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Summary of Stock-Based Compensation Recognized (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Total stock-based compensation $ 1,026 $ 805
Research and development    
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Total stock-based compensation 369 344
General and Administrative    
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Total stock-based compensation [1] $ 657 $ 461
[1] Included in general and administrative stock-based compensation for the three months ended March 31, 2021 is expense related to 10,149 shares of common stock issued to certain board members in lieu of their cash compensation