Stock-Based Compensation

9 Months Ended

Sep. 30, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

9. Stock-Based Compensation

Stock Options

Activities under the Company’s stock option plans for the nine months ended September 30, 2021 were as follows:

	Options Outstanding
	Number of  Options			Weighted- Average Exercise Price Per Share
Balances at December 31, 2020		10,929,530		$	10.77
Options granted		4,107,097			7.50
Options exercised		(483,591	)		2.69
Option forfeited/expired		(3,047,079	)		11.42
Balances at September 30, 2021		11,505,957		$	9.77
Options exercisable at September 30, 2021		5,708,010		$	11.63

Stock-based Compensation

Total stock-based compensation recorded related to options granted to employees and non-employees and employee stock purchase plan was as follows:

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2021		2020		2021		2020
	(in thousands)
Stock-based compensation expense:
Research and development	$	1,328	$	1,735	$	4,213	$	5,317
General and administrative		1,836		2,106		5,410		6,050
Total stock-based compensation expense	$	3,164	$	3,841	$	9,623	$	11,367