Property and equipment, net - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, cost	$ 2,748	$ 843
Property and equipment, accumulated amortization	688	443
Property and equipment, net book Value	2,060	400
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, cost	490	490
Property and equipment, accumulated amortization	333	248
Property and equipment, net book Value	157	242
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, cost	1,515
Property and equipment, accumulated amortization	62
Property and equipment, net book Value	1,453
Office Furniture, Equipment and Systems [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, cost	743	353
Property and equipment, accumulated amortization	293	195
Property and equipment, net book Value	$ 450	$ 158