Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued research and development expenses	$ 6,406	$ 3,409
Accrued payroll and related expenses	963	1,350
Accrued professional fees	446	924
Accrued other	151	160
Total accrued expenses	$ 7,966	$ 5,843