Balance Sheet Details - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Prepaid Expense And Other Assets [Abstract]
Refundable withholding tax	$ 3,375
Prepaid clinical costs	188	$ 820
Prepaid manufacturing costs	76	930
Prepaid insurance	28	505
Other prepaid expenses and current assets	596	1,133
Total prepaid expenses and other current assets	$ 4,263	$ 3,388