Stock Based Compensation (Tables)

6 Months Ended

Jun. 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 interim statements of operations:

	Three Months Ended June 30,				Six Months Ended June 30,
	2015		2014		2015		2014
Research and development — employee	$	392,842	$	234,484	$	728,780	$	409,638
General and administrative — employee		1,744,440		325,379		2,699,844		637,339
Total employee stock-based compensation	$	2,137,282	$	559,863	$	3,428,624	$	1,046,977

Research and development — non-employee	$	—	$	—	$	—	$	—
General and administrative — non-employee		140,533		160,629		234,084		352,620
Total non-employee stock-based compensation	$	140,533	$	160,629	$	234,084	$	352,620

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:

	Six Months Ended June 30, 2015			Six Months Ended June 30, 2014
Risk-free interest rate		2.21	%		1.92	%
Expected volatility		78.2% - 84.4	%		87.0% - 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:

	Six Months Ended June 30, 2015
	Number of Options (Employees)			Number of Options (Non-Employees)			Total Number of Options			Weighted-Average Exercise Price
Outstanding at January 1, 2015		9,348,952			692,143			10,040,735		$	2.87
Granted		550,000			—			550,000		$	3.86
Expired		(68,000	)		(56,429	)		(124,429	)	$	6.90
Outstanding at June 30, 2015		9,830,952			635,714			10,466,306		$	3.33
Options exercisable at June 30, 2015		6,276,275			635,714			6,911,989		$	3.59

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 June 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		5,837,558		8.51	$	2.12		3,226,398		8.00	$	2.08
$	2.51 – $3.50		954,482		8.64	$	2.85		874,482		8.62	$	2.83
$	3.51 – $8.00		3,386,201		7.93	$	5.06		2,523,043		7.74	$	5.16
$	8.01 – $32.55		288,065		2.31	$	9.00		288,066		2.31	$	9.00
			10,466,306		8.16	$	3.33		6,911,989		7.74	$	3.59