Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Expenses
Payroll and related costs	$ 2,514	$ 1,364
Clinical trials and drug development	1,849	2,781
Professional fees	396	204
Short-term lease liabilities	446
Other	63	88
Total accrued expenses	$ 5,268	$ 4,437