Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2017

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

A summary of stock option activity for employee, director and nonemployee awards under all stock option plans during the three months ended March 31, 2017 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 at January 1, 2017		4,020,288		$	4.31		8.4	$	—
Granted		1,479,450		$	0.82
Exercised		—			—
Forfeited		(58,633	)	$	4.21

Outstanding at March 31, 2017		5,441,105		$	3.36		8.6	$	—

Options exercisable at March 31, 2017		1,913,734		$	5.03		7.7	$	—

Options vested and expected to vest at March 31, 2017		4,956,695		$	3.56		8.5	$	—

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 ended March 31, 2017 and 2016 are as follows:


	Three Months Ended March 31,
	2017			2016
Expected life		4.6 years		5.9-6.1 years
Risk-free interest rate		1.8	%	1.3%-1.9%
Expected volatility		67	%	61%
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 fair value of the grants is being expensed over the vesting period of the options on a straight-line basis as the services are being provided. The Black-Scholes assumptions used to estimate fair value for the three months ended March 31, 2017 and 2016 were as follows:


	Three Months Ended March 31,
	2017	2016
Expected life	4.6-9.8 years	6.9-9.7 years
Risk-free interest rate	1.8%-2.4%	1.7%-2.0%
Expected volatility	67%-117%	60%-61%
Expected dividend rate	— %	— %