Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Losses Before Provision for Income Taxes

Losses before provision for income taxes were as follows in each period presented:

	Year Ended December 31,
	2021			2020			2019
	(in thousands)
United States	$	(340,301	)	$	(306,758	)	$	(291,049	)
Foreign		206			153			85
Total loss before provision for income taxes	$	(340,095	)	$	(306,605	)	$	(290,964	)

Components of Provision for (Benefit from) Income Taxes

The components of provision for (benefit from) income taxes were as follows in each period presented:

	Year Ended December 31,
	2021		2020		2019
	(in thousands)
Current provision for (benefit from) income taxes:
State		4		2		—
Foreign		42		13		12
Total current provision for (benefit from) income    taxes	$	46	$	15	$	12

Reconciliation of Statutory Tax Rates to Effective Tax Rates

A reconciliation of statutory tax rates to effective tax rates were as follows in each of the periods presented:

	Year Ended December 31,
	2021			2020			2019
Federal income taxes at statutory rate		21.0	%		21.0	%		21.0	%
Impact of stock compensation		(2.0	%)		(2.4	%)		0.1	%
Non-deductible executive compensation		(0.2	%)		(0.1	%)		(0.7	%)
Other		(0.1	%)		0.3	%		(0.2	%)
Change in valuation allowance		(18.7	%)		(18.8	%)		(20.2	%)
Effective tax rate		0.0	%		0.0	%		0.0	%

Components of Deferred Tax Assets and Liabilities

Significant components of our deferred tax assets and liabilities were as follows for each of the dates presented:

	As of December 31,
	2021			2020
	(in thousands)
Deferred tax assets:
Net operating losses	$	308,997		$	237,010
Stock-based compensation		24,181			20,672
Capitalized expenses		10,499			12,590
License fees		8,716			8,159
Operating lease liabilities		7,972			4,251
Legal fees		2,366			2,136
Tax credits		1,580			1,580
Deferred Revenue		12,133			—
Other		7,048			5,360
Total deferred tax assets		383,492			291,758
Valuation allowance		(376,071	)		(287,349	)
Total deferred tax assets		7,421			4,409
Deferred tax liabilities:
Operating lease assets		(7,421	)		(3,541	)
Other		—			(868	)
Total deferred tax liabilities		(7,421	)		(4,409	)
Net deferred tax assets (liabilities)	$	—		$	—

Reconciliation of Beginning and Ending Amount of Gross Unrecognized Tax Benefits

The changes in the balance of gross unrecognized tax benefits, which excludes interest and penalties, for the years ended December 31, 2019, 2020 and 2021 are as follows:

	(In thousands)
Balance as of January 1, 2019	$	41,074
Gross increases for tax positions related to current year		22,800
Gross increases for tax positions related to prior year		22,126
Gross decreases for tax positions related to prior year		—
Balance as of December 31, 2019		86,000
Gross increases for tax positions related to current year		24,648
Gross increases for tax positions related to prior year		—
Gross decreases for tax positions related to prior year		(47	)
Balance as of December 31, 2020		110,601
Gross increases for tax positions related to current year		28,171
Gross increases for tax positions related to prior year		5,295
Gross decreases for tax positions related to prior year		—
Balance as of December 31, 2021	$	144,067