We are subject to taxation in the U.S. and in various state, local, and foreign jurisdictions. We remain subject to examination by U.S. Federal, state, local, and foreign tax authorities for tax years 2016 through 2019. With a few exceptions, we are no longer subject to U.S. Federal, state, local, and foreign examinations by tax authorities for the tax year 2015 and prior. However, net operating losses from the tax year 2015 and prior would be subject to examination if and when used in a future tax return to offset taxable income. Our policy is to recognize income tax related penalties and interest, if any, in our provision for income taxes and, to the extent applicable, in the corresponding income tax assets and liabilities, including any amounts for uncertain tax positions.

As of December 31, 2019, we had available net operating loss carryforwards of $646.3 million and $184.9 million for Federal and state income tax purposes, respectively, which are available to offset future Federal and state taxable income, if any, $38.6 million of these Federal net operating loss carryforwards do not expire, while the remaining net operating loss carryforwards expire between 2021 and 2038. Our ability to use these net operating losses is limited by change of control provisions under Internal Revenue Code Section 382 and may expire unused. In addition, we have $8.8 million and $9.4 million of Federal and state research and development credits, respectively, available to offset future taxable income. These Federal and state research and development credits expire between 2020 and 2033 and 2020 and 2029, respectively. Additionally, we have $214,000 of state investment tax credits, available to offset future taxable income and expire between 2020 and 2022. We also have foreign income tax net operating loss carryforwards of approximately $1.9 million generated in Switzerland which are available to offset future foreign taxable income, if any, and expire between 2024 and 2026. We also have foreign net operating loss carryforwards, which do not expire, available to offset future foreign taxable income of $7.5 million in the United Kingdom, $8.0 million in Belgium, $55,000 in Ireland, and $289,000 in Hong Kong. The potential impacts of such provisions are among the items considered and reflected in management’s assessment of our valuation allowance requirements.

The tax effect of temporary differences and net operating loss and tax credit carryforwards that give rise to significant portions of the deferred tax assets and deferred tax liabilities as of December 31, 2019 and 2018 are presented below (in thousands).

	2019			2018
Deferred tax assets:
U.S. Federal and State net operating loss carryforwards	$	143,126		$	182,557
Foreign net operating loss carryforwards		4,096			1,524
Research and development tax credits		16,364			18,507
Share-based compensation		4,774			4,824
Intangible Assets		38,710			36,217
Interest expense carryforward		3,893			6,555
Deferred Revenue		47,456			—
Lease Liability		2,002			—
Other		3,974			4,882
Total deferred tax assets		264,395			255,066
Less: valuation allowance		(262,228	)		(254,315	)
Net deferred tax assets		2,167			751
Foreign intangible assets		(1,009	)		(1,063	)
Right of use asset		(1,599	)		—
Other		(165	)		(406	)
Deferred tax liabilities		(2,773	)		(1,469	)
Net deferred tax liability	$	(606	)	$	(718	)

In assessing the realizability of deferred tax assets, we consider whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which the net operating loss and tax credit carryforwards can be utilized or the temporary differences become deductible. We consider projected future taxable income and tax planning strategies in making this assessment. In order to fully realize the deferred tax asset, we will need to generate future taxable income sufficient to utilize net operating losses prior to their expiration. Based upon our history of not generating taxable income due to our business activities focused on product development, we believe that it is more likely than not that deferred tax assets will not be realized through future earnings. Accordingly, a valuation allowance has been established for deferred tax assets which will not be offset by the reversal of deferred tax liabilities. The valuation allowance on the deferred tax assets increased by $7.9 million during the year ended December 31, 2019, while the valuation allowance decreased by $21.9 during the year ended December 31, 2018, respectively.

Income tax benefit was nil for the years ended December 31, 2019, 2018 and 2017. Income taxes recorded differed from the amounts computed by applying the U.S. Federal income tax rate of 21% in 2019 and 2018 and 34% in 2017 to loss before income taxes as a result of the following (in thousands).

	2019			2018			2017
Computed “expected” Federal tax benefit	$	(23,413	)	$	(34,029	)	$	(41,035	)
(Increase) reduction in income taxes benefit resulting from:
Change in valuation allowance		7,913			24,233			(63,868	)
(Decrease) increase due to uncertain tax positions		(64	)		7			—
Foreign income inclusion		—			11,089			—
State and local income benefit, net of Federal income tax benefit		4,144			(11,708	)		(4,561	)
Change in federal tax rate		—			—			104,764
Foreign rate differential		(564	)		956			2,084
Change in fair value contingent consideration		1,219			(280	)		(1,084	)
Other, net		10,765			9,732			3,700
Income tax benefit	$	—		$	—		$	—

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

	2019			2018		2017
Balance, January 1	$	4,356		$	4,349	$	5,278
Increase related to current year positions		122			—		—
Increase (decrease) related to previously recognized positions		(186	)		7		—
Decrease related to change in federal tax rate		—			—		(929	)
Balance, December 31	$	4,292		$	4,356	$	4,349

These unrecognized tax benefits would all impact the effective tax rate if recognized. There are no positions which we anticipate could change within the next twelve months.