Accrued Expense (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accrued Expense
Accrued expense	$ 657	$ 975
Accrued clinical trial expenses		400
Accrued vacation and bonus expenses	300	400
Manufacturing and testing services	100
Manufacturing expenses		100
Professional and consulting fees	100
Accrued clinical and preclinical expenses	100
Other accrued expenses	$ 100	$ 100