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Income Taxes (Tables) | 12 Months Ended
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Dec. 31, 2021
Income Tax Disclosure [Abstract] |
Summary of Reconciliation of U.S. Federal Statutory Income Tax Rate to Company’s Effective Income Tax Rate | A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:
| Year Ended December 31,
| 2021 |  | 2020 |  | 2019
Income tax computed at federal statutory rate | 21.0 | % |  | 21.0 | % |  | 21.0 | %
State taxes, net of federal tax benefit | 7.7 | % |  | 7.4 | % |  | 2.7 | %
General business credit—federal | 5.3 | % |  | 5.3 | % |  | 295.9 | %
Stock-based compensation | (0.7) | % |  | (1.0) | % |  | (50.0) | %
Other permanent differences | (0.1) | % |  | (0.1) | % |  | (2.4) | %
Change in valuation allowance | (33.2) | % |  | (32.6) | % |  | (267.7) | %
Effective income tax rate | 0.0 | % |  | — | % |  | (0.5) | %
Summary of Deferred Tax Assets and Liabilities | Net deferred tax assets and liabilities consisted of the following (in thousands):
| December 31,
| 2021 |  | 2020
Deferred tax assets: |  |  |
Net operating losses | $ | 51,554 |  |  | $ | 27,047 |
Research and development credits | 13,989 |  |  | 7,617 |
Accrued expenses | 292 |  |  | 291 |
Other | 775 |  |  | 474 |
Deferred rent | — |  |  | 266 |
Lease liability | 2,000 |  |  | — |
Stock based compensation | 1,816 |  |  | 428 |
Total deferred tax assets | 70,426 |  |  | 36,123 |
Deferred tax liabilities: |  |  |
Fixed asset basis | $ | (61) |  |  | $ | (124) |
Prepaid expenses | (921) |  |  | (558) |
Right of use asset | (1,760) |  |  | — |
Total deferred tax liabilities | (2,742) |  |  | (682) |
Valuation allowance | 67,684 |  |  | 35,441 |
Net deferred taxes | $ | — |  |  | $ | — |
Summary of Net Operating Losses and Tax Credit Carryforwards | Net operating losses and tax credit carryforwards were as follows (in thousands):
| December 31, 2021 |  | Expiration Year
Net operating losses, federal (starting from January 1, 2018) | $ | 155,231 |  |  | Does not expire
Net operating losses, federal (before January 1, 2018) | $ | 29,486 |  |  | 2035-2037
Net operating losses, state | $ | 182,964 |  |  | 2035-2041
Tax credits, federal | $ | 14,094 |  |  | 2036-2041
Tax credits, state | $ | 4,069 |  |  | Does not expire
Summary of Changes in Valuation Allowance for Deferred Tax Assets | Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2021 and 2020 related primarily to the increases in net operating loss carryforwards and research and development tax credit carryforwards and were as follows (in thousands):
| Year Ended December 31,
| 2021 |  | 2020
Valuation allowance at the beginning of the year | $ | 35,441 |  |  | $ | 21,929 |
Increases recorded to income tax provision | 32,243 |  |  | 13,512 |
Valuation allowance at the end of the year | $ | 67,684 |  |  | $ | 35,441 |
Summary of Reconciliation of Unrecognized Tax Benefits | A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):
| Year Ended December 31,
| 2021 |  | 2020 |  | 2019
January 1 | $ | 2,007 |  |  | $ | 1,355 |  |  | $ | 855 |
Additions based on tax positions related to current year | 1,081 |  |  | 513 |  |  | 570 |
Additions (reductions) for tax positions of prior year | 417 |  |  | 139 |  |  | (70) |
December 31 | $ | 3,505 |  |  | $ | 2,007 |  |  | $ | 1,355 |

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