STOCKHOLDERS’ EQUITY / DEFICIT (Tables)

12 Months Ended

Dec. 31, 2015

Assumptions used in Black-Scholes options pricing model

The following weighted average assumptions were used in the Black-Scholes options pricing model to estimate the fair value of stock options for the specified reporting periods:



	Year Ended December 31, 2015		Year Ended December 31, 2014		Year Ended December 31, 2013
Risk free rate	1.53	%	1.55	%	1.51	%
Expected volatility	83	%	85	%	102	%
Expected life (in years)	5.8		5.8		5.8
Expected dividend yield	—		—		—

Schedule of stock option activity

The following table summarizes our stock option activity and related information for the year ended December 31, 2015:



			Weighted Average
	Shares Underlying Options		Exercise Price		Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Exercisable at December 31, 2014	1,225,833		$	9.73	7.96	$	3,395

Outstanding at December 31, 2014	4,892,208		$	10.93	8.57	$	8,353
Granted	2,285,000		$	27.15	—	—
Forfeited and expired	(970,170	)	14.91		—	—
Exercised	(541,454	)	13.10		—	—
Outstanding at December 31, 2015	5,665,584		$	17.05	8.75	$	31,542
Exercisable at December 31, 2015	2,036,906		$	12.55	8.34	$	15,582

Schedule of share based compensation expenses

Total non-cash stock-based compensation expense consisted of the following for the years ended December 31, 2015 and 2014 (in thousands):



	Year Ended December 31,
	2015		2014		2013
Selling, general and administrative expenses	$	16,483	$	10,940	$	2,651
Research and development expenses	9,417		4,960		259
Total	$	25,900	$	15,900	$	2,910

Schedule of unvested restricted shares

Unvested restricted shares consist of the following as of December 31, 2015:



	Number of shares		Weighted Average Grant Date Fair Value
Unvested December 31, 2014	691,668		$	10.83
Granted	273,000		26.97
Vested	(478,334	)	11.56
Forfeited/cancelled	(56,668	)	13.97
Unvested December 31, 2015	429,666		$	20.38