Stock-based compensation (Tables)

9 Months Ended

Sep. 30, 2024

Stock-based compensation

Compensation cost recognized for all stock-based compensation awards

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2024		2023		2024		2023
	(in thousands)
Research and development	$	1,590	$	919	$	4,495	$	2,472
General and administrative		1,844		1,959		6,553		5,636
Total stock-based compensation expense	$	3,434	$	2,878	$	11,048	$	8,108

Summary of stock-based compensation expense by type of award

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2024		2023		2024		2023
	(in thousands)
Stock options	$	2,373	$	2,021	$	7,357	$	5,587
Restricted stock awards and units		983		774		3,454		2,339
Employee stock purchase plan awards		78		83		237		182
Total stock-based compensation expense	$	3,434	$	2,878	$	11,048	$	8,108

Summary of status and changes in unvested restricted stock

		Weighted
		Average
		Grant Date
		Fair Value
	Units	Per Unit
Unvested restricted stock units as of December 31, 2023	1,370,897	$	6.65
Granted	867,558	$	8.15
Vested	(423,362)	$	6.23
Forfeited	(198,076)	$	6.68
Unvested restricted stock units as of September 30, 2024	1,617,017	$	7.56

Summary of stock option activity

		Weighted		Remaining	Aggregate
		Average		Contractual	Intrinsic
		Exercise		Life	Value
	Shares	Price		(in years)	(in thousands)
Outstanding at December 31, 2023	7,425,444	$	8.52
Granted	2,325,226	$	7.79
Exercised	(86,100)	$	4.11
Cancelled or forfeited	(793,242)	$	11.69
Outstanding at September 30, 2024	8,871,328	$	8.08	7.5		3,756
Exercisable at September 30, 2024	4,604,321	$	8.51	6.4		2,777