6. Income Taxes

For the years ended December 31, 2014, 2013 and 2012 there was no current provision for federal or state income taxes due to the taxable losses which resulted or use of legacy NOL carryforwards.

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)	$	—		$	—

The Company recognizes valuation allowances to reduce deferred tax assets to the amount that is more likely than not to be realized. In assessing the likelihood of realization, management considers (i) future reversals of existing taxable temporary differences; (ii) future taxable income exclusive of reversing temporary difference and carryforwards; (iii) taxable income in prior carryback years if carryback is permitted under applicable tax law; and (iv) tax planning strategies. The Company’s net deferred income tax asset is not more likely than not to be utilized due to the lack of sufficient sources of future taxable income and cumulative book losses which have resulted over the years. The net increase in the valuation allowance in 2014 is due to the fact the Company generated research and development and orphan drug credits and NOL carryforwards which increased the net deferred tax asset. The increase in the credits and NOL carryforwards were offset by the decrease in deferred revenue and resulted in a net current year increase to the valuation allowance.

As of December 31, 2014, the Company had U.S. federal NOL carryforwards of approximately $158.9 million and approximately $103.4 million for state that will expire in various years beginning in 2020 through 2034. In addition, the Company has U.S. federal tax credits of $26.3 million which will expire in various years beginning in 2020 through 2034.

The use of the Company’s U.S. federal NOL and tax credit carryforwards in future years are restricted due to changes in the Company’s ownership and tax attributes acquired through the Company’s acquisitions. As of December 31, 2014, $7.1 million of the Company’s US Federal NOLs are limited for use over the years 2015-2027 in which a range of such amounts could be utilized on an annual basis of $0.2 million to $1.4 million. The remaining $151.8 million of NOLs is not limited and can be offset against future taxable income. Additionally, approximately $7.7 million of NOLs will be recognized as a benefit through additional-paid-in-capital when realized. Further, despite the NOL and credit carryforwards, the Company may have a future tax liability due to an alternative minimum tax or state tax requirements in which net operating losses do not exist.

Furthermore, the Company recorded $1.6 million of current deferred tax liability and $1.6 million of noncurrent deferred tax asset as a result of the requirement to allocate its valuation allowance against gross deferred tax assets. As such the balance sheet was grossed up but nets to zero deferred income tax assets/(liabilities).

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)	$	—		$	—		$	—

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

As of December 31, 2014 and 2013, of the total gross unrecognized tax benefits, approximately $1.7 million and $1.3 million would favorably impact the Company’s effective income tax rate, respectively. Although, due to the Company’s determination that the deferred income tax asset would not more likely than not be realized, a valuation allowance would be recorded, therefore, zero net impact would result within the Company’s effective income tax rate. The Company’s uncertain income tax position liability has been recorded to deferred income taxes to offset the tax attribute carryforward amounts.

For the years ended December 31, 2014, 2013 and 2012, the Company has not recognized any interest or penalties related to the uncertain income tax positions due to the fact such position is related to tax attribute carryforwards which have not yet been utilized. The Company does not expect its unrecognized income tax position to significantly decrease within the next twelve months.

The Company’s U.S. Federal and state income tax returns from 2001 to 2014 remain subject to examination by the tax authorities. The Company’s 2001 through 2010 years remain open for examination, even though the statute of limitations has expired, due to the net operating losses and credits carried forward for use in prospective years.