Stock Based Compensation (Tables)

6 Months Ended

Jun. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [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 Consolidated Statements of Operations:

	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Research and development — employee	$	29,451	$	278,533	$	60,423	$	631,616
General and administrative — employee		264,935		401,820		556,158		869,485
Total employee stock-based compensation	$	294,386	$	680,353	$	616,581	$	1,501,101
Research and development — non-employee	$	—	$	—	$	—	$	—
General and administrative — non-employee		19,517		36,578		40,867		65,237
Total non-employee stock-based compensation	$	19,517	$	36,578	$	40,867	$	65,237

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, 2018			Six Months Ended June 30, 2017
Risk-free interest rate		2.42	%		2.04	%
Expected volatility		91.6	%		85.5	%
Expected lives (years)		6			6
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, 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
Exercised, Forfeited or Expired		(116,170	)		—		(116,170	)	$	10.11
Outstanding at June 30, 2018		2,377,676			373,333		2,751,009		$	10.63
Options exercisable at June 30, 2018		1,833,715			373,333		2,207,048		$	12.44

Schedule of Outstanding Stock Options

The following table summarizes significant ranges of outstanding stock options under our plans at June 30, 2018:

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
$1.75 - $5.00		1,287,364		9.08	$	2.14		797,279		9.06	$	2.19
$5.01 – $11.00		178,334		4.45	$	10.98		178,334		4.45	$	10.98
$11.01 – $15.00		767,958		6.69	$	13.91		714,498		6.64	$	13.86
$15.01 – $98.28		517,353		5.07	$	26.79		516,937		5.07	$	26.80
		2,751,009		7.36	$	10.63		2,207,048		6.97	$	12.44