Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accounts Payable and Accrued Liabilities [Abstract]
External research and development expenses	$ 32,619	$ 31,259
Restructuring reserve	20,790	0
Payroll and related expenses	11,945	17,255
Revenue-related reserves	9,441	3,381
Professional fees	5,626	3,306
Other	1,071	389
Total accrued expenses and other current liabilities	$ 80,773	$ 55,227