Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Loss Before Provision For (Benefit From) Income Taxes

Loss before (benefit from) provision for income taxes for the years ended December 31, 2019, 2018 and 2017 consist of the following (in thousands):



	Years Ended December 31,
	2019			2018			2017
United States	$	(508,595	)	$	(380,473	)	$	(247,784	)
Foreign	(6,121		)	(3,935		)	(8,212		)
Loss before (benefit from) provision for income taxes	$	(514,716	)	$	(384,408	)	$	(255,996	)

Provision For (Benefit From) Income Taxes

The (benefit from) provision for income taxes for the years ended December 31, 2019, 2018 and 2017 consist of the following components (in thousands):



	Years Ended December 31,
	2019			2018			2017
Current:
Federal	$	—		$	(26	)	$	(252	)
State	505			352			172
Total current	505			326			(80		)
Deferred:
Federal	(1,200		)	—			—
Total deferred	(1,200		)	—			—
Total (benefit from) provision for income taxes	$	(695	)	$	326		$	(80	)

Reconciliation of U.S. Statutory Income Tax Rate to Effective Tax Rate

The reconciliation of the U.S. statutory income tax rate to our effective tax rate for the years ended December 31, 2019, 2018 and 2017 are as follows:



	Years Ended December 31,
	2019		2018		2017
Tax effected at statutory rate	21.0	%	21.0	%	34.0	%
State taxes, net of federal benefit	7.9	%	6.3	%	8.5	%
Non-deductible items	1.6	%	0.0	%	(1.3	)%
Change in valuation allowance	(33.0	)%	(28.5	)%	(20.4	)%
Federal research and development credits	2.5	%	1.5	%	4.8	%
Foreign tax rate differential	(0.2	)%	(0.2	)%	(1.1	)%
Impact of federal rate change on net deferred taxes	0.0	%	0.0	%	(25.0	)%
Other	0.2	%	(0.2	)%	0.5	%
Effective tax rate	0.0	%	(0.1	)%	0.0	%

Significant Components of Deferred Tax Assets and Tax Liabilities

The significant components of our deferred tax assets and tax liabilities as of December 31, 2019 and 2018 are as follows (in thousands):



	December 31,
	2019			2018
Deferred tax assets:
Net operating loss carry-forwards	$	268,173		$	114,932
Stock-based compensation	43,978			33,138
Capitalized licenses, R&D and start-up costs	19,891			22,143
Tax credit carry-forwards	77,222			53,617
Accrued expenses	7,377			16,443
Deferred revenue	53,475			71,209
Operating lease liabilities	26,571			—
Lease financing obligation	10,570			9,149
Other	11			2,870
Total gross deferred tax assets	507,268			323,501
Less: valuation allowance	(470,753		)	(308,273		)
Total deferred tax assets, net of valuation allowance	36,515			15,228
Deferred tax liabilities:
Financing right-of-use assets	(2,612		)	—
Operating right-of-use assets	(24,944		)	—
Fixed assets	(8,959		)	(15,228		)
Total deferred tax liabilities	(36,515		)	(15,228		)
Net deferred tax assets	$	—		$	—

Reconciliation of the Beginning and Ending Amounts of Unrecognized Tax Benefits Roll Forward

A reconciliation of the beginning and ending amounts of unrecognized tax benefits during the years ended December 31, 2019 and 2018 are as follows (in thousands):



Balance as of December 31, 2017	$	940
Decrease due to prior positions	(799		)
Increase due to current year tax position	—
Balance as of December 31, 2018	141
Decrease due to prior positions	—
Increase due to current year tax positions	—
Balance as of December 31, 2019	$	141