Stock-Based Compensation

9 Months Ended

Sep. 30, 2023

Stock-Based Compensation

Stock-Based Compensation

(8)  Stock-Based Compensation

A summary of stock option activity for the nine months ended September 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	1,553,275	$	36.88
Exercised	(50,773)	$	15.89
Canceled	(180,580)	$	87.57
Options outstanding at September 30, 2023	6,407,584	$	29.57	7.8
Options vested and expected to vest at September 30, 2023	6,271,198	$	29.54	7.7
Options exercisable at September 30, 2023	3,088,826	$	29.58	6.6
Shares available for grant under the 2021 Plan	1,065,273

The weighted average grant-date fair value of stock options granted during the three and nine months ended September 30, 2023 was $25.80 and $28.38, respectively.

The aggregate intrinsic value of stock options vested and expected to vest at September 30, 2023 was $41.2 million. The aggregate intrinsic value of stock options exercisable at September 30, 2023 was $32.6 million. As of September 30, 2023, total compensation cost related to non-vested employee, consultant and non-employee director stock options not yet recognized was approximately $67.6 million, net of estimated forfeitures, which is expected to be recognized as expense over a weighted average period of 2.7 years.

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
	(In thousands)				(In thousands)
Research and development	$	3,618	$	2,342	$	8,269	$	5,754
General and administrative		3,503		2,154		8,409		5,349
Total stock-based compensation expense	$	7,121	$	4,496	$	16,678	$	11,103

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

	Three Months Ended September 30,		Nine Months Ended September 30,
	2023	2022	2023	2022
Expected stock price volatility	92%	91%	92%	90 – 97%
Expected option term	6.0 Years	6.0 Years	6.0 Years	6.0 Years
Risk-free interest rate	4.1%	2.9 – 3.5%	3.5 – 4.1%	1.7 – 3.6%
Expected dividend yield	None	None	None	None