Warrants (Tables)

3 Months Ended

Mar. 31, 2016

Outstanding Warrants to Purchase Common Stock

The following table summarizes outstanding liability-classified warrants to purchase common stock:



	Number of Warrants
Liability-classified warrants	March 31, 2016	December 31, 2015	Exercise Price		Expiration Dates
Issued in Series B and D Preferred Stock offerings	1,970,594	1,970,594	$	6.25	Jul 2016 - Dec 2016
Issued in March 2010 financing	—	319,789	$	6.25	Mar 2016
Issued in June 2011 financing	6,113	6,113	$	22.50	Jun 2016
Issued in August 2011 financing	565,759	565,759	$	18.75	Aug 2016
Issued to placement agents in August 2011 financing	50,123	50,123	$	13.635	Aug 2016
Issued in Series E Preferred Stock offering	60,000	60,000	$	2.50	Dec 2017
Issued with Convertible Notes	1,125,578	1,125,578	$	2.50	Jun 2018
Issued in Series E Preferred Stock offering	1,568,823	1,568,823	$	7.50	Dec 2018
Total	5,346,990	5,666,779

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, 2016:



	Number of warrants		Weighted- average exercise price
Outstanding at December 31, 2015	5,666,779		$	7.14
Granted	—		—
Exercised	—		—
Expired	(319,789	)	6.25
Outstanding at March 31, 2016	5,346,990		$	7.20

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, 2016			December 31, 2015
Calculated aggregate value	$	3,018		$	8,275
Weighted average exercise price per share	$	7.20		$	7.14
Closing price per share of common stock	$	2.50		$	4.55
Volatility	93.3		%	85.2		%
Weighted average remaining expected life	1 year, 6 months			1 year, 8 months
Risk-free interest rate	0.66		%	0.98		%
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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