Accrued Expenses - Summary (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accrued expenses
Accrued accounts payable	$ 3,466	$ 1,220
Research and development fees	2,066	2,001
Compensation expense	1,479	2,759
Lease liabilities	987	1,030
Accrued license obligations	799	358
Audit and tax fees	429	128
Other current liabilities	336	235
Total	$ 9,562	$ 7,731