Stock-based compensation - Summary of stock option activity (Details) - 2020 Stock Option and Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Number of Options
Options outstanding, beginning balance (in shares)	6,993,052
Options granted (in shares)	4,180,270
Options exercised (in shares)	(13,096)
Options forfeited/expired (in shares)	(1,685,217)
Options outstanding, ending balance (in shares)	9,475,009	6,993,052
Options exercisable (in shares)	3,838,707
Options vested and expected to vest (in shares)	9,475,009
Weighted-Average Exercise Price
Options outstanding, beginning balance (in dollars per share)	$ 21.57
Options granted (in dollars per share)	3.87
Options exercised (in dollars per share)	4.46
Options forfeited/expired (in dollars per share)	18.48
Options outstanding, ending balance (in dollars per share)	14.34	$ 21.57
Options exercisable (in dollars per share)	20.54
Options vested and expected to vest (in dollars per share)	$ 14.34
Options, Additional Disclosures
Weighted average remaining contractual term, outstanding	7 years 7 months 9 days	7 years 9 months 10 days
Weighted average remaining contractual term, exercisable	6 years 8 months 4 days
Weighted average remaining contractual term, vested and expected to vest	7 years 7 months 9 days
Aggregate intrinsic value, outstanding	$ 8,261	$ 1,031
Aggregate intrinsic value, exercisable	482
Aggregate intrinsic value, vested and expected to vest	$ 8,261