Stock Based Compensation (Tables)

3 Months Ended

Mar. 31, 2013

Stock Based Compensation [Abstract]

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,
	2013		2012
Research and development — employee	$	50,172	$	95,124
General and administrative — employee		184,640		174,072
Total employee stock-based compensation	$	234,812	$	269,196
Research and development — non-employee	$	—	$	—
General and administrative — non-employee		27,212		52,418
Total non-employee stock-based compensation	$	27,212	$	52,418

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

During the three-month period ended March 31, 2013, the Company issued stock options to purchase 89,176 shares of its common stock. The fair value of the stock options 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, 2013
Risk-free interest rate		1.16	%
Expected volatility		85.4% - 85.8	%
Expected lives (years)		6
Expected dividend yield		0.00	%

Schedule of share-based compensation, stock options, activity

As of March 31, 2013, there remained approximately $1.6 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 1.25 years. Presented below is the Company's stock option activity:

	Three Months Ended March 31, 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		89,176			—		89,176		$	2.45
Forfeited or expired		(103,716	)		—		(103,716	)	$	3.08
Outstanding at March 31, 2013		3,226,310			142,143		3,368,453		$	4.16
Options exercisable at March 31, 2013		2,020,696			133,215		2,153,911		$	5.28

Schedule of unvested stock options activity

A summary of the unvested stock options as of March 31, 2013, and changes during the three-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		89,176			—		89,176		$	1.75
Forfeited or expired		(103,716	)		—		(103,716	)	$	2.32
Vested		(102,236	)		—		(102,236	)	$	1.90
Non-vested at March 31, 2013		1,205,613			8,929		1,214,542		$	1.69

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, 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		2,115,545		9.26	$	1.98		962,073		9.26	$	2.03
$	3.01 –7.00		178,512		5.02	$	5.24		174,869		5.02	$	5.27
$	7.01 –8.50		942,110		4.88	$	7.66		884,683		4.88	$	7.69
$	8.51 – 32.55		132,286		1.58	$	12.75		132,286		1.58	$	12.75
			3,368,453		7.49	$	4.16		2,153,911		7.49	$	5.28