Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2017

Stock-Based Compensation

Summary of stock option activity

	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

Schedule of stock-based compensation expense

	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

Schedule of assumptions used for the fair value of employee and director stock options granted

	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