Commitments and contingencies (Details)	1 Months Ended	12 Months Ended
	May 31, 2017 ft² item	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Aug. 31, 2020 USD ($)
Future minimum lease payments
Rent expenses		$ 400,000	$ 300,000
Capital leases
Interest expense		18,000	60,000
Defined contribution		74,000	61,000
Office and laboratory space
Operating leases
Lease term	62 months
Space of leased area | ft²	11,000
Number of additional extension of lease terms | item	2
Additional lease term	5 years
Deferred rent		16,000	18,000
Future minimum lease payments
2021		349,000
2022		153,000
Total		502,000
Lab equipment
Operating leases
Lease term				1 year
Fixed monthly payments				$ 18,000
Capital leases
Interest expense		$ 7,000	$ 60,000