Income Taxes - Significant Component of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Net operating loss carryforwards	$ 171,070	$ 164,486
Deferred tax assets:
Start-up and pre-clinical studies	17,204	21,705
Research and development credit carryforwards	40,116	39,817
Stock-based compensation	698	706
Capitalized acquisition costs	2,180	2,946
Lease liability	618	1,278
Depreciation	239	102
Capitalized research expenses	5,156	0
Other	27	156
Deferred Tax Assets Gross	237,308	231,196
Less valuation allowance	(236,827)	(230,119)
Total deferred tax assets	481	1,077
Deferred tax liabilities:
Right of use asset	(481)	(1,077)
Total deferred tax liabilities	(481)	(1,077)
Net deferred taxes	$ 0	$ 0