0001962918-24-000128 | 10-Q | XBRL Viewer

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Significant Agreements	9 Months Ended
Significant Agreements	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Significant Agreements	Significant Agreements Affibody License and Collaboration Agreement On August 9, 2021, the Company entered into a license agreement with Affibody AB (“Affibody”) (the “Affibody Agreement”) under which Affibody granted the Company exclusive, sublicensable licenses to develop, commercialize and manufacture products containing izokibep for all human therapeutic uses on a worldwide basis, subject to a pre-existing agreement with Inmagene Biopharmaceuticals (“Inmagene”) with respect to certain Asian countries. The Company chairs a global joint steering committee composed of designees from Affibody, Inmagene and the Company and retains final decision-making authority for izokibep global development. In doing so, the Company is obligated to use commercially reasonable efforts (i) to develop products containing izokibep worldwide, excluding certain defined territories, (ii) for the conduct and finalization of certain ongoing clinical trials, and (iii) to commercialize products containing izokibep for all human therapeutic uses worldwide, excluding certain defined territories, after obtaining the applicable marketing authorization. The Company is responsible for manufacturing both the clinical and commercial supply of licensed product globally. In connection with the Affibody Agreement, the Company paid a non-refundable upfront license fee in the aggregate amount of $3.0 million in August 2021 and September 2021, and $22.0 million in October 2021. The Company is also obligated to pay Affibody (i) an aggregate of up to $280.0 million, $30.0 million of which would be due prior to the first approval in the United States, upon the achievement of various development, regulatory and commercialization milestones, $15.0 million of which was paid in November 2023 and (ii) high single-digit to low-teens royalties on net sales of licensed products in the territory where the Company has commercialization rights, subject to certain reductions. Royalties will be due on a licensed product-by-licensed product and country-by-country basis beginning after the first commercial sale of the licensed product, except in Mainland China, Hong Kong, Macau, Taiwan and South Korea, and lasting until the later of (a) the expiration of all valid patent claims or regulatory exclusivity covering the licensed product in that country and (b) ten years after such first commercial sale. In the event the U.S. Food and Drug Administration (“FDA”) grants the Company (or its affiliates or sublicensees) a priority review voucher for a licensed product, the Company will pay Affibody either: (a) if the Company sells or transfer such priority review voucher to a third-party, approximately one third of the proceeds received from the sale, net of taxes, or (b) if the Company uses the priority review voucher for an indication or product outside the scope of the Affibody Agreement, approximately one third of the fair market value of the priority review voucher as determined in accordance with the Affibody Agreement. Unless earlier terminated, the Affibody Agreement will continue on a licensed product-by-licensed product basis and country-by-country basis until there are no more royalty payments owed to Affibody on any licensed product thereunder. The acquisition of the exclusive license was accounted for as an in-process research and development asset acquisition and as the acquired technology did not have an alternative use, the total consideration of $25.0 million was recorded as research and development expense in the consolidated statements of operations and comprehensive loss for the year ended December 31, 2021. Milestone payments are contingent consideration and are accrued when contingent events occur and achievement of milestones is probable. In November 2023, the Company paid a total amount of $15.0 million in relation with attaining one of the development milestones described above and recorded the payment within research and development expenses in the consolidated statement of operations and comprehensive loss for the year ended December 31, 2023. Royalties will be recognized as cost of sales when products are sold and royalties are payable. No royalties or additional milestones were probable and estimable as of September 30, 2024 and December 31, 2023. Pierre Fabre License and Commercialization Agreement Upon the closing of the Acquisition, the Company became the successor to ValenzaBio’s rights under the March 25, 2021 license and commercialization agreement between ValenzaBio and Pierre Fabre, as amended (the “Pierre Fabre Agreement”). The Company received certain exclusive worldwide licenses with the right to sublicense to certain patents, know-how and other intellectual property to develop, manufacture, use and commercialize lonigutamab for non-oncology therapeutic indications. The license from Pierre Fabre extends to any product containing lonigutamab (excluding any fragments or derivatives) as its sole active ingredient (each, a “PF Licensed Product”). The Pierre Fabre Agreement prohibits the Company from using the licensed intellectual property in any antibody drug conjugate, multi-specific antibodies or any other derivatives of lonigutamab. In the event the Company decides to sublicense the rights to develop or commercialize a PF Licensed Product in any territory outside of the United States and Canada, Pierre Fabre retains the right of first negotiation to acquire such development and commercialization rights in one or more countries in such territory. Subject to the validation of certain clinical trial criteria by a joint steering committee, Pierre Fabre has the option to reclaim all exclusive rights to develop, commercialize and exploit the PF Licensed Product in such territories and to obtain an exclusive sublicensable license in such territories for any improvements and trademarks to such PF Licensed Product, and to exploit such PF Licensed Product for non-oncology therapeutic indications, subject to certain payment obligations. The joint steering committee validated such clinical trial criteria in May 2024, triggering the commencement of the option period in October 2024. In October 2024, Pierre Fabre exercised its option under the Pierre Fabre Agreement, requiring the Company to buy out its right to the option for a one-time payment of $31.0 million. The Company will recognize the option exercise expense in the Condensed Consolidated Statement of Operations and Comprehensive Loss in the period ended December 31, 2024, the period in which the obligation was incurred. As consideration for the amendment to the Pierre Fabre Agreement, which became effective upon the closing of the Acquisition (see Note 3), the Company paid Pierre Fabre an aggregate license payment of $10.0 million. The Company is also obligated to (i) make payments of up to $99.5 million upon the achievement of various development and regulatory milestones, (ii) make milestone payments of up to $390.0 million upon the achievement of certain commercial milestones, and (iii) pay tiered royalties in the high single-digit to low-teen percentages to Pierre Fabre on worldwide net sales in a given calendar year. Royalties will be payable for each PF Licensed Product in a given country during a period commencing upon the first commercial sale of such PF Licensed Product in such country and continuing until the latest of (a) 10 years after such first commercial sale, (b) expiration of last-to-expire valid claim in a licensed patent in such country and (c) expiration of regulatory exclusivity for such PF Licensed Product in such country. In the event the Company enters into a sublicense with a third party, the Company must also share with Pierre Fabre a percentage of any revenues from option fees, upfront payments, license maintenance fees, milestone payments or the like generated from the sublicense. Such percentage may be between the high single-digits to the low thirties based on which stage of development of a PF Licensed Product the sublicense relates to. Unless earlier terminated, the Pierre Fabre Agreement will continue on a PF Licensed Product-by-PF Licensed Product and country-by-country basis until there are no more royalty payments owed to Pierre Fabre on any PF Licensed Product thereunder. Either party may terminate the Pierre Fabre Agreement upon an uncured material breach, or upon the bankruptcy or insolvency of the other party. Pierre Fabre may also terminate the agreement if the Company or any of its affiliates institutes a patent challenge against the licensed patents from Pierre Fabre. The Company may also terminate the Pierre Fabre Agreement with or without cause upon nine months’ prior written notice, so long as there is no ongoing clinical trial for any PF Licensed Product. As of September 30, 2024, no milestones were probable and accrued in the condensed consolidated balance sheet. Novelty Nobility License and Commercialization Agreement Upon the closing of the Acquisition, the Company became the successor to an exclusive license agreement between ValenzaBio and Novelty Nobility (the “Novelty License Agreement”) and obtained a worldwide exclusive license for the development and commercialization of SLRN-517, an unmodified IgG1 monoclonal antibody, as a therapeutic treatment. In connection with the arrangement, the Company is obligated to (i) make development and regulatory milestones of up to $44.3 million, (ii) make commercial sales milestone payments of up to $682.0 million and (iii) pay tiered royalties of a low single-digit to high-single-digit percentage on future worldwide net sales. The Novelty License Agreement is effective on a licensed product-by-licensed product and country-by-country basis until the expiration of the latest to expire royalty term, unless early terminated. The royalty term, with respect to a licensed product and a country is the period commencing on the first commercial sale of such product in such country, and ending upon the latest to occur of: a) there being no patent right in such country that had at least one valid claim covering the licensed product in whole or in part, or the manufacture or use thereof; b) 10 years from the first commercial sale of such product worldwide; or c) expiration of regulatory exclusivity for such product in such country. The agreement can be early terminated upon (i) a material breach, (ii) abandonment of development by the Company, in which the Company ceases all development activities for the licensed product, (iii) termination by patent challenge, and (iv) insolvency. The Company may terminate the contract at any point, upon 30 days prior written notice to Novelty Nobility, Inc. As of September 30, 2024, no milestones were probable and accrued in the condensed consolidated balance sheet.

Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2024
Accounting Policies [Abstract]
Basis of Presentation	The condensed consolidated financial statements and accompanying notes are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the SEC regarding interim financial reporting. The accompanying financial statements are consolidated and include the accounts of ACELRYIN, INC. and its wholly owned subsidiary, WH2, LLC. The subsidiary has not had any operations or any balances from its inception. Certain information and footnote disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2023 included in the Company’s Annual Report. The information as of December 31, 2023 included in the condensed consolidated balance sheets was derived from the Company’s audited consolidated financial statements. These unaudited interim condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments necessary for a fair statement of the Company’s consolidated financial statements. The results of operations for the three and nine months ended September 30, 2024 are not necessarily indicative of the results that may be expected for the year ending December 31, 2024 or for any other interim period or for any other future year.
Use of Estimates	The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates estimates and assumptions, including but not limited to those related to the fair value of its derivative tranche liability, the fair value of its common stock, stock-based compensation expense, accruals for research and development expenses, valuation of deferred tax assets, and uncertain income tax positions. Management bases its estimates on historical experience and on various other assumptions that are 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 that are not readily apparent from other sources. Actual results may differ materially from those estimates.
Concentration of Credit Risk	Cash, cash equivalents, restricted cash and short-term marketable securities are financial instruments that potentially subject the Company to concentrations of credit risk. As of September 30, 2024 and December 31, 2023, cash consists of cash deposited with one financial institution, and account balances exceed federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial strength of this institution. The Company also has investments in money market funds, U.S. Treasury obligations, corporate debt obligations, and federal agency obligations, which can be subject to certain credit risks. The Company mitigates the risks by investing in high-grade instruments, limiting its exposure to any one issuer and monitoring the ongoing creditworthiness of the financial institutions and issuers. The Company has not experienced any losses on its financial instruments.
Restructuring	The Company accounts for exit or disposals costs in accordance with ASC 420, Exit or Disposal Cost Obligations. Charges represent expenses incurred in connection with certain exit or disposal activities and consist of the costs of contract termination, employee termination and other activities. A liability for costs associated with an exit or disposal activity is measured at its fair value when the liability is incurred.
Long-lived Assets Impairment Assessment	Long-lived assets, including operating lease assets, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. The recoverability of assets to be held and used is measured by a comparison of the carrying amount of the asset group to future net cash flows estimated by the Company to be generated by such assets. If such asset group is considered to be impaired, the impairment to be recognized is the amount by which the carrying amount of the asset group exceeds the fair value of the asset group. During the three months ended September 30, 2024, the Company performed an evaluation of the impact of the August 2024 Restructuring Plan on the carrying value of its long-lived assets and concluded that there was no impairment charge to be recognized on the long-lived assets.
Fair Value Measurements	The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1 — Quoted prices in active markets for identical assets or liabilities. Level 2 — Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The Company’s financial instruments measured at fair value on a recurring basis consist of Level 1, Level 2, and Level 3 financial instruments. Usually, short term marketable securities are considered Level 2 when their fair values are determined using inputs that are observable in the market or can be derived principally from or corroborated by observable market data such as pricing for similar securities, recently executed transactions, cash flow models with yield curves, and benchmark securities. In addition, Level 2 financial instruments are valued using comparisons to like-kind financial instruments and models that use readily observable market data as their basis. Corporate debt obligations, commercial paper, government agency obligations and asset-backed securities are valued primarily using market prices of comparable securities, bid/ask quotes, interest rate yields and prepayment spreads and are included in Level 2. Financial assets and liabilities are considered Level 3 when their fair values are determined using pricing models, discounted cash flow methodologies, or similar techniques, and at least one significant model assumption or input is unobservable.

Equity Incentive Plan - Narrative (Details) - USD ($)				1 Months Ended				3 Months Ended		9 Months Ended		12 Months Ended
Equity Incentive Plan - Narrative (Details) - USD ($)	Jan. 01, 2024	May 04, 2023	Jan. 04, 2023	May 31, 2024	Aug. 31, 2023	Apr. 30, 2023	Jul. 31, 2020	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]
Total shares reserved for future issuance (in shares)								23,894,919		23,894,919		20,101,379
Common stock, issued (in shares)								99,944,302		99,944,302		97,865,890
Common stock, outstanding (in shares)								99,944,302		99,944,302		97,865,890
Share-based and cash-based compensation, maximum		$ 750,000
Fair value of shares vested								$ 5,300,000		$ 18,100,000
Weighted-average grant date fair value, grants in period (in dollars per share)								$ 3.51		$ 3.80
Options granted (in shares)										9,773,227
Exercisable (in dollars per share)								$ 9.9887		$ 9.9887
Exercises in period (in shares)										511,255
Options expired (in dollars per share)										$ 7.1906
Total stock-based compensation expense								$ 7,054,000	$ 15,313,000	$ 37,391,000	$ 30,953,000
Expected dividend yield								0.00%	0.00%	0.00%	0.00%
Issuance of common stock under the employee stock purchase plan (in shares)								0		100,827
Research and Development Expense
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense								$ 2,640,000	$ 3,572,000	$ 12,081,000	$ 8,661,000
General and Administrative Expense
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense								$ 4,414,000	11,741,000	$ 25,310,000	22,292,000
Share-Based Payment Arrangement, Nonemployee
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-based and cash-based compensation, maximum		$ 1,000,000
Stock options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)								14,071,995		14,071,995		9,630,623
Expiration period												10 years
Total stock-based compensation expense								$ 6,324,000	8,577,000	$ 25,188,000	18,661,000
Employee Stock
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)								1,753,667		1,753,667		875,836
Additional shares authorized (in shares)	978,658
Purchase price of common stock						85.00%
Number of shares authorized (in shares)						900,000
Percentage of eligible compensation for payroll deductions to purchase stock						15.00%
Purchase period						6 months
Annual increase, period						10 years
Annual increase as percentage of shares outstanding						1.00%
Maximum number of shares available over award term						2,700,000
Total stock-based compensation expense								$ 53,000	126,000	$ 232,000	143,000
Deferred compensation share-based arrangements, liability, current								$ 200,000		$ 200,000
Performance Shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)								792,908		792,908		2,964,072
Expiration period										3 years
Total stock-based compensation expense								$ (941,000)	4,265,000	$ (2,739,000)	4,265,000
Target number of shares (in shares)					3,135,104
Target number of shares, percentage					150.00%
Share price (in usd per share)								$ 26.97		$ 26.97
Expected volatility										87.71%
Risk-free interest rate										4.47%
Expected dividend yield										0.00%
Granted (in dollars per share)												$ 27.43
Share-based payment arrangement, reversal of expense				$ (13,400,000)				$ 900,000
Weighted-average recognition period										1 year 3 months 18 days
Unrecognized stock-based compensation expense								10,100,000		$ 10,100,000
Unrecognized stock-based compensation expense, maximum								12,600,000		12,600,000
Performance Shares and Performance Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-based payment arrangement, reversal of expense								$ (13,500,000)		$ (13,500,000)
Unvested RSUs outstanding
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)								1,204,470		1,204,470		2,166,016
Total stock-based compensation expense								$ 1,618,000	$ 2,345,000	$ 14,857,000	7,884,000
Granted (in dollars per share)										$ 6.56
Share-based payment arrangement, accelerated and plan modification, cost										$ 12,700,000
Restricted Stock [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period							48 months
Equity Incentive Plan 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)		12,000,000
Percentage of outstanding stock maximum		5.00%
Vesting period		4 years
Equity Incentive Plan 2023 \| Stock options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Additional shares authorized (in shares)	5,230,473
Shares issuable (in shares)		56,762,538
Equity Incentive Plan 2023 \| Stock options \| Stockholder, 10% Or More
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expiration period		5 years
Equity Incentive Plan 2023 \| Stock options \| Minimum \| Stockholder, 10% Or More
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Purchase price of common stock		110.00%
2020 Equity Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock, issued (in shares)		6,920,846
Common stock, outstanding (in shares)		6,920,846
Shares available for future grants under Equity Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)								6,016,568		6,016,568		3,526,392
2020 Stock Option Plan \| Stock options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expiration period										10 years
Vesting period										4 years
ValenaBio 2020 Stock Option Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Options granted (in shares)			1,249,811
Exercisable (in dollars per share)			$ 3.6736
Exercises in period (in shares)								2,000		883,129
Options expired (in dollars per share)								$ 4.2891		$ 4.0538
Unrecognized stock-based compensation expense								$ 50,900,000		$ 50,900,000
ValenaBio 2020 Stock Option Plan \| ValenzaBio Asset Acquisition
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense											4,900,000
ValenaBio 2020 Stock Option Plan \| ValenzaBio Asset Acquisition \| Research and Development Expense
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense											3,100,000
ValenaBio 2020 Stock Option Plan \| ValenzaBio Asset Acquisition \| General and Administrative Expense
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense											1,800,000
ValenaBio 2020 Stock Option Plan \| Stock options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)								55,311		55,311		938,440
Weighted-average recognition period										1 year 6 months
ValenaBio 2020 Stock Option Plan \| Stock options \| ValenzaBio Asset Acquisition
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense											4,900,000
ValenaBio 2020 Stock Option Plan \| Unvested RSUs outstanding
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Weighted-average recognition period										1 year 8 months 12 days
Unrecognized stock-based compensation expense								$ 12,500,000		$ 12,500,000
ValenaBio 2020 Stock Option Plan \| Restricted Stock [Member] \| ValenzaBio Asset Acquisition
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense											$ 900,000

Net Loss Per Share Attributable to Common Stockholders - Schedule of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Numerator:
Net loss	$ (48,548)	$ (85,672)	$ (34,973)	$ (83,940)	$ (26,039)	$ (176,450)	$ (169,193)	$ (286,429)
Denominator:
Weighted average common shares outstanding (in shares)	99,835,707			97,227,070			99,050,167	61,580,296
Less: Weighted-average common shares subject to repurchase (in shares)	0			(354,323)			(76,649)	(442,191)
Weighted-average common shares outstanding, basic (in shares)	99,835,707			96,872,747			98,973,518	61,138,105
Weighted-average common shares outstanding, diluted (in shares)	99,835,707			96,872,747			98,973,518	61,138,105
Net loss per share attributable to common stockholder, basic (in shares)	$ (0.49)			$ (0.87)			$ (1.71)	$ (4.68)
Net loss per share attributable to common stockholder, diluted (in shares)	$ (0.49)			$ (0.87)			$ (1.71)	$ (4.68)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

+ Details

- Definition

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

+ References

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+ Details

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders’ Equity (Deficit) (Parenthetical) $ in Thousands	3 Months Ended
	Jun. 30, 2023 USD ($)
Statement of Stockholders' Equity [Abstract]
Underwriting discounts, commissions and offering costs	$ 47,354

Restructuring

9 Months Ended

Sep. 30, 2024

Restructuring and Related Activities [Abstract]

Restructuring

On August 10, 2024, the Company’s Board of Directors approved a plan to suspend new internal investment in the development of izokibep in hidradenitis suppurativa (“HS”), psoriatic arthritis (“PsA”) and axial spondyloarthritis (“AxSpA”), pursuant to which the Company is focusing its efforts primarily on its lonigutamab clinical program in thyroid eye disease (“TED”) and implemented an associated workforce reduction (the “Restructuring Plan”). As part of the Restructuring Plan, the Company’s workforce will ultimately be reduced by 40 people, or approximately 1/3 of the Company’s then-existing headcount.

In connection with the workforce reduction, the Company estimates it will incur restructuring charges totaling approximately $4.3 million in cash-based expenses related to one-time employee severance payments and benefits, of which it has recognized $3.6 million for the three months ended September 30, 2024. The remaining restructuring charges related to the workforce reduction will be substantially complete by the end of the fourth quarter of 2024. Remaining employee severance payments and benefits of $1.6 million are included in restructuring liabilities in the condensed consolidated balance sheet for the period ended September 30, 2024.

In the third quarter of 2024, the Company and a vendor entered into an agreement to cancel certain services under a manufacturing agreement related to the suspension of new internal development of izokibep in HS, PsA and AxSpA. All post-cancellation obligations are expected to be settled in the fourth quarter of 2024 and the first quarter of 2025. The Company incurred net restructuring charges of $7.2 million consisting of $42.9 million of expense in connection with such cancellation of services netted against $35.7 million credit voucher to be issued as part of the agreement to cancel services upon payment of the amounts due to the manufacturer, and recognized those costs (calculated using the average applicable exchange rate for the month of September 2024) in the quarter ended September 30, 2024, the period in which the obligation was incurred. The credit voucher is expected to be used by the Company in 2025 and the first quarter of 2026 to offset cash obligations for manufacturing costs under such manufacturing agreement as well as manufacturing services for the lonigutamab program.

For the three and nine months ended September 30, 2024, the Company recognized total restructuring charges of $10.8 million. Restructuring costs were included in restructuring in the condensed consolidated statement of operations and comprehensive loss for the quarter ended September 30, 2024.

The following table summarizes the change in the Company’s restructuring liabilities for the nine months ended September 30, 2024 (in thousands):


	Severance and other employee-related benefits		Service cancellation costs		Total
Balance at December 31, 2023	$	—	$	—	$	—
Restructuring charges	$	3,586	$	42,896	$	46,482
Cash payments	$	(1,974)	$	—	$	(1,974)
Revaluation	$	—	$	128	$	128
Balance at September 30, 2024	$	1,612	$	43,024	$	44,636

Equity Incentive Plan - Schedule of Stock Option Activity (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2024 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares
Number of Options
Outstanding, beginning balance (in shares) \| shares	9,630,623
Options granted (in shares) \| shares	9,773,227
Options exercised (in shares) \| shares	(511,255)
Options expired (in shares) \| shares	(128,091)
Options forfeited (in shares) \| shares	(4,692,509)
Outstanding, ending balance (in shares) \| shares	14,071,995	9,630,623
Exercisable (in shares) \| shares	3,812,458
Vested and expected to vest (in shares) \| shares	14,071,995
Weighted-Average Exercise Price Per Share
Outstanding, beginning balance (in dollars per share) \| $ / shares	$ 10.4619
Granted (in dollars per share) \| $ / shares	6.3274
Options exercised (in dollars per share) \| $ / shares	2.9748
Options expired (in dollars per share) \| $ / shares	7.1906
Options forfeited (in dollars per share) \| $ / shares	9.7232
Outstanding, ending balance (in dollars per share) \| $ / shares	8.1385	$ 10.4619
Exercisable (in dollars per share) \| $ / shares	9.9887
Vested and expected to vest (in dollars per share) \| $ / shares	$ 8.1385
Weighted-Average Remaining Contractual Term
Outstanding	8 years	9 years
Exercisable	4 years 8 months 12 days
Vested and expected to vest	8 years
Aggregate Intrinsic Value
Outstanding \| $	$ 3,829	$ 12,007
Exercisable \| $	1,094
Vested and expected to vest \| $	$ 3,829

Description of Business, Organization and Liquidity (Details) $ / shares in Units, $ in Thousands				3 Months Ended						9 Months Ended
	May 09, 2023 USD ($) $ / shares shares	Apr. 25, 2023	Jan. 04, 2023 USD ($) shares	Sep. 30, 2024 USD ($)	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Jul. 31, 2020 $ / shares
Subsidiary, Sale of Stock [Line Items]
Reverse stock split, conversion ratio		0.5071
Sale of stock, price (in dollars per share) \| $ / shares													$ 0.00002
Underwriting discounts, commissions and offering costs								$ 47,354
Temporary equity, convertible, conversion ratio				100.00%						100.00%
Net losses				$ 48,548	$ 85,672	$ 34,973	$ 83,940	$ 26,039	$ 176,450	$ 169,193	$ 286,429
Other nonoperating income						$ 37,000
Research and development				31,612			$ 74,562			166,026	272,512
Payments to acquire in-process research and development										0	10,000
Accumulated deficit				657,912						657,912		$ 488,719
Cash used in operating activities										182,338	96,074
Cash, cash equivalents, and marketable securities				$ 562,900						$ 562,900
Pierre Fabre
Subsidiary, Sale of Stock [Line Items]
Payments to acquire in-process research and development			$ 10,000								10,000
ValenzaBio Asset Acquisition
Subsidiary, Sale of Stock [Line Items]
Shares issued (in shares) \| shares			2,013,673
Research and development			$ 123,100								$ 123,100
ValenzaBio Asset Acquisition \| Common Class A
Subsidiary, Sale of Stock [Line Items]
Shares issued (in shares) \| shares			18,885,731
IPO
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in transaction (in shares) \| shares	34,500,000
Sale of stock, price (in dollars per share) \| $ / shares	$ 18.00
Gross proceeds received on transaction	$ 621,000
Net proceeds received on transaction	573,600
Underwriting discounts, commissions and offering costs	$ 47,400
Over-Allotment Option
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in transaction (in shares) \| shares	4,500,000

Restructuring - Schedule of Restructuring Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance		$ 0
Restructuring charges		46,482
Cash payments		(1,974)
Revaluation		128
Restructuring reserve, ending balance	$ 44,636	44,636
Severance and other employee-related benefits
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance		0
Restructuring charges	3,600	3,586
Cash payments		(1,974)
Revaluation		0
Restructuring reserve, ending balance	1,612	1,612
Service cancellation costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance		0
Restructuring charges	42,900	42,896
Cash payments		0
Revaluation		128
Restructuring reserve, ending balance	$ 43,024	$ 43,024

Equity Incentive Plan

9 Months Ended

Sep. 30, 2024

Share-Based Payment Arrangement [Abstract]

Equity Incentive Plan

In April 2023, the Company’s board of directors adopted, and stockholders approved, the 2023 Equity Incentive Plan (the “2023 Plan”) that became effective on May 4, 2023. The Company reserved 12,000,000 new shares of common stock for issuance under the 2023 Plan. In addition, 6,920,846 shares issued and outstanding under the Company’s 2020 Equity Incentive Plan, as amended (the “2020 Plan”), have been added to the 2023 Plan as such shares become available from time to time if awards terminate, expire, or lapse for any reason without the delivery of shares, or are reacquired or withheld (or not issued) to satisfy a tax withholding obligation or the purchase or exercise price. The 2023 Plan also provides that the number of shares initially reserved and available for issuance will automatically increase each January 1, beginning on January 1, 2024 and ending on January 1, 2033, by an amount equal to the lesser of (i) 5% of the shares of common stock outstanding on the last day of the immediately preceding fiscal year, and (ii) such smaller number of shares of stock as determined by the Company’s board of directors. On January 1, 2024, 5,230,473 additional shares of common stock became available for issuance under the 2023 Plan pursuant to the provision. No more than 56,762,538 shares of stock may be issued upon the exercise of incentive stock options under the 2023 Plan. The Company may grant incentive stock options, nonstatutory stock options (“NSOs”), restricted stock units (“RSUs”), restricted stock awards (“RSAs”), stock appreciation rights (“SARs”), performance awards and other awards to the Company’s officers, employees, directors and consultants. Options under the 2023 Plan may be granted for periods of up to 10 years at exercise prices no less than the fair market value of the common stock on the date of grant and usually vest over four years. The exercise price of an option granted to a 10% stockholder may not be less than 110% of the fair market value of the shares on the date of grant

and such option may not be exercisable after the expiration of five years from the date of grant. The grant date fair market value of all awards made under our 2023 Plan and all cash compensation paid by us to any non-employee director for services as a director in any fiscal year may not exceed $750,000, increased to $1,000,000 in the fiscal year of their initial service as a non-employee director. The 2023 Plan is the successor to and continuation of the 2020 Plan and no additional awards may be granted under the 2020 Plan. All outstanding awards granted under the 2020 Plan will remain subject to the terms of the 2020 Plan. The 2020 Plan provided for the grant of incentive stock options, nonstatutory stock options, RSUs and RSAs to the Company’s officers, employees, directors and consultants. As of September 30, 2024 and December 31, 2023, 6,016,568 and 3,526,392 shares of the Company’s common stock remained available for issuance under the 2023 Plan.

In April 2023, the Company’s board of directors and stockholders adopted the 2023 Employee Stock Purchase Plan (the “ESPP”), which became effective on May 4, 2023. The ESPP authorized issuance of up to 900,000 shares of common stock. The ESPP permits participants to purchase common stock through payroll deductions of up to 15% of their eligible compensation. Employees purchase shares of common stock at a price per share equal to 85% of the lower of the fair market value at the start or end of six-month purchase and offering consecutive periods. The aggregate number of shares reserved for sale under the 2023 ESPP will increase automatically on January 1 for a period of up to 10 calendar years, commencing on January 1, 2024, by the number of shares equal to the lesser of 1% of the Company's total outstanding shares of common stock on the immediately preceding December 31st, and 2,700,000 shares or a lesser number of shares as may be determined by the board of directors. On January 1, 2024, the Company registered 978,658 additional shares of its Common Stock under the ESPP pursuant to the provision. There were 1,753,667 and 875,836 ESPP shares available for future grants as of September 30, 2024 and December 31, 2023, respectively.

Stock Options

Stock options issued under the 2020 and 2023 Plan generally vest over a four-year period and expire ten years from the date of grant. Certain options provide for accelerated vesting if there is a change in control, as defined in the individual award agreements.

A summary of option activity under the 2020 and 2023 Plan is as follows:


	Number of Options	Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2023	9,630,623	$	10.4619	9.0	$	12,007
Options granted	9,773,227	6.3274
Options exercised	(511,255)	2.9748
Options expired	(128,091)	7.1906
Options forfeited	(4,692,509)	9.7232
Outstanding at September 30, 2024	14,071,995	$	8.1385	8.0	$	3,829
Exercisable at September 30, 2024	3,812,458	$	9.9887	4.7	$	1,094
Vested and expected to vest at September 30, 2024	14,071,995	$	8.1385	8.0	$	3,829

The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying stock options and the estimated fair value of the Company’s common stock for those stock options that had exercise prices lower than the estimated fair value of the Company’s common stock at September 30, 2024 and December 31, 2023. The fair value of shares vested during the three months ended September 30, 2024 was $5.3 million. The weighted-average grant date fair value of options granted in three months ended September 30, 2024 was $3.51 per share. Fair value of shares vested during the nine months ended September 30, 2024 was $18.1 million. The weighted-average grant date fair value of options granted in nine months ended September 30, 2024 was $3.80 per share.

ValenzaBio 2020 Stock Option Plan

On January 4, 2023, in connection with the Acquisition, the Company assumed the ValenzaBio 2020 Stock Option Plan and options to issue 1,249,811 shares of the Company’s Class A Common Stock to ValenzaBio option holders,

who entered into consulting agreements with the Company. The weighted-average exercise price of assumed options was $3.6736 per share.

Under the terms of the Merger Agreement, the assumed options vested in full on March 31, 2023. A total of 2,000 and 883,129 options assumed under the ValenzaBio 2020 Stock Option Plan having the weighted-average exercise price of $4.2891 and $4.0538 per share were exercised for the three and nine months ended September 30, 2024, respectively.

The Company recognized the full amount of stock-based compensation expense of $4.9 million, including $3.1 million as research and development expenses and $1.8 million as general administrative expenses, related to assumed options in the consolidated statement of operations for the nine months ended September 30, 2023.

Restricted Stock Units

A summary of unvested RSU activity is presented in the following table:


	Number of RSUs	Weighted-Average Grant Date Fair Value
Unvested at December 31, 2023	2,166,016	$	22.90
Granted	2,171,896	6.56
Vested	(1,019,894)	9.36
Forfeited	(2,113,548)	18.23
Unvested at September 30, 2024	1,204,470	$	13.09

Performance-Based Restricted Stock Units

In August 2023, the Company granted PSUs to certain employees and officers of the Company. The PSUs may vest over several years subject to the achievement of (i) certain clinical development milestones over a performance period from the grant date to May 2027 (the “Performance Period”) or (ii) market conditions (i.e., stock price hurdle) based on pre-specified volume-weighted average stock price measurements as of each vesting performance measurement date, and continued employment with the Company through the applicable vesting date(s). The target number of shares under the PSUs at the grant date was 3,135,104. The ultimate number of PSU shares that may vest, in the aggregate over the Performance Period could, in certain cases, be up to 150% of the target number of shares upon the achievement of certain market or performance conditions.

A summary of PSU activity based on the target number of shares is presented in the following table:


	Number of PSUs	Weighted-Average Grant Date Fair Value*
Outstanding at December 31, 2023	2,964,072	$	27.43
Granted	—
Vested	—
Forfeited	(2,171,164)	27.43
Outstanding at September 30, 2024	792,908	$	27.43

*The grant date fair value is based only on the PSUs with market conditions and does not factor in any performance conditions.

As the PSUs granted in 2023 are subject to a market condition, the grant date fair value for such PSUs was based on a Monte Carlo simulation model. The Company estimated the fair value of PSUs based on the grant date price of its common stock of $26.97 and the following assumptions: expected volatility of 87.71%, risk-free-rate of 4.47%, and zero expected dividend yield. In 2023, the Company granted PSUs to employees with a weighted-average grant date fair value of $27.43. The unvested awards will expire if it is determined that the vesting conditions have not been met during the applicable three-year performance period.

2023 Employee Stock Purchase Plan

The second purchase period commenced on December 15, 2023 and ended on June 14, 2024. The third purchase period commenced on June 15, 2024 and will end on December 14, 2024. The Company recorded $0.2 million in accrued liabilities as of September 30, 2024. Under the 2023 ESPP, 0 and 100,827 shares were issued for the three and nine months ended September 30, 2024, respectively.

Stock-Based Compensation Expense

The Company used Black-Scholes option pricing model to estimate fair value of each option at the grant date based on the following assumptions for the three and nine months ended September 30, 2024 and 2023:


	Three Months Ended September 30,		Three Months Ended September 30,		Nine Months Ended September 30,		Nine Months Ended September 30,
	2024		2023		2024		2023

Expected volatility	83.74% - 84.20%		87.34% - 87.93%		83.74% - 87.76%		75.30% - 92.20%
Expected dividend yield	0	%	0	%	0	%	0	%
Expected term (in years)	5.95 - 6.08		5.95 – 6.04		5.41 - 6.08		5.77 – 6.08
Risk-free interest rate	3.59% - 3.72%		4.14% - 4.61%		3.59% - 4.52%		3.30% - 4.61%

The following table presents the classification of stock-based compensation expense related to awards granted under equity incentive options (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Research and development expenses	$	2,640	$	3,572	$	12,081	$	8,661
General and administrative expenses	4,414		11,741		25,310		22,292
Total stock-based compensation expense	$	7,054	$	15,313	$	37,391	$	30,953

The stock-based compensation expense for the three and nine months ended September 30, 2024 was impacted by the departure of our founder and former CEO in May 2024. The departure resulted in a reversal of $13.5 million of PSU and PSO related expense offset by a $12.7 million net increase in stock-based compensation expense due to the partial accelerated vesting and modification of options and RSUs.

The stock-based compensation expense (in thousands) relates to the following equity-based awards:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Restricted stock units	$	1,618	$	2,345	$	14,857	$	7,884
Performance-based restricted stock units	(941)		4,265		(2,739)		4,265
Stock options	6,324		8,577		25,188		18,661
ESPP	53		126		232		143
Performance-based options	$	—	$	—	$	(147)	$	—
Total stock-based compensation expense	$	7,054	$	15,313	$	37,391	$	30,953

In the nine months ended September 30, 2023, the Company recognized $4.9 million of stock-based compensation expense related to assumed ValenzaBio options and $0.9 million related to unvested options and RSAs net-settled at the closing of the Acquisition. As of September 30, 2024 there was $50.9 million of unrecognized stock-based compensation expense related to granted stock options, which is expected to be recognized over a weighted-average period of 1.5 years. As of September 30, 2024, there was $12.5 million of unrecognized stock-based compensation expense related to RSUs

which is expected to be recognized over a weighted-average period of 1.7 years. The Company recognized a net reversal of $0.9 million in stock-based compensation expense during the three months ended September 30, 2024 related to PSUs. This expense is related to both the market and performance conditions associated with the PSUs and includes a reversal of $13.4 million related to the departure of our founder and former CEO in May 2024. As of September 30, 2024, the Company evaluated the clinical development milestone performance conditions and determined certain conditions to be probable of achievement. As of September 30, 2024, total compensation cost not yet recognized related to unvested PSUs was $10.1 million, which is expected to be recognized over a weighted-average period of 1.3 years. Total stock-based compensation expense not recognized related to unvested PSUs can increase up to $12.6 million depending on the future achievement of PSU performance conditions.

Cash, Cash Equivalents, Restricted Cash and Available-For-Sale Marketable Securities - Schedule of Restrictions on Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Cash and cash equivalents	$ 216,326	$ 218,097
Restricted cash	544	0
Total cash, cash equivalents and restricted cash	$ 216,870	$ 218,097	$ 381,738	$ 267,110

Consolidated Balance Sheet Components

9 Months Ended

Sep. 30, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Consolidated Balance Sheet Components

Prepaid expenses and other current assets

Prepaid expenses and other current assets consist of the following (in thousands):


	September 30, 2024		December 31, 2023
Credit voucher receivable	$	23,838	$	—
VAT receivable	4,320		3,985
Prepaid insurance and other current assets	2,244		1,712
Interest receivable	1,912		764
Prepaid other services	1,359		667
Prepaid research and development expenses	543		8,184
Total	$	34,216	$	15,312

Prepaid expenses and other assets, non-current

Other non-current assets consist of the following (in thousands):


	September 30, 2024		December 31, 2023
Credit voucher receivable	$	11,941	$	—
Prepaid research and development expenses, non-current	523		2,644
Security deposits	34		34
Total	$	12,498	$	2,678

Property, plant and equipment, net

Property, plant and equipment consisted of the following (in thousands):


	September 30, 2024		December 31, 2023
Construction in progress	$	—	$	1,460
Computer and other equipment	1,165		407
Furniture and fixtures	658		306
Leasehold improvements	209		121
Total property, plant and equipment, gross	2,032		2,294
Less: accumulated depreciation and amortization	(332)		(115)
Property, plant and equipment, net	$	1,700	$	2,179

Accrued research and development expenses

Accrued research and development expenses are comprised of the following (in thousands):


	September 30, 2024		December 31, 2023
Accrued clinical manufacturing expenses	$	6,894	$	22,232
Accrued clinical expenses	6,954		13,204
Total	$	13,848	$	35,436

Accrued compensation and other current liabilities

Accrued compensation and other current liabilities consist of the following (in thousands):


	September 30, 2024		December 31, 2023
Accrued compensation	$	5,145	$	5,417
Accrued professional service fees	458		1,099
Other accrued expenses and current liabilities	1,080		317
Total	$	6,683	$	6,833

Common Stock - Schedule of Common Stock Reserved for Future Issuance (Details) - shares	Sep. 30, 2024	Dec. 31, 2023
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	23,894,919	20,101,379
Outstanding stock options
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	14,071,995	9,630,623
Performance-based restricted stock units
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	792,908	2,964,072
Outstanding restricted stock units
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	1,204,470	2,166,016
ESPP Shares available for future grants
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	1,753,667	875,836
Shares available for future grants under Equity Incentive Plan
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	6,016,568	3,526,392
Options assumed upon ValenzaBio acquisition \| Outstanding stock options
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	55,311	938,440

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Common Stock (Tables)

9 Months Ended

Sep. 30, 2024

Equity [Abstract]

Schedule of Common Stock Reserved for Future Issuance

As of September 30, 2024 and December 31, 2023, Common Stock reserved for future issuance by the Company was as follows:


	September 30,	December 31,
	2024	2023
Shares available for future grants under Equity Incentive Plan	6,016,568	3,526,392
Outstanding stock options	14,071,995	9,630,623
Performance-based restricted stock units1	792,908	2,964,072
Outstanding restricted stock units	1,204,470	2,166,016
Options assumed upon ValenzaBio acquisition	55,311	938,440
ESPP Shares available for future grants	1,753,667	875,836
Total shares reserved for future issuance	23,894,919	20,101,379

1. The performance-based restricted stock units balance is based on the target number of shares.

Cash, Cash Equivalents, Restricted Cash and Available-For-Sale Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2024

Investments, Debt and Equity Securities [Abstract]

Schedule of Restrictions on Cash and Cash Equivalents

The following table provides a reconciliation of the Company’s cash and cash equivalents and non-current portion of restricted cash reported within the unaudited condensed consolidated balance sheets that sum to the total cash, cash equivalents and restricted cash shown in the Company’s condensed consolidated statement of cash flows:


	September 30, 2024		December 31, 2023
Cash and cash equivalents	$	216,326	$	218,097
Restricted cash	544		—
Total cash, cash equivalents and restricted cash	$	216,870	$	218,097

Schedule of Cash and Cash Equivalents


	September 30, 2024		December 31, 2023
Cash and cash equivalents	$	216,326	$	218,097
Restricted cash	544		—
Total cash, cash equivalents and restricted cash	$	216,870	$	218,097

Schedule of Available-for-Sale Marketable Securities

The following tables summarize the estimated fair value of the Company’s available-for-sale marketable securities as of September 30, 2024 and December 31, 2023 (in thousands):


As of September 30, 2024:	Total Amortized Cost		Total Unrealized Gain		Total Unrealized Loss		Total Estimated Fair Value

Money market funds (included in cash and cash equivalents)	$	201,253	$	—	$	-	$	201,253
U.S. Treasury obligations ($0 included in cash and cash equivalents)	230,870		248		-		231,118
Corporate debt obligations $1,331 included in cash and cash equivalents)	89,246		65		(7)		89,304
Federal agency obligations ($0 included in cash and cash equivalents)	26,878		79		(1)		26,956
Total available for sale marketable securities	$	548,247	$	392	$	(8)	$	548,631


As of December 31, 2023:	Total Amortized Cost		Total Unrealized Gain		Total Unrealized Loss		Total Estimated Fair Value

Money market funds (included in cash and cash equivalents)	$	23,205	$	—	$	-	$	23,205
U.S. Treasury obligations ($146,497 included in cash and cash equivalents)	525,198		156		(1)		525,353
Corporate debt obligations ($23,313 included in cash and cash equivalents)	135,288		36		(40)		135,284
Federal agency obligations ($15,344 included in cash and cash equivalents)	27,735		12		(1)		27,746
Total available for sale marketable securities	$	711,426	$	204	$	(42)	$	711,588

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
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-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
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+ Details

Description of Business, Organization and Liquidity	9 Months Ended
Description of Business, Organization and Liquidity	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business, Organization and Liquidity	Description of Business, Organization and Liquidity Organization and Business ACELYRIN, INC. (the “Company”) is a late-stage clinical biopharma company focused on identifying, acquiring, and accelerating the development and commercialization of transformative medicines. The Company was incorporated in the State of Delaware on July 27, 2020. Since its inception, the Company has devoted substantially all of its resources to organizing the Company, hiring personnel, business planning, acquiring and developing its product candidates, performing research and development, enabling manufacturing activities in support of its product development efforts, establishing and protecting its intellectual property portfolio, raising capital, and providing general and administrative support for these activities. The Company did not have any significant operations from the inception date until August 2021. On August 9, 2021, the Company entered into the License and Collaboration Agreement with Affibody AB, a Swedish company, and licensed worldwide development, manufacturing and commercialization rights to a therapeutic candidate, izokibep, for use in the treatment of inflammatory and autoimmune disorders, excluding rights in certain Asian and Nordic countries. See Note 7 for further details. On January 4, 2023, the Company closed the acquisition of ValenzaBio, Inc. (“ValenzaBio”) and issued as consideration 18,885,731 shares of its Class A common stock (“Class A Common Stock”). ValenzaBio was a privately held company developing therapies for autoimmune and inflammatory diseases. The ValenzaBio acquisition added additional assets to the Company’s portfolio, including lonigutamab and SLRN-517. See Note 3 for further details. Reverse Stock Split In April 2023, the Company effected a reverse split of shares of the Company’s outstanding common stock and redeemable convertible preferred stock at a ratio 1.972-for-1 (the “Reverse Stock Split”). The number of authorized shares and par value per share were not adjusted as a result of the Reverse Stock Split. All references to shares, restricted stock units (“RSUs”) and restricted stock awards (“RSAs”), options to purchase common stock, share data, per share data, and related information contained in the condensed consolidated financial statements have been retrospectively adjusted to reflect the effect of the Reverse Stock Split for all periods presented. Initial Public Offering On May 4, 2023, the Company’s Form S-1 Registration Statement for its initial public offering (the “IPO”) was declared effective, and on May 9, 2023, the Company closed its IPO and issued 34,500,000 shares of common stock at a price to the public of $18.00 per share, including 4,500,000 shares issued upon the exercise of underwriters’ option to purchase additional shares of common stock. The Company received gross proceeds of $621.0 million. Net proceeds were approximately $573.6 million, after deducting underwriting discounts and commissions and offering costs of $47.4 million. The common stock began trading on the Nasdaq Global Select Market on May 5, 2023, under the symbol “SLRN”. Immediately prior to the IPO closing, each share of the Company’s redeemable convertible preferred stock then outstanding converted into an equivalent number of shares of Class A Common Stock, and thereafter each share of Class A Common Stock then issued and outstanding was reclassified and became one share of the Company’s common stock. Liquidity The Company has incurred significant losses and negative cash flows from operations since its inception. During the nine months ended September 30, 2024 and 2023, the Company incurred net losses of $169.2 million and $286.4 million, respectively. The net loss of $169.2 million in the nine months ended September 30, 2024 includes $37.0 million of other income related to payments in the first quarter of 2024. The net loss of $286.4 million in the nine months ended September 30, 2023 includes $123.1 million of expenses related to acquired in-process research and development assets without alternative future use and a $10.0 million license fee payment to Pierre Fabre incurred in connection with the ValenzaBio acquisition. As of September 30, 2024, the Company had an accumulated deficit of $657.9 million. Cash used in operating activities was $182.3 million and $96.1 million for the nine months ended September 30, 2024 and 2023, respectively. The Company has historically financed its operations primarily through the sale of shares of its redeemable convertible preferred stock in private placements and the sale of shares of its common stock in its IPO. As of September 30, 2024, the Company had cash, cash equivalents, restricted cash and short-term marketable securities of $562.9 million. The Company does not have any products approved for sale and has not generated any revenue from product sales to date. The Company expects to continue to incur significant and increasing expenses and substantial losses for the foreseeable future as it continues its development of and seeks regulatory approvals for its product candidates and commercializes any approved products, seeks opportunities to selectively expand its product pipeline and invests in its organization. The Company’s ability to achieve and sustain profitability will depend on its ability to successfully develop, obtain regulatory approval for and commercialize its product candidates. There can be no assurance that the Company will ever earn revenue or achieve profitability, or if achieved, that the revenue or profitability will be sustained on a continuing basis. Unless and until it does, the Company will need to continue to raise additional capital. Based on its current operating plan, management estimates that its existing cash, cash equivalents and restricted cash, including the proceeds from the IPO, will be sufficient to fund its operating plan and capital expenditure requirements for at least the next 12 months from the date of issuance of these condensed consolidated financial statements.

Consolidated Balance Sheet Components - Schedule of Prepaid and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Credit voucher receivable	$ 23,838	$ 0
VAT receivable	4,320	3,985
Prepaid insurance and other current assets	2,244	1,712
Interest receivable	1,912	764
Prepaid other services	1,359	667
Prepaid research and development expenses	543	8,184
Total	$ 34,216	$ 15,312

Net Loss Per Share Attributable to Common Stockholders - Schedule of Outstanding Shares of Potentially Dilutive Securities (Details) - shares	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)	15,618,228	12,433,489
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	14,071,995	8,704,462
Stock options \| ValenzaBio Asset Acquisition
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	55,311	1,249,811
Unvested RSUs outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1,204,470	2,183,413
Unvested PSUs expected to vest
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	178,404	0
Common stock subject to repurchase
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	295,803
ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	108,048	0

Summary of Significant Accounting Policies (Details) - institution	Sep. 30, 2024	Dec. 31, 2023
Accounting Policies [Abstract]
Number of financial institutions with cash deposits	1	1

Cash, Cash Equivalents, Restricted Cash and Available-For-Sale Marketable Securities - Schedule of Available-for-Sale Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-Sale [Line Items]
Total Amortized Cost	$ 548,247	$ 711,426
Total Unrealized Gain	392	204
Total Unrealized Loss	(8)	(42)
Total Estimated Fair Value	548,631	711,588
Cash and cash equivalents
Debt Securities, Available-for-Sale [Line Items]
Total Estimated Fair Value	202,584	208,359
Money market funds (included in cash and cash equivalents)
Debt Securities, Available-for-Sale [Line Items]
Total Amortized Cost	201,253	23,205
Total Unrealized Gain	0	0
Total Unrealized Loss	0	0
Total Estimated Fair Value	201,253	23,205
U.S. Treasury obligations
Debt Securities, Available-for-Sale [Line Items]
Total Amortized Cost	230,870	525,198
Total Unrealized Gain	248	156
Total Unrealized Loss	0	(1)
Total Estimated Fair Value	231,118	525,353
U.S. Treasury obligations \| Cash and cash equivalents
Debt Securities, Available-for-Sale [Line Items]
Total Estimated Fair Value	0	146,497
Corporate debt obligations
Debt Securities, Available-for-Sale [Line Items]
Total Amortized Cost	89,246	135,288
Total Unrealized Gain	65	36
Total Unrealized Loss	(7)	(40)
Total Estimated Fair Value	89,304	135,284
Corporate debt obligations \| Cash and cash equivalents
Debt Securities, Available-for-Sale [Line Items]
Total Estimated Fair Value	1,331	23,313
Federal agency obligations
Debt Securities, Available-for-Sale [Line Items]
Total Amortized Cost	26,878	27,735
Total Unrealized Gain	79	12
Total Unrealized Loss	(1)	(1)
Total Estimated Fair Value	26,956	27,746
Federal agency obligations \| Cash and cash equivalents
Debt Securities, Available-for-Sale [Line Items]
Total Estimated Fair Value	$ 0	$ 15,344

Consolidated Balance Sheet Components (Tables)

9 Months Ended

Sep. 30, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure

Prepaid expenses and other current assets consist of the following (in thousands):


	September 30, 2024		December 31, 2023
Credit voucher receivable	$	23,838	$	—
VAT receivable	4,320		3,985
Prepaid insurance and other current assets	2,244		1,712
Interest receivable	1,912		764
Prepaid other services	1,359		667
Prepaid research and development expenses	543		8,184
Total	$	34,216	$	15,312

Other non-current assets consist of the following (in thousands):


	September 30, 2024		December 31, 2023
Credit voucher receivable	$	11,941	$	—
Prepaid research and development expenses, non-current	523		2,644
Security deposits	34		34
Total	$	12,498	$	2,678

Schedule of Property, Plant and Equipment

Property, plant and equipment consisted of the following (in thousands):


	September 30, 2024		December 31, 2023
Construction in progress	$	—	$	1,460
Computer and other equipment	1,165		407
Furniture and fixtures	658		306
Leasehold improvements	209		121
Total property, plant and equipment, gross	2,032		2,294
Less: accumulated depreciation and amortization	(332)		(115)
Property, plant and equipment, net	$	1,700	$	2,179

Schedule of Accrued Research and Development Expense

Accrued research and development expenses are comprised of the following (in thousands):


	September 30, 2024		December 31, 2023
Accrued clinical manufacturing expenses	$	6,894	$	22,232
Accrued clinical expenses	6,954		13,204
Total	$	13,848	$	35,436

Schedule of Other Current Liabilities

Accrued compensation and other current liabilities consist of the following (in thousands):


	September 30, 2024		December 31, 2023
Accrued compensation	$	5,145	$	5,417
Accrued professional service fees	458		1,099
Other accrued expenses and current liabilities	1,080		317
Total	$	6,683	$	6,833

Fair Value Measurements

9 Months Ended

Sep. 30, 2024

Fair Value Disclosures [Abstract]

Fair Value Measurements

The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows:

Level 1 — Quoted prices in active markets for identical assets or liabilities.

Level 2 — Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

The Company’s financial instruments measured at fair value on a recurring basis consist of Level 1, Level 2, and Level 3 financial instruments. Usually, short term marketable securities are considered Level 2 when their fair values are determined using inputs that are observable in the market or can be derived principally from or corroborated by observable market data such as pricing for similar securities, recently executed transactions, cash flow models with yield curves, and benchmark securities. In addition, Level 2 financial instruments are valued using comparisons to like-kind financial instruments and models that use readily observable market data as their basis. Corporate debt obligations, commercial paper, government agency obligations and asset-backed securities are valued primarily using market prices of comparable securities, bid/ask quotes, interest rate yields and prepayment spreads and are included in Level 2.

Financial assets and liabilities are considered Level 3 when their fair values are determined using pricing models, discounted cash flow methodologies, or similar techniques, and at least one significant model assumption or input is unobservable.

The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands):


	Fair Value Measurements as of September 30, 2024
As of September 30, 2024:	Total		Level 1		Level 2		Level 3

Assets:
Money market funds (included in cash and cash equivalents)	$	201,253	$	201,253	$	-	$	-
U.S. Treasury obligations ($0 included in cash and cash equivalents)	231,118		-		231,118		-
Corporate debt obligations ($1,331 included in cash and cash equivalents)	89,304		-		89,304		-
Federal agency obligations ($0 included in cash and cash equivalents)	26,956		-		26,956		-
Total fair value of assets	$	548,631	$	201,253	$	347,378	$	-


	Fair Value Measurements as of December 31, 2023
As of December 31, 2023:	Total		Level 1		Level 2		Level 3

Assets:
Money market funds (included in cash and cash equivalents)	$	23,205	$	23,205	$	-	$	-
U.S. Treasury obligations ($146,497 included in cash and cash equivalents)	525,353		-		525,353		-
Corporate debt obligations ($23,313 included in cash and cash equivalents)	135,284		-		135,284		-
Federal agency obligations ($15,344 included in cash and cash equivalents)	27,746		-		27,746		-
Total fair value of assets	$	711,588	$	23,205	$	688,383	$	-


Classified as:	September 30, 2024		December 31, 2023
Cash and cash equivalents	$	202,584	$	208,359
Short-term marketable securities	$	346,047	$	503,229
Total cash equivalents and marketable securities	$	548,631	$	711,588

- Definition

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

+ References

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

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
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-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
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-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478119/940-820-50-1

+ Details

Equity Incentive Plan (Tables)

9 Months Ended

Sep. 30, 2024

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Option Activity

A summary of option activity under the 2020 and 2023 Plan is as follows:


	Number of Options	Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2023	9,630,623	$	10.4619	9.0	$	12,007
Options granted	9,773,227	6.3274
Options exercised	(511,255)	2.9748
Options expired	(128,091)	7.1906
Options forfeited	(4,692,509)	9.7232
Outstanding at September 30, 2024	14,071,995	$	8.1385	8.0	$	3,829
Exercisable at September 30, 2024	3,812,458	$	9.9887	4.7	$	1,094
Vested and expected to vest at September 30, 2024	14,071,995	$	8.1385	8.0	$	3,829

Schedule of Restricted Stock Unit Activity

A summary of unvested RSU activity is presented in the following table:


	Number of RSUs	Weighted-Average Grant Date Fair Value
Unvested at December 31, 2023	2,166,016	$	22.90
Granted	2,171,896	6.56
Vested	(1,019,894)	9.36
Forfeited	(2,113,548)	18.23
Unvested at September 30, 2024	1,204,470	$	13.09

Schedule of Performance Share Activity

A summary of PSU activity based on the target number of shares is presented in the following table:


	Number of PSUs	Weighted-Average Grant Date Fair Value*
Outstanding at December 31, 2023	2,964,072	$	27.43
Granted	—
Vested	—
Forfeited	(2,171,164)	27.43
Outstanding at September 30, 2024	792,908	$	27.43

*The grant date fair value is based only on the PSUs with market conditions and does not factor in any performance conditions.

Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions


	Three Months Ended September 30,		Three Months Ended September 30,		Nine Months Ended September 30,		Nine Months Ended September 30,
	2024		2023		2024		2023

Expected volatility	83.74% - 84.20%		87.34% - 87.93%		83.74% - 87.76%		75.30% - 92.20%
Expected dividend yield	0	%	0	%	0	%	0	%
Expected term (in years)	5.95 - 6.08		5.95 – 6.04		5.41 - 6.08		5.77 – 6.08
Risk-free interest rate	3.59% - 3.72%		4.14% - 4.61%		3.59% - 4.52%		3.30% - 4.61%

Schedule of Share-Based Payment Arrangement, Expensed and Capitalized, Amount

The following table presents the classification of stock-based compensation expense related to awards granted under equity incentive options (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Research and development expenses	$	2,640	$	3,572	$	12,081	$	8,661
General and administrative expenses	4,414		11,741		25,310		22,292
Total stock-based compensation expense	$	7,054	$	15,313	$	37,391	$	30,953

The stock-based compensation expense (in thousands) relates to the following equity-based awards:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Restricted stock units	$	1,618	$	2,345	$	14,857	$	7,884
Performance-based restricted stock units	(941)		4,265		(2,739)		4,265
Stock options	6,324		8,577		25,188		18,661
ESPP	53		126		232		143
Performance-based options	$	—	$	—	$	(147)	$	—
Total stock-based compensation expense	$	7,054	$	15,313	$	37,391	$	30,953

Consolidated Balance Sheet Components - Schedule of Accrued Compensation and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued compensation	$ 5,145	$ 5,417
Accrued professional service fees	458	1,099
Other accrued expenses and current liabilities	1,080	317
Total	$ 6,683	$ 6,833

Equity Incentive Plan - Schedule of 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 Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense	$ 7,054	$ 15,313	$ 37,391	$ 30,953
Restricted stock units
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense	1,618	2,345	14,857	7,884
Performance-based restricted stock units
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense	(941)	4,265	(2,739)	4,265
Stock options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense	6,324	8,577	25,188	18,661
ESPP
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense	53	126	232	143
Performance-based options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense	0	0	(147)	0
Research and development expenses
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense	2,640	3,572	12,081	8,661
General and administrative expenses
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total stock-based compensation expense	$ 4,414	$ 11,741	$ 25,310	$ 22,292

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
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-Name Accounting Standards Codification
-Section 35
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Pay vs Performance Disclosure
Net losses	$ (48,548)	$ (85,672)	$ (34,973)	$ (83,940)	$ (26,039)	$ (176,450)	$ (169,193)	$ (286,429)

- Definition

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

+ References

+ Details

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Common stock, authorized (in shares)	790,000,000	790,000,000
Common stock, issued (in shares)	99,944,302	97,865,890
Common stock, outstanding (in shares)	99,944,302	97,865,890

Commitments and Contingent Liabilities - Schedule of Maturity Analysis of Operating Lease Liability (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Jul. 31, 2023	Jan. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
2024 (remainder of the year)	$ 394
2025	2,200
2026	2,275
2027	2,352
2028	2,291
2029	1,548
Total future lease payments	11,060
Less imputed interest	(3,678)
Total operating lease liability balance	7,382
Less current portion of lease liability	(824)		$ (200)
Operating lease liability, non-current	$ 6,558	$ 1,194	$ 5,700	$ 1,300

Condensed Consolidated Statements of Operations and Comprehensive Loss - 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	$ 31,612	$ 74,562	$ 166,026	$ 272,512
General and administrative	12,326	19,861	53,711	44,440
Restructuring charges	10,809	0	10,809	0
Total operating expenses	54,747	94,423	230,546	316,952
Loss from operations	(54,747)	(94,423)	(230,546)	(316,952)
Change in fair value of derivative tranche liability	0	0	0	10,291
Interest income	7,535	10,502	25,132	20,486
Other income (expense), net	(1,336)	(19)	36,221	(254)
Net loss	(48,548)	(83,940)	(169,193)	(286,429)
Other comprehensive gain (loss)
Unrealized gain (loss) on short-term marketable securities, net	551	(94)	222	36
Total other comprehensive gain (loss)	551	(94)	222	36
Net loss and other comprehensive loss	$ (47,997)	$ (84,034)	$ (168,971)	$ (286,393)
Net loss per share attributable to common stockholder, basic (in shares)	$ (0.49)	$ (0.87)	$ (1.71)	$ (4.68)
Net loss per share attributable to common stockholder, diluted (in shares)	$ (0.49)	$ (0.87)	$ (1.71)	$ (4.68)
Weighted-average common shares outstanding, basic (in shares)	99,835,707	96,872,747	98,973,518	61,138,105
Weighted-average common shares outstanding, diluted (in shares)	99,835,707	96,872,747	98,973,518	61,138,105

Consolidated Balance Sheet Components - Schedule of Accrued Research and Development Expense (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued clinical manufacturing expenses	$ 6,894	$ 22,232
Accrued clinical expenses	6,954	13,204
Total	$ 13,848	$ 35,436

Net Loss Per Share Attributable to Common Stockholders (Tables)

9 Months Ended

Sep. 30, 2024

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted

The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share data):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Numerator:
Net loss	$	(48,548)	$	(83,940)	$	(169,193)	$	(286,429)
Denominator:
Weighted average common shares outstanding	99,835,707		97,227,070		99,050,167		61,580,296
Less: Weighted-average common shares subject to repurchase	0		(354,323)		(76,649)		(442,191)
Weighted-average common shares outstanding, basic and diluted	99,835,707		96,872,747		98,973,518		61,138,105
Net loss per share attributable to common stockholders, basic and diluted	$	(0.49)	$	(0.87)	$	(1.71)	$	(4.68)

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been antidilutive:


	As of September 30,
	2024	2023
Outstanding options to purchase common stock	14,071,995	8,704,462
Unvested RSUs outstanding	1,204,470	2,183,413
Unvested PSUs expected to vest	178,404	—
Outstanding options to purchase common stock assumed upon acquisition of ValenzaBio	55,311	1,249,811
Common stock subject to repurchase	—	295,803
ESPP	108,048	—
Total	15,618,228	12,433,489

Restructuring - Narrative (Details) $ in Thousands		3 Months Ended		9 Months Ended
Restructuring - Narrative (Details) $ in Thousands	Aug. 10, 2024 people	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated \| people	40
Number of positions eliminated, percent	33.33%
Restructuring charges				$ 46,482
Restructuring charges		$ 10,809	$ 0	10,809	$ 0
Severance and other employee-related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring plan, expected cost		4,300		4,300
Restructuring charges		3,600		3,586
Restructuring and related cost		1,600		1,600
Service cancellation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges		42,900		$ 42,896
Restructuring, incurred cost		7,200
Restructuring reserve, credit voucher		$ 35,700

ValenzaBio Acquisition - Schedule of Total Purchase Consideration (Details) - ValenzaBio Asset Acquisition	Jan. 04, 2023 USD ($) $ / shares shares
Asset Acquisition [Line Items]
Issued common stock	$ 128,735,000
Transaction costs	1,271,000
Cash	7,663
Total	$ 130,014,000
Shares issued (in dollars per share) \| $ / shares	$ 6.86
Shares issued (in shares) \| shares	2,013,673
Contingent consideration	$ 100,000

Commitments and Contingent Liabilities - Narrative (Details)	1 Months Ended			3 Months Ended			9 Months Ended		12 Months Ended
	Nov. 30, 2023 USD ($)	Jul. 31, 2023 USD ($) ft²	Jan. 31, 2023 USD ($) ft²	Sep. 30, 2024 USD ($)	Jun. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2023 USD ($)
Other Commitments [Line Items]
Research and development				$ 31,612,000		$ 74,562,000	$ 166,026,000	$ 272,512,000
Unrecorded unconditional purchase obligation				19,500,000			19,500,000			$ 142,300,000
Loss on contract termination					$ 14,300,000
Office space leased (in square feet) \| ft²		22,365	10,012
Term of contract		60 months	65 months
Renewal term		5 years	3 years
Monthly payments		$ 150,000	$ 30,500
Annual rent increase		3.50%	3.00%
Rent abatement, term			6 months
Security deposit				34,000			34,000			34,000
Operating lease right-of-use asset		$ 6,100,000	$ 1,300,000	6,979,000			6,979,000			1,195,000
Operating lease liability, non-current		5,700,000	$ 1,300,000	6,558,000			6,558,000			$ 1,194,000
Operating lease liability, current		$ 200,000		824,000			824,000
Operating lease costs (less than)				500,000		100,000	700,000	200,000
Variable lease cost				$ 200,000		$ 0	$ 200,000	$ 0
Weighted average remaining lease term				4 years 9 months 18 days			4 years 9 months 18 days
Discount rate				18.00%			18.00%
Lease liability measurement (less than)							$ 400,000
Letter of Credit
Other Commitments [Line Items]
Security deposit				$ 200,000			$ 200,000
Affibody \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement
Other Commitments [Line Items]
Research and development	$ 15,000,000.0								$ 25,000,000.0

Cover - shares	9 Months Ended
Cover - shares	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	001-41696
Entity Registrant Name	ACELYRIN, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	85-2406735
Entity Address, Address Line One	4149 Liberty Canyon Road
Entity Address, City or Town	Agoura Hills
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	91301
City Area Code	805
Local Phone Number	730-0360
Title of 12(b) Security	Common Stock ($0.00001 par value)
Trading Symbol	SLRN
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		100,325,569
Entity Central Index Key	0001962918
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Amendment Flag	false

Other Income	9 Months Ended
Other Income	Sep. 30, 2024
Other Income and Expenses [Abstract]
Other Income	Other Income Arrangements with Vendors In March 2024, the Company entered into arrangements with certain vendors where the Company received a payment of $30.0 million and a $5.0 million service credit. The $30.0 million payment received from these arrangements was recorded as a gain in other income (expense), net in the condensed consolidated statement of operations and comprehensive loss for the nine months ended September 30, 2024 and included in the cash flows from operating activities in the condensed consolidated statement of cash flows for the same period. The $5.0 million service credit was recorded as a credit within research and development expenses. Asset sale In January 2024, the Company entered into an asset purchase agreement (“Purchase Agreement”) with Tenet Medicines, Inc. (“Tenet”). The Company recorded $7.0 million cash received as other income (expense), net in the condensed consolidated statement of operations and comprehensive loss for the nine months ended September 30, 2024. In consideration for the licenses and other rights Tenet received under the Purchase Agreement, the Company is entitled to receive development, regulatory and commercial milestone payments of up to $157.5 million, royalty on worldwide net sales and payments on sublicense income.

Commitments and Contingent Liabilities

9 Months Ended

Sep. 30, 2024

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingent Liabilities

License Agreements

The Company is required to pay certain milestones upon the achievement of specific development and regulatory events, upon products commercialization and products’ royalties under its license agreements, including its agreements with Affibody, Pierre Fabre, Novelty Nobility and other non-exclusive license agreements. None of the milestones, other than the $15.0 million Affibody milestone in November 2023, were achieved or probable as all products were in development. As such, no milestones or royalties were accrued in the condensed consolidated balance sheets as of September 30, 2024 and December 31, 2023.

Research and Development Agreements

The Company enters into various agreements in the ordinary course of business, such as those with suppliers, contract research organizations, contract manufacturing organizations, and clinical trial sites. These contracts generally provide for termination on notice or may have a potential termination fee if a purchase order is canceled within a specified time. The total value of non-cancellable obligations under contracts was $19.5 million and $142.3 million as of September 30, 2024, and December 31, 2023, respectively. This presentation of non-cancellable purchase obligations does not include any estimates of potential reduction of such liabilities related to mitigation obligations of the counter-parties in the event of cancellation under the terms of our engagements.

In July 2024, the Company and a vendor entered into an agreement to terminate a supply agreement. All post-termination activities are expected to be completed in the third and fourth quarters of 2024. The Company incurred and recognized $14.3 million for the termination costs in the quarter ended June 30, 2024, the period in which the obligation was incurred. These contract termination costs were included in research and development in the Condensed Consolidated Statement of Operations and Comprehensive Loss for the nine months ended September 30, 2024.

In October 2024, the Company and a vendor entered into an agreement to cancel certain services under a manufacturing agreement. See Note 13 to the condensed consolidated financial statements included in Part I, Item 1 of this Quarterly Report on Form 10-Q.

No other amounts related to termination and cancellation changes were accrued during the three and nine months ended September 30, 2024, and year ended December 31, 2023, as the Company has not determined cancellation under any other agreements to be probable.

Lease

In January 2023, the Company entered into a lease agreement to rent approximately 10,012 square feet of office space in southern California. The term of the lease is 65 months with an option to extend it for an additional three years. Monthly rent payments are approximately $30,500, subject to an annual 3.0% increase and six months rental abatement during the first year. In addition to the base rent, the Company is obligated to pay variable costs related to its share of operating expenses and taxes. In connection with the lease agreement, the Company made a security deposit of $34,000, that is included in prepaid expenses and other assets, non-current in the condensed consolidated balance sheet as of September 30, 2024 and December 31, 2023. As of the lease commencement date, the Company recorded $1.3 million as right-of-use (“ROU”) asset and operating lease liability, non-current, in the condensed consolidated balance sheet.

In July 2023, the Company entered into a lease agreement to rent approximately 22,365 square feet of office space in South San Francisco, California. The term of the lease is 60 months with an option to extend it for an additional five years. Monthly rent payments are approximately $150,000, subject to an annual 3.5% increase. In addition to the base rent, the Company is obligated to pay variable costs related to its share of operating expenses and taxes. In connection with the lease agreement, the Company made a security deposit in the form of a letter of credit of $0.2 million that is classified as non-current in the condensed consolidated balance sheet as of September 30, 2024. As of the lease commencement date, the Company recorded $6.1 million as the ROU asset, $0.2 million as the operating lease liability, current, and $5.7 million as the operating lease liability, non-current, in the condensed consolidated balance sheet.

Fixed operating lease costs were $0.5 million and $0.7 million for the three and nine months ended September 30, 2024, respectively. Variable operating lease costs were $0.2 million for the three and nine months ended September 30, 2024. Operating lease costs were less than $0.1 million and $0.2 million for the three and nine months ended September 30, 2023, respectively. Variable lease operating lease costs were $0 for the three and nine months ended September 30, 2023. Operating lease costs were recorded in general and administrative expenses and research and development expenses in the condensed consolidated statements of operations and comprehensive loss.

The following table summarizes a maturity analysis of the Company’s operating lease liabilities showing the aggregate lease payments as of September 30, 2024 (in thousands):


2024 (remainder of the year)	$	394
2025	2,200
2026	2,275
2027	2,352
2028	2,291
2029	1,548
Total future lease payments	11,060
Less imputed interest	(3,678)
Total operating lease liability balance	7,382
Less current portion of lease liability	(824)
Operating lease liability, non-current	$	6,558

The weighted-average remaining lease term was 4.8 years and the weighted-average discount rate was 18%.

Cash paid for amounts included in the measurement of lease liabilities was $0.4 million.

Legal Contingencies

On November 15, 2023, a purported federal securities class action lawsuit was commenced in the United States District Court for the Central District of California. An amended complaint was filed on March 26, 2024 (Boukadoum v. Acelyrin, Inc. et al., No. 2:23-cv-09672-FMO-MAA), naming us and current and former executive officers and directors as defendants. The complaint alleges that the defendants violated the Exchange Act and Securities Act by misleading investors about the Phase 2b trial of izokibep in HS. The original complaint was filed following our announcement of the week 16 results from the Part B portion of such Phase 2b trial. The complaint seeks damages and an award of reasonable costs and expenses, including attorneys' fees, expert fees and other costs, as well as such other and further relief as the court may deem just and proper.

It is possible that additional suits will be filed, or allegations made by stockholders, with respect to these same or other matters and also naming the Company and/or its officers and directors as defendants. This lawsuit and any other potential lawsuits are subject to inherent uncertainties, and the actual defense and disposition costs will depend upon many unknown factors. The outcome of this lawsuit is necessarily uncertain. The Company could be forced to expend significant resources in the defense against this and any other related lawsuits and the Company may not prevail. The Company currently is not able to estimate the possible loss to the Company from this lawsuit, as this lawsuit is currently at an early stage, and such amounts could be material to the Company’s financial statements even if the Company prevails in the defense against this lawsuit. The Company cannot be certain how long it may take to resolve this lawsuit or the possible amount of any damages that the Company may be required to pay. The Company does not consider any payment to be probable or reasonably estimable and has not accrued for any potential liability relating to this lawsuit.

From time to time, the Company may become involved in additional legal proceedings or be subject to claims arising in the ordinary course of business. The Company records a liability for such matters when it is probable that future losses will be incurred and that such losses can be reasonably estimated. Significant judgment is required to determine both probability and the estimated amount.

Guarantees and Indemnifications

In the normal course of business, the Company enters into agreements that contain a variety of representations and provide for general indemnification. Its exposure under these agreements is unknown because it involves claims that may be made against the Company in the future. To the extent permitted under Delaware law, the Company has agreed to indemnify its directors and officers for certain events or occurrences while the director or officer is, or was serving, at a request in such capacity. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. As of September 30, 2024, the Company did not have any material indemnification claims that were probable or reasonably possible and consequently has not recorded related liabilities.

Insider Trading Arrangements	3 Months Ended	9 Months Ended
Insider Trading Arrangements	Sep. 30, 2024 shares	Sep. 30, 2024 shares
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Terminated	false
Sanam Pangali [Member]
Trading Arrangements, by Individual
Material Terms of Trading Arrangement		During the three months ended September 30, 2024, Sanam Pangali, former Chief Legal Officer and Head of People of the Company, terminated a written plan intended to satisfy the affirmative defense conditions of Rule 10b5-1 on October 3, 2024, previously adopted on August 14, 2023 and covering the sale of 23,130 shares of common stock of the Company. Ms. Pangali resigned from the Company effective September 27, 2024.
Name	Sanam Pangali
Title	Chief Legal Officer
Rule 10b5-1 Arrangement Terminated	true
Termination Date	October 3, 2024
Aggregate Available	23,130	23,130

Equity Incentive Plan - Schedule of Restricted Stock Unit Activity (Details) - Restricted stock units	9 Months Ended
	Sep. 30, 2024 $ / shares shares
Number of Shares
Outstanding at beginning of period (in shares) \| shares	2,166,016
Shares granted (in shares) \| shares	2,171,896
Vested (in shares) \| shares	(1,019,894)
Forfeited (in shares) \| shares	(2,113,548)
Outstanding at end of period (in shares) \| shares	1,204,470
Weighted-Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share) \| $ / shares	$ 22.90
Granted (in dollars per share) \| $ / shares	6.56
Vested (in dollars per share) \| $ / shares	9.36
Forfeited (in dollars per share) \| $ / shares	18.23
Outstanding at end of period (in dollars per share) \| $ / shares	$ 13.09

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities:
Net loss	$ (169,193)	$ (286,429)
Adjustments to reconcile net loss to net cash used in operations:
Stock-based compensation expense	37,391	30,953
Income from sale of asset	(7,000)
Expense related to acquired in-process research and development assets	0	133,057
Net amortization of premiums and accretion of discounts on marketable securities	(15,110)	(5,564)
Change in fair value of derivative tranche liability	0	(10,291)
Depreciation and amortization expense	277	67
Loss on disposal of property, plant and equipment	1,369
Non-cash lease expense	322	108
Changes in assets and liabilities:
Prepaid expense and other current assets	(18,293)	(3,323)
Prepaid expenses and other assets, non-current	(9,820)	1,724
Accounts payable	(24,370)	11,225
Accrued research and development expenses	(21,588)	30,773
Accrued compensation and other current liabilities	(150)	2
Accrued restructuring liabilities	44,636	0
Operating lease liability	(593)	(96)
Severance liability	(216)	1,720
Net cash used in operating activities	(182,338)	(96,074)
Cash flows from investing activities
Proceeds from sale of asset	7,000
ValenzaBio assets acquisition cash acquired, net of acquisition costs	0	10,007
Cash paid to acquire in-process research and development assets	0	(10,000)
Purchase of marketable securities	(575,175)	(537,987)
Proceeds from maturities of short-term marketable securities	736,912	128,728
Sales of marketable securities	10,016	56,310
Purchase of property, plant and equipment	(1,166)	(2,196)
Net cash provided by (used in) investing activities	177,587	(355,138)
Cash flows from financing activities
Proceeds from exercise of common stock options and issuance of common stock upon settlement of restricted stock unites, net of shares withheld for taxes, and under the employee stock purchase plan	3,524	31
Taxes paid related to net share settlement of restricted stock units	0	(8,325)
Issuance of common stock upon initial public offering, net of commissions and issuance costs	0	574,134
Net cash provided by financing activities	3,524	565,840
Net increase (decrease) in cash, cash equivalents and restricted cash	(1,227)	114,628
Cash, cash equivalents and restricted cash at beginning of period	218,097	267,110
Cash, cash equivalents and restricted cash at end of period	216,870	381,738
Supplemental disclosure of cash flow information:
Conversion of 40,743,522 redeemable convertible preferred stock upon the closing of initial public offering	0	396,593
Common stock issued in connection with ValenzaBio acquisition	0	128,735
Right-of-use assets obtained in exchange for operating lease liability	6,106	1,348
Property and equipment purchase in accounts payable and accrued liabilities	$ 120	$ 0

Significant Agreements (Details) - USD ($)			1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
Significant Agreements (Details) - USD ($)	Jan. 04, 2023	Mar. 25, 2021	Nov. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2021	Dec. 31, 2023	Oct. 31, 2021	Sep. 30, 2021	Aug. 30, 2021	Aug. 09, 2021
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development				$ 31,612,000	$ 74,562,000	$ 166,026,000	$ 272,512,000
Affibody \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate milestone payments										$ 22,000,000.0	$ 3,000,000.0	$ 3,000,000.0
Maximum aggregate milestone payments													$ 280,000,000.0
Payment due prior to milestone													$ 30,000,000.0
Research and development			$ 15,000,000.0					$ 25,000,000.0
Aggregate milestone payments, period		10 years
Contingent payments, percentage													33.33%
Fair value threshold percentage													33.33%
Probable milestone payments				0		0			$ 0
Pierre Fabre \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate milestone payments		$ 10,000,000.0
Aggregate milestone payments, period		10 years
Probable milestone payments				0		0
One-time payment		$ 31,000,000.0
Termination period		9 months
Pierre Fabre \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement \| Development and Regulatory Milestone Payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum aggregate milestone payments		$ 99,500,000
Pierre Fabre \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement \| Commercial Sales Milestone Payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum aggregate milestone payments		$ 390,000,000.0
Novelty Nobility \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate milestone payments, period	10 years
Probable milestone payments				$ 0		$ 0
Contract termination, period	30 days
Novelty Nobility \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement \| Development and Regulatory Milestone Payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum aggregate milestone payments	$ 44,300,000
Novelty Nobility \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement \| Commercial Sales Milestone Payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum aggregate milestone payments	$ 682,000,000.0

Equity Incentive Plan - Schedule of Performance Share Activity (Details) - Performance Shares - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Number of Shares
Outstanding at beginning of period (in shares)	2,964,072
Shares granted (in shares)	0
Vested (in shares)	0
Forfeited (in shares)	(2,171,164)
Outstanding at end of period (in shares)	792,908	2,964,072
Weighted-Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share)	$ 27.43
Granted (in dollars per share)		$ 27.43
Vested (in dollars per share)
Forfeited (in dollars per share)	27.43
Outstanding at end of period (in dollars per share)	$ 27.43	$ 27.43

Consolidated Balance Sheet Components - Schedule of Prepaid and Other Noncurrent Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Credit voucher receivable	$ 11,941	$ 0
Prepaid research and development expenses, non-current	523	2,644
Security deposits	34	34
Total	$ 12,498	$ 2,678

ValenzaBio Acquisition - Narrative (Details)		3 Months Ended			9 Months Ended
ValenzaBio Acquisition - Narrative (Details)	Jan. 04, 2023 USD ($) shares	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 20, 2022 subsidiary
Asset Acquisition [Line Items]
Number of subsidiaries formed \| subsidiary								2
Expense related to acquired in-process research and development assets					$ 0	$ 133,057,000
Research and development		$ 31,612,000	$ 74,562,000		166,026,000	272,512,000
Severance payable, current		$ 0			0		$ 300,000
Payments to acquire in-process research and development					$ 0	10,000,000
Minimum
Asset Acquisition [Line Items]
Severance payment obligation period	3 months
Maximum
Asset Acquisition [Line Items]
Severance payment obligation period	18 months
Unvested Equity Awards
Asset Acquisition [Line Items]
Separately recognized expenses				$ 900,000
Severance Payment Obligation
Asset Acquisition [Line Items]
Liabilities recognized	$ 5,100,000
Severance Payment Obligation \| Measurement Input, Discount Rate
Asset Acquisition [Line Items]
Measurement input	8.00%
Research and Development Expense \| Assumed Options
Asset Acquisition [Line Items]
Separately recognized expenses				3,100,000
Research and Development Expense \| Severance Payment Obligation
Asset Acquisition [Line Items]
Separately recognized expenses				2,500,000
General and Administrative Expense \| Assumed Options
Asset Acquisition [Line Items]
Separately recognized expenses				1,800,000
General and Administrative Expense \| Severance Payment Obligation
Asset Acquisition [Line Items]
Separately recognized expenses				2,400,000
Non-Accredited Investor \| General and Administrative Expense
Asset Acquisition [Line Items]
Separately recognized expenses				8,387
Former ValenzaBio Employee \| General and Administrative Expense
Asset Acquisition [Line Items]
Separately recognized expenses				$ 30,000
Pierre Fabre
Asset Acquisition [Line Items]
Payments to acquire in-process research and development	$ 10,000,000.0					10,000,000.0
ValenzaBio Asset Acquisition
Asset Acquisition [Line Items]
Shares issued (in shares) \| shares	2,013,673
Share holdback (in shares) \| shares	2,013,673
Shares issued, withholding period	12 months
Asset acquisition payment	$ 7,663
Transaction cost, net	$ 1,200,000
Options exercisable (in shares) \| shares	1,249,811
Option exercisable period	12 months
Options exchange ratio	0.008027010
Research and development	$ 123,100,000					$ 123,100,000
ValenzaBio Asset Acquisition \| Common Class A
Asset Acquisition [Line Items]
Shares issued (in shares) \| shares	18,885,731
ValenzaBio Asset Acquisition \| lonigutamab
Asset Acquisition [Line Items]
Expense related to acquired in-process research and development assets	$ 114,800,000
ValenzaBio Asset Acquisition \| SLRN-517
Asset Acquisition [Line Items]
Expense related to acquired in-process research and development assets	$ 8,200,000

Restructuring (Tables)

9 Months Ended

Sep. 30, 2024

Restructuring and Related Activities [Abstract]

Schedule of Restructuring Liabilities

The following table summarizes the change in the Company’s restructuring liabilities for the nine months ended September 30, 2024 (in thousands):


	Severance and other employee-related benefits		Service cancellation costs		Total
Balance at December 31, 2023	$	—	$	—	$	—
Restructuring charges	$	3,586	$	42,896	$	46,482
Cash payments	$	(1,974)	$	—	$	(1,974)
Revaluation	$	—	$	128	$	128
Balance at September 30, 2024	$	1,612	$	43,024	$	44,636

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current assets
Cash and cash equivalents	$ 216,326	$ 218,097
Short-term marketable securities	346,047	503,229
Prepaid expenses and other current assets	34,216	15,312
Total current assets	596,589	736,638
Prepaid expenses and other assets, non-current	12,498	2,678
Operating lease right-of-use asset	6,979	1,195
Property, plant and equipment, net	1,700	2,179
Restricted cash	544	0
Total assets	618,310	742,690
Current liabilities
Accounts payable	17,550	41,920
Accrued research and development expenses	13,848	35,436
Accrued compensation and other current liabilities	6,683	6,833
Accrued restructuring liabilities	44,636	0
Severance liability	754	970
Total current liabilities	83,471	85,159
Operating lease liability, non-current	6,558	1,194
Total liabilities	90,029	86,353
Stockholders’ equity
Common stock, par value of $0.00001 per share; 790,000,000 shares authorized as of September 30, 2024 and December 31, 2023; 99,944,302 and 97,865,890 shares issued and outstanding as of September 30, 2024 and December 31, 2023, respectively	1	1
Additional paid-in capital	1,185,808	1,144,893
Accumulated other comprehensive income (loss)	384	162
Accumulated deficit	(657,912)	(488,719)
Total stockholders’ equity	528,281	656,337
Total liabilities, redeemable convertible preferred stock and stockholders’ equity	$ 618,310	$ 742,690

Cash, Cash Equivalents, Restricted Cash and Available-For-Sale Marketable Securities - Narrative (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-Sale [Line Items]
Restricted cash	$ 544,000	$ 544,000	$ 0
Allowance for credit loss	0	0
Accrued interest receivable	$ 1,900,000	$ 1,900,000	$ 800,000
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Current, Statement of Financial Position [Extensible Enumeration]	Prepaid expenses and other current assets	Prepaid expenses and other current assets	Prepaid expenses and other current assets
Accrued interest writeoff	$ 0	$ 0
Cash Pledged as Collateral for Stand-by Letter of Credit
Debt Securities, Available-for-Sale [Line Items]
Restricted cash	200,000	200,000
Corporate Credit Card Program
Debt Securities, Available-for-Sale [Line Items]
Restricted cash	$ 300,000	$ 300,000

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

+ Details

ValenzaBio Acquisition - Schedule of Allocation of Purchase Consideration (Details) - ValenzaBio Asset Acquisition $ in Thousands	Jan. 04, 2023 USD ($)
Asset Acquisition [Line Items]
Cash	$ 11,369
Prepaid expenses and other current assets	2,074
In-process research and development assets	123,057
Accounts payable	(1,628)
Accrued research and development expenses	(4,805)
Accrued compensation and other current liabilities	(53)
Total net asset acquired	$ 130,014

Consolidated Balance Sheet Components - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 2,032	$ 2,294
Less: accumulated depreciation and amortization	(332)	(115)
Property, plant and equipment, net	1,700	2,179
Construction in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	0	1,460
Computer and other equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	1,165	407
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	658	306
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 209	$ 121

Cash, Cash Equivalents, Restricted Cash and Available-For-Sale Marketable Securities

9 Months Ended

Sep. 30, 2024

Investments, Debt and Equity Securities [Abstract]

Cash, Cash Equivalents, Restricted Cash and Available-For-Sale Marketable Securities

Cash, cash equivalents and restricted cash


	September 30, 2024		December 31, 2023
Cash and cash equivalents	$	216,326	$	218,097
Restricted cash	544		—
Total cash, cash equivalents and restricted cash	$	216,870	$	218,097

Restricted cash represents cash held at a financial institution that is pledged as collateral for a stand-by letter of credit for $0.2 million for lease commitments and $0.3 million for the Company’s corporate credit card program. The cash will be restricted until the termination or modification of the lease agreement and corporate credit card program, respectively. Restricted cash is included in non-current assets.

Available-for-sale securities marketable securities

The following tables summarize the estimated fair value of the Company’s available-for-sale marketable securities as of September 30, 2024 and December 31, 2023 (in thousands):


As of September 30, 2024:	Total Amortized Cost		Total Unrealized Gain		Total Unrealized Loss		Total Estimated Fair Value

Money market funds (included in cash and cash equivalents)	$	201,253	$	—	$	-	$	201,253
U.S. Treasury obligations ($0 included in cash and cash equivalents)	230,870		248		-		231,118
Corporate debt obligations $1,331 included in cash and cash equivalents)	89,246		65		(7)		89,304
Federal agency obligations ($0 included in cash and cash equivalents)	26,878		79		(1)		26,956
Total available for sale marketable securities	$	548,247	$	392	$	(8)	$	548,631


As of December 31, 2023:	Total Amortized Cost		Total Unrealized Gain		Total Unrealized Loss		Total Estimated Fair Value

Money market funds (included in cash and cash equivalents)	$	23,205	$	—	$	-	$	23,205
U.S. Treasury obligations ($146,497 included in cash and cash equivalents)	525,198		156		(1)		525,353
Corporate debt obligations ($23,313 included in cash and cash equivalents)	135,288		36		(40)		135,284
Federal agency obligations ($15,344 included in cash and cash equivalents)	27,735		12		(1)		27,746
Total available for sale marketable securities	$	711,426	$	204	$	(42)	$	711,588

As of September 30, 2024 and December 31, 2023, no significant facts or circumstances were present to indicate a deterioration in the creditworthiness of the issuers of the marketable securities, and the Company has no requirement or intention to sell these securities before maturity or recovery of their amortized cost basis. The Company considered the current and expected future economic and market conditions and determined that its investments were not significantly impacted. For all securities with a fair value less than its amortized cost basis, the Company determined the decline in fair value below amortized cost basis to be immaterial and non-credit related, and therefore no allowance for losses has been recorded. During the nine months ended September 30, 2024 and for the year ended December 31, 2023, the Company did not recognize any impairment losses on its investments.

The Company presents accrued interest and dividend receivable related to the available-for-sale marketable securities in prepaid expenses and other current assets, separate from short-term investments in the condensed consolidated balance sheet. As of September 30, 2024 and December 31, 2023, accrued interest and dividend receivable was $1.9 million and $0.8 million, respectively. The Company’s accounting policy is to not measure an allowance for credit losses for accrued interest receivables and to write-off any uncollectible accrued interest receivable as a reversal of interest income in a timely manner, which it considers to be in the period in which the Company determines the accrued interest will not be collected. The Company has not written off any accrued interest receivables for the three and nine months ended September 30, 2024.

As of September 30, 2024, all available for sale marketable securities mature within one year.

Common Stock - Narrative (Details)	1 Months Ended		9 Months Ended	12 Months Ended
Common Stock - Narrative (Details)	Dec. 31, 2022 shares	Jul. 31, 2020 $ / shares shares	Sep. 30, 2024 shares	Dec. 31, 2023 shares	May 09, 2023
Class of Stock [Line Items]
Conversion of stock, ratio					1
Common stock, outstanding (in shares)			99,944,302	97,865,890
Stock issued during period, issued for services (in shares)		2,839,749
Sale of stock, price (in dollars per share) \| $ / shares		$ 0.00002
Common Class B
Class of Stock [Line Items]
Common stock, outstanding (in shares)				0
Restricted Stock [Member]
Class of Stock [Line Items]
Vesting period		48 months
Forfeited in period (in shares)	591,613
Shares unvested (in shares)			0	207,060
Vested (in shares)			207,060	354,972

Equity Incentive Plan - Schedule of Valuation Assumptions (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected volatility minimum	83.74%	87.34%	83.74%	75.30%
Expected volatility maximum	84.20%	87.93%	87.76%	92.20%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Risk-free interest rate minimum	3.59%	4.14%	3.59%	3.30%
Risk-free interest rate maximum	3.72%	4.61%	4.52%	4.61%
Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term (in years)	5 years 11 months 12 days	5 years 11 months 12 days	5 years 4 months 28 days	5 years 9 months 7 days
Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term (in years)	6 years 29 days	6 years 14 days	6 years 29 days	6 years 29 days

- Definition

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

+ References

+ Details

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2024

Fair Value Disclosures [Abstract]

Schedule of Financial Instruments Measured on Recurring Basis

The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands):


	Fair Value Measurements as of September 30, 2024
As of September 30, 2024:	Total		Level 1		Level 2		Level 3

Assets:
Money market funds (included in cash and cash equivalents)	$	201,253	$	201,253	$	-	$	-
U.S. Treasury obligations ($0 included in cash and cash equivalents)	231,118		-		231,118		-
Corporate debt obligations ($1,331 included in cash and cash equivalents)	89,304		-		89,304		-
Federal agency obligations ($0 included in cash and cash equivalents)	26,956		-		26,956		-
Total fair value of assets	$	548,631	$	201,253	$	347,378	$	-


	Fair Value Measurements as of December 31, 2023
As of December 31, 2023:	Total		Level 1		Level 2		Level 3

Assets:
Money market funds (included in cash and cash equivalents)	$	23,205	$	23,205	$	-	$	-
U.S. Treasury obligations ($146,497 included in cash and cash equivalents)	525,353		-		525,353		-
Corporate debt obligations ($23,313 included in cash and cash equivalents)	135,284		-		135,284		-
Federal agency obligations ($15,344 included in cash and cash equivalents)	27,746		-		27,746		-
Total fair value of assets	$	711,588	$	23,205	$	688,383	$	-


Classified as:	September 30, 2024		December 31, 2023
Cash and cash equivalents	$	202,584	$	208,359
Short-term marketable securities	$	346,047	$	503,229
Total cash equivalents and marketable securities	$	548,631	$	711,588

Fair Value Measurements - Schedule of Financial Instruments Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Assets:
Money market funds (included in cash and cash equivalents)	$ 548,631	$ 711,588
Total fair value of assets	548,631	711,588
Cash and cash equivalents
Assets:
Money market funds (included in cash and cash equivalents)	202,584	208,359
Money market funds (included in cash and cash equivalents)
Assets:
Money market funds (included in cash and cash equivalents)	201,253	23,205
U.S. Treasury obligations
Assets:
Money market funds (included in cash and cash equivalents)	231,118	525,353
U.S. Treasury obligations \| Cash and cash equivalents
Assets:
Money market funds (included in cash and cash equivalents)	0	146,497
Corporate debt obligations
Assets:
Money market funds (included in cash and cash equivalents)	89,304	135,284
Corporate debt obligations \| Cash and cash equivalents
Assets:
Money market funds (included in cash and cash equivalents)	1,331	23,313
Federal agency obligations
Assets:
Money market funds (included in cash and cash equivalents)	26,956	27,746
Federal agency obligations \| Cash and cash equivalents
Assets:
Money market funds (included in cash and cash equivalents)	0	15,344
Level 1
Assets:
Total fair value of assets	201,253	23,205
Level 1 \| Money market funds (included in cash and cash equivalents)
Assets:
Money market funds (included in cash and cash equivalents)	201,253	23,205
Level 1 \| U.S. Treasury obligations
Assets:
Money market funds (included in cash and cash equivalents)	0	0
Level 1 \| Corporate debt obligations
Assets:
Money market funds (included in cash and cash equivalents)	0	0
Level 1 \| Federal agency obligations
Assets:
Money market funds (included in cash and cash equivalents)	0	0
Level 2
Assets:
Total fair value of assets	347,378	688,383
Level 2 \| Money market funds (included in cash and cash equivalents)
Assets:
Money market funds (included in cash and cash equivalents)	0	0
Level 2 \| U.S. Treasury obligations
Assets:
Money market funds (included in cash and cash equivalents)	231,118	525,353
Level 2 \| Corporate debt obligations
Assets:
Money market funds (included in cash and cash equivalents)	89,304	135,284
Level 2 \| Federal agency obligations
Assets:
Money market funds (included in cash and cash equivalents)	26,956	27,746
Level 3
Assets:
Total fair value of assets	0	0
Level 3 \| Money market funds (included in cash and cash equivalents)
Assets:
Money market funds (included in cash and cash equivalents)	0	0
Level 3 \| U.S. Treasury obligations
Assets:
Money market funds (included in cash and cash equivalents)	0	0
Level 3 \| Corporate debt obligations
Assets:
Money market funds (included in cash and cash equivalents)	0	0
Level 3 \| Federal agency obligations
Assets:
Money market funds (included in cash and cash equivalents)	$ 0	$ 0

Fair Value Measurements - Schedule of Cash and Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	$ 548,631	$ 711,588
Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	202,584	208,359
Short-term marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	$ 346,047	$ 503,229

Condensed Consolidated Statements of Cash Flows (Parenthetical)	9 Months Ended
	Sep. 30, 2023 shares
Statement of Cash Flows [Abstract]
Conversion of redeemable convertible preferred stock into common stock in connection with initial public offering (in shares)	40,743,522

Other Income (Details) - USD ($)	1 Months Ended		9 Months Ended
Other Income (Details) - USD ($)	Mar. 31, 2024	Jan. 31, 2024	Sep. 30, 2024	Sep. 30, 2023
Other Income and Expenses [Abstract]
Other nonrecurring income	$ 30,000,000.0		$ 30,000,000
Research and development expense, vendor service credit	$ 5,000,000.0		5,000,000
Income from sale of asset		$ 7,000,000.0	7,000,000
Disposal group, including discontinued operation, consideration			$ 157,500,000

ValenzaBio Acquisition (Tables)

9 Months Ended

Sep. 30, 2024

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

Schedule of Asset Acquisition

The following table represents the total purchase consideration (in thousands):


Issued Class A Common Stock (1)	$	128,735
Transaction costs (2)	1,271
Cash (3)	8
Total	$	130,014

(1)Shares were issued for consideration at $6.86 per share, including 2,013,673 shares that were being held by Seller LLC until the Holdback Release Date. The Company used a third party valuation specialist to assist management in determining the fair value of the shares of Class A Common Stock at the Closing Date.

(2)Legal and advisory transaction costs of $1.3 million incurred by the Company in connection with the Acquisition, including $0.1 million payable in cash to Seller LLC for the expense fund.

(3)Cash payment of $7,663 to one non-accredited investor for settlement of vested ValenzaBio options.

The following is the allocation of the purchase consideration to the acquired assets and liabilities (in thousands):


Cash	$	11,369
Prepaid expenses and other current assets	2,074
In-process research and development assets	123,057
Accounts payable	(1,628)
Accrued research and development expenses	(4,805)
Accrued compensation and other current liabilities	(53)
Total net asset acquired	$	130,014

Net Loss Per Share Attributable to Common Stockholders

9 Months Ended

Sep. 30, 2024

Earnings Per Share [Abstract]

Net Loss Per Share Attributable to Common Stockholders

The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share data):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Numerator:
Net loss	$	(48,548)	$	(83,940)	$	(169,193)	$	(286,429)
Denominator:
Weighted average common shares outstanding	99,835,707		97,227,070		99,050,167		61,580,296
Less: Weighted-average common shares subject to repurchase	0		(354,323)		(76,649)		(442,191)
Weighted-average common shares outstanding, basic and diluted	99,835,707		96,872,747		98,973,518		61,138,105
Net loss per share attributable to common stockholders, basic and diluted	$	(0.49)	$	(0.87)	$	(1.71)	$	(4.68)


	As of September 30,
	2024	2023
Outstanding options to purchase common stock	14,071,995	8,704,462
Unvested RSUs outstanding	1,204,470	2,183,413
Unvested PSUs expected to vest	178,404	—
Outstanding options to purchase common stock assumed upon acquisition of ValenzaBio	55,311	1,249,811
Common stock subject to repurchase	—	295,803
ESPP	108,048	—
Total	15,618,228	12,433,489

The PSUs included above represent the expected payout at the reporting date under the current performance vesting conditions assessment (see Note 10).

Commitments and Contingent Liabilities (Tables)

9 Months Ended

Sep. 30, 2024

Commitments and Contingencies Disclosure [Abstract]

Schedule of Lessee, Operating Lease, Liability, to be Paid, Maturity

The following table summarizes a maturity analysis of the Company’s operating lease liabilities showing the aggregate lease payments as of September 30, 2024 (in thousands):


2024 (remainder of the year)	$	394
2025	2,200
2026	2,275
2027	2,352
2028	2,291
2029	1,548
Total future lease payments	11,060
Less imputed interest	(3,678)
Total operating lease liability balance	7,382
Less current portion of lease liability	(824)
Operating lease liability, non-current	$	6,558

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Gain (Loss)
Beginning balance (in shares) at Dec. 31, 2022	40,743,522
Beginning balance at Dec. 31, 2022	$ 396,593
Ending balance (in shares) at Mar. 31, 2023	40,743,522
Ending balance at Mar. 31, 2023	$ 396,593
Beginning balance (in shares) at Dec. 31, 2022		2,767,359
Beginning balance at Dec. 31, 2022	(102,862)	$ 0	$ 4,302	$ (107,078)	$ (86)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with ValenzaBio acquisition (in shares)		18,885,731
Issuance of common stock in connection with ValenzaBio acquisition	128,735		128,735
Stock-based compensation expense	7,139		7,139
Net loss	(176,450)			(176,450)
Unrealized gain (losses) on short-term marketable securities, net	86				86
Ending balance (in shares) at Mar. 31, 2023		21,653,090
Ending balance at Mar. 31, 2023	$ (143,352)	$ 0	140,176	(283,528)	0
Beginning balance (in shares) at Dec. 31, 2022	40,743,522
Beginning balance at Dec. 31, 2022	$ 396,593
Ending balance (in shares) at Sep. 30, 2023	0
Ending balance at Sep. 30, 2023	$ 0
Beginning balance (in shares) at Dec. 31, 2022		2,767,359
Beginning balance at Dec. 31, 2022	$ (102,862)	$ 0	4,302	(107,078)	(86)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of redeemable convertible preferred stock into common stock in connection with initial public offering (in shares)	40,743,522
Net loss	$ (286,429)
Unrealized gain (losses) on short-term marketable securities, net	36
Ending balance (in shares) at Sep. 30, 2023		97,240,419
Ending balance at Sep. 30, 2023	$ 732,376	$ 1	1,125,932	(393,507)	(50)
Beginning balance (in shares) at Mar. 31, 2023	40,743,522
Beginning balance at Mar. 31, 2023	$ 396,593
Redeemable Convertible Preferred Stock
Conversion of redeemable convertible preferred stock into common stock in connection with initial public offering (in shares)	(40,743,522)
Conversion of redeemable convertible preferred stock into common stock in connection with initial public offering	$ (396,593)
Ending balance (in shares) at Jun. 30, 2023	0
Ending balance at Jun. 30, 2023	$ 0
Beginning balance (in shares) at Mar. 31, 2023		21,653,090
Beginning balance at Mar. 31, 2023	(143,352)	$ 0	140,176	(283,528)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon initial public offering, net of underwriting discounts commissions and issuance costs (in shares)		34,500,000
Issuance of common stock upon initial public offering, net of underwriting discounts commissions and issuance costs of $47,354	573,644		573,644
Conversion of redeemable convertible preferred stock into common stock in connection with initial public offering (in shares)		40,743,522
Conversion of redeemable convertible preferred stock into common stock in connection with initial public offering	396,593	$ 1	396,592
Issuance of common stock upon settlement of restricted stock units, net of shares withheld for taxes (in shares)		303,237
Issuance of common stock upon settlement of restricted stock units, net of shares withheld for taxes	(8,325)		(8,325)
Stock-based compensation expense	8,501		8,501
Net loss	(26,039)			(26,039)
Unrealized gain (losses) on short-term marketable securities, net	44				44
Ending balance (in shares) at Jun. 30, 2023		97,199,849
Ending balance at Jun. 30, 2023	$ 801,066	$ 1	1,110,588	(309,567)	44
Ending balance (in shares) at Sep. 30, 2023	0
Ending balance at Sep. 30, 2023	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	15,313		15,313
Issuance of common stock upon exercise of options (in shares)		40,570
Issuance of common stock upon exercise of options	31		31
Net loss	(83,940)			(83,940)
Unrealized gain (losses) on short-term marketable securities, net	(94)				(94)
Ending balance (in shares) at Sep. 30, 2023		97,240,419
Ending balance at Sep. 30, 2023	$ 732,376	$ 1	1,125,932	(393,507)	(50)
Beginning balance (in shares) at Dec. 31, 2023	0
Beginning balance at Dec. 31, 2023	$ 0
Ending balance (in shares) at Mar. 31, 2024	0
Ending balance at Mar. 31, 2024	$ 0
Beginning balance (in shares) at Dec. 31, 2023	97,865,890	97,865,890
Beginning balance at Dec. 31, 2023	$ 656,337	$ 1	1,144,893	(488,719)	162
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon settlement of restricted stock units (in shares)		47,639
Stock-based compensation expense	20,163		20,163
Issuance of common stock upon exercise of options (in shares)		945,471
Issuance of common stock upon exercise of options	2,807		2,807
Net loss	(34,973)			(34,973)
Unrealized gain (losses) on short-term marketable securities, net	(267)				(267)
Ending balance (in shares) at Mar. 31, 2024		98,859,000
Ending balance at Mar. 31, 2024	$ 644,067	$ 1	1,167,863	(523,692)	(105)
Beginning balance (in shares) at Dec. 31, 2023	0
Beginning balance at Dec. 31, 2023	$ 0
Ending balance (in shares) at Sep. 30, 2024	0
Ending balance at Sep. 30, 2024	$ 0
Beginning balance (in shares) at Dec. 31, 2023	97,865,890	97,865,890
Beginning balance at Dec. 31, 2023	$ 656,337	$ 1	1,144,893	(488,719)	162
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of options (in shares)	511,255
Net loss	$ (169,193)
Unrealized gain (losses) on short-term marketable securities, net	$ 222
Issuance of common stock under the employee stock purchase plan (in shares)	100,827
Ending balance (in shares) at Sep. 30, 2024	99,944,302	99,944,302
Ending balance at Sep. 30, 2024	$ 528,281	$ 1	1,185,808	(657,912)	384
Beginning balance (in shares) at Mar. 31, 2024	0
Beginning balance at Mar. 31, 2024	$ 0
Ending balance (in shares) at Jun. 30, 2024	0
Ending balance at Jun. 30, 2024	$ 0
Beginning balance (in shares) at Mar. 31, 2024		98,859,000
Beginning balance at Mar. 31, 2024	644,067	$ 1	1,167,863	(523,692)	(105)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon settlement of restricted stock units, net of shares withheld for taxes (in shares)		459,808
Issuance of common stock upon settlement of restricted stock units, net of shares withheld for taxes	(1,937)		(1,937)
Stock-based compensation expense	10,174		10,174
Issuance of common stock upon exercise of options (in shares)		150,786
Issuance of common stock upon exercise of options	1,289		1,289
Net loss	(85,672)			(85,672)
Unrealized gain (losses) on short-term marketable securities, net	(62)				(62)
Issuance of common stock under the employee stock purchase plan (in shares)		100,827
Issuance of common stock under the employee stock purchase plan	359		359
Ending balance (in shares) at Jun. 30, 2024		99,570,421
Ending balance at Jun. 30, 2024	$ 568,218	$ 1	1,177,748	(609,364)	(167)
Ending balance (in shares) at Sep. 30, 2024	0
Ending balance at Sep. 30, 2024	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon settlement of restricted stock units, net of shares withheld for taxes (in shares)		75,754
Stock-based compensation expense	7,054		7,054
Issuance of common stock upon exercise of options (in shares)		298,127
Issuance of common stock upon exercise of options	1,006		1,006
Net loss	(48,548)			(48,548)
Unrealized gain (losses) on short-term marketable securities, net	$ 551				551
Issuance of common stock under the employee stock purchase plan (in shares)	0
Ending balance (in shares) at Sep. 30, 2024	99,944,302	99,944,302
Ending balance at Sep. 30, 2024	$ 528,281	$ 1	$ 1,185,808	$ (657,912)	$ 384

Summary of Significant Accounting Policies	9 Months Ended
Summary of Significant Accounting Policies	Sep. 30, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies The accounting policies used by the Company in its presentation of interim financial results are consistent with those presented in Note 2 to the consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023, filed with the Securities and Exchange Commission (“SEC”) on March 28, 2024, (the “Annual Report on Form 10-K”) except for the updates to the following: Basis of Presentation The condensed consolidated financial statements and accompanying notes are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the SEC regarding interim financial reporting. The accompanying financial statements are consolidated and include the accounts of ACELRYIN, INC. and its wholly owned subsidiary, WH2, LLC. The subsidiary has not had any operations or any balances from its inception. Certain information and footnote disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2023 included in the Company’s Annual Report. The information as of December 31, 2023 included in the condensed consolidated balance sheets was derived from the Company’s audited consolidated financial statements. These unaudited interim condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments necessary for a fair statement of the Company’s consolidated financial statements. The results of operations for the three and nine months ended September 30, 2024 are not necessarily indicative of the results that may be expected for the year ending December 31, 2024 or for any other interim period or for any other future year. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates estimates and assumptions, including but not limited to those related to the fair value of its derivative tranche liability, the fair value of its common stock, stock-based compensation expense, accruals for research and development expenses, valuation of deferred tax assets, and uncertain income tax positions. Management bases its estimates on historical experience and on various other assumptions that are 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 that are not readily apparent from other sources. Actual results may differ materially from those estimates. Concentration of Credit Risk Cash, cash equivalents, restricted cash and short-term marketable securities are financial instruments that potentially subject the Company to concentrations of credit risk. As of September 30, 2024 and December 31, 2023, cash consists of cash deposited with one financial institution, and account balances exceed federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial strength of this institution. The Company also has investments in money market funds, U.S. Treasury obligations, corporate debt obligations, and federal agency obligations, which can be subject to certain credit risks. The Company mitigates the risks by investing in high-grade instruments, limiting its exposure to any one issuer and monitoring the ongoing creditworthiness of the financial institutions and issuers. The Company has not experienced any losses on its financial instruments. Restructuring The Company accounts for exit or disposals costs in accordance with ASC 420, Exit or Disposal Cost Obligations. Charges represent expenses incurred in connection with certain exit or disposal activities and consist of the costs of contract termination, employee termination and other activities. A liability for costs associated with an exit or disposal activity is measured at its fair value when the liability is incurred. Long-lived Assets Impairment Assessment Long-lived assets, including operating lease assets, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. The recoverability of assets to be held and used is measured by a comparison of the carrying amount of the asset group to future net cash flows estimated by the Company to be generated by such assets. If such asset group is considered to be impaired, the impairment to be recognized is the amount by which the carrying amount of the asset group exceeds the fair value of the asset group. During the three months ended September 30, 2024, the Company performed an evaluation of the impact of the August 2024 Restructuring Plan on the carrying value of its long-lived assets and concluded that there was no impairment charge to be recognized on the long-lived assets.

Common Stock

9 Months Ended

Sep. 30, 2024

Equity [Abstract]

Common Stock

On May 9, 2023, immediately prior to the IPO closing, each share of the Company’s Class A Common Stock then issued and outstanding was reclassified and became one share of the Company’s common stock. As of December 31, 2023, there were no shares of Class B Common Stock outstanding.

As of September 30, 2024 and December 31, 2023, Common Stock reserved for future issuance by the Company was as follows:


	September 30,	December 31,
	2024	2023
Shares available for future grants under Equity Incentive Plan	6,016,568	3,526,392
Outstanding stock options	14,071,995	9,630,623
Performance-based restricted stock units1	792,908	2,964,072
Outstanding restricted stock units	1,204,470	2,166,016
Options assumed upon ValenzaBio acquisition	55,311	938,440
ESPP Shares available for future grants	1,753,667	875,836
Total shares reserved for future issuance	23,894,919	20,101,379

1. The performance-based restricted stock units balance is based on the target number of shares.

Founders’ Common Stock

On the IPO closing date, each share of the founders’ Class A common stock issued and outstanding was reclassified and became one share of the Company’s common stock; no vesting or other terms were modified.

In July 2020, the Company issued 2,839,749 shares of its common stock to founders at a price of $0.00002 per share. The issuance price was the estimated fair value of the shares as the shares were issued at inception and no intellectual property was contributed by the founders. The founders have voting rights and rights to receive dividends regardless of the vesting of the shares. Issued shares vested monthly over 48 months, as founders continued providing services to the Company. The Company had the right to repurchase unvested shares at the price paid by the founders if services are terminated. Stock-based compensation expense was minimal for these shares. In December 2022, the Company repurchased 591,613 restricted common shares at the original purchase price that were unvested as of the date of repurchase in connection with one founder’s resignation. As of September 30, 2024 and December 31, 2023, zero and 207,060 shares were unvested, respectively. During the nine months ended September 30, 2024 and year ended December 31, 2023, 207,060 and 354,972 founders’ shares vested.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (h)
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-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
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-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478448/946-505-50-6

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480237/815-40-50-6

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/505/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
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-Paragraph 13
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-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Section 50
-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

+ Details

ValenzaBio Acquisition

9 Months Ended

Sep. 30, 2024

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

ValenzaBio Acquisition

On December 20, 2022, the Company entered into the Agreement and the Plan of Merger and Reorganization (the “Merger Agreement”) to acquire ValenzaBio. In connection with the planned ValenzaBio acquisition, the Company formed two wholly owned subsidiaries, WH1, Inc. and WH2 LLC in November 2022. Through the two-step merger and restructuring, WH1 Inc. was merged with and into ValenzaBio with WH1 Inc. ceasing to exist, and ValenzaBio was then merged with and into WH2 LLC, with WH2 LLC continuing as the legal successor to ValenzaBio. (the “Acquisition”). The Acquisition closed on January 4, 2023 (the “Closing Date”).

The Company concluded that the Acquisition is an asset acquisition as substantially all of the fair value of the gross assets acquired, excluding cash, was concentrated in a single asset, lonigutamab, and the Company did not acquire a workforce or any substantive process capable of significantly contributing to the ability to create outputs.

As consideration, the Company issued 18,885,731 shares of its Class A Common Stock to ValenzaBio stockholders, of which 2,013,673 were being held by Seller LLC for any post-acquisition costs and general indemnities for 12 months from the Closing Date (“Holdback Release Date”), and paid $7,663 in cash to one non-accredited investor. The Company also incurred $1.2 million of acquisition-related costs that were included in the total consideration and capitalized to assets acquired.

The Company assumed options of certain ValenzaBio option holders who entered into consulting agreements with the Company, which became options for the purchase of an aggregate 1,249,811 shares of the Company’s Class A Common Stock upon the closing of the Acquisition on January 4, 2023. The assumed options vested in full on March 31, 2023. Each assumed option is exercisable until the earlier of (i) 12 months following the termination of the option holder’s continuous service with the Company, or (ii) the original expiration date of such assumed option.

Outstanding ValenzaBio shares were exchanged into shares of the Company’s Class A Common Stock and the options described above assumed at an exchange ratio of 0.8027010-for-one.

The following table represents the total purchase consideration (in thousands):


Issued Class A Common Stock (1)	$	128,735
Transaction costs (2)	1,271
Cash (3)	8
Total	$	130,014

(2)Legal and advisory transaction costs of $1.3 million incurred by the Company in connection with the Acquisition, including $0.1 million payable in cash to Seller LLC for the expense fund.

(3)Cash payment of $7,663 to one non-accredited investor for settlement of vested ValenzaBio options.

The following is the allocation of the purchase consideration to the acquired assets and liabilities (in thousands):


Cash	$	11,369
Prepaid expenses and other current assets	2,074
In-process research and development assets	123,057
Accounts payable	(1,628)
Accrued research and development expenses	(4,805)
Accrued compensation and other current liabilities	(53)
Total net asset acquired	$	130,014

In-process research and development (“IPR&D”) assets were related to acquired product candidates: lonigutamab in clinical trials and SLRN-517 in preclinical development. The fair value of in-process research and development assets was based on the present value of future discounted cash flows, which was based on significant estimates. These estimates included the number of potential patients and market prices of future product candidates, costs required to conduct clinical trials, future milestones and royalties payable under acquired license agreements, costs to receive regulatory approval and potentially commercialize product candidates, as well as estimates for probability of success and the discount rate. The estimated fair values of lonigutamab and SLRN-517 assets were $114.8 million and $8.2 million, respectively. The Company concluded that acquired assets do not have an alternative future use and recognized the full amount of $123.1 million as research and development expenses in the condensed consolidated statement of operations and comprehensive loss in January 2023.

There are a number of additional obligations under the Merger Agreement that are separate from the assets and liabilities acquired, including the following:

Assumed options. The assumed options, discussed above, did not have substantive service requirement, and were accounted as a separate transaction from the Acquisition. The fair values of assumed options of $3.1 million and $1.8 million was expensed as research and development and general and administrative expenses, respectively, in the condensed consolidated statement of operations and comprehensive loss for the three months ended March 31, 2023.

Settled equity awards. In accordance with the severance obligations of ValenzaBio and per the terms of the Merger Agreement, certain unvested options and restricted stock awards of former ValenzaBio employees, who did not enter into consulting agreements with the Company, were accelerated and net exercised upon the closing of the Acquisition and termination of employment of such ValenzaBio employees. The fair value of unvested equity awards of $0.9 million was expensed as general and administrative expense in the condensed consolidated statement of operations and comprehensive loss for the three months ended March 31, 2023. Payments in cash to one non-accredited investor for settlement of unvested ValenzaBio options and one former ValenzaBio employee to whom options were promised but not granted at the Closing Date of $8,387 and $30,000, respectively, were expensed as general and administrative expenses in the condensed consolidated statement of operations and comprehensive loss for the three months ended March 31, 2023.

Severance payment obligation. In accordance with the severance plan of ValenzaBio, the Company was obligated to make severance payments to certain former ValenzaBio employees of approximately $5.1 million, including estimated taxes, for a period of three to 18 months from the Closing Date, depending on the position and tenure of such employees with ValenzaBio. The Company recognized the estimated fair value of severance payments obligations of $2.5 million and $2.4 million at the Closing Date as research and development and general and administrative expenses, respectively, in the condensed consolidated statement of operations and comprehensive loss for the three months ended March 31, 2023. The fair value of severance payments obligations was estimated based on future expected cash flows discounted to the Closing Date and a discount rate of 8%. The Company will accrete the fair value of severance payments obligations to the amounts payable over the obligation period as either research and development or general and administrative expenses based on the former employees’ functional department.

As of September 30, 2024, no ValenzaBio severance plan payments obligations were outstanding to ValenzaBio employees. As of December 31, 2023, ValenzaBio severance plan payments obligations of $0.3 million were included in the condensed consolidated balance sheets.

Amendment to Pierre Fabre Agreement. The Company, ValenzaBio and Pierre Fabre Medicament SAS (“Pierre Fabre”) entered into an amendment to the license and commercialization agreement, which became effective on the Closing Date. The Company paid a $10.0 million non-refundable license fee to Pierre Fabre. See Note 7 for additional details.