Stock-Based Compensation

9 Months Ended

Sep. 30, 2017

Stock-Based Compensation

Stock-Based Compensation

(8)  Stock-Based Compensation

A summary of stock option activity for the nine months ended September 30, 2017 is as follows:

	Shares		Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (In Years)
Options Outstanding at December 31, 2016	10,218,710		$	11.14	6.5
Granted	2,309,900		$	2.34
Exercised	—		$	—
Canceled	(945,792	)	$	9.21
Options Outstanding at September 30, 2017	11,582,818		$	9.54	5.9
Options Vested and Expected to Vest at September 30, 2017	11,460,583		$	9.59	5.8
Options Exercisable at September 30, 2017	7,360,799		$	11.05	4.1
Shares Available for Grant Under the 2008 Plan	7,780,663

The weighted average grant-date fair value of stock options granted during the nine month period ended September 30, 2017 was $1.57. Stock-based compensation expense for the three and nine months ended September 30, 2017 and 2016 was recorded as follows:

	Three months ended September 30,				Nine months ended September 30,
	2017		2016		2017		2016
	(In thousands)
Research and development	$	1,546	$	2,042	$	5,310	$	5,866
General and administrative	1,193		1,754		4,418		5,843
Total stock-based compensation expense	$	2,739	$	3,796	$	9,728	$	11,709

The fair value of employee and director stock options granted during the three and nine month periods ended September 30, 2017 and 2016 were valued using the Black-Scholes option-pricing model with the following assumptions:

	Three months ended September 30,				Nine months ended September 30,
	2017		2016		2017		2016
Expected stock price volatility	76	%	76	%	76 — 77	%	70 — 77	%
Expected option term	6.0 years		6.0 years		6.0 years		6.0 years
Risk-free interest rate	2.0	%	1.4	%	2.0 — 2.3	%	1.4 — 1.6	%
Expected dividend yield	None		None		None		None