Stock Based Compensation (Tables)

6 Months Ended

Jun. 30, 2016

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 our Condensed Statements of Operations:

	Three Months Ended June 30,				Six Months Ended June 30,
	2016		2015		2016		2015
Research and development — employee	$	507,195	$	392,842	$	988,006	$	728,780
General and administrative — employee		2,499,368		1,744,440		3,156,418		2,699,844
Total employee stock-based compensation	$	3,006,563	$	2,137,282	$	4,144,424	$	3,428,624
Research and development — non-employee	$	—	$	—	$	—	$	—
General and administrative — non-employee		32,506		140,533		220,462		234,084
Total non-employee stock-based compensation	$	32,506	$	140,533	$	220,462	$	234,084

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

The fair value of the stock options was estimated using the Black-Scholes option-pricing model, based on the following assumptions:

	Six Months Ended June 30, 2016			Six Months Ended June 30, 2015
Risk-free interest rate		1.47	%		2.21	%
Expected volatility		76.3	%		78.2% - 84.4	%
Expected lives (years)		5 - 10			6 - 10
Expected dividend yield		0.00	%		0.00	%

Schedule of share-based compensation, stock options, activity

Presented below is our stock option activity:

	Six Months Ended June 30, 2016
	Number of Options (Employees)			Number of Options (Non-Employees)		Total Number of Options			Weighted-Average Exercise Price
Outstanding at January 1, 2016		13,583,862			635,714		14,219,576		$	3.10
Granted		425,000			—		425,000		$	2.22
Exercised, Forfeited or Expired		(623,284	)		—		(623,284	)	$	3.88
Outstanding at June 30, 2016		13,385,578			635,714		14,021,292		$	3.04
Options exercisable at June 30, 2016		8,651,113			635,714		9,286,827		$	3.34

Schedule of share-based compensation, summarizes significant ranges of outstanding stock options

The following table summarizes significant ranges of outstanding stock options under our plans at June 30, 2016:

Range of Exercise Prices		Total Number of Options		Weighted-Average Remaining Contractual Life (years)		Weighted-Average Exercise Price		Total Number of Options Exercisable		Weighted-Average Remaining Contractual Life (years)		Weighted-Average Exercise Price
$	1.83 - $2.00		1,224,500		6.45	$	1.83		1,224,500		6.45	$	1.83
$	2.01 – $2.50		8,395,558		8.70	$	2.32		4,071,021		8.25	$	2.30
$	2.51 – $4.00		1,047,693		7.75	$	2.86		910,194		7.57	$	2.86
$	4.01 – $32.55		3,353,541		6.62	$	5.34		3,081,112		6.54	$	5.38
			14,021,292		7.93	$	3.04		9,286,827		7.38	$	3.31