Stock Based Compensation (Tables)

6 Months Ended

Jun. 30, 2013

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,
	2013		2012		2013		2012
Research and development — employee	$	53,583	$	98,242	$	103,755	$	193,366
General and administrative — employee		202,589		263,007		387,229		437,079
Total employee stock-based compensation	$	256,172	$	361,249	$	490,984	$	630,445

Research and development — non-employee	$	—	$	—	$	—	$	—
General and administrative — non-employee		152,074		176,074		179,286		228,492
Total non-employee stock-based compensation	$	152,074	$	176,074	$	179,286	$	228,492

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

During the six-month period ended June 30, 2013, the Company issued stock options to purchase 117,176 shares of its common stock. The fair value of the stock options granted in the current six-month period was estimated using the Black-Scholes option-pricing model, based on the following assumptions:

	Six Months Ended June 30, 2013			Six Months Ended June 30, 2012
Risk-free interest rate		1.11	%		1.54	%
Expected volatility		85.2% - 85.8	%		89.7% - 97.7	%
Expected lives (years)		6			6 - 10
Expected dividend yield		0.00	%		0.00	%

Schedule of share-based compensation, stock options, activity

As of June 30, 2013, there remained approximately $1.3 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 1.13 years. Presented below is the Company’s stock option activity:

	Six Months Ended June 30, 2013
	Number of Options (Employees)			Number of Options (Non-Employees)		Total Number of Options			Weighted-Average Exercise Price
Outstanding at January 1, 2013		3,240,850			142,143		3,382,993		$	4.17
Granted		92,176			25,000		117,176		$	2.52
Exercised		(476	)		—		(476	)	$	1.96
Forfeited or expired		(103,716	)		—		(103,716	)	$	3.08
Outstanding at June 30, 2013		3,228,834			167,143		3,395,977		$	4.15
Options exercisable at June 30, 2013		2,159,480			149,881		2,309,361		$	5.10

Schedule of unvested stock options activity

A summary of the unvested stock options as of June 30, 2013, and changes during the six-month period then ended, is 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, 2013		1,322,389			8,929			1,331,318		$	1.69
Granted		92,176			25,000			117,176		$	1.80
Forfeited or expired		(103,716	)		—			(103,716	)	$	2.32
Vested		(241,495	)		(16,667	)		(258,162	)	$	3.68
Non-vested at June 30, 2013		1,069,354			17,262			1,086,616		$	1.67

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, 2013:

Range of Exercise Prices		Number of Options		Weighted-Average Remaining Contractual Life (years)		Weighted-Average Exercise Price		Number of Options Exercisable		Weighted-Average Contractual Life		Weighted-Average Exercise Price
$	1.83 - 3.00		2,143,069		8.99	$	1.99		1,100,587		8.99	$	2.04
$	3.01 –7.00		178,512		4.77	$	5.24		176,036		4.77	$	5.26
$	7.01 –8.50		942,110		4.63	$	7.66		900,452		4.63	$	7.68
$	8.51 – 32.55		132,286		1.33	$	12.75		132,286		1.33	$	12.75
			3,395,977		7.26	$	4.15		2,309,361		7.26	$	5.10