Accrued Expenses And Current Portion Of Other Liabilities - Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued compensation	$ 2,767	$ 2,274
Accrued taxes	29	558
External research and development	3,557	1,017
Accrued outside services	927	0
Accrued leasehold improvements	0	927
Other accrued expenses	70	198
Total accrued expenses	$ 7,350	$ 4,974	[1]

[1] The balance sheet as of December 31, 2020 is derived from the audited financial statements as of that date.