Income Taxes - Components of Company's Deferred Tax Asset (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred Tax Assets, Net of Valuation Allowance [Abstract]
Accrued bonuses	$ 63	$ 53
Accrued vacation	26	24
Net operating loss (NOL) carryover	14,975	12,876
Research & development tax credits	3,353	2,902
Share based expense	572	472
Other	4	4
Right of use lease liability	49	69
Fixed asset depreciation	43	55
Total deferred tax asset	19,085	16,455
Less: valuation allowance	(19,042)	(16,395)
Net deferred tax asset	43	60
Right of use asset	(43)	(60)
Net deferred tax asset	$ 0	$ 0