0001785530-24-000028 | 10-Q | XBRL Viewer | Werewolf Therapeutics INC

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Financial Instruments and Fair Value Measurements - Unobservable Inputs (Details)	Jun. 30, 2024 $ / shares Term	May 02, 2024 $ / shares Term
Stock Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input \| $ / shares	2.44	6.08
Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	1.010	1.010
Risk-free rate (continuous)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.045	0.047
Expected term (in years)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input \| Term	0.0075	0.0091
Dividend yield (continuous)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0	0

Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2024
Accounting Policies [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements as of June 30, 2024 and December 31, 2023, and for the three and six months ended June 30, 2024 and 2023, 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 our financial position and results of our 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 our Annual Report on Form 10-K for the year ended December 31, 2023 filed with the SEC on March 7, 2024 (the “2023 Annual Report”).
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. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, those related to revenue recognition, accrued expenses, assumptions used in the valuation of stock-based compensation expense and the fair value of the derivative liability, and income taxes. Actual results could differ from those estimates.
Recently Adopted Accounting Pronouncements and Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging Contracts in Entity’s Own Equity (Subtopic 815-40) (“ASU No. 2020-06”), which reduces the number of accounting models for convertible debt instruments and convertible preferred stock as well as amends the derivatives scope exception for contracts in an entity’s own equity. ASU No. 2020-06 also simplifies the diluted earnings per share calculation in certain areas. We adopted ASU No. 2020-06 on January 1, 2024. The adoption did not have a material impact on the condensed consolidated financial statements. Recent Accounting Pronouncements In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures (“ASU No. 2023-09”), which enhances the transparency and decision usefulness of income tax disclosures primarily related to rate reconciliation and income taxes paid. The provisions of ASU No. 2023-09 are effective for fiscal years beginning after December 15, 2024, with early adoption permitted, and are required to be applied on a prospective basis. Our management is currently evaluating the impact that this standard will have on our consolidated financial statements. Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on our consolidated financial statements upon adoption.
Subsequent Events	Subsequent Events We have evaluated subsequent events and transactions that occurred after the balance sheet date up to the date that the financial statements were issued. Other than as described in these condensed consolidated financial statements, we did not identify any subsequent events that require adjustment or disclosure in the condensed consolidated financial statements.

Stock-based Compensation - Stock Option Activity (Details) - Outstanding stock options - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2024
Number of Options
Outstanding at beginning of period (in shares)	5,700,070
Granted (in shares)	2,205,112
Exercised (in shares)	(6,099)
Cancelled (in shares)	(389,050)
Outstanding at end of period (in shares)	7,510,033
Exercisable at end of period (in shares)	4,100,266
Weighted-Average Exercise Price per Share
Weighted-Average Exercise Price - Outstanding at beginning of period (in usd per share)	$ 6.89
Weighted-Average Exercise Price - Granted (in usd per share)	4.66
Weighted-Average Exercise Price - Exercised (in usd per share)	2.05
Weighted-Average Exercise Price - Cancelled (in usd per share)	5.06
Weighted-Average Exercise Price - Outstanding at end of period (in usd per share)	6.33
Weighted-Average Exercise Price - Exercisable at end of period (in usd per share)	$ 7.25
Weighted-Average Remaining Contractual Life (in years)
Weighted Average Remaining Contractual Life - Outstanding	7 years 10 months 6 days
Weighted Average Remaining Contractual Life - Exercisable	7 years 1 month 2 days
Outstanding, Aggregate Intrinsic Value	$ 0.8
Exercisable, Aggregate Intrinsic Value	$ 0.5

Nature of Business	6 Months Ended
Nature of Business	Jun. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	1. Nature of Business Werewolf Therapeutics, Inc. was incorporated in the state of Delaware in October 2017. As used throughout these unaudited, condensed consolidated financial statements, the terms “Werewolf,” “we,” “us,” and “our” refer to the business of Werewolf Therapeutics, Inc., and its wholly owned subsidiary. We are an innovative biopharmaceutical company pioneering the development of therapeutics engineered to stimulate the body’s immune system for the treatment of cancer. Our headquarters are located in Watertown, Massachusetts. Since inception, we have devoted substantially all of our efforts and financial resources to organizing and staffing the company; business planning; raising capital; developing and optimizing our platform technology; identifying potential product candidates; enhancing our intellectual property portfolio; undertaking research, preclinical studies, and clinical trials; and enabling manufacturing for our development programs. We are 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 our product development efforts are successful, it is uncertain when, if ever, we will realize significant revenue from product sales. We had cash and cash equivalents of $135.3 million at June 30, 2024. We expect that our cash and cash equivalents will enable us to fund our operating expenses and capital expenditure requirements for at least twelve months from the date of issuance of the condensed consolidated financial statements in this Form 10-Q. However, additional funding will be necessary beyond this point to fund future preclinical and clinical activities. We expect to finance our future cash needs through a combination of equity or debt financings, collaboration agreements, strategic alliances and licensing arrangements.

Financial Instruments and Fair Value Measurements - Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2024 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivative liabilities, beginning balance	$ 0
Derivative liabilities, ending balance	2,841
Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivative liabilities, ending balance	2,841
Level 3 \| Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivative liabilities, beginning balance	0
Fair value of embedded derivative at issuance of term loan	4,450
Change in fair value	(1,609)
Derivative liabilities, ending balance	$ 2,841

- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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+ Details

Net (Loss) Income Attributable to Common Stockholders per Share - Antidilutive Shares (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Earnings Per Share [Abstract]
Net loss	$ (17,249)	$ (5,098)	$ (33,442)	$ (17,080)
Less: Change in fair value of derivative liability	(1,609)	0	(1,609)	0
Plus: Interest expense on converted term loan	120	0	120	0
Adjusted net loss	$ (18,738)	$ (5,098)	$ (34,931)	$ (17,080)
Weighted-average common shares outstanding, basic (in shares)	43,521,406	35,557,701	42,564,342	35,173,327
Dilutive effect of common stock issuable from assumed conversion of convertible term loan (in shares)	521,778	0	260,889	0
Weighted -average common shares outstanding, diluted (in shares)	44,043,184	35,557,701	42,825,231	35,173,327
Net loss per share, basic (in usd per share)	$ (0.40)	$ (0.14)	$ (0.79)	$ (0.49)
Net loss per share, diluted (in usd per share)	$ (0.43)	$ (0.14)	$ (0.82)	$ (0.49)

Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Abstract]

Schedule of Stock-based Compensation Expense Recognized

Total stock-based compensation expense recognized in the condensed consolidated statements of operations was as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
	(in thousands)
Research and development	$	1,516	$	1,019	$	2,698	$	2,039
General and administrative	1,086		911		2,209		1,999
Total stock-based compensation	$	2,602	$	1,930	$	4,907	$	4,038

Schedule of Restricted Stock Awards Activity

The following table summarizes RSU activity during the six months ended June 30, 2024:


	Shares/Units	Weighted-Average Grant Date Fair Value Per Share
	(in thousands)
Unvested at December 31, 2023	361,500	$	3.92
Granted	—	$	—
Vested	(211,500)	$	4.97
Forfeited	—	$	—
Unvested at June 30, 2024	150,000	$	2.45

Schedule of Weighted -average Valuation Assumptions

The fair value of stock options granted during the three and six months ended June 30, 2024 and 2023 was calculated on the date of grant using the following weighted-average assumptions:


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Risk-free interest rate	4.5	%	3.8	%	4.0	%	3.9	%
Expected term (in years)	5.5		5.7		6.0		6.0
Expected annual dividend yield	—	%	—	%	—	%	—	%
Expected volatility	92.6	%	82.6	%	92.6	%	82.6	%

Summary of Stock Option Activity

The following table summarizes stock option activity during the six months ended June 30, 2024:


	Options Outstanding
	Number of Options	Weighted-Average Exercise Price per Share		Weighted-Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2023	5,700,070	$	6.89
Granted	2,205,112	$	4.66
Exercised	(6,099)	$	2.05
Cancelled	(389,050)	$	5.06
Outstanding at June 30, 2024	7,510,033	$	6.33	7.85	$	0.8
Exercisable at June 30, 2024	4,100,266	$	7.25	7.09	$	0.5

Net Loss Attributable to Common Stockholders per Share (Tables)

6 Months Ended

Jun. 30, 2024

Earnings Per Share [Abstract]

Schedule of Antidilutive Securities Excluded from Computation of (Loss) Income per Share

For purposes of the diluted net loss attributable to common stockholders per share calculation, outstanding stock options, unvested RSAs, unvested RSUs, conversion option derivative under the K2HV Loan Agreement, and warrants to purchase common stock are considered to be potentially dilutive securities, however the following outstanding shares of common stock equivalents were excluded from the calculation of diluted net loss attributable to common stockholders per share because their effect would be anti-dilutive:


	June 30,
	2024	2023
Outstanding stock options	7,510,033	6,745,934
Unvested RSUs	150,000	316,500
Warrants to purchase common stock	58,904	58,904
Common stock to be issued under the 2021 ESPP	36,767	18,366

Total	7,755,704	7,139,704

Schedule of Calculation of Basic and Diluted Net (Loss) Income per Share


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Numerator
Net loss	$	(17,249)	$	(5,098)	$	(33,442)	$	(17,080)
Less: Change in fair value of derivative liability	(1,609)		—		(1,609)		—
Plus: Interest expense on converted term loan	120		—		120		—
Adjusted net loss	$	(18,738)	$	(5,098)	$	(34,931)	$	(17,080)
Denominator
Weighted-average common stock outstanding, basic	43,521,406		35,557,701		42,564,342		35,173,327
Dilutive effect of common stock issuable from assumed conversion of convertible term loan	521,778		—		260,889		—
Weighted-average common stock outstanding, diluted	44,043,184		35,557,701		42,825,231		35,173,327
Net loss per share
Basic	$	(0.40)	$	(0.14)	$	(0.79)	$	(0.49)
Diluted	$	(0.43)	$	(0.14)	$	(0.82)	$	(0.49)

Term Loan - Schedule of Interest Expense (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2024 USD ($)
Debt Disclosure [Abstract]
Interest expense based on coupon interest rate (10.3%) of outstanding term loans	$ 515	$ 515
Accretion of debt discount and Final Fee (8.94%)	285	285
Total interest expense on effective rate (19.24%)	$ 800	$ 800
Coupon rate (as a percent)	10.30%	10.30%
Accretion of debt discount (as a percent)	8.94%	8.94%
Effective interest rate (percent)	19.24%	19.24%

Stock-based Compensation - Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 2,602	$ 1,930	$ 4,907	$ 4,038
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	1,516	1,019	2,698	2,039
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 1,086	$ 911	$ 2,209	$ 1,999

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Operating activities:
Net loss	$ (33,442)	$ (17,080)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	4,907	4,038
Depreciation expense	918	859
Non-cash interest expense	410	92
Non-cash lease expense	541	675
Loss on extinguishment of debt	553	0
Change in fair value of derivative liabilities	(1,609)	(1,030)
Amortization of debt issuance costs	0	60
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(474)	863
Other receivables	805	1
Other non-current assets	329	0
Accounts payable, accrued expenses and other liabilities	15	(3,017)
Deferred revenue	(1,340)	(5,271)
Operating lease liability	(1,087)	(1,009)
Net cash used in operating activities	(29,474)	(20,819)
Investing activities:
Purchases of property and equipment	(128)	(350)
Net cash used in investing activities	(128)	(350)
Financing activities:
Proceeds from at the market offering of common stock, net of issuance costs	21,124	9,265
Proceeds from drawdown of term loans	30,000	40,000
Payment of debt issuance costs	(673)	0
Repayment of term loan	(40,000)	0
Proceeds from issuances under Employee Stock Purchase Plan	76	45
Proceeds from stock option exercises	12	5
Net cash provided by financing activities	10,539	49,315
Net (decrease) increase in cash, cash equivalents and restricted cash and cash equivalents	(19,063)	28,146
Cash, cash equivalents and restricted cash and cash equivalents—beginning of period	155,577	130,529
Cash, cash equivalents and restricted cash and cash equivalents—end of period	136,514	158,675
Reconciliation of cash, cash equivalents and restricted cash and cash equivalents to the condensed consolidated balance sheets
Cash and cash equivalents	135,303	137,452
Prepaid expenses and other current assets	0	208
Restricted cash and cash equivalents, net of current portion	1,211	21,015
Cash, cash equivalents and restricted cash and cash equivalents	136,514	158,675
Supplemental disclosure of cash flow information:
Cash paid for interest	1,788	742
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property and equipment in accounts payable and accrued expenses	0	13
Issuance costs in accounts payable and accrued expenses	69	15
Fair value of derivative liability issued with term loan	$ 4,450	$ 0

Financial Instruments and Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Liabilities:
Derivative liability	$ 2,841	$ 0
Recurring
Assets:
Total assets	129,881	149,294
Liabilities:
Derivative liability	2,841
Total liabilities	2,841
Money market funds \| Recurring
Assets:
Money market funds	129,881	149,294
Level 1 \| Recurring
Assets:
Total assets	129,881	149,294
Liabilities:
Derivative liability	0
Total liabilities	0
Level 1 \| Money market funds \| Recurring
Assets:
Money market funds	129,881	149,294
Level 2 \| Recurring
Assets:
Total assets	0	0
Liabilities:
Derivative liability	0
Total liabilities	0
Level 2 \| Money market funds \| Recurring
Assets:
Money market funds	0	0
Level 3 \| Recurring
Assets:
Total assets	0	0
Liabilities:
Derivative liability	2,841	0
Total liabilities	2,841
Level 3 \| Money market funds \| Recurring
Assets:
Money market funds	$ 0	$ 0

Related Parties (Details) - USD ($) $ in Millions	6 Months Ended
Related Parties (Details) - USD ($) $ in Millions	Jun. 30, 2024	Jun. 30, 2022
Related Party Transactions [Abstract]
Sublease cash payments received	$ 0.4
Security deposit liability		$ 0.2

Common and Preferred Stock - Narrative (Details)		6 Months Ended
Common and Preferred Stock - Narrative (Details)	Feb. 09, 2024 USD ($)	Jun. 30, 2024 USD ($) $ / shares shares	Jun. 30, 2023 USD ($) $ / shares shares	Dec. 31, 2023 shares	May 10, 2022 USD ($)
Class of Stock [Line Items]
Common stock authorized (in shares) \| shares		200,000,000		200,000,000
Dividends declared \| $		$ 0
Proceeds from at the market offering of common stock, net of issuance costs \| $		$ 21,124,000	$ 9,265,000
Preferred stock authorized (in shares) \| shares		5,000,000		5,000,000
Preferred stock outstanding (in shares) \| shares		0		0
Preferred stock issued (in shares) \| shares		0		0
ATM Offering
Class of Stock [Line Items]
Sales commissions, percentage					0.030
Sale of stock increase in offering amount \| $	$ 25,000,000.0
Issuance of common stock from at the market offering, net of issuance costs (in shares) \| shares		4,342,320	4,096,281
Price per share (in usd per share) \| $ / shares		$ 5.11	$ 2.36
Proceeds from at the market offering of common stock, net of issuance costs \| $		$ 21,100,000	$ 9,300,000
ATM Offering \| Maximum
Class of Stock [Line Items]
Common stock, amount authorized \| $	$ 75,000,000.0				$ 50,000,000.0

Cover - shares	6 Months Ended
Cover - shares	Jun. 30, 2024	Aug. 02, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2024
Document Transition Report	false
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	200 Talcott Ave
Entity Address, Address Line Two	2nd Floor
Entity Address, City or Town	Watertown
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02472
City Area Code	617
Local Phone Number	952‑0555
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	HOWL
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
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 Shell Company	false
Entity Common Stock, Shares Outstanding		43,702,147
Entity Central Index Key	0001785530
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
Amendment Flag	false

Condensed Consolidated Statements of Operations (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Revenue:
Collaboration revenue	$ 1,143	$ 8,081	$ 1,885	$ 12,545
Operating expenses:
Research and development	15,271	9,583	28,179	21,289
General and administrative	4,832	4,565	9,828	9,546
Total operating expenses	20,103	14,148	38,007	30,835
Operating loss	(18,960)	(6,067)	(36,122)	(18,290)
Other income:
Interest income	1,793	1,949	3,766	3,467
Interest expense	(1,142)	(955)	(2,145)	(1,126)
Loss on extinguishment of debt	(553)	0	(553)	0
Other income (expense), net	1,613	(25)	1,612	(1,131)
Total other income	1,711	969	2,680	1,210
Net loss	$ (17,249)	$ (5,098)	$ (33,442)	$ (17,080)
Net loss per share attributable to common stockholders, basic and diluted
Net loss per common share, basic (in usd per share)	$ (0.40)	$ (0.14)	$ (0.79)	$ (0.49)
Net loss per common share, diluted (in usd per share)	$ (0.43)	$ (0.14)	$ (0.82)	$ (0.49)
Weighted-average common shares outstanding, basic and diluted
Weighted-average common shares outstanding, basic (in shares)	43,521,406	35,557,701	42,564,342	35,173,327
Weighted -average common shares outstanding, diluted (in shares)	44,043,184	35,557,701	42,825,231	35,173,327

Collaboration and License Agreement

6 Months Ended

Jun. 30, 2024

Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]

Collaboration and License Agreement

3. Collaboration and License Agreement

Detailed description of the contractual terms and our accounting for the agreement described below is included in our audited financial statements and notes in the 2023 Annual Report.

During the six months ended June 30, 2024, we continued to perform under our exclusive global collaboration and license agreement (the “Collaboration Agreement”) with Jazz Pharmaceuticals Ireland Limited ("Jazz"), pursuant to which we recognized revenue utilizing the cost-to-cost input method, which best depicts the research and development services performed for the customer. Revenue from the transaction price was recognized over time as research and development services were performed. In June 2024, we executed a transfer agreement (the “Transfer Agreement”) to assign our rights in a development agreement with a contract manufacturer of our interferon alpha INDUKINE molecule JZP898 to Jazz. The execution of this Transfer Agreement was the last material performance obligation required of us under the Collaboration Agreement. As of the execution of the Transfer Agreement, we no longer have any material performance obligations under the Collaboration Agreement. As a result, during the three months ended June 30, 2024, all remaining deferred revenue related to the Collaboration Agreement has been recognized. The following table summarizes research and development costs incurred and revenue recognized in connection with our performance under the Collaboration Agreement:


	Three Months Ended June 30,		Six Months Ended June 30,
	2024	2023	2024	2023
	(in thousands)		(in thousands)
Revenue recognized	1,143	8,081	1,885	12,545
Cost incurred	210	5,152	545	7,273

The following table presents changes in our contract liabilities during the six months ended June 30, 2024:


	Balance as of December 31, 2023		Additions		Reductions		Balance as of June 30, 2024
	(in thousands)
Contract liabilities:
Deferred revenue	$	1,340	$	—	$	(1,340)	$	—
Total contract liabilities	$	1,340	$	—	$	(1,340)	$	—

All deferred revenue related to the Collaboration Agreement has been recognized as of June 30, 2024

Unbilled receivables related to the Collaboration Agreement of $0.2 million and $0.4 million are included within other receivables in the accompanying condensed consolidated balance sheets as of June 30, 2024 and December 31, 2023, respectively. Receivables related to the Collaboration Agreement of $0.3 million and $0.9 million are included within other receivables in the accompanying condensed consolidated balance sheets as of June 30, 2024 and December 31, 2023, respectively. Revenue recognized during the six months ended June 30, 2024 and 2023, includes $1.3 million and $5.3 million of revenue that was included in deferred revenue as of December 31, 2023 and 2022, respectively.

At the end of each reporting period, we re-evaluate our estimate of the transaction price associated with the Collaboration Agreement and determine if variable consideration previously excluded from the transaction should be included in the transaction price based on changes in circumstances, if any. During the six months ended June 30, 2024 and 2023, we did not recognize any adjustment to the transaction price associated with variable consideration previously excluded from the transaction price. As of June 30, 2024, we have not received any royalty payments under the Collaboration Agreement.

Common and Preferred Stock (Tables)

6 Months Ended

Jun. 30, 2024

Equity [Abstract]

Schedule of Common Stock Reserved for Issuance

We have reserved shares of common stock for issuance as follows:


	As of June 30,	As of December 31,
	2024	2023
Shares reserved for exercises of outstanding stock options	7,510,033	5,700,070
Shares reserved for vesting of restricted stock units	150,000	361,500
Shares reserved for exercises of warrants	58,904	58,904
Shares reserved for future issuance under the 2021 Employee Stock Purchase Plan	471,933	507,113
Shares reserved for future issuance under the 2021 Stock Incentive Plan	2,050,950	1,911,660
Shares reserved for future issuance as part of K2HV conversion feature	791,364	—
Total shares reserved for future issuance	11,033,184	8,539,247

Collaboration and License Agreement - Narrative (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognized that was included in prior period deferred revenue	$ 1.3	$ 5.3
Unbilled Accounts Receivables
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract with customer, asset, after allowance for credit loss	0.2		$ 0.4
Accounts Receivable
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract with customer, asset, after allowance for credit loss	$ 0.3		$ 0.9

Stock-based Compensation - Weighted Average Assumptions (Details) - Outstanding stock options	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Risk-free interest rate	4.50%	3.80%	4.00%	3.90%
Expected term (in years)	5 years 6 months	5 years 8 months 12 days	6 years	6 years
Expected annual dividend yield	0.00%	0.00%	0.00%	0.00%
Expected volatility	92.60%	82.60%	92.60%	82.60%

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Payables and Accruals [Abstract]
Contract research	$ 2,845	$ 1,049
Manufacturing	2,418	2,772
Employee compensation and benefits	2,274	3,627
Professional fees	847	655
Accrued interest	258	310
Other	59	447
Total accrued expenses and other current liabilities	$ 8,701	$ 8,860

Term Loan - Schedule of Total Principle Payments Maturities (Details) $ in Thousands	Jun. 30, 2024 USD ($)
Long-Term Debt, Fiscal Year Maturity [Abstract]
2024 (remaining as of June 30, 2024)	$ 0
2025	0
2026	9,600
2027	14,400
2028	8,085
Total principal payments and Final Fee	$ 32,085

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details

Term Loan

6 Months Ended

Jun. 30, 2024

Debt Disclosure [Abstract]

Term Loan

6. Term Loan

PWB Loan Agreement

In April 2022, we entered into the PWB Loan Agreement with PWB and subsequently drew down an aggregate of $40.0 million in term loans. The term loans accrued interest on the outstanding daily balance at a floating annual rate equal to greater of: (i) 0.5% above the prime rate then in effect or (ii) 4.5%. If the prime rate changed throughout the term, the interest rate would be adjusted effective on the date of the prime rate change. All interest chargeable under the PWB Loan Agreement was computed on a 360-day year for the actual number of days elapsed, with interest payable monthly. We recognized interest expense related to the PWB Loan Agreement of $0.3 million and $0.9 million during the three months ended June 30, 2024 and 2023, respectively.

In May 2024, we repaid all amounts outstanding under the PWB Loan Agreement, using $29.5 million in net loan proceeds received under the K2HV Loan Agreement, as described below at Note 6, together with $10.5 million in existing cash. We recognized a total loss on extinguishment of debt in the amount of $0.6 million in the six months ended June 30, 2024 primarily due to the write off of unamortized debt issuance costs.

K2HV Loan Agreement

In May 2024, we, as borrower, entered into the K2HV Loan Agreement with K2HV (together with any other lender from time to time, the “Lenders”); K2HV, as administrative agent for the Lenders; and Ankura Trust Company, LLC, as collateral trustee for the Lenders. The K2HV Loan Agreement provides up to $60.0 million principal in term loans. We received $30.0 million in gross loan proceeds at closing, $25.0 million from the first tranche commitment upon closing and $5.0 million from the second tranche commitment. A third tranche commitment of up to $10.0 million is available to be drawn at our option between January 1, 2025 and June 30, 2025, subject to the achievement, as determined by the administrative agent in its discretion, of certain time-based, clinical and regulatory milestones and receipt of not less than $60.0 million in net cash proceeds from certain financing activities, with at least $50.0 million from a single offering of common stock. A fourth tranche commitment of up to $20.0 million is available to be drawn down at our option through May 1, 2026 or if the third tranche is funded, May 1, 2027, subject to Lender’s review of our clinical, financial and operating plan and subject to the Lender’s consent in its sole and absolute discretion.

The term loan matures on May 1, 2028, and we are obligated to make interest only payments for the first 24 months, or 36 months if the third tranche is funded, and then interest and equal principal payments each month thereafter through the maturity date. The term loan bears a variable interest rate equal to the greater of (i) 10.3%, and (ii) the sum of (A) the prime rate last quoted in The Wall Street Journal (or a comparable replacement rate if The Wall Street Journal ceases to quote such rate) and (B) 1.8%. We may prepay, at our option, all, but not less than all, of the outstanding principal balance and all accrued and unpaid interest with respect to the principal balance being prepaid of the term loans, subject to a prepayment premium to which the Lenders are entitled and certain notice requirements. We are obligated to pay a final fee equal to 6.95% of the aggregate amount of the term loans funded, or the Final Fee, to occur upon the earliest of (i) the maturity date, (ii) the acceleration of the term loans, and (iii) the prepayment of the term loans. The Final Fee is being accreted to interest expense using the effective interest method over the life of the debt.

The Lenders may elect prior to the full repayment of the term loans to convert up to $5.0 million of outstanding principal of the term loans into shares of our common stock, pursuant to the Fixed Price Conversion or the Variable Price Conversion, subject to customary adjustments and 9.99% and 19.99% beneficial ownership limitations. There will be no prepayment penalty for any principal amount converted into common stock. We determined that the Fixed Price Conversion and the Variable Price

Conversion within the K2HV Loan Agreement are required to be bifurcated as an embedded derivative under ASC 815 at fair value, and recorded as a discount on the debt on the date of issuance, with subsequent changes in fair value recognized in the accompanying consolidated statements of operations. See Note 4 for further discussion on this derivative instrument.

As security for our obligations under the K2HV Loan Agreement, we granted the Lenders a first priority security interest on substantially all of our assets (other than intellectual property), subject to certain exceptions. The K2HV Loan Agreement contains customary representations and warranties, events of default and affirmative and negative covenants, including covenants that limit or restrict our ability to, among other things, dispose of assets, make changes to the our business, management, ownership or business locations, merge or consolidate, incur additional indebtedness, incur additional liens, pay dividends or other distributions or repurchase equity, make investments, and enter into certain transactions with affiliates, in each case subject to certain exceptions. Upon the occurrence of an event of default, a default interest rate of an additional 5.0% per annum may be applied to the outstanding loan balances, and the Lenders may declare all outstanding obligations immediately due and payable and exercise all of their rights and remedies as set forth in the K2HV Loan Agreement and under applicable law. As of June 30, 2024, we are in compliance with all covenants.

Subject to certain conditions, we granted the Lenders the right, prior to repayment of the term loans, to invest up to $5.0 million in the aggregate in future offerings of capital stock, at market terms, subject to certain exceptions and conditions.

We incurred debt issuance costs of $0.7 million in connection with the term loans, composed of the facility fee of $0.4 million and other expenses paid to the Lenders of $0.2 million and external legal fees of $0.1 million. These debt issuance costs, together with fair value of the embedded derivative of $4.5 million, resulted in a debt discount of $5.1 million which is being amortized to interest expense over the term of the K2HV Loan Agreement using the effective interest method.

The outstanding term loans payable consists of the following:


	June 30, 2024
	(in thousands)
Term loans	$	30,000
Unamortized debt discount	(4,837)
Total debt, long-term	$	25,163

The following table provides the components of interest expense related to the K2HV Loan Agreement:


	Three Months Ended June 30, 2024		Six Months Ended June 30, 2024
	(in thousands)
Interest expense based on coupon interest rate (10.3%) of outstanding term loans	$	515	$	515
Accretion of debt discount and Final Fee (8.94%)	285		285
Total interest expense on effective rate (19.24%)	$	800	$	800

The following table presents the total principal payments and Final Fee schedules to become due during each of the years ended December 31:


	Principal Payments and Final Fee
	(in thousands)
2024 (remaining as of June 30, 2024)	$	—
2025	—
2026	9,600
2027	14,400
2028	8,085
Total principal payments and Final Fee	$	32,085

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477092/405-40-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Subparagraph (a)(3)
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Paragraph 1
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Paragraph 1
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Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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Reference 21: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Condensed Consolidated Statements of Stockholders’ Equity (unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023
Market Offering
Issuance costs	$ 61	$ 985	$ 31	$ 103

Term Loan - Narrative (Details) $ in Thousands		1 Months Ended		3 Months Ended		6 Months Ended
Term Loan - Narrative (Details) $ in Thousands	May 02, 2024	May 31, 2024 USD ($)	Apr. 30, 2022 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)
Debt Instrument [Line Items]
Floating rate spread in effect (greater than) (percent)			4.50%
Proceeds from drawdown of term loans						$ 30,000	$ 40,000
Loss on extinguishment of debt				$ 553	$ 0	553	0
Payment of debt issuance costs						673	$ 0
Level 3 \| Recurring
Debt Instrument [Line Items]
Fair value of embedded derivative at issuance of term loan						4,450
Prime Rate
Debt Instrument [Line Items]
Floating rate spread in effect (greater than) (percent)			0.50%
Term loan
Debt Instrument [Line Items]
Non-cash interest expense				300	$ 900
Proceeds from drawdown of term loans		$ 29,500
Cash used to repay debt		10,500
Loss on extinguishment of debt						600
Term Loans
Debt Instrument [Line Items]
Payment of debt issuance costs		700
Facility fee		400
Payments for other fees and expenses		200
Debt instrument, final fee amount		100
Debt discount		$ 5,100
Term Loans \| Term loan
Debt Instrument [Line Items]
Term loan available			$ 40,000
Debt discount				$ 4,837		$ 4,837
Loan Agreement
Debt Instrument [Line Items]
Floating rate spread in effect (greater than) (percent)		1.80%
Proceeds from drawdown of term loans		$ 30,000
Loan agreement, amount		60,000
Amount of net cash proceeds from certain financing activities		60,000
Minimum amount of offering of common stock		$ 50,000
Final fee, percentage		6.95%
Conversion of outstanding principal		$ 5,000
Additional interest rate (percent)	0.050
Allowable amount to invest in future offerings		$ 5,000
Loan Agreement \| Minimum
Debt Instrument [Line Items]
Adjustment rate (percent)		9.99%
Loan Agreement \| Maximum
Debt Instrument [Line Items]
Adjustment rate (percent)		19.99%
Loan Agreement \| Period One
Debt Instrument [Line Items]
Proceeds from drawdown of term loans		$ 25,000
Period for interest only payments (in months)		24 months
Loan Agreement \| Period Two
Debt Instrument [Line Items]
Proceeds from drawdown of term loans		$ 5,000
Loan Agreement \| Tranche three
Debt Instrument [Line Items]
Capacity available to draw on the term loans		$ 10,000
Period for interest only payments (in months)		36 months
Loan Agreement \| Tranche four
Debt Instrument [Line Items]
Capacity available to draw on the term loans		$ 20,000
Loan Agreement \| Prime Rate
Debt Instrument [Line Items]
Floating rate spread in effect (greater than) (percent)		10.30%

Nature of Business (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 135,303	$ 134,343	$ 137,452

Term Loan (Tables)

6 Months Ended

Jun. 30, 2024

Debt Disclosure [Abstract]

Schedule of Outstanding Term Loans Payable

The outstanding term loans payable consists of the following:


	June 30, 2024
	(in thousands)
Term loans	$	30,000
Unamortized debt discount	(4,837)
Total debt, long-term	$	25,163

Schedule of Interest Expense

The following table provides the components of interest expense related to the K2HV Loan Agreement:


	Three Months Ended June 30, 2024		Six Months Ended June 30, 2024
	(in thousands)
Interest expense based on coupon interest rate (10.3%) of outstanding term loans	$	515	$	515
Accretion of debt discount and Final Fee (8.94%)	285		285
Total interest expense on effective rate (19.24%)	$	800	$	800

Schedule of Total Principal Payments Maturities

The following table presents the total principal payments and Final Fee schedules to become due during each of the years ended December 31:


	Principal Payments and Final Fee
	(in thousands)
2024 (remaining as of June 30, 2024)	$	—
2025	—
2026	9,600
2027	14,400
2028	8,085
Total principal payments and Final Fee	$	32,085

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
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+ Details

Collaboration and License Agreement (Tables)

6 Months Ended

Jun. 30, 2024

Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]

Schedule of Research and Development Costs Incurred and Revenue Recognized

The following table summarizes research and development costs incurred and revenue recognized in connection with our performance under the Collaboration Agreement:


	Three Months Ended June 30,		Six Months Ended June 30,
	2024	2023	2024	2023
	(in thousands)		(in thousands)
Revenue recognized	1,143	8,081	1,885	12,545
Cost incurred	210	5,152	545	7,273

Schedule of Changes in Contract Liabilities

The following table presents changes in our contract liabilities during the six months ended June 30, 2024:


	Balance as of December 31, 2023		Additions		Reductions		Balance as of June 30, 2024
	(in thousands)
Contract liabilities:
Deferred revenue	$	1,340	$	—	$	(1,340)	$	—
Total contract liabilities	$	1,340	$	—	$	(1,340)	$	—

Financial Instruments and Fair Value Measurements

6 Months Ended

Jun. 30, 2024

Fair Value Disclosures [Abstract]

Financial Instruments and Fair Value Measurements

4. Financial Instruments and Fair Value Measurements

Our assets that are required to be measured at fair value on a recurring basis consist of money market funds, classified as cash, cash equivalents and restricted cash and cash equivalents on our condensed consolidated balance sheets as June 30, 2024 and December 31, 2023.

Our liabilities that are required to be measured at fair value on a recurring basis consist of a derivative liability pursuant to a loan and security agreement (the “K2HV Loan Agreement”) with K2 HealthVentures LLC (“K2HV”) (see Note 6, Term Loan) on our condensed consolidated balance sheets as June 30, 2024. We did not have any liabilities that are required to be measured at fair value on a recurring basis as of December 31, 2023.

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 and liabilities measured at fair value on a recurring basis as of June 30, 2024 were as follows:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	129,881	$	—	$	—	$	129,881
Total assets	$	129,881	$	—	$	—	$	129,881

Liabilities:	$	—	$	—	$	2,841	$	2,841
Derivative liability	$	—	$	—	$	2,841	$	2,841

Assets measured at fair value on a recurring basis as of December 31, 2023 were as follows:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	149,294	$	—	$	—	$	149,294
Total assets	$	149,294	$	—	$	—	$	149,294

There were no changes in valuation techniques during the three or six months ended June 30, 2024.

Derivative liabilities

In May 2024, we entered into the K2HV Loan Agreement, as further described in Note 6, which provides up to $60.0 million principal in term loans. Pursuant to the terms of the K2HV Loan Agreement, the lenders thereto may elect, prior to the full repayment of the term loans, to convert up to $5.0 million of the outstanding principal of the term loans into shares of our common stock at a conversion price of the lesser of $6.3182 per share (the “Fixed Price Conversion”) and the lowest effective price per share of our first equity financing following the closing of the K2HV Loan Agreement (the “Variable Price Conversion”), subject to customary adjustments and 9.99% and 19.99% beneficial ownership limitations. The Fixed Price Conversion and Variable Price Conversion within the K2HV Loan Agreement are required to be bifurcated as a single compound embedded derivative at fair value, with subsequent changes in fair value recognized in the statements of operations.

The following table reconciles the change in fair value of the conversion option derivative liability during the six months ended June 30, 2024 based on Level 3 inputs (in thousands):


	Six Months Ended June 30, 2024
Balance at December 31, 2023	$	—
Fair value of embedded derivative at issuance of term loan	4,450
Change in fair value	(1,609)
Balance at June 30, 2024	$	2,841

For the period ended June 30, 2024, the fair value of the conversion option derivative liability in the term loan has been estimated using the Monte Carlo model. A summary of the weighted-average significant unobservable inputs (Level 3 inputs) used in measuring the conversion option derivative liability in the term loan as of June 30, 2024 and May 2, 2024 (inception) is as follows:


	June 30, 2024	May 2, 2024
Stock Price	$2.44	$6.08
Volatility	101.0%	101.0%
Risk-free rate (continuous)	4.5%	4.7%
Expected term (in years)	0.75 yrs	0.91 yrs
Dividend yield (continuous)	—%	—%

Success Payment Liability

In April 2022, we entered into an amended and restated loan and security agreement (the “PWB Loan Agreement”) with Pacific Western Bank (“PWB”), as described below in Note 6. In conjunction with the PWB Loan Agreement, we became obligated to pay to PWB a one-time success payment of up to $1.6 million (the “Success Fee”) upon achieving certain conditions defined in the PWB Loan Agreement (the “Success Fee Event”). The Success Fee Event occurred during the second quarter of 2023, resulting in the immediate payment in full of the required Success Fee.

Prior to the occurrence of the Success Fee Event, we recognized a success payment liability that was stated at fair value and was considered Level 3 because its fair value measurement was based, in part, on significant inputs not observed in the market. Upon completion of the Success Fee Event, we paid the total $1.6 million success payment and removed the corresponding success payment liability. We remeasured the success payment liability at each reporting date and immediately prior to the Success Fee Event. During the six months ended June 30, 2023, we recognized expense of $1.0 million associated with the change in the fair value of the success payment liability which is included in change in fair value of derivative liability in the accompanying condensed consolidated statements of operations. We had no outstanding obligation associated with the Success Fee as of June 30, 2024 or December 31, 2023.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 107
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-107

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+ Details

Collaboration and License Agreement - Schedule of Research and Development Costs Incurred and Revenue Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]
Revenue recognized	$ 1,143	$ 8,081	$ 1,885	$ 12,545
Cost incurred	$ 210	$ 5,152	$ 545	$ 7,273

Collaboration and License Agreement - Schedule of Changes in Contract Liabilities (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2024 USD ($)
Contract liabilities:
Deferred revenue, beginning balance	$ 1,340
Additions	0
Reductions	(1,340)
Deferred revenue, ending balance	$ 0

Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - $ / shares	Jun. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Preferred stock par value (in usd per share)	$ 0.0001	$ 0.0001
Preferred stock authorized (in shares)	5,000,000	5,000,000
Preferred stock issued (in shares)	0	0
Preferred stock outstanding (in shares)	0	0
Common stock par value (in usd per share)	$ 0.0001	$ 0.0001
Common stock authorized (in shares)	200,000,000	200,000,000
Common stock issued (in shares)	43,702,147	39,107,048
Common stock outstanding (in shares)	43,702,147	39,107,048

Stock-based Compensation - Narrative (Details)	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
Stock-based Compensation - Narrative (Details)	Apr. 30, 2021 shares	Jun. 30, 2024 USD ($) $ / shares shares	Jun. 30, 2023 USD ($) $ / shares	Jun. 30, 2024 USD ($) $ / shares shares	Jun. 30, 2023 USD ($) $ / shares shares	Dec. 31, 2022 $ / shares shares	Dec. 31, 2021
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation \| $		$ 2,602,000	$ 1,930,000	$ 4,907,000	$ 4,038,000
Weighted-average grant date fair value of awards (in usd per share) \| $ / shares		$ 3.68	$ 2.24	$ 3.60	$ 1.55
Aggregate intrinsic fair value of options exercised \| $		$ 0	$ 0	$ 0	$ 0
Share-based compensation expense not yet recognized (less than) \| $		12,400,000		$ 12,400,000
Unvested RSAs \| 2017 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Granted (in shares)				0
Share-based compensation expense not yet recognized, excluding option \| $		0		$ 0
Aggregate fair value of awards that vested \| $			100,000		200,000
Shares reserved for vesting of restricted stock units \| 2021 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Granted (in shares)				0
Share-based compensation expense not yet recognized, excluding option \| $		200,000		$ 200,000
Aggregate fair value of awards that vested \| $		$ 700,000	0	$ 700,000	0
Share-based compensation not yet recognized, recognition period				4 months 24 days
Weighted Average Grant Date Fair Value - Granted (in usd per share) \| $ / shares				$ 0
Vested (in shares)				211,500
Performance Shares
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Granted (in shares)		0		0		883,352
Weighted Average Grant Date Fair Value - Granted (in usd per share) \| $ / shares						$ 3.36
Vested (in shares)				0
Total stock-based compensation \| $			$ 0		$ 0
Shares reserved for future issuance under the 2021 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation not yet recognized, recognition period				2 years 6 months
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%
2021 Stock Incentive Plan \| Unvested RSAs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (in shares)	477,725
2021 Stock Employee Stock Purchase Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Offering period							6 months
Purchase period							6 months
ESPP purchase price, percent							0.85
Common Stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (in 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 (in shares)	2,843,116
Maximum number of shares to be added annually, as a percentage of outstanding shares (in shares)				4,911,502
Common Stock \| 2017 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (in shares)	31,884
Common Stock \| 2021 Stock Employee Stock Purchase Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Shares purchased by employees (in shares)				35,180	28,739

Net Loss Attributable to Common Stockholders per Share - Antidilutive Shares (Details) - shares	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	7,755,704	7,139,704
Outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	7,510,033	6,745,934
Unvested RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	150,000	316,500
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	58,904	58,904
Common stock to be issued under the 2021 ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	36,767	18,366

Financial Instruments and Fair Value Measurements - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		3 Months Ended	6 Months Ended
	May 31, 2024	Apr. 30, 2022	Jun. 30, 2023	Jun. 30, 2023	Jun. 30, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Success fee liability paid		$ 1.6	$ 1.6
Change in fair value of derivative liabilities				$ (1.0)
Accrued interest					$ 0.0	$ 0.0
Loan Agreement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loan agreement, amount	$ 60.0
Conversion of outstanding principal	$ 5.0
Conversion price (in usd per share)	$ 6.3182
Loan Agreement \| Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Adjustment rate (percent)	9.99%
Loan Agreement \| Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Adjustment rate (percent)	19.99%

Term Loan - Schedule of Outstanding Term Loans Payable (Details) - USD ($) $ in Thousands	Jun. 30, 2024	May 31, 2024
Debt Instrument [Line Items]
Total principal payments and Final Fee	$ 32,085
Term Loans
Debt Instrument [Line Items]
Unamortized debt discount		$ (5,100)
Term Loans \| Term loan
Debt Instrument [Line Items]
Term loans	30,000
Unamortized debt discount	(4,837)
Total principal payments and Final Fee	$ 25,163

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 835
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-Name Accounting Standards Codification
-Section 55
-Paragraph 8
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+ Details

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details

Summary of Significant Accounting Policies	6 Months Ended
Summary of Significant Accounting Policies	Jun. 30, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements as of June 30, 2024 and December 31, 2023, and for the three and six months ended June 30, 2024 and 2023, 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 our financial position and results of our 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 our Annual Report on Form 10-K for the year ended December 31, 2023 filed with the SEC on March 7, 2024 (the “2023 Annual Report”). The information presented in the condensed consolidated financial statements and related notes as of June 30, 2024, and for the three and six months ended June 30, 2024 and 2023, is unaudited. The December 31, 2023 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, 2024 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2024, 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 our audited financial statements as of and for the year ended December 31, 2023, and the notes thereto, which are included in the 2023 Annual Report. Other than as set forth below there have been no material changes in our significant accounting policies during the six months ended June 30, 2024. 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. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, those related to revenue recognition, accrued expenses, assumptions used in the valuation of stock-based compensation expense and the fair value of the derivative liability, and income taxes. Actual results could differ from those estimates. Recently Adopted Accounting Pronouncements In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging Contracts in Entity’s Own Equity (Subtopic 815-40) (“ASU No. 2020-06”), which reduces the number of accounting models for convertible debt instruments and convertible preferred stock as well as amends the derivatives scope exception for contracts in an entity’s own equity. ASU No. 2020-06 also simplifies the diluted earnings per share calculation in certain areas. We adopted ASU No. 2020-06 on January 1, 2024. The adoption did not have a material impact on the condensed consolidated financial statements. Recent Accounting Pronouncements In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures (“ASU No. 2023-09”), which enhances the transparency and decision usefulness of income tax disclosures primarily related to rate reconciliation and income taxes paid. The provisions of ASU No. 2023-09 are effective for fiscal years beginning after December 15, 2024, with early adoption permitted, and are required to be applied on a prospective basis. Our management is currently evaluating the impact that this standard will have on our consolidated financial statements. Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on our consolidated financial statements upon adoption. Subsequent Events We have evaluated subsequent events and transactions that occurred after the balance sheet date up to the date that the financial statements were issued. Other than as described in these condensed consolidated financial statements, we did not identify any subsequent events that require adjustment or disclosure in the condensed consolidated financial statements.

Financial Instruments and Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2024

Fair Value Disclosures [Abstract]

Schedule of Assets Measured at Fair Value on a Recurring Basis

Assets and liabilities measured at fair value on a recurring basis as of June 30, 2024 were as follows:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	129,881	$	—	$	—	$	129,881
Total assets	$	129,881	$	—	$	—	$	129,881

Liabilities:	$	—	$	—	$	2,841	$	2,841
Derivative liability	$	—	$	—	$	2,841	$	2,841

Assets measured at fair value on a recurring basis as of December 31, 2023 were as follows:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	149,294	$	—	$	—	$	149,294
Total assets	$	149,294	$	—	$	—	$	149,294

Schedule of Weighted-Average Significant Unobservable Inputs

The following table reconciles the change in fair value of the conversion option derivative liability during the six months ended June 30, 2024 based on Level 3 inputs (in thousands):


	Six Months Ended June 30, 2024
Balance at December 31, 2023	$	—
Fair value of embedded derivative at issuance of term loan	4,450
Change in fair value	(1,609)
Balance at June 30, 2024	$	2,841

A summary of the weighted-average significant unobservable inputs (Level 3 inputs) used in measuring the conversion option derivative liability in the term loan as of June 30, 2024 and May 2, 2024 (inception) is as follows:


	June 30, 2024	May 2, 2024
Stock Price	$2.44	$6.08
Volatility	101.0%	101.0%
Risk-free rate (continuous)	4.5%	4.7%
Expected term (in years)	0.75 yrs	0.91 yrs
Dividend yield (continuous)	—%	—%

Accrued Expenses and Other Current Liabilities (Tables)

6 Months Ended

Jun. 30, 2024

Payables and Accruals [Abstract]

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities were comprised as follows:


	June 30, 2024		December 31, 2023
	(in thousands)
Contract research	$	2,845	$	1,049
Manufacturing	2,418		2,772
Employee compensation and benefits	2,274		3,627
Professional fees	847		655
Accrued interest	258		310
Other	59		447
Total accrued expenses and other current liabilities	$	8,701	$	8,860

Related Parties	6 Months Ended
Related Parties	Jun. 30, 2024
Related Party Transactions [Abstract]
Related Parties	9. Related Parties In May 2022, we entered into a sublease agreement with Crossbow Therapeutics, Inc. (“Crossbow”), for which entities affiliated with MPM Capital (“MPM Capital”) are also beneficial owners, to sublease the entirety of our office and laboratory space in Cambridge, Massachusetts. Luke Evnin, Ph.D., the chair of our board of directors, co-founded MPM Capital and serves as Managing Director of MPM Capital. Briggs Morrison, who serves on our board of directors, serves as Executive Partner of MPM Capital and Chief Executive Officer of Crossbow. The term of the sublease agreement commenced in June 2022 and ended in March 2024, with no option to extend. We received cash payments under the sublease of approximately $0.4 million during the six months ended June 30, 2024. In addition, we received $0.2 million from Crossbow in June 2022 as a security deposit, which was remitted to Crossbow following the termination of the sublease.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

+ Details

Condensed Consolidated Statements of Stockholders’ Equity (unaudited) - USD ($) $ in Thousands	Total	Market Offering	Common Stock	Common Stock Market Offering	Additional Paid-in Capital	Additional Paid-in Capital Market Offering	Accumulated Deficit
Stockholders' equity, beginning balance (in shares) at Dec. 31, 2022			31,515,074
Stockholders' equity, beginning balance at Dec. 31, 2022	$ 122,337		$ 3		$ 429,039		$ (306,705)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from at the market offering, net of issuance costs (in shares)				3,824,249
Issuance of common stock from at the market offering, net of issuance costs		$ 8,610				$ 8,610
Stock-based compensation expense	2,108				2,108
Net loss	(11,982)						(11,982)
Stockholders' equity, ending balance (in shares) at Mar. 31, 2023			35,339,323
Stockholders' equity, ending balance at Mar. 31, 2023	121,073		$ 3		439,757		(318,687)
Stockholders' equity, beginning balance (in shares) at Dec. 31, 2022			31,515,074
Stockholders' equity, beginning balance at Dec. 31, 2022	122,337		$ 3		429,039		(306,705)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(17,080)
Stockholders' equity, ending balance (in shares) at Jun. 30, 2023			35,641,784
Stockholders' equity, ending balance at Jun. 30, 2023	118,599		$ 3		442,381		(323,785)
Stockholders' equity, beginning balance (in shares) at Mar. 31, 2023			35,339,323
Stockholders' equity, beginning balance at Mar. 31, 2023	121,073		$ 3		439,757		(318,687)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from at the market offering, net of issuance costs (in shares)			28,739	272,032
Issuance of common stock from at the market offering, net of issuance costs	45	644			45	644
Stock-based compensation expense	1,930				1,930
Stock option exercises (in shares)			1,690
Stock option exercises	5				5
Net loss	(5,098)						(5,098)
Stockholders' equity, ending balance (in shares) at Jun. 30, 2023			35,641,784
Stockholders' equity, ending balance at Jun. 30, 2023	$ 118,599		$ 3		442,381		(323,785)
Stockholders' equity, beginning balance (in shares) at Dec. 31, 2023	39,107,048		39,107,048
Stockholders' equity, beginning balance at Dec. 31, 2023	$ 111,374		$ 4		455,443		(344,073)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from at the market offering, net of issuance costs (in shares)				4,169,324
Issuance of common stock from at the market offering, net of issuance costs		20,089				20,089
Stock-based compensation expense	2,305				2,305
Stock option exercises (in shares)			5,999
Stock option exercises	12				12
Net loss	(16,193)						(16,193)
Stockholders' equity, ending balance (in shares) at Mar. 31, 2024			43,282,371
Stockholders' equity, ending balance at Mar. 31, 2024	$ 117,587		$ 4		477,849		(360,266)
Stockholders' equity, beginning balance (in shares) at Dec. 31, 2023	39,107,048		39,107,048
Stockholders' equity, beginning balance at Dec. 31, 2023	$ 111,374		$ 4		455,443		(344,073)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ (33,442)
Stockholders' equity, ending balance (in shares) at Jun. 30, 2024	43,702,147		43,702,147
Stockholders' equity, ending balance at Jun. 30, 2024	$ 104,018		$ 4		481,529		(377,515)
Stockholders' equity, beginning balance (in shares) at Mar. 31, 2024			43,282,371
Stockholders' equity, beginning balance at Mar. 31, 2024	117,587		$ 4		477,849		(360,266)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from at the market offering, net of issuance costs (in shares)			246,680	172,996
Issuance of common stock from at the market offering, net of issuance costs	76	$ 1,002			76	$ 1,002
Stock-based compensation expense	2,602				2,602
Stock option exercises (in shares)			100
Stock option exercises	0
Net loss	$ (17,249)						(17,249)
Stockholders' equity, ending balance (in shares) at Jun. 30, 2024	43,702,147		43,702,147
Stockholders' equity, ending balance at Jun. 30, 2024	$ 104,018		$ 4		$ 481,529		$ (377,515)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
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-Section 50
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

- Definition

Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

+ References + Details

- Definition

Amount of equity (deficit) attributable to parent. Excludes temporary equity and equity attributable to noncontrolling interest.

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+ Details

Stock-based Compensation - Restricted Stock Award Activity (Details) - Unvested RSUs - 2021 Stock Incentive Plan	6 Months Ended
	Jun. 30, 2024 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested at beginning of period (in shares) \| shares	361,500
Granted (in shares) \| shares	0
Vested (in shares) \| shares	(211,500)
Forfeited (in shares) \| shares	0
Unvested at end of period (in shares) \| shares	150,000
Weighted-Average Grant Date Fair Value Per Share
Weighted Average Grant Date Fair Value - Unvested at beginning of period (in usd per share) \| $ / shares	$ 3.92
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	4.97
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	$ 2.45

Common and Preferred Stock - Schedule of Common Stock Reserved for Issuance (Details) - shares	Jun. 30, 2024	Dec. 31, 2023
Class of Stock [Line Items]
Common stock available for issuance (in shares)	11,033,184	8,539,247
Shares reserved for exercises of outstanding stock options
Class of Stock [Line Items]
Common stock available for issuance (in shares)	7,510,033	5,700,070
Shares reserved for vesting of restricted stock units
Class of Stock [Line Items]
Common stock available for issuance (in shares)	150,000	361,500
Shares reserved for exercises of warrants
Class of Stock [Line Items]
Common stock available for issuance (in shares)	58,904	58,904
Shares reserved for future issuance under the 2021 Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock available for issuance (in shares)	471,933	507,113
Shares reserved for future issuance under the 2021 Stock Incentive Plan
Class of Stock [Line Items]
Common stock available for issuance (in shares)	2,050,950	1,911,660
Shares reserved for future issuance as part of K2HV conversion feature
Class of Stock [Line Items]
Common stock available for issuance (in shares)	791,364	0

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

Common and Preferred Stock

6 Months Ended

Jun. 30, 2024

Equity [Abstract]

Common and Preferred Stock

7. Common and Preferred Stock

Common Stock

We are authorized to issue 200,000,000 shares of common stock. Common stockholders are entitled to dividends if and when declared by our board of directors. As of June 30, 2024, no dividends on common stock had been declared by us.

On May 10, 2022, we entered into a Sales Agreement (the “Sales Agreement”) with Leerink Partners LLC (“Leerink Partners”), formerly known as SVB Securities LLC, pursuant to which we may offer and sell shares of our common stock (the “ATM Offering”). The Sales Agreement provides that Leerink Partners will be entitled to a sales commission equal to 3.0% of the gross sales price per share of all shares sold under the ATM Offering. We were initially entitled to offer and sell shares of our common stock having an aggregate offering price of up to $50.0 million in the ATM Offering. On February 9, 2024, we filed a prospectus supplement (the “Prospectus Supplement”) under our shelf registration statement for the offer and sale of shares of our common stock having an offering price of up to an additional $25.0 million in the ATM Offering. Following our filing of the Prospectus Supplement, we are now entitled to offer and sell shares of our common stock with an aggregate offering price of up to $75.0 million pursuant to the Sales Agreement. During the six months ended June 30, 2024, we sold 4,342,320 shares of our common stock at an average price of $5.11 per share for net proceeds of $21.1 million after deducting sales commissions and offering expenses. During the six months ended June 30, 2023, we sold 4,096,281 shares of our common stock at an average price of $2.36 per share for net proceeds of $9.3 million after deducting sales commissions and offering expenses.

We have reserved shares of common stock for issuance as follows:


	As of June 30,	As of December 31,
	2024	2023
Shares reserved for exercises of outstanding stock options	7,510,033	5,700,070
Shares reserved for vesting of restricted stock units	150,000	361,500
Shares reserved for exercises of warrants	58,904	58,904
Shares reserved for future issuance under the 2021 Employee Stock Purchase Plan	471,933	507,113
Shares reserved for future issuance under the 2021 Stock Incentive Plan	2,050,950	1,911,660
Shares reserved for future issuance as part of K2HV conversion feature	791,364	—
Total shares reserved for future issuance	11,033,184	8,539,247

Preferred Stock

We are authorized to issue 5,000,000 shares of undesignated preferred stock in one or more series. As of June 30, 2024, no shares of preferred stock were issued or outstanding.

- Definition

The entire disclosure for equity.

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+ Details

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 135,303	$ 134,343
Prepaid expenses and other current assets	2,940	2,677
Other receivables	545	1,350
Total current assets	138,788	138,370
Property and equipment, net	7,092	7,958
Restricted cash and cash equivalents, net of current portion	1,211	21,023
Operating lease right of use asset	6,347	6,888
Other assets	265	594
Total assets	153,703	174,833
Current liabilities:
Accounts payable	1,467	1,336
Accrued expenses and other current liabilities	8,701	8,860
Operating lease liability, current	1,274	1,608
Deferred revenue, current	0	907
Note payable, current	0	6,667
Total current liabilities	11,442	19,378
Operating lease liability, net of current portion	10,239	10,992
Deferred revenue, net of current portion	0	433
Note payable, net of discount, issuance costs, and current portion	25,163	32,656
Derivative liability	2,841	0
Total liabilities	49,685	63,459
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value, 5,000,000 shares authorized as of June 30, 2024 and December 31, 2023; no shares issued or outstanding as of June 30, 2024 and December 31, 2023	0	0
Common stock, $0.0001 par value, 200,000,000 shares authorized as of June 30, 2024 and December 31, 2023; 43,702,147 and 39,107,048 shares issued and outstanding as of June 30, 2024 and December 31, 2023, respectively	4	4
Additional paid-in capital	481,529	455,443
Accumulated deficit	(377,515)	(344,073)
Total stockholders’ equity	104,018	111,374
Total liabilities and stockholders’ equity	$ 153,703	$ 174,833

Stock-based Compensation

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Abstract]

Stock-based Compensation

8. Stock-based Compensation

2017 Stock Incentive Plan

In December 2017, we adopted the 2017 Stock Incentive Plan (as amended and restated, the “2017 Plan”), under which we 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 RSAs, including vesting requirements, were determined by our board of directors, subject to the provisions of the 2017 Plan.

2021 Stock Incentive Plan

In April 2021, our board of directors adopted and our stockholders approved the 2021 Stock Incentive Plan (the “2021 Plan”), which became effective immediately prior to the effectiveness of our initial public offering (“IPO”). As a result of 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. Our 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 our board of directors, subject to the provisions of the 2021 Plan.

We 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 IPO, and (iii) 477,725 shares of unvested restricted stock

subject to repurchase by us that may become issuable under the 2021 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 ended December 31, 2022 and continuing until, and including, the fiscal year ending 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 our board of directors. As of June 30, 2024, a total of 4,911,502 additional shares have been added to the total shares authorized for issuance under the 2021 Plan in accordance with these terms.

2021 Employee Stock Purchase Plan

The 2021 ESPP permits eligible employees to purchase shares of our common stock at a discount and consists of consecutive six-month offering periods, each containing a single six-month purchase period. On the first day of each offering period, each employee who is enrolled in the 2021 ESPP will automatically receive an option to purchase up to a whole number of shares of our common stock. The purchase price of each of the shares purchased, in a given purchase period, will be equal to 85% of the lesser of the closing price of a share of our common stock on (i) the first day of the offering period, or (ii) the last day of the offering period. During the six months ended June 30, 2024 and 2023, 35,180 shares and 28,739 shares, respectively, of our common stock were purchased by participants of the 2021 ESPP.

Stock-Based Compensation Expense

Total stock-based compensation expense recognized in the condensed consolidated statements of operations was as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
	(in thousands)
Research and development	$	1,516	$	1,019	$	2,698	$	2,039
General and administrative	1,086		911		2,209		1,999
Total stock-based compensation	$	2,602	$	1,930	$	4,907	$	4,038

RSA Activity

We may, at our 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 us. The shares are recorded in stockholders’ deficit as they vest.

As of December 31, 2023, all RSAs granted to employees or non-employees had become fully vested or had been previously forfeited. No RSAs were granted during the six months ended June 30, 2024. Accordingly, we had no unrecognized stock-based compensation expense related to unvested RSAs as of June 30, 2024.

The aggregate fair value of RSAs that vested during the three and six months ended June 30, 2023, based upon the fair values of the stock underlying the RSAs on the date of vesting, was $0.1 million and $0.2 million, respectively.

RSU Activity

We have granted RSUs to our employees under the 2021 Plan. The following table summarizes RSU activity during the six months ended June 30, 2024:


	Shares/Units	Weighted-Average Grant Date Fair Value Per Share
	(in thousands)
Unvested at December 31, 2023	361,500	$	3.92
Granted	—	$	—
Vested	(211,500)	$	4.97
Forfeited	—	$	—
Unvested at June 30, 2024	150,000	$	2.45

As of June 30, 2024, we had unrecognized stock-based compensation expense related to unvested RSUs of $0.2 million, which we expect to recognize over a weighted-average period of approximately 0.4 years.

The aggregate fair value of RSUs that vested during the three and six months ended June 30, 2024, was $0.7 million based upon the fair value of the stock underlying the RSUs on the day of vesting. No RSUs vested during the three and six months ended June 30, 2023.

Stock Option Activity

During the year ended December 31, 2022, we granted performance-based stock options to certain executive officers for the purchase of an aggregate of 883,352 shares of common stock with a grant date fair value of $3.36 per share. These stock options would have vested only upon achievement of specified performance targets related to certain business objectives on or before December 31, 2023. As of June 30, 2023, none of these options were vested because none of the specified performance targets had been achieved. Because achievement of the specified performance targets was not deemed probable as of June 30, 2023, we did not record any expense for these stock options during the three or six months ended June 30, 2023. As of December 31, 2023, the specified performance targets had not been achieved, and accordingly, all outstanding performance-based stock options expired without vesting. No additional performance-based stock options have been granted during the three or six months ended June 30, 2024.

The fair value of stock options granted during the three and six months ended June 30, 2024 and 2023 was calculated on the date of grant using the following weighted-average assumptions:


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Risk-free interest rate	4.5	%	3.8	%	4.0	%	3.9	%
Expected term (in years)	5.5		5.7		6.0		6.0
Expected annual dividend yield	—	%	—	%	—	%	—	%
Expected volatility	92.6	%	82.6	%	92.6	%	82.6	%

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, 2024 and 2023 was $3.68 and $2.24 per share, respectively. Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted during the six months ended June 30, 2024 and 2023 was $3.60 and $1.55 per share, respectively.

The following table summarizes stock option activity during the six months ended June 30, 2024:


	Options Outstanding
	Number of Options	Weighted-Average Exercise Price per Share		Weighted-Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2023	5,700,070	$	6.89
Granted	2,205,112	$	4.66
Exercised	(6,099)	$	2.05
Cancelled	(389,050)	$	5.06
Outstanding at June 30, 2024	7,510,033	$	6.33	7.85	$	0.8
Exercisable at June 30, 2024	4,100,266	$	7.25	7.09	$	0.5

The aggregate intrinsic fair value of stock options exercised during the three and six months ended June 30, 2024 and 2023 was nominal for each period.

As of June 30, 2024, we had unrecognized stock-based compensation expense related to unvested stock options of $12.4 million, which we expect to recognize over a weighted-average period of approximately 2.5 years.

Accrued Expenses and Other Current Liabilities

6 Months Ended

Jun. 30, 2024

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

5. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities were comprised as follows:


	June 30, 2024		December 31, 2023
	(in thousands)
Contract research	$	2,845	$	1,049
Manufacturing	2,418		2,772
Employee compensation and benefits	2,274		3,627
Professional fees	847		655
Accrued interest	258		310
Other	59		447
Total accrued expenses and other current liabilities	$	8,701	$	8,860

Net Loss Attributable to Common Stockholders per Share

6 Months Ended

Jun. 30, 2024

Earnings Per Share [Abstract]

Net Loss Attributable to Common Stockholders per Share

10. Net Loss Attributable to Common Stockholders per Share


	June 30,
	2024	2023
Outstanding stock options	7,510,033	6,745,934
Unvested RSUs	150,000	316,500
Warrants to purchase common stock	58,904	58,904
Common stock to be issued under the 2021 ESPP	36,767	18,366

Total	7,755,704	7,139,704

Basic net loss per share is computed by dividing net loss by the weighted-average number of shares of common stock outstanding during the applicable period. In computing diluted net loss per share, only potential shares of common stock that are dilutive are included. We considered each issue or series of issues of potential shares of common stock separately when determining whether potential shares of common stock are dilutive or antidilutive. We made such determination in sequence from the most dilutive to the least dilutive and concluded that the conversion option derivative under the K2HV Loan Agreement is dilutive to net loss per share for the three and six months ended June 30, 2024. Pursuant to FASB ASC Topic 260, Earnings Per Share, we applied the if-converted method to determine the effect of the conversion option derivative under the K2HV Loan Agreement on the diluted earnings per share calculations. Pursuant to such method, we adjusted the numerator for the gain recognized during the period in net loss from the conversion option derivative under the K2HV Loan Agreement and the increased the denominator to include the number of additional shares of common stock that would have been outstanding if the conversion option derivative under the K2HV Loan Agreement were converted as of the beginning the period.


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Numerator
Net loss	$	(17,249)	$	(5,098)	$	(33,442)	$	(17,080)
Less: Change in fair value of derivative liability	(1,609)		—		(1,609)		—
Plus: Interest expense on converted term loan	120		—		120		—
Adjusted net loss	$	(18,738)	$	(5,098)	$	(34,931)	$	(17,080)
Denominator
Weighted-average common stock outstanding, basic	43,521,406		35,557,701		42,564,342		35,173,327
Dilutive effect of common stock issuable from assumed conversion of convertible term loan	521,778		—		260,889		—
Weighted-average common stock outstanding, diluted	44,043,184		35,557,701		42,825,231		35,173,327
Net loss per share
Basic	$	(0.40)	$	(0.14)	$	(0.79)	$	(0.49)
Diluted	$	(0.43)	$	(0.14)	$	(0.82)	$	(0.49)