Immunome Inc.

Segment Financial Information

We are filing Exhibit 99.1 to this Quarterly Report solely to recast certain segment financial information and related disclosures included in our Annual Report on Form 10-K for the year ended December 31, 2025, originally filed with the SEC on March 3, 2026, or the 2025 Form 10-K. The recast information reflects changes in the research and development expenses by program that are regularly reviewed by our Chief Operating Decision Maker, or CODM, when evaluating our financial performance. These changes were implemented during the first and third quarters of 2026, as described below and in our Quarterly Reports for the periods ended March 31, 2026 and June 30, 2026, filed with the SEC on May 12, 2026 and August 11, 2026, respectively, and this Quarterly Report for the period ending September 30, 2026. The information in Exhibit 99.1 to this Quarterly Report is not an amendment or restatement of the 2025 Form 10-K.

Commencing in the first quarter of 2026, we revised the presentation of our significant segment expense categories reviewed by the CODM to separately disclose costs incurred during the reporting periods associated with the IM-1617 program following our Investigational New Drug application clearance from the United States Food and Drug Administration. Additionally, within this Quarterly Report, we revised the presentation of our significant segment expense categories reviewed by the CODM to separately disclose costs incurred during the reporting periods associated with the IM-1340 program following our Investigational New Drug application clearance from the United States Food and Drug Administration. Prior period amounts had been reclassified to conform to the current year presentation, and there was no impact to our consolidated financial statements for any period presented.

There were also updates to certain MD&A disclosures presented in components of our results of operations to the consolidated financial statements to align with our newly established methodology for significant segment expense categories. These category methodologies are subject to periodic refinement due to the development of programs and product candidates.

SEC rules require that when a registrant prepares, on or after the date a registrant reports an accounting change such as the significant segment expense category changes noted above, a new registration, proxy, or information statement (or amends a previously filed registration, proxy, or information statement) that includes or incorporates by reference financial statements, the registrant must recast the prior period financial statements included or incorporated by reference in the registration, proxy, or information statement to reflect these types of changes. Accordingly, we are filing Exhibit 99.1 to this Quarterly Report to update historical operating segment financial information and related disclosures contained in the 2025 Form 10-K to reflect the changes in the significant segment expense categories regularly reviewed by the CODM as described above. The updates do not represent a restatement of previously issued financial statements. The recast information of the items contained in the 2025 Form 10-K is presented in Exhibit 99.1 to this Quarterly Report.

The information included in Exhibit 99.1 to this Quarterly Report is presented for informational purposes only in connection with the segment reporting changes described above and does not amend or restate our audited consolidated financial statements, which were included in the Company's 2025 Form 10-K. The information included in Exhibit 99.1 to this Quarterly Report does not reflect events occurring after we filed the 2025 Form 10-K and does not modify or update the disclosures therein in any way, other than to illustrate the impact of the significant segment expense category changes as described above. Exhibit 99.1 to this Quarterly Report should be read in conjunction with the 2025 Form 10-K. For developments subsequent to the filings of the 2025 Form 10-K, refer to our Quarterly Reports on Form 10-Q for the periods ended March 31, 2026 and June 30, 2026, to the information contained in this Quarterly Report for the period ended September 30, 2026, and to our Current Reports on Form 8-K.

Rule 10b5-1 Plans

During the quarter ended September 30, 2026, none of our directors or officers (as defined in Rule 16a-1(f) under the Exchange Act) or directors adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement” as those terms are defined in Item 408 of Regulation S-K.