Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense (Benefit)

The difference between the provision for income taxes and income taxes computed using the effective U.S. federal statutory rate is as follows (in thousands):

	December 31,
	2023			2022
Tax at statutory federal rate	$	(23,210	)	$	(38,225	)
State tax, net of federal benefit		(1,460	)		(13,898	)
Research and development credits		—			(3,531	)
Stock-based compensation expense		19,022			5,857
Non-deductible compensation		(4,682	)		2,104
Employee retention credit adjustment		—			(1,265	)
Change in valuation allowance		7,556			46,452
Provision to return adjustment		3,008			—
Other		(234	)		2,506
Provision for income taxes	$	—		$	—

Schedule of Deferred Tax Assets and Liabilities

Deferred income tax assets and liabilities arising from differences between accounting for financial statement purposes and tax purposes, less valuation allowance at year-end are as follows (in thousands):

	December 31,
	2023			2022
Deferred tax assets:
Net operating loss carryforward	$	320,998		$	313,834
Research and development credits		59,417			60,245
Section 174 capitalized research and development		28,822			20,903
Stock-based compensation		15,413			23,991
Lease liabilities		1,471			2,052
Other		5,005			3,693
Total gross deferred tax assets		431,126			424,718
Deferred tax liabilities:
Right-of-use lease assets		(1,362	)		(1,914	)
Total gross deferred tax liabilities		(1,362	)		(1,914	)
Valuation allowance		(429,764	)		(422,804	)
Net deferred tax assets	$	—		$	—

Summary of Unrecognized Tax Benefits

A reconciliation of our unrecognized tax benefits is as follows (in thousands):

	Year Ended December 31,
	2023			2022
Balance at beginning of year	$	11,235		$	9,631
Decrease for tax positions of prior years		(332	)		(200	)
Increase based on tax positions related to current year		—			1,804
Balance at end of year	$	10,903		$	11,235