Income Tax (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Schedule of Pretax Losses for Domestic and Foreign Operations

Pretax losses were generated by both domestic and foreign operations as follows (in thousands):

	Years Ended December 31,
	2021			2020			2019
United States	$	(33,316	)	$	(15,950	)	$	(23,315	)
Foreign		(458	)		(280	)		(448	)
Worldwide pre-tax loss	$	(33,774	)	$	(16,230	)	$	(23,763	)

Schedule of Reconciliations of the Expected Statutory Federal Income Tax

A reconciliation of the expected statutory federal income tax provision to the actual income tax provision is summarized as follows (in thousands):

	Years Ended December 31,
	2021			2020			2019
Expected income taxes benefit at federal statutory rate	$	(7,093	)	$	(3,408	)	$	(4,990	)
State income taxes, net of federal benefit		(2,313	)		(12	)		(19	)
Permanent items and other		592			169			49
Stock compensation		90			804			701
Research credits		(1,253	)		(835	)		(817	)
Unrecognized tax benefits		500			334			327
Foreign rate differential		21			13			20
Change in tax rate		52			(7	)		(49	)
Change in valuation allowance		9,404			2,942			4,778
Income tax (benefit) expense	$	—		$	—		$	—

Schedule of Significant Components of Deferred Tax Assets

Significant components of our deferred tax assets are summarized as follows (in thousands):

	December 31,
	2021			2020
Deferred tax assets:
Net operating loss carryforwards	$	48,833		$	41,203
Capitalized research and development expenses		18,086			17,007
Research credits and other state credits		13,695			12,954
Intangible assets		1,465			1,655
Reserve and accruals		641			544
Share-based compensation expense		1,369			1,253
Lease liability		290			472
Valuation allowance		(84,112	)		(74,646	)
Total deferred tax assets	$	267		$	442
Deferred tax liabilities:
Right of use lease assets		(267	)		(442	)
Total deferred tax liabilities		(267	)		(442	)
Net deferred tax assets	$	—		$	—

Schedule of Activity Related to Unrecognized Tax Benefits

The activity related to our unrecognized tax benefits is summarized as follows (in thousands):

	December 31,
	2021			2020		2019
Balance as of beginning of year	$	21,707		$	21,302	$	19,643
Increase (decrease) related to prior year tax positions		(9	)		3		—
Increase related to current year tax positions		534			402		1,659
Balance as of end of year	$	22,232		$	21,707	$	21,302