Income Taxes (Tables)

12 Months Ended

Dec. 31, 2022

Income Tax Disclosure [Abstract]

United States and Foreign Components of Consolidated Loss Before Income Taxes

U.S and foreign components of consolidated loss before income taxes for the years ended December 31, 2022, 2021 and 2020, was as follows (in thousands):

	2022			2021			2020
Loss before income taxes:
U.S.	$	(43,096	)	$	(54,757	)	$	(61,246	)
Foreign		759			700			1,673
Loss before income taxes	$	(42,337	)	$	(54,057	)	$	(59,573	)

Provision Benefit for Income Taxes

The provision for income taxes for the years ended December 31, 2022, 2021 and 2020, was as follows (in thousands):

	2022			2021		2020
Provision for income taxes:
Current:
Foreign	$	520		$	274	$	274
Federal		—			—		—
State		5			—		—
Total current		525			274		274
Deferred:
Foreign					—		—
Federal		(18	)		23		6
State		(19	)		22		4
Total deferred		(37	)		45		10
Provision for income taxes	$	488		$	319	$	284

Difference Between Provision for Income Taxes and Amounts Computed by Applying Federal Statutory Income Tax Rate to Loss before Taxes

The difference between the provision for income taxes and the amount computed by applying the federal statutory income tax rate to loss before taxes for the years ended December 31, 2022, 2021 and 2020, was as follows (in thousands):

	2022			2021			2020
Federal statutory tax	$	(8,891	)	$	(11,352	)	$	(12,510	)
Federal research credits		(1,874	)		(2,159	)		(1,630	)
State research credits		(822	)		(767	)		(749	)
Expiration of federal carryovers		4,858			4,651			9,200
Change in valuation allowance		6,379			10,482			6,738
Compensation related items		1,794			460			978
State taxes		(1,127	)		(1,294	)		(1,921	)
Other		171			298			178
Provision for income taxes	$	488		$	319		$	284

Significant Components of Deferred Tax Assets and Liabilities

The significant components of the Company’s deferred tax assets and liabilities at December 31, 2022, 2021 and 2020, were as follows (in thousands):

	December 31,
	2022			2021
Deferred tax assets:
Net operating loss carryforwards	$	136,632		$	150,523
Research and development credit carryforwards		29,242			29,411
Capitalized research and development		27,916			8,406
Compensation related items		12,014			11,951
Operating leases		3,786			4,125
Other		9,056			8,218
Total deferred tax assets		218,646			212,634
Valuation allowance		(215,903	)		(209,524	)
Net deferred tax assets	$	2,743		$	3,110
Deferred tax liabilities:
Right-of-use assets	$	2,610		$	2,895
Other		194			313
Total deferred tax liabilities	$	2,804		$	3,208

Gross Amounts and Dates of Expiration of Tax Credits and Carryovers

The Company's tax losses and credits are subject to varying carryforward periods. The gross amounts and dates of expiration of the significant carryforwards are as follows:

			Expires		Expires		Expires		No
	Total		2023-2025		2026-2032		2033-2042		Expiration
Federal losses carryovers	$	616,922	$	69,647	$	186,833	$	169,673	$	190,769
California loss carryovers		75,192				46,641		28,551
Other state loss carryovers		37,687		601		364		36,722
Federal research credits		18,036		3,758		1,483		12,795
California research credits		14,186								14,186
Federal foreign tax credits		610				610

Reconciliation of Unrecognized Tax Benefits

The following is a tabular reconciliation of the total amounts of unrecognized tax benefits (in thousands):

	December 31,			December 31,
	2022			2021
Unrecognized tax benefits at beginning of period	$	9,366		$	10,110
Decreases related to expired carryforwards		(1,481	)		(1,296	)
Increases related to prior year tax positions		258			112
Increases related to current year tax positions		509			440
Unrecognized tax benefits at end of period	$	8,652		$	9,366