Stock based compensation - Stock-based compensation expense and by award type (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Stock based compensation
Total stock-based compensation	$ 3,797	$ 2,380
Stock options
Stock based compensation
Total stock-based compensation	3,546	2,108
Restricted stock units
Stock based compensation
Total stock-based compensation	97
Restricted stock awards
Stock based compensation
Total stock-based compensation	93	272
Employee stock purchase plan
Stock based compensation
Total stock-based compensation	61
Research and development expenses
Stock based compensation
Total stock-based compensation	2,112	1,309
General and administrative expense
Stock based compensation
Total stock-based compensation	$ 1,685	$ 1,071