Stock Based Compensation (Tables)

3 Months Ended

Mar. 31, 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 March 31,
	2014		2013
Research and development — employee	$	175,153	$	50,172
General and administrative — employee		311,960		184,640
Total employee stock-based compensation	$	487,113	$	234,812

Research and development — non-employee	$	86,539	$	—
General and administrative — non-employee		191,992		27,212
Total non-employee stock-based compensation	$	278,531	$	27,212

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

During the three-month period ended March 31, 2014, the Company issued stock options to purchase 270,000 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 granted in the current three-month period was estimated using the Black-Scholes option-pricing model, based on the following assumptions:

	Three Months Ended March 31, 2014			Three Months Ended March 31, 2013
Risk-free interest rate		1.98	%		1.16	%
Expected volatility		87.8% - 89.6	%		85.4% - 85.8	%
Expected lives (years)		6 - 10			6
Expected dividend yield		0.00	%		0.00	%

Schedule of share-based compensation, stock options, activity

As of March 31, 2014, there remained approximately $4.6 million of unrecognized compensation expense related to unvested stock options granted to current and former employees, directors and consultants, to be recognized as expense over a weighted-average period of 1.24 years. Presented below is the Company’s stock option activity:

	Three Months Ended March 31, 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		270,000				270,000	$	5.38
Outstanding at March 31, 2014		6,498,593		167,143		6,665,736	$	3.20
Options exercisable at March 31, 2014		3,406,261		167,143		3,573,404	$	3.74

Schedule of unvested stock options activity

A summary of the unvested stock options as of March 31, 2014, and changes during the three-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		270,000			—		270,000		$	3.97
Vested		(280,541	)		—		(280,541	)	$	1.68
Non-vested at March 31, 2014		3,092,332			—		3,092,332		$	1.86

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, 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		5,130,056		9.21	$	2.21		2,374,550		9.21	$	2.15
$	2.51 – $3.50		194,482		6.69	$	2.79		153,291		6.69	$	2.69
$	3.51 – $8.00		962,701		6.69	$	6.31		667,066		6.69	$	6.75
$	8.01 – $32.55		378,497		2.88	$	8.86		378,497		2.88	$	8.86
			6,665,736		8.41	$	3.20		3,573,404		8.41	$	3.74