Stock-based compensation - Activity Under Stock Option Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Number of Shares
Outstanding at beginning of period (in shares)	10,902,845
Granted (in shares)	2,697,112
Exercised (in shares)	(14,223)
Cancelled/forfeited (in shares)	(1,366,486)
Outstanding at end of period (in shares)	12,219,248	10,902,845
Exercisable, at end of period (in shares)	7,919,813
Weighted- Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 7.42
Granted (in dollars per share)	2.90
Exercised (in dollars per share)	3.25
Cancelled/forfeited (in dollars per share)	8.06
Outstanding at end of period (in dollars per share)	6.35	$ 7.42
Exercisable, at end of period (in dollars per share)	$ 7.67
Additional Disclosures
Weighted average remaining contractual term, options outstanding	6 years 6 months	6 years 9 months 18 days
Weighted average remaining contractual term, options exercisable	5 years 4 months 24 days
Aggregate intrinsic value, options outstanding	$ 130	$ 1,786
Aggregate intrinsic value, options exercisable	$ 45