Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accrued Expenses
Payroll and related costs	$ 1,349	$ 2,514
Clinical trials and drug development	5,047	1,849
Professional fees	574	396
Short-term lease liabilities	462	446
Other	47	63
Total accrued expenses	$ 7,479	$ 5,268