Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Stock-Based Compensation

Schedule of stock option activity

		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	1,383,410	$	28.55
Exercised	(259,322)	$	8.72
Canceled	(88,650)	$	31.89
Options outstanding at December 31, 2021	4,077,667	$	30.02	8.0
Options vested and expected to vest at December 31, 2021	3,952,611	$	30.31	8.0
Options exercisable at December 31, 2021	1,483,998	$	49.01	6.6
Shares available for grant under the 2021 Plan	3,304,217

Schedule of stock-based compensation expense

	2021		2020		2019
	(In thousands)
Research and development	$	4,525	$	1,933	$	2,053
General and administrative		4,428		1,982		2,498
Total stock-based compensation expense	$	8,953	$	3,915	$	4,551

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

	2021	2020	2019
Expected stock price volatility	97 - 98%	91 - 98%	90 - 91%
Expected option term	6.0 Years	6.0 Years	6.0 Years
Risk-free interest rate	0.8 - 1.4%	0.5 - 0.7%	1.6 - 2.5%
Expected dividend yield	None	None	None