Stock Based Compensation (Tables)

3 Months Ended

Mar. 31, 2017

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, restricted stock and warrants included in our unaudited interim statements of operations:

	Three Months Ended March 31,
	2017		2016
Research and development — employee	$	353,083	$	480,811
General and administrative — employee		549,782		657,050
Total employee stock-based compensation	$	902,865	$	1,137,861
Research and development — non-employee	$	—	$	—
General and administrative — non-employee		28,660		187,956
Total non-employee stock-based compensation	$	28,660	$	187,956

Schedule of Share-based Payment Award, Fair Value of the Stock Options Granted, Assumptions

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

	Three Months Ended March 31, 2017		Three Months Ended March 31, 2016
Risk-free interest rate		—		1.47	%
Expected volatility		—		76.3	%
Expected lives (years)		—		5 - 10
Expected dividend yield		—		0.00	%

Schedule of Share-based Compensation, Stock Options, Activity

Presented below is our stock option activity:

	Three Months Ended March 31, 2017
	Number of Options (Employees)			Number of Options (Non-Employees)		Total Number of Options			Weighted-Average Exercise Price
Outstanding at January 1, 2017		16,879,770			600,000		17,479,770		$	2.37
Granted		—			—		—		$	—
Exercised, forfeited or expired		(360,000	)		—		(360,000	)	$	3.24
Outstanding at March 31, 2017		16,519,770			600,000		17,119,770		$	2.35
Exercisable at March 31, 2017		11,108,079			600,000		11,708,079		$	2.85

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 March 31, 2017:

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
$	0.43 - $1.50		4,432,500		9.70	$	0.44		1,330,704		9.71	$	0.44
$	1.51 – $2.50		8,752,604		7.58	$	2.26		6,469,375		7.26	$	2.22
$	2.51 – $4.00		960,670		6.88	$	2.88		934,004		6.86	$	2.87
$	4.01 – $32.55		2,973,996		5.78	$	5.32		2,973,996		5.78	$	5.32
			17,119,770		7.78	$	2.35		11,708,079		7.13	$	2.85