Income Taxes

12 Months Ended

Dec. 31, 2025

Income Tax Disclosure [Abstract]

Income Taxes

Note 12. Income Taxes

The Company adopted ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures effective January 1, 2025, on a prospective basis. The disclosures required by the standard are included below for the year ended December 31, 2025. Comparative prior-period disclosures have not been revised.

The components of loss before income taxes were as follows (in thousands):

	Year Ended December 31,
	2025
Domestic	$	(311,351	)
Total loss before income taxes	$	(311,351	)

The Company has had immaterial tax expense due to operating losses incurred since inception and no deferred tax provision in the current period.

The following table reconciles the U.S. federal statutory income tax rate to the Company’s effective income tax rate for the year ended December 31, 2025 (in thousands):

	Year Ended December 31, 2025
	Amount ($)			Percentage (%)
Federal statutory income tax rate	$	(65,384	)		21.0		%
State income taxes, net of federal income tax effect		(99	)		0.0
Research and development tax credits		(6,982	)		2.2
Changes in valuation allowances		72,265			(23.2	)
Nontaxable or nondeductible items:
Excess tax benefits on share-based payments		9485			(3.0	)
Stock-based compensation		(9407	)		3.0
Other		122			0.0
Effective income tax rate	$	—			0.0		%

As previously disclosed for the years ended December 31, 2024 and 2023, prior to the adoption of ASU 2023-09, the effective income tax rate differed from the federal statutory income tax rate as follows:

	Year Ended December 31,
	2024		2023
Federal statutory income tax rate	21.0	%	21.0	%
State income taxes, net of federal benefit	7.9		6.8
Federal and state research and development tax credits	6.1		4.6
Stock-based compensation	0.3		(1.5)
Disallowed Expenditures	(2.3)		(2.3)
Change in deferred tax asset valuation allowance	(33.0)		(28.6)
Effective income tax rate	0.0	%	0.0	%

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amount of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The significant components of the Company’s net deferred income taxes were as follows (in thousands):

	December 31,
	2025			2024
Deferred Tax Assets:
Net operating loss carryforwards	$	159,311		$	61,531
Research and development credit carryforwards		54,742			42,549
Lease liabilities		21,716			22,980
Deferred revenue		—			3,603
Accruals and reserves, stock and other		18,633			18,794
Capitalized Research and Development		96,991			110,333
Total deferred tax assets	$	351,393		$	259,790
Valuation allowance		(330,285	)		(236,206	)
Total deferred tax assets, net of valuation allowance	$	21,108		$	23,584
Deferred Tax Liabilities:
Operating right-of-use assets		(9,477	)		(10,632	)
Depreciation		(11,631	)		(12,952	)
Total deferred tax liabilities		(21,108	)		(23,584	)
Net deferred tax assets	$	—		$	—

The changes in the valuation allowance were as follows (in thousands):

	Year Ended December 31,
	2025
Beginning balance	$	236,206
Domestic federal income taxes		72,265
Domestic state & local income taxes		21,814
Ending balance	$	330,285

The Company has evaluated the positive and negative evidence bearing upon the reliability of its deferred tax assets. Based on this, the Company has provided a valuation allowance for the full amount of the net deferred tax assets as the realization of the deferred tax assets is not determined to be more likely than not. During the year ended December 31, 2025, the valuation allowance increased by $94.1 million primarily due to the increase in the Company’s net operating loss, capitalized expenditures and tax credit carryforwards during the period.

As of December 31, 2025, the Company had $571.6 million and $607.5 million of federal and state operating loss carryforwards, respectively. Substantially all of the federal net operating losses ("NOLs") are not subject to expiration and the state NOLs begin to expire in 2037. These loss carryforwards are available to reduce future federal and state taxable income, if any. As of December 31, 2025, the Company also had federal and state research and development tax credit carryforwards of $40.1 million and $18.6 million respectively, to offset future income taxes, which will begin to expire in December 2039. These loss carryforwards are subject to review and possible adjustment by the appropriate taxing authorities.

Utilization of the Company’s NOL carryforwards and research and development credit carryforwards may be subject to a substantial annual limitation due to ownership change limitations that have occurred previously or that could occur in the future in accordance with Section 382 as well as similar state provisions. These ownership changes may limit the amount of NOL and research and development credit carryforwards that can be utilized annually to offset future taxable income and taxes, respectively. In general, an ownership change as defined by Section 382 results from transactions increasing the ownership of certain stockholders or public groups in the stock of a corporation by more than 50% over a three-year period. Since its formation, the Company has raised capital through the issuance of capital stock on several occasions. These financings could result in a change of control as defined by Section 382. The Company has not yet conducted an analysis under Section 382 to determine if historical changes in ownership through December 31, 2025, would limit or otherwise restrict its ability to utilize its NOL and research and development credit carryforwards. In addition, future changes in ownership occurring after

December 31, 2025 could affect the limitation in future years, and any limitation may result in expiration of a portion of the NOL or research and development credit carryforwards before utilization.

On July 4, 2025, the One Big Beautiful Bill Act (“OBBBA”) was signed into law. Among other provisions, this act includes permanently extended and modified certain expiring provisions of the 2017 Tax Cuts and Jobs Act and restored the immediate expensing of domestic research and development expenses. The Company has evaluated the impacts of these provisions and has concluded the OBBBA does not have a material impact on its consolidated financial statements other than reclassifications of the deferred tax assets.

The Company follows the provisions of ASC Topic 740-10, Accounting for Uncertainty in Income Taxes, which specifies how tax benefits for uncertain tax positions are to be recognized, measured, and recorded in financial statements; requires certain disclosures of uncertain tax matters; specifies how reserves for uncertain tax positions should be classified on the consolidated balance sheets; and provides transition and interim period guidance, among other provisions. As of December 31, 2025 and 2024, the Company has not recorded any amounts for uncertain tax positions. The Company’s policy is to recognize interest and penalties accrued on any uncertain tax positions as a component of income tax expense, if any, in its consolidated statements of operations and comprehensive loss. As of December 31, 2025 and 2024, the Company had no reserves for uncertain tax positions. For the years ended December 31, 2025, 2024, and 2023, no estimated interest or penalties were recognized on uncertain tax positions.

The Company files federal income tax returns in the United States and state income tax returns in Massachusetts and various other state jurisdictions. The Company’s tax returns for the years ended December 31, 2022 to December 31, 2025 remain open and subject to examination by the Internal Revenue Service and state taxing authorities.