STOCKHOLDERS' EQUITY (Tables)

12 Months Ended

Dec. 31, 2015

Stock-based compensation expense recognized under ASC 718 was as follows:

	December 31,
	2015		2014		2013
Research and development	$	-	$	-	$	92,249
General and administrative		105,782		21,416		19,387
Total stock-based compensation expense	$	105,782	$	21,416	$	111,636

The following table presents the assumptions used to estimate the fair values of the stock options granted in the periods presented:

The summary of the stock options activity is as follows for year ended:

	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value
Outstanding at January 1, 2014		1,167,000		$	9.03		3.65	$	15,420,965
Grants		15,000			26.48		10.00		-
Exercised		(407,042	)		5.27		-		11,559,689
Forfeitures or expirations		(15,000	)		26.48		-		-
Outstanding at January 1, 2015		759,958			11.04		3.12		23,483,235
Grants		30,000			37.64		10.00		-
Exercised		(227,958	)		12.39		-		9,251,027
Forfeitures or expirations		-			-		-		-
Outstanding at December 31, 2015		562,000			11.91		2.51		17,456,220

Vested and expected to vest at December 31, 2015		562,000			11.91		2.51		17,456,220
Exercisable at December 31, 2015		504,500		$	9.60		1.97	$	16,833,170

The following table summarizes information relating to stock options by exercise price at December 31, 2015:

		Outstanding Shares						Exercisable Shares
Option Exercise Price		Number of Shares		Weighted Average Life (years)		Weighted Average Exercise Price		Number of Shares		Weighted Average Option Price		Weighted Average Life (years)
$	0.83 - 1.00		225,000		0.41	$	0.91		225,000	$	0.91		0.41
	4.00 - 5.50		50,000		1.70		5.22		50,000		5.22		1.70
	13.24 - 15.85		65,000		4.39		14.50		65,000		14.50		4.39
	17.00 - 21.00		145,000		3.38		19.48		137,500		19.57		3.14
	26.43 - 37.64		77,000		5.98		31.95		27,000		27.67		3.79
			562,000		2.51	$	11.91		504,500	$	9.60		1.97