Income Taxes

12 Months Ended

Dec. 31, 2024

Income Taxes [Abstract]

Income taxes

8. Income taxes

As of December 31, 2024 and 2023, a valuation allowance was recorded against all deferred tax assets due to our cumulative net loss position.

The components of our provision for income taxes are as follows for the periods indicated:

		Year Ended
		December 31,
(in thousands)		2024		2023
Current
Federal and state	$	—	$	—
Foreign		55		147
Total provision for income taxes	$	55	$	147

The reconciliation of taxes at the federal statutory rate to our provision for income taxes are as follows for the periods indicated:

	Year Ended
	December 31,
	2024		2023
Tax at federal statutory rate	21.0	%	21.0	%
Permanent differences	(4.2)		(4.3)
Research and development ("R&D") tax credit	0.8		1.4
Uncertain tax position	(0.1)		(0.3)
State, net of federal benefit	2.0		2.6
Deferred rate change	(0.3)		0.4
Change in valuation allowance	(19.3)		(21.2)
Total	(0.1)	%	(0.4)	%

Significant components of net deferred tax assets were as follows for the periods indicated:

		Year Ended
		December 31,
(in thousands)		2024		2023
Deferred tax assets
Net operating loss carryforwards	$	98,329	$	89,173
R&D tax credits		10,147		9,664
Capitalized R&D expenses		8,015		8,963
Non-qualified stock options		4,482		1,473
Start-up costs		452		680
Accrued vacation		227		179
Other		450		420
Total deferred tax assets		122,102		110,552
Valuation allowance		(122,102)		(110,552)
Net deferred tax assets	$	—	$	—

As of December 31, 2024, we had federal and state net operating loss carryforwards (“NOLs”) of approximately $429.7 million and $8.1 million, respectively. The federal NOLs began expiring in 2021 and the state NOLs began expiring in 2020. As of December 31, 2024, we had federal and state tax credit carryforwards of approximately $10.2 million and $1.7 million, respectively. The federal tax credit carryforwards began expiring in 2021 and the state tax credits will begin expiring in 2028.

Utilization of NOLs may be subject to an annual limitation due to the ownership change limitations provided by Section 382 of the Internal Revenue Code of 1986, as amended, and similar state provisions. We have not performed a detailed analysis to determine whether an ownership change has occurred. Such a change of ownership would limit our utilization of the NOLs and could be triggered by subsequent sales of securities by us or our stockholders.

The changes to our gross unrecognized tax benefits were as follows for the periods indicated:

		Year Ended
		December 31,
(in thousands)		2024		2023
Gross unrecognized tax benefits at beginning of year	$	2,221	$	2,046
Gross increases:
Prior year tax positions		—		12
Current year tax positions		182		185
Gross decreases:
Prior year tax positions		(57)		(22)
Gross unrecognized tax benefits at end of year	$	2,346	$	2,221

All of these unrecognized tax benefits, if recognized, would impact the effective tax rate before taking consideration of the valuation allowance. The amount of unrecognized tax benefits subjected to the valuation allowance was $1.8 million and $1.7 million for the years ended December 31, 2024 and 2023, respectively. We recognized a nominal amount and approximately $0.1 million of interest or penalties for each of the years ended December 31, 2024 and 2023, respectively. As of December 31, 2024 and 2023, total accrued interest and penalties were both $0.5 million. We recognize accrued interest and penalties related to unrecognized tax positions as a component of income tax expense. We do not expect a significant change in the amount of unrecognized tax benefits in the next year.

We are subject to U.S. federal income tax as well as income tax of multiple state and foreign jurisdictions. Tax years from 2005 through present remain open for audit under the applicable statute of limitations due to

the carryover of the unused NOLs and tax credit carryforwards. We do not have any tax audits or other proceedings pending.