Accounts Payable and Accrued Expenses - Schedule of Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Accounts payable	$ 711	$ 515
Accrued research projects	1,552	549
Accrued professional fees	303	266
Accrued compensation and benefits	543	504
Accrued other	41	112
Total	$ 3,150	$ 1,946