Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Taxes

Schedule of tax effects of temporary differences that give rise to significant portions of deferred tax assets

	December 31,
	2021		2020
Deferred tax assets:
Net operating loss carryforwards	$	81,102	$	66,907
Research credit carryforward		7,943		7,909
Stock options and other		2,114		1,962
Total gross deferred tax assets		91,159		76,778
Valuation allowance for deferred tax assets		(91,159)		(76,778)
Net deferred tax assets	$	—	$	—

Schedule of reconciliation of U.S. statutory income tax rate to effective tax rate

	December 31,
	2021		2020		2019
Federal income tax at statutory rate	21.0	%	21.0	%	21.0	%
State income tax benefit, net of federal benefit	0.3	%	1.0	%	7.0	%
Research and development tax credits	0.2	%	0.7	%	4.0	%
Other	(2.2)	%	(2.0)	%	(4.0)	%
Increase to valuation allowance	(19.3)	%	(20.7)	%	(28.0)	%
Effective income tax rate	0.0	%	0.0	%	0.0	%