Income Taxes (Tables)

12 Months Ended

Dec. 31, 2022

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of the Company's Effective Tax Rate to the Statutory Federal Income Tax Rate

A reconciliation of the Company’s effective tax rate to the statutory federal income tax rate is as follows:

	Years Ended December 31,
	2022			2021
Federal income tax at statutory federal rate		21.0	%		21.0	%
State taxes		6.1			4.9
Permanent differences		—			0.3
Stock-based compensation		(2.8	)		0.1
Tax credits		(6.5	)		0.1
Recapture of tax credits		0.0			0.0
Other		(0.1	)		1.3
Change in valuation allowance		(17.9	)		(27.8	)
Total		(0.2	)%		(0.1	)%

Schedule of Temporary Differences That Give Rise to Significant Net Deferred Tax Assets

Temporary differences that give rise to significant net deferred tax assets as of December 31, 2022 and 2021 are as follows:

	December 31,
(in thousands)	2022			2021
Deferred tax assets:
Net operating losses	$	64,135		$	62,619
Capitalized research and development expenses		141			282
Credit carryforwards		167,397			167,498
Deferred compensation		1,181			1,993
Election out of installment method		820			956
Accrued expenses		44			44
Other temporary differences		621			672
Installment sale tax basis		15,869			15,869
Total gross deferred tax assets		250,208			249,933
Valuation allowance		(250,208	)		(249,933	)
Net deferred tax assets	$	—		$	—

Schedule of Changes in the Valuation Allowance

The change in the valuation allowance against the deferred tax assets in the years ended December 31, 2022 and 2021 was as follows:

(in thousands)	Balance at Beginning of Period		Additions		Deductions		Balance at End of Period
December 31, 2021	$	249,252	$	681	$	—	$	249,933
December 31, 2022		249,933		275		—		250,208