Income Taxes - Net deferred tax assets (Details) - USD ($) $ in Thousands |
Dec. 31, 2022 |
Dec. 31, 2021 |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|---|---|
| Deferred tax assets: | ||||
| Net operating loss carryforwards | $ 159,691 | $ 145,990 | ||
| Research and development tax credit carryforwards | 45,478 | 36,161 | ||
| Accrued expenses | 105 | 2,137 | ||
| Capitalized intellectual property costs | 2,051 | 1,746 | ||
| Capitalized research and development expense | 32,007 | 86 | ||
| Operating lease liabilities | 301 | 10,194 | ||
| Stock‑based compensation expense | 24,454 | 21,483 | ||
| Depreciation | 74 | 0 | ||
| Total deferred tax assets | 264,161 | 217,797 | ||
| Deferred tax liabilities: | ||||
| Operating lease assets | (732) | (9,590) | ||
| Depreciation and other | 0 | (1,500) | ||
| Total deferred tax liabilities | (732) | (11,090) | ||
| Valuation allowance | (263,429) | (206,707) | $ (139,877) | $ (85,884) |
| Net deferred tax assets | $ 0 | $ 0 |