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Stock-Based Compensation - Summary of Share-based Compensation Expense (Detail) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]        
Total stock-based compensation expense $ 4,730 $ 128 $ 9,015 $ 175
Research and development expense [Member]        
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]        
Total stock-based compensation expense 2,079 73 4,004 104
General and administrative expense [Member]        
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]        
Total stock-based compensation expense $ 2,651 $ 55 $ 5,011 $ 71