Accrued Expenses
 12 Months Ended
Dec. 31, 2021
Payables and Accruals [Abstract]  
Accrued Expenses Accrued Expenses
Accrued expenses consisted of the following (in thousands):
December 31,
20212020
Accrued employee compensation and benefits$5,596 $3,513 
Accrued tenant improvements13 2,385 
Accrued external research and development expenses3,079 2,146 
Accrued professional fees495 979 
Other379 138 
$9,562 $9,161