Income Taxes - Significant Component of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Net operating loss carryforwards	$ 148,009	$ 171,070
Deferred tax assets:
Start-up and pre-clinical studies	13,754	17,204
Research and development credit carryforwards	39,838	40,116
Stock-based compensation	681	698
Capitalized acquisition costs	1,570	2,180
Lease liability	0	618
Depreciation	1	239
Capitalized research expenses	7,176	5,156
Other	2	27
Deferred Tax Assets Gross	211,031	237,308
Less valuation allowance	(211,031)	(236,827)
Total deferred tax assets	0	481
Deferred tax liabilities:
Right of use asset	0	(481)
Total deferred tax liabilities	0	(481)
Net deferred taxes	$ 0	$ 0