Stock-based compensation

9 Months Ended

Sep. 30, 2024

Stock-based compensation

Stock-based compensation

9. Stock-based compensation

Stock-Based Compensation Expense

Total compensation cost recognized for all stock-based compensation awards in the condensed consolidated statements of operations and comprehensive (loss) income was as follows:

	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

Stock-based compensation expense by type of award included within the condensed consolidated statements of operations and comprehensive (loss) income was as follows:

	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

Restricted Stock Units

A summary of the status of and changes in unvested restricted stock unit activity under the Company’s equity award plans for the nine months ended September 30, 2024 was as follows:

		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

Stock-based compensation of restricted stock units is based on the fair value of the Company’s common stock on the date of grant and is recognized over the vesting period. All of the restricted stock units granted in the nine months ended September 30, 2024 vest in equal amounts, annually over three years. The stock-based compensation expense related to restricted stock units was $1.0 million and $3.5 million for the three and nine months ended September 30, 2024, respectively. The stock-based compensation expense related to restricted stock units was $0.8 million and $2.3 million for the three and nine months ended September 30, 2023, respectively.

As of September 30, 2024, the Company had unrecognized stock-based compensation expense related to its unvested restricted stock units of $9.1 million, which is expected to be recognized over the remaining average vesting period of 2.1 years.

Stock Options

The following is a summary of stock option activity for the nine months ended September 30, 2024:

		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

As of September 30, 2024, the Company had unrecognized stock-based compensation expense related to its unvested stock options of $20.1 million which is expected to be recognized over the remaining weighted-average vesting period of 2.7 years.