Balance Sheet Components - Summary of Accrued Expenses and Other Payables (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accrued clinical and research related expenses	$ 4,299	$ 3,617
Accrued employee related expenses	1,338	1,420
Accrued professional service fees	669	115
Accrued milestone payment to former collaboration partner	250	0
Other	171	120
Total accrued expenses and other payables	$ 6,727	$ 5,272