Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Share-based Compensation, Activity [Table Text Block]

Share-based compensation expense included in the statements of operations for the three months ended March 31, 2014 and 2013 was as follows:

	Three Months Ended March 31,
	2014		2013
Research and development expenses	$	233,573	$	206,480
General and administrative expenses		2,207,426		270,231
Total	$	2,440,999	$	476,711

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

Stock Options A summary of stock option activity during the three months ended March 31, 2014 and related information is included in the table below:

	Number of Options	Weighted-  Average  Exercise  Price		Weighted-  Average  Remaining  Contractual  Life (in years)	Aggregate  Intrinsic Value
Outstanding at January 1, 2014	18,577,207	$	1.79	5.8	$	24,000,710
Granted	408,482	$	3.22
Exercised	(304,097)	$	1.44		$	1,247,250
Forfeited	(220,903)	$	0.62
Outstanding at March 31, 2014	18,460,689	$	1.85	5.8	$	43,269,029
Exercisable at March 31, 2014	12,895,445	$	2.13	4.6	$	26,589,447
Vested and expected to vest	18,460,689	$	1.85	5.8	$	43,269,029

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]

Range of Exercise Prices		Number of Options Outstanding	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value
	$0.50 - $1.00	7,000,000	$	0.80	6.3	$	23,730,000
	$1.01 - $2.00	4,281,837	$	1.19	7.4		12,846,782
	$2.01 - $3.00	2,067,037	$	2.48	5.2		3,527,937
	$3.01 - $4.00	5,111,815	$	3.57	4.0		3,164,310
		18,460,689	$	1.85	5.8	$	43,269,029

Schedule Of Share Based Payment Award Stock Options Valuation Assumptions Black Sholes Model [Table Text Block]

Significant assumptions used in these models include:

	Three Months Ended March 31,
	2014	2013
Annual dividend	-	-
Expected life (in years)	4.0 - 8.5	3.0 - 6.0
Risk free interest rate	1.12% - 2.50%	0.51% - 1.01%
Expected volatility	68.8% - 100.0%	65.1% - 75.2%

Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]

A summary of our restricted stock unit activity for the three months ended March 31, 2014 is as follows:

	Number of RSU's	Weighted-  Average  Grant Date  Fair Value
Outstanding at January 1, 2014	401,625	$	2.03
Granted	25,000	$	3.33
Vested and converted to common shares	-	$	-
Forfeited	-	$	-
Outstanding at March 31, 2014	426,625	$	2.11
Exercisable at March 31, 2014	404,397	$	2.09

Schedule Of Share Based Compensation Warrant Activity [Table Text Block]

A summary of warrant activity for the three months ended March 31, 2014 follows:

	Number of Warrants	Weighted- Average Exercised Price		Weighted- Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value
Outstanding at January 1, 2014	19,586,819	$	1.96	3.4	$	21,146,495
Granted	3,436,435	$	3.64	4.8
Exercised	(1,486,573)	$	1.30
Forfeited	(231,664)	$	1.19
Outstanding at March 31, 2014	21,305,017	$	2.29	3.5	$	41,358,464
Exercisable at March 31, 2014	21,305,017	$	2.29	3.5	$	41,358,464