Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2015

Summary of the Company's Outstanding Common Stock Warrants

The following is a summary of the Company’s outstanding common stock warrants as of June 30, 2015 and December 31, 2014:


				Number of warrants (In thousands)
Warrants Issued in Connection with:	Expiration Date	Exercise Price		June 30, 2015		December 31, 2014
Private Placement Series A	04/16/18	$	3.40		1,460		1,460
Private Placement Series B	04/16/15	$	3.40		—		757
2013 Private Placement	09/23/18	$	2.80		147		147
2014 Public Offering	02/18/19	$	2.75		1,872		1,872
2014 Public Offering	02/18/19	$	2.56		293		293
2014 Private Placement	08/28/19	$	2.90		2,700		2,700
2014 Private Placement	08/28/19	$	3.70		216		216
2015 Private Placement	03/25/20	$	1.71		2,920		—
2015 Private Placement	03/20/20	$	2.13		234		—

Total Warrants Outstanding					9,842		7,445

Summary of the Company's Stock Option Activity under its 2005 and 2015 Plans

The following is a summary of the Company’s stock option activity under its 2005 and 2015 Plans for the six months ended June 30, 2015:


	Options Available for Grant			Options Outstanding			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life		Aggregate Intrinsic Value
	(In thousands)								(Years)		(In thousands)

Balance at December 31, 2014		54			672		$	3.63		8.49

Options granted		(1,423	)		1,423		$	1.44
Options forfeited		190			(190	)	$	1.93
Options expired		(60	)		—		$	2.67
Options authorized		4,000			—		$	—

Balance at June 30, 2015		2,761			1,905		$	2.16		8.78	$	—


Exercisable at June 30, 2015					493		$	3.28		8.10	$	—

Vested and expected to vest at June 30, 2015					1,322		$	2.39		8.51	$	—

Weighted-Average Assumptions

The fair values for the stock options granted in the six-month period ended June 30, 2015 were estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:


Weighted Average Assumptions
	Six months ended June 30,
	2015			2014

Risk-free interest rate		1.69	%		1.56	%
Expected life (years)		6			4
Expected volatility		92	%		101	%
Dividend yield		0.00	%		0.00	%

- 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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