Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Accrued Expenses
Research and development expenses	$ 1,489	$ 123
Employee-related expenses	1,088
Licensing fees		250
Vixen contract payable.	100
Professional fees	37	283
Other	103	89
Total accrued expenses	$ 2,817	$ 745