(9) Stock-Based Compensation

A summary of stock option activity for the six months ended June 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	1,439,175	$	10.36
Exercised	—		—
Canceled	(53,090)	$	46.03
Options Outstanding at June 30, 2020	3,085,287	$	28.76	8.69
Options Vested and Expected to Vest at June 30, 2020	2,875,684	$	30.23	8.62
Options Exercisable at June 30, 2020	821,537	$	84.93	6.39
Shares Available for Grant Under the 2008 Plan	938,178

The weighted average grant-date fair value of stock options granted during the three and six month period ended June 30, 2020 was $7.96 and $7.95, respectively. Stock-based compensation expense for the three and six months ended June 30, 2020 and 2019 was recorded as follows:


	Three months ended June 30,				Six months ended June 30,
	2020		2019		2020		2019
	(In thousands)				(In thousands)
Research and development	$	342	$	654	$	652	$	1,410
General and administrative		380		810		756		1,747
Total stock-based compensation expense	$	722	$	1,464	$	1,408	$	3,157

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


	Three months ended June 30,				Six months ended June 30,
	2020		2019		2020		2019
Expected stock price volatility	97	%	91	%	91 - 97	%	91	%
Expected option term	6.0	Years	6.0	Years	6.0	Years	6.0	Years
Risk-free interest rate	0.5	%	1.9 - 2.4	%	0.5 - 0.6	%	1.9 - 2.5	%
Expected dividend yield	None		None		None		None