Income Taxes (Tables)
 12 Months Ended
Dec. 31, 2022
Income Tax Disclosure [Abstract]  
Schedule of reconciliation of the U.S. federal statutory income tax rate to the Company's effective income tax
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,
20222021
Federal statutory income tax rate(21.0)%(21.0)%
State taxes, net of federal benefit(6.0)(6.2)
Federal and state research and development tax credits(5.3)(6.4)
Stock‑based compensation expense0.5 (1.6)
Section 162(m) compensation deduction limitation0.1 1.6 
Other0.1 (0.4)
Increase in deferred tax asset valuation allowance31.6 34.0 
Effective income tax rate— %— %
Net deferred tax assets
Net deferred tax assets consisted of the following (in thousands):

December 31,
20222021
Deferred tax assets:
Net operating loss carryforwards$159,691 $145,990 
Research and development tax credit carryforwards45,478 36,161 
Accrued expenses105 2,137 
Capitalized intellectual property costs2,051 1,746 
Capitalized research and development expense32,007 86 
Operating lease liabilities301 10,194 
Stock‑based compensation expense24,454 21,483 
Depreciation74 — 
Total deferred tax assets264,161 217,797 
Deferred tax liabilities:
Operating lease assets(732)(9,590)
Depreciation and other— (1,500)
Total deferred tax liabilities(732)(11,090)
Valuation allowance263,429 206,707 
Net deferred tax assets$— $— 
Summary of changes in the valuation allowance for deferred tax assets
Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2022, 2021 and 2020 related primarily to the increase in net operating loss carryforwards and research and development tax credit carryforwards and were as follows (in thousands):
Year ended December 31,
202220212020
Valuation allowance as of beginning of year$206,707$139,877$85,884
Decreases recorded as benefit to income tax provision———
Increases recorded to income tax provision56,72266,83053,993
Valuation allowance as of end of year$263,429$206,707$139,877