Technology license agreement - Additional Information (Details) - BWH License - USD ($) $ in Thousands			6 Months Ended
	Sep. 15, 2020	Jan. 20, 2018	Jun. 30, 2022	Jun. 30, 2021
Technology License Agreement [Line Items]
Committed amount to remitting in support of clinical trial		$ 750
Committed period to remitting in support of clinical trial		3 years
Non-refundable fee		$ 40
Expense for startup and patient fees for clinical trials			$ 0	$ 28
Payment for license fee	$ 100
Payment at the time of entering into license	141
Payment for annual license fee	50
Maximum amount upon achievement of various clinical, commercial and sales milestones	$ 39,000