Alto Neuroscience (ANRO) 10-Q 12 Nov 24 2024 Q3 Quarterly report Financial data

Cover

Cover - shares	9 Months Ended
	Sep. 30, 2024	Nov. 08, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2024
Document Transition Report	false
Entity File Number	001-41944
Entity Registrant Name	Alto Neuroscience, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	83-4210124
Entity Address, Address Line One	650 Castro Street, Suite 450
Entity Address, City or Town	Mountain View
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94041
City Area Code	650
Local Phone Number	200-0412
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	ANRO
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		26,970,168
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001999480
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Amendment Flag	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 181,701	$ 82,548
Other receivables	0	8
Prepaid expenses and other current assets	1,825	2,835
Total current assets	183,526	85,391
Restricted cash	500	0
Property and equipment, net	2,353	1,106
Operating right-of-use asset	5,225	0
Other assets	4	131
Total assets	191,608	86,628
Current liabilities:
Accounts payable	2,252	1,074
Accrued expenses and other current liabilities	8,234	4,536
Term loan, current	3,529	0
Total current liabilities	14,015	5,610
Term loan, non-current	6,627	9,861
Convertible Grant Agreement	1,298	0
Preferred stock warrant liability	0	1,352
Lease liability, long-term	4,616	0
Total liabilities	26,556	16,823
Commitments and contingencies (Note 12)
Convertible preferred stock	0	141,477
Stockholders’ equity (deficit):
Common stock (par value $0.0001), 500,000 and 52,000 shares authorized; 26,968 and 3,832 shares issued and outstanding as of September 30, 2024 and December 31, 2023	3	0
Additional paid-in capital	288,339	5,372
Accumulated deficit	(123,195)	(76,965)
Accumulated other comprehensive loss	(95)	(79)
Total stockholders’ equity (deficit)	165,052	(71,672)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 191,608	$ 86,628

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2024	Feb. 06, 2024	Dec. 31, 2023	Sep. 30, 2023
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.0001		$ 0.0001	$ 0.0001
Common stock, authorized (in shares)	500,000,000	500,000,000	52,000,000
Common stock, issued (in shares)	26,968,198		3,832,134
Common stock, outstanding (in shares)	26,968,198		3,832,134

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
Operating expenses:
Research and development	$ 13,060	$ 7,967	$ 36,196	$ 20,648
General and administrative	5,826	1,751	15,417	5,396
Total operating expenses	18,886	9,718	51,613	26,044
Loss from operations	(18,886)	(9,718)	(51,613)	(26,044)
Other income (expense):
Interest income	2,500	714	6,716	1,611
Interest expense	(349)	(363)	(1,042)	(1,014)
Change in fair value of warrant liability	0	226	(243)	359
Change in fair value of Convertible Grant Agreement	(48)	0	(48)	0
Total other income (expense), net	2,103	577	5,383	956
Net loss	(16,783)	(9,141)	(46,230)	(25,088)
Other comprehensive loss
Foreign currency translation	(6)	(10)	(16)	(40)
Total other comprehensive loss	(6)	(10)	(16)	(40)
Comprehensive loss	$ (16,789)	$ (9,151)	$ (46,246)	$ (25,128)
Net loss per share attributable to common stockholders, basic (in dollars per share)	$ (0.62)	$ (2.44)	$ (1.94)	$ (6.75)
Net loss per share attributable to common stockholders, diluted (in dollars per share)	$ (0.62)	$ (2.44)	$ (1.94)	$ (6.75)
Weighted-average number of common shares outstanding, basic (in shares)	26,959,000	3,742,000	23,878,000	3,717,000
Weighted-average number of common shares outstanding, diluted (in shares)	26,959,000	3,742,000	23,878,000	3,717,000

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ (38,406)	$ 0	$ 2,300	$ (40,660)	$ (46)
Preferred stock, beginning balance (in shares) at Dec. 31, 2022	16,204,000
Preferred stock, beginning balance at Dec. 31, 2022	$ 72,235
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Series B preferred stock, net of issuance costs (in shares)	4,167,000
Issuance of Series B preferred stock, net of issuance costs	$ 24,846
Preferred stock, ending balance (in shares) at Mar. 31, 2023	20,371,000
Preferred stock, ending balance at Mar. 31, 2023	$ 97,081
Beginning balance (in shares) at Dec. 31, 2022		3,764,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation	(19)				(19)
Stock compensation expense	484		484
Net loss	(7,284)			(7,284)
Ending balance (in shares) at Mar. 31, 2023		3,764,000
Ending balance at Mar. 31, 2023	$ (45,225)	$ 0	2,784	(47,944)	(65)
Preferred stock, beginning balance (in shares) at Dec. 31, 2022	16,204,000
Preferred stock, beginning balance at Dec. 31, 2022	$ 72,235
Preferred stock, ending balance (in shares) at Sep. 30, 2023	20,371,000
Preferred stock, ending balance at Sep. 30, 2023	$ 97,081
Beginning balance (in shares) at Dec. 31, 2022		3,764,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation	(40)
Net loss	(25,088)
Ending balance (in shares) at Sep. 30, 2023		3,797,000
Ending balance at Sep. 30, 2023	(61,097)	$ 0	4,737	(65,748)	(86)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ (45,225)	$ 0	2,784	(47,944)	(65)
Preferred stock, beginning balance (in shares) at Mar. 31, 2023	20,371,000
Preferred stock, beginning balance at Mar. 31, 2023	$ 97,081
Preferred stock, ending balance (in shares) at Jun. 30, 2023	20,371,000
Preferred stock, ending balance at Jun. 30, 2023	$ 97,081
Beginning balance (in shares) at Mar. 31, 2023		3,764,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		10,000
Exercise of common stock options	43		43
Foreign currency translation	(11)				(11)
Stock compensation expense	1,260		1,260
Net loss	(8,663)			(8,663)
Ending balance (in shares) at Jun. 30, 2023		3,774,000
Ending balance at Jun. 30, 2023	(52,596)	$ 0	4,087	(56,607)	(76)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ (52,596)	$ 0	4,087	(56,607)	(76)
Preferred stock, ending balance (in shares) at Sep. 30, 2023	20,371,000
Preferred stock, ending balance at Sep. 30, 2023	$ 97,081
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		23,000
Exercise of common stock options	109		109
Foreign currency translation	(10)				(10)
Stock compensation expense	541		541
Net loss	(9,141)			(9,141)
Ending balance (in shares) at Sep. 30, 2023		3,797,000
Ending balance at Sep. 30, 2023	(61,097)	$ 0	4,737	(65,748)	(86)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(61,097)	0	4,737	(65,748)	(86)
Beginning balance	$ (71,672)	$ 0	5,372	(76,965)	(79)
Preferred stock, beginning balance (in shares) at Dec. 31, 2023	29,919,000
Preferred stock, beginning balance at Dec. 31, 2023	$ 141,477
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of common stock for conversion of preferred stock (in shares)	(29,919,000)
Issuance of common stock for conversion of preferred stock	$ (141,477)
Preferred stock, ending balance (in shares) at Mar. 31, 2024	0
Preferred stock, ending balance at Mar. 31, 2024	$ 0
Beginning balance (in shares) at Dec. 31, 2023	3,832,134	3,832,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		69,000
Exercise of common stock options	$ 10		10
Issuance of common stock for conversion of preferred stock (in shares)		13,664,000
Issuance of common stock for conversion of preferred stock	141,477	$ 2	141,475
Foreign currency translation	(5)				(5)
Stock compensation expense	2,179		2,179
Exercise of warrant (in shares)		73,000
Initial public offering of common stock, net of offering cost of $4,653 (in shares)		9,246,000
Initial public offering of common stock, net of offering cost of $4,643	132,937	$ 1	132,936
Reclassification of warrant to equity	1,595		1,595
Net loss	(13,417)			(13,417)
Ending balance (in shares) at Mar. 31, 2024		26,884,000
Ending balance at Mar. 31, 2024	$ 193,104	$ 3	283,567	(90,382)	(84)
Preferred stock, beginning balance (in shares) at Dec. 31, 2023	29,919,000
Preferred stock, beginning balance at Dec. 31, 2023	$ 141,477
Preferred stock, ending balance (in shares) at Sep. 30, 2024	0
Preferred stock, ending balance at Sep. 30, 2024	$ 0
Beginning balance (in shares) at Dec. 31, 2023	3,832,134	3,832,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation	$ (16)
Net loss	$ (46,230)
Ending balance (in shares) at Sep. 30, 2024	26,968,198	26,968,000
Ending balance at Sep. 30, 2024	$ 165,052	$ 3	288,339	(123,195)	(95)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 193,104	$ 3	283,567	(90,382)	(84)
Preferred stock, beginning balance (in shares) at Mar. 31, 2024	0
Preferred stock, beginning balance at Mar. 31, 2024	$ 0
Preferred stock, ending balance (in shares) at Jun. 30, 2024	0
Preferred stock, ending balance at Jun. 30, 2024	$ 0
Beginning balance (in shares) at Mar. 31, 2024		26,884,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		20,000
Exercise of common stock options	61		61
Issuance of common stock for MedRx Agreement (in shares)		47,000
Issuance of common stock for MedRx Agreement	735		735
Foreign currency translation	(5)				(5)
Stock compensation expense	1,888		1,888
Settlement of initial public offering cost	23		23
Net loss	(16,030)			(16,030)
Ending balance (in shares) at Jun. 30, 2024		26,951,000
Ending balance at Jun. 30, 2024	179,776	$ 3	286,274	(106,412)	(89)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 179,776	$ 3	286,274	(106,412)	(89)
Preferred stock, ending balance (in shares) at Sep. 30, 2024	0
Preferred stock, ending balance at Sep. 30, 2024	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		17,000
Exercise of common stock options	67		67
Foreign currency translation	(6)				(6)
Stock compensation expense	1,998		1,998
Net loss	$ (16,783)			(16,783)
Ending balance (in shares) at Sep. 30, 2024	26,968,198	26,968,000
Ending balance at Sep. 30, 2024	$ 165,052	$ 3	288,339	(123,195)	(95)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 165,052	$ 3	$ 288,339	$ (123,195)	$ (95)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Series B Preferred
Payments on issuance costs	$ 4,643	$ 154

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Net loss	$ (46,230)	$ (25,088)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	332	261
Loss on disposal of assets	22	20
Stock compensation expense	6,065	2,285
Change in fair value of preferred stock warrant liability	243	(359)
Non-cash lease expense	126	209
Non-cash interest expense related to term loan	295	290
Non-cash research and development license expense	735	0
Change in fair value of Convertible Grant Agreement	48	0
Changes in operating assets and liabilities:
Other receivables	8	325
Prepaid expenses and other assets	(921)	(159)
Accounts payable	1,278	149
Accrued liabilities and other liabilities	3,596	143
Net cash used in operating activities	(34,403)	(21,924)
Cash Flows from Investing Activities:
Capital expenditures	(1,569)	(118)
Net cash used in investing activities	(1,569)	(118)
Cash Flows from Financing Activities:
Proceeds from exercise of stock options	138	152
Issuance of convertible preferred stock	0	25,000
Proceeds from issuance of common stock from initial public offering	137,579	0
Proceeds from Convertible Grant Agreement	1,250	0
Net cash provided by financing activities	135,642	24,998
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(17)	(12)
Net increase in cash, cash equivalents and restricted cash	99,653	2,944
Cash, cash equivalents and restricted cash at the beginning of the period	82,548	48,344
Cash, cash equivalents and restricted cash at the end of the period	182,201	51,288
Supplemental Disclosure of Non-cash Activities
Purchase of property and equipment not yet paid	32	0
Deferred offering and share issue costs not yet paid	0	60
Conversion of preferred stock into common stock upon completion of initial public offering	141,477	0
Reclassification of preferred warrant liability to equity	1,595	0
Reclassification of deferred offering costs to equity	1,393	0
Operating right-of-use asset obtained in exchange for lease obligation	5,246	0
Supplemental Disclosure of Cash Flow Information
Cash paid for interest	751	665
Series B Preferred Stock Financing
Cash Flows from Financing Activities:
Payments on issuance costs	0	(154)
IPO
Cash Flows from Financing Activities:
Payments on issuance costs	(3,225)	0
Series C Preferred Stock Financing
Cash Flows from Financing Activities:
Payments on issuance costs	$ (100)	$ 0

Description of the Business

Description of the Business	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of the Business	Description of the Business Alto Neuroscience, Inc. (the “Company” or “Alto”) was incorporated in Delaware on March 25, 2019. The Company maintains its headquarters in Mountain View, California. The Company has one wholly-owned subsidiary in Australia that was formed during 2020 to conduct clinical trials. Alto is a clinical stage biopharmaceutical company with a mission to redefine psychiatry by leveraging individuals’ neurobiology to develop personalized and highly effective treatment options. Through insights derived from the Company’s scalable and proprietary Precision Psychiatry Platform, which applies rigorous data science and robust analytics to data gathered by neurocognitive assessments, electroencephalography, and wearable devices, the Company aims to discover brain-based biomarkers to better identify which patients are more likely to respond to its novel product candidates. The Company’s current pipeline consists of five clinical-stage assets initially targeting major depressive disorder, bipolar depression, schizophrenia, and post-traumatic stress disorder populations as identified by independent brain-based biomarkers. Reverse Stock Split In January 2024, the Company’s Board of Directors (the “Board”) approved a 1 for 2.2241 reverse stock split of the Company’s issued and outstanding shares of common stock and options to purchase common stock under its 2019 Equity Incentive Plan. The reverse stock split reduced the number of shares of the Company’s issued and outstanding common stock, as well as the numbers of shares reserved and available for future issuance and underlying outstanding options to purchase common stock under its 2019 Equity Incentive Plan, on a 1 for 2.2241 basis, and resulted in an adjustment to the respective conversion ratios for the Company’s Series Seed convertible preferred stock, Series A convertible preferred stock, Series B convertible preferred stock, and Series C convertible preferred stock to account for the reverse stock split on any conversion of such series of convertible preferred stock into common stock. As such, all references to Series Seed convertible preferred stock, Series A convertible preferred stock, Series B convertible preferred stock, and Series C convertible preferred stock conversion ratios, conversion share and per share amounts, and post-conversion share and per share amounts, as well as common stock option, option per common share, common share and common per share amounts, in these condensed consolidated financial statements and accompanying notes have been retroactively restated to reflect the reverse stock split and the reverse stock split’s effect on the respective Series Seed convertible preferred stock, Series A convertible preferred stock, Series B convertible preferred stock, and Series C convertible preferred stock conversion ratios for each series of convertible preferred stock. The reverse stock split did not affect the par values per share. Forward Stock Split In January 2023, the Board approved a 1.1156 for 1 forward stock split of the Company’s issued and outstanding shares of Series B Preferred Stock, and a proportional adjustment to the existing conversion ratio, as well as the exercise price of the outstanding K2 Warrant. Accordingly, all Series B share and per share amounts for all periods presented in these interim condensed consolidated financial statements have been adjusted retroactively, where applicable, to reflect this stock split and adjustment of the preferred stock conversion ratio. The Co mpany completed an Initial Public Offering (“IPO”) in February 2024 which resulted in the conversion of outstanding preferred stock to common stock (see Note 10). Initial Public Offering On February 6, 2024, the Company completed its IPO of its common stock pursuant to which the Company issued and sold 9,246,000 shares of common stock at a price to the public of $16.00 per share, which includes the exercise in full by the underwriters of their option to purchase 1,206,000 additional shares. The aggregate net proceeds from the IPO, inclusive of proceeds from the over-allotment exercise, were approximately $133.0 million after deducting underwriting discounts and commissions of $10.4 million and offering expenses of $4.6 million. Upon completion of the IPO, all outstanding shares of Series Seed, Series A, Series B and Series C convertible preferred stock converted to common stock. In addition, the IPO also resulted in the net exercise of the Series A Preferred Stock Warrants for an aggregate of 72,631 shares of common stock. Liquidity and Capital Resources The Company has incurred significant operating losses since inception and has relied upon equity financings to fund its operations. At September 30, 2024, the Company had an accumulated deficit of approximately $123.2 million. As the Company continues to incur losses, its transition to profitability will depend on the successful development, approval and commercialization of product candidates and on the generation of sufficient revenues to support its cost structure. No assurance can be provided that the Company will ever be profitable, and unless or until it becomes profitable, the Company will need to continue to raise additional capital.

Summary of Significant Accounti

Summary of Significant Accounting Policies and Basis of Presentation	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies and Basis of Presentation	Summary of Significant Accounting Policies and Basis of Presentation Basis of Presentation The accompanying interim condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) as determined by the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”), and include the accounts of Alto and its wholly-owned subsidiary. All intercompany transactions and balances have been eliminated in consolidation. The interim condensed consolidated financial statements are unaudited and have been prepared on the same basis as the audited annual financial st atements and, in management’s opinion, include all adjustments consisting of only normal recurring adjustments necessary for the fair statement of the Company’s financial position as of September 30, 2024 and its results of operations and statements of equity for the three and nine months ended September 30, 2024 and 2023 and cash flows for the nine months ended September 30, 2024 and 2023. The results o f operations for the three and nine months ended September 30, 2024 are not necessarily indicative of the results to be expected for the full fiscal year or any other period. Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. These interim condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements and the related notes thereto for the year ended December 31, 2023 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission on March 21, 2024. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results may differ materially from those estimates. The most significant estimates and assumptions in the Company’s condensed consolidated financial statements relate to the determination of the fair value of its common stock (as an input for calculating stock-based compensation), estimating accrued or prepaid research and development expenses, and the valuation of the preferred stock warrant liability. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. To the extent there are material differences between the estimates and actual results, the Company’s future results of operations will be affected. Significant Accounting Policies The Company’s significant accounting policies used in the preparation of these condensed consolidated financial statements for the three and nine months ended September 30, 2024 are consistent with those discussed in Note 3 to the consolidated financial statements in the Company's Annual Report on Form 10-K for the year ended December 31, 2023. Recently Issued Accounting Pronouncements In December 2023, the FASB issued Accounting Standards Update (“ASU”) No. 2023-09, Income Taxes (“Topic 740”). The standard requires disaggregation of the effective rate reconciliation into standard categories, enhances disclosure of income taxes paid, and modifies other income tax-related disclosures. The standard will be effective starting in annual periods beginning after December 15, 2024, with early adoption permitted. The Company is currently assessing the impact of adopting this guidance on its condensed consolidated financial statements. In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting - Improving Reportable Segment Disclosures (“Topic 280”). The standard requires disclosures to include significant segment expenses that are regularly provided to the chief operating decision maker (“CODM”), a description of other segment items by reportable segment, and any additional measures of a segment's profit or loss used by the CODM when deciding how to allocate resources. The ASU also requires all annual disclosures currently required by Topic 280 to be included in interim periods. The standard is effective starting in annual periods beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024 with early adoption permitted and requires retrospective application to all prior periods presented in the financial statements. The Company is currently assessing the impact of adopting this guidance on its condensed consolidated financial statements.

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Components	Balance Sheet Components Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following (in thousands): September 30, December 31, Prepayments $ 853 $ 522 Other current assets 277 104 Deferred offering costs — 2,209 Prepaid insurance 695 — Total prepaid expenses and other current assets $ 1,825 $ 2,835 Property and Equipment, Net Property and equipment, net are as follows (in thousands): September 30, December 31, Office equipment and furniture $ 284 $ 70 Computer software and equipment 421 519 Laboratory equipment 2,306 1,201 Construction in progress 251 — Less : accumulated depreciation (909) (684) Property and equipment, net $ 2,353 $ 1,106 During the three and nine months ended September 30, 2024, the Company recorded depreciation and amortization expense of $0.2 million and $0.3 million, respectively . During the three and nine months ended September 30, 2023, the Company recorded depreciation and amortization expense of $0.1 million and $0.3 million, respectively. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consist of the following (in thousands): September 30, December 31, Accrued payroll, vacation and employee-related expenses $ 3,879 $ 518 Accrued research 2,683 2,328 Accrued offering and share issue cost — 916 Accrued license fees 19 50 Accrued interest, short term 81 84 Other accruals and current liabilities 856 515 Lease liability, short term 716 125 Total accrued expenses and other current liabilities $ 8,234 $ 4,536

Debt

Debt	9 Months Ended
	Sep. 30, 2024
Debt Disclosure [Abstract]
Debt	Debt K2 HealthVentures LLC Loan Agreement On December 16, 2022, the Company entered into a Loan and Security Agreement (the “Loan Agreement”) with K2 HealthVentures LLC as a lender, and other lenders (collectively, “Lender”), K2 HealthVentures LLC, as administrative agent for Lender (“Administrative Agent”), and Ankura Trust Company, LLC, as collateral agent for Lender. The Lender has agreed to make available to the Company term loans in an aggregate principal amount of up to $35.0 million under the Loan Agreement. The Company plans to use the proceeds of the term loans to support clinical development as well as for working capital and general corporate purposes. The Loan Agreement provides a term loan commitment of $35.0 million in four potential tranches: (i) a $10.0 million term loan facility funded on December 16, 2022 (the “First Tranche Term Loan”), (ii) a $7.5 million term loan facility (the “Second Tranche Term Loan”) available at the Company’s request between October 1, 2023 and March 1, 2024 subject to either positive data from the Company’s Phase 2b randomized controlled study of ALTO-100 or positive data from the Company’s Phase 2b randomized controlled study of ALTO-300, in each case as determined by the Administrative Agent in its sole discretion, (iii) a $7.5 million term loan facility (the “Third Tranche Term Loan”) available at the Company’s request between October 1, 2023 and March 1, 2024 subject to positive data from the Company’s Phase 2b randomized controlled study of ALTO-100 and positive data from the Company’s Phase 2b randomized controlled study of ALTO-300, in each case as determined by the Administrative Agent in its sole discretion, and (iv) a $10.0 million term loan facility (the “Fourth Tranche Term Loan”) available through January 1, 2025 at both the Lender’s and the Company’s option, subject to the Lender’s review of the Company’s financial and clinical information and operating plans and approval of the Lender’s investment committee. All four of these term loans have a maturity date of December 1, 2026. Based upon the terms of the Loan Agreement, the Company could potentially access up to $10.0 million of the remaining $25.0 million of the credit facility. Borrowings under all four term loan facilities bear interest at a variable annual rate equal to the greater of (i) 6.70%, and (ii) the Prime Rate plus 1.20%. The Company is permitted to make interest-only payments on the First Tranche Term Loan for the first 24 months following the funding date. The interest-only period can be extended by an additional 12 months, subject to the funding of the Second Tranche Term Loan or the funding of the Third Tranche Term Loan and if the Company has completed equity sales of greater than $75.0 million prior to January 1, 2025, subject to certain conditions. In addition, each term loan funded also accrues a deferred interest amount equal to 1% annually of the outstanding principal, and becomes payable at the end of the 48-month term, or earlier in the instance of a repayment. The term of the combined facility will be 48 months, with repayment in monthly installments commencing at the end of the resulting interest-only period as outlined above through the end of the 48-month term. The Company is obligated to pay a final fee equal to 6.25% of the aggregate amount of the term loans funded (“Exit Fee”) to occur upon the earliest of (i) the maturity date, (ii) the acceleration of the term loans, and (iii) the prepayment of the term loans. The Company has the option to prepay all, but not less than all, of the outstanding principal balance of the term loans under the Loan Agreement. If the Company prepays all of the term loans prior to the maturity date, it will pay the Lender a prepayment penalty fee based on a percentage of the outstanding principal balance, equal to 3% if the payment occurs on or before 24 months after the initial funding date, 2% if the prepayment occurs more than 24 months after, but on or before 36 months after the initial funding date, or 1% if the prepayment occurs more than 36 months after the initial funding date. The Exit Fee of $0.6 million with respect to the First Tranche Term Loan was recorded as debt discount, and is being accreted using the effective interest method over the term of the First Tranche Term Loan within Other income (expense), net in the condensed consolidated statements of operations and comprehensive loss. The Company was also obligated to pay the Lender a one-time facility fee of approximately $0.2 million on the initial closing date and will be obligated to pay a 0.7% fee on the amount of the Fourth Tranche Term Loan if and when funded.  The Lender may, at its option, elect to convert any portion of no more than $4.0 million of the then outstanding term loan amount and all accrued and unpaid interest thereon into shares of the Company’s common stock at the Lender’s election, at a conversion price of $10.49 per share. The Company’s obligations under the Loan Agreement are secured by a first priority security interest in substantially all of its assets (with an exclusion for intellectual property). The Loan Agreement contains customary representations and warranties, and also includes customary events of default, including payment default, breach of covenants, change of control, and material adverse effects. The Loan Agreement restricts certain activities, such as disposing of the Company’s business or certain assets, incurring additional debt or liens or making payments on other debt, making certain investments and declaring dividends, acquiring or merging with another entity, engaging in transactions with affiliates or encumbering intellectual property, among others. There are no financial covenants associated with the Loan Agreement. Upon the occurrence of an event of default, a default interest rate of an additional 5% per annum may be applied to the outstanding loan balances, and the Lender may declare all outstanding obligations immediately due and payable and exercise all of its rights and remedies as set forth in the Loan Agreement and under applicable law. The Company recorded interest expense at a weighted average rate of 10.63% and 10.68% re lated to the Loan Agreement for the three and nine months ended September 30, 2024, respectively. During the three and nine months ended September 30, 2024, the Company recorded interest expense of $0.3 million and $1.0 million, respectively. During the three and nine months ended September 30, 2023, the Company recorded interest expense of $0.4 million and $1.0 million, respectively. Future principal debt payments and Exit Fee of the term loan funded as of September 30, 2024 are as follows (in thousands): 2024 (remainder of year) $ — 2025 4,767 2026 5,233 Total principal payments 10,000 Exit Fee 625 Deferred Interest 184 Total principal payments and Exit Fee 10,809 Less: unamortized Exit Fee (352) Less: unamortized debt discount related to warrants (118) Less: unamortized debt issuance costs, including Facility Fee (183) Term loan, net $ 10,156 Less: Term loan, current portion (3,529) Term loan, non-current $ 6,627 The Wellcome Trust Limited Convertible Grant Agreement In July 2024, the Company entered into a convertible loan agreement, or the Convertible Grant Agreement, with The Wellcome Trust Limited, or Wellcome. The Convertible Grant Agreement provides for an unsecured convertible loan, or the Convertible Loan, from Wellcome of up to approximately $11.7 million, payable to Alto in six tranches, of which up to $2.0 million could be funded upon the execution of the Convertible Grant Agreement and the remainder of which will be funded upon the completion of certain milestones as set forth in the Convertible Grant Agreement. As of September 30, 2024, the Company has drawn down $1.3 million of the $2.0 million execution tranche and will continue to access the loan as needed as the ALTO-100 study in bipolar depression progresses. Interest will accrue at an annual rate equal to the Sterling Overnight Index Rate plus 2%, subject to potential adjustment if such annual interest rate equals or exceeds 9% at any time. Proceeds from the Convertible Loan may be used by the Company solely to advance development of ALTO-100 in bipolar depression. The Convertible Grant Agreement also includes customary covenants, representations and warranties, including with respect to the conduct of the Company’s Phase 2b clinical trial evaluating ALTO-100 in patients with bipolar depression and certain information and audit rights of Wellcome in connection therewith, as well as with respect to the Company’s efforts to develop and exploit ALTO-100. At any time after the second anniversary of the effective date of the Convertible Grant Agreement or in connection with an event of default, Wellcome has the right, at its election, to convert some or all of the Convertible Loan into shares of the Company’s common stock at a price per share equal to a 20% discount to the thirty-day volume-weighted average price of Common Stock on the New York Stock Exchange at the date of such conversion. The Convertible Grant Agreement provides that in no event shall the aggregate number of shares of Common Stock issued pursuant to conversion of the Convertible Loan exceed 5,363,326, which is equal to 19.9% of the number of shares of Common Stock outstanding as of the date of the Convertible Grant Agreement. At any time after the fifth anniversary of the effective date of the Convertible Grant Agreement or in connection with an event of default, Wellcome may require repayment of the Convertible Loan in full, together with accrued interest, to the extent not converted as described above. Future principal debt payments of the Convertible Grant Agreement funded as of September 30, 2024 are as follows (in thousands): 2024 (remainder of year) $ — 2025 — 2026 — 2027 — 2028 — 2029 1,250 Term loan, non-current $ 1,250 The proceeds of the Convertible Grant Agreement are being used to fund the Company’s Phase 2b clinical trial evaluating ALTO-100 in bipolar depression. The Company assessed the terms and features of the Convertible Grant Agreement and determined that the Company was eligible to elect the fair value option under ASC 825, Financial Instruments. The Convertible Grant Agreement contain various embedded features and the election of the fair value option allowed the Company to bypass analysis of potential embedded derivatives and further analysis of bifurcation of any recognized financial liabilities. Under the fair value option, the financial liability is initially measured at its fair value on the issue date and subsequently remeasured at estimated fair value on a recurring basis at each reporting date. Changes in the fair value of the Convertible Grant Agreement, which include accrued interest, if any, are recorded as a component of other income (expense) in the condensed consolidated statements of operations. The Company has not elected to present interest expense separately from changes in fair value and therefore will not present interest expense associated with the Convertible Grant Agreement. Any changes in fair value caused by instrument-specific credit risk are presented separately in other comprehensive income or loss. The Company determined the fair value of the Convertible Grant Agreement using a probability-weighted income approach and recorded the loan at fair value of $1.3 million in the condensed consolidated balance sheet at issuance. The Company calculated the discounted cash flows of the Convertible Grant Agreement using a discount rate of 11.17% and adjusted for the probability of repayment and conversion scenarios. The Company remeasured the fair value of the Convertible Grant Agreement as of September 30, 2024 using a probability-weighted income approach. The Company calculated discounted cash flows of the Convertible Grant Agreement using a discount rate of 10.22% and adjusted for the probability of various repayment scenarios. The following table reconciles the change in fair value of the Convertible Grant Agreement during the three months ended September 30, 2024 (in thousands): Beginning fair value balance, July 2024 $ — Recognition of Convertible Grant Agreement 1,250 Principal payments — Changes in fair value reported in statement of operation 48 Changes in fair value reported in comprehensive loss — Ending fair value balances as of September 30, 2024 $ 1,298

Fair Value

Fair Value	9 Months Ended
	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Fair Value	Fair Value The Company’s financial instruments that are measured at fair value on a recurring basis consist of money market funds and the Convertible Grant Agreement. 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): December 31, 2023 Total Level 1 Level 2 Level 3 Assets: Cash equivalents - money market funds $ 82,548 $ 82,548 $ — $ — Total assets $ 82,548 $ 82,548 $ — $ — Liabilities: Preferred stock warrant liability $ 1,352 $ — $ — $ 1,352 Total liabilities $ 1,352 $ — $ — $ 1,352 September 30, 2024 Total Level 1 Level 2 Level 3 Assets: Cash and cash equivalents: Money market funds $ 181,448 $ 181,448 $ — $ — Restricted cash: Money market funds 500 500 — — Total assets $ 181,948 $ 181,948 $ — $ — Liabilities: Convertible Grant Agreement 1,298 — — 1,298 Total liabilities $ 1,298 $ — $ — $ 1,298

Asset Purchase and License Agre

Asset Purchase and License Agreements	9 Months Ended
	Sep. 30, 2024
Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]
Asset Purchase and License Agreements	Asset Purchase and License Agreements From time to time, the Company enters into asset purchase and license agreements with third parties. As of September 30, 2024 , the Company was a party to the following significant agreements with certain financial commitments: Stanford License Agreement On December 6, 2019, the Company entered into a license agreement with the Board of Trustees of the Leland Stanford Junior University (“Stanford”) covering four inventions to guide treatment of psychiatry patients, some of which are jointly owned by other academic institutions but are exclusively managed by Stanford under certain invention management agreements between Stanford and the other institutions (the “Stanford License Agreement”). The Stanford License Agreement was subsequently amended in May 2020 and December 2023. In connection with the Stanford License Agreement, as amended, the Company obtained an exclusive, worldwide, royalty-bearing license under certain patent rights in five patent families relating to brain stimulation, electroencephalogram and functional MRI that could be used to guide treatment of psychiatry patients (the “Stanford Licensed Patents”), and under certain technology relating to the inventions covered by the Stanford Licensed Patents (the “Stanford Licensed Technology”), to make, have made, use, sell, offer for sale and import licensed products for use in any indication. The Company's rights under the Stanford Licensed Patents are exclusive until December 2029, at which time it will become non-exclusive, and its rights under the Stanford Licensed Technology are non-exclusive. The Company may terminate the Stanford License Agreement at any time upon specified written notice to Stanford. Stanford may also terminate the agreement upon an uncured material breach of the agreement, including failure to achieved defined milestones related to the development and commercialization of the licensed products, as well as for certain other specified breaches. As partial consideration to acquire these license rights, Alto paid a nominal upfront fee and reimbursed Stanford a nominal amount of prior patent prosecution expenses related to the licensed patents. Additionally, Alto is required to pay a low five-digit annual maintenance fee beginning on the first anniversary of the effective date through the term of the agreement. Alto also agreed to issue an aggregate of 71,370 shares of Alto’s common stock, or 1% of Alto’s equity on a fully-diluted basis, to Stanford and the other inventors. These shares were issued in April 2020. As additional consideration, the Company granted Stanford and the other inventors antidilution rights, whereby the Company agreed to maintain this collective equity ownership percentage at 1% until such time as the Company completed its initial qualified financing. In connection with this anti-dilution provision, Alto issued a further 32,978 shares of its common stock to Stanford and the other inventors in 2021. Following the initial closing of the Series A convertible preferred stock agreement, which met the definition of such qualified financing, the anti-dilution feature expired and no additional shares were issued. In further consideration of the rights granted, beginning with the Company’s first commercial sale of the licensed products, the Company will also pay an annual earned royalty in the very low single digits on net sales of licensed products, subject to certain customary reductions. The Company is also required to pay Stanford mid-teen to low-mid double digit percentages of any sublicensing consideration that it receives from third parties to whom the Company sublicenses rights under the Stanford Licensed Patents, depending on the timing of entry into the applicable sublicense. The Company does not have any future milestone payment obligations to Stanford or the other inventors under the Stanford License Agreement other than costs related to maintenance of patents. Sanofi License Agreement Effective May 18, 2021 , the Company entered into an agreement with Sanofi to obtain an exclusive, worldwide, royalty-bearing license, with the right to grant sublicenses, under certain patent rights and know-how of Sanofi relating to a PDE4 inhibitor compound, now known as ALTO-101, to use, develop, manufacture, commercialize or otherwise exploit ALTO-101 and products incorporating ALTO-101 in all human therapeutic, prophylactic and diagnostic uses. The Company also acquired a worldwide non-exclusive license to use certain know-how licensed to Sanofi by a specified third party to exploit the licensed products solely with respect to Parkinson’s disease. In exchange for the rights granted to the Company, the Company made a cash payment of $0.5 million which is recorded in research and development expenses during the year ended December 31, 2021 in the consolidated statements of operations and comprehensive loss since the acquired license does not have an alternative future use. The Company is obligated to pay Sanofi up to an aggregate amount in the low-mid double digit millions upon the completion of a combination of development and regulatory approval milestones. If the Company achieves regulatory approval for one or more licensed products, the Company will owe Sanofi certain commercial milestone payments for the achievement of specified levels of aggregate, annual worldwide net sales of all licensed products, up to an aggregate amount of $102.0 million. In addition, if the Company grants sublicenses under the patents and know how licensed to the Company under the agreement, the Company will be required to pay sublicense revenue to Sanofi at tiered percentages ranging from low-mid double-digit percentages down to the very low double-digit percentages, reducing based on the time of entry into the applicable sublicense agreement. No additional milestones or royalties were paid or accrued during the three or nine months ended September 30, 2024 or 2023 related to this agreement. In further consideration of the rights granted, beginning with the Company’s first commercial sale of the licensed products, the Company will also pay an annual tiered earned royalty ranging from the mid-to-high single digits on net sales of licensed products, subject to certain customary reductions and a customary royalty floor. Royalties are payable, on a licensed products-by-licensed products and a country-by-country basis, until the latest to occur of (a) expiration of the last valid claim of a licensed patent covering such licensed products in such country, (b) the expiration of any regulatory exclusivity for such licensed products in such country, and (c) the 10th anniversary of the first commercial sale of such licensed product in such country. In addition, if the Company uses specified know-how licensed to Sanofi by the specified third party to exploit the licensed products for Parkinson’s disease, the Company will be required pay an additional premium at a mid-single digit percentage on all fees, milestone payments and royalties payable by the Company to Sanofi under the agreement. Unless terminated earlier, the license agreement with Sanofi will expire with respect to each licensed product, on a country-by-country basis, upon the expiration of the royalty term set forth above, and with respect to the agreement in its entirety upon the expiry of the royalty term for the last licensed product for which there has been a first commercial sale. Either the Company or Sanofi may terminate the Sanofi Agreement upon written notice for the uncured material breach of the other party. Sanofi also has the right to terminate the agreement for the Company’s insolvency or if the Company brings or otherwise participates in a patent challenge against any licensed patents. The Company may terminate the agreement for any reason upon specified prior written notice to Sanofi. Cerecor License Agreement Effective May 28, 2021 , the Company entered into an agreement with Cerecor Inc. (n/k/a Avalo Therapeutics, Inc.) (“Cerecor”) to obtain an exclusive, worldwide, royalty-bearing license, with the right to grant sublicenses, under certain patent rights and know-how owned or controlled by Cerecor, relating to an NR2B inhibitor compound now known as ALTO-202, including certain rights licensed to Cerecor by Essex Chemie AG, or Merck, to research, develop, make, have made, use, import, offer for sale and sell ALTO-202 and products incorporating ALTO-202 (“Cerecor Licensed Products”), for the prevention, diagnosis and/or treatment of all diseases in humans. In exchange for the rights granted to the Company, the Company made a cash payment of $0.5 million, which is recorded in research and development expenses during the year ended December 31, 2021 in the consolidated statements of operations and comprehensive loss since the acquired license does not have an alternative future use. The Company is obligated to make aggregate cash payments of up to $59.1 million per Cerecor Licensed Product if the Company achieves certain development, regulatory approval, and first commercial sale milestones for such Cerecor Licensed Product in up to a specified number of indications. If the Company successfully commercializes Cerecor Licensed Products, it will also be required to pay to Merck sales milestones totaling up to $15.0 million for all Cerecor Licensed Products, for the achievement of certain specified levels of worldwide annual aggregate net sales of all Cerecor Licensed Products. No additional milestones or royalties were paid or accrued during the three or nine months ended September 30, 2024 or 2023 related to this agreement. In further consideration of the rights granted, beginning with the Company’s first commercial sale of a Cerecor Licensed Product, the Company will also pay an annual tiered earned royalty in the high single digits in the aggregate on net sales of Cerecor Licensed Products. Royalties are payable, on a Cerecor Licensed Product-by-Cerecor Licensed Product and a country-by-country basis, until the later of the expiration of the last valid claim of a licensed patent covering such Cerecor Licensed Products in such country or 10 years after the first commercial sale of such Cerecor Licensed Product in such country. If the Company develops and commercializes a companion diagnostic as a standalone product in connection with a Cerecor Licensed Product, the Company will be required to make a one-time milestone payment to Cerecor upon the achievement of a specified level of net sales of such companion diagnostic product, at an amount in the very low single digit millions. The license agreement with Cerecor will terminate upon the expiration of the royalty term set forth above. Either the Company or Cerecor may terminate the Cerecor license agreement upon written notice for an uncured material breach of the other party, or in the case of an insolvency event of the other party. The Company may terminate the agreement for any reason upon specified prior written notice to Cerecor. Teva Asset Purchase Agreement Effective October 4, 2021 , the Company entered into an agreement with Teva Pharmaceutical Industries, Ltd to acquire patents, know-how and other rights to ALTO-203 and a specified related compound (the “Teva Acquired Compound”), and assumed all post-acquisition liabilities related thereto. In exchange for the rights granted to the Company, the Company made a cash payment of $0.5 million which is recorded in research and development expenses during the year ended December 31, 2021 in the consolidated statements of operations and comprehensive loss since the acquired license does not have an alternative future use. The Company is obligated to make aggregate cash payments of up to $27.0 million upon the achievement of certain development and regulatory approval milestones, and up to $35.0 million in the aggregate for the achievement of certain tiered sales milestones for any product that incorporates a Teva Acquired Compound (each, a “Teva Product”). In April 2024, the Company achieved a clinical milestone related to the initiation of its Phase 2 proof-of-concept trial evaluating ALTO-203 resulting in a cash payment of $0.5 million which was recorded in research and development expenses during the nine months ended September 30, 2024. No additional milestones or royalties were paid or accrued during the three or nine months ended September 30, 2024 or 2023 related to this agreement. In further consideration of the rights granted, beginning with the Company’s first commercial sale of a Teva Product, the Company will also pay an annual tiered earned royalty ranging from the mid-single-digits to 10 percent on net sales of Teva Products. Royalties are payable, on a Teva Product-by-Teva Product and a country-by-country basis, until the latest to occur of (a) expiration of the last valid claim of an acquired patent covering the composition of matter, or use or formulation of the composition of matter of a Teva Acquired Compound incorporated in or comprising such Teva Product in such country , (b) the expiration of new chemical entity data and/or market exclusivity for such Teva Product in such country or (c) the 10th anniversary of the date of first commercial sale of such Teva Product in such country. Palisade Asset Purchase Agreement Effective October 18, 2021 , the Company entered into an agreement (the “Palisade Agreement”) with Palisade Bio, Inc. (“Palisade”) to acquire all patent, know-how and other rights to ALTO-100. In exchange for the rights granted to the Company, the Company made a cash payment of $0.5 million which is recorded in research and development expenses during the year ended December 31, 2021 in the consolidated statements of operations and comprehensive loss since the acquired license does not have an alternative future use. The Company is obligated to make aggregate cash payments of up to $4.5 million upon the achievement of certain development and regulatory approval milestones. In connection with the sale or license by the Company to a third party of any of the patent, know-how or other rights included in the acquired assets prior to the achievement of a specified clinical development milestone, the Company will be required to pay to Palisade a low-double digit percentage of any consideration received by the Company from such license or sale, provided that the maximum aggregate consideration the Company will be required to pay to Palisade under the Palisade Agreement, including the upfront payment and all potential milestones and transaction-related payments, will not exceed $5.0 million. No additional milestones or royalties were paid or accrued during the three or nine months ended September 30, 2024 or 2023 related to this agreement. MedRx License Agreement On September 25, 2023, the Company entered into a joint development and license agreement (the “MedRx Agreement”) with MedRx Co., Ltd. (“MedRx”), pursuant to which the Company obtained an exclusive, sublicensable, worldwide license, with the right to sublicense, under certain patent rights and know-how of MedRx relating to transdermal drug delivery to develop (excluding any pre-clinical development), manufacture, and commercialize transdermally delivered pharmaceutical products comprising MedRx’s transdermal patch technology and the Company’s ALTO-101 (the “MedRx Licensed Products”) for all therapeutic, prophylactic, and diagnostic uses. The Company granted MedRx an exclusive, sublicensable, worldwide license under certain patent rights and know-how relating to ALTO-101 owned or controlled by the Company, including certain patents and know how licensed to the Company pursuant to the Sanofi Agreement, solely to conduct pre-clinical development and manufacturing of the MedRx Licensed Products for the Company in accordance with the MedRx Agreement and a separate manufacturing and supply agreement to be entered into between the Company and MedRx. During the term of the MedRx Agreement, the Company agreed that it will not, directly or indirectly, develop, manufacture, or commercialize any pharmaceutical product that is a transdermal patch formulation containing similar active pharmaceutical ingredients as ALTO-101 and that is used in the same field and labeled for the same indications as the MedRx Licensed Products (“MedRx Competitive Product”). MedRx agreed that it will not, directly or indirectly, exploit any patch formulations of PDE4-inhibitor drugs for use within central nervous system disorders or exploit any MedRx Competitive Product, provided that if certain specified development or first commercial sale milestones are not achieved by certain specified dates, then MedRx has the right to cause the non-compete restrictions on both parties to lapse. Under the MedRx Agreement, MedRx will be solely responsible for conducting all pre-clinical development of MedRx Licensed Products to support IND and institutional review board filing, and the Company will be solely responsible for all other development (including non-clinical studies and clinical studies) necessary to obtain regulatory approval for MedRx Licensed Products and subsequent commercialization of Products. The Company is obligated to use commercially reasonable efforts to commercialize MedRx Licensed Products in each of the following countries in which the Company has obtained regulatory approval: the United States; at least two of Germany, Spain, France, Italy or the United Kingdom; and one of China or Japan. Pursuant to the MedRx Agreement, the Company paid MedRx an upfront fee of less than $0.2 million, which was recorded within research and development expenses during the year ended December 31, 2023 in the consolidated statements of operations and comprehensive loss since the acquired license does not have an alternative future use. The Company is required to pay MedRx up to an aggregate of $11.0 million for the achievement of certain development and first commercial sale milestones for the first MedRx Licensed Product to achieve such milestones with respect to a first indication, and an additional milestone in the mid single digit millions for each additional approved distinct indication for such first MedRx Licensed Product or a subsequent MedRx Licensed Product. In April 2024, the Company achieved the desired pharmacokinetic profile for ALTO-101 in a Phase 1 trial resulting in a milestone payment to MedRx comprised of $0.75 million, paid in cash, as well as 46,875 shares of the Company’s common stock. The Company recognized $1.5 million of expense related to this milestone, which was recorded in research and development expenses during the nine months ended September 30, 2024. In addition, the Company will be required to pay MedRx sales milestones based on the achievement of specified thresholds of aggregate annual worldwide net sales of all MedRx Licensed Products of up to $110.0 million in the aggregate, if all such sales thresholds are achieved. Commencing on the first commercial sale of a MedRx Licensed Product, the Company will also be obligated to pay MedRx a mid-single digit royalty on annual, worldwide net sales of all MedRx Licensed Products, subject to certain customary reductions and a royalty floor. Royalties will be payable, on a MedRx Licensed Product-by-MedRx Licensed Product and country-by-country basis, until the latest to occur of (a) expiration of the last valid claim of certain specified patent rights covering such MedRx Licensed Products in such country, (b) the expiration of any regulatory exclusivity for such MedRx Licensed Product in such country, (c) the first approval of a specified generic product referencing such MedRx Licensed Product in such country, and (d) the tenth anniversary of the first commercial sale of such MedRx Licensed Product in such country, or the Royalty Term. The MedRx Agreement will expire with respect to each MedRx Licensed Product, on a country-by-country basis, upon the expiration of the Royalty Term, and with respect to the entire MedRx Agreement upon the expiry of the last-to-expire Royalty Term for the last MedRx Licensed Product for which there has been a first commercial sale. Either the Company or MedRx may terminate the MedRx Agreement in its entirety or on a MedRx Licensed Product-by-MedRx Licensed Product basis upon an uncured material breach by the other party or in connection with an insolvency event of such party. In addition, if the Company or MedRx bring or otherwise participate in a patent challenge against any patents licensed by the other party, such other party may terminate the MedRx Agreement immediately. The Company has the right to terminate the MedRx Agreement in its entirety or on a MedRx Licensed Product-by-MedRx Licensed Product basis for any reason upon specified prior written notice to MedRx provided that the effective date of such termination will not be earlier than the completion date of a specified development event. The Company also has the right to terminate the MedRx Agreement with respect to a MedRx Licensed Product immediately upon its reasonable determination of a material safety issue with respect to such MedRx Licensed Product. Except for the $1.5 million milestone discussed above, no additional milestones or royalties were paid or accrued during the nine months ended September 30, 2024 related to this agreement.

Stock-Based Plans

Stock-Based Plans	9 Months Ended
	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Stock-Based Plans	Stock-Based Plans 2024 Equity Incentive Plan In January 2024, the Board adopted, and the Company’s stockholders approved, the 2024 Equity Incentive Plan (the “2024 Plan”), which became effective on the execution of the underwriting agreement related to the IPO. Under the 2024 Plan, the Company may grant incentive stock options to employees, including employees of any parent or subsidiary, and nonstatutory stock options, stock appreciation rights, RSAs, restricted stock unit awards, performance awards and other forms of stock awards to employees, directors, and consultants, including employees and consultants of the Company’s affiliates. The 2024 Plan is a successor to the 2019 Equity Incentive Plan, which was adopted by the Board of Directors in March 2019 (as amended, the “2019 Plan”). A total of 2,000,000 shares of common stock were approved to be initially reserved for issuance under the 2024 Plan. In addition, the number of shares of the Company’s common stock reserved for issuance under the 2024 Plan will automatically increase on January 1 of each calendar year, starting on January 1, 2025 and continuing through and including January 1, 2034, in an amount equal to 5% of the total number of shares of the Company’s common stock outstanding on the last day of the calendar month before the date of each automatic increase, or a lesser number of shares determined by the Board. No future issuances were made under the 2019 Plan upon the effectiveness of the 2024 Plan. As of December 31, 2023, the total number of shares authorized to be issued under the 2019 Plan was 4,078,285. As of September 30, 2024, the total number of shares authorized to be issued under the 2024 Plan was 2,000,000. As of September 30, 2024 and December 31, 2023, there wer e 280,929 and 251,450 shares of common stock, respectively, reserved and available for issuance under the 2024 Plan and 2019 Plan, respectively. Adoption of Employee Stock Purchase Plan In January 2024, the Board adopted, and the Company’s stockholders approved, the 2024 Employee Stock Purchase Plan (the “ESPP”), which became effective on the execution of the underwriting agreement related to the IPO. A total of 250,000 shares of common stock were approved to be initially reserved for issuance under the ESPP. In addition, the number of shares of common stock reserved for issuance under the ESPP will automatically increase on January 1 of each calendar year, beginning on January 1, 2025 and continuing through, and including, January 1, 2034, by the lesser of (1) 1% of the total number of shares of the Company’s common stock outstanding on the last day of the calendar month before the date of the automatic increase, and (2) 750,000 shares; provided, that before the date of any such increase, the Board may determine that such increase will be less than the amount set forth in clauses (1) and (2). As of September 30, 2024, the Company had not opened the ESPP for enrollment, and therefore there were no purchases or share issuances during this period. Stock Options The options have a 10-year life and generally vest over a period of four years, with the first 25% of the award vesting after one year and then monthly thereafter, subject to continuous service. Once the options are exercised, the shares are subject to transfer restrictions under the terms of the Company’s amended and restated certificate of incorporation. The weighted-average grant date fair value of options granted during the three and nine months ended September 30, 2024 for awards subject only to service-based vesting conditions were $8.90 and $11.13 per share, respectively. Weighted-average grant date fair value of options granted during the three and nine months ended September 30, 2023 for awards subject only to service-based vesting conditions were $4.80 and $4.79 per share, respectively. Weighted-average grant date fair value assumptions were based on the following: Nine months ended 2024 2023 Exercise price $ 14.53 $ 6.23 Fair value of common stock $ 14.53 $ 6.23 Expected term (in years) 6.0 6.0 Expected volatility 90.7% 92.4% Risk-free rate 4.1% 3.6% Dividend yield 0.0% 0.0% The table below summarizes activity related to stock options subject only to service-based vesting conditions (in thousands, except per share amounts): Shares Weighted- Weighted – Aggregate Outstanding, December 31, 2023 2,878 $ 4.48 8.7 $ 7,794 Granted 1,682 14.51 Exercised (106) 1.31 1,077 Forfeited and cancelled (101) 6.11 Outstanding, September 30, 2024 4,353 $ 8.40 8.4 $ 18,500 Exercisable at September 30, 2024 1,260 $ 4.13 7.2 $ 9,435 As of September 30, 2024, there was approximate ly $21.9 million of unrecognized stock-based compensation expense related to these service-based unvested stock options which is expected to be recognized ov er a weighted-average period of 2.9 years. Restricted Stock Units The table below summ arizes activity related to restricted stock units (“RSUs”) subject only to service-based vesting conditions (in thousands, except per share amounts): Shares Weighted-average Outstanding, December 31, 2023 — $ — Granted 54 14.88 Vested — — Forfeited and cancelled — — Outstanding, September 30, 2024 54 $ 14.88 On March 1, 2024, the Company issued 53,864 RSUs under the 2024 Plan; 50% of the shares of common stock underlying the RSUs vest after 18 months and the remainder vest after 24 months from the grant date. The RSUs are subject only to a service-based vesting condition. Such shares are not accounted for as outstanding until they vest. As of September 30, 2024, the total unrecognized compensation related to unvested RSUs granted was $0.6 million which is expected to be amortized on a straight-line basis over the weighted-average remaining vesting period of approximately 1.4 years. Performance Option Awards The Board granted options to purchase common stock to certain employees and consultants that vest upon the achievement of certain performance conditions (“Performance Awards”) such as the completion of a future financing event or upon the achievement of defined clinical milestones or outcomes. The Company did not issue any Performance Awards during the three or nine months ended September 30, 2024 and 2023. The Performance Awards have a contractual term of ten years. During the nine months ended September 30, 2023, clinical milestones were met which resulted in the vesting of 179,846 Performance Awards, respectively, and the recognition of $0.8 million of stock-based compensation expense. During the nine months ended September 30, 2024, certain financial milestones were met which resulted in the vesting of 194,835 Performance Awards, and the recognition of $0.9 million of stock-based compensation expense. As of September 30, 2024, there w ere 592,748 Performance Awards still outstanding, with a weighted-average exercise price of $4.63 per share, of which none remain unvested. The remaining contractual life of the Performance Awards was 8.0 years as of September 30, 2024. Stock-based Compensation Expense Non-cash stock-based compensation expense recognized in the accompanying condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2024 and 2023 was as follows (in thousands): Three months ended Nine months ended 2024 2023 2024 2023 Research and development $ 1,025 $ 433 $ 2,891 $ 1,803 General and administrative 973 108 3,174 482 Total stock-based compensation expense $ 1,998 $ 541 $ 6,065 $ 2,285 Restricted Stock Awards

Leases

Leases	9 Months Ended
	Sep. 30, 2024
Leases [Abstract]
Leases	Leases On May 29, 2024, the Company and Mountain View City Center, LP (“Landlord”) entered into a lease agreement (the “2024 Lease Agreement”) for 16,332 square feet of office space in a multi-tenant building located in Mountain View, California with an initial lease term of 65 months. The Company will make payments of approximately $7.1 million over the course of the initial term of the lease. In connection with the 2024 Lease Agreement, the Company secured a letter of credit amounting to $0.5 million, which was recorded in restricted cash on its condensed consolidated balance sheet as of September 30, 2024. At the Company’s option, it may renew the lease for one three-year period. The Company also has a one-time option to terminate the lease after the third lease year. If the Company elects to terminate the lease after the third lease year, the Company will make payments of approximately $4.1 million over the term of the lease. The Company obtained control of the space, and, accordingly, the Company recorded related operating right-of-use assets and the lease liabilities during the third quarter of 2024. The Company recorded the liability associated with the 2024 Lease Agreement at the present value of the lease payments not yet paid, using the discount rate as of the commencement date. As the discount rate implicit in the 2024 Lease Agreement was not readily determinable, the Company utilized its incremental borrowing rate. The renewal or early termination options were not assumed to be exercised in the determination of the lease term, since they are not deemed to be reasonably certain at the inception of the lease. At lease commencement, the Company recorded an operating right-of-use asset and lease liability of $5.2 million. The 2024 Lease Agreement does not contain material residual value guarantees, restrictions, or covenants. The components of lease expense were as follows (in thousands): Three months ended September 30, 2024 Operating lease expense $ 107 Variable lease expense — Total lease expense $ 107 Short-term lease costs were not material for the three and nine months ended September 30, 2024 or 2023. Supplemental cash flow information related to operating leases for the three months ended September 30, 2024 (in thousands): September 30, Cash paid for amounts included in the measurement of lease liabilities $ — Supplemental balance sheet information related to operating leases as of September 30, 2024 was as follows (in thousands): September 30, Operating lease right-of-use assets $ 5,225 Operating lease liability—current portion (included in accrued expenses and other current liabilities) 716 Operating lease liability, long-term 4,616 Total operating lease liabilities $ 5,332 Weighted average lease term (in years) 5.4 Weighted average discount rate 9.71 % As of September 30, 2024 , the future payments under operating leases were as follows (in thousands): For the year ending December 31, 2024 $ 76 2025 917 2026 1,216 2027 1,456 2028 1,500 Thereafter 1,977 Total lease payments 7,142 Less: imputed interest (1,810) Present value of lease payments $ 5,332

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes There is no provision for income taxes. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are provided if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets, including its net operating losses. Based on its history of operating losses, the Company believes that it is more likely than not that the benefit of its deferred tax assets will not be realized. Accordingly, the Company has provided a full valuation allowance for its net deferred tax assets as of September 30, 2024 and December 31, 2023.

Convertible Preferred Stock and

Convertible Preferred Stock and Stockholders’ Equity (Deficit)	9 Months Ended
	Sep. 30, 2024
Equity [Abstract]
Convertible Preferred Stock and Stockholders’ Equity (Deficit)	Convertible Preferred Stock and Stockholders’ Equity (Deficit) Convertible Preferred Stock Upon closing of the IPO in February 2024, all of the outstanding convertible preferred stock automatically converted into 13,664,261 shares of common stock. Subsequent to the closing of the IPO, there were no shares of convertible preferred stock outstanding. At December 31, 2023, convertible preferred stock consisted of the following (in thousands): Share Class Shares Shares Carrying Liquidation Series Seed Preferred 3,709 3,709 $ 7,674 $ 7,722 Series A Preferred 7,251 6,785 30,489 31,887 Series B Preferred 9,877 9,877 58,918 62,095 Series C Preferred 10,675 9,548 44,396 45,000 Total 31,512 29,919 $ 141,477 $ 146,704 Preferred Stock In January 2023, the Company sold 4,166,667 additional shares of Series B Preferred Stock to a new investor at $6.00 per share for gross proceeds of $25.0 million. Series A Preferred Stock Warrants In May 2021, in connection with the closing of the Series A Preferred Stock Agreement, the Company issued warrants to the lead Series A investor to purchase an aggregate of 465,917 shares of Series A Preferred Stock (“Series A Preferred Stock Warrants”) at a price of $4.6996 per share (“Exercise Price”). The Series A Preferred Stock Warrants expire, and if not earlier exercised, will be automatically net exercised, on the earliest to occur of (i) the closing of a deemed liquidation event; (ii) the closing of the sale of shares of common stock in a public offering resulting in at least $75.0 million of gross proceeds and a share price of at least $15.68 per share (one and one half times the Exercise Price as adjusted by the reverse stock split discussed in Note 1 ); (iii) immediately prior to the consummation of a SPAC transaction in which the combined company, immediately following the closing of the SPAC transaction, holds at least $75.0 million in unrestricted cash; or (iv) May 3, 2026. A s of September 30, 2023, th e Company remeasured the fair value of the Series A Preferred Stock Warrants. The remeasured fair value of the Series A Preferred Stock Warrants as of September 30, 2023 was $1.4 million, resulting in an immaterial non-c ash expense w hich was recorded in the condensed consolidated statements of operations and comprehensive loss during the three and nine months ended September 30, 2023. In February 2024, in connection with the IPO, the Series A Preferred Stock Warrants were exercised and net settled for shares of the Company’s common stock, which resulted in the issuance of 72,631 shares of common stock. The Company remeasured the fair value of the Series A Preferred Stock Warrants immediately prior to their exercise, resulting in an insignificant change in fair value from December 31, 2023. The resulting warrant liability was then extinguished upon the net exercise. K2 Warrant In December 2022, in connection with the closing of the Loan Agreement, the Company issued a warrant to the Lender to purchase a number of shares of the Company’s Series B convertible preferred stock, or at Lender’s election, next round stock (“K2 Warrant”). The number of shares of convertible preferred stock issuable upon exercise of the warrant is equal to (a) (i) 0.0375, multiplied by (ii) the aggregate principal amount of term loans actually funded under the Loan Agreement, divided by (b) the warrant price then in effect. If exercised for Series B preferred stock, the exercise price is $6.00 per share, which would result in the issuance of an aggregate of 62,500 shares of Series B Preferred Stock. In January 2023, the Company completed a forward stock split of outstanding Series B Preferred Stock of 1.1156 for 1 to give effect to the $6.00 per share price across the entire Series B Preferred Stock share class. Following the sale and issuance of the Series C Preferred Stock in November 2023 and as of December 31, 2023, the exercise price of the warrants is $4.7132 per share, which would result in the issuance of an aggregate of 79,564 shares of Series C Preferred Stock. Following the conversion of Series C Preferred Stock to common stock upon the completion of the IPO in February 2024, the K2 Warrant became a warrant to purchase up to an aggregate of 35,773 shares of the Company’s common stock at an exercise price of $10.49 per share. The K2 Warrant was remeasured to fair value immediately prior to the conversion to a common stock warrant, and the change in fair value since December 31, 2023 was $0.2 million. The Company determined that the K2 Warrant is equity-classified, and therefore the resulting warrant liability was reclassified to permanent equity, and is not subject to future remeasurement. The following table summarizes the change in fair value of the preferred stock warrant liability, a Level 3 recurring fair value measurement, for the nine months ended September 30, 2024 (in thousands): Preferred Balance at December 31, 2023 $ 1,352 Issuance of Preferred Stock Warrants — Exercise — Expiration — Change in fair value 243 Balance at February 2, 2024 $ 1,595 Reclassification to equity (1) $ (1,595) Balance at September 30, 2024 $ — (1) During the first quarter of 2024, the Company reclassified the warrant liability to equity directly as a result of the IPO. Common Stock and Authorized Shares As of September 30, 2024 and December 31, 2023, the Company h ad 500,000,000 and 52,000,000 authorized shares of common stock, respectively, with a par value of $0.0001 per share, of which 26,968,198 and 3,832,134 shares, respectively, were issued and outstanding. On February 6, 2024, the Company amended its certificate of incorporation such that the total number of shares of common stock authorized to be issued was increased to 500,000,000, and the total number of shares of new preferred stock authorized to be issued was 10,000,000 with a par value per share of $0.0001. As of September 30, 2024, no shares of preferred stock were issued or outstanding. As of September 30, 2024 and December 31, 2023, the Company had reserved common stock, on an as-if converted basis, for issuance as follows (in thousands): September 30, December 31, Series Seed Preferred Stock — 1,668 Series A Preferred Stock — 3,051 Series B Preferred Stock — 4,653 Series C Preferred Stock — 4,293 Series A Preferred Stock Warrants — 209 K2 Warrant 36 36 Stock options issued and outstanding 4,946 3,471 Stock options available for future grant 281 251 Total 5,263 17,632

Loss Per Share

Loss Per Share	9 Months Ended
	Sep. 30, 2024
Earnings Per Share [Abstract]
Loss Per Share	Loss Per Share Basic net loss per common share is computed by dividing net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding for the period. The Company’s unvested restricted common stock is not included in the determination of loss per share until the award vests. Diluted net loss per common share excludes the potential impact of the Company’s convertible preferred stock and warrants because their effect would be anti-dilutive due to the Company’s net loss. Since the Company had a net loss in each of the periods presented, basic and diluted net loss per common share are the same. The following outstanding potentially dilutive common stock equivalents were excluded from the computation of diluted net loss per share for the periods presented because including them would have been antidilutive (in thousands): September 30, 2024 2023 Convertible Preferred Stock (as if converted) — 9,159 Preferred Stock Warrants — 238 Common Stock Warrant 36 — Restricted Stock Units and Award 54 34 Stock options issued and outstanding 4,946 2,534 Total 5,036 11,965

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies From time to time, the Company is subject to occasional lawsuits, investigations and claims arising out of the ordinary course of business. The Company has no significant pending or threatened litigation as of September 30, 2024. In the ordinary course of business, the Company enters into contracts that contain a variety of indemnifications with its employees, licensors, suppliers and service providers. Further, the Company indemnifies its directors and officers who are, or were, serving at the Company’s request in such capacities. The Company’s maximum exposure under these arrangements is unknown at September 30, 2024. The Company does not anticipate recognizing any significant losses relating to these arrangements.

Retirement Plan

Retirement Plan	9 Months Ended
	Sep. 30, 2024
Retirement Benefits [Abstract]
Retirement Plan	Retirement Plan The Company has established a defined contribution 401(k) plan (the “401(k) Plan”) for the benefit of its employees. All of the full-time employees of the Company are eligible to participate in the 401(k) Plan which permits employees to make voluntary contributions up to the dollar limit allowed under the Internal Revenue Code. Beginning in January 2022, the 401(k) Plan also provides for matching contributions as defined by the Company of up to a combined total of 3% of an employee’s eligible annual compensation. During the

Summary of Significant Accoun_2

Summary of Significant Accounting Policies and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying interim condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) as determined by the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”), and include the accounts of Alto and its wholly-owned subsidiary. All intercompany transactions and balances have been eliminated in consolidation. The interim condensed consolidated financial statements are unaudited and have been prepared on the same basis as the audited annual financial st atements and, in management’s opinion, include all adjustments consisting of only normal recurring adjustments necessary for the fair statement of the Company’s financial position as of September 30, 2024 and its results of operations and statements of equity for the three and nine months ended September 30, 2024 and 2023 and cash flows for the nine months ended September 30, 2024 and 2023. The results o f operations for the three and nine months ended September 30, 2024 are not necessarily indicative of the results to be expected for the full fiscal year or any other period. Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. These interim condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements and the related notes thereto for the year ended December 31, 2023 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission on March 21, 2024.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results may differ materially from those estimates. The most significant estimates and assumptions in the Company’s condensed consolidated financial statements relate to the determination of the fair value of its common stock (as an input for calculating stock-based compensation), estimating accrued or prepaid research and development expenses, and the valuation of the preferred stock warrant liability. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. To the extent there are material differences between the estimates and actual results, the Company’s future results of operations will be affected.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In December 2023, the FASB issued Accounting Standards Update (“ASU”) No. 2023-09, Income Taxes (“Topic 740”). The standard requires disaggregation of the effective rate reconciliation into standard categories, enhances disclosure of income taxes paid, and modifies other income tax-related disclosures. The standard will be effective starting in annual periods beginning after December 15, 2024, with early adoption permitted. The Company is currently assessing the impact of adopting this guidance on its condensed consolidated financial statements. In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting - Improving Reportable Segment Disclosures (“Topic 280”). The standard requires disclosures to include significant segment expenses that are regularly provided to the chief operating decision maker (“CODM”), a description of other segment items by reportable segment, and any additional measures of a segment's profit or loss used by the CODM when deciding how to allocate resources. The ASU also requires all annual disclosures currently required by Topic 280 to be included in interim periods. The standard is effective starting in annual periods beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024 with early adoption permitted and requires retrospective application to all prior periods presented in the financial statements. The Company is currently assessing the impact of adopting this guidance on its condensed consolidated financial statements.

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of prepaid expenses and other current assets	Prepaid expenses and other current assets consist of the following (in thousands): September 30, December 31, Prepayments $ 853 $ 522 Other current assets 277 104 Deferred offering costs — 2,209 Prepaid insurance 695 — Total prepaid expenses and other current assets $ 1,825 $ 2,835
Schedule of property and equipment, net	Property and equipment, net are as follows (in thousands): September 30, December 31, Office equipment and furniture $ 284 $ 70 Computer software and equipment 421 519 Laboratory equipment 2,306 1,201 Construction in progress 251 — Less : accumulated depreciation (909) (684) Property and equipment, net $ 2,353 $ 1,106
Schedule of accrued liabilities	Accrued expenses and other current liabilities consist of the following (in thousands): September 30, December 31, Accrued payroll, vacation and employee-related expenses $ 3,879 $ 518 Accrued research 2,683 2,328 Accrued offering and share issue cost — 916 Accrued license fees 19 50 Accrued interest, short term 81 84 Other accruals and current liabilities 856 515 Lease liability, short term 716 125 Total accrued expenses and other current liabilities $ 8,234 $ 4,536

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2024
Debt Disclosure [Abstract]
Schedule of future principal debt payments and exit fee	Future principal debt payments and Exit Fee of the term loan funded as of September 30, 2024 are as follows (in thousands): 2024 (remainder of year) $ — 2025 4,767 2026 5,233 Total principal payments 10,000 Exit Fee 625 Deferred Interest 184 Total principal payments and Exit Fee 10,809 Less: unamortized Exit Fee (352) Less: unamortized debt discount related to warrants (118) Less: unamortized debt issuance costs, including Facility Fee (183) Term loan, net $ 10,156 Less: Term loan, current portion (3,529) Term loan, non-current $ 6,627 Future principal debt payments of the Convertible Grant Agreement funded as of September 30, 2024 are as follows (in thousands): 2024 (remainder of year) $ — 2025 — 2026 — 2027 — 2028 — 2029 1,250 Term loan, non-current $ 1,250
Fair Value, Liabilities Measured on Recurring Basis	The following table reconciles the change in fair value of the Convertible Grant Agreement during the three months ended September 30, 2024 (in thousands): Beginning fair value balance, July 2024 $ — Recognition of Convertible Grant Agreement 1,250 Principal payments — Changes in fair value reported in statement of operation 48 Changes in fair value reported in comprehensive loss — Ending fair value balances as of September 30, 2024 $ 1,298

Fair Value (Tables)

Fair Value (Tables)	9 Months Ended
	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Schedule of classes of financial assets and liabilities measured at fair value on recurring basis	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): December 31, 2023 Total Level 1 Level 2 Level 3 Assets: Cash equivalents - money market funds $ 82,548 $ 82,548 $ — $ — Total assets $ 82,548 $ 82,548 $ — $ — Liabilities: Preferred stock warrant liability $ 1,352 $ — $ — $ 1,352 Total liabilities $ 1,352 $ — $ — $ 1,352 September 30, 2024 Total Level 1 Level 2 Level 3 Assets: Cash and cash equivalents: Money market funds $ 181,448 $ 181,448 $ — $ — Restricted cash: Money market funds 500 500 — — Total assets $ 181,948 $ 181,948 $ — $ — Liabilities: Convertible Grant Agreement 1,298 — — 1,298 Total liabilities $ 1,298 $ — $ — $ 1,298

Stock-Based Plans (Tables)

Stock-Based Plans (Tables)	9 Months Ended
	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Schedule of share-based payment award, stock options, valuation assumptions	Weighted-average grant date fair value assumptions were based on the following: Nine months ended 2024 2023 Exercise price $ 14.53 $ 6.23 Fair value of common stock $ 14.53 $ 6.23 Expected term (in years) 6.0 6.0 Expected volatility 90.7% 92.4% Risk-free rate 4.1% 3.6% Dividend yield 0.0% 0.0%
Disclosure of share-based compensation arrangements by share-based payment award	The table below summarizes activity related to stock options subject only to service-based vesting conditions (in thousands, except per share amounts): Shares Weighted- Weighted – Aggregate Outstanding, December 31, 2023 2,878 $ 4.48 8.7 $ 7,794 Granted 1,682 14.51 Exercised (106) 1.31 1,077 Forfeited and cancelled (101) 6.11 Outstanding, September 30, 2024 4,353 $ 8.40 8.4 $ 18,500 Exercisable at September 30, 2024 1,260 $ 4.13 7.2 $ 9,435
Share-based payment arrangement, restricted stock unit, activity	The table below summ arizes activity related to restricted stock units (“RSUs”) subject only to service-based vesting conditions (in thousands, except per share amounts): Shares Weighted-average Outstanding, December 31, 2023 — $ — Granted 54 14.88 Vested — — Forfeited and cancelled — — Outstanding, September 30, 2024 54 $ 14.88
Share-based payment arrangement, cost by plan	Non-cash stock-based compensation expense recognized in the accompanying condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2024 and 2023 was as follows (in thousands): Three months ended Nine months ended 2024 2023 2024 2023 Research and development $ 1,025 $ 433 $ 2,891 $ 1,803 General and administrative 973 108 3,174 482 Total stock-based compensation expense $ 1,998 $ 541 $ 6,065 $ 2,285

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2024
Leases [Abstract]
Schedule of lease cost	The components of lease expense were as follows (in thousands): Three months ended September 30, 2024 Operating lease expense $ 107 Variable lease expense — Total lease expense $ 107 Short-term lease costs were not material for the three and nine months ended September 30, 2024 or 2023. Supplemental cash flow information related to operating leases for the three months ended September 30, 2024 (in thousands): September 30, Cash paid for amounts included in the measurement of lease liabilities $ —
Schedule of supplemental balance sheet information	Supplemental balance sheet information related to operating leases as of September 30, 2024 was as follows (in thousands): September 30, Operating lease right-of-use assets $ 5,225 Operating lease liability—current portion (included in accrued expenses and other current liabilities) 716 Operating lease liability, long-term 4,616 Total operating lease liabilities $ 5,332 Weighted average lease term (in years) 5.4 Weighted average discount rate 9.71 %
Schedule of operating lease maturity	As of September 30, 2024 , the future payments under operating leases were as follows (in thousands): For the year ending December 31, 2024 $ 76 2025 917 2026 1,216 2027 1,456 2028 1,500 Thereafter 1,977 Total lease payments 7,142 Less: imputed interest (1,810) Present value of lease payments $ 5,332

Convertible Preferred Stock a_2

Convertible Preferred Stock and Stockholders’ Equity (Deficit) (Tables)	9 Months Ended
	Sep. 30, 2024
Equity [Abstract]
Convertible preferred stock by class	At December 31, 2023, convertible preferred stock consisted of the following (in thousands): Share Class Shares Shares Carrying Liquidation Series Seed Preferred 3,709 3,709 $ 7,674 $ 7,722 Series A Preferred 7,251 6,785 30,489 31,887 Series B Preferred 9,877 9,877 58,918 62,095 Series C Preferred 10,675 9,548 44,396 45,000 Total 31,512 29,919 $ 141,477 $ 146,704
Change in fair value of the preferred stock warrant liability	The following table summarizes the change in fair value of the preferred stock warrant liability, a Level 3 recurring fair value measurement, for the nine months ended September 30, 2024 (in thousands): Preferred Balance at December 31, 2023 $ 1,352 Issuance of Preferred Stock Warrants — Exercise — Expiration — Change in fair value 243 Balance at February 2, 2024 $ 1,595 Reclassification to equity (1) $ (1,595) Balance at September 30, 2024 $ — (1) During the first quarter of 2024, the Company reclassified the warrant liability to equity directly as a result of the IPO.
Schedule of stock reserved for issuance	As of September 30, 2024 and December 31, 2023, the Company had reserved common stock, on an as-if converted basis, for issuance as follows (in thousands): September 30, December 31, Series Seed Preferred Stock — 1,668 Series A Preferred Stock — 3,051 Series B Preferred Stock — 4,653 Series C Preferred Stock — 4,293 Series A Preferred Stock Warrants — 209 K2 Warrant 36 36 Stock options issued and outstanding 4,946 3,471 Stock options available for future grant 281 251 Total 5,263 17,632

Loss Per Share (Tables)

Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2024
Earnings Per Share [Abstract]
Schedule of antidilutive securities excluded from computation of earnings per share	The following outstanding potentially dilutive common stock equivalents were excluded from the computation of diluted net loss per share for the periods presented because including them would have been antidilutive (in thousands): September 30, 2024 2023 Convertible Preferred Stock (as if converted) — 9,159 Preferred Stock Warrants — 238 Common Stock Warrant 36 — Restricted Stock Units and Award 54 34 Stock options issued and outstanding 4,946 2,534 Total 5,036 11,965

Description of the Business (De

Description of the Business (Details) $ / shares in Units, $ in Thousands		1 Months Ended
	Feb. 06, 2024 USD ($) $ / shares shares	Jan. 31, 2024 Rate	Jan. 31, 2023 Rate	Sep. 30, 2024 USD ($) subsidiary clinical-stageAsset	Dec. 31, 2023 USD ($)
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Number of wholly owned subsidiaries | subsidiary				1
Number of clinical-stage assets | clinical-stageAsset				5
Stock split, conversion ratio | Rate		44.62%	111.56%
Accumulated deficit				$ 123,195	$ 76,965
IPO
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Sale of stock, number of shares issued in transaction (in shares) | shares	9,246,000
Sale of stock, price per share (in dollars per share) | $ / shares	$ 16
Sale of stock, consideration received on transaction	$ 133,000
Underwriting discounts and commissions	10,400
Offering expenses	$ 4,600
Number of shares called by warrants (in shares) | shares	72,631
Over-Allotment Option
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Sale of stock, number of shares issued in transaction (in shares) | shares	1,206,000

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of prepaid expenses and other current assets (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Prepayments	$ 853	$ 522
Other current assets	277	104
Deferred offering costs	0	2,209
Prepaid insurance	695	0
Total prepaid expenses and other current assets	$ 1,825	$ 2,835

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of property and equipment, net (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Less: accumulated depreciation	$ (909)	$ (684)
Property and equipment, net	2,353	1,106
Office equipment and furniture
Property, Plant and Equipment [Line Items]
Property equipment, gross	284	70
Computer software and equipment
Property, Plant and Equipment [Line Items]
Property equipment, gross	421	519
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property equipment, gross	2,306	1,201
Construction in progress
Property, Plant and Equipment [Line Items]
Property equipment, gross	$ 251	$ 0

Balance Sheet Components - Narr

Balance Sheet Components - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Depreciation and amortization	$ 200	$ 100	$ 332	$ 261

Balance Sheet Components - Sc_3

Balance Sheet Components - Schedule of accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued payroll, vacation and employee-related expenses	$ 3,879	$ 518
Accrued research	2,683	2,328
Accrued offering and share issue cost	0	916
Accrued license fees	19	50
Accrued interest, short term	81	84
Other accruals and current liabilities	856	515
Lease liability, short term	716	125
Total accrued expenses and other current liabilities	$ 8,234	$ 4,536

Debt - Narrative (Details)

Debt - Narrative (Details) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended
	Dec. 16, 2022 USD ($) loan tranche $ / shares	Jul. 31, 2024	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)
Debt Instrument [Line Items]
Interest rate, basis spread (greater of)		2%
Deferred interest accrued, percent	1%
Exit fee			$ 625		$ 625
Proceeds from Convertible Grant Agreement					$ 1,250	$ 0
Loan and Security Agreement | Secured Debt
Debt Instrument [Line Items]
Aggregate principle amount (up to)	$ 35,000
Number of potential tranches | tranche	4
Number of term loan facilities | loan	4
Current amount potentially accessible	$ 10,000
Remaining amount available on credit facility	$ 25,000
Interest rate, basis spread (greater of)	1.20%
Term of credit facility	48 months
Final fee, percent of loan funded	6.25%
Prepayment fee, percent of outstanding principle, applicable on or before 24 months after initial funding date	3%
Prepayment fee, percent of outstanding principle, applicable after 24 months and on or before 36 months after initial funding date	2%
Prepayment fee, percent of outstanding principle, applicable on or before 36 months after initial funding date	1%
One-time facility fee	$ 200
Conversion price per share | $ / shares	$ 10.49
Interest rate increase in event of default	5%
Weighted average interest rate			10.63%		10.68%
Interest expense			$ 300	$ 400	$ 1,000	$ 1,000
Loan and Security Agreement | Secured Debt | Minimum
Debt Instrument [Line Items]
Interest rate (greater of)	6.70%
Loan and Security Agreement | Secured Debt | Maximum
Debt Instrument [Line Items]
Amount of debt convertible to equity at election of lender	$ 4,000
Loan and Security Agreement | Secured Debt | First tranche, funded on December 16, 2022
Debt Instrument [Line Items]
Term loan	$ 10,000
Interest only payment term	24 months
Extension term of interest only payments	12 months
Equity sales (greater than)	$ 75,000
Exit fee	600
Loan and Security Agreement | Secured Debt | Second tranche, available between October 1, 2023 and March 1, 2024
Debt Instrument [Line Items]
Aggregate principle amount (up to)	7,500
Loan and Security Agreement | Secured Debt | Third tranche, available from October 1, 2023 and March 1, 2024
Debt Instrument [Line Items]
Aggregate principle amount (up to)	7,500
Loan and Security Agreement | Secured Debt | Fourth tranche, available through January 1, 2025
Debt Instrument [Line Items]
Aggregate principle amount (up to)	$ 10,000
Percent of fourth tranche term loan when funded	0.70%

Debt - Schedule of future princ

Debt - Schedule of future principal debt payments and exit fee (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Debt Disclosure [Abstract]
2024 (remainder of year)	$ 0
2025	4,767
2026	5,233
Total principal payments	10,000
Exit Fee	625
Deferred Interest	184
Total principal payments and Exit Fee	10,809
Less: unamortized Exit Fee	(352)
Less: unamortized debt discount related to warrants	(118)
Less: unamortized debt issuance costs, including Facility Fee	(183)
Term loan, net	10,156
Less: Term loan, current portion	(3,529)	$ 0
Term loan, non-current	$ 6,627	$ 9,861

Debt - Convertible Grant Narrat

Debt - Convertible Grant Narrative (Details) $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended
	Jul. 31, 2024 USD ($) tranche shares	Sep. 30, 2024 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)
Debt Instrument [Line Items]
Convertible Grant Agreement		$ 1,298	$ 1,298
Proceeds from Convertible Grant Agreement			$ 1,250	$ 0
Interest rate, basis spread (greater of)	2%
Variable rate threshold for potential adjustment	9%
Grant Agreement | Convertible Debt
Debt Instrument [Line Items]
Number of tranches | tranche	6
Discount on shares	20%
Term of weighted average price for share conversion	30 days
Maximum shares issuable (in shares) | shares	5,363,326
Maximum percentage of outstanding stock	19.90%
Grant Agreement | Convertible Debt | Maximum
Debt Instrument [Line Items]
Term loan	$ 11,700
First tranche, funded on December 16, 2022 | Grant Agreement | Convertible Debt
Debt Instrument [Line Items]
Convertible Grant Agreement	1,300
Aggregate principle amount (up to)	$ 2,000
Proceeds from Convertible Grant Agreement		$ 1,300
First tranche, funded on December 16, 2022 | Grant Agreement | Convertible Debt | Measurement Input, Discount Rate
Debt Instrument [Line Items]
Debt Instrument, Measurement Input	0.1117	0.1022	0.1022

Debt - Convertible Grant Maturi

Debt - Convertible Grant Maturity (Details) $ in Thousands	Sep. 30, 2024 USD ($)
Debt Instrument [Line Items]
2024 (remainder of year)	$ 0
2025	4,767
2026	5,233
Long-Term Debt, Term	10,156
Convertible Debt
Debt Instrument [Line Items]
2024 (remainder of year)	0
2025	0
2026	0
Long-Term Debt, Maturity, Year Three	0
Long-Term Debt, Maturity, Year Four	0
Long-Term Debt, Maturity, Year Five	1,250
Long-Term Debt, Term	$ 1,250

Debt - Change in Fair Value of

Debt - Change in Fair Value of Convertible Grant Agreement (Details) - Convertible Debt $ in Thousands	2 Months Ended
	Sep. 30, 2024 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 0
Recognition of Convertible Grant Agreement	1,250
Principal payments	0
Changes in fair value reported in statement of operation	48
Changes in fair value reported in comprehensive loss	0
Ending balance	$ 1,298

Fair Value (Details)

Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Assets
Cash and cash equivalents	$ 181,701	$ 82,548
Total assets	181,948	82,548
Liabilities:
Preferred stock warrant liability		1,352
Convertible Grant Agreement	1,298
Total liabilities	1,298	1,352
Money Market Funds
Assets
Cash and cash equivalents	181,448	82,548
Restricted cash	500
Level 1
Assets
Total assets	181,948	82,548
Liabilities:
Preferred stock warrant liability		0
Convertible Grant Agreement	0
Total liabilities	0	0
Level 1 | Money Market Funds
Assets
Cash and cash equivalents	181,448	82,548
Restricted cash	500
Level 2
Assets
Total assets	0	0
Liabilities:
Preferred stock warrant liability		0
Convertible Grant Agreement	0
Total liabilities	0	0
Level 2 | Money Market Funds
Assets
Cash and cash equivalents	0	0
Restricted cash	0
Level 3
Assets
Total assets	0	0
Liabilities:
Preferred stock warrant liability		1,352
Convertible Grant Agreement	1,298
Total liabilities	1,298	1,352
Level 3 | Money Market Funds
Assets
Cash and cash equivalents	0	$ 0
Restricted cash	$ 0

Asset Purchase and License Ag_2

Asset Purchase and License Agreements (Details)						1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 25, 2023 USD ($)	Oct. 18, 2021 USD ($)	Oct. 04, 2021 USD ($)	May 28, 2021 USD ($)	May 18, 2021 USD ($)	Apr. 30, 2024 USD ($) shares	Apr. 30, 2020 shares	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2021 USD ($) shares	Dec. 06, 2019 patentFamily invention
Other Commitments [Line Items]
Research and development								$ 13,060,000	$ 7,967,000	$ 36,196,000	$ 20,648,000
Stanford License Agreement | Leland Stanford Junior University
Other Commitments [Line Items]
Number of inventions | invention														4
Shares issued for license agreement | shares							71,370						32,978
Number of shares on a fully diluted basis as a percentage of equity														1%
Antidilution rights, collectively maintained percent of equity ownership														1%
Stanford Licensed Patents | Leland Stanford Junior University
Other Commitments [Line Items]
Number of patent families | patentFamily														5
Sanofi License Agreement
Other Commitments [Line Items]
Research and development													$ 500,000
Licensing agreement, aggregate maximum milestone payment					$ 102,000,000
Licensing agreement, milestone payments								0	0	0	0
License agreement, term of royalties on licensed patent				10 years	10 years
Cerecor License Agreement
Other Commitments [Line Items]
Research and development													500,000
Licensing agreement, aggregate maximum milestone payment				$ 59,100,000
Licensing agreement, milestone payments								0	0	0	0
Cerecor License Agreement | Merck
Other Commitments [Line Items]
Licensing agreement, aggregate maximum milestone payment				$ 15,000,000
Teva Asset Purchase Agreement
Other Commitments [Line Items]
Research and development										500,000			500,000
Asset Purchase agreement, aggregate amount of milestone payments (up to)			$ 27,000,000
Asset purchase agreement, aggregate tiered sales milestone payments (up to)			$ 35,000,000
Asset purchase agreement, milestone payments								0	0	0	0
Annual tiered royalty payments, percent of net sales			10%
Asset purchase agreement, term of royalties on licensed patent			10 years
Palisade Asset Purchase Agreement
Other Commitments [Line Items]
Research and development													$ 500,000
Asset Purchase agreement, aggregate amount of milestone payments (up to)		$ 4,500,000
Asset purchase agreement, milestone payments								$ 0	$ 0	0	$ 0
Asset purchase agreement, combined upfront and milestone payments		$ 5,000,000
MedRX License Agreement
Other Commitments [Line Items]
Research and development										1,500,000		$ 200,000
Licensing agreement, aggregate maximum milestone payment	$ 110,000,000
Licensing agreement, milestone payments						$ 750,000
Asset purchase agreement, milestone payments										$ 0
Licensing agreement, aggregate milestone payments after first commercial sales (up to)	$ 11,000,000
Shares issued subject to lockup agreement (in shares) | shares						46,875

Stock-Based Plans - Narrative (

Stock-Based Plans - Narrative (Details) - USD ($)		1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 01, 2024	Jan. 31, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Shares reserved for issuance under ESPP plan (in shares)			5,263,000		5,263,000		17,632,000
Stock-based compensation expense			$ 1,998,000	$ 541,000	$ 6,065,000	$ 2,285,000
Employee Stock Purchase Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Annual increase, percentage of outstanding shares		1%
Shares reserved for issuance under ESPP plan (in shares)		250,000
Additional shares reserved for annual increase in ESPP (in shares)		750,000
Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expiration period of options		10 years
Vesting period		4 years
Weighted average grant date fair value (in dollars per share)			$ 8.90	$ 4.80	$ 11.13	$ 4.79
Unrecognized stock-based compensation			$ 21,900,000		$ 21,900,000
Period for recognition of unrecognized share based compensation					2 years 10 months 24 days
Stock Options | Vested after 18 months
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period		1 year
Percentage vested in year one		25%
Restricted Stock Units (RSUs)
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Period for recognition of unrecognized share based compensation			1 year 4 months 24 days
RSU unrecognized compensation			$ 600,000		$ 600,000
Granted (in shares)					54,000
Clinical milestones met, shares vested (in shares)					0
Awards still outstanding (in shares)			54,000		54,000		0
Performance Shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expiration period of options					10 years
Clinical milestones met, shares vested (in shares)					194,835	179,846
Stock-based compensation expense					$ 900,000	$ 800,000
Awards still outstanding (in shares)			592,748		592,748
Weighted average exercise price (in dollars per share)					$ 4.63
Remaining contractual life of awards					8 years
Restricted Stock Units and Award | Chief Executive Officer
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock-based compensation expense			$ 0		$ 0
Awards still outstanding (in shares)			0		0		21,075
The 2024 Equity Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of shares approved, initially reserved for issuance under plan (in shares)		2,000,000	2,000,000		2,000,000
Shares reserved for issuance under ESPP plan (in shares)			280,929		280,929
The 2024 Equity Incentive Plan | Restricted Stock Units (RSUs) | Vested after 18 months
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period	18 months
Percentage vested in year one	50%
The 2024 Equity Incentive Plan | Restricted Stock Units (RSUs) | Vested after 24 months
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period	24 months
Percentage vested in year one	50%
The 2024 Equity Incentive Plan | Restricted Stock Units (RSUs) | Common Stock
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
RSUs issued (in shares)	53,864
The 2019 Equity Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of shares approved, initially reserved for issuance under plan (in shares)							4,078,285
Annual increase, percentage of outstanding shares		5%
Shares reserved for issuance under ESPP plan (in shares)							251,450

Stock-Based Plans - Stock optio

Stock-Based Plans - Stock option weighted average assumptions (Details) - Stock Options - $ / shares	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Exercise price (in dollars per share)	$ 14.53	$ 6.23
Fair value of common stock (in dollars per share)	$ 14.53	$ 6.23
Expected term (in years)	6 years	6 years
Expected volatility	90.70%	92.40%
Risk-free rate	4.10%	3.60%
Dividend yield	0%	0%

Stock-Based Plans - Schedule of

Stock-Based Plans - Schedule of stock option activity (Details) - Stock options issued and outstanding $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2024 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares
Shares
Outstanding, beginning balance (in shares) | shares	2,878
Granted (in shares) | shares	1,682
Exercised (in shares) | shares	(106)
Forfeited and cancelled (in shares) | shares	(101)
Outstanding, ending balance (in shares) | shares	4,353	2,878
Exercisable at period end (in shares) | shares	1,260
Weighted- average exercise price per share
Outstanding, beginning balance (in dollars per share) | $ / shares	$ 4.48
Granted (in dollars per share) | $ / shares	14.51
Exercised (in dollars per share) | $ / shares	1.31
Forfeited and cancelled (in dollars per share) | $ / shares	6.11
Outstanding, ending balance (in dollars per share) | $ / shares	8.40	$ 4.48
Exercisable at period end (in dollars per share) | $ / shares	$ 4.13
Weighted – average remaining contractual term (in years)
Outstanding	8 years 4 months 24 days	8 years 8 months 12 days
Exercisable	7 years 2 months 12 days
Aggregate intrinsic value
Outstanding | $	$ 18,500	$ 7,794
Exercised | $	1,077
Exercisable | $	$ 9,435

Stock-Based Plans - Schedule _2

Stock-Based Plans - Schedule of activity related to RSUs (Details) - Restricted Stock Units (RSUs) shares in Thousands	9 Months Ended
	Sep. 30, 2024 $ / shares shares
Shares
Outstanding, beginning balance (in shares) | shares	0
Granted (in shares) | shares	54
Vested (in shares) | shares	0
Forfeited and cancelled (in shares) | shares	0
Outstanding, ending balance (in shares) | shares	54
Weighted-average grant date fair value per share
Outstanding, beginning balance (in dollars per share) | $ / shares	$ 0
Granted (in dollars per share) | $ / shares	14.88
Vested (in dollars per share) | $ / shares	0
Forfeited and cancelled (in dollars per share) | $ / shares	0
Outstanding, ending balance (in dollars per share) | $ / shares	$ 14.88

Stock-Based Plans - Schedule _3

Stock-Based Plans - Schedule of stock-based compensation expense (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]
Total stock-based compensation expense	$ 1,998	$ 541	$ 6,065	$ 2,285
Research and development
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	1,025	433	2,891	1,803
General and administrative
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 973	$ 108	$ 3,174	$ 482

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Thousands	Sep. 30, 2024 USD ($) termination	Sep. 11, 2024 USD ($)	May 29, 2024 USD ($) ft² renewal	Dec. 31, 2023 USD ($)
Lessee, Lease, Description [Line Items]
Square feet of office space | ft²			16,332
Term of lease			65 months
Total lease payments	$ 7,142		$ 7,100
Number of terminate | termination	1
Number of renewals | renewal			1
Renewal term			3 years
Payments over life of lease if option to terminate is taken			$ 4,100
Operating right-of-use asset	$ 5,225	$ 5,200		$ 0
Total operating lease liabilities	$ 5,332	$ 5,200
Letter of Credit
Lessee, Lease, Description [Line Items]
Letter of credit			$ 500

Leases - Schedule of lease cost

Leases - Schedule of lease cost (Details) $ in Thousands	3 Months Ended
	Sep. 30, 2024 USD ($)
Leases [Abstract]
Operating lease expense	$ 107
Variable lease expense	0
Total lease expense	$ 107

Leases - Schedule of Supplement

Leases - Schedule of Supplemental cash flow information (Details) $ in Thousands	3 Months Ended
	Sep. 30, 2024 USD ($)
Leases [Abstract]
Cash paid for amounts included in the measurement of lease liabilities	$ 0

Leases - Schedule of suppleme_2

Leases - Schedule of supplemental balance sheet information (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 11, 2024	Dec. 31, 2023
Leases [Abstract]
Operating right-of-use asset	$ 5,225	$ 5,200	$ 0
Operating lease liability—current portion (included in accrued expenses and other current liabilities)	716		125
Operating lease liability, long-term	4,616		$ 0
Total operating lease liabilities	$ 5,332	$ 5,200
Weighted average lease term (in years)	5 years 4 months 24 days
Weighted average discount rate	9.71%

Leases - Schedule of operating

Leases - Schedule of operating lease maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 11, 2024	May 29, 2024
Leases [Abstract]
For the year ending December 31, 2024	$ 76
2025	917
2026	1,216
2027	1,456
2028	1,500
Thereafter	1,977
Total lease payments	7,142		$ 7,100
Less: imputed interest	(1,810)
Present value of lease payments	$ 5,332	$ 5,200

Income Taxes (Details)

Income Taxes (Details)	9 Months Ended
	Sep. 30, 2024 USD ($)
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 0

Convertible Preferred Stock a_3

Convertible Preferred Stock and Stockholders’ Equity (Deficit) - Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended					3 Months Ended			9 Months Ended
	Feb. 29, 2024 $ / shares shares	Jan. 31, 2024 Rate	Jan. 31, 2023 USD ($) $ / shares Rate shares	Dec. 31, 2022 $ / shares shares	May 31, 2021 USD ($) $ / shares Rate shares	Sep. 30, 2024 USD ($) $ / shares shares	Mar. 31, 2024 shares	Sep. 30, 2023 USD ($) $ / shares	Sep. 30, 2024 USD ($) $ / shares shares	Sep. 30, 2023 USD ($) $ / shares	Feb. 06, 2024 $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares
Class of Stock [Line Items]
Preferred stock conversion, number of common stock (in shares)	13,664,261						29,919,000
Preferred stock, outstanding (in shares)						0			0
Preferred stock warrant liability | $						$ 0			$ 0			$ 1,352
Shares issued during period (in shares)	72,631
Number of shares called by warrants, multiplier				0.0375
Stock split, conversion ratio | Rate		44.62%	111.56%
Change in fair value of preferred stock warrant liability | $						$ 0		$ (226)	$ 243	$ (359)
Common stock, authorized (in shares)						500,000,000			500,000,000		500,000,000	52,000,000
Common stock, par value (in dollars per share) | $ / shares						$ 0.0001		$ 0.0001	$ 0.0001	$ 0.0001		$ 0.0001
Common stock, issued (in shares)						26,968,198			26,968,198			3,832,134
Common stock, outstanding (in shares)						26,968,198			26,968,198			3,832,134
Preferred stock, authorized (in shares)											10,000,000
Preferred stock, par value (in dollars per share) | $ / shares											$ 0.0001
Preferred stock, issued (in shares)						0			0
Series A Preferred Stock Warrants
Class of Stock [Line Items]
Warrant exercise price (in dollars per share) | $ / shares					$ 4.6996
Automatic exercise, threshold gross proceeds from stock sale, if circumstances met | $					$ 75,000
Automatic exercise, threshold price per share, if circumstances met (in dollars per share) | $ / shares					$ 15.68
Automatic exercise, share price multiplier | Rate					150%
Automatic exercise, threshold amount of unrestricted cash, if circumstances met | $					$ 75,000
Preferred stock warrant liability | $								$ 1,400		$ 1,400
K2 Warrant
Class of Stock [Line Items]
Warrant exercise price (in dollars per share) | $ / shares				$ 6								$ 4.7132
Convertible Preferred Stock (as if converted)
Class of Stock [Line Items]
Preferred stock, outstanding (in shares)	0
Series B Preferred
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)			4,166,667
Sale of stock, price per share (in dollars per share) | $ / shares			$ 6
Sale of stock, consideration received on transaction | $			$ 25,000
Stock split, conversion ratio				1.1156
Series B Preferred | K2 Warrant
Class of Stock [Line Items]
Number of shares called by warrants (in shares)				62,500
Series A Preferred | Series A Preferred Stock Warrants
Class of Stock [Line Items]
Number of shares called by warrants (in shares)					465,917
Series C Preferred | K2 Warrant
Class of Stock [Line Items]
Number of shares called by warrants (in shares)												79,564
Change in fair value of preferred stock warrant liability | $									$ 200
Common Stock | K2 Warrant
Class of Stock [Line Items]
Warrant exercise price (in dollars per share) | $ / shares	$ 10.49
Number of warrants or rights outstanding (in shares)	35,773

Convertible Preferred Stock a_4

Convertible Preferred Stock and Stockholders’ Equity (Deficit) - Schedule of convertible preferred stock (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Class of Stock [Line Items]
Shares authorized (in shares)				31,512,000
Shares issued (in shares)				29,919,000
Shares outstanding (in shares)	0	0	0	29,919,000	20,371,000	20,371,000	20,371,000	16,204,000
Carrying Value	$ 0	$ 0	$ 0	$ 141,477	$ 97,081	$ 97,081	$ 97,081	$ 72,235
Liquidation Preference				$ 146,704
Series Seed Preferred
Class of Stock [Line Items]
Shares authorized (in shares)				3,709,000
Shares issued (in shares)				3,709,000
Shares outstanding (in shares)				3,709,000
Carrying Value				$ 7,674
Liquidation Preference				$ 7,722
Series A Preferred
Class of Stock [Line Items]
Shares authorized (in shares)				7,251,000
Shares issued (in shares)				6,785,000
Shares outstanding (in shares)				6,785,000
Carrying Value				$ 30,489
Liquidation Preference				$ 31,887
Series B Preferred
Class of Stock [Line Items]
Shares authorized (in shares)				9,877,000
Shares issued (in shares)				9,877,000
Shares outstanding (in shares)				9,877,000
Carrying Value				$ 58,918
Liquidation Preference				$ 62,095
Series C Preferred
Class of Stock [Line Items]
Shares authorized (in shares)				10,675,000
Shares issued (in shares)				9,548,000
Shares outstanding (in shares)				9,548,000
Carrying Value				$ 44,396
Liquidation Preference				$ 45,000

Convertible Preferred Stock a_5

Convertible Preferred Stock and Stockholders’ Equity (Deficit) - Change in fair value of the preferred stock warrant liability (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	8 Months Ended
	Feb. 02, 2024	Mar. 31, 2024	Sep. 30, 2024
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reclassification to equity		$ (1,595)
Preferred Stock Warrants
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 1,352	$ 1,352	$ 1,595
Issuance of Preferred Stock Warrants	0
Exercise	0
Expiration	0
Change in fair value	243
Balance at February 2, 2024	1,595		0
Reclassification to equity			(1,595)
Ending balance	$ 1,595		$ 0

Convertible Preferred Stock a_6

Convertible Preferred Stock and Stockholders’ Equity (Deficit) - Schedule of stock reserved for issuance (Details) - shares	Sep. 30, 2024	Dec. 31, 2023
Class of Stock [Line Items]
Reserved common stock on an as-if converted basis (in shares)	5,263,000	17,632,000
Stock options issued and outstanding
Class of Stock [Line Items]
Reserved common stock on an as-if converted basis (in shares)	4,946,000	3,471,000
Stock options available for future grant
Class of Stock [Line Items]
Reserved common stock on an as-if converted basis (in shares)	281,000	251,000
Series Seed Preferred
Class of Stock [Line Items]
Reserved common stock on an as-if converted basis (in shares)	0	1,668,000
Series A Preferred
Class of Stock [Line Items]
Reserved common stock on an as-if converted basis (in shares)	0	3,051,000
Series B Preferred
Class of Stock [Line Items]
Reserved common stock on an as-if converted basis (in shares)	0	4,653,000
Series C Preferred
Class of Stock [Line Items]
Reserved common stock on an as-if converted basis (in shares)	0	4,293,000
Series A Preferred Stock Warrants
Class of Stock [Line Items]
Reserved common stock on an as-if converted basis (in shares)	0	209,000
K2 Warrant
Class of Stock [Line Items]
Reserved common stock on an as-if converted basis (in shares)	36,000	36,000

Loss Per Share (Details)

Loss Per Share (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	5,036	11,965
Convertible Preferred Stock (as if converted)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	9,159
Preferred Stock Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	238
Common Stock Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	36	0
Restricted Stock Units and Award
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	54	34
Stock options issued and outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	4,946	2,534

Retirement Plan (Details)

Retirement Plan (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Retirement Benefits [Abstract]
Employer matching contribution, percent of employees' gross pay			3%
Defined contribution plan, cost (less than for the quarters ended September 30, 2024 and 2023)	$ 0.1	$ 0.1	$ 0.3	$ 0.2