Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Taxes [Abstract]

Loss Before Income Taxes

Loss before income taxes is comprised of (in thousands):

	Year Ended December 31,
	2023			2022			2021
United States	$	(334,707	)	$	(258,493	)	$	(29,966	)
Foreign		742			508			818
Loss before income taxes	$	(333,965	)	$	(257,985	)	$	(29,148	)

Income Tax Expense (Benefit)

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

	Year Ended December 31,
	2023			2022		2021
Current:
Federal	$	35,861		$	10,522	$	(200	)
State		(3,687	)		1,129		(690	)
Foreign		147			86		339
Total current income tax expense (benefit)		32,321			11,737		(551	)
Deferred:
Federal		—			—		—
State		—			—		—
Total deferred income tax benefit		—			—		—
Total income tax expense (benefit)	$	32,321		$	11,737	$	(551	)

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 loss before income taxes. The sources and tax effects of the differences are as follows (in thousands):

	Year Ended December 31,
	2023					2022					2021
Pre-tax loss	$	(333,965	)			$	(257,985	)			$	(29,148	)
Statutory rate		(70,133	)	21.0	%		(54,177	)	21.0	%		(6,121	)	21.0	%
State income tax net of federal benefit		(22,597	)	6.8	%		(13,622	)	5.3	%		4,278		(14.7	)%
Foreign		(22	)	0.0	%		(49	)	0.0	%		143		(0.5	)%
Net change in valuation allowance		175,388		(52.5	)%		104,951		(40.7	)%		2,885		(9.9	)%
Loss on debt transactions		—		—			—		—			262		(0.9	)%
Tax credits		(67,131	)	20.1	%		(39,729	)	15.4	%		(23,198	)	79.6	%
Deferred tax true-up		4		0.0	%		(20	)	0.0	%		(24	)	0.1	%
Tax rate change		1,023		(0.3	)%		(3,091	)	1.2	%		12,838		(44.0	)%
Non-deductible compensation		3,814		(1.1	)%		3,023		(1.2	)%		5,085		(17.4	)%
Other non-deductible items		327		(0.1	)%		57		0.0	%		84		(0.3	)%
Foreign-derived intangible income benefit		(7,493	)	2.2	%		—		—			—		—
Stock-based compensation		19,546		(5.9	)%		14,030		(5.4	)%		4,720		(16.2	)%
Other		(405	)	0.1	%		364		(0.1	)%		(1,503	)	5.1	%
Effective rate	$	32,321		(9.7	)%	$	11,737		(4.5	)%	$	(551	)	1.9	%

Deferred Tax Assets and Liabilities

Significant components of our deferred tax assets and liabilities as of December 31, 2023 and 2022 are as follows (in thousands):

	Year Ended December 31,
	2023			2022
Deferred Tax Assets:
Net operating loss carryovers	$	77,964		$	87,802
Tax credits		239,962			277,436
Deferred revenue		71,683			85,700
Stock-based compensation		77,468			86,983
Intangible and capital assets		104,380			104,649
Convertible debt		16,849			34,384
Capitalized research and development expenses		238,738			119,635
Long-term lease liabilities		43,718			45,612
Sale of future royalties		144,608			—
Other		10,343			15,813
Total deferred tax assets	$	1,025,713		$	858,014
Deferred Tax Liabilities:
Fixed assets		(4,166	)		(4,475	)
Right-of-use assets		(42,007	)		(44,504	)
Other		(1,910	)		(313	)
Net deferred tax asset	$	977,630		$	808,722
Valuation allowance		(977,630	)		(808,722	)
Total net deferred tax assets and liabilities	$	—		$	—

Gross Unrecognized Tax Benefits

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

	Year Ended December 31,
	2023			2022			2021
Beginning balance of unrecognized tax benefits	$	56,567		$	55,085		$	54,163
Decrease for lapse of statute of limitations		(14,993	)		—			—
Decrease for prior period tax positions		(737	)		(267	)		(695	)
Increase for prior period tax positions		429			259			263
Increase for current period tax positions		2,032			1,490			1,354
Ending balance of unrecognized tax benefits	$	43,298		$	56,567		$	55,085