(9) Stock-Based Compensation

A summary of stock option activity for the nine months ended September 30, 2020 is as follows:


		Weighted		Weighted
		Average		Average
		Exercise		Remaining
		Price		Contractual
	Shares	Per Share		Term (In Years)
Options Outstanding at December 31, 2019	1,699,202	$	44.87	8.0
Granted	1,490,925	$	10.42
Exercised	(36,960)	$	3.85
Canceled	(78,335)	$	35.80
Options Outstanding at September 30, 2020	3,074,832	$	28.89	8.4
Options Vested and Expected to Vest at September 30, 2020	2,888,532	$	30.19	8.4
Options Exercisable at September 30, 2020	871,007	$	80.35	6.2
Shares Available for Grant Under the 2008 Plan	907,673

The weighted average grant-date fair value of stock options granted during the three and nine month period ended September 30, 2020 was $9.25 and $7.99, respectively. Stock-based compensation expense for the three and nine months ended September 30, 2020 and 2019 was recorded as follows:


	Three months ended September 30,				Nine months ended September 30,
	2020		2019		2020		2019
	(In thousands)				(In thousands)
Research and development	$	642	$	330	$	1,294	$	1,740
General and administrative		608		377		1,364		2,124
Total stock-based compensation expense	$	1,250	$	707	$	2,658	$	3,864

The fair values of employee and director stock options granted during the three and nine months ended September 30, 2020 and 2019 were valued using the Black-Scholes option pricing model with the following assumptions:


	Three months ended September 30,				Nine months ended September 30,
	2020		2019		2020		2019
Expected stock price volatility	98	%	91	%	91 - 98	%	91	%
Expected option term	6.0	Years	6.0	Years	6.0	Years	6.0	Years
Risk-free interest rate	0.5	%	1.6 - 1.9	%	0.5 - 0.6	%	1.6 - 2.5	%
Expected dividend yield	None		None		None		None