Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accrued Expenses
Payroll and related costs	$ 477	$ 2,133
Clinical and nonclinical trial expenses	2,909	3,229
Professional and consulting fees	591	584
Other	111	126
Total accrued expenses	$ 4,088	$ 6,072