Income Taxes (Tables)

12 Months Ended

Dec. 31, 2014

Components of the Company's Deferred Income Tax Assets (Liabilities)

The significant components of the Company’s deferred income tax assets (liabilities) were as follows (in thousands):


	December 31,
	2014			2013
Deferred income tax assets:
Federal U.S. net operating loss carryforward	$	55,358		$	36,561
State net operating loss carryforward		3,723			3,316
Research and development credit, net		7,177			3,786
Orphan drug credit, net		19,287			19,883
Deferred rent		4,069			5,132
Deferred revenue		3,989			8,217
Depreciation		1,337			1,438
Other		962			1,439

Gross deferred income tax assets		95,902			79,772
Valuation allowance		(94,297	)		(79,377	)

Net deferred income tax assets		1,605			395
Deferred income tax liabilities:
Prepaid expenditures		(1,605	)		(395	)

Gross deferred income tax liabilities		(1,605	)		(395	)
Net deferred income tax asset/(liability)	$	—		$	—

Reconciliation of Reported Estimated Income Tax Benefit

The reconciliation of the reported estimated income tax benefit to the amount that would result by applying the U.S. federal statutory tax rate to the net income is as follows (in thousands):


	Year Ended December 31,
	2014			2013			2012
United States federal tax at statutory rate	$	(13,410	)	$	(91	)	$	2,927
State taxes (net of federal benefit)		(1,608	)		609			1,460
Deferred income tax adjustments		—			(855	)		(512	)
Deferred state blended rate adjustments		3,034			(344	)		—
Research credit, net		(2,228	)		(226	)		—
Transaction cost deduction		(379	)		—			—
Transaction cost deduction—prior year adjustment		(564	)		—			—
Orphan drug credit, net		(139	)		(843	)		(4,896	)
Other permanent items		(382	)		3			8
Equity-based compensation		756			241			279
Fair value adjustment of preferred stock warrant liability		—			219			(53	)
Change in valuation allowance		14,920			1,287			787

Income tax expense/(benefit)	$	—		$	—		$	—

Reconciliation of the Beginning and Ending Amount of Gross Unrecognized Tax Benefits

A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows (in thousands):


	Year Ended December 31,
	2014		2013		2012
Beginning balance	$	1,708	$	1,592	$	1,534
Increases/(decreases) for current year tax positions		242		116		58
Increases/(decreases) for prior year tax positions		97		—		—
Decreases as a result of expiration of statute of limitations		—		—		—

Ending balance	$	2,047	$	1,708	$	1,592