Accrued Expenses and Other Current Liabilities - Schedule of Accrued Liabilities and Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Expenses and Other Current Liabilities
Accrued clinical and non-clinical expenses	$ 3,451	$ 9,790
Accrued contract manufacturing expenses	1,414	1,971
Derivative liability for exit fee	969	533
Accrued regulatory expenses	342	21
Accrued professional and consulting services	323	112
Foreign currency derivative contract		52
Other	749	378
Accrued liabilities and other liabilities	$ 7,248	$ 12,857