Property and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 1,561	$ 1,074
Less: accumulated depreciation	(431)	(262)
Property and equipment, net	1,130	812
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	407	334
Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	263	252
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	446	43
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 445	$ 445