Summary of Stock-Based Compensation Recognized (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation		$ 515	$ 1,026
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation		128	369
General and Administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	[1]	$ 387	$ 657

[1] Included in general and administrative stock-based compensation for the three months ended March 31, 2022 is stock-based compensation expense related to 32,684 shares of common stock issued to certain board members in lieu of their cash compensation.