Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

A summary of warrant activity during the year ended December 31, 2017 is as follows (share amounts in thousands):



	Common Shares Issuable upon Exercise		Weighted Average Exercise Price
Outstanding at December 31, 2016	2,318		$	15.19
Issued	5,199		$	1.60
Exercised	(186	)	$	1.55
Cancelled	(247	)	52.50
Outstanding as of December 31, 2017	7,084		$	3.91
Exercisable as of December 31, 2017	7,084		$	3.91

The following table shows the number of outstanding warrants by exercise price and date of expiration as of December 31, 2017 (share amounts in thousands):



Shares Issuable Upon Exercise	Exercise Price		Expiration Date
300	$	34.00	May 2018
1,068	$	1.67	March 2020
107	$	2.16	March 2020
252	$	1.75	April 2022
4,452	$	1.55	May 2022
429	$	8.80	January 2023
442	$	8.80	March 2023
19	$	12.90	October 2024
15	$	16.40	July 2025
7,084

- 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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