Summary of Stock-Based Compensation Recognized (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation		$ 3,405	$ 3,627
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation		1,202	1,487
General and Administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	[1]	$ 2,203	$ 2,140

[1] Included in general and administrative stock-based compensation for the years ended December 31, 2021 and 2020 is $0.3 million and $0.3 million in expense related to 56,912 shares and 51,056 shares of common stock, respectively, issued to certain board members in lieu of their cash compensation.