Income Taxes - Significant Component of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Net operating loss carryforwards	$ 154,634	$ 148,009
Deferred tax assets:
Start-up and pre-clinical studies	11,011	13,754
Research and development credit carryforwards	40,486	39,838
Stock-based compensation	699	681
Capitalized acquisition costs	1,050	1,570
Lease liability	0	0
Depreciation	1	1
Capitalized research expenses	5,400	7,176
Other	0	2
Deferred Tax Assets Gross	213,281	211,031
Less valuation allowance	(213,281)	(211,031)
Total deferred tax assets	0	0
Deferred tax liabilities:
Right-of-use asset	0	0
Total deferred tax liabilities	0	0
Net deferred taxes	$ 0	$ 0