Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payroll and related costs	$ 3,108	$ 2,498
Clinical and nonclinical trial expenses	3,495	3,577
Cost of regaining rights to cancer program	1,317	840
Professional and consulting fees		368
Other	80	111
Total accrued expenses	8,000	$ 7,394
Former Executive
Payroll and related costs	600
Salary continuation severance benefits	900
Long-term portion of other liabilities	$ 300