Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2016

Summary of Stock Option Activity for Employee, Director and Nonemployee Awards

Stock Options

A summary of stock option activity for employee, director and nonemployee awards under all stock option plans during the three months ended March 31, 2016 is presented below (Aggregate Intrinsic Value in thousands):

	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
Outstanding — January 1, 2016		3,454,926		$	5.39		8.9	$	—
Granted		547,070			2.98
Exercised		—			—
Forfeited		(10,410	)		4.88
Outstanding — March 31, 2016		3,991,586		$	5.06		8.8	$	19
Options expected to vest — March 31, 2016		2,695,996		$	4.79		9.3	$	18
Options exercisable — March 31, 2016		1,159,945		$	5.72		7.7	$	—

Summary of Assumptions Used in Black-Scholes Option-Pricing Model for Stock Options Granted to Employees, Directors and Non Employees

The assumptions used in the Black-Scholes option-pricing model for stock options granted to employees and to directors in respect of board services during the three months ended March 31, 2016 and 2015 are as follows:

	Three Months Ended March 31,
	2016	2015
Expected life	5.9-6.1 years	6 years
Risk-free interest rate	1.31%-1.89%	1.45%-1.69%
Expected volatility	61%	61%-63%
Expected dividend rate	—%	—%

Non Employee Awards [Member]

Summary of Assumptions Used in Black-Scholes Option-Pricing Model for Stock Options Granted to Employees, Directors and Non Employees

The Black-Scholes assumptions used to estimate fair value for the three months ended March 31, 2016 and 2015 were as follows:

	Three Months Ended March 31,
	2016	2015
Expected life	6.9-9.7 years	8 years
Risk-free interest rate	1.7%-2.0%	1.86%
Expected volatility	60%-61%	62%
Expected dividend rate	—%	—%