Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Taxes [Abstract]

Components of Loss Before Provision for Income Taxes

The components of loss before provision for income taxes for the years ended December 31, 2023, 2022 and 2021 are as follows (in thousands):

	2023			2022			2021
U.S. loss before provision for income taxes	$	(95,977	)	$	(132,442	)	$	(94,989	)
Foreign income before provision for income taxes		17			-			-
Loss before provision for income taxes	$	(95,960	)	$	(132,442	)	$	(94,989	)

Statutory to Effective Income Tax Rate Reconciliation

For purposes of reconciling the Company’s provision for income taxes at the statutory rate and the Company’s provision (benefit) for income taxes at the effective rate, a notional 21% tax rate was applied as follows:

	2023			2022			2021
Federal income tax at statutory rate		21.0	%		21.0	%		21.0	%
State income tax, net of federal benefit		7.81			4.10			7.0
Uncertain tax positions		(1.45	)		-			-
Tax credits generated in current year		0.68			1.90			2.8
Return to provision adjustments		(3.25	)		-			-
Stock-based compensation		(3.17	)		(0.50	)		1.6
Other		(0.10	)		0.90			0.6
Valuation allowance change		(21.52	)		(27.40	)		(33.0	)
Total		0.0	%		0.0	%		0.0	%

Provision for Income Taxes

The provision for income taxes for the years ended December 31, 2023, 2022 and 2021 consists of the following (in thousands):

	2023		2022		2021
Current:
Federal	$	-	$	-	$	-
State		-		-		-
Foreign		-		-		-
Total current		-		-		-
Deferred:
Federal		-		-		-
State		-		-		-
Foreign		-		-		-
Total deferred		-		-		-
Income tax provision	$	-	$	-	$	-

Deferred Tax Assets and Liabilities

The tax effects of temporary differences that give rise to significant portions of the Company’s deferred tax assets and liabilities as of December 31, 2023 and 2022 related to the following (in thousands):

	2023			2022
Deferred income tax assets:
Net operating loss carryforwards	$	89,525		$	77,008
Tax credit carryforwards		9,855			13,358
Stock-based compensation		4,528			7,309
Operating lease liabilities		3,385			4,344
Loss on marketable securities		2,195			5,724
Capitalized research and development		30,878			12,005
Other		2,938			3,925
Total deferred income tax assets	$	143,304		$	123,673
Deferred income tax liabilities:
Operating lease right-of-use assets	$	(215	)	$	(4,258	)
Property and equipment		(3,558	)		(381	)
Total deferred income tax liabilities		(3,773	)		(4,639	)
Valuation allowance		(139,531	)		(119,034	)
Net deferred tax assets (liabilities)	$	-		$	-

Gross Unrecognized Tax Benefits

The following table summarizes the activity related to the Company’s gross unrecognized tax benefits as of December 31, 2023, 2022 and 2021 (in thousands):

	2023		2022		2021
Beginning balance	$	-	$	-	$	-
Increases related to prior year tax positions		1,310		-		-
Increases related to current year tax positions		69		-		-
Ending balance	$	1,379	$	-	$	-