Stock Based Compensation (Tables)

9 Months Ended

Sep. 30, 2015

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 unaudited Condensed Statements of Operations:

	Three Months Ended September 30,					Nine Months Ended September 30,
	2015			2014		2015		2014
Research and development — employee	$	402,292		$	213,180	$	1,131,072	$	622,818
General and administrative — employee		482,954			380,274		3,182,798		1,017,613
Total employee stock-based compensation	$	885,246		$	593,454	$	4,313,870	$	1,640,431

Research and development — non-employee	$	—		$	—	$	—	$	86,539
General and administrative — non-employee		(27,647	)		24,228		206,437		376,849
Total non-employee stock-based compensation	$	(27,647	)	$	24,228	$	206,437	$	463,388

Schedule of share-based payment award, fair value of the stock options granted , assumptions

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

	Nine Months Ended September 30,2015			Nine Months Ended September 30, 2014
Risk-free interest rate		2.21	%		1.98	%
Expected volatility		78.2% - 84.4	%		83.9% - 89.6	%
Expected lives (years)		6 - 10			6 - 10
Expected dividend yield		0.00	%		0.00	%

Schedule of share-based compensation, stock options, activity

Presented below is the Company’s stock option activity:

	Nine Months Ended September 30, 2015
	Number of Options (Employees)			Number of Options (Non-Employees)			Total Number of Options			Weighted-Average Exercise Price
Outstanding at January 1, 2015		9,348,592			692,143			10,040,735		$	2.87
Granted		550,000			—			550,000		$	3.86
Exercised		(287,143	)		—			(287,143	)	$	2.05
Expired		(77,587	)		(56,429	)		(134,016	)	$	6.82
Outstanding at September 30, 2015		9,533,862			635,714			10,169,576		$	3.36
Options exercisable at September 30, 2015		6,454,764			635,714			7,090,478		$	3.61

Schedule of share-based compensation, summarizes significant ranges of outstanding stock options

The following table summarizes significant ranges of outstanding stock options under the Company’s plans at September 30, 2015:

Range of Exercise Prices		Total Number of Options		Weighted-Average Remaining Contractual Life (years)		Weighted-Average Exercise Price		Total Number of Options Exercisable		Weighted-Average Remaining Contractual Life (years)		Weighted-Average Exercise Price
$	1.83 - $2.50		5,557,558		8.24	$	2.13		3,242,079		7.75	$	2.09
$	2.51 – $3.50		947,339		8.41	$	2.85		897,340		8.39	$	2.84
$	3.51 – $8.00		3,376,614		7.70	$	5.06		2,662,994		7.55	$	5.13
$	8.01 – $32.55		288,065		2.06	$	9.00		288,065		2.06	$	9.00
			10,169,576		7.90	$	3.36		7,090,478		7.56	$	3.61