Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 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	15,100		$	3.49
Exercised	—		$	—
Canceled	(74,680	)	$	13.79
Options Outstanding at March 31, 2017	10,159,130		$	11.11	6.3
Options Vested and Expected to Vest at March 31, 2017	10,069,706		$	11.12	6.3
Options Exercisable at March 31, 2017	6,340,993		$	11.14	4.9
Shares Available for Grant under the 2008 Plan	3,635,563

Schedule of stock-based compensation expense

	Three months ended March 31,
	2017		2016
	(In thousands)
Research and development	$	1,893	$	1,815
General and administrative	1,646		2,125
Total stock-based compensation expense	$	3,539	$	3,940

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

	Three months ended March 31,
	2017		2016
Expected stock price volatility	76 - 77	%	70	%
Expected option term	6.0 Years		6.0 Years
Risk-free interest rate	2.3	%	1.6	%
Expected dividend yield	None		None