STOCK-BASED COMPENSATION (Tables)

3 Months Ended

Mar. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of weighted average assumptions used to estimate fair value of each service-based stock option grant

The fair value of each service-based stock option grant for the reported periods is estimated on the date of the grant using the Black-Scholes option-pricing model using the weighted average assumptions noted in the following table.

	Three Months Ended March 31,
Service-Based Stock Options	2016		2015
Expected dividend rate	—	%	—	%
Expected stock price volatility	78.7 – 85.5%		80.3 – 88.1%
Risk-free interest rate	1.3 – 1.8%		1.5 – 1.9%
Expected life (years)	6.1 – 6.3		5.5 – 6.3

Summary of activity for service-based stock options

The following table summarizes the activity for service-based stock options for the indicated periods:

Service-Based Stock Options	Options	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Outstanding at December 31, 2015	2,523,400	$	6.36	8.7	$	5,000
Granted	835,480	$	3.09
Exercised	38,919	$	3.06		$	76,687
Expired	34,187	$	49.45
Forfeited	72,340	$	3.94
Outstanding at March 31, 2016	3,213,434	$	5.14	8.8	$	8,116,912
Exercisable at March 31, 2016	739,346	$	11.20	7.4	$	1,430,199