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Stockholders' Equity (Tables) | 9 Months Ended
--- | ---
Sep. 30, 2025
Stockholders' Equity |
Schedule of common stock reserved for issuance, on an as-converted basis | ​
​ | ​ | ​ | ​ | ​
​ |  | September 30, |  | December 31,
​ | ​ | 2025 | ​ | 2024
Stock options issued and outstanding |  | 20,090,359 |  | 9,458,788
RSUs issued and outstanding | ​ | 2,670,905 | ​ | —
Shares available for grant under the 2024 Equity Incentive Plan | ​ | 930,301 | ​ | 6,893,517
Shares available for grant under the 2024 Employee Stock Purchase Plan | ​ | 1,009,440 | ​ | 650,000
Shares available for grant under the ACELYRIN, Inc. 2023 Equity Incentive Plan | ​ | 6,448,105 | ​ | —
Shares available for grant under the 2024 Performance Option Plan | ​ | 199,856 | ​ | 92,800
Total |  | 31,348,966 |  | 17,095,105
Schedule of summarizes the activity for the company's restricted common stock | ​
​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | Weighted-
​ | ​ | ​ | ​ | Average
​ | ​ | Number of | ​ | Grant Date
​ | ​ | Shares | ​ | Fair Value
Unvested as of December 31, 2024 |  | 2,583 | ​ | $ | 2.90
Vested |  | (2,583) | ​ | $ | 2.90
Unvested as of September 30, 2025 |  | — | ​ | $ | —
​

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- Definition Tabular disclosure of common stock reserved for issuance, on an as-converted basis. + References No definition available. + Details
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- Definition Tabular disclosure of the changes in outstanding nonvested restricted stock shares. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Subparagraph (c) -Paragraph 2 -SubTopic 10 -Topic 718 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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