Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2015

Components of Derivative Instruments

Derivative instruments consist of the following:

	December 31,
	2015		2014
	(in thousands)
Convertible Notes	$	30,823	$	21,501
Reimbursement Notes		1,118		705
Bridge Notes		3,130		1,926
Amended and Restated August 2009 Warrants		2,142		930
Amended and Restated June 2010 MHR Warrants		552		282
Amended and Restated August 2010 Warrants		1,507		654
August 2010 Investor Warrants*		—		29
Amended and Restated August 2010 MHR Waiver Warrants		560		243
Amended and Restated July 2011 Warrants		1,729		750
July 2011 Investor Warrants		205		210
Amended and Restated July 2011 MHR Waiver Warrants		456		198
May 2013 MHR Modification Warrants		5,744		2,492
	$	47,966	$	29,920

* These warrants expired August 2015.

Convertible Notes [Member]

Summary of Assumptions Used in Computing Fair Value

The assumptions used in computing the fair values as of December 31, 2015 and 2014, are as follows:

	December 31, 2015			December 31, 2014
Closing stock price	$	0.68		$	0.28
Conversion price	$	1.25		$	1.25
Expected volatility		143	%		140	%
Remaining term (years)		6.25			7.25
Risk-free rate		1.95	%		1.97	%
Expected dividend yield		0	%		0	%

Reimbursement Notes [Member]

Summary of Assumptions Used in Computing Fair Value

The assumptions used in computing the fair value as of December 31, 2015 and 2014 are as follows:

	December 31, 2015			December 31, 2014
Closing stock price	$	0.68		$	0.28
Conversion price	$	0.50		$	0.50
Expected volatility		143	%		140	%
Remaining term (years)		6.25			7.25
Risk-free rate		1.95	%		1.97	%
Expected dividend yield		0	%		0	%

Bridge Notes [Member]

Summary of Assumptions Used in Computing Fair Value

The assumptions used in computing the fair value as of December 31, 2015 and 2014 are as follows:

	December 31, 2015			December 31, 2014
Closing stock price	$	0.68		$	0.28
Conversion price	$	0.50		$	0.50
Expected volatility		143	%		140	%
Remaining term (years)		6.25			7.25
Risk-free rate		1.95	%		1.97	%
Expected dividend yield		0	%		0	%

Amended and Restated June 2010 Warrants [Member]

Summary of Assumptions Used in Computing Fair Value

The assumptions used in computing the fair value of the Amended and Restated June 2010 Warrants as of December 31, 2015 and 2014, are as follows:

	December 31, 2015			December 31, 2014
Closing stock price	$	0.68		$	0.28
Conversion price	$	0.50		$	0.50
Expected volatility		136	%		160	%
Remaining term (years)		3.52			4.52
Risk-free rate		1.42	%		1.51	%
Expected dividend yield		0	%		0	%

Warrants [Member]

Summary of Assumptions Used in Computing Fair Value

The assumptions used in computing the fair value the Original Warrants as of December 31, 2015 and 2014, are as follows:

	December 31, 2015			December 31, 2014
Closing stock price	$	0.68		$	0.28
Conversion price	$	0.50		$	0.50
Expected volatility		141	%		161	%
Remaining term (years)		3.52			4.52
Risk-free rate		1.31	%		1.65	%
Expected dividend yield		0	%		0	%

August 2010 Investor Warrants [Member]

Summary of Assumptions Used in Computing Fair Value

The assumptions used in computing the fair value of the remaining August 2010 Warrants as of December 31, 2014, are as follows:

	December 31, 2014
Closing stock price	$	0.28
Conversion price	$	1.26
Expected volatility		116	%
Remaining term (years)		0.65
Risk-free rate		0.12	%
Expected dividend yield		0	%

July 2011 Investor Warrants [Member]

Summary of Assumptions Used in Computing Fair Value

The assumptions used in computing the fair value of the July 2011 Warrants as of December 31, 2015 and 2014, are as follows:

	December 31, 2015			December 31, 2014
Closing stock price	$	0.68		$	0.28
Conversion price	$	1.09		$	1.09
Expected volatility		88	%		122	%
Remaining term (years)		0.51			1.51
Risk-free rate		0.49	%		0.67	%
Expected dividend yield		0	%		0	%

2013 Restructuring Warrants [Member]

Summary of Assumptions Used in Computing Fair Value

The assumptions used in computing the fair value of the 2013 Restructuring Warrants as of December 31, 2015 and 2014, are as follows:

	December 31, 2015			December 31, 2014
Closing stock price	$	0.68		$	0.28
Conversion price	$	0.50		$	0.50
Expected volatility		141	%		161	%
Remaining term (years)		3.52			4.52
Risk-free rate		1.31	%		1.65	%
Expected dividend yield		0	%		0	%