Stock-based compensation - Stock-based compensation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Stock-based compensation
Stock-based compensation expense	$ 1,040	$ 1,719	$ 4,042	$ 5,867
Research and development expenses
Stock-based compensation
Stock-based compensation expense	428	643	1,568	2,412
General and Administrative Expense
Stock-based compensation
Stock-based compensation expense	$ 612	$ 1,076	$ 2,474	$ 3,455