Property and equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 37,005	$ 25,643
Less: accumulated depreciation	(11,570)	(7,657)
Property and equipment, net	25,435	17,986
Depreciation expense	3,817	2,765	$ 2,117
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	18,093	13,748
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	15,469	7,129
Furniture and office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,410	1,888
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	866	2,188
Other
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 167	$ 690