Stock Based Compensation (Tables)

9 Months Ended

Sep. 30, 2014

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 September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
Research and development — employee	$	213,180	$	52,492	$	622,818	$	156,247
General and administrative — employee		380,274		202,827		1,017,613		590,056
Total employee stock-based compensation	$	593,454	$	255,319	$	1,640,431	$	746,303

Research and development — non-employee	$	—	$	—	$	86,539	$	—
General and administrative — non-employee		24,228		271,594		376,849		450,880
Total non-employee stock-based compensation	$	24,228	$	271,594	$	463,388	$	450,880

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

During the nine-month period ended September 30, 2014, the Company granted stock options to purchase 362,500 shares of its common stock and issued warrants to purchase 25,000 shares of its stock with an exercise of $5.60. The fair value of the stock options and warrants was estimated using the Black-Scholes option-pricing model, based on the following assumptions:

	Nine Months Ended September 30, 2014			Nine Months Ended September 30, 2013
Risk-free interest rate		1.98	%		1.36	%
Expected volatility		83.9% - 89.6	%		84.5% - 85.8	%
Expected lives (years)		6 - 10			5 - 6
Expected dividend yield		0.00	%		0.00	%

Schedule of share-based compensation, stock options, activity

As of September 30, 2014, there remained approximately $3.9 million of unrecognized compensation expense related to unvested stock options granted to current and former employees and directors, which is expected will be recognized over a weighted-average period of 1.03 years. Presented below is the Company’s stock option activity:

	Nine Months Ended September 30, 2014
	Number of Options (Employees)			Number of Options (Non-Employees)			Total Number of Options			Weighted-Average Exercise Price
Outstanding at January 1, 2014		6,228,593			167,143			6,395,736		$	3.11
Granted		362,500			—			362,500		$	4.91
Exercised, forfeited or expired		(56,431	)		(25,000	)		(81,431	)	$	4.78
Outstanding at September 30, 2014		6,534,662			142,143			6,676,805		$	3.19
Options exercisable at September 30, 2014		3,989,640			142,143			4,131,783		$	3.53

Schedule of unvested stock options activity

A summary of the unvested stock options as of September 30, 2014, and changes during the nine-month period then ended, are presented below:

	Number of Options (Employees)			Number of Options (Non-Employees)		Total Number of Options			Weighted-Average Grant Date Fair Value per Share
Non-vested at January 1, 2014		3,102,873			—		3,102,873		$	1.66
Granted		362,500			—		362,500		$	3.61
Forfeited		(23,168	)		—		(23,168	)	$	1.98
Vested		(897,183	)		—		(897,183	)	$	1.78
Non-vested at September 30, 2014		2,545,022			—		2,545,022		$	1.89

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, 2014:

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		5,115,056		8.71	$	2.21		2,918,951		8.71	$	2.16
$	2.51 – $3.50		224,482		6.88	$	2.82		141,387		6.88	$	2.72
$	3.51 – $8.00		989,201		6.29	$	6.27		723,379		6.29	$	6.63
$	8.01 – $32.55		348,066		2.60	$	8.92		348,066		2.60	$	8.92
			6,676,805		7.97	$	3.19		4,131,783		7.97	$	3.53