Income Taxes (Tables)

9 Months Ended

Sep. 30, 2012

Income Taxes

Schedule of components of the benefit from income tax

	Year Ended December 31,
	2009		2010			2011
	(in thousands)
Current
Federal	$	—	$	—		$	(14,090	)
State		—		—			(2,155	)
Deferred
Federal		—		(399	)		—
State		—		—			—
Total	$	—	$	(399	)	$	(16,245	)

Schedule of reconciliation of the expected income tax benefit computed using the federal statutory income tax rate to the entity's effective income tax rate

	Year Ended December 31,
	2009			2010			2011
	(in thousands)
Income tax (benefit) computed at federal statutory tax rate	$	157		$	(13,421	)	$	(13,419	)
Permanent items		38			61			57
State taxes		33			(2,142	)		(2,155	)
Change in valuation allowance		(667	)		16,144			—
Uncertain tax position		—			190			129
Research and development credits		(986	)		(1,267	)		(857	)
Other		1,425			36			—
Total	$	—		$	(399	)	$	(16,245	)

Schedule of Significant components of the entity's deferred tax assets (liabilities)

	As of December 31,
	2010			2011
	(in thousands)
Deferred tax assets:
Net operating loss carryforward	$	36,418		$	14,809
Deferred rent credit		339			514
Accrued compensation and non-qualified stock options		57			48
Deferred financing costs		(8	)		35
Depreciation and amortization		(15	)		98
Research and development credits		4,282			5,018
Other		8			9
Net deferred tax asset before valuation allowance		41,081			20,531
Valuation allowance		(41,081	)		(20,531	)
Net deferred tax asset	$	—		$	—

Schedule of reconciliation of the beginning and ending amount of gross unrecognized tax benefits

	Year Ended December 31,
	2009		2010		2011
	(in thousands)
Balance as of January 1	$	—	$	—	$	642
Gross increases related to prior-year tax positions		—		452		—
Gross increases related to current-year tax positions		—		190		110
Balance as of December 31	$	—	$	642	$	752