Stock Based Compensation (Tables)

6 Months Ended

Jun. 30, 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 and warrants included in our Condensed Statements of Operations:

	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
Research and development — employee	$	278,533	$	507,195	$	631,616	$	988,006
General and administrative — employee		401,820		2,499,368		869,485		3,156,418
Total employee stock-based compensation	$	680,353	$	3,006,563	$	1,501,101	$	4,144,424
Research and development — non-employee	$	—	$	—	$	—	$	—
General and administrative — non-employee		36,578		32,506		65,237		220,462
Total non-employee stock-based compensation	$	36,578	$	32,506	$	65,237	$	220,462

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, 2017			Six Months Ended June 30, 2016
Risk-free interest rate		2.04	%		1.47	%
Expected volatility		85.5	%		76.3	%
Expected lives (years)		6			5 - 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, 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		10,000			—		10,000		$	0.41
Exercised, Forfeited or Expired		(646,847	)		—		(646,847	)	$	3.16
Outstanding at June 30, 2017		16,242,923			600,000		16,842,932		$	2.34
Options exercisable at June 30, 2017		11,655,168			600,000		12,255,168		$	2.75

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, 2017:

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
$	0.41 - $1.50		4,317,533		9.45	$	0.44		1,586,461		9.46	$	0.44
$	1.51 – $2.50		8,669,296		7.32	$	2.26		6,835,946		7.07	$	2.22
$	2.51 – $4.00		960,670		6.64	$	2.88		937,337		6.61	$	2.87
$	4.01 – $32.55		2,895,424		5.69	$	5.24		2,895,424		5.69	$	5.24
			16,842,923		7.55	$	2.34		12,255,168		7.02	$	2.75