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v3.25.3

Acquisitions (Details) $ / shares in Units, $ in Thousands |  |  | 3 Months Ended | 4 Months Ended | 9 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
May 21, 2025 USD ($) installment lease $ / shares shares | Mar. 29, 2024 $ / shares | Sep. 30, 2025 USD ($) shares | Sep. 30, 2024 USD ($) | Sep. 30, 2025 USD ($) shares | Sep. 30, 2025 USD ($) shares | Sep. 30, 2024 USD ($) | Dec. 31, 2025 USD ($) | Jan. 31, 2025 | Dec. 31, 2024 shares
Acquisitions |  |  |  |  |  |  |  |  |  |
Stock option, exercise price ($ per share) | $ / shares |  | $ 8.84 |  |  |  |  |  |  |  |
Common stock reserved for future issuance | shares |  |  | 31,348,966 |  | 31,348,966 | 31,348,966 |  |  |  | 17,095,105
Net income (loss) |  |  | $ (104,452) | $ (141,667) |  | $ (380,973) | $ (222,102) |  |  |
Gain on bargain purchase |  |  |  |  |  | 187,907 |  |  |  |
Severance liability |  |  | 1,374 |  | $ 1,374 | $ 1,374 |  |  |  |
RSUs |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Shares issued for conversion | shares |  |  |  |  |  | 1,470,868 |  |  |  |
ACELYRIN |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Number of shares issued in exchange | shares | 48,653,549 |  |  |  |  |  |  |  |  |
Stock option, exercise price ($ per share) | $ / shares | $ 18 |  |  |  |  |  |  |  |  |
Exchange ratio | 0.4814 |  |  |  |  |  |  |  |  |
Merger transaction costs |  |  | (100) |  |  | $ 14,700 |  |  |  |
Fair value of IPR&D asset | $ 50,959 |  |  |  |  |  |  |  |  |
Credit voucher acquired, balance | $ 11,400 |  |  |  |  |  |  |  |  |
Number of operating leases acquired | lease | 2 |  |  |  |  |  |  |  |  |
Lease liability fair value adjustment, short term portion | $ 200 |  |  |  |  |  |  |  |  |
Lease liability fair value adjustment, long term portion | 500 |  |  |  |  |  |  |  |  |
Right of use asset fair value adjustment | 100 |  |  |  |  |  |  |  |  |
Gain on bargain purchase | 187,907 |  | 0 |  |  | 187,900 |  |  |  |
Deferred income tax liability | 10,701 |  |  |  |  |  |  |  |  |
Additional stock-based compensation |  |  | 2,100 |  |  | 12,900 |  |  |  |
Revenue of acquiree |  |  |  |  | 0 |  |  |  |  |
Operating losses of acquiree |  |  |  |  | 14,200 |  |  |  |  |
ACELYRIN | Acquisition related cost |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Merger transaction costs |  |  |  | 0 |  |  | 14,700 |  |  |
ACELYRIN | Stock based compensation |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Net income (loss) |  |  |  |  |  |  | 13,100 |  |  |
ACELYRIN | Stock based compensation | Less than |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Net income (loss) |  |  |  | 100 |  |  |  |  |  |
ACELYRIN | Gain on bargain purchase |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Net income (loss) |  |  |  | 0 |  |  | 187,900 |  |  |
ACELYRIN | General and administrative expenses |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Merger transaction costs |  |  | (100) |  |  | 14,700 |  |  |  |
ACELYRIN | Severance Plan |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Severance cash obligations | $ 13,500 |  |  |  |  |  |  |  |  |
Severance cash obligations payment period | 12 months |  |  |  |  |  |  |  |  |
Severance cost |  |  | 4,300 |  |  | 13,200 |  |  |  |
Severance liability |  |  | 1,400 |  | $ 1,400 | 1,400 |  |  |  |
Additional stock-based compensation |  |  |  |  |  |  |  | $ 13,100 |  |
ACELYRIN | Severance Plan | Severance cash obligations |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Net income (loss) |  |  |  | $ 0 |  |  | $ 13,500 |  |  |
ACELYRIN | Severance Plan | General and administrative expenses |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Severance cost |  |  | 1,900 |  |  | 7,100 |  |  |  |
Additional stock-based compensation |  |  | 1,000 |  |  | 8,800 |  |  |  |
ACELYRIN | Severance Plan | Research and development expenses |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Severance cost |  |  | 2,400 |  |  | 6,100 |  |  |  |
Additional stock-based compensation |  |  | $ 1,100 |  |  | $ 4,100 |  |  |  |
ACELYRIN | IPR&D asset |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Fair value of IPR&D asset | $ 51,000 |  |  |  |  |  |  |  |  |
Discount rate | 23.00% |  |  |  |  |  |  |  |  |
Deferred income tax liability | $ 10,700 |  |  |  |  |  |  |  |  |
ACELYRIN | RSUs |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Shares issued for conversion | shares | 1,323,905 |  |  |  |  |  |  |  |  |
ACELYRIN | Performance based RSU |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Shares issued for conversion | shares | 146,963 |  |  |  |  |  |  |  |  |
Percentage of performance conditions achieved | 100.00% |  |  |  |  |  |  |  |  |
ACELYRIN | Performance based RSU | Merger closes before May 15, 2025 |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Number of installments | installment | 2 |  |  |  |  |  |  |  |  |
ACELYRIN | ACELYRIN Plans |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Common stock reserved for future issuance | shares | 4,712,186 |  |  |  |  |  |  |  |  |
Legacy Alumis Inc |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Percentage of equity owned |  |  |  |  |  |  |  |  | 52.00% |
Legacy Acelyrin Inc |  |  |  |  |  |  |  |  |  |
Acquisitions |  |  |  |  |  |  |  |  |  |
Percentage of equity owned |  |  |  |  |  |  |  |  | 48.00% |

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