administrative 399 22 Total stock-based compensation $ 539 $ 57 Restricted Stock Activity Restricted stock issued under the Plan allow the Company, at its discretion, to repurchase unvested shares 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 three months ended March 31, 2021 (in thousands, except per share amounts): Shares/Units Weighted-Average Unvested at December 31, 2020 562 $ 1.54 Granted — $ — Vested (64) $ 1.53 Forfeited — $ — Unvested at March 31, 2021 498 $ 1.54 As of March 31, 2021, there was unrecognized stock-based compensation expense related to unvested restricted stock awards of $0.8 million, which the Company expects to recognize over a weighted-average period of approximately 2.0 years. The aggregate fair value of restricted stock awards that vested during the three months ended March 31, 2021 and 2020, based upon the fair values of the stock underlying the restricted stock awards on the day of vesting, was $0.3 million and $0.1 million, respectively. Stock Option Activity The fair value of stock options granted during the three months ended March 31, 2021 and 2020 was calculated on the date of grant using the following weighted-average assumptions: Three Months Ended 2021 2020 Risk-free interest rate 0.8 % 0.9 % Expected term (in years) 6.0 6.0 Dividend yield — % — % Expected volatility 79.8 % 86.3 % Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted during the three months ended March 31, 2021 and 2020 was $4.23 and $1.12 per share, respectively. The following table summarizes stock option activity during the three months ended March 31, 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 356 $ 6.22 Exercised (13) $ 1.56 Cancelled — $ — Outstanding, March 31, 2021 2,402 $ 4.16 9.58 Exercisable at March 31, 2021 54 $ 3.25 9.14 The aggregate intrinsic fair value of stock options exercised during the three months ended March 31, 2021 was $0.1 million. There were no stock options exercised during the three months ended March 31, 2020. As of March 31, 2021, there was unrecognized stock-based compensation expense related to unvested stock options of $6.2 million, which the Company expects to recognize over a weighted-average period of approximately 3.6 years.

Related Parties

Related Parties	3 Months Ended
	Mar. 31, 2021
Related Party Transactions [Abstract]
Related Parties	Related Parties For the three months ended March 31, 2020, the Company recorded $8,000 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 months ended March 31, 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 for 46,570 shares of our 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 option has an exercise price of $1.56 per share and is scheduled to vest with respect to 2.0833% of the shares underlying the stock option in equal monthly installments over four years following November 2019, subject to continuous service. The Company recognized $3,000 of expense related to this award in the research and development line in the condensed consolidated statements of operations for both the three months ended March 31, 2021 and 2020.

Net Loss Attributable to Common

Net Loss Attributable to Common Stockholders per Share	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Net Loss Attributable to Common Stockholders per Share	Net Loss Attributable to Common Stockholders per Share For purposes of the diluted net loss attributable to common stockholders per share calculation, redeemable convertible preferred stock, outstanding stock options, unvested restricted stock awards and warrants to purchase common stock are considered to be potentially dilutive securities, however the following weighted-average amounts were excluded from the calculation of diluted net loss attributable to common stockholders per share because their effect would be anti-dilutive (in thousands): As of March 31, 2021 2020 Redeemable convertible preferred stock (as converted) 18,280 5,615 Outstanding stock options 2,401 193 Unvested restricted common stock 498 886 Warrants to purchase common stock 59 59 Total 21,238 6,753

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Reverse Stock Split In connection with preparing for its initial public offering, the Company’s board of directors and stockholders approved an amendment to the Company’s certificate of incorporation, which became effective on April 23, 2021. The amendment, among other things, effected a 1-for-8.6691 reverse stock split of the Company’s common stock and a proportional adjustment to the conversion price for each series of preferred stock and to the exercise prices and number of shares of common stock underlying the outstanding stock options, and modified the requirements for the automatic conversion of all outstanding shares of preferred stock. All share and per share amounts in the condensed consolidated financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to the reverse stock split. Amendments to Articles of Incorporation In connection with the completion of the IPO, the board of directors and stockholders approved the amended and restated certificate of incorporation to, among other things, provide for 200,000,000 authorized shares of common stock with a par value of $0.0001 per share and 5,000,000 authorized shares of preferred stock with a par value of $0.0001 per share. Stock Plans The Company's board of directors adopted and the Company's stockholders approved the 2021 stock incentive plan ("2021 Plan"), which became effective immediately prior to the effectiveness of the Company's IPO. The 2021 Plan provides for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock units, stock appreciation rights and other stock-based awards. The Company's employees, officers, directors and consultants and advisors are eligible to receive awards under the 2021 Plan. The Company's board of directors adopted and the Company's stockholders approved the 2021 employee stock purchase plan, which became effective upon the closing of the Company's IPO. Lease In June 2021, the Company entered into an office lease agreement (the “Lease”) for approximately 25,778 square feet of laboratory and office space in Watertown, Massachusetts, which will serve as the Company’s headquarters. The lease term is targeted to commence in March 2022 and has an approximate eight year term. Total estimated base rent payments over the term of the lease are approximately $17.9 million. The Company will also pay its proportional share of operating expenses and tax obligations. The Company provided the landlord with a security deposit in the form of a letter of credit in the amount of $1.0 million upon signing.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	The accompanying condensed consolidated financial statements as of March 31, 2021, and for the three months ended March 31, 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)	3 Months Ended
	Mar. 31, 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 March 31, 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 $ 84,602 $ — $ — $ 84,602 Total assets $ 84,602 $ — $ — $ 84,602 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 (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2021
Payables and Accruals [Abstract]
Accrued Expenses	Accrued expenses as of March 31, 2021 and December 31, 2020 were comprised as follows (in thousands): March 31, December 31, Manufacturing $ 1,166 $ 1,741 Employee compensation and benefits 381 990 Professional fees 832 654 Contract research 123 107 Other 388 94 Total accrued expenses $ 2,890 $ 3,586

Common Stock (Tables)

Common Stock (Tables)	3 Months Ended
	Mar. 31, 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 March 31, As of December 31, 2021 2020 Redeemable convertible preferred stock outstanding 18,280 18,280 Options issued and outstanding 2,401 2,059 Warrants issued and outstanding 59 59 Total 20,740 20,398

Stock-based Compensation (Table

Stock-based Compensation (Tables)	3 Months Ended
	Mar. 31, 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 months ended March 31, 2021 and 2020 was as follows (in thousands): Three Months Ended 2021 2020 Research and development $ 140 $ 35 General and administrative 399 22 Total stock-based compensation $ 539 $ 57
Restricted Stock Awards Activity	The following table summarizes restricted stock award activity during the three months ended March 31, 2021 (in thousands, except per share amounts): Shares/Units Weighted-Average Unvested at December 31, 2020 562 $ 1.54 Granted — $ — Vested (64) $ 1.53 Forfeited — $ — Unvested at March 31, 2021 498 $ 1.54
Weighted -average Valuation Assumptions	The fair value of stock options granted during the three months ended March 31, 2021 and 2020 was calculated on the date of grant using the following weighted-average assumptions: Three Months Ended 2021 2020 Risk-free interest rate 0.8 % 0.9 % Expected term (in years) 6.0 6.0 Dividend yield — % — % Expected volatility 79.8 % 86.3 %
Summary of Stock Option Activity	The following table summarizes stock option activity during the three months ended March 31, 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 356 $ 6.22 Exercised (13) $ 1.56 Cancelled — $ — Outstanding, March 31, 2021 2,402 $ 4.16 9.58 Exercisable at March 31, 2021 54 $ 3.25 9.14

Net Loss Attributable to Comm_2

Net Loss Attributable to Common Stockholders per Share (Tables)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	For purposes of the diluted net loss attributable to common stockholders per share calculation, redeemable convertible preferred stock, outstanding stock options, unvested restricted stock awards and warrants to purchase common stock are considered to be potentially dilutive securities, however the following weighted-average amounts were excluded from the calculation of diluted net loss attributable to common stockholders per share because their effect would be anti-dilutive (in thousands): As of March 31, 2021 2020 Redeemable convertible preferred stock (as converted) 18,280 5,615 Outstanding stock options 2,401 193 Unvested restricted common stock 498 886 Warrants to purchase common stock 59 59 Total 21,238 6,753

Description of Business, Orga_2

Description of Business, Organization, and Liquidity (Details) - USD ($) $ / shares in Units, $ in Thousands	May 04, 2021	Mar. 31, 2021	Dec. 31, 2020
Subsidiary, Sale of Stock [Line Items]
Cash and cash equivalents		$ 84,602	$ 92,570
IPO | Subsequent Event
Subsidiary, Sale of Stock [Line Items]
Gross proceeds from the IPO	$ 120,000
Net proceeds from the IPO	$ 108,900
Aggregate shares converted (shares)	18,279,712
IPO | Common Stock | Subsequent Event
Subsidiary, Sale of Stock [Line Items]
Shares issued in IPO (shares)	7,500,000
Price per share (in usd per share)	$ 16

Financial Instruments and Fai_3

Financial Instruments and Fair Value Measurements (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020	Jun. 01, 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			$ 7,800,000	$ 7,300,000	$ 7,800,000
Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	$ 84,602,000	$ 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	84,602,000	92,570,000
Quoted Price in Active Markets (Level 1) | Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	84,602,000	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	84,602,000	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 Thousands	Mar. 31, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Abstract]
Non-current restricted cash	$ 298	$ 207

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Manufacturing	$ 1,166	$ 1,741
Employee compensation and benefits	381	990
Professional fees	832	654
Contract research	123	107
Other	388	94
Total accrued expenses	$ 2,890	$ 3,586

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock (Details) $ / shares in Units, $ in Millions	May 04, 2021shares	Jun. 01, 2020USD ($)$ / sharesshares	Mar. 31, 2021USD ($)member_of_Board_of_Directors$ / sharesshares	Dec. 31, 2020shares	Dec. 31, 2019USD ($)shares	Dec. 30, 2019USD ($)
Class of Stock [Line Items]
Redeemable convertible preferred stock issued (shares)					48,675,140
Preferred stock tranche liability | $		$ 7.8			$ 7.3	$ 7.8
Voting rights, minimum shares outstanding required (shares)			15,000,000
Gross cash proceeds upon conversion (at least) | $			$ 75
Conversion rights, minimum initial offering price to the public (in usd per share) | $ / shares			$ 24.01
Protective provisions, minimum shares outstanding threshold (shares)			20,000,000
Series A Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Redeemable convertible preferred stock authorized (shares)			80,247,000	80,247,000
Redeemable convertible preferred stock issued (shares)			80,246,565	80,247,000
Redeemable convertible preferred stock outstanding (shares)			80,246,565	80,247,000
Price per share (in usd per share) | $ / shares			$ 0.70
Cash proceeds from issuance | $			$ 44
Issuance costs | $			0.2
Outstanding convertible notes exchanged, including interest | $			$ 12
Dividend rate entitled (in usd per share) | $ / shares			$ 0.056
Number of members of Company's Board of Directors that can be elected | member_of_Board_of_Directors			4
Liquidation preference (greater than) (in usd per share) | $ / shares			$ 0.70
Redemption rights, initial offering price to the public (greater than) (in usd per share) | $ / shares			$ 0.70
Series A Redeemable Convertible Preferred Stock | Second Closing
Class of Stock [Line Items]
Price per share (in usd per share) | $ / shares		$ 0.70
Shares issued in IPO (shares)		31,571,425
Series B Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Redeemable convertible preferred stock authorized (shares)			78,222,173	78,222,000
Redeemable convertible preferred stock issued (shares)			78,222,173	78,222,000
Redeemable convertible preferred stock outstanding (shares)			78,222,173	78,222,000
Price per share (in usd per share) | $ / shares			$ 0.92
Cash proceeds from issuance | $			$ 71.8
Issuance costs | $			$ 0.3
Dividend rate entitled (in usd per share) | $ / shares			$ 0.0737
Number of members of Company's Board of Directors that can be elected | member_of_Board_of_Directors			2
Liquidation preference (greater than) (in usd per share) | $ / shares			$ 0.92
Stockholders' vote or written consent threshold (percent)			67.00%
Redemption rights, initial offering price to the public (greater than) (in usd per share) | $ / shares			$ 0.92
Protective provisions, majority vote approvals needed (greater than) (percent)			67.00%
Subsequent Event | IPO
Class of Stock [Line Items]
Aggregate shares converted (shares)	18,279,712

Term Loan (Details)

Term Loan (Details) - Term loan - USD ($)	1 Months Ended	11 Months Ended
	May 31, 2020	Mar. 31, 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 Stock (Details)

Common Stock (Details) - shares shares in Thousands	Mar. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Common stock available for issuance (shares)	20,740	20,398
Redeemable convertible preferred stock outstanding
Class of Stock [Line Items]
Common stock available for issuance (shares)	18,280	18,280
Options issued and outstanding
Class of Stock [Line Items]
Common stock available for issuance (shares)	2,401	2,059
Warrants issued and outstanding
Class of Stock [Line Items]
Common stock available for issuance (shares)	59	59

Stock-based Compensation - Narr

Stock-based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock available for issuance (shares)	20,740,000		20,398,000
Weighted-average grant date fair value of awards (in usd per share)	$ 4,230,000	$ 1,120,000
Aggregate intrinsic fair value of options exercised	$ 0.1	$ 0
Share-based compensation expense not yet recognized	$ 6.2
2017 Stock Incentive Plan (the “Plan”)
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock available for issuance (shares)	28,893
Common Stock | 2017 Stock Incentive Plan (the “Plan”)
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (shares)	3,728,307
Unvested restricted common stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense not yet recognized	$ 0.8
Share-based compensation not yet recognized, recognition period	2 years
Aggregate fair value of awards that vested	$ 0.3	$ 0.1
Stock options
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation not yet recognized, recognition period	3 years 7 months 6 days

Stock-based Compensation - Expe

Stock-based Compensation - Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 539	$ 57
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	140	35
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 399	$ 22

Stock-based Compensation - Rest

Stock-based Compensation - Restricted Stock Award Activity (Details) - Unvested restricted common stock shares in Thousands	3 Months Ended
	Mar. 31, 2021$ / sharesshares
Shares/Units
Unvested at beginning of period (shares) | shares	562
Granted (shares) | shares	0
Vested (shares) | shares	(64)
Forfeited (shares) | shares	0
Unvested at end of period (shares) | shares	498
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	1.53
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
	Mar. 31, 2021	Mar. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Risk-free interest rate	0.80%	0.90%
Expected term (in years)	6 years	6 years
Dividend yield	0.00%	0.00%
Expected volatility	79.80%	86.30%

Stock-based Compensation - Stoc

Stock-based Compensation - Stock Option Activity (Details) - $ / shares shares in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Number of Options
Outstanding at beginning of period (shares)	2,059
Granted (shares)	356
Exercised (shares)	(13)
Cancelled (shares)	0
Outstanding at end of period (shares)	2,402	2,059
Exercisable at end of period (shares)	54
Weighted-Average Exercise Price
Weighted-Average Exercise Price - Outstanding at beginning of period (in usd per share)	$ 3.79
Weighted-Average Exercise Price - Granted (in usd per share)	6.22
Weighted-Average Exercise Price - Exercised (in usd per share)	1.56
Weighted-Average Exercise Price - Cancelled (in usd per share)	0
Weighted-Average Exercise Price - Outstanding at end of period (in usd per share)	4.16	$ 3.79
Weighted-Average Exercise Price - Exercisable at end of period (in usd per share)	$ 3.25
Weighted-Average Remaining Contractual Life (in years)
Weighted Average Remaining Contractual Life - Outstanding	9 years 6 months 29 days	9 years 9 months 3 days
Weighted Average Remaining Contractual Life - Exercisable	9 years 1 month 20 days

Related Parties (Details)

Related Parties (Details) - USD ($)	1 Months Ended	3 Months Ended
	Dec. 31, 2019	Mar. 31, 2021	Mar. 31, 2020
Related Party Transaction [Line Items]
Options granted (shares)		356,000
Exercise price (in usd per share)		$ 6.22
Total stock-based compensation		$ 539,000	$ 57,000
MPM Capital | Management Services
Related Party Transaction [Line Items]
General and administrative expenses		0	8,000
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		$ 3,000	$ 3,000
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 Attributable to Comm_3

Net Loss Attributable to Common Stockholders per Share (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	21,238,000	6,753,000
Redeemable convertible preferred stock (as converted)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	18,280,000	5,615,000
Options issued and outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	2,401,000	193,000
Unvested restricted common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	498,000	886,000
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	59,000	59,000

Subsequent Events (Details)

Subsequent Events (Details) $ / shares in Units, $ in Millions	Apr. 23, 2021	Jun. 10, 2021USD ($)ft²	May 04, 2021$ / sharesshares	Mar. 31, 2021$ / sharesshares	Dec. 31, 2020$ / sharesshares
Subsequent Event [Line Items]
Common stock authorized (shares) | shares				196,000,000	193,500,000
Common stock par value (usd per share) | $ / shares				$ 0.0001	$ 0.0001
Subsequent Event
Subsequent Event [Line Items]
Common stock authorized (shares) | shares			200,000,000
Common stock par value (usd per share) | $ / shares			$ 0.0001
Preferred stock authorized (shares) | shares			5,000,000
Preferred stock par value (usd per share) | $ / shares			$ 0.0001
Laboratory and office space to be rented (in sqft) | ft²		25,778
Lease term		8 years
Total estimated base rent payments to be made over term of lease | $		$ 17.9
Security deposit provided | $		$ 1
Subsequent Event | Common Stock
Subsequent Event [Line Items]
Reverse stock split conversion ratio	0.115352228028284000