Property and equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 4,018	$ 2,988
Less: accumulated depreciation	(784)	(184)
Property and equipment, net	3,234	2,804
Depreciation expense	600	184
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	2,183	1,223
Furniture and office equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	499	441
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 1,336	$ 1,324