Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2023

Stock-Based Compensation

Summary of stock option activity

		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

Schedule of stock-based compensation expense

	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

Schedule of assumptions used for the fair value of employee stock options granted

	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