Stock-Based Compensation

3 Months Ended

Mar. 31, 2018

Stock-Based Compensation

Stock-Based Compensation

(9)  Stock-Based Compensation

A summary of stock option activity for the three months ended March 31, 2018 is as follows:

	Shares		Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (In Years)
Options Outstanding at December 31, 2017	10,856,212		$	9.40	6.1
Granted	18,000		$	2.82
Exercised	(104,500	)	$	2.80
Canceled	(1,313,031	)	$	8.83
Options Outstanding at March 31, 2018	9,456,681		$	9.55	6.5
Options Vested and Expected to Vest at March 31, 2018	9,313,514		$	9.62	6.5
Options Exercisable at March 31, 2018	5,827,235		$	11.85	5.2
Shares Available for Grant Under the 2008 Plan	8,879,518

The weighted average grant-date fair value of stock options granted during the three-month period ended March 31, 2018 was $1.86. Stock-based compensation expense for the three months ended March 31, 2018 and 2017 was recorded as follows:

	Three months ended March 31,
	2018		2017
	(In thousands)
Research and development	$	1,311	$	1,893
General and administrative	1,177		1,646
Total stock-based compensation expense	$	2,488	$	3,539

The fair values of employee and director stock options granted during the three months ended March 31, 2018 and 2017 were valued using the Black-Scholes option pricing model with the following assumptions:

	Three months ended March 31,
	2018	2017
Expected stock price volatility	73%	76 - 77%
Expected option term	6.0 Years	6.0 Years
Risk-free interest rate	2.8%	2.3%
Expected dividend yield	None	None