Assets and Liabilities Measured at Fair Value (Tables)

3 Months Ended

Mar. 31, 2013

Assets and Liabilities Measured at Fair Value

Schedule of weighted average assumptions used in the Black-Scholes valuation model for the warrants

	Three Months Ended March 31,
	2012			2013
Expected stock price volatility	72.6		%	98.8		%
Risk free interest rate	0.31		%	0.13		%
Expected life of warrants (years)	1.92			0.92
Expected annual dividend per share	$	0.00		$	0.00

Schedule of financial assets and liabilities subject to fair value measurements

A summary of the fair value of the Company’s assets and liabilities aggregated by the level in the fair value hierarchy within which those measurements fall as of December 31, 2012, are identified in the following table (in thousands):

	Level 1		Level 2		Total
Assets:
Cash/Money market funds	$	33,971	$	—	$	33,971
Corporate debt securities	—		42,497		42,497
Commercial paper	—		19,744		19,744
Certificate of deposit	—		2,910		2,910
	$	33,971	$	65,151	$	99,122

	Level 1		Level 2		Level 3		Total
Liabilities:
Secured debt	$	—	$	697	$	—	$	697
Warrants liability	—		—		908		908
	$	—	$	697	$	908	$	1,605

A summary of the fair value of the Company’s assets and liabilities aggregated by the level in the fair value hierarchy within which those measurements fall as of March 31, 2013, are identified in the following table (in thousands):

	Level 1		Level 2		Total
Assets:
Cash/Money market funds	$	26,736	$	—	$	26,736
Corporate debt securities	—		35,924		35,924
Commercial paper	—		21,741		21,741
Certificate of deposit	—		350		350
	$	26,736	$	58,015	$	84,751

	Level 1		Level 2		Level 3		Total
Liabilities:
Secured debt	$	—	$	597	$	—	$	597
Warrants liability	—		—		1,170		1,170
	$	—	$	597	$	1,170	$	1,767