Enliven Therapeutics (ELVN) 10-Q 14 May 24 2024 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2024	May 01, 2024
Cover [Abstract]
Entity Registrant Name	ENLIVEN THERAPEUTICS, INC.
Document Type	10-Q
Trading Symbol	ELVN
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		47,036,698
Amendment Flag	false
Entity Central Index Key	0001672619
Entity Filer Category	Non-accelerated Filer
Document Period End Date	Mar. 31, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Title of 12(b) Security	Common Stock, $0.001 par value per share
Security Exchange Name	NASDAQ
Entity File Number	001-39247
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-1523849
Entity Address, Address Line One	6200 Lookout Road
Entity Address, City or Town	Boulder
Entity Address, State or Province	CO
Entity Address, Postal Zip Code	80301
City Area Code	720
Local Phone Number	647-8519
Document Quarterly Report	true
Document Transition Report	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($)	Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 149,165,000	$ 100,141,000
Marketable securities	171,339,000	153,007,000
Restricted cash	54,000	54,000
Prepaid expenses and other current assets	6,641,000	2,949,000
Contingent value right asset	10,000,000	10,000,000
Total current assets	337,199,000	266,151,000
Property and equipment, net	683,000	742,000
Operating lease right-of-use assets	241,000	320,000
Deferred offering costs	563,000	563,000
Other long-term assets	4,091,000	4,091,000
Total assets	342,777,000	271,867,000
Current liabilities:
Accounts payable	2,727,000	532,000
Accrued expenses and other current liabilities	12,304,000	15,362,000
Contingent value right liability	10,000,000	10,000,000
Total current liabilities	25,031,000	25,894,000
Long-term liabilities	34,000	67,000
Total liabilities	25,065,000	25,961,000
Commitments and contingencies (Note 9):
Stockholders' equity (deficit):
Preferred stock, value	0	0
Common stock, par value $0.001; authorized shares - 100,000,000; issued and outstanding shares - 46,782,639 and 41,292,027 at March 31, 2024 and December 31, 2023, respectively	47,000	41,000
Additional paid-in capital	494,904,000	400,172,000
Accumulated other comprehensive loss	(53,000)	141,000
Accumulated deficit	(177,186,000)	(154,448,000)
Total stockholders' equity (deficit)	317,712,000	245,906,000
Total liabilities, convertible preferred stock and stockholders' equity (deficit)	$ 342,777,000	$ 271,867,000

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2024	Dec. 31, 2023	Feb. 23, 2023
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	46,782,639	41,292,027	41,011,501
Common stock, shares outstanding	46,782,639	41,292,027	41,011,501

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating expenses:
Research and development	$ 19,970	$ 11,880
General and administrative	6,017	4,538
Total operating expenses	25,987	16,418
Loss from operations	(25,987)	(16,418)
Other income (expense), net
Interest income	3,250	1,694
Other expense	(1)	0
Total other income (expense), net	3,249	1,694
Net loss	(22,738)	(14,724)
Other comprehensive income (loss):
Net unrealized losses on marketable securities	(194)	0
Comprehensive loss	$ (22,932)	$ (14,724)
Net loss per share, basic	$ (0.54)	$ (0.8)
Net loss per share, diluted	$ (0.54)	$ (0.8)
Weighted-average shares outstanding, basic	42,045,608	18,514,644
Weighted-average shares outstanding, diluted	42,045,608	18,514,644

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Preferred Stock Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2022	$ (76,825)	$ 149,749	$ 1	$ 6,038		$ (82,864)
Beginning balance, shares at Dec. 31, 2022		61,730,064	3,570,019
Exercise of common stock options	140			140
Exercise of common stock options, shares			55,599
Vesting of restricted stock awards and stock options	73			73
Conversion of convertible preferred stock to common stock in connection with the Merger	149,749	$ (149,749)	$ 18	149,731
Conversion of convertible preferred stock to common stock in connection with the Merger, shares		(61,730,064)	18,216,847
Issuance of common stock in the Financing Transaction, net of issuance costs	159,544		$ 13	159,531
Issuance of common stock in the Financing Transaction, net of issuance costs, shares			12,638,636
Issuance of common stock to former stockholders of Imara Inc. in connection with the Merger	80,241		$ 7	80,234
Issuance of common stock to former stockholders of Imara Inc. in connection with the Merger, shares			6,625,176
Adjustment for change in common stock par value in connection with the Merger			$ 2	(2)
Reverse recapitalization transaction costs	(9,044)			(9,044)
Stock-based compensation	2,262			2,262
Net loss	(14,724)					(14,724)
Ending balance at Mar. 31, 2023	291,416		$ 41	388,963		(97,588)
Ending balance, shares at Mar. 31, 2023			41,106,277
Beginning balance at Dec. 31, 2023	245,906		$ 41	400,172	$ 141	(154,448)
Beginning balance, shares at Dec. 31, 2023			41,292,027
Exercise of common stock options	320			320
Exercise of common stock options, shares			130,780
Vesting of restricted stock awards and stock options	73			73
Vesting of restricted stock units			2,688
Issuance of common stock and Pre-Funded Warrants in the Private Placement, net of issuance costs	89,830		$ 6	89,824
Issuance of common stock and Pre-Funded Warrants in the Private Placement, net of issuance costs, shares			5,357,144
Stock-based compensation	4,515			4,515
Net loss	(22,738)					(22,738)
Other comprehensive loss	(194)				(194)
Ending balance at Mar. 31, 2024	$ 317,712		$ 47	$ 494,904	$ (53)	$ (177,186)
Ending balance, shares at Mar. 31, 2024			46,782,639

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Statement of Stockholders' Equity [Abstract]
Payments of stock and warrants issuance costs	$ 170

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows from operating activities:
Net loss	$ (22,738)	$ (14,724)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	79	67
Stock-based compensation	4,515	2,262
Non-cash lease expense	79	0
Amortization of premiums and discounts on marketable securities, net	(661)	0
Changes in operating assets and liabilities:
Prepaid expenses, other current and long-term assets	(3,642)	(6,088)
Operating lease liabilities	(83)	(1)
Accounts payable	2,155	492
Accrued expenses and other liabilities	(3,065)	(2,852)
Net cash used in operating activities	(23,361)	(20,844)
Cash flows from investing activities:
Maturities of marketable securities	38,913	0
Purchases of marketable securities	(56,778)	0
Purchases of property and equipment	(20)	(31)
Net cash used in investing activities	(17,885)	(31)
Cash flows from financing activities:
Proceeds from exercise of stock options	270	140
Proceeds from issuance of common stock and Pre-Funded Warrants in the Private Placement, net of issuance costs	90,000	0
Proceeds from the Financing Transaction, net of issuance costs	0	162,900
Cash acquired in connection with the reverse recapitalization	0	81,821
Payment of reverse recapitalization transaction costs	0	(7,420)
Net cash provided by financing activities	90,270	237,441
Net increase in cash, cash equivalents and restricted cash	49,024	216,566
Cash, cash equivalents and restricted cash at the beginning of the period	100,195	75,590
Cash, cash equivalents and restricted cash at the end of the period	149,219	292,156
Components of cash, cash equivalents and restricted cash:
Cash and cash equivalents	149,165	292,102
Restricted cash	54	54
Total cash, cash equivalents and restricted cash	149,219	292,156
Supplemental disclosure of non-cash investing and financing activities:
Conversion of convertible preferred stock to common stock	0	149,749
Issuance costs related to the Private Placement included in accounts payable and accrued expenses and other current liabilities	170	0
Issuance costs related to the Financing Transaction included in accounts payable	0	1,534
Transaction costs related to reverse recapitalization included in accounts payable and accrued expenses and other current liabilities	0	1,316
Receivables from stock option exercises included in prepaid expenses and other current assets	$ 50	$ 0

Organization, Description of Bu

Organization, Description of Business and Liquidity	3 Months Ended
	Mar. 31, 2024
Organization Description Of Business And Liquidity [Abstract]
Organization Description of Business and Liquidity	1. Organization, Description of Business and Liquidity Business Enliven Inc. (formerly, Enliven Therapeutics, Inc.) (“Former Enliven”) was incorporated in the State of Delaware on June 12, 2019 . Enliven Therapeutics, Inc. (formerly, Imara Inc.) (the “Company”) is headquartered in Boulder, Colorado. The Company is a clinical-stage biopharmaceutical company focused on the discovery and development of small molecule inhibitors to help people with cancer not only live longer, but live better. The Company aims to address existing and emerging unmet needs with a precision oncology approach that improves survival and enhances overall well-being. Its discovery process combines deep insights in clinically validated biological targets and differentiated chemistry with the goal of designing therapies for unmet needs. Since its inception, the Company has devoted substantially all of its efforts to research and development activities, business planning, establishing and maintaining its intellectual property portfolio, hiring personnel, raising capital, and providing general and administrative support for these activities. To date, the Company has funded its operations primarily through private placements of its common and convertible preferred stock. The Merger, Exchange Ratio and Financing Transaction On October 13, 2022, the Company entered into an agreement and plan of merger (“Merger Agreement” and such transactions considered by the Merger Agreement, the “Merger”) with Former Enliven. On February 23, 2023, the Company completed the Merger with Former Enliven in accordance with the Merger Agreement. Prior to the effective time of the Merger, the Company effected a 1-for-4 reverse stock split (the “Reverse Stock Split”), and right after the Merger, the Company changed its name to Enliven Therapeutics, Inc. Subject to the terms and conditions of the Merger Agreement, at the closing of the Merger, (a) each outstanding share of Former Enliven common stock (including common stock issued upon the conversion of its preferred stock) was converted into the right to receive a number of shares of the Company’s common stock (“Company Common Stock”) (after giving effect to the Reverse Stock Split) equal to the exchange ratio per the Merger Agreement; and (b) each then outstanding Former Enliven stock option that had not previously been exercised prior to the closing of the Merger was assumed by the Company. At closing of the Merger, the Company issued an aggregate of 34,426,351 shares of Company Common Stock to Former Enliven’s stockholders, based on an exchange ratio of approximately 0.2951 shares of Company Common Stock for each share of Former Enliven common stock outstanding immediately prior to the Merger, including those shares of common stock issued upon conversion of the Former Enliven preferred stock, resulting in 41,011,501 shares of Company Common Stock being issued and outstanding immediately following the effective time of the Merger. The Company also assumed all of the outstanding and unexercised stock options to purchase shares of Former Enliven common stock. The assumed options continue to be governed by the terms of the 2019 Equity Incentive Plan (as further discussed in Note 12) under which the options were originally granted, with such options hence forth representing the right to purchase a number of shares of Company Common Stock equal to approximately 0.2951 multiplied by the number of shares of Former Enliven common stock previously represented by such options. The Merger was accounted for as a reverse recapitalization in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”). Under this method of accounting, Former Enliven was deemed to be the accounting acquirer for financial reporting purposes. This determination was primarily based on the expectation that, immediately following the Merger: (i) Former Enliven stockholders will own a substantial majority of the voting rights; (ii) Former Enliven will designate a majority ( eight of nine) of the initial members of the board of directors of the combined company; (iii) Former Enliven’s executive management team will become the management team of the combined company; and (iv) the combined company will be named Enliven Therapeutics, Inc. and be headquartered in Boulder, Colorado. Accordingly, for accounting purposes, the Merger was treated as the equivalent of Former Enliven issuing stock to acquire the net assets of the Company. As a result of the Merger, the net assets of the Company were recorded at their acquisition-date fair value in the financial statements of Former Enliven and the reported operating results prior to the Merger will be those of Former Enliven. Historical common share figures of Former Enliven have been retroactively restated based on the exchange ratio of approximately 0.2951 . On February 23, 2023, prior to the effective time of the Merger, the Company entered into a Contingent Value Rights Agreement (the “CVR Agreement”) with a rights agent, pursuant to which the Company’s pre-Merger common stockholders received one contingent value right (each, a “CVR”) for each outstanding share of the Company’s common stock held by such stockholder as of February 22, 2023. Each CVR represents the contractual right to receive payments upon the occurrence of certain events related to the Company’s sale of certain assets prior to the completion of the Merger, in each case subject to, and in accordance with, the terms and conditions of the CVR Agreement. Under the CVR Agreement, the Company is only liable to the CVR holders once it has received payments from the third-party that purchased the assets, which will only occur upon the third-party achieving certain development milestones related to the assets purchased. In accordance with the CVR Agreement, any distributions to the Company for these milestone payments are then subsequently remitted to the CVR holders, net of permitted deductions, if any. Pursuant to the terms of an asset purchase agreement with a third-party, the Company is eligible to receive two potential milestones, one for $ 10.0 million and a second for $ 50.0 million. The Company has no involvement, control or influence over the development of such assets. Concurrently with the execution of the Merger Agreement, and in order to provide Former Enliven with additional capital for its development programs prior to the closing of the Merger, certain new and current investors purchased an aggregate of $ 164.5 million of common stock of Former Enliven (the “Financing Transaction”). Risks and uncertainties The Company is subject to risks common to development-stage companies in the biotechnology industry including, but not limited to, risks of failure of preclinical studies and clinical trials, new technological innovations, protection of proprietary technology, dependence on key personnel, reliance on third-party organizations, risks of obtaining regulatory approval for any product candidate that it may develop, compliance with government regulations and the need to obtain additional financing. The Company continues to closely monitor macroeconomic and geopolitical developments, including inflation, instability in the banking and financial services sector, tightening of the credit markets, the Russia-Ukraine conflict and widening conflict in the Middle East, and COVID-19. The Company intends to establish clinical trial sites in Israel, which may face enrollment, retention, operational or other difficulties due to conflicts within the region, including, for example, difficulties importing clinical trial drug through Israeli customs, difficulties with patient enrollment, or difficulties with patients or medical personnel accessing appropriate medical facilities. The extent of the impact of these developments on the Company’s business, operations and research and development timelines and plans remains uncertain and will depend on numerous factors, including the impact, if any, on the Company’s personnel, responses of governmental entities, and the responses of third parties, such as contract research organizations, contract manufacturing organizations and other third parties with whom the Company does business. Any prolonged material disruption to the Company’s employees or suppliers could adversely impact the Company’s development activities, financial condition and results of operations, including its ability to obtain financing. The Company is monitoring the potential impact of these developments on its business and consolidated financial statements. To date, the Company has not experienced material business disruptions or incurred impairment losses in the carrying values of its assets as a result of these developments, and it is not aware of any specific related event or circumstance that would require it to revise its estimates reflected in these condensed consolidated financial statements. Liquidity considerations In order to complete the development of the Company’s product candidates and to build the sales, marketing and distribution infrastructure that the Company believes will be necessary to commercialize its product candidates, if approved, the Company will require substantial additional capital. Until the Company can generate a sufficient amount of revenue from the commercialization of its product candidates, the Company may seek to raise any necessary additional capital through equity or debt financings, loans or other capital sources, which could include income from collaborations, partnerships or other marketing, distribution, licensing or other strategic arrangements with third parties, or from grants. Because of the numerous risks and uncertainties associated with research, development and commercialization of product candidates, the Company is unable to estimate the exact amount and timing of its capital requirements. The Company does not expect to generate any meaningful revenue unless and until the Company obtains regulatory approval of and commercializes any of its product candidates, and the Company does not know when, or if, that will occur. The Company has incurred significant losses and negative cash flows from operations since inception. As of March 31, 2024, the Company had an accumulated deficit of $ 177.2 million. The Company expects that its operating losses and negative cash flows will continue for the foreseeable future as the Company continues to develop its product candidates. The Company currently expects that its cash, cash equivalents and marketable securities of $ 320.5 million as of March 31, 2024 will be sufficient to fund operating expenses and capital requirements for at least 12 months from the date the unaudited condensed consolidated financial statements are issued. On June 23, 2023, the Company filed a shelf registration statement on Form S-3 with the Securities and Exchange Commission (the "SEC"), which was declared effective by the SEC on July 3, 2023, which allows the Company to undertake various equity and debt offerings up to $ 400.0 million. On June 23, 2023, the Company also entered into an Open Market Sale Agreement SM (the “Sales Agreement”) with Jefferies LLC (the "Sales Agent”), pursuant to which the Company may offer and sell shares of Company Common Stock, from time to time through an “at-the-market” program under the Securities Act of 1933 (the “Securities Act”), having an aggregate offering price of up to $ 200.0 million through the Sales Agent. Sales of Company Common Stock made pursuant to the Sales Agreement, if any, will be made under the Company’s shelf registration statement on Form S-3. On July 6, 2023, the Company filed a prospectus supplement to the shelf registration statement that covers the offering, issuance and sale of Company Common Stock under the Sales Agreement. Refer to Note 10 for further discussion.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of presentation The accompanying unaudited condensed consolidated financial statements as of March 31, 2024 and for the three months ended March 31, 2024 and 2023 have been prepared in conformity with U.S. GAAP, for interim financial information and pursuant to Article 10 of Regulation S-X of the Securities Act. Accordingly, they do not include all of the information and notes required by U.S. GAAP for complete financial statements. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s audited financial statements and include only normal and recurring adjustments that the Company believes are necessary to fairly state the Company’s financial position and the results of its operations and cash flows. The results for the three months ended March 31, 2024 are not necessarily indicative of the results expected for the full fiscal year or any subsequent interim period. The condensed consolidated balance sheet as of December 31, 2023 has been derived from the audited financial statements at that date but does not include all disclosures required by U.S. GAAP for complete financial statements. Because all of the disclosures required by U.S. GAAP for complete financial statements are not included herein, these unaudited condensed consolidated financial statements and the notes accompanying them should be read in conjunction with the Company’s audited financial statements as of and for the year ended December 31, 2023 included in the Company’s Annual Report on Form 10-K filed with the SEC on March 14, 2024 . Any reference in these notes to applicable guidance is meant to refer to the authoritative U.S. GAAP, as found in the Accounting Standards Codification ("ASC") and Accounting Standards Update ("ASU") of the Financial Accounting Standards Board ("FASB"). Use of estimates The preparation of financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of income and expense during the reporting period. The most significant estimates relate to stock-based compensation and accrued research and development expenses. Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors, including the current economic environment, and makes adjustments when facts and circumstances dictate. Actual results may differ from those estimates or assumptions. Cash and cash equivalents The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. Cash and cash equivalents are recorded at cost, which approximates fair value. As of March 31, 2024 and December 31, 2023 , cash and cash equivalents consisted primarily of checking and money market funds composed of U.S. government obligations. Restricted cash The Company classifies all cash whose use is limited by contractual provisions as restricted cash. Restricted cash arises from the requirement for the Company to maintain cash of $ 54,000 as collateral for a sublease with the facility’s landlord. As of March 31, 2024 and December 31, 2023 , $ 54,000 of restricted cash was reflected as current assets in the condensed consolidated balance sheets. Marketable securities The Company’s marketable securities primarily consist of U.S. Treasury securities. The Company classifies its marketable securities as available-for-sale and records such assets at estimated fair value in the condensed consolidated balance sheets, with unrealized gains and losses, if any, reported as a component of other comprehensive income (loss) within the condensed consolidated statements of operations and comprehensive loss and as a separate component of stockholders’ equity. The Company classifies marketable securities with remaining maturities greater than one year as current assets due to their highly liquid nature and because such marketable securities represent the investment of cash that is available to fund the Company’s current operations. Interest and dividends on marketable securities are included in interest income. The cost of marketable securities sold is based on the specific identification method, with any realized gains and losses recorded as interest income. There were no realized gains and losses during the periods presented. At each balance sheet date, the Company assesses available-for-sale debt securities in an unrealized loss position to determine whether the unrealized loss or any potential credit losses should be recognized in net income (loss). For available-for-sale debt securities in an unrealized loss position, the Company first assesses whether it intends to sell, or it is more likely than not that it will be required to sell, the security before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the security’s amortized cost basis is written down to fair value through net income (loss). For available-for-sale securities that do not meet the aforementioned criteria, the Company evaluates whether the decline in fair value has resulted from credit losses or other factors. In making this assessment, the Company considers the severity of the impairment, any changes in interest rates, underlying credit ratings and forecasted recovery, among other factors. The credit-related portion of unrealized losses, and any subsequent improvements, are recorded as an allowance in interest income. There have been no impairment or credit losses recognized during the periods presented. Concentrations of credit risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities, as well as restricted cash. The Company maintains deposits in U.S. federally insured financial institutions in excess of federally insured limits. The Company has established guidelines regarding approved investments, credit quality, diversification, liquidity and maturities of investments, which are designed to maintain safety and liquidity. Although management currently believes that the financial institutions with whom it does business will be able to fulfill their commitments to the Company, there is no assurance that those institutions will be able to continue to do so. As of March 31, 2024 , the Company has not experienced any losses in its accounts and believes it is not exposed to significant credit risk on its cash balances. Fair value measurements Financial assets and liabilities recorded at fair value on a recurring basis in the balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the price the Company would receive to sell an investment in a timely transaction or pay to transfer a liability in a timely transaction with an independent buyer in the principal market, or in the absence of a principal market, the most advantageous market for the investment or liability. A framework is used for measuring fair value utilizing a three-tier hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). The three levels of the fair value hierarchy are as follows: • Level 1—Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; • Level 2—Quoted prices (other than quoted prices in Level 1) in markets that are not considered to be active or financial instrument valuations for which all significant inputs are observable, either directly or indirectly; and • Level 3—Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable. Financial instruments are categorized in their entirety based on the lowest level of input that is significant to the fair value measurement. The assessment of the significance of a particular input to the fair value measurement requires judgment and considers factors specific to the investment. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. The Company monitors the availability of inputs that are significant to the measurement of fair value to assess the appropriate categorization of financial instruments within the fair value hierarchy. Changes in economic conditions or model-based valuation techniques may require the transfer of financial instruments from one fair value level to another. In such instances, the Company’s policy is to recognize significant transfers between levels at the end of the reporting period. The significance of transfers between levels is evaluated based upon the nature of the financial instrument and size of the transfer relative to total net assets available for benefits. The Company’s cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued expenses and other current liabilities approximate their fair value due to their short maturities. Deferred offering costs Deferred offering costs represent legal, accounting and other direct costs related to the Company’s efforts to raise capital through a public or private sale of the Company’s common stock. These costs are generally deferred until the completion of the applicable offering, at which time such costs are reclassified to additional paid-in-capital as a reduction of the proceeds. In the instance where a planned equity financing is abandoned, terminated or significantly delayed, the deferred offering costs are recorded as expense in the period of such determination . Property and equipment, net Property and equipment are stated at cost, net of accumulated depreciation and amortization. Expenditures for repairs and maintenance are expensed as incurred. When assets are retired or disposed of, the assets and related accumulated depreciation are eliminated from the accounts, and any resulting gain or loss is included in the determination of net income or loss. Depreciation is calculated using the straight-line method over the estimated useful lives of the related assets. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the asset. The Company’s property and equipment consist of laboratory equipment and employee-related computers with estimated useful lives of three to five years . Impairment of long-lived assets The Company evaluates long-lived assets, which consist of laboratory equipment and computers, for impairment at least annually, or whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the asset exceeds the fair value of the asset. As of March 31, 2024 , no impairments have been recognized in the Company’s financial statements. Leases At the inception of a contractual arrangement, the Company determines whether the contract contains a lease by assessing whether there is an identified asset and whether the contract conveys the right to control the use of the identified asset in exchange for consideration over a period of time. If both criteria are met, the Company records the associated lease liability and corresponding right-of-use ("ROU") asset upon commencement of the lease using the implicit rate or a discount rate based on a credit-adjusted secured borrowing rate commensurate with the term of the lease. Certain leases include renewal options at the lessee’s election, which are included when recording the lease if it is reasonably certain that the renewal option will be exercised. Operating lease assets represent a right to use an underlying asset for the lease term and operating lease liabilities represent an obligation to make lease payments arising from the lease. Operating lease liabilities with a term greater than one year and their corresponding ROU assets are recognized on the balance sheet at the commencement date of the lease based on the present value of lease payments over the expected lease term. Lease cost is recognized on a straight-line basis over the lease term and variable lease payments are recognized as operating expenses in the period in which the obligation for those payments is incurred. Variable lease payments primarily include common area maintenance, utilities, real estate taxes, insurance, and other operating costs that are passed on from the lessor in proportion to the space leased by the Company. The Company has elected the practical expedient not to separate between lease and non-lease components. Operating ROU assets are reflected in operating lease right-of-use assets on the balance sheets. Operating lease liabilities are reflected in accrued expenses and other current liabilities and long-term liabilities on the balance sheets. CVR asset and liability The Company evaluates its contracts to determine if those contracts qualify as derivatives under ASC 815, Derivatives and Hedging . For derivative financial instruments that are accounted for as assets or liabilities, the derivative instrument is initially recorded at its fair value and is then re-valued at each reporting date. Any changes in fair value are recorded as other income or expense for each reporting period. Derivative instrument assets or liabilities are classified in the balance sheet as current or non-current based on whether or not net-cash settlement of the derivative instrument is probable within the next 12 months from the balance sheet date. The Company determined that certain contingent payments under the CVR Agreement and milestone payments related to the asset sales prior to the merger qualified as derivatives under ASC 815. Upon such time that these payments are assessed a fair value, they would be recorded as a liability and asset, respectively, on the balance sheet. These values are then remeasured for future expected payout or receipt, as well as the increase in fair value due to the time value of money. These gains or losses, if any, are recognized in the consolidated statements of operations and comprehensive loss within Other income (expense), net. The Company applies a scenario-based method and weighs them based on the possible achievement of certain milestones for both the asset and liability recognized. The fair value measurements are based on significant inputs not observable in the market and thus represent a Level 3 measurement as defined in ASC 820, Fair Value Measurement . The estimated value of the CVR and milestone consideration are based upon available information and certain assumptions, which the Company's management believes are reasonable under the circumstances. Convertible preferred stock The Company classifies convertible preferred stock outside of stockholders’ equity on its balance sheet as the requirements of triggering a deemed liquidation event are not within the Company’s control. In the event of a deemed liquidation event, the proceeds from the event are distributed in accordance with liquidation preferences. The Company records the issuance of convertible preferred stock at the issuance price less related issuance costs and less any discount arising on allocation of proceeds to one or more derivative features. Immediately prior to the effective time of the Merger, all outstanding shares of Former Enliven's convertible preferred stock were converted into shares of Former Enliven's common stock, which were subsequently converted into Company Common Stock upon the closing of the Merger (see Note 11). Research and development expenses The Company expenses research and development costs as incurred. Research and development expenses consist primarily of costs incurred for the discovery and development of its product candidates and include consultants and supplies to conduct clinical, preclinical, and non-clinical studies, costs to acquire, develop and manufacture supplies for preclinical and clinical testing and other studies, expenses incurred under agreements with contract research organizations, and salaries and related costs, including stock-based compensation, as well as depreciation and other allocated facility-related and overhead expenses. Advance payments for goods or services for future research and development activities are deferred and expensed as the goods are delivered or the related services are performed. The Company estimates clinical and preclinical study expenses based on the services performed pursuant to contracts with research institutions and clinical research organizations that conduct and manage preclinical studies and clinical trials on the Company’s behalf. In addition, clinical, preclinical, and non-clinical study materials are manufactured by contract manufacturing organizations. In accruing for these services, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. These estimates are based on communications with the third-party service providers and the Company’s estimates of accrued expenses and on information available at each balance sheet date. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Stock-based compensation The Company measures and records the expense related to stock-based payment awards based on the estimated grant date fair value of those awards. The Company recognizes stock-based compensation expense over the requisite service period on a straight-line basis for all stock-based awards to employees, non-employees and directors, including grants of stock options and other stock-based awards. The Company uses the Black-Scholes option pricing model to determine the fair value of the stock awards. The Black-Scholes option pricing model requires the Company to make assumptions and judgments about the variables used in the calculations, including the expected term, expected volatility of its common stock, risk-free interest rate and expected dividend yield. As the stock-based compensation is based on awards ultimately expected to vest, it is reduced by forfeitures, which the Company accounts for as they occur. The Company classifies equity-based compensation expense in the statement of operations and comprehensive loss in the same manner in which the award recipients’ payroll costs are classified or in which the award recipients’ service payments are classified. Black-Scholes requires the use of subjective assumptions, which determine the fair value of stock-based awards. These assumptions include: • Expected Term—The expected term represents the period that the Company’s options are expected to be outstanding and is determined using the simplified method (based on the mid-point between the vesting date and the end of the contractual term). The Company has very limited historical information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior for its stock option grants. • Expected Volatility—The expected stock price volatilities are estimated based on the historical and implied volatilities of comparable publicly traded companies as the Company does not have sufficient history of trading its common stock. • Risk-Free Interest Rate—The risk-free interest rates are based on U.S. Treasury yields in effect at the grant date for notes with comparable terms as the awards. • Expected Dividend Yield—The Company has never paid dividends on its common stock and has no plans to do so in the future. Therefore, the Company used an expected dividend of zero . The assumptions underlying these valuations represented the Company’s board of directors' and management’s best estimates, which involved inherent uncertainties and the application of management’s judgment. As a result, if the Company had used significantly different assumptions or estimates, the fair value of its stock-based compensation expense could be materially different. Income taxes Income taxes are accounted for using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or the Company’s tax return. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period of enactment. Valuation allowances are established, when necessary, to reduce deferred tax assets to the amount expected to be realized. The Company has generated significant net losses since its inception and accordingly has not recorded a provision for income taxes. The Company evaluates its uncertain tax positions using the provisions of ASC Topic 740 , Income taxes, which prescribes a recognition threshold that a tax position is required to meet before being recognized in the consolidated financial statements by using a "more-likely-than-not" criteria for financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The Company recognizes a tax benefit from an uncertain tax position if it is more likely than not that the tax position will be sustained upon examination by the tax authorities, based on the merits of the position. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, which are considered appropriate as well as the related net interest and penalties. As of March 31, 2024 , there have been no interest or penalties charged in relation to the unrecognized tax benefits. Net loss per share Basic net loss per share of common stock is computed by dividing net loss by the weighted-average number of shares of common stock outstanding during each period, including pre-funded warrants to purchase shares of common stock. The weighted-average number of shares of common stock outstanding used in the basic net loss per share calculation does not include unvested restricted common stock as these shares are considered contingently issuable shares until they vest. Diluted net loss per share of common stock includes the effect, if any, from the potential exercise or conversion of securities, such as convertible preferred stock, stock options, unvested early exercised common stock and unvested restricted common stock, which would result in the issuance of incremental shares of common stock. For diluted net loss per share, the weighted-average number of shares of common stock is the same for basic net loss per share due to the fact that when a net loss exists, dilutive securities are not included in the calculation as the impact is anti-dilutive. For all periods presented, basic and diluted net loss per share were the same, as any additional share equivalents would be anti-dilutive. Segments The Company operates in one segment and, accordingly, no segment disclosures have been presented herein. The Company's long-lived assets are primarily located in the United States. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for allocating and evaluating financial performance. Comprehensive income (loss) Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources, which includes net income (loss) and other comprehensive income (loss). Other comprehensive income (loss) includes unrealized gains and losses on marketable securities, other than losses attributable to a credit loss, which are included in other income and expense. The Company's only component of other comprehensive income (loss) is related to unrealized gains and losses on marketable securities. Emerging growth company status The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the "JOBS Act"). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act, until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it (i) is no longer an emerging growth company or (ii) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. As a result, these financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates. Accounting pronouncements not yet adopted In October 2023, the FASB issued ASU 2023-06, Disclosure Improvements: Codification Amendments in Response to the SEC’s Disclosure Updated and Simplification Initiative , which amends the disclosure or presentation requirements related to various subtopics in the FASB ASC. ASU 2023-06 was issued in response to the SEC's August 2018 final rule that updated and simplified disclosure requirements and is intended to align U.S. GAAP requirements with those of the SEC and to facilitate the application of U.S. GAAP for all entities. For entities subject to the SEC’s existing disclosure requirements and for entities required to file or furnish financial statements with or to the SEC in preparation for the sale of or for purposes of issuing securities that are not subject to contractual restrictions on transfer, the effective date for each amendment will be the date on which the SEC removes that related disclosure from its rules. However, if by June 30, 2027, the SEC has not removed the related disclosure from its regulations, the amendments will be removed from the Codification and not become effective for any entity. The Company is currently evaluating the impact of this guidance, but does not expect the adoption of this guidance to have a material impact on its consolidated financial statements and disclosures. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures , which are intended to improve reportable segment disclosure requirements. ASU 2023-07 expands public entities’ segment disclosures by requiring disclosure of significant segment expenses that are regularly provided to the chief operating decision maker and included within each reported measure of segment profit or loss, an amount and description of its composition for other segment items, and interim disclosures of a reportable segment’s profit or loss and assets. The amendments are effective for fiscal years beginning after December 15, 2023, and for interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. The amendments should be applied retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating the impact that this guidance will have on its consolidated financial statements and disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. ASU 2023-09 improves the transparency and decision usefulness of income tax disclosures by requiring consistent categorization and greater disaggregation of information in the effective tax rate reconciliation and income taxes paid, disaggregated by jurisdiction. It also includes certain other amendments to improve the effectiveness of income tax disclosures. This guidance will be effective for the annual periods beginning after December 15, 2024. Early adoption is permitted. The Company is currently evaluating the impact that this guidance will have on its consolidated financial statements and disclosures.

The Merger

The Merger	3 Months Ended
	Mar. 31, 2024
Business Combination and Asset Acquisition [Abstract]
The Merger	3. The Merger As described in Note 1, Former Enliven merged with the Company on February 23, 2023. The Merger was accounted for as a reverse recapitalization with Former Enliven as the accounting acquirer. The primary pre-combination assets of the Company were cash and cash equivalents. Under reverse recapitalization accounting, the assets and liabilities of the Company were recorded at their fair value, which approximated book value due to the short-term nature of the instruments. No goodwill or intangible assets were recognized. Consequently, the unaudited condensed consolidated financial statements of the Company reflect the operations of Former Enliven for accounting purposes together with a deemed issuance of shares, equivalent to the shares held by the former stockholders of the legal acquirer and a recapitalization of the equity of the accounting acquirer. The following table summarizes the fair value of identifiable assets acquired and liabilities assumed as part of the recapitalization (in thousands): Cash and cash equivalents $ 81,821 Other current assets 1,044 Accrued liabilities ( 2,624 ) Net assets acquired $ 80,241 In connection with the Merger and concurrent Financing Transaction, the Company incurred reverse recapitalization transaction costs of $ 9.0 million and issuance costs of $ 5.0 million, which were capitalized and recorded on the condensed consolidated balance sheets as deferred offering costs. On February 23, 2023, at the close of the Merger, the deferred offering costs were recorded as contra equity. In addition, the Company incurred $ 1.3 million in stock-based compensation expense as a result of the acceleration of vesting of stock options at the time of the Merger. This amount was recorded in general and administrative expense on the condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2023 and year ended December 31, 2023.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements The following tables set forth the fair value of the Company’s financial assets measured at fair value on a recurring basis and indicates the level within the fair value hierarchy utilized to determine such values (in thousands): As of March 31, 2024 Total Level 1 Level 2 Level 3 Cash equivalents: U.S. Treasury backed money market funds $ 143,427 $ 143,427 $ — $ — U.S. Treasury securities 4,977 4,977 — — Marketable securities: U.S. Treasury securities 171,339 171,339 — — Total $ 319,743 $ 319,743 $ — $ — As of December 31, 2023 Total Level 1 Level 2 Level 3 Cash equivalents: U.S. Treasury backed money market funds $ 99,388 $ 99,388 $ — $ — Marketable securities: U.S. Treasury securities 153,007 153,007 — — Total $ 252,395 $ 252,395 $ — $ — CVR asset and liability Upon the completion of the Merger in February 2023, the Company assessed the fair value of the payments to be made under the CVR Agreement to be zero as the Company had determined the payments were not probable. During the fourth quarter of 2023, the Company assessed the fair value of the first milestone under the asset purchase agreement at 100 % based upon certain information received from the third-party indicating that the milestone was likely to be achieved in early 2024. As such, the Company estimated the fair value of the CVR asset and liability for this first milestone and recorded a $ 10.0 million CVR asset and $ 10.0 million CVR liability on its consolidated balance sheet as of December 31, 2023. In March 2024, the Company received formal notification from the third-party that the first milestone event as set forth in the asset purchase agreement had been achieved, and the Company received the $ 10.0 million milestone payment in April 2024. As the second milestone event under this asset purchase agreement relates to the future potential commercialization of the assets, no value was attributed to this milestone as of March 31, 2024 and December 31, 2023. As of March 31, 2024 and December 31, 2023, the Company's condensed consolidated balance sheets reflected a $ 10.0 million CVR asset and $ 10.0 million CVR liability, and no CVR payments have been made under the CVR Agreement. Pursuant to the terms of the CVR Agreement, the Company has 45 days from the end of the calendar quarter in which funds are received to deliver the milestone proceeds, net of permitted deductions, if any, to the rights agent for distribution to the CVR holders.

Marketable Securities

Marketable Securities	3 Months Ended
	Mar. 31, 2024
Marketable Securities [Abstract]
Marketable Securities	5. Marketable Securities The Company’s marketable securities are classified as available-for-sale and are stated at fair value. Marketable securities consisted of the following (in thousands): As of March 31, 2024 Maturity Amortized Unrealized Unrealized Estimated U.S. Treasury securities 1 or less $ 171,392 $ 7 $ ( 60 ) $ 171,339 Total $ 171,392 $ 7 $ ( 60 ) $ 171,339 As of December 31, 2023 Maturity Amortized Unrealized Unrealized Estimated U.S. Treasury securities 1 or less $ 152,866 $ 147 $ ( 6 ) $ 153,007 Total $ 152,866 $ 147 $ ( 6 ) $ 153,007

Leases

Leases	3 Months Ended
	Mar. 31, 2024
Leases [Abstract]
Leases	6. Leases Facility lease In June 2020, the Company executed a sublease agreement for 6,782 square feet of office and laboratory space, which was set to expire on December 30, 2021 . In March 2021, the Company amended its sublease agreement, increasing the leased space by 2,495 square feet to 9,277 square feet and monthly rent to $ 12,000 . In April 2022, the lease term was extended to December 30, 2024 . In addition, the Company’s leased space was increased to 18,170 square feet commencing in July 2022 , and the rental payments were increased by an equally proportionate amount to reflect the increase in floor space. The monthly rent is subject to annual increases through the lease term. The Company is required to pay base rent expense as well as its proportionate share of the facilities operating expenses. The non-lease components, consisting primarily of common area maintenance, are paid separately based on actual costs incurred. Therefore, the variable non-lease components were not included in the ROU assets and lease liabilities and are reflected as expense in the period incurred. The incremental borrowing rate used to calculate the Company’s ROU assets and lease liabilities is 4 %. The incremental borrowing rate was estimated based on the Company's estimated borrowing rate on a collateralized loan. As of March 31, 2024, the remaining ROU assets and lease liabilities were $ 0.2 million and $ 0.3 million, respectively. As of December 31, 2023, the remaining ROU assets and lease liabilities were $ 0.3 million and $ 0.3 million, respectively. Under the facility sublease, the Company recognized rent expense of $ 81,000 and $ 81,000 for the three months ended March 31, 2024 and 2023 , respectively. As of March 31, 2024, the future minimum lease payments under the facilities operating sublease were as follows (in thousands): As of March 31, 2024 Year ending December 31, 2024 (remaining nine months) $ 256 Thereafter — Total future minimum lease payments 256 Less: amount representing interest ( 4 ) Present value of lease liabilities 252 Less: current portion of lease liabilities ( 252 ) Lease liabilities, non-current $ — No impairment losses were recognized during the three months ended March 31, 2024 and 2023 .

Property and Equipment, Net

Property and Equipment, Net	3 Months Ended
	Mar. 31, 2024
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	7. Property and Equipment, Net Property and equipment, net consisted of the following (dollar amounts in thousands): Estimated Useful As of As of Life in Years March 31, 2024 December 31, 2023 Laboratory equipment 5 $ 1,191 $ 1,191 Computer equipment 3 242 222 Property and equipment, gross 1,433 1,413 Less: accumulated depreciation ( 750 ) ( 671 ) Property and equipment, net $ 683 $ 742 Depreciation expense was $ 79,000 and $ 67,000 for the three months ended March 31, 2024 and 2023 , respectively.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	3 Months Ended
	Mar. 31, 2024
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	8. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): As of As of March 31, 2024 December 31, 2023 Accrued employee compensation costs $ 1,808 $ 3,328 Accrued research and development costs 8,835 10,433 Lease liability 252 335 Accrued legal and professional fees 963 902 Other 446 364 Accrued expenses and other current liabilities $ 12,304 $ 15,362

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies Litigation From time to time, the Company may be involved in legal proceedings or be subject to claims arising in the ordinary course of its business. The Company is not currently a party to any legal proceedings. Regardless of outcome, any proceedings or claims can have an adverse impact on the Company because of defense and settlement costs, diversion of resources and other factors, and there can be no assurances that favorable outcomes will be obtained. Indemnification agreements In the ordinary course of business, the Company has provided and may provide indemnification of varying scope and terms to vendors, consultants, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company is not aware of any claims under indemnification arrangements, and it has not accrued any liabilities related to such obligations in its condensed consolidated financial statements as of March 31, 2024 and December 31, 2023 .

Common Stock

Common Stock	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Common Stock	10. Common Stock As of March 31, 2024 , the Company’s Amended and Restated Certificate of Incorporation authorized the Company to issue 100,000,000 shares of $ 0.001 par value common stock, of which 46,782,639 shares were issued and outstanding. As of March 31, 2024 and December 31, 2023, there were 60,830 and 86,153 shares subject to repurchase, respectively. The liability related to shares subject to repurchase totaled $ 0.3 million and $ 0.4 million as of March 31, 2024 and December 31, 2023, respectively, of which $ 0.1 million and $ 0.1 million were recorded as long-term liabilities as of March 31, 2024 and December 31, 2023, respectively. Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, as may be declared by the Company’s board of directors, if any. No dividends have been declared or paid by the Company through March 31, 2024. Upon completion of the Merger on February 23, 2023, the Company issued an aggregate of 34,426,351 shares of its common stock to Former Enliven stockholders, based on an exchange ratio of approximately 0.2951 share of the Company’s common stock for each share of Former Enliven common stock outstanding immediately prior to the Merger, including those shares of common stock issued upon conversion of the Former Enliven preferred stock ( 18,216,847 common shares) and those shares issued with its pre-merger financing of $ 164.5 million ( 12,638,636 common shares). On June 23, 2023, the Company entered into the Sales Agreement with the Sales Agent, pursuant to which the Company may offer and sell shares of its common stock, from time to time, having an aggregate offering price of up to $ 200.0 million through the Sales Agent. Sales of the Company’s common stock made pursuant to the Sales Agreement, if any, will be made under the Company’s shelf registration statement on Form S-3, which was declared effective by the SEC on July 3, 2023. As of March 31, 2024 , there have been no sales of common stock pursuant to the Sales Agreement. On March 21, 2024, the Company sold in a private placement (the "Private Placement") 5,357,144 shares of its common stock at $ 14.00 per share and pre-funded warrants (the "Pre-Funded Warrants") to purchase 1,071,505 shares of its common stock at a price of $ 13.999 per Pre-Funded Warrant, resulting in aggregate gross proceeds of $ 90.0 million, before estimated issuance costs of $ 0.2 million. The Pre-Funded Warrants have an exercise price of $ 0.001 per share, subject to proportional adjustments in the event of stock splits or combinations or similar events, are immediately exercisable on the date of issuance and remain exercisable until exercised in full. As of March 31, 2024, all of the Pre-Funded Warrants related to the Private Placement remain unexercised and outstanding. The Pre-Funded Warrants met the permanent equity criteria classification and, therefore, were classified as a component of permanent stockholders’ equity within additional paid-in capital. The Pre-Funded Warrants are equity classified because they (i) are freestanding financial instruments that are legally detachable and separately exercisable from the equity instruments, (ii) are immediately exercisable, (iii) do not embody an obligation for the Company to repurchase its shares, (iv) permit the holders to receive a fixed number of shares of common stock upon exercise, (v) are indexed to the Company’s common stock and (vi) meet the equity classification criteria. In addition, the Pre-Funded Warrants do not provide any guarantee of value or return. The Company had the following shares of common stock reserved for future issuance: As of As of March 31, 2024 December 31, 2023 Issuance of common stock upon exercise of stock options 7,755,740 5,817,339 Issuance of common stock upon vesting of restricted stock units 95,817 78,505 Equity awards available for grant under equity plans 1,322,398 1,574,426 Shares available for issuance under the Employee Stock Purchase Plan 809,890 402,757 Total common stock reserved for future issuance 9,983,845 7,873,027

Preferred Stock and Convertible

Preferred Stock and Convertible Preferred Stock	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Preferred Stock and Convertible Preferred Stock	11. Preferred Stock and Convertible Preferred Stock Preferred stock As of March 31, 2024 and December 31, 2023 , the Company was authorized to issue up to 10,000,000 shares of preferred stock at a par value of $ 0.001 . As of March 31, 2024 and December 31, 2023 , no shares of preferred stock were issued and outstanding. Convertible preferred stock On February 23, 2023, Former Enliven completed the Merger with the Company in accordance with the Merger Agreement. Under the terms of the Merger Agreement, immediately prior to the effective time of the Merger, each share of Former Enliven’s convertible preferred stock was converted into a share of Former Enliven’s common stock. At closing of the merger, the Company issued an aggregate of 34,426,351 shares of its common stock to Former Enliven stockholders, based on an exchange ratio of approximately 0.2951 shares of the Company’s common stock for each share of Former Enliven’s common stock outstanding immediately prior to the Merger, including those shares of common stock issued upon conversion of Former Enliven's convertible preferred stock.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2024
Compensation Related Costs [Abstract]
Stock-Based Compensation	12. Stock-Based Compensation Equity Incentive Plans 2019 Equity Incentive Plan In July 2019, Former Enliven adopted the 2019 Equity Incentive Plan (the “2019 Plan”) pursuant to which its board of directors may grant non-statutory stock options, stock appreciation rights, restricted stock, and restricted stock units to employees and non-employees and incentive stock options only to employees. The 2019 Plan was terminated as of the close of the Merger, and no shares remain available for future issuance under the 2019 Plan. Any options outstanding under the 2019 Plan remained outstanding and effective. 2016 Stock Incentive Plan The Company’s 2016 Stock Incentive Plan (the “2016 Plan”) provided for the grant of restricted stock, restricted stock units, stock appreciation rights, incentive stock options, non-statutory stock options and other stock-based awards to employees, officers, members of the board of directors, consultants and advisors of the Company. As of the effective date of the 2020 Equity Incentive Plan, no shares remained available for future issuance under the 2016 Plan. Any options or awards outstanding under the 2016 Plan remained outstanding and effective. 2020 Equity Incentive Plan On October 1, 2019, the Company’s board of directors adopted, and on February 26, 2020 the Company’s stockholders approved, the 2020 Equity Incentive Plan, which became effective on March 11, 2020 (the “2020 Plan”). The 2020 Plan provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. On November 8, 2022, the Company’s board of directors adopted, and on February 22, 2023, the Company’s stockholders approved, the amendment and restatement of the 2020 Plan. Following the Reverse Stock Split effected on February 23, 2023, the number of shares reserved for issuance under the 2020 Plan is equal to 4,275,000 shares of the Company’s common stock. The number of shares reserved shall be annually increased on the first day of each fiscal year, beginning with the fiscal year commencing on January 1, 2024 and continuing until, and including, the fiscal year commencing January 1, 2032, equal to the least of (i) 4.5 % of the number of shares of the Company’s common stock outstanding on the first day of such fiscal year and (ii) an amount determined by the Company’s board of directors. The shares of common stock underlying any awards that expire, terminate, or are otherwise surrendered, cancelled, forfeited or repurchased by the Company under the 2020 Plan will be added back to the shares of common stock available for issuance under the 2020 Plan. As of March 31, 2024, 1,322,398 shares of the Company’s common stock remained available for issuance under the 2020 Plan. Awards granted under the Company’s equity plans expire no later than 10 years from the date of grant. Options and restricted stock granted to employees typically vest over a four-year period but may have been granted with different vesting terms. 2020 Employee Stock Purchase Plan On October 1, 2019, the Company’s board of directors adopted, and on February 26, 2020, the Company’s stockholders approved, the 2020 Employee Stock Purchase Plan (the “ESPP”), which became effective on March 11, 2020. The ESPP permits eligible employees who elect to participate, in six-month offering periods, to purchase shares of common stock through payroll deductions at a price equal to 85 % of the fair market value of the common stock on the first or last business day of each applicable six-month offering period, whichever is lower. Purchase dates under the ESPP occur on or about June 13 and December 13 each year. On November 8, 2022, the Company’s board of directors adopted, and on February 22, 2023, the Company’s stockholders approved, an amendment to the ESPP to increase its share reserve. Following the Reverse Stock Split effected on February 23, 2023, the number of shares reserved for issuance under the ESPP is equal to 407,133 shares of the Company’s common stock. The number of shares reserved shall be annually increased on the first day of each fiscal year, beginning with the fiscal year commencing on January 1, 2024 and continuing until, and including, the fiscal year commencing January 1, 2043, equal to the least of (i) 407,133 shares of the Company’s common stock, (ii) 1 % of the number of shares of the Company’s common stock outstanding on the first day of such fiscal year and (iii) an amount determined by the Company’s board of directors. As of March 31, 2024, 809,890 shares of the Company’s common stock remained available for issuance under the ESPP. The Company did no t issue any shares under the ESPP during the three months ended March 31, 2024 and 2023. The Company had an outstanding liability of $ 216,000 and $ 53,000 at March 31, 2024 and December 31, 2023, respectively, which is included in accrued expenses and other current liabilities on the condensed consolidated balance sheets, for employee contributions to the ESPP for shares pending issuance at the end of the offering period. As of March 31, 2024, total stock-based compensation cost not yet recognized related to stock purchase rights under the ESPP was $ 0.1 million, which is expected to be recognized over a weighted-average period of 0.2 years. Stock options The following table summarizes stock option activity: Stock Options Weighted-Average Outstanding - January 1, 2024 5,817,339 $ 11.90 Options granted 2,089,517 14.86 Options exercised and vested ( 151,116 ) 2.59 Options cancelled and forfeited — — Outstanding - March 31, 2024 7,755,740 $ 12.88 As of March 31, 2024, total compensation cost not yet recognized related to unvested stock options was $ 53.1 million, which is expected to be recognized over a weighted-average period of 3.0 years. Restricted stock awards Upon formation of Former Enliven in June 2019, Former Enliven issued approximately 3.0 million shares in restricted common stock to its founders. Additionally, between 2019 and 2020, Former Enliven issued a total of 197,262 shares of restricted stock to employees and consultants. As of March 31, 2024, total compensation cost not yet recognized for restricted stock awards was immaterial. Restricted stock units Restricted stock units ("RSUs") are valued at the market price of a share of the Company’s common stock on the date of grant. The following table summarizes RSU activity: Number of Shares Weighted-Average Grant Date Fair Value Unvested - January 1, 2024 78,505 $ 14.28 Granted 20,000 14.85 Vested ( 2,688 ) 17.56 Forfeited — — Unvested - March 31, 2024 95,817 $ 14.31 As of March 31, 2024, total compensation cost not yet recognized related to unvested RSUs was $ 1.3 million, which is expected to be recognized over a weighted-average period of 3.5 years. Stock-based compensation expense The allocation of stock-based compensation expense was as follows (in thousands): Three Months Ended March 31, 2024 2023 Research and development $ 2,229 $ 492 General and administrative 2,286 1,770 Total stock-based compensation expense $ 4,515 $ 2,262 The assumptions used in the Black-Scholes model to determine the fair value of stock option grants and stock purchase rights under the ESPP were as follows: Three Months Ended March 31, Stock Options 2024 2023 Expected term (years) 5.7 - 6.1 5.8 Expected volatility 84 % 83 % Risk-free interest rate 4.0 % - 4.3 % 4.1 % Expected dividend yield — % — % Three Months Ended March 31, ESPP 2024 2023 Expected term (years) N/A N/A Expected volatility N/A N/A Risk-free interest rate N/A N/A Expected dividend yield N/A N/A

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Net Loss Per Share	13. Net Loss Per Share Basic and diluted net loss per common share were calculated as follows (in thousands, except share and per share amounts): Three Months Ended March 31, 2024 2023 Numerator: Net loss $ ( 22,738 ) $ ( 14,724 ) Denominator: Weighted-average common shares outstanding (including vested and unvested shares) 42,118,267 18,738,115 Less: weighted-average unvested common stock issued upon early exercise of common stock options ( 68,244 ) ( 149,069 ) Less: weighted-average unvested restricted shares of common stock ( 4,415 ) ( 74,402 ) Weighted-average shares used to compute net loss per common share, basic and diluted 42,045,608 18,514,644 Net loss per share, basic and diluted $ (0.54 ) $ ( 0.80 ) Pre-Funded Warrants to purchase 1,071,505 shares of the Company's common stock were used in the calculation of the weighted-average common shares outstanding for the three months ended March 31, 2024. The Company’s potentially dilutive securities have been excluded from the computation of diluted net loss per share as the effect would be antidilutive. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share is the same. The following potentially dilutive securities, presented on an as converted basis, were excluded from the calculation of net loss per share due to their anti-dilutive effect: As of March 31, 2024 2023 Stock options outstanding 7,755,740 3,890,266 Unvested restricted stock awards 2,493 59,339 Unvested restricted stock units 95,817 — ESPP shares pending issuance 21,431 — Total 7,875,481 3,949,605

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of presentation The accompanying unaudited condensed consolidated financial statements as of March 31, 2024 and for the three months ended March 31, 2024 and 2023 have been prepared in conformity with U.S. GAAP, for interim financial information and pursuant to Article 10 of Regulation S-X of the Securities Act. Accordingly, they do not include all of the information and notes required by U.S. GAAP for complete financial statements. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s audited financial statements and include only normal and recurring adjustments that the Company believes are necessary to fairly state the Company’s financial position and the results of its operations and cash flows. The results for the three months ended March 31, 2024 are not necessarily indicative of the results expected for the full fiscal year or any subsequent interim period. The condensed consolidated balance sheet as of December 31, 2023 has been derived from the audited financial statements at that date but does not include all disclosures required by U.S. GAAP for complete financial statements. Because all of the disclosures required by U.S. GAAP for complete financial statements are not included herein, these unaudited condensed consolidated financial statements and the notes accompanying them should be read in conjunction with the Company’s audited financial statements as of and for the year ended December 31, 2023 included in the Company’s Annual Report on Form 10-K filed with the SEC on March 14, 2024 . Any reference in these notes to applicable guidance is meant to refer to the authoritative U.S. GAAP, as found in the Accounting Standards Codification ("ASC") and Accounting Standards Update ("ASU") of the Financial Accounting Standards Board ("FASB").
Use of estimates	Use of estimates The preparation of financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of income and expense during the reporting period. The most significant estimates relate to stock-based compensation and accrued research and development expenses. Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors, including the current economic environment, and makes adjustments when facts and circumstances dictate. Actual results may differ from those estimates or assumptions.
Cash and cash equivalents	Cash and cash equivalents The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. Cash and cash equivalents are recorded at cost, which approximates fair value. As of March 31, 2024 and December 31, 2023 , cash and cash equivalents consisted primarily of checking and money market funds composed of U.S. government obligations.
Restricted cash	Restricted cash The Company classifies all cash whose use is limited by contractual provisions as restricted cash. Restricted cash arises from the requirement for the Company to maintain cash of $ 54,000 as collateral for a sublease with the facility’s landlord. As of March 31, 2024 and December 31, 2023 , $ 54,000 of restricted cash was reflected as current assets in the condensed consolidated balance sheets.
Marketable securities	Marketable securities The Company’s marketable securities primarily consist of U.S. Treasury securities. The Company classifies its marketable securities as available-for-sale and records such assets at estimated fair value in the condensed consolidated balance sheets, with unrealized gains and losses, if any, reported as a component of other comprehensive income (loss) within the condensed consolidated statements of operations and comprehensive loss and as a separate component of stockholders’ equity. The Company classifies marketable securities with remaining maturities greater than one year as current assets due to their highly liquid nature and because such marketable securities represent the investment of cash that is available to fund the Company’s current operations. Interest and dividends on marketable securities are included in interest income. The cost of marketable securities sold is based on the specific identification method, with any realized gains and losses recorded as interest income. There were no realized gains and losses during the periods presented. At each balance sheet date, the Company assesses available-for-sale debt securities in an unrealized loss position to determine whether the unrealized loss or any potential credit losses should be recognized in net income (loss). For available-for-sale debt securities in an unrealized loss position, the Company first assesses whether it intends to sell, or it is more likely than not that it will be required to sell, the security before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the security’s amortized cost basis is written down to fair value through net income (loss). For available-for-sale securities that do not meet the aforementioned criteria, the Company evaluates whether the decline in fair value has resulted from credit losses or other factors. In making this assessment, the Company considers the severity of the impairment, any changes in interest rates, underlying credit ratings and forecasted recovery, among other factors. The credit-related portion of unrealized losses, and any subsequent improvements, are recorded as an allowance in interest income. There have been no impairment or credit losses recognized during the periods presented.
Concentrations of credit risk	Concentrations of credit risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities, as well as restricted cash. The Company maintains deposits in U.S. federally insured financial institutions in excess of federally insured limits. The Company has established guidelines regarding approved investments, credit quality, diversification, liquidity and maturities of investments, which are designed to maintain safety and liquidity. Although management currently believes that the financial institutions with whom it does business will be able to fulfill their commitments to the Company, there is no assurance that those institutions will be able to continue to do so. As of March 31, 2024 , the Company has not experienced any losses in its accounts and believes it is not exposed to significant credit risk on its cash balances.
Fair value measurements	Fair value measurements Financial assets and liabilities recorded at fair value on a recurring basis in the balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the price the Company would receive to sell an investment in a timely transaction or pay to transfer a liability in a timely transaction with an independent buyer in the principal market, or in the absence of a principal market, the most advantageous market for the investment or liability. A framework is used for measuring fair value utilizing a three-tier hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). The three levels of the fair value hierarchy are as follows: • Level 1—Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; • Level 2—Quoted prices (other than quoted prices in Level 1) in markets that are not considered to be active or financial instrument valuations for which all significant inputs are observable, either directly or indirectly; and • Level 3—Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable. Financial instruments are categorized in their entirety based on the lowest level of input that is significant to the fair value measurement. The assessment of the significance of a particular input to the fair value measurement requires judgment and considers factors specific to the investment. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. The Company monitors the availability of inputs that are significant to the measurement of fair value to assess the appropriate categorization of financial instruments within the fair value hierarchy. Changes in economic conditions or model-based valuation techniques may require the transfer of financial instruments from one fair value level to another. In such instances, the Company’s policy is to recognize significant transfers between levels at the end of the reporting period. The significance of transfers between levels is evaluated based upon the nature of the financial instrument and size of the transfer relative to total net assets available for benefits. The Company’s cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued expenses and other current liabilities approximate their fair value due to their short maturities.
Deferred offering costs	Deferred offering costs Deferred offering costs represent legal, accounting and other direct costs related to the Company’s efforts to raise capital through a public or private sale of the Company’s common stock. These costs are generally deferred until the completion of the applicable offering, at which time such costs are reclassified to additional paid-in-capital as a reduction of the proceeds. In the instance where a planned equity financing is abandoned, terminated or significantly delayed, the deferred offering costs are recorded as expense in the period of such determination
Property and equipment, net	Property and equipment, net Property and equipment are stated at cost, net of accumulated depreciation and amortization. Expenditures for repairs and maintenance are expensed as incurred. When assets are retired or disposed of, the assets and related accumulated depreciation are eliminated from the accounts, and any resulting gain or loss is included in the determination of net income or loss. Depreciation is calculated using the straight-line method over the estimated useful lives of the related assets. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the asset. The Company’s property and equipment consist of laboratory equipment and employee-related computers with estimated useful lives of three to five years .
Impairment of long-lived assets	Impairment of long-lived assets The Company evaluates long-lived assets, which consist of laboratory equipment and computers, for impairment at least annually, or whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the asset exceeds the fair value of the asset. As of March 31, 2024 , no impairments have been recognized in the Company’s financial statements.
Leases	Leases At the inception of a contractual arrangement, the Company determines whether the contract contains a lease by assessing whether there is an identified asset and whether the contract conveys the right to control the use of the identified asset in exchange for consideration over a period of time. If both criteria are met, the Company records the associated lease liability and corresponding right-of-use ("ROU") asset upon commencement of the lease using the implicit rate or a discount rate based on a credit-adjusted secured borrowing rate commensurate with the term of the lease. Certain leases include renewal options at the lessee’s election, which are included when recording the lease if it is reasonably certain that the renewal option will be exercised. Operating lease assets represent a right to use an underlying asset for the lease term and operating lease liabilities represent an obligation to make lease payments arising from the lease. Operating lease liabilities with a term greater than one year and their corresponding ROU assets are recognized on the balance sheet at the commencement date of the lease based on the present value of lease payments over the expected lease term. Lease cost is recognized on a straight-line basis over the lease term and variable lease payments are recognized as operating expenses in the period in which the obligation for those payments is incurred. Variable lease payments primarily include common area maintenance, utilities, real estate taxes, insurance, and other operating costs that are passed on from the lessor in proportion to the space leased by the Company. The Company has elected the practical expedient not to separate between lease and non-lease components. Operating ROU assets are reflected in operating lease right-of-use assets on the balance sheets. Operating lease liabilities are reflected in accrued expenses and other current liabilities and long-term liabilities on the balance sheets.
CVR asset and liability	CVR asset and liability The Company evaluates its contracts to determine if those contracts qualify as derivatives under ASC 815, Derivatives and Hedging . For derivative financial instruments that are accounted for as assets or liabilities, the derivative instrument is initially recorded at its fair value and is then re-valued at each reporting date. Any changes in fair value are recorded as other income or expense for each reporting period. Derivative instrument assets or liabilities are classified in the balance sheet as current or non-current based on whether or not net-cash settlement of the derivative instrument is probable within the next 12 months from the balance sheet date. The Company determined that certain contingent payments under the CVR Agreement and milestone payments related to the asset sales prior to the merger qualified as derivatives under ASC 815. Upon such time that these payments are assessed a fair value, they would be recorded as a liability and asset, respectively, on the balance sheet. These values are then remeasured for future expected payout or receipt, as well as the increase in fair value due to the time value of money. These gains or losses, if any, are recognized in the consolidated statements of operations and comprehensive loss within Other income (expense), net. The Company applies a scenario-based method and weighs them based on the possible achievement of certain milestones for both the asset and liability recognized. The fair value measurements are based on significant inputs not observable in the market and thus represent a Level 3 measurement as defined in ASC 820, Fair Value Measurement . The estimated value of the CVR and milestone consideration are based upon available information and certain assumptions, which the Company's management believes are reasonable under the circumstances.
Convertible preferred stock	Convertible preferred stock The Company classifies convertible preferred stock outside of stockholders’ equity on its balance sheet as the requirements of triggering a deemed liquidation event are not within the Company’s control. In the event of a deemed liquidation event, the proceeds from the event are distributed in accordance with liquidation preferences. The Company records the issuance of convertible preferred stock at the issuance price less related issuance costs and less any discount arising on allocation of proceeds to one or more derivative features. Immediately prior to the effective time of the Merger, all outstanding shares of Former Enliven's convertible preferred stock were converted into shares of Former Enliven's common stock, which were subsequently converted into Company Common Stock upon the closing of the Merger (see Note 11).
Research and development expenses	Research and development expenses The Company expenses research and development costs as incurred. Research and development expenses consist primarily of costs incurred for the discovery and development of its product candidates and include consultants and supplies to conduct clinical, preclinical, and non-clinical studies, costs to acquire, develop and manufacture supplies for preclinical and clinical testing and other studies, expenses incurred under agreements with contract research organizations, and salaries and related costs, including stock-based compensation, as well as depreciation and other allocated facility-related and overhead expenses. Advance payments for goods or services for future research and development activities are deferred and expensed as the goods are delivered or the related services are performed. The Company estimates clinical and preclinical study expenses based on the services performed pursuant to contracts with research institutions and clinical research organizations that conduct and manage preclinical studies and clinical trials on the Company’s behalf. In addition, clinical, preclinical, and non-clinical study materials are manufactured by contract manufacturing organizations. In accruing for these services, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. These estimates are based on communications with the third-party service providers and the Company’s estimates of accrued expenses and on information available at each balance sheet date. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly.
Stock-based compensation	Stock-based compensation The Company measures and records the expense related to stock-based payment awards based on the estimated grant date fair value of those awards. The Company recognizes stock-based compensation expense over the requisite service period on a straight-line basis for all stock-based awards to employees, non-employees and directors, including grants of stock options and other stock-based awards. The Company uses the Black-Scholes option pricing model to determine the fair value of the stock awards. The Black-Scholes option pricing model requires the Company to make assumptions and judgments about the variables used in the calculations, including the expected term, expected volatility of its common stock, risk-free interest rate and expected dividend yield. As the stock-based compensation is based on awards ultimately expected to vest, it is reduced by forfeitures, which the Company accounts for as they occur. The Company classifies equity-based compensation expense in the statement of operations and comprehensive loss in the same manner in which the award recipients’ payroll costs are classified or in which the award recipients’ service payments are classified. Black-Scholes requires the use of subjective assumptions, which determine the fair value of stock-based awards. These assumptions include: • Expected Term—The expected term represents the period that the Company’s options are expected to be outstanding and is determined using the simplified method (based on the mid-point between the vesting date and the end of the contractual term). The Company has very limited historical information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior for its stock option grants. • Expected Volatility—The expected stock price volatilities are estimated based on the historical and implied volatilities of comparable publicly traded companies as the Company does not have sufficient history of trading its common stock. • Risk-Free Interest Rate—The risk-free interest rates are based on U.S. Treasury yields in effect at the grant date for notes with comparable terms as the awards. • Expected Dividend Yield—The Company has never paid dividends on its common stock and has no plans to do so in the future. Therefore, the Company used an expected dividend of zero . The assumptions underlying these valuations represented the Company’s board of directors' and management’s best estimates, which involved inherent uncertainties and the application of management’s judgment. As a result, if the Company had used significantly different assumptions or estimates, the fair value of its stock-based compensation expense could be materially different.
Income taxes	Income taxes Income taxes are accounted for using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or the Company’s tax return. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period of enactment. Valuation allowances are established, when necessary, to reduce deferred tax assets to the amount expected to be realized. The Company has generated significant net losses since its inception and accordingly has not recorded a provision for income taxes. The Company evaluates its uncertain tax positions using the provisions of ASC Topic 740 , Income taxes, which prescribes a recognition threshold that a tax position is required to meet before being recognized in the consolidated financial statements by using a "more-likely-than-not" criteria for financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The Company recognizes a tax benefit from an uncertain tax position if it is more likely than not that the tax position will be sustained upon examination by the tax authorities, based on the merits of the position. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, which are considered appropriate as well as the related net interest and penalties. As of March 31, 2024 , there have been no interest or penalties charged in relation to the unrecognized tax benefits.
Net loss per share	Net loss per share Basic net loss per share of common stock is computed by dividing net loss by the weighted-average number of shares of common stock outstanding during each period, including pre-funded warrants to purchase shares of common stock. The weighted-average number of shares of common stock outstanding used in the basic net loss per share calculation does not include unvested restricted common stock as these shares are considered contingently issuable shares until they vest. Diluted net loss per share of common stock includes the effect, if any, from the potential exercise or conversion of securities, such as convertible preferred stock, stock options, unvested early exercised common stock and unvested restricted common stock, which would result in the issuance of incremental shares of common stock. For diluted net loss per share, the weighted-average number of shares of common stock is the same for basic net loss per share due to the fact that when a net loss exists, dilutive securities are not included in the calculation as the impact is anti-dilutive. For all periods presented, basic and diluted net loss per share were the same, as any additional share equivalents would be anti-dilutive.
Segments	Segments The Company operates in one segment and, accordingly, no segment disclosures have been presented herein. The Company's long-lived assets are primarily located in the United States. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for allocating and evaluating financial performance.
Comprehensive income (loss)	Comprehensive income (loss) Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources, which includes net income (loss) and other comprehensive income (loss). Other comprehensive income (loss) includes unrealized gains and losses on marketable securities, other than losses attributable to a credit loss, which are included in other income and expense. The Company's only component of other comprehensive income (loss) is related to unrealized gains and losses on marketable securities.
Emerging growth company status	Emerging growth company status The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the "JOBS Act"). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act, until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it (i) is no longer an emerging growth company or (ii) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. As a result, these financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates.
Accounting pronouncements not yet adopted	Accounting pronouncements not yet adopted In October 2023, the FASB issued ASU 2023-06, Disclosure Improvements: Codification Amendments in Response to the SEC’s Disclosure Updated and Simplification Initiative , which amends the disclosure or presentation requirements related to various subtopics in the FASB ASC. ASU 2023-06 was issued in response to the SEC's August 2018 final rule that updated and simplified disclosure requirements and is intended to align U.S. GAAP requirements with those of the SEC and to facilitate the application of U.S. GAAP for all entities. For entities subject to the SEC’s existing disclosure requirements and for entities required to file or furnish financial statements with or to the SEC in preparation for the sale of or for purposes of issuing securities that are not subject to contractual restrictions on transfer, the effective date for each amendment will be the date on which the SEC removes that related disclosure from its rules. However, if by June 30, 2027, the SEC has not removed the related disclosure from its regulations, the amendments will be removed from the Codification and not become effective for any entity. The Company is currently evaluating the impact of this guidance, but does not expect the adoption of this guidance to have a material impact on its consolidated financial statements and disclosures. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures , which are intended to improve reportable segment disclosure requirements. ASU 2023-07 expands public entities’ segment disclosures by requiring disclosure of significant segment expenses that are regularly provided to the chief operating decision maker and included within each reported measure of segment profit or loss, an amount and description of its composition for other segment items, and interim disclosures of a reportable segment’s profit or loss and assets. The amendments are effective for fiscal years beginning after December 15, 2023, and for interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. The amendments should be applied retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating the impact that this guidance will have on its consolidated financial statements and disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. ASU 2023-09 improves the transparency and decision usefulness of income tax disclosures by requiring consistent categorization and greater disaggregation of information in the effective tax rate reconciliation and income taxes paid, disaggregated by jurisdiction. It also includes certain other amendments to improve the effectiveness of income tax disclosures. This guidance will be effective for the annual periods beginning after December 15, 2024. Early adoption is permitted. The Company is currently evaluating the impact that this guidance will have on its consolidated financial statements and disclosures.

The Merger (Tables)

The Merger (Tables)	3 Months Ended
	Mar. 31, 2024
Business Combination and Asset Acquisition [Abstract]
Summary of Fair Value of Identifiable Assets Acquired and Liabilities Assumed as Part of Recapitalization	(in thousands): Cash and cash equivalents $ 81,821 Other current assets 1,044 Accrued liabilities ( 2,624 ) Net assets acquired $ 80,241

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Schedule of Financial Assets Measured at Fair Value on a Recurring Basis	The following tables set forth the fair value of the Company’s financial assets measured at fair value on a recurring basis and indicates the level within the fair value hierarchy utilized to determine such values (in thousands): As of March 31, 2024 Total Level 1 Level 2 Level 3 Cash equivalents: U.S. Treasury backed money market funds $ 143,427 $ 143,427 $ — $ — U.S. Treasury securities 4,977 4,977 — — Marketable securities: U.S. Treasury securities 171,339 171,339 — — Total $ 319,743 $ 319,743 $ — $ — As of December 31, 2023 Total Level 1 Level 2 Level 3 Cash equivalents: U.S. Treasury backed money market funds $ 99,388 $ 99,388 $ — $ — Marketable securities: U.S. Treasury securities 153,007 153,007 — — Total $ 252,395 $ 252,395 $ — $ —

Marketable Securities (Tables)

Marketable Securities (Tables)	3 Months Ended
	Mar. 31, 2024
Marketable Securities [Abstract]
Schedule of Available-for-sale Marketable Securities	The Company’s marketable securities are classified as available-for-sale and are stated at fair value. Marketable securities consisted of the following (in thousands): As of March 31, 2024 Maturity Amortized Unrealized Unrealized Estimated U.S. Treasury securities 1 or less $ 171,392 $ 7 $ ( 60 ) $ 171,339 Total $ 171,392 $ 7 $ ( 60 ) $ 171,339 As of December 31, 2023 Maturity Amortized Unrealized Unrealized Estimated U.S. Treasury securities 1 or less $ 152,866 $ 147 $ ( 6 ) $ 153,007 Total $ 152,866 $ 147 $ ( 6 ) $ 153,007

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2024
Leases [Abstract]
Summary of Future Minimum Lease Payments Under Operating Sublease	As of March 31, 2024, the future minimum lease payments under the facilities operating sublease were as follows (in thousands): As of March 31, 2024 Year ending December 31, 2024 (remaining nine months) $ 256 Thereafter — Total future minimum lease payments 256 Less: amount representing interest ( 4 ) Present value of lease liabilities 252 Less: current portion of lease liabilities ( 252 ) Lease liabilities, non-current $ —

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	3 Months Ended
	Mar. 31, 2024
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following (dollar amounts in thousands): Estimated Useful As of As of Life in Years March 31, 2024 December 31, 2023 Laboratory equipment 5 $ 1,191 $ 1,191 Computer equipment 3 242 222 Property and equipment, gross 1,433 1,413 Less: accumulated depreciation ( 750 ) ( 671 ) Property and equipment, net $ 683 $ 742

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2024
Payables and Accruals [Abstract]
Summary Of Accrued Expenses And Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): As of As of March 31, 2024 December 31, 2023 Accrued employee compensation costs $ 1,808 $ 3,328 Accrued research and development costs 8,835 10,433 Lease liability 252 335 Accrued legal and professional fees 963 902 Other 446 364 Accrued expenses and other current liabilities $ 12,304 $ 15,362

Common Stock (Tables)

Common Stock (Tables)	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Following Shares of Common Stock Reserved for Future Issuance	The Company had the following shares of common stock reserved for future issuance: As of As of March 31, 2024 December 31, 2023 Issuance of common stock upon exercise of stock options 7,755,740 5,817,339 Issuance of common stock upon vesting of restricted stock units 95,817 78,505 Equity awards available for grant under equity plans 1,322,398 1,574,426 Shares available for issuance under the Employee Stock Purchase Plan 809,890 402,757 Total common stock reserved for future issuance 9,983,845 7,873,027

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Summary of Stock Option Activity	The following table summarizes stock option activity: Stock Options Weighted-Average Outstanding - January 1, 2024 5,817,339 $ 11.90 Options granted 2,089,517 14.86 Options exercised and vested ( 151,116 ) 2.59 Options cancelled and forfeited — — Outstanding - March 31, 2024 7,755,740 $ 12.88
Summary of Stock-Based Compensation Expense	The allocation of stock-based compensation expense was as follows (in thousands): Three Months Ended March 31, 2024 2023 Research and development $ 2,229 $ 492 General and administrative 2,286 1,770 Total stock-based compensation expense $ 4,515 $ 2,262
Summary of Stock-Based Compensation Fair Value Assumptions	The assumptions used in the Black-Scholes model to determine the fair value of stock option grants and stock purchase rights under the ESPP were as follows: Three Months Ended March 31, Stock Options 2024 2023 Expected term (years) 5.7 - 6.1 5.8 Expected volatility 84 % 83 % Risk-free interest rate 4.0 % - 4.3 % 4.1 % Expected dividend yield — % — % Three Months Ended March 31, ESPP 2024 2023 Expected term (years) N/A N/A Expected volatility N/A N/A Risk-free interest rate N/A N/A Expected dividend yield N/A N/A
Restricted Stock Units
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Summary of Restricted Stock Award and Restricted Stock Units Activity	Restricted stock units ("RSUs") are valued at the market price of a share of the Company’s common stock on the date of grant. The following table summarizes RSU activity: Number of Shares Weighted-Average Grant Date Fair Value Unvested - January 1, 2024 78,505 $ 14.28 Granted 20,000 14.85 Vested ( 2,688 ) 17.56 Forfeited — — Unvested - March 31, 2024 95,817 $ 14.31

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Net Loss Per Common Share	Basic and diluted net loss per common share were calculated as follows (in thousands, except share and per share amounts): Three Months Ended March 31, 2024 2023 Numerator: Net loss $ ( 22,738 ) $ ( 14,724 ) Denominator: Weighted-average common shares outstanding (including vested and unvested shares) 42,118,267 18,738,115 Less: weighted-average unvested common stock issued upon early exercise of common stock options ( 68,244 ) ( 149,069 ) Less: weighted-average unvested restricted shares of common stock ( 4,415 ) ( 74,402 ) Weighted-average shares used to compute net loss per common share, basic and diluted 42,045,608 18,514,644 Net loss per share, basic and diluted $ (0.54 ) $ ( 0.80 )
Anti Dilutive Potential Common Shares Excluded From Computation of Diluted Net Loss Per Share	The following potentially dilutive securities, presented on an as converted basis, were excluded from the calculation of net loss per share due to their anti-dilutive effect: As of March 31, 2024 2023 Stock options outstanding 7,755,740 3,890,266 Unvested restricted stock awards 2,493 59,339 Unvested restricted stock units 95,817 — ESPP shares pending issuance 21,431 — Total 7,875,481 3,949,605

Organization, Description of _2

Organization, Description of Business and Liquidity - Additional Information (Details)			3 Months Ended
	Jun. 23, 2023 USD ($)	Feb. 23, 2023 USD ($) Director shares	Mar. 31, 2024 USD ($) shares	Dec. 31, 2023 USD ($) shares
Organization, Description of Business and Liquidity [Line Items]
Entity incorporation date			Jun. 12, 2019
Reverse stock split		1-for-4
Business acquisition, exchange ratio		0.2951%
Common stock, shares issued | shares		41,011,501	46,782,639	41,292,027
Common stock, shares outstanding | shares		41,011,501	46,782,639	41,292,027
Majority number of initial members of board of directors | Director		8
Common stock, par value $0.001; authorized shares - 100,000,000; issued and outstanding shares - 46,782,639 and 41,292,027 at March 31, 2024 and December 31, 2023, respectively		$ 164,500,000	$ 47,000	$ 41,000
Accumulated deficit			(177,186,000)	$ (154,448,000)
Contingent value right		one
Cash, cash equivalents and marketable securities			$ 320,500,000
Milestone One
Organization, Description of Business and Liquidity [Line Items]
Payments to be received under contingent value rights agreement		$ 10,000,000
Milestone Two
Organization, Description of Business and Liquidity [Line Items]
Payments to be received under contingent value rights agreement		$ 50,000,000
Maximum
Organization, Description of Business and Liquidity [Line Items]
Equity and debt offerings available	$ 400,000,000
Maximum | Sales agreement
Organization, Description of Business and Liquidity [Line Items]
Common stock, aggregate offering price	$ 200,000,000
Merger Agreement
Organization, Description of Business and Liquidity [Line Items]
Business acquisition, common shares issued | shares		34,426,351

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended
	Mar. 31, 2024 USD ($) Segment	Dec. 31, 2023 USD ($)
Summary of Significant Accounting Policies [LineItems]
Restricted cash as current assets	$ 54,000	$ 54,000
Restricted cash collateral of sublease	$ 54,000
Expected dividend yield	0%
Number of operating segments | Segment	1
Impairment of long-lived assets	$ 0
Interest or penalties charged in relation to unrecognized tax benefits	$ 0
Minimum
Summary of Significant Accounting Policies [LineItems]
Property and equipment estimated useful lives	3 years
Maximum
Summary of Significant Accounting Policies [LineItems]
Property and equipment estimated useful lives	5 years

The Merger - Summary of Fair Va

The Merger - Summary of Fair Value of Identifiable Assets Acquired and Liabilities Assumed as Part of Recapitalization (Details) $ in Thousands	Feb. 23, 2023 USD ($)
Business Combination and Asset Acquisition [Abstract]
Cash and cash equivalents	$ 81,821
Other current assets	1,044
Accrued liabilities	(2,624)
Net assets acquired	$ 80,241

The Merger - Additional Informa

The Merger - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended
	Feb. 23, 2023	Mar. 31, 2023
Business Acquisition [Line Items]
Reverse recapitalization transaction costs	$ 9,000	$ 9,044
Issuance costs incurred	5,000	$ 4,955
General and Administrative Expense
Business Acquisition [Line Items]
Stock-based compensation expense upon acceleration	$ 1,300

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Recurring - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	$ 319,743	$ 252,395
U.S. Treasury backed money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	143,427	99,388
U.S. Treasury securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	4,977
Marketable securities	171,339	153,007
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	319,743	252,395
Level 1 | U.S. Treasury backed money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	143,427	99,388
Level 1 | U.S. Treasury securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	4,977
Marketable securities	171,339	153,007
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	0	0
Level 2 | U.S. Treasury backed money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Level 2 | U.S. Treasury securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0
Marketable securities	0	0
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	0	0
Level 3 | U.S. Treasury backed money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Level 3 | U.S. Treasury securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0
Marketable securities	$ 0	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)		1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Apr. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payments made under CVR Agreement			$ 0	$ 0
Fair value assessment of payments under CVR Agreement	$ 0
CVR asset			10,000,000	10,000,000
CVR liability			$ 10,000,000	10,000,000
Terms of CVR Agreement			Pursuant to the terms of the CVR Agreement, the Company has 45 days from the end of the calendar quarter in which funds are received to deliver the milestone proceeds, net of permitted deductions, if any, to the rights agent for distribution to the CVR holders.
Subsequent Event
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payments received under CVR Agreement		$ 10,000,000
Milestone One
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
CVR asset				10,000,000
CVR liability				$ 10,000,000
Percentage of CVR asset and liability upon expected probability				100%
Milestone Two
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assessment of milestone payments under CVR Agreement			$ 0	$ 0

Marketable Securities - Schedul

Marketable Securities - Schedule of Available-for-sale Marketable Securities (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Marketable Securities [Line Items]
Amortized Cost	$ 171,392	$ 152,866
Unrealized Gains	7	147
Unrealized Losses	(60)	(6)
Estimated Fair Value	171,339	153,007
U.S. Treasury securities
Marketable Securities [Line Items]
Amortized Cost	171,392	152,866
Unrealized Gains	7	147
Unrealized Losses	(60)	(6)
Estimated Fair Value	$ 171,339	$ 153,007
Maturity (in years)	1 or less	1 or less

Leases - Additional Information

Leases - Additional Information (Details)	1 Months Ended			3 Months Ended
	Apr. 30, 2022	Mar. 31, 2021 USD ($)	Jun. 30, 2020 ft²	Mar. 31, 2024 USD ($) ft²	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Mar. 01, 2021 ft²	Feb. 28, 2021 ft²
Leases [Abstract]
Area of rentable square feet of office and laboratory space | ft²			6,782
Lease expiration date			Dec. 30, 2021
Square feet of office space leased | ft²				18,170			9,277	2,495
Lease and rental expense		$ 12,000		$ 81,000	$ 81,000
Lease renewal term for office space extended date	Dec. 30, 2024
Lease commencement date				Jul. 31, 2022
Incremental borrowing rate of right of used assets and lease liabilities				400%
Remaining lease liabilities				$ 300,000		$ 300,000
Remaining operating lease right of use assets				200,000		$ 300,000
Impairment losses				$ 0	$ 0

Leases - Summary of Future Mini

Leases - Summary of Future Minimum Lease Payments Under Operating Sublease (Details) $ in Thousands	Mar. 31, 2024 USD ($)
Leases [Abstract]
2024 (remaining nine months)	$ 256
Thereafter	0
Total future minimum lease payments	256
Less: amount representing interest	(4)
Present value of lease liabilities	$ 252
Operating Lease, Liability, Statement of Financial Position [Extensible Enumeration]	Accrued Expenses And Other Current Liabilities
Less: current portion of lease liabilities	$ (252)
Lease liabilities, non-current	$ 0

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 1,433	$ 1,413
Less: accumulated depreciation	(750)	(671)
Property and equipment, net	683	742
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 1,191	1,191
Property and equipment estimated useful life	5 years
Computer equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 242	$ 222
Property and equipment estimated useful life	3 years

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 79,000	$ 67,000

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Summary Of Accrued Expenses And Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued employee compensation costs	$ 1,808	$ 3,328
Accrued research and development costs	8,835	10,433
Lease liability	252	335
Accrued legal and professional fees	963	902
Other	446	364
Accrued expenses and other current liabilities	$ 12,304	$ 15,362

Common Stock - Additional Infor

Common Stock - Additional Information (Details)					3 Months Ended
	Mar. 31, 2024 USD ($) Vote $ / shares shares	Mar. 21, 2024 USD ($) $ / shares shares	Jun. 23, 2023 USD ($)	Feb. 23, 2023 USD ($) shares	Mar. 31, 2024 USD ($) Vote $ / shares shares	Mar. 31, 2023 USD ($) shares	Dec. 31, 2023 USD ($) $ / shares shares
Class of Stock [Line Items]
Shares issued				34,426,351
Business acquisition, exchange ratio				0.2951%
Shares issued upon conversion of preferred stock				18,216,847
Payments of stock issuance costs | $				$ 5,000,000		$ 4,955,000
Pre-merger financing amount | $				$ 164,500,000
Pre-merger financing shares issued				12,638,636
Common stock, shares authorized	100,000,000				100,000,000		100,000,000
Common stock, par value | $ / shares	$ 0.001				$ 0.001		$ 0.001
Common stock, shares issued	46,782,639			41,011,501	46,782,639		41,292,027
Common stock, shares outstanding	46,782,639			41,011,501	46,782,639		41,292,027
Shares subject to repurchase	60,830				60,830		86,153
Liability related to shares subject to repurchase | $	$ 300,000				$ 300,000		$ 400,000
Number of vote by common stock holders | Vote	1				1
Sales agreement
Class of Stock [Line Items]
Shares issued	0
Sales agreement | Maximum
Class of Stock [Line Items]
Common stock, aggregate offering price | $			$ 200,000,000
Pre-Funded Warrants
Class of Stock [Line Items]
Purchase of Shares	1,071,505	1,071,505			1,071,505
Purchase price per share | $ / shares		$ 0.001
Shares issued price per share | $ / shares		$ 13.999
Common Stock
Class of Stock [Line Items]
Shares issued						12,638,636
Private Placement
Class of Stock [Line Items]
Aggregate gross proceeds from issuance of cost | $		$ 90,000,000
Payments of stock issuance costs | $		$ 200,000
Private Placement | Common Stock
Class of Stock [Line Items]
Shares issued		5,357,144
Common stock per share | $ / shares		$ 14
Long-term liabilities
Class of Stock [Line Items]
Liability related to shares subject to repurchase | $	$ 100,000				$ 100,000		$ 100,000
Dividend Declared
Class of Stock [Line Items]
Dividends | $					0
Dividend Paid
Class of Stock [Line Items]
Dividends | $					$ 0

Common Stock - Following Shares

Common Stock - Following Shares of Common Stock Reserved for Future Issuance (Details) - shares	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Class of Stock [Line Items]
Issuance of common stock upon exercise of stock options	7,755,740	5,817,339
Issuance of common stock upon vesting of restricted stock units	95,817	78,505
Equity awards available for grant under equity plans	1,322,398	1,574,426
Common stock reserved for future issuance	9,983,845	7,873,027
Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock reserved for future issuance	809,890	402,757

Preferred Stock and Convertib_2

Preferred Stock and Convertible Preferred Stock - Additional Information (Details) - $ / shares	Feb. 23, 2023	Mar. 31, 2024	Dec. 31, 2023
Class Of Stock [Line Items]
Preferred stock, shares authorized		10,000,000	10,000,000
Preferred stock, par value		$ 0.001	$ 0.001
Business acquisition, exchange ratio	0.2951%
Preferred stock, shares issued		0	0
Preferred stock, shares outstanding		0	0
Merger Agreement
Class Of Stock [Line Items]
Business acquisition, common shares issued	34,426,351
Convertible Preferred Stock
Class Of Stock [Line Items]
Business acquisition, exchange ratio	0.2951%

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)			1 Months Ended	3 Months Ended		19 Months Ended
	Feb. 23, 2023	Mar. 11, 2020	Jun. 30, 2019	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2020	Dec. 31, 2023	Jul. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance				9,983,845			7,873,027
Stock issued during period, value, new issues					$ 159,544,000
Total compensation cost not yet recognized related to unvested stock options				$ 53,100,000
Expected to be recognized over a weighted-average period				3 years
Restricted Stock Awards | Enliven Inc.
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Granted			3,000,000
Restricted Stock Awards | Employees and Consultants | Enliven Inc.
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock shares issued						197,262
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total compensation cost not yet recognized related to unvested stock options				$ 1,300,000
Expected to be recognized over a weighted-average period				3 years 6 months
Number of Shares, Granted				20,000
2019 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance								0
2016 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance		0
2020 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance				1,322,398
Award expiration period from date of grant	10 years
Award vesting period	4 years
Number of shares of common stock that may be issued accordance with plan	4,275,000
Description of changes in the number of shares reserved for issuance				The number of shares reserved shall be annually increased on the first day of each fiscal year, beginning with the fiscal year commencing on January 1, 2024 and continuing until, and including, the fiscal year commencing January 1, 2032, equal to the least of (i) 4.5% of the number of shares of the Company’s common stock outstanding on the first day of such fiscal year and (ii) an amount determined by the Company’s board of directors.
Common stock outstanding percent	4.50%
2020 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance				809,890
Exercise price per share of stock options as percentage of fair market value of common stock		85%
Number of shares of common stock that may be issued accordance with plan	407,133
Common stock outstanding percent	1%
Stock issued during period, value, new issues				$ 0	$ 0
Share based compensation liability				216,000			$ 53,000
Total compensation cost not yet recognized related to unvested stock options				$ 100,000
Expected to be recognized over a weighted-average period				2 months 12 days

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Details)	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Compensation Related Costs [Abstract]
Stock Options Outstanding, Beginning Balance | shares	5,817,339
Stock Options Outstanding, Options granted | shares	2,089,517
Stock Options Outstanding, Options exercised and vested | shares	(151,116)
Stock Options Outstanding, Options cancelled and forfeited | shares	0
Stock Options Outstanding, Ending Balance | shares	7,755,740
Weighted-Average Exercise Price, Beginning Balance | $ / shares	$ 11.9
Weighted-Average Exercise Price, Options granted | $ / shares	14.86
Weighted-Average Exercise Price, Options exercised and vested | $ / shares	2.59
Weighted-Average Exercise Price, Options cancelled and forfeited | $ / shares	0
Weighted-Average Exercise Price, Ending Balance | $ / shares	$ 12.88

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Restricted Stock Award and Restricted Stock Units Activity (Details) - Restricted Stock Units	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Unvested, Beginning Balance | shares	78,505
Number of Shares, Granted | shares	20,000
Number of Shares, Vested | shares	(2,688)
Number of Shares, Forfeited | shares	0
Number of Shares, Unvested, Ending Balance | shares	95,817
Weighted-Average Grant Date Fair Value, Unvested, Beginning Balance | $ / shares	$ 14.28
Weighted-Average Grant Date Fair Value, Granted | $ / shares	14.85
Weighted-Average Grant Date Fair Value, Vested | $ / shares	17.56
Weighted-Average Grant Date Fair Value, Forfeited | $ / shares	0
Weighted-Average Grant Date Fair Value, Unvested, Ending Balance | $ / shares	$ 14.31

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Allocated share based compensation expense	$ 4,515	$ 2,262
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Allocated share based compensation expense	2,229	492
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Allocated share based compensation expense	$ 2,286	$ 1,770

Stock-Based Compensation - Su_4

Stock-Based Compensation - Summary of Stock-Based Compensation Fair Value Assumptions (Details)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield	0%
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)		5 years 9 months 18 days
Expected volatility	84%	83%
Risk-free interest rate		4.10%
Risk-free interest rate, minimum	4%
Risk-free interest rate, maximum	4.30%
Expected dividend yield	0%	0%
Minimum | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	5 years 8 months 12 days
Maximum | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	6 years 1 month 6 days

Net Loss Per Share (Additional

Net Loss Per Share (Additional Information) (Details) - shares	Mar. 31, 2024	Mar. 21, 2024
Pre-Funded Warrants
Earnings Per Share Basic [Line Items]
Purchase of Shares	1,071,505	1,071,505

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Basic and Diluted Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Numerator:
Net loss	$ (22,738)	$ (14,724)
Denominator:
Weighted-average common shares outstanding (including vested and unvested shares)	42,118,267	18,738,115
Less: weighted-average unvested common stock issued upon early exercise of common stock options	(68,244)	(149,069)
Less: weighted-average unvested restricted shares of common stock	(4,415)	(74,402)
Weighted-average shares outstanding, basic	42,045,608	18,514,644
Weighted-average shares outstanding, diluted	42,045,608	18,514,644
Net loss per share, basic	$ (0.54)	$ (0.8)
Net loss per share, diluted	$ (0.54)	$ (0.8)

Net Loss Per Share - Anti Dilut

Net Loss Per Share - Anti Dilutive Potential Common Shares Excluded From Computation of Diluted Net Loss Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Earnings Per Share Basic [Line Items]
Convertible preferred stock (as converted)	7,875,481	3,949,605
Stock Options Outstanding
Earnings Per Share Basic [Line Items]
Convertible preferred stock (as converted)	7,755,740	3,890,266
Unvested restricted stock awards
Earnings Per Share Basic [Line Items]
Convertible preferred stock (as converted)	2,493	59,339
Unvested Restricted Stock Units
Earnings Per Share Basic [Line Items]
Convertible preferred stock (as converted)	95,817	0
ESPP Shares Pending Issuance
Earnings Per Share Basic [Line Items]
Convertible preferred stock (as converted)	21,431	0

Subsequent Events - Additional

Subsequent Events - Additional Information (Details)	1 Months Ended	3 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Jun. 30, 2020 ft²
Subsequent Event [Line Items]
Area of rentable square feet of office and laboratory space | ft²				6,782
Lease and rental expense | $	$ 12,000	$ 81,000	$ 81,000