Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accrued Expenses
Payroll and related costs	$ 1,234	$ 1,323
Clinical trials and drug development	2,224	156
Professional fees	200	113
Other	302	25
Total accrued expenses	$ 3,960	$ 1,617