Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Taxes [Abstract]

Income (Loss) Before Income Taxes

Income (loss) before income taxes is comprised of (in thousands):

	Year Ended December 31,
	2021			2020			2019
				(as revised*)			(as revised*)
United States	$	(29,966	)	$	(137,222	)	$	336,277
Foreign		818			2,670			2,489
Income (loss) before income taxes	$	(29,148	)	$	(134,552	)	$	338,766

Income Tax Expense (Benefit)

Our income tax expense (benefit) was as follows (in thousands):

	Year Ended December 31,
	2021			2020			2019
				(as revised*)			(as revised*)
Current:
Federal	$	(200	)	$	(837	)	$	35,861
State		(690	)		3,782			14,329
Foreign		339			518			413
Total current income tax expense (benefit)		(551	)		3,463			50,603
Deferred:
Federal		—			341,728			904
State		—			—			—
Total deferred income tax benefit		—			341,728			904
Total income tax expense (benefit)	$	(551	)	$	345,191		$	51,507

Reconciliation of Statutory to Effective Tax Rate

Our expense (benefit) for income taxes differs from the amount computed by applying the U.S. federal statutory rate to income (loss) before taxes. The sources and tax effects of the differences are as follows (in thousands):

	Year Ended December 31,
	2021					2020					2019
						(as revised*)					(as revised*)
Pre-tax income (loss)	$	(29,148	)			$	(134,552	)			$	338,766
Statutory rate		(6,121	)	21.0	%		(28,256	)	21.0	%		71,141		21.0	%
State income tax net of federal benefit		4,278		(14.7	)%		(37,705	)	28.0	%		49,000		14.5	%
Foreign		143		(0.5	)%		49		0.0	%		340		0.1	%
Net change in valuation allowance		2,885		(9.9	)%		460,898		(342.5	)%		(37,314	)	(11.0	)%
Loss on debt transactions		262		(0.9	)%		—		—			9,911		2.9	%
Impact from outside basis differences		—		—			—		—			(16,344	)	(4.8	)%
Tax credits		(23,198	)	79.6	%		(18,774	)	14.0	%		(22,296	)	(6.6	)%
Deferred tax true-up		(24	)	0.1	%		(206	)	0.2	%		646		0.2	%
Tax rate change		12,838		(44.0	)%		(32,951	)	24.5	%		1,248		0.4	%
Non-deductible compensation		5,085		(17.4	)%		7,931		(5.9	)%		3,361		1.0	%
Other non-deductible items		84		(0.3	)%		193		(0.1	)%		329		0.1	%
Stock-based compensation		4,720		(16.2	)%		17,435		(13.0	)%		(4,837	)	(1.4	)%
Foreign-derived intangible income benefit		—		—			—		—			(2,071	)	(0.6	)%
Impacts from Akcea Merger		—		—			(22,032	)	16.4	%		—		—
Other		(1,503	)	5.1	%		(1,391	)	0.9	%		(1,607	)	(0.6	)%
Effective rate	$	(551	)	1.9	%	$	345,191		(256.5	)%	$	51,507		15.2	%

Deferred Tax Assets and Liabilities

Significant components of our deferred tax assets and liabilities as of December 31, 2021 and 2020 are as follows (in thousands):

	Year Ended December 31,
	2021			2020
				(as revised*)
Deferred Tax Assets:
Net operating loss carryovers	$	85,600		$	83,681
Tax credits		269,538			245,746
Deferred revenue		104,330			124,452
Stock-based compensation		86,611			80,055
Intangible and capital assets		92,542			98,443
Convertible debt		45,681			22,395
Interest expense limitation		6,996			—
Other		15,048			13,402
Total deferred tax assets	$	706,346		$	668,174
Deferred Tax Liabilities:
Fixed assets		(3,303	)		(3,611	)
Other		(5,270	)		(5,808	)
Net deferred tax asset	$	697,773		$	658,755
Valuation allowance		(697,773	)		(658,755	)
Total net deferred tax assets and liabilities	$	—		$	—

* We revised our 2020 and 2019 amounts to reflect the simplified convertible instruments accounting guidance, which we adopted retrospectively. Refer to Note 1, Organization and Significant Accounting Policies, for further information.

Gross Unrecognized Tax Benefits

The following table summarizes our gross unrecognized tax benefits (in thousands):

	Year Ended December 31,
	2021			2020			2019
Beginning balance of unrecognized tax benefits	$	54,163		$	69,784		$	68,301
Decrease for prior period tax positions		(695	)		(24,154	)		(867	)
Increase for prior period tax positions		263			7,023			736
Increase for current period tax positions		1,354			1,510			1,614
Ending balance of unrecognized tax benefits	$	55,085		$	54,163		$	69,784