| Dec 31, 2019 | Dec 31, 2020 | Dec 31, 2021 | Dec 31, 2022 | Dec 31, 2023 | Dec 31, 2024 |
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| Cash and cash equivalents | 90 | 50 | 329 | 154 | 75 | 33 |
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| Marketable securities | 263 | 363 | 406 | 559 | 474 | 380 |
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| Prepaid expenses and other current assets | 4 | 8 | 7 | 11 | 17 | 11 |
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| Total current assets | 357 | 422 | 750 | 726 | 566 | 425 |
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| Property and equipment, net | 34 | 30 | 27 | 26 | 22 | 17 |
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| Operating lease right-of-use assets | 28 | 32 | 31 | 28 | 25 | 20 |
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| Restricted cash | 1 | 1 | 2 | 2 | 2 | 2 |
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| Other assets | 1 | 3 | 6 | 6 | 7 | 5 |
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| Total assets | 422 | 488 | 815 | 788 | 622 | 468 |
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| Accounts payable | 0 | 3 | 5 | 4 | 4 | 2 |
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| Accrued Clinical Supply Cost | 7 | 11 | 9 | 6 | 5 | 7 |
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| Accrued liabilities | 18 | 23 | 27 | 28 | 30 | 29 |
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| Deferred revenue, current portion | 30 | 24 | 91 | 48 | 83 | 24 |
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| Collaboration Payable | - | - | - | - | 8 | 6 |
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| Contract with Customer, Refund Liability, Current | - | - | - | - | 39 | 49 |
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| Operating Lease, Liability, Current | 7 | 8 | 8 | 8 | 8 | 9 |
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| Total current liabilities | 62 | 68 | 140 | 94 | 178 | 125 |
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| Deferred revenue, long-term portion | 123 | 108 | 334 | 443 | 211 | 172 |
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| Long-term debt | - | - | - | - | - | 9 |
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| Contract with Customer, Refund Liability, Noncurrent | - | - | - | - | 67 | 9 |
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| Operating Lease, Liability, Noncurrent | 41 | 44 | 40 | 35 | 30 | 24 |
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| Other long-term liabilities | 0 | 0 | 0 | 1 | 1 | 1 |
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| Total liabilities | 227 | 221 | 514 | 573 | 488 | 342 |
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| Common Stock, Value, Issued | 0 | 0 | 0 | 0 | 0 | 0 |
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| Additional paid-in capital | 414 | 677 | 748 | 799 | 844 | 956 |
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| Accumulated other comprehensive income | 0 | 1 | -1 | -5 | 0 | 0 |
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| Accumulated deficit | -220 | -410 | -446 | -580 | -710 | -829 |
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| Total stockholders' equity | 195 | 268 | 301 | 214 | 134 | 127 |
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| Total liabilities and stockholders' equity | 422 | 488 | 815 | 788 | 622 | 468 |
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