Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

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, 2021, 2020 and 2019, was as follows (in thousands):

	2021			2020			2019
Loss before income taxes:
U.S.	$	(54,757	)	$	(61,246	)	$	(71,946	)
Foreign		700			1,673			965
Loss before income taxes	$	(54,057	)	$	(59,573	)	$	(70,981	)

Provision Benefit for Income Taxes

The provision for income taxes for the years ended December 31, 2021, 2020 and 2019, was as follows (in thousands):

	2021		2020		2019
Provision for income taxes:
Current:
Foreign	$	274	$	274	$	255
Federal		—		—		—
State		—		—		2
Total current		274		274		257
Deferred:
Foreign		—		—		—
Federal		23		6		4
State		22		4		2
Total deferred		45		10		6
Provision for income taxes	$	319	$	284	$	263

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, 2021, 2020 and 2019, was as follows (in thousands):

	2021			2020			2019
Federal statutory tax	$	(11,352	)	$	(12,510	)	$	(14,906	)
Federal research credits		(2,159	)		(1,630	)		(1,857	)
State research credits		(767	)		(749	)		(821	)
Expiration of federal carryovers		4,651			9,200			5,472
Change in valuation allowance		10,482			6,738			13,059
Compensation related items		460			978			158
State taxes		(1,294	)		(1,921	)		(1,111	)
Other		298			178			269
Provision for income taxes	$	319		$	284		$	263

Significant Components of Deferred Tax Assets and Liabilities

The significant components of the Company’s deferred tax assets and liabilities at December 31, 2021, 2020 and 2019, were as follows (in thousands):

	December 31,
	2021			2020
Deferred tax assets:
Net operating loss carryforwards	$	150,523		$	141,176
Research and development credit carryforwards		29,411			28,892
Capitalized research and development		8,406			10,756
Compensation related items		11,951			10,957
Operating leases		4,125			4,214
Other		8,218			6,051
Total deferred tax assets		212,634			202,046
Valuation allowance		(209,524	)		(199,042	)
Net deferred tax assets	$	3,110		$	3,004
Deferred tax liabilities:
Right-of-use assets	$	2,895		$	2,892
Other		313			163
Total deferred tax liabilities	$	3,208		$	3,055

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		2022-2024		2025-2031		2032-2041		Expiration
Federal losses carryovers	$	676,762	$	76,223	$	183,062	$	185,571	$	231,906
California loss carryovers		80,227		—		41,407		38,820		—
Other state loss carryovers		53,967		620		870		52,477
Federal research credits		19,001		6,180		1,539		11,282		—
California research credits		13,178		—		—		—		13,178
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,
	2021			2020
Unrecognized tax benefits at beginning of period	$	10,110		$	10,842
Decreases related to expired carryforwards		(1,296	)		(1,171	)
Increases related to prior year tax positions		112
Increases related to current year tax positions		440			439
Unrecognized tax benefits at end of period	$	9,366		$	10,110