Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accrued Expenses
Payroll and related costs	$ 1,796	$ 2,179
Clinical and nonclinical trial expenses	4,405	4,199
Professional and consulting fees	692	859
Restructuring expenses	16	113
Other	114	111
Total accrued expenses	$ 7,023	$ 7,461