Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued external research and development expenses	$ 9,794	$ 7,035
Accrued payroll and related expenses	1,313	3,918
Accrued professional fees	1,553	1,066
Accrued other	298	222
Total Accrued expenses and other current liabilities	$ 12,958	$ 12,241