Stock-Based Compensation

9 Months Ended

Sep. 30, 2021

Stock-Based Compensation

Stock-Based Compensation

(8)  Stock-Based Compensation

A summary of stock option activity for the nine months ended September 30, 2021 is as follows:

		Weighted		Weighted
		Average		Average
		Exercise		Remaining
		Price		Contractual
	Shares	Per Share		Term (In Years)
Options outstanding at December 31, 2020	3,042,229	$	28.93	8.2
Granted	1,350,210	$	28.16
Exercised	(192,464)	$	9.53
Canceled	(70,349)	$	35.62
Options outstanding at September 30, 2021	4,129,626	$	29.46	8.2
Options vested and expected to vest at September 30, 2021	3,982,965	$	29.81	8.2
Options exercisable at September 30, 2021	1,387,147	$	51.75	6.7
Shares available for grant under the 2021 Plan	3,319,116

The weighted average grant-date fair value of stock options granted during the three and nine months ended September 30, 2021 was $41.34 and $21.86, respectively.

The aggregate intrinsic value of stock options vested and expected to vest at September 30, 2021 was $140.6 million. The aggregate intrinsic value of stock options exercisable at September 30, 2021 was $47.3 million. As of September 30, 2021, total compensation cost related to non-vested employee, consultant and non-employee director stock options not yet recognized was approximately $33.7 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 nine months ended September 30, 2021 and 2020 was recorded as follows:

	Three months ended September 30,				Nine months ended September 30,
	2021		2020		2021		2020
	(In thousands)				(In thousands)
Research and development	$	1,504	$	642	$	2,927	$	1,294
General and administrative		1,525		608		2,886		1,364
Total stock-based compensation expense	$	3,029	$	1,250	$	5,813	$	2,658

The fair values of employee, consultant and non-employee director stock options granted during the three and nine months ended September 30, 2021 and 2020 were valued using the Black-Scholes option pricing model with the following assumptions:

	Three months ended September 30,		Nine months ended September 30,
	2021	2020	2021	2020
Expected stock price volatility	98%	98%	97 – 98%	91 – 98%
Expected option term	6.0 Years	6.0 Years	6.0 Years	6.0 Years
Risk-free interest rate	1.1 – 1.2%	0.5%	0.8 – 1.3%	0.5 – 0.6%
Expected dividend yield	None	None	None	None