Warrants (Tables)

3 Months Ended

Mar. 31, 2018

Outstanding Warrants to Purchase Common Stock

The following table summarizes outstanding warrants to purchase the Company’s common stock:



	Number of warrants
	March 31, 2018	December 31, 2017	Exercise Price		Expiration Dates
Liability-classified Warrants
Issued with June 2012 Convertible Notes	375,194	375,194	$	7.50	Jun 2018
Issued in Series E Preferred Stock offering	523,045	523,045	$	22.50	Dec 2018
Issued with September 2016 Convertible Notes	6,029,174	6,029,174	$	4.50	Sep 2021
Total liability-classified warrants	6,927,413	6,927,413

Equity-classified Warrants
Issued in 2017 Series A Preferred Stock Offering	3,437,334	3,437,334	$	2.54	Mar 2022
Issued in December 2017 Common Stock Offering - common warrants	14,046,950	14,046,950	$	0.77	Dec 2022
Issued in December 2017 Common Stock Offering - underwriter warrants	436,364	436,364	$	0.9625	Dec 2022
Issued in December 2017 Common Stock Offering - pre-funded warrants	—	2,416,104	$	0.01	No exp
Total equity-classified warrants	17,920,648	20,336,752


Total outstanding warrants	24,848,061	27,264,165

Schedule of Warrants Outstanding Roll Forward

The table below is a summary of the Company’s warrant activity during the three months ended March 31, 2018:



	Number of warrants					Weighted- average exercise price
	Liability-classified	Equity-classified		Total		Weighted- average exercise price
Outstanding at December 31, 2017	6,927,413	20,336,752		27,264,165		$	2.26
Granted	—	—		—		—
Exercised	—	(2,416,104	)	(2,416,104	)	0.01
Expired	—	—		—		—
Outstanding at March 31, 2018	6,927,413	17,920,648		24,848,061		$	2.48

Summary of Other Assumptions Used by Entity

The following table summarizes the calculated aggregate fair values, along with the inputs and assumptions utilized in each calculation:




($ in thousands except per share data)	March 31, 2018			December 31, 2017
Calculated aggregate value	$	838		$	1,073
Weighted average exercise price per share	$	6.02		$	6.02
Closing price per share of common stock	$	0.59		$	0.64
Volatility	93.0		%	92.2		%
Weighted average remaining expected life	3 years, 1 month			3 years, 4 months
Risk-free interest rate	2.34		%	2.00		%
Dividend yield	—			—

- Definition

Tabular disclosure of warrants or rights issued. Warrants and rights outstanding are derivative securities that give the holder the right to purchase securities (usually equity) from the issuer at a specific price within a certain time frame. Warrants are often included in a new debt issue to entice investors by a higher return potential. The main difference between warrants and call options is that warrants are issued and guaranteed by the company, whereas options are exchange instruments and are not issued by the company. Also, the lifetime of a warrant is often measured in years, while the lifetime of a typical option is measured in months. Disclose the title of issue of securities called for by warrants and rights outstanding, the aggregate amount of securities called for by warrants and rights outstanding, the date from which the warrants or rights are exercisable, and the price at which the warrant or right is exercisable.

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