Exhibit 12.1

Statement re Computation of Ratio of Earnings to Fixed Charges

	Year Ended December 31,															Six Months Ended June 30, 2012
	2007			2008			2009			2010			2011
	(in thousands)
Earnings:
Net loss	$	(28,575	)	$	(37,874	)	$	(31,929	)	$	(17,347	)	$	(25,997	)	$	(10,587	)
Add: Fixed charges		1,671			2,713			4,154			1,288			753			388
Total earnings (loss)	$	(26,904	)	$	(35,161	)	$	(27,775	)	$	(16,059	)	$	(25,244	)	$	(10,199	)
Fixed Charges:
Interest expense	$	911		$	2,030		$	2,613		$	870		$	488		$	273
Amortization of commitment fees, debt issuance costs and original issue discount		738			654			1,491			388			235			100
Estimated interest component of rent expense		22			29			50			30			30			15
Total fixed charges	$	1,671		$	2,713		$	4,154		$	1,288		$	753		$	388
Ratio of earnings to fixed charges		—			—			—			—			—			—
Deficiency of earnings available to cover fixed charges	$	(28,575	)	$	(37,874	)	$	(31,929	)	$	(17,347	)	$	(25,997	)	$	(10,587	)