Enliven Therapeutics, Inc. Income Taxes Disclosure

11. Income Taxes

The Company’s losses before income taxes for the years ended December 31, 2025 and 2024 consist entirely of losses from domestic operations. For the year ended December 31, 2025, the Company did not record a provision for income taxes. For the year ended December 31, 2024, the Company had income taxes of $232,000 related to the Section 453A interest charge in connection with the CVR milestone payment, as discussed in Note 3.

As further described in Note 2, "Summary of Significant Accounting Policies," the Company has elected to retrospectively adopt the guidance in ASU 2023-09. The following table is a reconciliation of the U.S. federal statutory rate of 21% to the Company’s effective

Significant components of the Company’s deferred income taxes consist of the following (in thousands):

Realization of tax assets is dependent upon future earnings, the timing and amount of which are uncertain. Accordingly, the U.S. net deferred tax assets have been fully offset by a valuation allowance. The changes in the valuation allowance for the years ended December 31, 2025 and 2024 were $28.6 million and $20.9 million, respectively. The increase in deferred tax assets and valuation allowance during the current year was primarily related to the generation of net operating losses and the capitalization of research and development costs.

As of December 31, 2025 and 2024, the Company had federal net operating loss carryforwards of approximately $266.9 million and $203.5 million, respectively. The 2017 Tax Cuts and Jobs Act (“TCJA”) generally allows losses incurred after 2017 to be carried over indefinitely, but limits the net operating loss deduction to the lesser of the net operating loss carryover or 80% of a corporation’s

taxable income (subject to Internal Revenue Code of 1986, as amended (“IRC”), Section 382). Additionally, there is no carryback for losses incurred after 2017. Losses incurred prior to 2018 are generally deductible to the extent of the lesser of a corporation’s net operating loss carryover or 100% of its taxable income and are available for twenty years from the period the loss was generated. The Company has federal net operating losses generated following 2017 of $258.9 million, which do not expire. The federal net operating losses generated prior to 2018 of $8.0 million will expire beginning in 2037.

As of December 31, 2025 and 2024, the Company had state net operating loss carryforwards of approximately $342.6 million and $265.8 million, respectively. The state net operating loss carryforwards will expire at various dates through 2045.

As of December 31, 2025 and 2024, the Company had federal research and development credit carryforwards of approximately $16.0 million and $13.4 million, respectively, which are available to offset future federal income tax liabilities and expire at various dates through 2045. As of December 31, 2025 and 2024, the Company had state research and development credit carryforwards of approximately $3.1 million and $2.3 million, respectively, which are available to reduce future state tax liabilities. The Company has California research and development credit carryforwards of approximately $2.3 million, which do not expire. The remaining state research and development credit carryforwards will expire at various dates through 2040.

Section 382 and Section 383, and corresponding provisions of state law, impose limitations on the use of net operating loss carryforwards when the stock ownership of one or more 5% stockholders (stockholders owning 5% or more of the Company’s outstanding capital stock) has increased on a cumulative basis by more than 50 percentage points. There is a risk of an ownership change beyond the control of the Company that could trigger a limitation of the use of the loss carryover. As of December 31, 2025, the Company has completed an analysis and determined ownership changes occurred under Section 382 in the past, including in 2023 due to the Merger. The Company’s deferred tax assets have been reduced by $0.9 million and $65.7 million of net operating loss carryforwards expected to expire unused due to the limitation for federal and state, respectively. The Company’s deferred tax assets have also been reduced by $8.8 million and $0.8 million of credit carryforwards expected to expire due to the limitation for federal and state, respectively. Additionally, in the future, the Company may experience ownership changes which, if they occur, could substantially limit its ability to utilize its net operating loss and other tax carryforwards. A full valuation allowance has been established against the deferred tax assets related to the Company’s net operating losses and tax credit carryforwards. Any future adjustments would be entirely offset by an adjustment to the valuation allowance.

The Company adopted the provisions of FASB ASC 740-10, Accounting for Uncertainty in Income Taxes, upon the date of incorporation. ASC 740-10 prescribes a comprehensive model for the recognition, measurement, presentation and disclosure in financial statements of any uncertain tax positions that have been taken or expected to be taken on a tax return. It is the Company’s policy to include penalties and interest expense related to income taxes as a component of its income tax expense, as necessary. As of December 31, 2025, the Company has not recognized any tax-related penalties or interest. As of December 31, 2025 and 2024, the gross unrecognized tax benefit was $34.5 million and $33.5 million, respectively, none of which if recognized would reduce the effective tax rate in a future period, due to the Company’s full valuation allowance on U.S. net deferred tax assets. The following table summarizes the changes to the Company’s unrecognized tax benefits (in thousands):

The Company has filed a U.S. federal income tax return and state tax returns in various states. The federal and state income tax returns are generally subject to examination for the tax years ended December 31, 2022 through the present. To the extent that the Company has tax attribute carryforwards, the tax year in which the attributes were generated may still be adjusted upon examination by the Internal Revenue Service or State taxing authorities to the extent utilized in a future period. The Company is not currently under examination by any tax authorities.

On July 4, 2025, the OBBBA was signed into law and introduced significant changes to U.S. income-tax legislation. Key provisions affecting the Company include (i) permanent immediate expensing of domestic research and experimental expenditures starting January 1, 2025, and (ii) 100 percent bonus depreciation for qualified property placed in service after January 19, 2025.

The Company has evaluated the current legislation at this time and prepared the provision by following the treatment of research and development expenditures for tax purposes under Section 174 and 174A. For domestic R&D costs incurred in tax years 2022–2024, the Company elected to continue amortizing the costs over its historical 5-year period under Section 174. For domestic R&D costs incurred in the current tax year under Section 174A, the Company is treating the costs as immediately deductible.