Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 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	1,350,210	$	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

Schedule of stock-based compensation expense

	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

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

	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