Accounts Payable and Accrued Expenses - Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Payables And Accruals [Abstract]
Trade payables	$ 872	$ 553
Employee compensation, benefits, and related accruals	731	1,077
Consulting and contracted research	432	774
Professional fees	216	180
Other	27	80
Total	$ 2,278	$ 2,664