Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Accrued Expenses
Research and development expenses	$ 178	$ 123
Employee-related expenses	310
Licensing fees		250
Vixen contract payable.	100
Professional fees	281	283
Other	52	89
Accrued expenses, total	$ 921	$ 745