Income taxes - Components of Deferred Income Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
U.S. net operating losses	$ 22,863	$ 12,328
Research and development deductions and credits	2,414	1,040
Intangibles	457	422
Lease liability	2,701	2,513
Stock-based compensation	1,695	717
Other	186	162
Total deferred tax assets:	30,316	17,182
Deferred income tax liabilities
Right-of-use assets	2,261	2,132
Other	287	157
Total deferred tax liabilities	2,548	2,289
Net deferred income tax assets	27,768	14,893
Less: valuation allowance	(27,768)	(14,893)
Deferred tax assets, net of valuation allowance	$ 0	$ 0