STOCK-BASED COMPENSATION (Tables)

6 Months Ended

Jun. 30, 2013

STOCK-BASED COMPENSATION

Summary of option activity

	Number of		Weighted Average
	Shares		Exercise Price
Outstanding at December 31, 2012	5,579,042		$	6.68
Granted	903,915		1.67
Exercised	(7,550	)	1.82
Forfeited	(127,693	)	3.69
Expired	(173,871	)	10.09
Outstanding at June 30, 2013	6,173,843		5.91
Options exercisable at June 30, 2013	3,458,023		$	8.28
Weighted average grant date fair value of options granted during the six months ended June 30, 2013			$	1.18

Schedule of assumptions used in determining fair value of stock options granted using the Black-Scholes option pricing model

	Six Months Ended
	June 30,
	2013	2012
Expected dividend yield	—	—
Risk-free rate	0.71% - 1.49%	0.67% - 1.15%
Expected option term (in years)	6.0	5.3 – 5.5
Volatility	84% - 85%	85% - 87%