Income taxes - Deferred taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Net operating loss carryforwards	$ 20,523	$ 19,925
Research and development intangibles	4,839
Research and development credits	2,878	2,157
Share-based compensation	2,016	886
Accrued bonus	383	331
Amortization	1	1
Gross deferred tax assets	30,640	23,300
Less: valuation allowance	(30,609)	(23,255)
Net deferred tax asset	31	45
Deferred tax liability
Depreciation	(31)	(45)
Total deferred tax liabilities