Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of Provision for Federal Income Taxes

The provision for federal income taxes in 2017, 2016, and 2015 is as follows:

	December 31,
	2017			2016		2015
Current
Federal	$	(247	)	$	247	$	—
State		—			—		—
		(247	)		247		—
Deferred
Federal	$	—		$	—	$	—
State		—			—		—
Total deferred tax expense		—			—		—
Total income tax expense	$	(247	)	$	247	$	—

Schedule of Income (Loss) Before Income Taxes Attributed to Geographic Locations

	December 31,
	2017			2016			2015
United States	$	(125,093	)	$	(10,421	)	$	(17,671	)
Foreign		39,867			(85,149	)		(64,506	)
Net loss before provision for income taxes	$	(85,226	)	$	(95,570	)	$	(82,177	)

Summary of Statutory Federal Tax Rate to Income or Loss before Taxes

Income tax expense (benefit) in 2017, 2016, and 2015 differed from the amount expected by applying the statutory federal tax rate to the income or loss before taxes as summarized below:

	December 31,
	2017			2016			2015
Federal tax benefit at statutory rate		34	%		34	%		34	%
State tax benefit net of federal effect		—			—			—
Change in valuation allowance		(7	)%		(3	)%		(8	)%
Research and development credits		16	%		4	%		2	%
Non-deductible warrant		—			—			—
Foreign loss not benefitted		—			(30	)%		(26	)%
Other Non-deductible expenses		(3	)%		(5	)%		(2	)%
Change in rate differential		(38	)%		—			—
Build-to-suit adjustments		(2	)%		—			—
Total		0	%		0	%		0	%

Significant Components of Net Deferred Tax Assets

Significant components of the Company’s net deferred tax assets at December 31, 2016 and 2017 are as follows (in thousands):

	December 31,
	2017			2016
Net operating loss carry forwards	$	69,281		$	32,500
Research and development tax credits		34,891			8,142
Stock based compensation and other		5,693			7,256
Depreciation and amortization		—			78
Total deferred tax assets		109,865			47,976
Less: Valuation allowance		(108,782	)		(47,976	)
Deferred tax liabilities		(1,083	)		—
Net deferred tax assets	$	—		$	—

Reconciliation of Amount of Unrecognized Tax Benefits

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

	Amount
Balance at January 1, 2015	$	332
Increases based on tax positions taken during a prior period		3,562
Increases based on tax positions taken during a current period		167
Balance at December 31, 2015	$	4,061
Gross increase/ (decrease) related to prior year tax positions		1,069
Gross increase related to current year positions		4,986
Reductions to unrecognized tax benefits related to lapsing statute of limitations		—
Balance at December 31, 2016	$	10,116
Gross increase/ (decrease) related to prior year tax positions1		(7,776	)
Gross increase related to current year positions		1,594
Reductions to unrecognized tax benefits related to lapsing statute of limitations		—
Balance at December 31, 2017	$	3,934

¹ During 2017, the Company received new information related to its Orphan Drug Credit which provides clarification regarding tax

positions previously taken. As a result of this new information, Management re-assessed its Orphan Drug Credit uncertain tax position and made its best estimate to account for the higher level of certainty. The change in unrecognized tax benefit is fully offset by a corresponding change in valuation allowance and therefore has no impact on the income statement.