Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2015

Assets and Liabilities Measured at Fair Value

The following table provides a summary of the recognized assets and liabilities that we measure at fair value on a recurring basis:

	Balance as of		Basis of Fair Value Measurements
	June 30, 2015		Level 1		Level 2		Level 3
Assets:
Cash equivalents	$	5,644,000	$	5,644,000	$	—	$	—
Liabilities:
Warrant liability	$	18,187,000	$	—	$	—	$	18,187,000

	Balance as of		Basis of Fair Value Measurements
	December 31, 2014		Level 1		Level 2		Level 3
Assets:
Cash equivalents	$	8,144,000	$	8,144,000	$	—	$	—
Liabilities:
Warrant liability	$	9,793,000	$	—	$	—	$	9,793,000

Estimation of Fair Value Determined by Using Option Pricing Model

All future changes in the fair value of the warrants will be recognized in our consolidated statements of operations until they are either exercised or expire in 2020. The warrants are not traded in an active securities market, and as such the estimated the fair value as of June 30, 2015 and December 31, 2014 was determined by using an option pricing model (Monte Carlo) with the following assumptions:

	As of June 30, 2015			As of December 31, 2014
October 2014 Warrants
Expected term	4.8 years			5.3 years
Common stock market price	$	0.56		$	0.49
Risk-free interest rate		1.63	%		1.65	%
Expected volatility		90-120	%		90.00	%
Resulting fair value (per warrant)	$	0.43		$	0.38

	As of June 30, 2015			As of December 31, 2014
May 2015 Warrants
Expected term	5.4 years				—
Common stock market price	$	0.56			—
Risk-free interest rate		1.63	%		—
Expected volatility		90-120	%		—
Resulting fair value (per warrant)	$	0.42			—

Summary of Change in Level 3 Warrant Liability

The following table summarizes the change in our Level 3 warrant liability value:

Warrant liability	Six months ended June 30, 2015

Beginning balance	$	9,793,000
Issuance of warrants		14,329,000
Exercised warrants		(8,257,000	)
Change in fair value		2,322,000
Ending balance	$	18,187,000