(10) Stock-Based Compensation

A summary of stock option activity for the nine months ended September 30, 2019 is as follows:


		Weighted		Weighted
		Average		Average
		Exercise		Remaining
		Price		Contractual
	Shares	Per Share		Term (In Years)
Options Outstanding at December 31, 2018	866,132	$	93.70	7.1
Granted	926,840		2.78
Exercised	—		—
Canceled	(68,214)		85.89
Options Outstanding at September 30, 2019	1,724,758		45.15	8.2
Options Vested and Expected to Vest at September 30, 2019	1,585,308		48.71	8.1
Options Exercisable at September 30, 2019	551,716		127.95	5.6
Shares Available for Grant Under the 2008 Plan	398,707

The weighted average grant-date fair value of stock options granted during the three and nine month periods ended September 30, 2019 was $2.00 and $2.08, respectively. Stock-based compensation expense for the three and nine month periods ended September 30, 2019 and 2018 was recorded as follows:


	Three months ended September 30,				Nine months ended September 30,
	2019		2018		2019		2018
	(In thousands)				(In thousands)
Research and development	$	330	$	799	$	1,740	$	3,088
General and administrative		377		994		2,124		3,241
Total stock-based compensation expense	$	707	$	1,793	$	3,864	$	6,329

The fair values of employee and director stock options granted during the three and nine month periods ended September 30, 2019 and 2018 were valued using the Black-Scholes option pricing model with the following assumptions:


	Three months ended September 30,				Nine months ended September 30,
	2019		2018		2019		2018
Expected stock price volatility	91	%	85	%	91	%	73 - 85	%
Expected option term	6.0	Years	6.0	Years	6.0	Years	6.0	Years
Risk-free interest rate	1.6 -1.9	%	2.8	%	1.6 - 2.5	%	2.8 - 3.0	%
Expected dividend yield	None		None		None		None