Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accrued Expenses
Payroll and related costs	$ 1,260	$ 2,179
Clinical and nonclinical trial expenses	5,247	4,199
Professional and consulting fees	701	859
Restructuring expenses	64	113
Other	113	111
Total accrued expenses	$ 7,385	$ 7,461