Stock-Based Compensation

6 Months Ended

Jun. 30, 2023

Stock-Based Compensation

Stock-Based Compensation

(8)  Stock-Based Compensation

A summary of stock option activity for the six months ended June 30, 2023 is as follows:

		Weighted		Weighted
		Average		Average
		Exercise		Remaining
		Price		Contractual
	Shares	Per Share		Term (In Years)
Options outstanding at December 31, 2022	5,085,662	$	29.26	7.9
Granted	1,534,575	$	36.92
Exercised	(46,624)	$	15.63
Canceled	(127,852)	$	31.62
Options outstanding at June 30, 2023	6,445,761	$	31.13	8.0
Options vested and expected to vest at June 30, 2023	6,284,352	$	31.16	7.9
Options exercisable at June 30, 2023	2,896,986	$	33.88	6.7
Shares available for grant under the 2021 Plan	1,031,245

The weighted average grant-date fair value of stock options granted during the three and six months ended June 30, 2023 was $28.32 and $28.41, respectively.

The aggregate intrinsic value of stock options vested and expected to vest at June 30, 2023 was $68.6 million. The aggregate intrinsic value of stock options exercisable at June 30, 2023 was $46.6 million. As of June 30, 2023, total compensation cost related to non-vested employee, consultant and non-employee director stock options not yet recognized was approximately $73.8 million, net of estimated forfeitures, which is expected to be recognized as expense over a weighted average period of 2.9 years.

Stock-based compensation expense for the three and six months ended June 30, 2023 and 2022 was recorded as follows:

	Three months ended June 30,				Six months ended June 30,
	2023		2022		2023		2022
	(In thousands)				(In thousands)
Research and development	$	2,489	$	1,798	$	4,650	$	3,412
General and administrative		2,728		1,656		4,907		3,195
Total stock-based compensation expense	$	5,217	$	3,454	$	9,557	$	6,607

The fair values of employee, consultant and non-employee director stock options granted during the three and six months ended June 30, 2023 and 2022 were valued using the Black-Scholes option pricing model with the following assumptions:

	Three months ended June 30,		Six months ended June 30,
	2023	2022	2023	2022
Expected stock price volatility	92%	90 - 91%	92%	90 – 97%
Expected option term	6.0 Years	6.0 Years	6.0 Years	6.0 Years
Risk-free interest rate	3.5 – 3.9%	2.7 - 3.6%	3.5 – 4.0%	1.7 – 3.6%
Expected dividend yield	None	None	None	None