Note Payable and Accrued Expenses - Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Note Payable and Accrued Expenses
Payroll and related costs	$ 2,498	$ 2,325
Clinical and nonclinical trial expenses	3,577	1,339
Cost of regaining rights to cancer program	840	425
Professional and consulting fees	368
Other	111	185
Total accrued expenses	$ 7,394	$ 4,274