Stock-based compensation - Compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 2,558	$ 2,319
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	1,663	1,477
Restricted stock awards and units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	841	792
Employee stock purchase plan awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	54	51
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	863	801
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 1,695	$ 1,518