Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Schedule of deferred tax assets and liabilities

Components of the net deferred tax (liability) asset at December 31, 2016 and 2015 are as follows, in thousands:



	2016			2015
Deferred tax assets:
Federal and state net operating losses	$	94,793		$	115,606
Research credits	30,007			23,088
Deferred compensation	9,701			10,031
Deferred revenue	28,096			8,635
Accrued expenses	5,053			3,023
Intangibles	3,220			3,300
Depreciation	475			686
Unrealized loss on marketable securities	—			1
Total deferred tax assets	171,345			164,370
Deferred tax liabilities:
Unrealized gain on marketable securities	(30		)	—
Total deferred tax liabilities	(30		)	—
Valuation allowance	(171,315		)	(164,370		)
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, 2016, 2015 and 2014 is as follows (in thousands):



	2016			2015			2014
Benefit at federal statutory tax rate	$	(7,137	)	$	(28,323	)	$	(33,521	)
State taxes, net of federal benefit	(1,108		)	(4,398		)	(5,206		)
Share-based compensation	5,148			3,634			2,411
Tax credits	(4,120		)	(2,652		)	(5,529		)
Other	272			42			23
Change in valuation allowance	6,945			31,697			41,822
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, 2016 and 2015 is as follows (in thousands):



	2016			2015			2014
Balance, beginning of year	$	5,116		$	4,064		$	4,465
Additions for tax positions related to the current year	1,602			1,395			940
Reductions of tax positions of prior years	(40		)	(343		)	(1,341		)
Balance, end of year	$	6,678		$	5,116		$	4,064