Accrued Expenses and Other Current Liabilities - Schedule of Composition of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued clinical and related costs	$ 3,272	$ 2,753
Accrued compensation and related costs	1,841	2,260
Accrued interest	44	69
Current portion of operating lease liability	485	459
Accrued other	481	390
Accrued expenses and other current liabilities	$ 6,123	$ 5,931