Stock-based compensation (Tables)

6 Months Ended

Jun. 30, 2024

Stock-based compensation

Compensation cost recognized for all stock-based compensation awards

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2024		2023		2024		2023
	(in thousands)
Research and development	$	1,626	$	690	$	2,906	$	1,553
General and administrative		2,416		1,982		4,709		3,677
Total stock-based compensation expense	$	4,042	$	2,672	$	7,615	$	5,230

Summary of stock-based compensation expense by type of award

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2024		2023		2024		2023
	(in thousands)
Stock options	$	2,577	$	1,903	$	4,985	$	3,566
Restricted stock awards and units		1,382		724		2,471		1,565
Employee stock purchase plan awards		83		45		159		99
Total stock-based compensation expense	$	4,042	$	2,672	$	7,615	$	5,230

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	851,908	$	8.16
Vested	(381,069)	$	6.06
Forfeited	(38,196)	$	6.51
Unvested restricted stock units as of June 30, 2024	1,803,540	$	7.49

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	1,999,926	$	7.81
Exercised	(58,458)	$	4.47
Cancelled or forfeited	(500,794)	$	14.40
Outstanding at June 30, 2024	8,866,118	$	8.05	7.4		9,481
Exercisable at June 30, 2024	4,212,635	$	8.57	6.4	$	5,862