Stock-based compensation (Tables)

6 Months Ended

Jun. 30, 2022

Stock-based compensation

Compensation cost recognized for all stock-based compensation awards

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

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2022		2021		2022		2021
	(in thousands)
Research and development	$	781	$	1,336	$	1,582	$	2,706
General and administrative		1,709		2,655		3,227		4,886
Total stock-based compensation expense	$	2,490	$	3,991	$	4,809	$	7,592

Summary of stock-based compensation expense by type of award

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2022		2021		2022		2021
	(in thousands)
Stock options	$	1,618	$	2,480	$	3,095	$	5,002
Restricted stock awards and units		842		1,392		1,634		2,366
Employee stock purchase plan awards		30		120		81		223
Total stock-based compensation expense	$	2,490	$	3,991		4,809		7,592

Summary of status and changes in unvested restricted stock

A summary of the status of and changes in unvested restricted stock unit activity under the Company’s equity award plans for the six months ended June 30, 2022 was as follows:

		Weighted
		Average
		Grant Date
		Fair Value
	Units	Per Unit
Unvested restricted stock units as of December 31, 2021	806,379	$	7.26
Granted	739,080	$	3.79
Vested	(344,255)		7.45
Forfeited	(169,839)	$	5.06
Unvested restricted stock units as of June 30, 2022	1,031,365	$	5.08

Summary of stock option activity

The following is a summary of stock option activity for the six months ended June 30, 2022:

		Weighted		Remaining	Aggregate
		Average		Contractual	Intrinsic
		Exercise		Life	Value
	Shares	Price		(in years)	(in thousands)
Outstanding at December 31, 2021	5,013,193	$	12.69	5.6	$	1,165
Granted	2,965,075	$	4.95
Exercised	(74,496)	$	7.90
Cancelled or forfeited	(1,274,172)	$	12.42
Outstanding at June 30, 2022	6,629,600	$	9.33	7.2	$	5,914
Exercisable at June 30, 2022	3,378,945	$	12.29	5.3	$	1,575