Income Taxes (Tables)

12 Months Ended

Dec. 31, 2022

Income Tax Disclosure [Abstract]

Loss Before Income Taxes

Loss before income taxes for the years ended December 31 consisted of the following (in thousands):

	2022		2021		2020
Domestic	$	(160,542)	$	(116,178)	$	(111,101)
Foreign	1,316		1,091		1,276
Loss before income taxes	$	(159,226)	$	(115,087)	$	(109,825)

Significant Components of our Provision for Income Taxes

Significant components of our provision for income taxes for the years ended December 31 are as follows (in thousands):

	2022		2021		2020
Current:
Domestic	$	—	$	—	$	—
Foreign	317		167		253
Total provision for income taxes	$	317	$	167	$	253

Income Tax Expense (Benefit) Differed from Amounts Computed by Applying Statutory Federal Income Tax Rate

A reconciliation of the federal statutory income tax rate to the effective income tax rate for the years ended December 31 are as follows (in thousands):

	2022		2021		2020
Income tax provision at federal statutory rate	$	(33,706)	$	(24,168)	$	(23,063)
Tax on repatriated foreign earnings and other nondeductible items	284		580		348
Section 162(m) limitations	1,265		5,824		5,044
Change in tax credits	(3,501)		(2,514)		3,123
Change in valuation allowance	36,163		36,550		21,766
Changes in federal and state tax rates	2		(110)		586
Stock option exercise windfall	1,758		(9,761)		(7,683)
RTP and other true-ups	1,665		(2,823)		2,461
State and foreign tax, and other	(3,613)		(3,411)		(2,329)
Total provision for income taxes	$	317	$	167	$	253

Effect of Temporary Differences and Carryforwards

The effect of temporary differences and carryforwards that give rise to deferred tax assets and liabilities for the years ended December 31 were as follows (in thousands):

	2022		2021
Deferred tax assets:
Net operating loss carryforwards	$	146,108	$	131,971
Research and development tax credit carryforwards	15,529		12,028
Section 174 capitalized costs	17,076		—
Operating lease liability	5,736		6,423
Stock-based compensation	6,561		6,287
Foreign tax credit carryforwards	659		659
Accruals and other	12,603		10,139
Total deferred tax assets before allowance	204,272		167,507
Less: Valuation allowance	(198,980)		(162,817)
Deferred tax assets, net	5,292		4,690
Deferred tax liabilities:
Right of use asset and other	(4,329)		(4,690)
State net operating loss adjustments	(963)		—
Deferred tax liability	(5,292)		(4,690)
Net deferred tax assets and liabilities	$	—	$	—

Summary of Changes in Deferred Tax Asset Valuation Allowance

The table below summarizes changes in the deferred tax asset valuation allowance for the years ended December 31 (in thousands):

	2022		2021		2020
Balance at beginning of year	$	162,817	$	114,335	$	106,438
Impact of adoption of ASU 2020-06 on debt discount (equity component) deferred tax liability	—		11,932		—
Charged to costs and expenses	36,165		36,440		8,483
Impact of change in tax rate	(2)		110		(586)
Balance at end of year	$	198,980	$	162,817	$	114,335

Total Balance of Unrecognized Gross Tax Benefits Resulting from R&D Credits Claimed

The total balance of unrecognized gross tax benefits for the years ended December 31, resulting from research and development tax credits claimed on the Company’s annual tax return was as follows (in thousands):

	2022		2021		2020
Unrecognized tax benefits at beginning of year	$	10,009	$	9,171	$	4,212
Additions based on current year tax positions	1,167		838		4,959
Unrecognized tax benefits at end of year	$	11,176	$	10,009	$	9,171