Other Balance Sheet Accounts - Summary of Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Payables And Accruals [Abstract]
Employee compensation	$ 1,850	$ 2,471
Clinical trial accruals	206	1,686
Accounts payable	316	227
Deferred rent	480	432
Other accrued liabilities	512	385
Total accounts payable and accrued expenses	$ 3,364	$ 5,201