Upstream Bio (UPB) 10-Q 7 Nov 24 2024 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2024	Nov. 05, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Entity Registrant Name	UPSTREAM BIO, INC.
Trading Symbol	UPB
Entity Central Index Key	0002022626
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		53,596,601
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity File Number	001-42366
Entity Tax Identification Number	38-4187694
Entity Address, Address Line One	890 Winter Street
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	Waltham
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02451
City Area Code	781
Local Phone Number	208-2466
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ

Condensed consolidated balance

Condensed consolidated balance sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 32,948	$ 25,833
Short-term investments	187,711	83,977
Accounts receivable - related party	607	98
Prepaid expenses and other current assets	6,007	7,088
Total current assets	227,273	116,996
Property and equipment, net	578	159
Operating lease right-of-use assets	1,914	43
Deferred offering costs	2,741
Restricted cash	194
Total assets	232,700	117,198
Current liabilities:
Accounts payable	4,899	1,990
Accrued expenses and other current liabilities	5,297	4,480
Operating lease liabilities, current portion	678	45
Total current liabilities	10,874	6,515
Operating lease liabilities, net of current portion	1,263
Preferred stock tranche right liability		2,874
Total liabilities	12,137	9,389
Commitments and contingencies (Note 13)
Redeemable convertible preferred stock (Series A,B), $0.001 par value; 31,764,693 shares authorized at September 30, 2024 and December 31, 2023; 31,764,693 shares and 22,941,170 shares issued and outstanding at September 30, 2024 and December 31, 2023, respectively; aggregate liquidation preference $430,759 and $267,718 at September 30, 2024 and December 31, 2023, respectively	380,874	230,935
Stockholders' deficit:
Common stock, $0.001 par value; 40,684,346 shares and 40,664,346 shares authorized at September 30, 2024 and December 31, 2023, respectively; 3,025,452 and 2,992,479 shares issued and outstanding at September 30, 2024 and December 31, 2023, respectively	3	3
Additional paid-in capital	8,873	4,824
Accumulated other comprehensive income	351	21
Accumulated deficit	(169,538)	(127,974)
Total stockholders' deficit	(160,311)	(123,126)
Total liabilities, redeemable convertible preferred stock and stockholders' deficit	$ 232,700	$ 117,198

Condensed consolidated balanc_2

Condensed consolidated balance sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Redeemable convertible preferred stock, shares authorized	31,764,693	31,764,693
Redeemable convertible preferred stock, shares issued	31,764,693	22,941,170
Redeemable convertible preferred stock, shares outstanding	31,764,693	22,941,170
Redeemable convertible preferred stock, liquidation preference	$ 430,759	$ 267,718
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	40,684,346	40,664,346
Common stock, shares issued	3,025,452	2,992,479
Common stock, shares outstanding	3,025,452	2,992,479
Series A and B Redeemable Convertible Preferred Stock [Member]
Redeemable convertible preferred stock, par value	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	31,764,693	31,764,693
Redeemable convertible preferred stock, shares issued	31,764,693	22,941,170
Redeemable convertible preferred stock, shares outstanding	31,764,693	22,941,170
Redeemable convertible preferred stock, liquidation preference	$ 430,759	$ 267,718

Condensed consolidated statemen

Condensed consolidated statements of operations and comprehensive loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Statement [Abstract]
Collaboration revenue - related party	$ 607	$ 621	$ 1,757	$ 1,930
Operating expenses:
Research and development	15,433	7,788	41,193	20,245
General and administrative	4,067	2,219	12,010	7,469
Total operating expenses	19,500	10,007	53,203	27,714
Loss from operations	(18,893)	(9,386)	(51,446)	(25,784)
Other income (expense):
Change in fair value of preferred stock tranche right liabilities		4,773	2,859	14,542
Interest income	2,904	1,527	7,047	2,646
Other expense, net	(3)	(16)	(24)	(108)
Total other income, net	2,901	6,284	9,882	17,080
Net loss	(15,992)	(3,102)	(41,564)	(8,704)
Redeemable convertible preferred stock cumulative dividends	(5,041)	(3,151)	(13,041)	(14,567)
Net loss attributable to common stockholders	$ (21,033)	$ (6,253)	$ (54,605)	$ (23,271)
Net loss per share attributable to common stockholders, basic	$ (6.96)	$ (2.11)	$ (18.15)	$ (7.9)
Net loss per share attributable to common stockholders, diluted	$ (6.96)	$ (2.11)	$ (18.15)	$ (7.9)
Weighted-average common shares outstanding, basic	3,023,155	2,958,727	3,009,234	2,944,804
Weighted-average common shares outstanding, diluted	3,023,155	2,958,727	3,009,234	2,944,804
Comprehensive loss:
Net loss	$ (15,992)	$ (3,102)	$ (41,564)	$ (8,704)
Unrealized gain (loss) on investments, net of tax	406	(19)	330	(77)
Comprehensive loss	$ (15,586)	$ (3,121)	$ (41,234)	$ (8,781)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Deficit (Unaudited) - USD ($) $ in Thousands	Total	Redeemable Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Temporary equity, beginning balance at Dec. 31, 2022		$ 112,823
Temporary equity, beginning balance, shares at Dec. 31, 2022		12,000,000
Beginning balance at Dec. 31, 2022	$ (106,155)		$ 3	$ 1,279	$ (107,437)
Beginning balance, shares at Dec. 31, 2022			2,937,197
Issuance of Series A redeemable convertible preferred stock in connection with the settlement of the tranche right liability		$ 80,320
Issuance of Series A redeemable convertible preferred stock in connection with the settlement of the tranche right liability, shares		8,000,000
Stock-based compensation expense	1,304			1,304
Net loss	(3,062)				(3,062)
Temporary equity, ending balance at Mar. 31, 2023		$ 193,143
Temporary equity, ending balance, shares at Mar. 31, 2023		20,000,000
Ending balance at Mar. 31, 2023	(107,913)		$ 3	2,583	(110,499)
Ending balance, shares at Mar. 31, 2023			2,937,197
Temporary equity, beginning balance at Dec. 31, 2022		$ 112,823
Temporary equity, beginning balance, shares at Dec. 31, 2022		12,000,000
Beginning balance at Dec. 31, 2022	(106,155)		$ 3	1,279	(107,437)
Beginning balance, shares at Dec. 31, 2022			2,937,197
Unrealized gain (loss) on available-for-sale securities, net of tax	(77)
Net loss	(8,704)
Temporary equity, ending balance at Sep. 30, 2023		$ 230,935
Temporary equity, ending balance, shares at Sep. 30, 2023		22,941,170
Ending balance at Sep. 30, 2023	(112,204)		$ 3	4,011	(116,141)	$ (77)
Ending balance, shares at Sep. 30, 2023			2,971,499
Temporary equity, beginning balance at Mar. 31, 2023		$ 193,143
Temporary equity, beginning balance, shares at Mar. 31, 2023		20,000,000
Beginning balance at Mar. 31, 2023	(107,913)		$ 3	2,583	(110,499)
Beginning balance, shares at Mar. 31, 2023			2,937,197
Issuance of Series B redeemable convertible preferred stock in connection with the settlement of the tranche right liability, net of issuance costs		$ 37,842
Issuance of Series B redeemable convertible preferred stock in connection with the settlement of the tranche right liability, net of issuance costs, shares		2,941,170
Exercise of stock options, net of tax withholding	18			18
Exercise of stock options, net of tax withholding, shares			5,245
Stock-based compensation expense	627			627
Unrealized gain (loss) on available-for-sale securities, net of tax	(58)					(58)
Net loss	(2,540)				(2,540)
Temporary equity, ending balance at Jun. 30, 2023		$ 230,985
Temporary equity, ending balance, shares at Jun. 30, 2023		22,941,170
Ending balance at Jun. 30, 2023	(109,866)		$ 3	3,228	(113,039)	(58)
Ending balance, shares at Jun. 30, 2023			2,942,442
Series B redeemable convertible preferred stock issuance costs		$ (50)
Exercise of stock options, net of tax withholding	100			100
Exercise of stock options, net of tax withholding, shares			29,057
Stock-based compensation expense	683			683
Unrealized gain (loss) on available-for-sale securities, net of tax	(19)					(19)
Net loss	(3,102)				(3,102)
Temporary equity, ending balance at Sep. 30, 2023		$ 230,935
Temporary equity, ending balance, shares at Sep. 30, 2023		22,941,170
Ending balance at Sep. 30, 2023	(112,204)		$ 3	4,011	(116,141)	(77)
Ending balance, shares at Sep. 30, 2023			2,971,499
Temporary equity, beginning balance at Dec. 31, 2023	$ 230,935	$ 230,935
Temporary equity, beginning balance, shares at Dec. 31, 2023	22,941,170	22,941,170
Beginning balance at Dec. 31, 2023	$ (123,126)		$ 3	4,824	(127,974)	21
Beginning balance, shares at Dec. 31, 2023			2,992,479
Exercise of stock options, net of tax withholding	12			12
Exercise of stock options, net of tax withholding, shares			3,563
Stock-based compensation expense	643			643
Unrealized gain (loss) on available-for-sale securities, net of tax	(42)					(42)
Net loss	(10,894)				(10,894)
Temporary equity, ending balance at Mar. 31, 2024		$ 230,935
Temporary equity, ending balance, shares at Mar. 31, 2024		22,941,170
Ending balance at Mar. 31, 2024	(133,407)		$ 3	5,479	(138,868)	(21)
Ending balance, shares at Mar. 31, 2024			2,996,042
Temporary equity, beginning balance at Dec. 31, 2023	$ 230,935	$ 230,935
Temporary equity, beginning balance, shares at Dec. 31, 2023	22,941,170	22,941,170
Beginning balance at Dec. 31, 2023	$ (123,126)		$ 3	4,824	(127,974)	21
Beginning balance, shares at Dec. 31, 2023			2,992,479
Unrealized gain (loss) on available-for-sale securities, net of tax	330
Net loss	(41,564)
Temporary equity, ending balance at Sep. 30, 2024	$ 380,874	$ 380,874
Temporary equity, ending balance, shares at Sep. 30, 2024	31,764,693	31,764,693
Ending balance at Sep. 30, 2024	$ (160,311)		$ 3	8,873	(169,538)	351
Ending balance, shares at Sep. 30, 2024			3,025,452
Temporary equity, beginning balance at Mar. 31, 2024		$ 230,935
Temporary equity, beginning balance, shares at Mar. 31, 2024		22,941,170
Beginning balance at Mar. 31, 2024	(133,407)		$ 3	5,479	(138,868)	(21)
Beginning balance, shares at Mar. 31, 2024			2,996,042
Issuance of Series B redeemable convertible preferred stock in connection with the settlement of the tranche right liability, net of issuance costs		$ 149,939
Issuance of Series B redeemable convertible preferred stock in connection with the settlement of the tranche right liability, net of issuance costs, shares		8,823,523
Exercise of stock options, net of tax withholding	100			100
Exercise of stock options, net of tax withholding, shares			24,504
Stock-based compensation expense	1,412			1,412
Unrealized gain (loss) on available-for-sale securities, net of tax	(34)					(34)
Net loss	(14,678)				(14,678)
Temporary equity, ending balance at Jun. 30, 2024		$ 380,874
Temporary equity, ending balance, shares at Jun. 30, 2024		31,764,693
Ending balance at Jun. 30, 2024	(146,607)		$ 3	6,991	(153,546)	(55)
Ending balance, shares at Jun. 30, 2024			3,020,546
Exercise of stock options, net of tax withholding	19			19
Exercise of stock options, net of tax withholding, shares			4,906
Stock-based compensation expense	1,863			1,863
Unrealized gain (loss) on available-for-sale securities, net of tax	406					406
Net loss	(15,992)				(15,992)
Temporary equity, ending balance at Sep. 30, 2024	$ 380,874	$ 380,874
Temporary equity, ending balance, shares at Sep. 30, 2024	31,764,693	31,764,693
Ending balance at Sep. 30, 2024	$ (160,311)		$ 3	$ 8,873	$ (169,538)	$ 351
Ending balance, shares at Sep. 30, 2024			3,025,452

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Deficit (Parenthetical) (Unaudited) - Series B Redeemable Convertible Preferred Stock - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Redeemable convertible preferred stock tranche right liability		$ 11,774
Redeemable convertible preferred stock issuance costs	$ 75	$ 385

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities:
Net loss		$ (41,564)	$ (8,704)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense		40	46
Stock-based compensation expense		3,918	2,614
Change in fair value of preferred stock tranche right liabilities		(2,859)	(14,542)
Net amortization of premiums and accretion of discounts on short-term investments		(2,337)	(1,012)
Non-cash lease expense		51	59
Changes in operating assets and liabilities:
Accounts receivable - related party		(509)	147
Prepaid expenses and other assets		1,081	(282)
Accounts payable		2,888	(479)
Accrued expenses and other current liabilities		(243)	(217)
Deferred revenue - related party			616
Operating lease liabilities		(26)	(62)
Net cash used in operating activities		(39,560)	(21,816)
Cash flows from investing activities:
Purchases of short-term investments		(248,400)	(94,194)
Maturities of short-term investments		147,333	16,738
Purchases of property and equipment		(326)	(144)
Net cash used in investing activities		(101,393)	(77,600)
Cash flows from financing activities:
Proceeds from exercises of stock options		131	118
Payments of deferred offering costs		(1,793)
Net cash provided by financing activities		148,262	129,683
Net increase in cash, cash equivalents and restricted cash		7,309	30,267
Cash, cash equivalents and restricted cash at beginning of period		25,833	17,051
Cash, cash equivalents and restricted cash at end of period		33,142	47,318
Cash, cash equivalents and restricted cash at end of period:
Cash and cash equivalents		32,948	47,318
Restricted cash		194
Total cash, cash equivalents and restricted cash at end of period		33,142	47,318
Supplemental cash flow information:
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability		1,922	33
Supplemental disclosure of non-cash investing and financing activities:
Deferred offering costs included in accounts payable and accrued expenses		948
Purchases of property and equipment included in accounts payable and accrued expenses		133
Series A Redeemable Convertible Preferred Stock
Cash flows from financing activities:
Proceeds from the issuance of preferred stock	[1]		80,000
Series B Redeemable Convertible Preferred Stock
Cash flows from financing activities:
Proceeds from the issuance of preferred stock		149,924	49,565
Series A Preferred Stock
Supplemental disclosure of non-cash investing and financing activities:
Settlement of preferred stock tranche right liability			$ 320
Series B Preferred Stock
Supplemental disclosure of non-cash investing and financing activities:
Settlement of preferred stock tranche right liability		$ 15
[1] Includes related party amount of $ 10.0 million for the nine months ended September 30, 2023 (Note 16).

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (Parenthetical) - Series A Redeemable Convertible Preferred Stock $ in Thousands	9 Months Ended
	Sep. 30, 2023 USD ($)
Proceeds from the issuance of preferred stock	$ 80,000	[1]
Related Party
Proceeds from the issuance of preferred stock	$ 10,000
[1] Includes related party amount of $ 10.0 million for the nine months ended September 30, 2023 (Note 16).

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (15,992)	$ (14,678)	$ (10,894)	$ (3,102)	$ (2,540)	$ (3,062)	$ (41,564)	$ (8,704)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Sep. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business and Basis of Presentation	1. Nature of the business and basis of presentation Upstream Bio, Inc. was incorporated in April 2021, under the laws of the State of Delaware, and along with its consolidated subsidiary (collectively, the “Company” or “Upstream”), is focused on developing treatments for inflammatory diseases, with an initial focus on severe respiratory disorders. Since its inception, the Company has devoted substantially all of its efforts to raising capital and incurring research and development expenses related to advancing verekitug, a clinical-stage monoclonal antibody that targets and inhibits the Thymic Stromal Lymphopoietin receptor. Risks and uncertainties The global economy has experienced extreme volatility and disruptions due to the military conflict between Russia and Ukraine and the war between Israel and Hamas. These conditions have impacted, and may continue to impact, the capital and credit markets, which may reduce the Company’s ability to raise additional capital through equity, equity-linked instruments or debt financings which could negatively impact the Company’s short-term and long-term liquidity. Additionally, the Company’s results of operations could be adversely affected by general conditions in the global economy and financial markets. A severe or prolonged economic downturn could result in a variety of risks to the Company’s business, including a reduced ability to raise additional capital when needed on favorable terms, if at all. The Federal Reserve raised the federal funds interest rates during 2022 and 2023 in order to mitigate persistent inflation. During September 2024, the Federal Reserve effected a reduction to the federal funds interest rate, the impact of which is not yet clear. Higher interest rates, coupled with reduced government spending and volatility in financial markets, may increase economic uncertainty and affect consumer spending. Any of the foregoing could harm the Company’s business, and it cannot anticipate all of the ways in which the current economic climate and financial market conditions could adversely impact its ability to raise capital, business, results of operations and financial condition. The Company is subject to risks and uncertainties common to early-stage companies in the biopharmaceutical industry, including, but not limited to, the successful development of verekitug, the development of new technological innovations by competitors, dependence on key personnel, the ability to attract and retain qualified employees, protection of proprietary technology, compliance with governmental regulations and the ability to secure additional capital to fund operations and commercial success of verekitug. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be maintained, that any therapeutic products developed will obtain required regulatory approval or that any approved or consumer products will be commercially viable. Even if the Company’s development efforts are successful, it is uncertain when, if ever, the Company will generate significant product sales. Stock split On October 4, 2024, the Company effected a 1.049 -for-one stock split of its issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios of each series of the Company’s preferred stock (see Notes 8 and 17). Accordingly, all share and per share amounts for all periods presented in the accompanying condensed consolidated financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect this stock split and adjustment of the preferred stock conversion ratios. Liquidity The Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year from the issuance of these condensed consolidated financial statements. The accompanying condensed consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. The Company has historically financed its operations principally through the issuance and sale of Series A redeemable convertible preferred stock (“Series A Preferred Stock”) and Series B redeemable convertible preferred stock (“Series B Preferred Stock”), which are collectively referred to as the “Preferred Stock.” The Company has incurred recurring losses and negative cash flows from operations since its inception and expects to continue to incur losses and negative cash flows for the foreseeable future as it continues the research and development of verekitug. The Company incurred net losses of $ 41.6 million and $ 8.7 million for the nine months ended September 30, 2024 and 2023, respectively. As of September 30, 2024 , the Company had an accumulated deficit of $ 169.5 million. In October 2024, the Company completed its initial public offering (“IPO” ) of its common stock. In connection with its IPO, the Company issued and sold 17,250,000 shares of common stock, including 2,250,000 shares pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a price to the public of $ 17.00 per share. As a result of the IPO, the Company received approximately $ 268.7 million in net proceeds, after deducting $ 20.5 million in underwriting discounts and commissions, and approximately $ 4.0 million in other offering costs. The Company expects its cash, cash equivalents and short-term investments will be sufficient to fund its operating expenses and capital expenditure requirements for at least the next twelve months from the date of issuance of these condensed consolidated financial statements. The Company will need additional financing to support its continuing operations and pursue its growth strategy. Until such time as the Company can generate significant product revenue, if ever, the Company expects to fund its operations through equity offerings or debt financings, credit or loan facilities, potentially other capital resources, or a combination of one or more of these funding sources. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. The Company’s failure to raise capital as and when needed could have a negative impact on its financial condition and its ability to pursue its business strategies. If adequate funds are not available to the Company, the Company may be required to delay, reduce or eliminate clinical programs, obtain funds through arrangements with collaborators on terms unfavorable to the Company or pursue merger or acquisition strategies. There can be no assurances the Company will be able to obtain additional funding. Although management continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all. Basis of presentation The accompanying unaudited condensed consolidated financial statements reflect the operations of the Company. Intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial reporting and as required by Regulation S-X, Rule 10-01. 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”). The condensed consolidated interim financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair statement of the Company’s financial position as of September 30, 2024 and the results of operations for the three and nine month interim periods ended September 30, 2024 and 2023. The condensed balance sheet as of December 31, 2023 was derived from audited annual financial statements but does not include all disclosures required by U.S. GAAP. The results of operations for the interim periods are not necessarily indicative of results to be expected for the year ending December 31, 2024, any other interim periods, or any future year or period.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Other than policies noted below, there have been no significant changes from the significant accounting policies and estimates disclosed in Note 2 of the “Notes to Consolidated Financial Statements” in our audited annual financial statements included in the Company's IPO final prospectus filed pursuant to Rule 424(b)(4) under the Securities Act with the Securities and Exchange Commission (the “SEC”) on October 11, 2024. Use of estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. The Company assesses estimates on an ongoing basis; however, actual results could materially differ from those estimates. Significant estimates and assumptions reflected within these condensed consolidated financial statements include, but are not limited to, prepaid and accrued research and development expenses, including those related to contract research organizations (“CROs”), contract manufacturing organizations (“CMOs”) and other third-party vendors, the valuation of the Company’s common stock and stock-based awards and the valuation of the preferred stock tranche right liabilities. Changes in estimates are recorded in the period in which they become known. Concentration of credit risk and of significant suppliers Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents and short-term investments. The Company deposits its cash and cash equivalents in financial institutions in amounts that may exceed federally insured limits, and has not experienced any losses on such accounts and does not believe it is exposed to any unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company’s short-term investments consist of U.S. treasury bills and U.S. government agency bonds which the Company believes represent minimal credit risk. The Company is dependent on third-party manufacturers to supply products for research and development activities related to verekitug, including preclinical and clinical studies and testing. In particular, the Company relies and expects to continue to rely on a small number of manufacturers for the supply of verekitug. The Company’s preclinical and clinical studies and testing could be adversely affected by a significant interruption in the supply. Cash and cash equivalents The Company considers all short-term, highly liquid investments, with an original maturity of three months or less, to be cash equivalents, and includes amounts held in money market funds in the amount of $ 32.5 million and $ 23.3 million as of September 30, 2024 and December 31, 2023 , respectively. Restricted cash Restricted cash consisted of a letter of credit totaling $ 0.2 million as of September 30, 2024, that is required to be maintained in connection with the Company's lease arrangements. The letter of credit is in the name of the Company's landlord and is required to fulfill lease requirements in the event the Company should default on its lease obligations. As of September 30, 2024, the Company classified its restricted cash as non-current assets on the condensed consolidated balance sheet based on the release date of the restriction. The Company did not hold a letter of credit as of December 31, 2023. Short-term investments Available-for-sale securities consist of investments with original maturities greater than 90 days at acquisition date. The Company classifies any investments with maturities beyond one year as short term, based on their highly liquid nature and because such available-for-sale securities represent the investment of cash that is available for current operations. The Company’s debt security investments are classified as available-for-sale and are carried at fair value, with the unrealized gains and losses reported as a component of accumulated other comprehensive income (loss) in stockholders’ deficit. Realized gains and losses and declines in fair value due to credit-related factors are based on the specific identification method and are included as other expense, net in the condensed consolidated statements of operations and comprehensive loss. The Company recorded interest income on available-for-sale investments of $ 2.9 million and $ 7.0 million, and $ 1.5 million and $ 2.6 million for the three and nine months ended September 30, 2024 and the three and nine months ended September 30, 2023, respectively, which is classified as interest income in the condensed consolidated statements of operations and comprehensive loss. 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 other expense, net. The Company evaluates 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. The Company also 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, changes to the underlying credit ratings and forecasted recovery, among other factors. The credit-related portion of unrealized losses, and any subsequent improvements, are recorded in other expense, net. The portion that is not credit-related is treated in accordance with other unrealized losses as a component of accumulated other comprehensive income (loss) in stockholders’ deficit. There have been no impairment or credit losses recognized during any of the periods presented. Deferred offering costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded as a reduction of the proceeds from the offering, either as a reduction of the carrying value of the Preferred Stock or in stockholders’ deficit as a reduction of additional paid-in-capital generated as a result of the offering. Should the planned equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the condensed consolidated statements of operations and comprehensive loss. The Company recorded deferred offering costs of $ 2.7 million and $ 0 as of September 30, 2024 and December 31, 2023 , respectively. Recently issued accounting pronouncements not yet adopted In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures (“ASU 2023-07”). 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. All disclosure requirements under ASU 2023-07 are also required for public entities with a single reportable segment. ASU 2023-07 is effective for public business entities with fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. The Company is currently evaluating the impact of adopting ASU 2023-07 on its consolidated financial statements and related disclosures. In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures (“ASU 2023-09”). ASU 2023-09 requires entities to disclose additional information in specified categories with respect to the reconciliation of the effective tax rate to the statutory rate (the rate reconciliation) for federal, state, and foreign income taxes. It also requires greater detail about individual reconciling items in the rate reconciliation to the extent the impact of those items exceeds a specified threshold (if the effect of those reconciling items is equal to or greater than 5% of the amount computed by multiplying pretax income or loss by the applicable statutory income tax rate). In addition to new disclosures associated with the rate reconciliation, ASU 2023-09 requires information pertaining to taxes paid (net of refunds received) to be disaggregated for federal, state, and foreign taxes and further disaggregated for specific jurisdictions to the extent the related amounts exceed a quantitative threshold. The amendments are effective for public business entities for annual periods beginning after December 15, 2024. For entities other than public business entities, the amendments are effective for annual periods beginning after December 15, 2025. Early adoption is permitted. The Company is currently evaluating the timing and impact of adopting ASU 2023-09 on its consolidated financial statements and related disclosures. In November 2024, the FASB issued an ASU to require more detailed information about specified categories of expenses (purchases of inventory, employee compensation, depreciation, amortization, and depletion) included in certain expense captions presented on the face of the income statement. This ASU is effective for fiscal years beginning after December 15, 2026, and for interim periods within fiscal years beginning after December 15, 2027. Early adoption is permitted. The amendments may be applied either (1) prospectively to financial statements issued for reporting periods after the effective date of this ASU or (2) retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating the impact of adopting this ASU on its consolidated financial statements and related disclosures.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair value measurements The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicate the level of the fair value hierarchy used to determine such fair values (in thousands): Fair Value Measurements at Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 32,492 $ — $ — $ 32,492 Short-term investments: U.S. treasury bills — 93,275 — 93,275 U.S. government agency bonds — 94,436 — 94,436 $ 32,492 $ 187,711 $ — $ 220,203 Fair Value Measurements at Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 23,314 $ — $ — $ 23,314 Short-term investments: U.S. treasury bills — 45,864 — 45,864 U.S. government agency bonds — 38,113 — 38,113 $ 23,314 $ 83,977 $ — $ 107,291 Liabilities: Preferred stock tranche right liability (Series B) $ — $ — $ 2,874 $ 2,874 For the three and nine months ended September 30, 2024 and for the year ended December 31, 2023 , there were no transfers between Level 1, Level 2 and Level 3. The Company classifies its U.S. treasury bills and U.S. government agency bonds as short-term based on each instrument’s availability for use in current operations. The fair value of the Company’s U.S. treasury bills and U.S. government agency bonds are classified as Level 2 because they are valued using observable inputs to quoted market prices, benchmark yields, reported trades, broker/dealer quotes or alternative pricing sources with reasonable levels of price transparency. Short-term investments consisted of the following (in thousands): September 30, 2024 Amortized Unrealized Unrealized Fair Short-term investments: U.S. treasury bills $ 93,201 $ 81 $ ( 7 ) $ 93,275 U.S. government agency bonds 94,160 276 — 94,436 Total short-term investments: $ 187,361 $ 357 $ ( 7 ) $ 187,711 December 31, 2023 Amortized Unrealized Unrealized Fair Short-term investments: U.S. treasury bills $ 45,863 $ 9 $ ( 8 ) $ 45,864 U.S. government agency bonds 38,093 23 ( 3 ) 38,113 Total short-term investments: $ 83,956 $ 32 $ ( 11 ) $ 83,977 The contractual maturities of the Company’s short-term investments in available-for-sale securities held were as follows (in thousands): September 30, December 31, Due within one year $ 157,861 $ 83,977 Due after one year through two years 29,850 — Total available-for-sale securities $ 187,711 $ 83,977 Valuation of preferred stock tranche right liabilities As of December 31, 2023, the preferred stock tranche right liability in the table above is composed of the fair value of the obligation to issue Series B Preferred Stock (Note 8). The fair value of the preferred stock tranche right liabilities was based on significant inputs not observable in the market, which represented a Level 3 measurement within the fair value hierarchy. Series A preferred stock tranche right liability In February 2023, upon satisfaction of certain conditions, the second closing of the Series A Preferred Stock was completed. The Company issued and sold 8,000,000 shares of Series A Preferred Stock at a price of $ 10.00 per share, which resulted in the settlement of the associated Series A preferred stock tranche right liability. The fair value of Series A Preferred Stock was $ 10.04 per share upon the second closing. Series B preferred stock tranche right liability The fair value of the Series B preferred stock tranche right liability was determined using an option pricing model as it represents an option for the Series B Option Shares (as defined in Note 8). The valuation considered as inputs the estimated fair value of the Series B Preferred Stock as of each valuation date, the risk-free interest rate, volatility, expected dividends, and estimated time to the tranche closing. The most significant assumption in the valuation model impacting the fair value of the preferred stock tranche right liability is the fair value of the Company’s Series B Preferred Stock as of each measurement date. The Company determined the fair value per share of the underlying Series B Preferred Stock by taking into consideration the most recent sales of its Series B Preferred Stock, results obtained from third-party valuations and additional factors the Company deemed relevant. In June 2023, the initial tranche of the Series B Preferred Stock closed with a fair value of $ 13.00 per share. As of December 31, 2023 , the fair value of Series B Preferred Stock was $ 15.86 per share. In April 2024, upon satisfaction of certain conditions, the Company issued and sold 8,823,523 shares of Series B Preferred Stock at a price of $ 17.00 per share, which resulted in the settlement of the associated Series B preferred stock tranche right liability. The fair value of Series B Preferred Stock was $17.002 per share upon the closing. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve for time periods approximately equal to the remaining estimated time to the tranche closing. The volatility is based on the historical volatility of publicly traded peer companies adjusted for the seniority of the Series B Preferred Stock. The expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future. Changes in these inputs can have a significant impact on the fair value of the preferred stock tranche right liability. The following table presents the assumptions used in the option-pricing model to determine the fair value of the Series B preferred stock tranche right liability during the periods presented: 2023 June (Issuance Date) June 30, December 31, Expected volatility 51.0 % 36.2 % 21.2 % Expected dividends 0.0 % 0.0 % 0.0 % Expected term (in years) 0.80 0.75 0.25 Risk-free rate 5.3 % 5.4 % 5.4 % The following table presents a roll-forward of the fair value of the Series B preferred stock tranche right liability during the nine months ended September 30, 2024, for which fair value is determined using Level 3 inputs (in thousands): Series B Preferred Fair value at December 31, 2023 $ 2,874 Change in fair value of Series B preferred stock tranche right liability ( 2,859 ) Final settlement of Series B preferred stock tranche right liability ( 15 ) Fair value at September 30, 2024 $ - The following table presents a roll-forward of the fair value of the Series A and Series B preferred stock tranche right liabilities during the nine months ended September 30, 2023, for which fair value is determined using Level 3 inputs (in thousands): Preferred Stock Series A Series B Fair value at December 31, 2022 $ 6,947 $ — Fair value of Series B preferred stock tranche right liability at — 11,774 Change in fair value of preferred stock tranche right liabilities ( 6,627 ) ( 7,915 ) Final settlement of Series A preferred stock tranche right ( 320 ) — Fair value at September 30, 2023 $ — $ 3,859

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	9 Months Ended
	Sep. 30, 2024
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid Expenses and Other Current Assets	4. Prepaid expenses and other current assets Prepaid expenses and other current assets consisted of the following (in thousands): September 30, December 31, 2024 2023 Prepaid research and development expense $ 5,076 $ 6,436 Interest receivable 485 138 Prepaid employee-related costs 58 123 Other 388 391 $ 6,007 $ 7,088

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2024
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	5. Property and equipment, net Property and equipment, net consisted of the following (in thousands): September 30, December 31, 2024 2023 Office equipment $ 163 $ 163 Computer equipment 141 36 Leasehold improvements 59 27 Construction in progress 322 — 685 226 Less: Accumulated depreciation and amortization ( 107 ) ( 67 ) Property and equipment, net $ 578 $ 159 Depreciation and amortization expense related to property and equipment, net was less than $ 0.1 million for each of the three and nine months ended September 30, 2024 and 2023 .

Accrued expenses and other curr

Accrued expenses and other current liabilities	9 Months Ended
	Sep. 30, 2024
Payables and Accruals [Abstract]
Accrued expenses and other current liabilities	6. Accrued expenses and other current liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): September 30, December 31, 2024 2023 Accrued employee compensation and benefits $ 1,999 $ 2,168 Accrued external research and development expenses 1,764 1,437 Accrued consultant and professional fees 747 875 Accrued offering costs 669 — Other 118 — $ 5,297 $ 4,480

Leases

Leases	9 Months Ended
	Sep. 30, 2024
Leases [Abstract]
Leases	7. Leases As of December 31, 2023, the Company was a party to a lease related to commercial real estate under a non-cancelable lease term and a short-term lease related to commercial real estate. In July 2024, the Company entered into an operating lease agreement for office space located at 890 Winter Street in Waltham, Massachusetts. The lease commenced in September 2024 and the Company began paying monthly rent starting one month after the lease commenced. The Company occupies approximately 16,801 square feet of space under a three-year agreement expiring in October 2027. Initial base rent is approximately $ 0.7 million for the first year and approximately $ 0.8 million for the second and third year. The Company previously had an operating lease for office space at 460 Totten Pond Road, Waltham, Massachusetts, for which it provided notice of termination in July 2024. This notice became effective on October 9, 2024 , after which the Company’s rights and obligations under this lease ceased. The lease expired on June 30, 2024 , after which the Company continued to pay rent on a month-to-month basis until October 9, 2024.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	9 Months Ended
	Sep. 30, 2024
Equity [Abstract]
Redeemable Convertible Preferred Stock	8. Redeemable convertible preferred stock The Company has issued Series A Preferred Stock and Series B Preferred Stock, which are collectively referred to as the Preferred Stock. As of September 30, 2024 and December 31, 2023 , the Company authorized the issuance of 31,764,693 shares of Preferred Stock, par value of $ 0.001 per share, of which 20,000,000 have been designated Series A Preferred Stock and 11,764,693 have been designated Series B Preferred Stock. Immediately prior to the closing of the Company’s IPO on October 15, 2024, pursuant to the stock split and a proportional adjustment to the existing conversion ratios of each series of the Company’s Preferred Stock as discussed further below, all of the Company’s outstanding shares of convertible preferred stock were converted into an aggregate of 33,321,149 shares of common stock. Issuance and sale of Series A redeemable convertible preferred stock In October 2021, the Company issued and sold 11,000,000 shares of Series A Preferred Stock at $ 10.00 per share. Pursuant to the Series A Preferred Stock Purchase Agreement (the “Series A Agreement”), the Company was obligated to issue and the Series A investors were obligated to purchase an additional 9,000,000 shares of Series A Preferred Stock (“Milestone Shares”) at the same purchase price of $ 10.00 per share (the “Series A preferred stock tranche right”), after the initial closing and upon the satisfaction of certain conditions at a date which would occur at the earlier of (i) immediately prior to the Company’s first underwritten public offering of its common stock under the Securities Act; (ii) the resolution of the board of directors that the pharmacokinetics, pharmacodynamics, immunogenicity and safety profile of verekitug (formerly referred to as ASP7266), when administered as multiple ascending doses, supports further clinical development (“Second Closing Milestone”) has been achieved; or (iii) the written consent of the purchasers holding a majority of the Series A Preferred Stock that the Second Closing Milestone has been waived (collectively, the “Second Closing”). The board of directors may determine at any time prior to the Second Closing to issue and sell up to 1,000,000 of the Milestone Shares at a price of $ 10.00 per share for gross cash proceeds of $ 10.0 million (“Interim Second Closing”) and the number of Milestone Shares to be issued in the Second Closing will be reduced accordingly. In October 2022, the Interim Second Closing was completed and 1,000,000 of the Milestone Shares on a pro-rata basis to the purchasers of the Series A Preferred Stock were issued at a price of $ 10.00 per share. In February 2023, upon the satisfaction of the Second Closing Milestone, the remaining 8,000,000 of the Milestone Shares on a pro-rata basis to the purchasers of the Series A Preferred Stock were issued at a price of $ 10.00 per share, which resulted in gross cash proceeds of $ 80.0 million. As a result of this issuance, the Series A preferred stock tranche right liability of $ 0.3 million was settled and the Series A Preferred Stock was recorded at its fair value of $ 80.3 million. Issuance and sale of Series B redeemable convertible preferred stock In June 2023, the Company executed the Series B Stock Preferred Purchase Agreement (the “Series B Agreement”) to issue and sell up to 11,764,693 shares of Series B Preferred Stock at a price of $ 17.00 per share. In the initial closing in June 2023, the Company issued 2,941,170 shares of Series B Preferred Stock resulting in gross cash proceeds of $ 50.0 million and incurred $ 0.6 million of issuance costs, of which $ 0.1 million was allocated to the preferred stock tranche right liability and recognized in the condensed consolidated statement of operations and comprehensive loss as general and administrative expense. Pursuant to the Series B Agreement, the Company has the right (“Series B Option”) to issue and sell an additional 8,823,523 shares of Series B Preferred Stock (“Series B Option Shares”) at the same price of $ 17.00 per share after the initial closing but prior to March 31, 2024 upon approval of at least six ( 6 ) board of directors of which at least one ( 1 ) has to be appointed by the holders of Series B Preferred Stock. If the Company does not exercise the Series B Option prior or at a date which would occur at the earlier of (i) March 31, 2024 or (ii) the closing of an acquisition agreement signed prior to March 31, 2024, the holders of Series B Preferred Stock will have the right but not obligation to require the Company to issue and sell the Series B Option Shares at the same purchase price of $ 17.00 per share (the “Series B preferred stock tranche right”). Upon the initial closing of the Series B Preferred Stock, the Company recorded a preferred stock tranche right liability of $ 11.8 million and a corresponding reduction to the carrying value of the Series B Preferred Stock. The fair value of the Series B preferred stock tranche right was allocated from the gross cash proceeds of $ 50.0 million of the Series B Preferred Stock issuance, and the residual value was then allocated to the Series B Preferred Stock. In April 2024, pursuant to the satisfaction of the Series B Option contemplated in the Series B Agreement, the Company issued and sold 8,823,523 shares of Series B Preferred Stock at a price of $ 17.00 per share, which resulted in gross cash proceeds of $ 150.0 million. As a result of this issuance, the Series B preferred stock tranche right liability of less than $ 0.1 million was settled and the Series B Preferred Stock was recorded at its fair value of $ 150.0 million. The Company incurred less than $ 0.1 million of issuance costs in connection with the Series B Option closing. Upon issuance of the Preferred Stock, the Company assessed the embedded conversion and liquidation features of the securities and determined that such features did not require the Company to separately account for these features. Preferred Stock consisted of the following (dollar amounts in thousands): September 30, 2024 Preferred Preferred Carrying Liquidation Common Stock Series A Preferred Stock 20,000,000 20,000,000 $ 193,143 $ 223,800 20,980,000 Series B Preferred Stock 11,764,693 11,764,693 187,731 206,959 12,341,149 31,764,693 31,764,693 $ 380,874 $ 430,759 33,321,149 December 31, 2023 Preferred Preferred Carrying Liquidation Common Stock Series A Preferred Stock 20,000,000 20,000,000 $ 193,143 $ 216,293 20,980,000 Series B Preferred Stock 11,764,693 2,941,170 37,792 51,425 3,085,280 31,764,693 22,941,170 $ 230,935 $ 267,718 24,065,280 The holders of the Preferred Stock have the following rights and preferences: Dividends The holders of Preferred Stock are entitled to a cumulative dividend from and after the date of the share issuance at the rate per annum of 5 % of the Original Issue Price (subject to appropriate adjustment in the event of any stock dividend, stock split, combination or other similar recapitalization with respect to the Preferred Stock), provided that the total accrued amount will not exceed 15 % of the Original Issue Price in aggregate (the “Accruing Dividend”). Such dividends shall be accrued, whether or not declared. In the event of any dividend being payable to common stockholders, the holders of Preferred Stock shall be entitled to receive, prior to any such dividend being paid to the common stockholders, the greater of (i) the Accruing Dividend then accrued and not previously paid, and (ii) the amount of any dividend being paid to the common stockholders (determined on an as-converted basis with respect to the holders of Preferred Stock). Voting rights The holders of the Preferred Stock are entitled to vote together with all other classes and series of stock as a single class on all matters, except those matters requiring a separate class vote, and are entitled to the number of votes equal to the number of shares of common stock into which each share of the applicable series of Preferred Stock is then convertible. The holders of Series A Preferred Stock as a separate class are entitled to elect four ( 4 ) board of directors, and the holders of Series B Preferred Stock as a separate class are entitled to elect two ( 2 ) board of directors. Liquidation preference In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company or in the event of a Deemed Liquidation Event (“DLE”) which is defined as a merger or consolidation in which the Company issues shares of its capital stock (other than one in which stockholders of the Company own a majority by voting power of the outstanding shares of the surviving or acquiring corporation), and the sale, lease, transfer, exclusive license or other disposition of substantially all of the Company’s assets, the holders of shares of Preferred Stock then outstanding shall be entitled to be paid out of the assets of the Company available for distribution to its shareholders or consideration payable to stockholders in such DLE or out of the available proceeds as follows: • Before any payment is made to the holders of Series A Preferred Stock and common stock, an amount equal to any Accruing Dividends on the Series B Preferred Stock accrued but unpaid, whether or not declared, together with any other dividends that are declared but unpaid (“Series B Dividend Payment”); • If the assets available are not sufficient for the Company to pay the Series B Dividend Payment to the holders of Series B Preferred Stock in full, holders of Series B Preferred Stock will share ratably in the assets available for distribution; • After the Series B Dividend Payment is paid in full, holders of Preferred Stock will be entitled to be paid out of the assets of the Company available for distribution to its stockholders before any payment is made to the holders of common stock, on a pari passu basis, an amount per share equal to (i) with respect to the Series A Preferred Stock, the greater of (a) the Original Issue Price, plus any Accruing Dividends on the Series A Preferred Stock accrued but unpaid, whether or not declared, together with any other dividends declared but unpaid, or (b) such amount per share as would have been payable had all shares of Series A Preferred Stock been converted in common stock, and (ii) with respect to the Series B Preferred Stock, (1) the greater of (a) the Original Issue Price, plus any Accruing Dividends on the Series B Preferred Stock accrued but unpaid, whether or not declared, together with any other dividends declared but unpaid thereon, or (b) such amount per share as would have been payable had all shares of Series B Preferred Stock been converted in common stock, less (2) Series B Dividend Payment that was paid. (“Liquidation Amount”); • If the assets available are not sufficient for the Company to pay holders of Preferred Stock the Liquidation Amount in full, holders of Preferred Stock will share ratably in the assets available for distribution; • After payment of Liquidation Amounts is paid in full to the holders of Preferred Stock, the remaining assets of the Company available for distribution to its stockholders, or in the case of a DLE, the consideration not payable to the holders of shares of Preferred Stock or the remaining available proceeds, will be distributed among the holders of the shares of common stock on a pro rata basis. The “Original Issue Price” is defined as (i) with respect to the Series A Preferred Stock, $ 10.00 per share, and (ii) with respect to the Series B Preferred Stock, $ 17.00 per share. Conversion Optional conversion Each share of Preferred Stock is convertible at the option of the holder and at any time into common stock as determined by dividing the Preferred Stock Original Issue Price by the Preferred Stock Conversion Price. “Conversion Price” is defined as initially the applicable Original Issue Price for the applicable series of Preferred Stock, subject to certain adjustments in the event of any down round, stock dividend, stock split, combination or other similar recapitalization. Mandatory conversion Each share of Preferred Stock will automatically be converted into shares of common stock, at the conversion ratio of dividing the Original Issue Price by the Preferred Stock Conversion Price, upon either (a) the closing of the sale of shares of common stock to the public at a price of at least $ 21.07 per share (subject to appropriate adjustment in the event of any stock dividend, stock split, combination or other similar recapitalization with respect to the common stock) in a firm commitment underwritten public offering pursuant to an effective registration statement under the Securities Act of 1933, as amended, resulting in at least $ 100.0 million of gross proceeds to the Company and after which the common stock is listed on the Nasdaq Global Market, the Nasdaq Global Select Market or the New York Stock Exchange or (b) the date and time, or the occurrence of an event specified by vote or written consent of the Requisite Holders (which is defined as at least a majority of the outstanding shares of Preferred Stock, voting together as a single class on an as converted to common stock basis, which majority must include holders of at least a majority of the outstanding shares of Series B Preferred Stock) voting together as a single class on an as converted to common stock basis, then all outstanding shares of Preferred Stock will automatically be converted into shares of common stock, at the then effective conversion rate and such shares of Preferred Stock may not be reissued by the Company. Special mandatory conversion Pursuant to the terms of the Series A Agreement, if a Series A Preferred Shareholder fails to purchase all of the Milestone Shares allocated to such shareholder at or prior to the Second Closing Milestone or breaches its obligations set forth in the Series A Agreement, then such investor will be deemed a Defaulting Purchaser. As of December 31, 2023, all of the Milestone Shares had been issued without triggering the special mandatory conversion provision under the Series A Agreement. Pursuant to the terms of the Series B Agreement, if a Series B Preferred Shareholder fails to purchase all of the Series B Option Shares allocated to such shareholder at or prior to the closing of the Series B Option or breaches its obligations set forth in the Series B Agreement, then such investor will be deemed a Defaulting Purchaser. Each ten shares of Preferred Stock held by the Defaulting Purchaser will automatically, and without any further action on the part of such holder, be converted into one share of common stock. In April 2024, all of the Series B Option Shares had been issued without triggering the special mandatory conversion provision under the Series B Agreement. Modification to Series A preferred stock In June 2023, in connection with the issuance of the Company’s Series B Preferred Stock, the rights of the Company’s Series A Preferred Stock were amended to entitle holders to a cumulative dividend from and after the date of the share issuance at the rate per annum of 5 % of the Original Issue Price (subject to appropriate adjustment in the event of any stock dividend, stock split, combination or other similar recapitalization with respect to the Preferred Stock), provided that the total accrued amount will not exceed 15 % of the Original Issue Price in aggregate. The dividend replaced the original accrued return definition within the liquidation preference terms of the Series A Preferred Stock. Previously, holders were entitled to a liquidation preference per share equal to the greater of (a) the Original Issue Price, plus an accrued return of 5 % of the Original Issue Price per annum, provided that the total of such accrued return shall not exceed 15 % of the Original Issue Price in the aggregate, or (b) such amount per share as would have been payable had all shares of Series A Preferred Stock been converted in common stock. The changes to the rights of the Company’s Series A Preferred Stock were not considered to be a significant change to the contractual terms of the Company’s Series A Preferred Stock because the accrued return of the liquidation preference and the cumulative dividend definitions will result in the same amount to be received in a liquidation event, and accordingly, the Company accounted for the change as a modification.

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2024
Equity [Abstract]
Common Stock	9. Common stock Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, as may be declared by the board of directors, if any, subject to the preferential dividend rights of the Preferred Stock. When dividends are declared on shares of common stock, the Company must declare at the same time a dividend payable to the holders of Preferred Stock equivalent to the dividend amount they would receive if each share of Preferred Stock were converted into common stock. The Company may not pay dividends to common stockholders until all dividends accrued or declared but unpaid on the Preferred Stock have been paid in full. As of September 30, 2024 and December 31, 2023 , no dividends were declared. As of September 30, 2024 and December 31, 2023 , the Company’s amended and restated certificate of incorporation authorized the issuance of 40,684,346 and 40,664,346 shares, respectively, of $ 0.001 par value common stock. As of September 30, 2024 and December 31, 2023 , there were 3,025,452 shares and 2,992,479 shares of common stock issued and outstanding, respectively. As of September 30, 2024 and December 31, 2023 , the Company had reserved 39,614,500 and 38,051,952 shares of common stock, respectively, for the conversion of shares of Preferred Stock into common stock (including committed but unissued shares under future tranche obligations for the Preferred Stock as of December 31, 2023), the exercise of outstanding stock options for common stock, and the issuance of common stock options remaining available for grant under its equity incentive plan. On October 4, 2024, the Company’s stockholders approved the third amended and restated certificate of incorporation, which was filed immediately prior to the closing of the IPO on October 15, 2024 and which, among other things, increased the number of shares of common stock authorized for issuance from 40,684,346 to 500,000,000 shares of common stock. In October 2024, the Company completed its IPO of its common stock. In connection with its IPO, the Company issued and sold 17,250,000 shares of common stock, including 2,250,000 shares sold pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a price to the public of $ 17.00 per share. As a result of the IPO, the Company received approximately $ 268.7 million in net proceeds, after deducting $ 20.5 million in underwriting discounts and commissions, and approximately $ 4.0 million in other offering costs.

Stock-based Compensation

Stock-based Compensation	9 Months Ended
	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Stock-based Compensation	10. Stock-based compensation Stock incentive plan The Company’s 2021 Stock Option and Grant Plan (the “2021 Plan”) provides for the Company to grant incentive stock options, nonqualified stock options, restricted stock awards, unrestricted stock awards and restricted stock units (collectively, the “Awards”) to among others, members of the board of directors, employees, consultants and other key persons to the Company and its affiliates. The 2021 Plan is administered by the board of directors, or at the discretion of the board of directors, by a committee of the board. As of September 30, 2024 and December 31, 2023 , the total number of shares of common stock reserved for issuance under the 2021 Plan was 6,360,626 shares and 4,765,105 shares, respectively. In April 2024, upon the satisfaction of the Series B Option contemplated in the Series B Agreement, the Company’s board of directors increased the number of shares of common stock reserved for issuance under the plan from 4,765,105 to 6,360,626 shares. As of September 30, 2024 and December 31, 2023 , 55,379 shares and 564,696 shares remain available for future grants, respectively. Shares of unused common stock underlying any Awards that are forfeited, canceled or reacquired by the Company prior to vesting will again be available for the grant of awards under the 2021 Plan. Shares underlying any awards that are forfeited, canceled, or reacquired by the Company prior to vesting, satisfied without the issuance of stock or otherwise terminated and shares that are withheld upon exercise of an option of settlement of an award to cover the exercise price or tax withholding shall be added back to the shares available for issuance under the 2021 Plan. 2024 Stock option and incentive plan On August 19, 2024, the Company’s board of directors adopted, and on October 4, 2024 its stockholders approved, the 2024 Stock Option and Incentive Plan (the “2024 Plan”), which became effective upon the date immediately preceding the date on which the IPO registration statement was declared effective by the SEC. The 2024 Plan allows the Company to make equity-based and cash-based incentive awards to its officers, employees, directors, and consultants. The 2024 Plan provides for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, restricted stock units, restricted shares of common stock and other stock-based awards. The number of shares initially reserved for issuance under the 2024 Plan is 3,180,000 shares. The number of shares reserved under the 2024 Plan is subject to adjustment in the event of a stock split, stock dividend or other change in the Company’s capitalization. In addition, the number of shares reserved and available for issuance under the 2024 Plan will automatically increase on January 1, 2025 and each January 1 thereafter, by five percent of the outstanding number of shares of its common stock on the immediately preceding December 31 or such lesser number of shares as determined by the Company’s compensation committee. The shares of common stock underlying any awards under the 2024 Plan and the 2021 Plan that are forfeited, cancelled, held back upon exercise or settlement of an award to satisfy the exercise price or tax withholding, reacquired by the Company prior to vesting, satisfied without the issuance of stock, expire or are otherwise terminated (other than by exercise) will be added back to the shares of common stock available for issuance under the 2024 Plan. 2024 Employee stock purchase plan On August 19, 2024, the Company’s board of directors adopted, and on October 4, 2024 its stockholders approved, the 2024 Employee Stock Purchase Plan (the “2024 ESPP”), which became effective on the date immediately preceding the date on which the IPO registration statement was declared effective by the SEC. A total of 488,467 shares of common stock were initially reserved for issuance to participating employees under this plan. The 2024 ESPP provides that the number of shares reserved and available for issuance will automatically increase on January 1, 2025 and each January 1 thereafter through January 1, 2034, by the least of (i) 976,934 shares of common stock, (ii) one percent of the outstanding number of shares of common stock on the immediately preceding December 31, or (iii) such lesser number of shares of common stock as determined by the administrator of the 2024 ESPP. The number of shares reserved under the 2024 ESPP is subject to adjustment in the event of a stock split, stock dividend or other change in the Company’s capitalization. Fair value inputs The following table presents, on a weighted-average basis, the assumptions used in the Black-Scholes option-pricing model to determine the fair value of stock options granted: Nine Months Ended September 30, 2024 2023 Per share fair value of common stock $ 6.19 $ 4.52 Expected volatility 78.0 % 77.0 % Expected dividends 0 % 0 % Expected term (in years) 6.3 6.3 Risk-free rate 3.35 % 1.94 % Stock options The Company generally grants stock-based awards with service-based vesting. During the nine months ended September 30, 2024 , the Company granted performance-based stock options to certain employees and directors for the purchase of an aggregate 1,206,249 shares of common stock with a vesting commencement date contingent upon the achievement of the Series B Option closing, which was achieved in April 2024. The Company determined that it met all the conditions to establish a grant date for these performance-based stock options at the original issuance date and that the performance condition was deemed probable of achievement, as the board of directors had approved the Series B Option closing prior to the grant date. The vesting of the performance-based stock options is also subject to the grantees’ continued service until the fourth anniversary of the Series B Option closing. The following table summarizes the activity of stock options with service-based and performance-based vesting conditions during the nine months ended September 30, 2024: Number of Weighted- Weighted- Intrinsic Value Outstanding as of December 31, 2023 4,166,107 $ 3.75 8.5 4,648 Granted 3,209,120 6.19 Exercised ( 32,973 ) 3.99 Forfeited or expired ( 1,104,280 ) 3.82 Outstanding as of September 30, 2024 6,237,974 $ 4.99 8.0 $ 35,091 Options exercisable September 30, 2024 1,861,312 $ 3.62 5.4 $ 13,028 Vested and expected to vest September 30, 2024 6,237,974 $ 4.99 8.0 $ 35,091 The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying stock options and the estimated fair value of the Company’s common stock for those stock options that had exercise prices lower than the estimated fair value of the Company’s common stock. The weighted-average grant-date fair value of options granted during the nine months ended September 30, 2024 and 2023 was $ 4.36 and $ 3.08 , respectively. As of September 30, 2024 , there was $ 14.1 million of total unrecognized compensation cost related to unvested stock options, which is expected to be recognized over a weighted-average period of 3.2 years. Modification of certain stock-based compensation awards In February 2024, the Company entered into a separation agreement with the Company’s former Chief Operating Officer (“COO”), effective March 2024. Under the terms of the separation agreement, stock options for the purchase of 142,935 shares of common stock, representing all of the vested options held by the former COO as of the date of her termination, became exercisable for one year following her termination. In March 2024, the Company entered into a separation agreement with the Company’s former Chief Executive Officer (“CEO”), effective March 2024. Under the terms of the separation agreement, vesting of options for the purchase of 38,245 shares of common stock held by the former CEO were accelerated with no change to the exercise price of such options. In addition, stock options for the purchase of 532,553 shares of common stock, representing all of the vested options held by the former CEO as of the date of her termination, became exercisable for two years following her termination. As a result of these modifications, the Company recognized $ 0.7 million of incremental stock-based compensation during the nine months ended September 30, 2024. The following table illustrates the classification of stock-based compensation in the condensed consolidated statements of operations and comprehensive loss (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 General and administrative 1,553 $ 421 3,082 $ 1,801 Research and development 310 262 836 813 $ 1,863 $ 683 $ 3,918 $ 2,614

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes The Company’s tax provision for interim periods is determined using an estimate of its annual effective tax rate, adjusted for discrete items, if any, that arise during the period. Each quarter, the Company updates its estimate of the annual effective tax rate and, if the estimated annual effective tax rate changes, the Company makes a cumulative adjustment in such period. No such adjustment was made as of September 30, 2024. The Company’s effective federal and state tax rate for the nine months ended September 30, 2024 and 2023 was 0 %, and the Company did no t record any income tax expense or benefit during the nine months ended September 30, 2024 and 2023 , primarily as a result of estimated net operating losses for the fiscal year to date offset by the increase in the valuation allowance against its deferred tax asset. All losses before income taxes arose in the United States.

Net loss per share

Net loss per share	9 Months Ended
	Sep. 30, 2024
Earnings Per Share [Abstract]
Net Loss per Share	12. Net loss per share Basic and diluted net loss per share attributable to common stockholders was calculated as follows (dollar amounts in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 Numerator: Net loss $ ( 15,992 ) $ ( 3,102 ) $ ( 41,564 ) $ ( 8,704 ) Preferred Stock cumulative dividends ( 5,041 ) ( 3,151 ) ( 13,041 ) ( 14,567 ) Net loss attributable to common stockholders $ ( 21,033 ) $ ( 6,253 ) $ ( 54,605 ) $ ( 23,271 ) Denominator: Weighted-average common shares outstanding, basic 3,023,155 2,958,727 3,009,234 2,944,804 Net loss per share attributable to common stockholders, $ ( 6.96 ) $ ( 2.11 ) $ ( 18.15 ) $ ( 7.90 ) Prior to June 2023, the Company’s Series A Preferred Stockholders were not entitled to cumulative dividends. In connection with the Series B Agreement in June 2023, the Company modified the dividend rights for its Series A Preferred Stockholders such that they became entitled to cumulative dividends based on the original issuance dates of the respective Series A Preferred Stock (Note 8). As such for the nine months ended September 30, 2023, the Company calculated its net loss attributable to common stockholders by adjusting its net loss for the aggregate cumulative dividends that had accrued since the original issuances dates in the period in which the Preferred Stockholders became legally entitled to such dividends. For the nine months ended September 30, 2024, the Company calculated its net loss attributable to common stockholders by adjusting its net loss for the aggregate cumulative dividends that accrued during the period. The Company’s potentially dilutive securities, which include stock options to purchase common stock and Preferred Stock, have been excluded from the computation of diluted net loss per share as the effect would be anti-dilutive. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The following potentially dilutive securities have been excluded from the calculation of diluted net loss per share due to their anti-dilutive effect: As of September 30, 2024 2023 Preferred Stock (as converted to common stock) (1) 33,321,149 24,065,280 Stock options to purchase common stock 6,237,974 4,188,618 39,559,123 28,253,898 (1) For the nine months ended September 30, 2023 , the Preferred Stock excludes 8,823,523 shares of Series B Preferred Stock (or 9,255,869 shares as converted to common stock) that were contingently issuable upon settlement of the Series B preferred stock tranche right liability (Note 8).

Commitments and contingencies

Commitments and contingencies	9 Months Ended
	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	13. Commitments and contingencies Legal matters The Company is subject to contingent liabilities, such as legal proceedings and claims, that arise in the ordinary course of business activities. The Company accrues for loss contingencies when losses become probable and are reasonably estimable. If the reasonable estimate of the loss is a range and no amount within the range is a better estimate, the minimum amount of the range is recorded as a liability on the condensed consolidated balance sheets. The Company does not accrue for contingent losses that, in its judgment, are considered to be reasonably possible, but not probable; however, it discloses the range of reasonably possible losses. As of September 30, 2024 and December 31, 2023 , the Company was not a party to any material legal proceedings or claims and no liabilities were recorded for loss contingencies. Contracts The Company enters into contracts in the normal course of business with various third parties for preclinical research studies, clinical trials, testing, manufacturing, and other services. These contracts generally provide for termination upon notice and are cancellable without significant penalty or payment, and do not contain any minimum purchase commitments. Guarantees and indemnifications In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out 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 all 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 that could have a material effect on its financial position, results of operations or cash flows, and it has not accrued any liabilities related to such obligations in its condensed consolidated financial statements as of September 30, 2024 and December 31, 2023 .

License Agreements

License Agreements	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License Agreements	14. License agreements License agreement with Lonza In October 2021, in connection with an asset purchase agreement entered into with Astellas Pharma, Inc. (“Astellas”), the Company and Lonza Sales AG (“Lonza”) entered into a license agreement (as amended, the “Lonza License Agreement”). Pursuant to the Lonza License Agreement, the Company obtained a worldwide, non-exclusive, sublicensable (subject to Lonza’s right of pre-approval with respect to any sublicense of manufacturing activities) license to certain intellectual property rights owned by Lonza. Lonza was the originator of the master cell bank for verekitug (formerly referred to as ASP7266 and UPB-101, collectively referred to as “the Compound”) developed by Astellas. As consideration for the rights and licenses granted to the Company under the Lonza License Agreement, the Company agreed to pay Lonza certain royalties and annual payments, both payable in Swiss francs, in respect of the manufacturing and sale of the Compound, such amounts to be determined by the party manufacturing the Compound, and range from no annual payment to up to a mid-six-figure annual payment, and a less-than-one percent to a low-single-digit percentage royalty on net sales of the Compound. In accordance with the Lonza License Agreement, the Company entered into a sublicense with Wuxi Biologics (Hong Kong) Limited to manufacture the Compound, requiring the Company to pay a mid-six-figure annual fee to Lonza pursuant to this provision. Any royalties due under the Lonza License Agreement are payable on a country-by-country basis until ten years from the first commercial sale of the Compound in that particular country. During the nine months ended September 30, 2024 and 2023 , the Company did no t make any royalty payments to Lonza under the Lonza License Agreement. The Lonza agreement continues for an indefinite period of time unless otherwise terminated. The Company has the right to terminate the Lonza License Agreement at any time by providing prior written notice to Lonza. During the nine months ended September 30, 2024 and 2023 , the Company made an annual payment in the amount of $ 0.5 million and $ 0.4 million, respectively, to Lonza pursuant to the Lonza License Agreement and recognized it as research and development expense in the condensed consolidated statements of operations and comprehensive loss.

Revenue

Revenue	9 Months Ended
	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Revenue	15. Revenue Maruho agreement In October 2021, in connection with an asset purchase agreement entered into with Astellas, the Company entered into an agreement (as amended, the “Maruho Agreement”), under which it granted Maruho an exclusive, irrevocable, perpetual, royalty-free, sublicensable (subject to its right of first negotiation) license. Pursuant to the Maruho Agreement, the Company maintains its responsibility for and controls the global research and development of the Maruho license product, including in Japan. The Company will conduct specified clinical trial activities for Japan as part of its global research and development plan. Maruho will reimburse the Company for the costs of these research and development activities, including the cost of drug supply. Maruho has the right to terminate the Maruho Agreement at any time by providing 60 days prior written notice to the Company with no substantial penalty. The Company concluded that Maruho is a customer under the Maruho Agreement, and as such, the Maruho Agreement falls within the scope of ASC 606. The Company identified one performance obligation under the Maruho Agreement related to the performance of research and development services, which are an output of the Company’s ordinary activities, in Japan. The Company determined that the transaction price of the Maruho Agreement as of September 30, 2024 consisted solely of variable consideration. The variable consideration was estimated using the expected value method based on the Company’s experience and best judgment of the total reimbursable costs expected to be incurred through the period of performance. The transaction price is being recognized as revenue over time using the cost-to-cost input method, which the Company believes best depicts the transfer of control to the customer. Under the cost-to-cost input method, the extent of progress towards completion is measured based on the ratio of actual costs incurred in Japan to the total estimated costs expected to satisfy the performance obligation. The calculation of the total estimated costs to fulfill the performance obligation includes costs associated with employees, clinical and development, manufacturing, and out-of-pocket costs expected to be paid to third parties. The estimate of the Company’s measure of progress and estimate of variable consideration to be included in the transaction price will be updated at each reporting period as a change in estimate. The Company excludes disclosures related to the aggregate amount of the transaction price allocated to the performance obligation that are unsatisfied as of the end of the reporting period because the contract has an initial expected term of one year or less. The Company currently expects to continue providing research and development services to Maruho under the Maruho Agreement through the completion of its Phase 2 clinical trials, and if successful, through any Phase 3 clinical trials. During the nine months ended September 30, 2023, the Company received a prepayment of $ 2.4 million from Maruho for research and development services to be provided by the Company under the Maruho Agreement. During the nine months ended September 30, 2023 , the Company recognized $ 1.8 million of related revenue from the prepayments, resulting in $ 0.6 million in deferred revenue as of September 30, 2023 . There was no deferred revenue as of December 31, 2022 . The Company did no t receive any prepayments or recognize any deferred revenue during the nine months ended September 30, 2024 .

Related Parties

Related Parties	9 Months Ended
	Sep. 30, 2024
Related Party Transactions [Abstract]
Related Parties	16. Related parties In October 2021, the Company entered into the Maruho Agreement (Note 15). Maruho is considered to be a related party because it is one of the co-founders of the Company and has representation on the Company’s board of directors. During the nine months ended September 30, 2024 and 2023 , the Company received payments of $ 1.2 million and $ 2.7 million, respectively, in cost reimbursements from Maruho. The Company recorded related party collaboration revenue of $ 0.6 million during each of the three months ended September 30, 2024 and 2023 . The Company recorded related party collaboration revenue of $ 1.8 million and $ 1.9 million during the nine months ended September 30, 2024 and 2023, respectively. As of September 30, 2024 and 2023, there was $ 0.6 million and $ 0.3 million in related party accounts receivable, respectively, representing amounts due for qualifying reimbursable expenses related to the Maruho Agreement. In February 2023, the Company issued 1,000,000 shares of Series A Preferred Stock to Maruho for gross proceeds of $ 10.0 million.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2024
Subsequent Events [Abstract]
Subsequent Events	17. Subsequent events Stock split On October 4, 2024, the Company effected a 1.049 -for-one stock split of its issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios of each series of the Company’s preferred stock (see Note 8). Accordingly, all share and per share amounts for all periods presented in the accompanying condensed consolidated financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect this stock split and adjustment of the preferred stock conversion ratios. In connection with the stock split, the Company’s board of directors adopted, and its stockholders approved, the third amended and restated certificate of incorporation, which, among other things, increased the number of shares of common stock authorized for issuance to 500,000,000 shares of common stock. Written consent for the conversion of preferred stock On October 4, 2024, the Company obtained written consent from the Requisite Holders (as defined in the Company’s second amended and restated certificate of incorporation) for the conversion of the preferred stock into common stock in connection with the Company’s IPO (see Note 8). Upon the closing of the IPO, 31,764,693 shares of outstanding convertible preferred stock were automatically converted into 33,321,149 shares of common stock, after the effect of the 1.049 -for-one stock split, with the related carrying value of $ 380.9 million reclassified to common stock and additional paid-in capital. Initial public offering In October 2024, the Company completed its IPO of its common stock. In connection with its IPO, the Company issued and sold 17,250,000 shares of its common stock, including 2,250,000 shares pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a price to the public of $ 17.00 per share. As a result of the IPO, the Company received approximately $ 268.7 million in net proceeds, after deducting $ 20.5 million in underwriting discounts and commissions, and approximately $ 4.0 million in other offering costs.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2024
Policy Text Block [Abstract]
Use of Estimates	Use of estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. The Company assesses estimates on an ongoing basis; however, actual results could materially differ from those estimates. Significant estimates and assumptions reflected within these condensed consolidated financial statements include, but are not limited to, prepaid and accrued research and development expenses, including those related to contract research organizations (“CROs”), contract manufacturing organizations (“CMOs”) and other third-party vendors, the valuation of the Company’s common stock and stock-based awards and the valuation of the preferred stock tranche right liabilities. Changes in estimates are recorded in the period in which they become known.
Concentration of Credit Risk and of Significant Suppliers	Concentration of credit risk and of significant suppliers Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents and short-term investments. The Company deposits its cash and cash equivalents in financial institutions in amounts that may exceed federally insured limits, and has not experienced any losses on such accounts and does not believe it is exposed to any unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company’s short-term investments consist of U.S. treasury bills and U.S. government agency bonds which the Company believes represent minimal credit risk. The Company is dependent on third-party manufacturers to supply products for research and development activities related to verekitug, including preclinical and clinical studies and testing. In particular, the Company relies and expects to continue to rely on a small number of manufacturers for the supply of verekitug. The Company’s preclinical and clinical studies and testing could be adversely affected by a significant interruption in the supply.
Cash and Cash Equivalents	Cash and cash equivalents The Company considers all short-term, highly liquid investments, with an original maturity of three months or less, to be cash equivalents, and includes amounts held in money market funds in the amount of $ 32.5 million and $ 23.3 million as of September 30, 2024 and December 31, 2023 , respectively.
Restricted Cash	Restricted cash Restricted cash consisted of a letter of credit totaling $ 0.2 million as of September 30, 2024, that is required to be maintained in connection with the Company's lease arrangements. The letter of credit is in the name of the Company's landlord and is required to fulfill lease requirements in the event the Company should default on its lease obligations. As of September 30, 2024, the Company classified its restricted cash as non-current assets on the condensed consolidated balance sheet based on the release date of the restriction. The Company did not hold a letter of credit as of December 31, 2023.
Short-Term Investments	Short-term investments Available-for-sale securities consist of investments with original maturities greater than 90 days at acquisition date. The Company classifies any investments with maturities beyond one year as short term, based on their highly liquid nature and because such available-for-sale securities represent the investment of cash that is available for current operations. The Company’s debt security investments are classified as available-for-sale and are carried at fair value, with the unrealized gains and losses reported as a component of accumulated other comprehensive income (loss) in stockholders’ deficit. Realized gains and losses and declines in fair value due to credit-related factors are based on the specific identification method and are included as other expense, net in the condensed consolidated statements of operations and comprehensive loss. The Company recorded interest income on available-for-sale investments of $ 2.9 million and $ 7.0 million, and $ 1.5 million and $ 2.6 million for the three and nine months ended September 30, 2024 and the three and nine months ended September 30, 2023, respectively, which is classified as interest income in the condensed consolidated statements of operations and comprehensive loss. 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 other expense, net. The Company evaluates 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. The Company also 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, changes to the underlying credit ratings and forecasted recovery, among other factors. The credit-related portion of unrealized losses, and any subsequent improvements, are recorded in other expense, net. The portion that is not credit-related is treated in accordance with other unrealized losses as a component of accumulated other comprehensive income (loss) in stockholders’ deficit. There have been no impairment or credit losses recognized during any of the periods presented.
Deferred Offering Costs	Deferred offering costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded as a reduction of the proceeds from the offering, either as a reduction of the carrying value of the Preferred Stock or in stockholders’ deficit as a reduction of additional paid-in-capital generated as a result of the offering. Should the planned equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the condensed consolidated statements of operations and comprehensive loss. The Company recorded deferred offering costs of $ 2.7 million and $ 0 as of September 30, 2024 and December 31, 2023 , respectively.
Recently Issued Accounting Pronouncements Not Yet Adopted	Recently issued accounting pronouncements not yet adopted In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures (“ASU 2023-07”). 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. All disclosure requirements under ASU 2023-07 are also required for public entities with a single reportable segment. ASU 2023-07 is effective for public business entities with fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. The Company is currently evaluating the impact of adopting ASU 2023-07 on its consolidated financial statements and related disclosures. In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures (“ASU 2023-09”). ASU 2023-09 requires entities to disclose additional information in specified categories with respect to the reconciliation of the effective tax rate to the statutory rate (the rate reconciliation) for federal, state, and foreign income taxes. It also requires greater detail about individual reconciling items in the rate reconciliation to the extent the impact of those items exceeds a specified threshold (if the effect of those reconciling items is equal to or greater than 5% of the amount computed by multiplying pretax income or loss by the applicable statutory income tax rate). In addition to new disclosures associated with the rate reconciliation, ASU 2023-09 requires information pertaining to taxes paid (net of refunds received) to be disaggregated for federal, state, and foreign taxes and further disaggregated for specific jurisdictions to the extent the related amounts exceed a quantitative threshold. The amendments are effective for public business entities for annual periods beginning after December 15, 2024. For entities other than public business entities, the amendments are effective for annual periods beginning after December 15, 2025. Early adoption is permitted. The Company is currently evaluating the timing and impact of adopting ASU 2023-09 on its consolidated financial statements and related disclosures. In November 2024, the FASB issued an ASU to require more detailed information about specified categories of expenses (purchases of inventory, employee compensation, depreciation, amortization, and depletion) included in certain expense captions presented on the face of the income statement. This ASU is effective for fiscal years beginning after December 15, 2026, and for interim periods within fiscal years beginning after December 15, 2027. Early adoption is permitted. The amendments may be applied either (1) prospectively to financial statements issued for reporting periods after the effective date of this ASU or (2) retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating the impact of adopting this ASU on its consolidated financial statements and related disclosures.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Schedule of Financial Assets and Liabilities Measured at Fair Value	The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicate the level of the fair value hierarchy used to determine such fair values (in thousands): Fair Value Measurements at Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 32,492 $ — $ — $ 32,492 Short-term investments: U.S. treasury bills — 93,275 — 93,275 U.S. government agency bonds — 94,436 — 94,436 $ 32,492 $ 187,711 $ — $ 220,203 Fair Value Measurements at Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 23,314 $ — $ — $ 23,314 Short-term investments: U.S. treasury bills — 45,864 — 45,864 U.S. government agency bonds — 38,113 — 38,113 $ 23,314 $ 83,977 $ — $ 107,291 Liabilities: Preferred stock tranche right liability (Series B) $ — $ — $ 2,874 $ 2,874
Schedule of Short-Term Investments	Short-term investments consisted of the following (in thousands): September 30, 2024 Amortized Unrealized Unrealized Fair Short-term investments: U.S. treasury bills $ 93,201 $ 81 $ ( 7 ) $ 93,275 U.S. government agency bonds 94,160 276 — 94,436 Total short-term investments: $ 187,361 $ 357 $ ( 7 ) $ 187,711 December 31, 2023 Amortized Unrealized Unrealized Fair Short-term investments: U.S. treasury bills $ 45,863 $ 9 $ ( 8 ) $ 45,864 U.S. government agency bonds 38,093 23 ( 3 ) 38,113 Total short-term investments: $ 83,956 $ 32 $ ( 11 ) $ 83,977
Schedule of Contractual Maturities of Short-term Investments	The contractual maturities of the Company’s short-term investments in available-for-sale securities held were as follows (in thousands): September 30, December 31, Due within one year $ 157,861 $ 83,977 Due after one year through two years 29,850 — Total available-for-sale securities $ 187,711 $ 83,977
Schedule of Assumptions Used in Option-Pricing Model to Determine Fair Value of Series B Preferred Stock Tranche Right Liability	The following table presents, on a weighted-average basis, the assumptions used in the Black-Scholes option-pricing model to determine the fair value of stock options granted: Nine Months Ended September 30, 2024 2023 Per share fair value of common stock $ 6.19 $ 4.52 Expected volatility 78.0 % 77.0 % Expected dividends 0 % 0 % Expected term (in years) 6.3 6.3 Risk-free rate 3.35 % 1.94 %
Roll-forward of Fair Value of the Series A and Series B Preferred Stock Tranche Right Liability Using Level 3 Inputs	The following table presents a roll-forward of the fair value of the Series B preferred stock tranche right liability during the nine months ended September 30, 2024, for which fair value is determined using Level 3 inputs (in thousands): Series B Preferred Fair value at December 31, 2023 $ 2,874 Change in fair value of Series B preferred stock tranche right liability ( 2,859 ) Final settlement of Series B preferred stock tranche right liability ( 15 ) Fair value at September 30, 2024 $ - The following table presents a roll-forward of the fair value of the Series A and Series B preferred stock tranche right liabilities during the nine months ended September 30, 2023, for which fair value is determined using Level 3 inputs (in thousands): Preferred Stock Series A Series B Fair value at December 31, 2022 $ 6,947 $ — Fair value of Series B preferred stock tranche right liability at — 11,774 Change in fair value of preferred stock tranche right liabilities ( 6,627 ) ( 7,915 ) Final settlement of Series A preferred stock tranche right ( 320 ) — Fair value at September 30, 2023 $ — $ 3,859
Series B Preferred Stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Schedule of Assumptions Used in Option-Pricing Model to Determine Fair Value of Series B Preferred Stock Tranche Right Liability	The following table presents the assumptions used in the option-pricing model to determine the fair value of the Series B preferred stock tranche right liability during the periods presented: 2023 June (Issuance Date) June 30, December 31, Expected volatility 51.0 % 36.2 % 21.2 % Expected dividends 0.0 % 0.0 % 0.0 % Expected term (in years) 0.80 0.75 0.25 Risk-free rate 5.3 % 5.4 % 5.4 %

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	9 Months Ended
	Sep. 30, 2024
Prepaid Expense and Other Assets, Current [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following (in thousands): September 30, December 31, 2024 2023 Prepaid research and development expense $ 5,076 $ 6,436 Interest receivable 485 138 Prepaid employee-related costs 58 123 Other 388 391 $ 6,007 $ 7,088

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2024
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following (in thousands): September 30, December 31, 2024 2023 Office equipment $ 163 $ 163 Computer equipment 141 36 Leasehold improvements 59 27 Construction in progress 322 — 685 226 Less: Accumulated depreciation and amortization ( 107 ) ( 67 ) Property and equipment, net $ 578 $ 159

Accrued expenses and other cu_2

Accrued expenses and other current liabilities (Tables)	9 Months Ended
	Sep. 30, 2024
Payables and Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): September 30, December 31, 2024 2023 Accrued employee compensation and benefits $ 1,999 $ 2,168 Accrued external research and development expenses 1,764 1,437 Accrued consultant and professional fees 747 875 Accrued offering costs 669 — Other 118 — $ 5,297 $ 4,480

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock (Tables)	9 Months Ended
	Sep. 30, 2024
Equity [Abstract]
Schedule of Preferred Stock	Preferred Stock consisted of the following (dollar amounts in thousands): September 30, 2024 Preferred Preferred Carrying Liquidation Common Stock Series A Preferred Stock 20,000,000 20,000,000 $ 193,143 $ 223,800 20,980,000 Series B Preferred Stock 11,764,693 11,764,693 187,731 206,959 12,341,149 31,764,693 31,764,693 $ 380,874 $ 430,759 33,321,149 December 31, 2023 Preferred Preferred Carrying Liquidation Common Stock Series A Preferred Stock 20,000,000 20,000,000 $ 193,143 $ 216,293 20,980,000 Series B Preferred Stock 11,764,693 2,941,170 37,792 51,425 3,085,280 31,764,693 22,941,170 $ 230,935 $ 267,718 24,065,280

Net Loss per Share (Tables)

Net Loss per Share (Tables)	9 Months Ended
	Sep. 30, 2024
Earnings Per Share [Abstract]
Summary of Basic and Diluted Net Loss per Share Attributable to Common Stockholders	Basic and diluted net loss per share attributable to common stockholders was calculated as follows (dollar amounts in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 Numerator: Net loss $ ( 15,992 ) $ ( 3,102 ) $ ( 41,564 ) $ ( 8,704 ) Preferred Stock cumulative dividends ( 5,041 ) ( 3,151 ) ( 13,041 ) ( 14,567 ) Net loss attributable to common stockholders $ ( 21,033 ) $ ( 6,253 ) $ ( 54,605 ) $ ( 23,271 ) Denominator: Weighted-average common shares outstanding, basic 3,023,155 2,958,727 3,009,234 2,944,804 Net loss per share attributable to common stockholders, $ ( 6.96 ) $ ( 2.11 ) $ ( 18.15 ) $ ( 7.90 )
Schedule of Dilutive Securities Excluded from Calculation of Diluted Net Loss per Share	The following potentially dilutive securities have been excluded from the calculation of diluted net loss per share due to their anti-dilutive effect: As of September 30, 2024 2023 Preferred Stock (as converted to common stock) (1) 33,321,149 24,065,280 Stock options to purchase common stock 6,237,974 4,188,618 39,559,123 28,253,898 (1) For the nine months ended September 30, 2023 , the Preferred Stock excludes 8,823,523 shares of Series B Preferred Stock (or 9,255,869 shares as converted to common stock) that were contingently issuable upon settlement of the Series B preferred stock tranche right liability (Note 8).

Stock-based Compensation (Table

Stock-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Schedule of Assumptions Used in Black-Scholes Option-pricing Model to Determine the Fair Value of Stock Options Granted	The following table presents, on a weighted-average basis, the assumptions used in the Black-Scholes option-pricing model to determine the fair value of stock options granted: Nine Months Ended September 30, 2024 2023 Per share fair value of common stock $ 6.19 $ 4.52 Expected volatility 78.0 % 77.0 % Expected dividends 0 % 0 % Expected term (in years) 6.3 6.3 Risk-free rate 3.35 % 1.94 %
Summary of Stock Options Activity	The following table summarizes the activity of stock options with service-based and performance-based vesting conditions during the nine months ended September 30, 2024: Number of Weighted- Weighted- Intrinsic Value Outstanding as of December 31, 2023 4,166,107 $ 3.75 8.5 4,648 Granted 3,209,120 6.19 Exercised ( 32,973 ) 3.99 Forfeited or expired ( 1,104,280 ) 3.82 Outstanding as of September 30, 2024 6,237,974 $ 4.99 8.0 $ 35,091 Options exercisable September 30, 2024 1,861,312 $ 3.62 5.4 $ 13,028 Vested and expected to vest September 30, 2024 6,237,974 $ 4.99 8.0 $ 35,091
Schedule of Classification of Stock-based Compensation in Condensed Consolidated Statements of Operations and Comprehensive Loss	The following table illustrates the classification of stock-based compensation in the condensed consolidated statements of operations and comprehensive loss (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 General and administrative 1,553 $ 421 3,082 $ 1,801 Research and development 310 262 836 813 $ 1,863 $ 683 $ 3,918 $ 2,614

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended						9 Months Ended
	Oct. 04, 2024	Oct. 31, 2024 USD ($) $ / shares shares	Sep. 30, 2024 USD ($)	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Product Information [Line Items]
Net Income (Loss)			$ (15,992)	$ (14,678)	$ (10,894)	$ (3,102)	$ (2,540)	$ (3,062)	$ (41,564)	$ (8,704)
Accumulated deficit			$ (169,538)						$ (169,538)		$ (127,974)
Subsequent Events
Product Information [Line Items]
Stock split ratio	1.049
IPO | Subsequent Events
Product Information [Line Items]
Sale of stock, number of shares issued | shares		17,250,000
Sale of stock, price per share | $ / shares		$ 17
Proceeds from IPO		$ 268,700
Underwriting discounts and commissions		20,500
Other offering costs		$ 4,000
Over Allotment Option | Subsequent Events
Product Information [Line Items]
Sale of stock, number of shares issued | shares		2,250,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Change in Accounting Estimate [Line Items]
Cash and cash equivalents	$ 32,500,000		$ 32,500,000		$ 23,300,000
Letter of credit	200,000		200,000
Interest income	2,900,000	$ 1,500,000	7,000,000	$ 2,600,000
Deferred offering costs	$ 2,700,000		$ 2,700,000		$ 0

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Shor-term investments	$ 187,711	$ 83,977
Fair Value on Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		107,291
Fair Value on Recurring Basis | Preferred Stock Tranche Right Liability (Series B)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities		2,874
Fair Value on Recurring Basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	32,492	23,314
Fair Value on Recurring Basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	187,711	83,977
Fair Value on Recurring Basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	220,203
Fair Value on Recurring Basis | Level 3 | Preferred Stock Tranche Right Liability (Series B)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities		2,874
Fair Value on Recurring Basis | Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	32,492	23,314
Fair Value on Recurring Basis | Money Market Funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	32,492	23,314
Fair Value on Recurring Basis | U.S. Treasury Bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Shor-term investments	93,275	45,864
Fair Value on Recurring Basis | U.S. Treasury Bills | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Shor-term investments	93,275	45,864
Fair Value on Recurring Basis | U.S. Government Agency Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Shor-term investments	94,436	38,113
Fair Value on Recurring Basis | U.S. Government Agency Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Shor-term investments	$ 94,436	$ 38,113

Fair Value Measurements - Sch_2

Fair Value Measurements - Schedule of Short-Term Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	$ 187,361	$ 83,956
Unrealized Gains	357	32
Unrealized Losses	(7)	(11)
Fair Value	187,711	83,977
U.S. Treasury Bills
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	93,201	45,863
Unrealized Gains	81	9
Unrealized Losses	(7)	(8)
Fair Value	93,275	45,864
U.S. Government Agency Bonds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	94,160	38,093
Unrealized Gains	276	23
Unrealized Losses		(3)
Fair Value	$ 94,436	$ 38,113

Fair Value Measurements - Sch_3

Fair Value Measurements - Schedule of Contractual Maturities of Short-term Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Due within one year	$ 157,861	$ 83,977
Due after one year through two years	29,850
Total available-for-sale securities	$ 187,711	$ 83,977

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended
	Apr. 30, 2024	Feb. 28, 2023	Sep. 30, 2024	Sep. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Debt Securities, Available-for-Sale [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset,Transfers, Net			$ 0	$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net, Total			$ 0	$ 0	$ 0
Series A Preferred Stock
Debt Securities, Available-for-Sale [Line Items]
Sale of stock, number of shares issued		8,000,000
Preferred stock, par value		$ 10
Preferred stock, par value second closing		$ 10.04
Series B Preferred Stock
Debt Securities, Available-for-Sale [Line Items]
Sale of stock, number of shares issued	8,823,523
Preferred stock, par value	$ 17				$ 15.86	$ 13

Fair Value Measurements - Sch_4

Fair Value Measurements - Schedule of Assumptions Used in Option-Pricing Model to Determine Fair Value of Series B Preferred Stock Tranche Right Liability (Details)			1 Months Ended	9 Months Ended
	Dec. 31, 2023	Jun. 30, 2023	Jun. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected volatility				78%	77%
Expected dividends				0%	0%
Expected term (in years)				6 years 3 months 18 days	6 years 3 months 18 days
Risk-free rate				3.35%	1.94%
Series B Preferred Stock
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected volatility	21.20%	36.20%	51%
Expected dividends	0%	0%	0%
Expected term (in years)	3 months	9 months	9 months 18 days
Risk-free rate	5.40%	5.40%	5.30%

Fair Value Measurements - Roll-

Fair Value Measurements - Roll-forward of Fair Value of the Series A and Series B Preferred Stock Tranche Right Liability Using Level 3 Inputs (Details) - Level 3 - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Series A Preferred Stock [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value at beginning balance		$ 6,947
Change in fair value of preferred stock tranche right liabilities		(6,627)
Final settlement of Series A and Series B preferred stock tranche right liability		(320)
Series B Preferred Stock [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value at beginning balance	$ 2,874
Fair value of Series B preferred stock tranche right liability at issuance		11,774
Change in fair value of preferred stock tranche right liabilities	(2,859)	(7,915)
Final settlement of Series A and Series B preferred stock tranche right liability	$ (15)
Fair value at ending balance		$ 3,859

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid research and development expense	$ 5,076	$ 6,436
Interest receivable	485	138
Prepaid employee-related costs	58	123
Other	388	391
Prepaid expenses and other current assets	$ 6,007	$ 7,088

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property Plant and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 685	$ 226
Less: Accumulated depreciation and amortization	(107)	(67)
Property and equipment, net	578	159
Office Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	163	163
Computer Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	141	36
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	59	$ 27
Construction in Progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 322

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Property, Plant and Equipment [Line Items]
Depreciation and amortization			$ 40,000	$ 46,000
Maximum
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 100,000	$ 100,000	$ 100,000	$ 100,000

Accrued expenses and other cu_3

Accrued expenses and other current liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued employee compensation and benefits	$ 1,999	$ 2,168
Accrued external research and development expenses	1,764	1,437
Accrued consultant and professional fees	747	875
Accrued offering costs	669
Other	118
Accrued expenses and other current liabilities	$ 5,297	$ 4,480

Leases - Additional Information

Leases - Additional Information (Details) $ in Millions	9 Months Ended
	Sep. 30, 2024 USD ($) ft²
Leases [Abstract]
Lease description	In July 2024, the Company entered into an operating lease agreement for office space located at 890 Winter Street in Waltham, Massachusetts. The lease commenced in September 2024 and the Company began paying monthly rent starting one month after the lease commenced.
Area of real estate property | ft²	16,801
Operating lease, term of contract	3 years
Rent payment, year one	$ 0.7
Rent payment, year two	0.8
Rent payment, year three	$ 0.8
Operating lease effective date	Oct. 09, 2024
Lease expired date	Jun. 30, 2024

Redeemable Convertible Prefer_3

Redeemable Convertible Preferred Stock - Additional Information (Details)	1 Months Ended						6 Months Ended	9 Months Ended
	Apr. 30, 2024 USD ($) $ / shares shares	Mar. 31, 2024 USD ($) Director $ / shares	Jun. 30, 2023 $ / shares shares	Feb. 28, 2023 USD ($) $ / shares shares	Oct. 31, 2022 $ / shares shares	Oct. 31, 2021 USD ($) $ / shares shares	Jun. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2024 USD ($) Director $ / shares shares	Dec. 31, 2023 $ / shares shares
Conversion of Stock [Line Items]
Redeemable convertible preferred stock, shares authorized								31,764,693	31,764,693
Convertible preferred stock converted to common stock								33,321,149	24,065,280
Underwriting discounts and commissions | $								$ 1,793,000
Preferred stock, dividend rate per annum			5%					5%
Percentage of accruing dividend			15%					15%
Conversion terms for preferred stock								Each share of Preferred Stock is convertible at the option of the holder and at any time into common stock as determined by dividing the Preferred Stock Original Issue Price by the Preferred Stock Conversion Price.
Sale of shares of common stock to public at price per share | $ / shares								$ 21.07
Gross proceeds | $								$ 100,000,000
Number of preferred stock converted to Common stock								1
Percentage of original issue price plus accrued return			5%
Percentage of accrued return shall not exceed original issue price			15%
Series A Preferred Stock [Member]
Conversion of Stock [Line Items]
Preferred stock, par value | $ / shares				$ 10
Sale of stock, number of shares issued				8,000,000
Number of board of directors entitled to elect | Director								4
Original issue price per share | $ / shares								$ 10
Series B Preferred Stock [Member]
Conversion of Stock [Line Items]
Preferred stock, par value | $ / shares	$ 17		$ 13				$ 13		$ 15.86
Sale of stock, number of shares issued	8,823,523
Number of directors approval by stock holders | Director		1
Number of board of directors entitled to elect | Director								2
Original issue price per share | $ / shares								$ 17
Redeemable Convertible Preferred Stock
Conversion of Stock [Line Items]
Redeemable convertible preferred stock, shares authorized								31,764,693	31,764,693
Redeemable convertible preferred stock, par value | $ / shares								$ 0.001
Preferred stock, par value | $ / shares									$ 0.001
Redeemable Convertible Preferred Stock | Interim Second Closing
Conversion of Stock [Line Items]
Gross cash proceeds | $						$ 10,000,000
Series A Redeemable Convertible Preferred Stock
Conversion of Stock [Line Items]
Redeemable convertible preferred stock, shares authorized								20,000,000	20,000,000
Convertible preferred stock converted to common stock								20,980,000	20,980,000
Sale of stock, number of shares issued						11,000,000
Sale of stock, price per share | $ / shares						$ 10
Series A Redeemable Convertible Preferred Stock | Interim Second Closing
Conversion of Stock [Line Items]
Sale of stock, price per share | $ / shares						$ 10
Series A Redeemable Convertible Preferred Stock | Maximum | Interim Second Closing
Conversion of Stock [Line Items]
Sale of stock, number of shares issued						1,000,000
Series A Redeemable Convertible Preferred Stock | Milestone Shares
Conversion of Stock [Line Items]
Sale of stock, number of shares issued				8,000,000		9,000,000
Sale of stock, price per share | $ / shares				$ 10		$ 10
Fair value of convertible preferred stock | $				$ 80,300,000
Gross cash proceeds | $				80,000,000
Preferred stock tranche right liability settled | $				$ 300,000
Series A Redeemable Convertible Preferred Stock | Milestone Shares | Interim Second Closing
Conversion of Stock [Line Items]
Sale of stock, number of shares issued					1,000,000
Sale of stock, price per share | $ / shares					$ 10
Series B Redeemable Convertible Preferred Stock
Conversion of Stock [Line Items]
Redeemable convertible preferred stock, shares authorized								11,764,693	11,764,693
Convertible preferred stock converted to common stock								12,341,149	3,085,280
Sale of stock, number of shares issued	8,823,523						2,941,170
Sale of stock, price per share | $ / shares	$ 17	$ 17	$ 17				$ 17
Convertible preferred stock approval by number of directors | Director		6
Fair value of convertible preferred stock | $	$ 150,000,000
Gross cash proceeds | $	150,000,000	$ 50,000,000					$ 50,000,000
Underwriting discounts and commissions | $							600,000
Preferred stock tranche right liability settled | $		$ 11,800,000					$ 100,000
Series B Redeemable Convertible Preferred Stock | Maximum
Conversion of Stock [Line Items]
Sale of stock, number of shares issued			11,764,693
Underwriting discounts and commissions | $	100,000
Preferred stock tranche right liability settled | $	$ 100,000
Series B Redeemable Convertible Preferred Stock | Milestone Shares
Conversion of Stock [Line Items]
Sale of stock, number of shares issued							8,823,523

Redeemable Convertible Prefer_4

Redeemable Convertible Preferred Stock - Schedule of Preferred Stock (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Conversion of Stock [Line Items]
Preferred Stock Authorized	31,764,693	31,764,693
Preferred Stock Issued	31,764,693	22,941,170
Preferred Stock Outstanding	31,764,693	22,941,170
Carrying Value	$ 380,874	$ 230,935
Liquidation Preference	$ 430,759	$ 267,718
Common Stock Issuable Upon Conversion	33,321,149	24,065,280
Series A Redeemable Convertible Preferred Stock
Conversion of Stock [Line Items]
Preferred Stock Authorized	20,000,000	20,000,000
Preferred Stock Issued	20,000,000	20,000,000
Preferred Stock Outstanding	20,000,000	20,000,000
Carrying Value	$ 193,143	$ 193,143
Liquidation Preference	$ 223,800	$ 216,293
Common Stock Issuable Upon Conversion	20,980,000	20,980,000
Series B Redeemable Convertible Preferred Stock
Conversion of Stock [Line Items]
Preferred Stock Authorized	11,764,693	11,764,693
Preferred Stock Issued	11,764,693	2,941,170
Preferred Stock Outstanding	11,764,693	2,941,170
Carrying Value	$ 187,731	$ 37,792
Liquidation Preference	$ 206,959	$ 51,425
Common Stock Issuable Upon Conversion	12,341,149	3,085,280

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - USD ($)	1 Months Ended	9 Months Ended	12 Months Ended
	Oct. 31, 2024	Sep. 30, 2024	Dec. 31, 2023	Oct. 15, 2024	Oct. 04, 2024
Class of Stock [Line Items]
Dividends declared		$ 0	$ 0
Common stock, shares authorized		40,684,346	40,664,346
Common stock, par value		$ 0.001	$ 0.001
Common stock, shares issued		3,025,452	2,992,479
Common stock, shares outstanding		3,025,452	2,992,479
Shares of common stock reserved for issuance		39,614,500	38,051,952
Offering costs		$ 1,793,000
Subsequent Events
Class of Stock [Line Items]
Common stock, shares authorized					500,000,000
IPO | Subsequent Events
Class of Stock [Line Items]
Common stock, shares authorized				500,000,000
Number of shares issued and sold (in shares)	17,250,000
Net proceeds from issuance of initial public offering	$ 268,700,000
Underwriting discounts and commissions	20,500,000
Offering costs	$ 4,000,000
Over Allotment Option | Subsequent Events
Class of Stock [Line Items]
Number of shares issued and sold (in shares)	2,250,000
Issued price per share	$ 17

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended			9 Months Ended
	Aug. 19, 2024	Apr. 30, 2024	Mar. 31, 2024	Feb. 29, 2024	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock reserved for future issuance					39,614,500		38,051,952
Stock options, granted					3,209,120
Weighted-average grant-date fair value of options granted					$ 4.36	$ 3.08
Unrecognized compensation cost related to unvested stock options					$ 14.1
Incremental stock-based compensation					$ 0.7
2021 Stock Option and Grant Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock reserved for future issuance					6,360,626		4,765,105
Number of remaining shares available for future grants					55,379		564,696
2024 Stock Option and Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock reserved for future issuance	3,180,000
Increase in percentage of outstanding number of common stock					5%
2024 Employee Stock Purchase Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock reserved for future issuance	488,467
Increase in number of shares available for issuance	976,934
Increase in percentage of outstanding number of common stock					1%
Stock Options to Purchase Common Stock
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Weighted average period in years of recognition for unvested stock options					3 years 2 months 12 days
Performance-based Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock options, granted					1,206,249
Minimum | 2021 Stock Option and Grant Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Increase in number of shares available for issuance		4,765,105
Maximum | 2021 Stock Option and Grant Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Increase in number of shares available for issuance		6,360,626
Chief Operating Officer
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of shares held				142,935
Exercisable, termination term				1 year
Chief Executive Officer
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of shares held			532,553
Stock options vested			38,245
Exercisable, termination term			2 years

Stock-based Compensation - Sche

Stock-based Compensation - Schedule of Assumptions Used in Black-Scholes Option-pricing Model to Determine the Fair Value of Stock Options Granted (Details) - $ / shares	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Per share fair value of common stock	$ 6.19	$ 4.52
Expected volatility	78%	77%
Expected dividends	0%	0%
Expected term (in years)	6 years 3 months 18 days	6 years 3 months 18 days
Risk-free rate	3.35%	1.94%

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Number of Options, Outstanding as of December 31, 2023	4,166,107
Number of Options, Granted	3,209,120
Number of Options, Exercised	(32,973)
Number of Options, Forfeited or expired	(1,104,280)
Number of Options, Outstanding as of September 30, 2024	6,237,974	4,166,107
Number of Options, Options exercisable September 30, 2024	1,861,312
Number of Options, Vested and expected to vest September 30, 2024	6,237,974
Weighted Average Exercise Price, Outstanding as of December 31, 2023	$ 3.75
Weighted Average Exercise Price, Granted	6.19
Weighted Average Exercise Price, Exercised	3.99
Weighted Average Exercise Price, Forfeited or expired	3.82
Weighted Average Exercise Price, Outstanding as of September 30, 2024	4.99	$ 3.75
Weighted Average Exercise Price, Options exercisable September 30, 2024	3.62
Weighted Average Exercise Price, Vested and expected to vest September 30, 2024	$ 4.99
Weighted-Average Remaining Contractual Term, Outstanding	8 years	8 years 6 months
Weighted-Average Remaining Contractual Term, Options exercisable September 30, 2024	5 years 4 months 24 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest September 30, 2024	8 years
Intrinsic Value, Outstanding	$ 35,091	$ 4,648
Intrinsic Value, Options exercisable September 30, 2024	13,028
Intrinsic Value, Vested and expected to vest September 30, 2024	$ 35,091

Stock-based compensation - Sc_2

Stock-based compensation - Schedule of Classification of Stock-based Compensation in Condensed Consolidated Statements of Operations and Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	$ 1,863	$ 683	$ 3,918	$ 2,614
General and Administrative
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	1,553	421	3,082	1,801
Research and Development
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	$ 310	$ 262	$ 836	$ 813

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Effective federal tax rate	0%	0%
Effective state tax rate	0%	0%
Income tax expense or benefit	$ 0	$ 0

Net Loss per Share - Summary of

Net Loss per Share - Summary of Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Numerator:
Net loss	$ (15,992)	$ (14,678)	$ (10,894)	$ (3,102)	$ (2,540)	$ (3,062)	$ (41,564)	$ (8,704)
Preferred stock cumulative dividends	(5,041)			(3,151)			(13,041)	(14,567)
Net loss attributable to common stockholders	$ (21,033)			$ (6,253)			$ (54,605)	$ (23,271)
Denominator:
Weighted-average common shares outstanding, basic	3,023,155			2,958,727			3,009,234	2,944,804
Weighted-average common shares outstanding, diluted	3,023,155			2,958,727			3,009,234	2,944,804
Net loss per share attributable to common stockholders, basic	$ (6.96)			$ (2.11)			$ (18.15)	$ (7.9)
Net loss per share attributable to common stockholders, diluted	$ (6.96)			$ (2.11)			$ (18.15)	$ (7.9)

Net Loss per Share - Schedule o

Net Loss per Share - Schedule of Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive securities excluded from calculation of diluted net loss per share	39,559,123	28,253,898
Preferred stock converted to common stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive securities excluded from calculation of diluted net loss per share	33,321,149	24,065,280
Stock Options to Purchase Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive securities excluded from calculation of diluted net loss per share	6,237,974	4,188,618

Net Loss per Share - Schedule_2

Net Loss per Share - Schedule of Dilutive Securities Excluded from Calculation of Diluted Net Loss per Share (Parenthetical) (Details) - shares	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive securities excluded from calculation of diluted net loss per share	39,559,123	28,253,898
Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Preferred stock shares converted to common stock		9,255,869
Series B Preferred Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive securities excluded from calculation of diluted net loss per share		8,823,523

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)	Sep. 30, 2024	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Liabilities recorded for loss contingencies	$ 0	$ 0

License Agreements - Additional

License Agreements - Additional Information (Details) - Lonza License Agreement - USD ($)	1 Months Ended	9 Months Ended
	Oct. 31, 2021	Sep. 30, 2024	Sep. 30, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalty payment term upon first commercial sale	10 years
License agreement, royalty payments		$ 0	$ 0
License agreement, annual payment		$ 500,000	$ 400,000

Revenue - Additional Informatio

Revenue - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2021	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
License agreement, revenue recognized		$ 607,000	$ 621,000	$ 1,757,000	$ 1,930,000
Maruho Agreement
Disaggregation of Revenue [Line Items]
License agreement, termination written notice period	60 days
Prepayment for research and development services				0	2,400,000
License agreement, revenue recognized					1,800,000
License agreement, deferred revenue		$ 0	$ 600,000	$ 0	$ 600,000	$ 0

Related Parties - Additional In

Related Parties - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 28, 2023	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Related Party Transaction [Line Items]
Collaboration revenue - related party		$ 607	$ 621	$ 1,757	$ 1,930
Related party accounts receivable		$ 607		$ 607		$ 98
Preferred stock, shares issued		31,764,693		31,764,693		22,941,170
Maruho | Series A Preferred Stock
Related Party Transaction [Line Items]
Preferred stock, shares issued	1,000,000
Gross proceeds from issuance of preferred stock	$ 10,000
Maruho | Maruho Agreement
Related Party Transaction [Line Items]
Cost reimbursements received				$ 1,200	2,700
Collaboration revenue - related party		$ 600	600	1,800	1,900
Related party accounts receivable		$ 600	$ 300	$ 600	$ 300

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) $ / shares in Units, $ in Millions		1 Months Ended
	Oct. 04, 2024 USD ($) shares	Oct. 31, 2024 USD ($) $ / shares shares	Oct. 15, 2024 shares	Sep. 30, 2024 $ / shares shares	Dec. 31, 2023 shares	Sep. 30, 2023 $ / shares
Subsequent Event [Line Items]
Common stock, shares authorized				40,684,346	40,664,346
Convertible preferred stock, shares outstanding				31,764,693	22,941,170
Stock issued upon conversion				1
Share price | $ / shares				$ 6.19		$ 4.52
Subsequent Events
Subsequent Event [Line Items]
Stock split ratio	1.049
Common stock, shares authorized	500,000,000
Reclassification of convertible preferred stock | $	$ 380.9
Subsequent Events | Common Stock
Subsequent Event [Line Items]
Stock issued upon conversion	33,321,149
Subsequent Events | Convertible Preferred Stock
Subsequent Event [Line Items]
Convertible preferred stock, shares outstanding	31,764,693
Subsequent Events | IPO
Subsequent Event [Line Items]
Common stock, shares authorized			500,000,000
Sale of stock, number of shares issued		17,250,000
Share price | $ / shares		$ 17
Net proceeds from issuance of initial public offering | $		$ 268.7
Underwriting discounts and commissions | $		20.5
Other offering costs | $		$ 4
Subsequent Events | Over Allotment Option
Subsequent Event [Line Items]
Sale of stock, number of shares issued		2,250,000