Stock Based Compensation (Tables)

3 Months Ended

Mar. 31, 2018

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,
	2018		2017
Research and development — employee	$	30,972	$	353,083
General and administrative — employee		428,989		549,782
Total employee stock-based compensation	$	459,961	$	902,865
Research and development — non-employee	$	—	$	—
General and administrative — non-employee		21,350		28,660
Total non-employee stock-based compensation	$	21,350	$	28,660

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, 2018			Three Months Ended March 31, 2017
Risk-free interest rate		2.42	%		—
Expected volatility		91.6	%		—
Expected lives (years)		6			—
Expected dividend yield		0.0	%		—

Schedule of Share-based Compensation, Stock Options, Activity

Presented below is our stock option activity:

	Three Months Ended March 31, 2018
	Number of Options (Employees)			Number of Options (Non-Employees)		Total Number of Options			Weighted-Average Exercise Price
Outstanding at January 1, 2018		2,492,179			373,333		2,865,512		$	10.62
Granted		1,667			—		1,667		$	1.89
Forfeited or expired		(94,424	)		—		(94,424	)	$	3.20
Outstanding at March 31, 2018		2,399,422			373,333		2,772,755		$	10.86
Exercisable at March 31, 2018		1,777,853			373,333		2,151,186		$	12.96

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, 2018:

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
$	1.75 - $5.00		1,287,920		9.33	$	2.14		742,990		9.31	$	2.19
$	5.01 – $11.00		178,335		4.70	$	10.98		178,335		4.70	$	10.98
$	11.01 – $15.00		767,959		6.94	$	13.91		692,283		6.86	$	13.83
$	15.01 – $98.28		538,541		5.19	$	27.36		537,578		5.19	$	27.37
			2,772,755		7.57	$	10.86		2,151,186		7.11	$	12.96