Income Taxes (Tables)

12 Months Ended

Dec. 31, 2012

Income Taxes [Abstract]

Schedule of effective tax rate based on federal statutory rate

The Company’s effective tax rate differs from that based on the federal statutory rate due to the following:

	Years Ended December 31,
	2012			2011
Federal tax at statutory rate		$(14,603	)		(8,571	)
State income taxes		(1,149	)		(1,278	)
State rate changes		2,161			(1,443	)
Federal and state credits		(15,784	)		(1,611	)
Trimeris net operating losses		—			(9,481	)
Expiration of state NOLs		11,129			337
Stock-based compensation		335			(26	)
Valuation allowance		17,887			22,081
Other		24			(8	)
Benefit from income taxes	$	—		$	—

Significant components of net deferred tax asset

Significant components of the Company’s net deferred tax asset as December 31, 2012 and 2011 are as follows:

	2012			2011
Deferred tax assets:
Net operating losses	$	37,451		$	45,825
Capitalized research and development		10,286			10,428
Tax credit carryforwards		25,693			5,267
Deferred revenue		2,056			1,073
Accrued expenses		142			706
Depreciation and amortization		235			109
Stock-based compensation		1,289			6
Other		10			11
		77,162			63,425
Deferred tax liabilities:
Acquired intangibles		(1,527	)		(3,445	)
Valuation allowance		(75,635	)		(59,980	)
Net deferred tax asset	$	—		$	—

Schedule of earliest tax years that remain subject to examination by jurisdictions

Below is a table of the earliest tax years that remain subject to examination by jurisdictions:

	Earliest Tax Year Subject to Examination
Jurisdiction
U.S Federal		2009
State of Georgia		2009
State of North Carolina		2009
Commonwealth of Massachusetts		2009