Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accrued Expenses
Payroll and related costs	$ 946	$ 1,323
Clinical trials and drug development	1,035	156
Professional fees	224	113
Other	61	25
Total accrued expenses	$ 2,266	$ 1,617