	Year Ended December 31,			Six Months Ended December 31,			Year Ended June 30,
	2019			2018			2018			2017
U.S. operations	$	(56,866	)	$	(44,804	)	$	(53,000	)	$	(17,566	)
Non-U.S. operations		73			84			(171	)		(919	)
Loss before income taxes	$	(56,793	)	$	(44,720	)	$	(53,171	)	$	(18,485	)

On December 22, 2017, the Tax Cuts and Jobs Act (the “Tax Act”) was signed into law, making significant changes to the federal tax law. Amongst other things, the Tax Act reduces the federal corporate tax rate from 34% to 21% effective for tax years beginning after December 31, 2017 and has resulted in a remeasurement of the Company’s deferred tax assets included in the Company’s fiscal 2018 rate reconciliation. The difference between the Company’s expected income tax benefit, as computed by applying the blended statutory U.S. federal tax rate of 21% for the year ended December 31, 2019, 21% for the six months ended December 31, 2018, 27.5% for fiscal 2018 and 34% for fiscal 2017 to loss before income taxes, and actual income tax benefit is reconciled in the following table (in thousands):

	Year Ended December 31,			Six Months Ended December 31,			Year Ended June 30,
	2019			2018			2018			2017
Income tax benefit at statutory rate	$	(11,927	)	$	(9,391	)	$	(14,622	)	$	(6,284	)
State income taxes, net of federal benefit		(3,685	)		(1,657	)		(1,552	)		(928	)
Non-U.S. income tax rate differential		374			186			(66	)		(121	)
Change in fair value of derivative		—			3,900			7,227			—
Change in federal tax rate		—			—			14,673			—
Research and development tax credits		(150	)		(231	)		(284	)		(242	)
Permanent items		55			—			(15	)		(9	)
Changes in valuation allowance		15,608			7,166			(5,385	)		7,489
Other, net		(275	)		27			24			95
Income tax benefit	$	—		$	—		$	—		$	—

For the year ended June 30, 2018, in addition to the $5.4 million change in valuation allowance in the above table, the Company recorded a deferred tax asset of $6.2 million and a valuation allowance of the same amount in connection with the Icon acquisition.

The significant components of deferred income taxes are as follows (in thousands):

	December 31,		December 31,
	2019		2018
Deferred tax assets:
Net operating loss carryforwards	$	66,400	$	53,259
Deferred revenue		8		70
Lease liability		923		0
Stock-based compensation		5,805		4,788
Tax credits		3,687		3,696
Other		1,473		682
Total deferred tax assets		78,296		62,495
Deferred tax liabilities:
Intangible assets		7,559		8,207
Right-of-use assets		841		—
Total deferred tax liabilities		8,400		8,207
Deferred tax assets, net		69,896		54,288
Valuation allowance		69,896		54,288
Total deferred tax liability	$	—	$	—

The valuation allowance generally reflects limitations on the Company’s ability to use the tax attributes and reduces the value of such attributes to the more-likely-than-not realizable amount. Management assessed the available positive and negative evidence to estimate if sufficient taxable income will be generated to use the existing net deferred tax assets. Based on a weighting of the objectively verifiable negative evidence in the form of cumulative operating losses over the three-year period ended June 30, 2018, management believes that it is not more likely than not that the deferred tax assets will be realized and, accordingly, a full valuation allowance has been established. The valuation allowance increased $15.6 million for the year ended December 31, 2019, $7.2 million for the six months ended December 31, 2018 and $765,000 and $7.5 million during the fiscal years ended June 30, 2018 and 2017, respectively, with such increases attributed to the re-measurement of the net deferred tax assets at the year-end dates. The valuation allowance decreased by $5.4 million from fiscal year 2018 activity, including the impact of the 2017 Tax Act, offset by an increase of $6.2 million related to the Icon acquisition.

The Company has tax net operating loss and tax credit carry forwards in its individual tax jurisdictions. Including approximately $49.3 million related to the Icon acquisition, at December 31, 2019 the Company had U.S. federal net operating loss carry forwards of approximately $236.6 million. The net operating losses consist of $151.8, which expire at various dates between calendar years 2023 and 2038. The utilization of certain of these loss and tax credit carry forwards may be limited by Sections 382 and 383 of the Internal Revenue Code as a result of historical or future changes in the Company’s ownership. At December 31, 2019, the Company had state net operating loss carry forwards of approximately $190.1 million, which expire between 2033 and 2038, as well as U.S. federal and state research and development tax credit carry forwards of approximately $3.1 million, which expire at various dates between calendar years 2018 and 2038. In addition, at December 31, 2019 the Company had net operating loss carry forwards in the U.K. of £21.0 million (approximately $26.7 million), which are not subject to any expiration dates.

The Company’s U.S. federal income tax returns for calendar years 2003 through 2017 remain subject to examination by the Internal Revenue Service. The Company’s U.K. tax returns for fiscal years 2006 through 2017 remain subject to examination.

Through December 31, 2019, the Company had no unrecognized tax benefits in its consolidated statements of comprehensive loss and no unrecognized tax benefits in its consolidated balance sheets as of December 31, 2019 and 2018, respectively.

As of December 31, 2019 and 2018, the Company had no accrued penalties or interest related to uncertain tax positions.