Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accrued Liabilities [Abstract]
Accrued external research, development and manufacturing costs	$ 72,064	$ 48,590
Accrued professional and consultant fees	2,326	2,155
Accrued employee compensation	1,817	4,945
Other	330	587
Accrued Expenses	$ 76,537	$ 56,277