Income Taxes - Significant Component of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Net operating loss carryforwards	$ 164,486	$ 147,004
Deferred tax assets:
Start-up and organizational costs	21,705	25,909
Research and development credit carryforwards	39,817	37,183
Stock compensation	706	1,478
Capitalized acquisition costs	2,946	3,691
Lease liability	1,278	1,225
Depreciation	102	71
Other	156	135
Deferred Tax Assets Gross	231,196	216,696
Less valuation allowance	(230,119)	(215,513)
Total deferred tax assets	1,077	1,183
Deferred tax liabilities:
Right of use asset	(1,077)	(1,183)
Total deferred tax liabilities	(1,077)	(1,183)
Net deferred taxes	$ 0	$ 0