Stock-Based Compensation

3 Months Ended

Mar. 31, 2023

Stock-Based Compensation

Stock-Based Compensation

(8)  Stock-Based Compensation

A summary of stock option activity for the three months ended March 31, 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	26,900	$	43.17
Exercised	(37,492)	$	15.18
Canceled	(107,306)	$	20.95
Options outstanding at March 31, 2023	4,967,764	$	29.62	7.6
Options vested and expected to vest at March 31, 2023	4,884,568	$	29.72	7.6
Options exercisable at March 31, 2023	2,273,841	$	38.18	6.4
Shares available for grant under the 2021 Plan	1,918,374

The weighted average grant-date fair value of stock options granted during the three months ended March 31, 2023 was $33.25.

The aggregate intrinsic value of stock options vested and expected to vest at March 31, 2023 was $78.1 million. The aggregate intrinsic value of stock options exercisable at March 31, 2023 was $42.0 million. As of March 31, 2023, total compensation cost related to non-vested employee, consultant and non-employee director stock options not yet recognized was approximately $38.3 million, net of estimated forfeitures, which is expected to be recognized as expense over a weighted average period of 2.5 years.

Stock-based compensation expense for the three months ended March 31, 2023 and 2022 was recorded as follows:

	Three months ended March 31,
	2023		2022
	(In thousands)
Research and development	$	2,162	$	1,614
General and administrative		2,178		1,539
Total stock-based compensation expense	$	4,340	$	3,153

The fair values of employee, consultant and non-employee director stock options granted during the three months ended March 31, 2023 and 2022 were valued using the Black-Scholes option pricing model with the following assumptions:

	Three months ended March 31,
	2023	2022
Expected stock price volatility	92%	91 - 97%
Expected option term	6.0 Years	6.0 Years
Risk-free interest rate	3.7 - 4.0%	1.7 - 1.9%
Expected dividend yield	None	None