Accrued Expense (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accrued Expense
Accrued expense	$ 582	$ 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
Other accrued expenses	$ 100	$ 100