Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

Income Taxes

Schedule of deferred tax assets and liabilities

Components of the net deferred tax (liability) asset at December 31, 2015 and 2014 are as follows, in thousands:

	2015			2014
Deferred tax assets:
Federal and state net operating losses	$	115,583		$	80,549
Research credits		23,353			18,773
Deferred compensation		10,031			14,391
Deferred revenue		8,635			12,176
Accrued expenses		3,023			2,851
Intangibles		3,300			3,441
Depreciation		686			838
Unrealized loss on marketable securities		1			6
Total deferred tax assets		164,612			133,025
Valuation allowance		(164,612	)		(133,025	)
Net deferred tax assets	$	—		$	—

Schedule of reconciliation of federal statutory income tax provision to actual provision

        A reconciliation of the federal statutory income tax benefit to the Company's actual provision for the years ended December 31, 2015, 2014 and 2013 is as follows (in thousands):

	2015			2014			2013
Benefit at federal statutory tax rate	$	(28,323	)	$	(33,521	)	$	(36,856	)
State taxes, net of federal benefit		(4,398	)		(5,206	)		(5,724	)
Share-based compensation		3,634			2,411			2,106
Tax credits		(2,652	)		(5,529	)		(2,404	)
Other		42			23			15
Change in valuation allowance		31,697			41,822			42,863
Income tax provision	$	—		$	—		$	—

Schedule of reconciliation of unrecognized tax benefits

        A reconciliation of the beginning and ending amount of unrecognized tax benefits for the years ended December 31, 2015 and 2014 is as follows (in thousands):

	2015			2014
Balance, beginning of year	$	4,064		$	4,465
Additions for tax positions related to the current year		1,395			940
Reductions of tax positions of prior years		(343	)		(1,341	)
Balance, end of year	$	5,116		$	4,064