Stock Options and Equity-Classified Warrants (Tables)

12 Months Ended

Dec. 31, 2015

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of total stock-based compensation expense from stock options and warrants

The following table sets forth the total stock-based compensation expense resulting from stock options and warrants included in the Company’s Statements of Operations:

	Years Ended December 31,
	2015		2014		2013
Research and development - employee	$	1,590,267	$	932,482	$	241,459
General and administrative - employee		5,568,537		2,383,624		2,659,105
Total employee stock-based compensation	$	7,158,804	$	3,316,106	$	2,900,564
Research and development – non-employee	$	—	$	86,539	$	—
General and administrative – non-employee		225,852		1,736,703		898,153
Total non-employee stock-based compensation	$	225,852	$	1,823,242	$	898,153

Significant Ranges of Outstanding Stock Options and Warrants

The following table summarizes significant ranges of outstanding stock options under the two plans at December 31, 2015:

Range of Exercise Prices		Number of Options		Weighted Average RemainingContractual Life (years)		Weighted Average Exercise Price		Number of Options Exercisable		Weighted Average Contractual Life		Weighted Average Exercise Price
$	1.75 — 2.00		1,374,500		6.95	$	1.83		1,374,500		6.95	$	1.83
$	2.01 — 2.50		8,215,556		9.14		2.33		3,280,923		8.54		2.30
$	2.51 — 4.00		986,980		8.06		2.89		919,481		8.01		2.87
$	4.01 — 32.55		3,632,540		7.03		5.38		3,075,974		6.85		5.48
			14,209,576		8.31	$	3.10		8,650,878		7.63	$	3.42

Stock Options [Member] | Employees [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Fair Value Assumptions of Stock Options

The fair value of the stock options at the date of grant was estimated using the Black-Scholes option-pricing model, based on the following assumptions:

	2015			2014			2013
Risk-free interest rate		1.74% - 2.42	%		1.74% - 2.12	%		0.91% - 2.79	%
Expected volatility		74% - 85	%		82% - 90	%		85% - 89	%
Expected lives (years)		6 - 10			6 - 10			6 - 10
Expected dividend yield		0.00	%		0.00	%		0.00	%

Stock Options [Member] | Non-employees [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Fair Value Assumptions of Stock Options

The fair value of the stock options at the date of grant was estimated using the Black-Scholes option-pricing model, based on the following assumptions:

	2015		2014			2013
Risk-free interest rate		—		2.23	%		2.05	%
Expected volatility		—		85.0	%		84.8	%
Expected lives (years)		—		10			10
Expected dividend yield		—		0	%		0	%

Stock Options and Warrants Activity

Presented below is the Company’s non-employee stock option activity:

	Stock Options								Weighted Average Exercise Price
	2015			2014			2013		2015		2014		2013
Outstanding — beginning of year		692,143			167,143			142,143	$	3.47	$	5.69	$	6.20
Granted		—			550,000			25,000		—		2.76		2.79
Exercised		—			—			—		—		—		—
Expired/Forfeited		(56,429	)		(25,000	)		—		8.54		2.79		—
Outstanding — end of year		635,714			692,143			167,143		3.02		3.47		5.69
Exercisable at end of year		635,714			692,143			167,143	$	3.02	$	3.47	$	5.69
Weighted average fair value of stock options granted during the year:	$	—		$	2.32		$	1.98

Stock Options [Member] | Employees and Directors [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock Options and Warrants Activity

Presented below is the Company’s stock option activity for employees and directors:

	Stock Options									Weighted Average Exercise Price
	2015			2014			2013			2015		2014		2013
Outstanding — beginning of year		9,348,592			6,228,593			3,240,850		$	2.83	$	3.11	$	4.08
Granted		4,590,000			3,180,000			3,323,176			2.61		2.47		2.43
Exercised		(287,143	)		(1,667	)		(476	)		2.05		1.83		1.93
Forfeited		—			(24,333	)		(127,812	)		—		2.81		3.09
Expired		(77,587	)		(34,001	)		(207,145	)		5.58		8.18		9.59
Outstanding — end of year		13,573,862			9,348,592			6,228,593			3.11		2.83		3.11
Exercisable at end of year		8,015,164			4,901,511			3,125,720		$	3.45	$	3.22	$	3.86
Weighted average fair value of stock options granted during the year:	$	1.88		$	1.80		$	1.82

Warrants [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock Options and Warrants Activity

A summary of the Company’s warrant activity and related information for the years ended December 31 are shown below.

	Warrants									Weighted Average Exercise Price
	2015			2014			2013			2015		2014		2013
Outstanding — beginning of year		7,349,760			8,324,609			7,518,113		$	4.27	$	4.86	$	5.09
Granted		—			25,000			816,667			—		5.60		2.80
Exercised		(10,000	)		(340,527	)		(8,572	)		2.50		2.56		4.48
Forfeited		—			—			—			—		—		—
Expired		(114,288	)		(659,322	)		(1,599	)		3.82		12.66		14.99
Outstanding — end of year		7,225,472			7,349,760			8,324,609			4.28		4.27		4.86
Exercisable at end of year		7,225,472			7,149,760			7,924,609		$	4.28	$	4.32	$	4.98
Weighted average fair value of warrants granted during the year:	$	—		$	3.46		$	1.31

Significant Ranges of Outstanding Stock Options and Warrants

The following table summarizes additional information concerning warrants outstanding and exercisable at December 31, 2015:

		Warrants Outstanding
Range of Exercise Prices		Number of Shares		Weighted Average Remaining Contractual Life (years)		Weighted Average Exercise Price		Warrants Number of Shares Exercisable		Exercisable Weighted Average Exercise Price
$	2.10 — 2.60		578,573		2.32	$	2.42		578,573	$	2.42
$	2.61 — 3.60		125,000		2.86		3.00		125,000		3.00
$	3.61 — 4.60		6,496,899		0.63		4.47		6,496,899		4.47
$	4.61 — 5.60		25,000		8.21		5.60		25,000		5.60
			7,225,472		0.83	$	4.28		7,225,472	$	4.28