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Stock-Based Compensation - Summary of Share-based Compensation Expense (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Total stock-based compensation expense $ 4,285 $ 47
Research and development expense [Member]    
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Total stock-based compensation expense 1,925 31
General and administrative expense [Member]    
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Total stock-based compensation expense $ 2,360 $ 16