Stock Based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

Share-based Payment Arrangement [Abstract]

Schedule of Total Stock-based Compensation Expense from Stock Options, Restricted Stock 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,
	2019		2018
Research and development — employee	$	—	$	—
General and administrative — employee		213,174		428,989
Total employee stock-based compensation	$	213,174	$	428,989
Research and development — non-employee	$	—	$	—
General and administrative — non-employee		—		21,350
Total non-employee stock-based compensation	$		$	21,350

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, 2019		Three Months Ended March 31, 2018
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, 2019
	Number of Options (Employees)			Number of Options (Non-Employees)		Total Number of Options			Weighted-Average Exercise Price
Outstanding at January 1, 2019		2,190,835			365,000		2,555,835		$	10.69
Granted		—			—		—			—
Forfeited or expired		(146,950	)		—		(146,950	)	$	10.03
Outstanding at March 31, 2019		2,043,885			365,000		2,408,885		$	10.73
Exercisable at March 31, 2019		1,803,304			365,000		2,168,304		$	11.69

Schedule of Outstanding Stock Options

The following table summarizes significant ranges of outstanding stock options under our plans at March 31, 2019:

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		1,138,099		8.34	$	2.13		897,518		8.32	$	2.17
$5.01 – $11.00		165,834		3.70	$	10.98		165,834		3.70	$	10.98
$11.01 – $15.00		634,025		6.05	$	13.91		634,025		6.05	$	13.91
$15.01 – $98.28		470,927		4.44	$	27.12		470,927		4.44	$	27.12
		2,408,885		6.65	$	10.73		2,168,304		6.46	$	11.69