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Stock-Based Compensation

6 Months Ended

Jun. 30, 2021

Note 11—Stock-Based Compensation

Our stock option plans provide for the grant of incentive and non-qualified stock options, restricted stock awards, warrants and other stock awards to employees, non-employee directors and consultants.

In July 2021, annual stock option grants exercisable for a total of approximately 2.1 million shares of common stock were awarded to eligible participants for the 2020 annual performance period. The options have an exercise price of $14.99 per share and vest monthly on a straight-line basis over four years.

Stock-based compensation expense is as follows:


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020

	(In thousands)
Research and development	$	1,410	$	1,631	$	2,890	$	3,078
Selling, general and administrative		1,707		2,191		3,498		4,220
Total	$	3,117	$	3,822	$	6,388	$	7,298

The fair value of each option grant is estimated on the date of grant using the Black-Scholes option-pricing model. The following assumptions were applied to all stock option grants:


	Three Months Ended			Six Months Ended
	June 30, 2021			June 30, 2021
Estimated weighted-average fair value	$	11.29		$	12.79
Weighted-average assumptions:
Expected volatility		81	%		81	%
Expected life, in years		6.1			6.1
Risk-free interest rate		0.98	%		0.89	%
Expected dividend yield		—	%		—	%

Stock option activity for all stock plans and related information is as follows:


		Weighted-
		Average			Aggregate
		Exercise		Remaining	Intrinsic
	Options	Price per		Contractual Life	Value
	Outstanding	Share		(In years)	(In thousands)
Balance at December 31, 2020	11,938,528	$	11.92
Granted	307,450		18.53
Exercised	(794,808)		9.40
Forfeited	(135,617)		15.42
Balance at June 30, 2021	11,315,553	$	12.24	5.7	$	33,730
Vested and expected to vest at June 30, 2021	11,019,841	$	12.20	5.6	$	33,217
Exercisable at June 30, 2021	8,719,802	$	11.82	4.9	$	29,075

As of June 30, 2021, there were 2.6 million unvested options outstanding that will vest over a weighted-average period of 2.3 years. The total estimated compensation expense yet to be recognized on outstanding options is $20.2 million.