Stock Based Compensation (Tables)

3 Months Ended

Mar. 31, 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 March 31,
	2015		2014
Research and development — employee	$	335,938	$	175,153
General and administrative — employee		955,404		311,960
Total employee stock-based compensation	$	1,291,342	$	487,113

Research and development — non-employee	$	—	$	86,539
General and administrative — non-employee		93,551		191,992
Total non-employee stock-based compensation	$	93,551	$	278,531

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

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

	Three months Ended March 31, 2015			Three Months Ended March 31, 2014
Risk-free interest rate		2.20	%		1.98	%
Expected volatility		84.3	%		87.8% - 89.6	%
Expected lives (years)		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:

	Three months Ended March 31, 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		180,000		—			180,000		$	3.15
Exercised, forfeited or expired		—		(56,429	)		(56,429	)	$	8.54
Outstanding at March 31, 2015		9,528,592		635,714			10,164,306		$	2.84
Options exercisable at March 31, 2015		5,528,887		635,714			6,164,601		$	3.14

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 March 31, 2015:

Range of Exercise Prices		Number of Options		Weighted-Average Remaining Contractual Life (years)		Weighted-Average Exercise Price		Number of Options Exercisable		Weighted-Average Remaining Contractual Life (years)		Weighted-Average Exercise Price
$	1.83 - $2.50		7,932,556		8.74	$	2.19		4,212,622		8.33	$	2.17
$	2.51 – $3.50		954,482		8.89	$	2.85		873,054		8.87	$	2.83
$	3.51 – $8.00		989,201		5.79	$	6.27		790,858		5.01	$	6.50
$	8.01 – $32.55		288,067		2.56	$	9.00		288,067		2.56	$	9.00
			10,164,306		8.29	$	2.84		6,164,601		7.71	$	3.14