EO-2463

New data show 100% (6/6) objective response rate (ORR) with EO2463 in previously untreated patients with follicular lymphoma needing treatment in combination with rituximab (SIDNEY Cohort 3)Of the 6 patients, 5 had a complete response (CR), 1 partial response (PR)Patients with follicular lymphoma in watch-and-wait setting (SIDNEY Cohort 2) showed a 52.6% ORR with EO2463 monotherapy Paris, France – 9 DECEMBER 2025 (08:30 CET)Enterome, a clinical-stage company pioneering OncoMimics™, a new class of off-the-shelf, multi-targeted in vivo immune therapies that induce a fast and potent expansion of memory T-cells to fight cancer, today presents highly encouraging updated interim data from two cohorts of patients with low tumor-burden follicular lymphoma in the ongoing SIDNEY Phase 2 trial of its lead OncoMimics™ immunotherapy EO2463. The data were presented at the 67th meeting of the American Society for Hematology (ASH) in Orlando, Florida. In Cohort 3, 100% (6/6) ORR was achieved with EO2463 plus rituximab as first-line treatment for previously untreated patients with low tumor-burden follicular lymphoma in need of treatment. In this feasibility assessment among the 6 patients, 5 had a complete response, and one a partial response. The median time to OR was 17 weeks, and to CR 18 weeks. These results marked an improvement over preliminary data submitted in the abstract for ASH. “These new results are encouraging, despite the limited number of patients. The potent and rapid expansion of specific CD8 T-cells induced by EO2463 supports our understanding that OncoMimics™ trigger memory T-cells to generate sustained immune responses. The data suggest that the combination therapy given as a first-line treatment in patients with low-tumor burden follicular lymphoma should be evaluated in further studies,” said Dr Stephen Smith, principal study investigator at the Fred Hutchinson Cancer Center, University of Washington, Seattle, WA, USA, who presented the data. Data from Cohort 2 continue to show that EO2463 monotherapy produces excellent response rates when offered to patients with newly diagnosed follicular lymphoma or marginal zone lymphoma as an alternative to the standard watch-and-wait regime. Previously undisclosed data from 19 evaluable patients with follicular lymphoma showed a 52.6% ORR as of October. The ORR in the total group of 21 patients with follicular lymphoma or marginal zone lymphoma was 47.6% (14.3% CR and 33.3% PR). Current standard of practice is that, while patients often have visibly swollen lymph nodes, no treatment other than watchful waiting is suggested, as long as they do not show troublesome symptoms. Nevertheless, these patients often are understandably anxious about their disease, which progresses in the majority of cases, and then leads to a decreased quality of life. “These new data with EO2463 contribute more compelling evidence and further strengthen our belief in the potential of our OncoMimics™ multi-targeted in vivo immune therapies for blood cancers. I’m looking forward to initiating Phase 3 testing of EO2463 in patients in the watch-and-wait setting in 2026,” said Pierre Belichard, CEO of Enterome. Follicular Lymphoma, one of several types of indolent Non-Hodgkin Lymphoma, is a difficult to treat chronic condition with relapses, characterized by slow progression and few symptoms, and reduced life expectancy. It is usually diagnosed by the appearance of swollen lymph nodes, and the early stages of the disease can be characterized by a lack of troublesome symptoms such as night sweats, fever or weight loss. There is a widespread consensus among leading investigators on the need for a well-tolerated and effective monotherapy to stop or slow progression for patients in the watch-and-wait setting. EO2463 is an innovative, off-the-shelf OncoMimics™ active immunotherapy that combines four synthetic peptides. These non-self, microbial-derived peptides correspond to CD8 HLA-A2 epitopes that exhibit molecular mimicry with the B lymphocyte-specific lineage markers CD20, CD22, CD37, and CD268 (BAFF receptor). It also includes the helper peptide (CD4+ epitope) universal cancer peptide 2 (UCP2). The unique ability of EO2463 to selectively target multiple B cell markers enables the destruction of malignant B lymphocytes. By ensuring broad target coverage across malignant B cells, this novel approach aims to simultaneously improve safety and maximize efficacy, reducing the tumor cells’ capacity to develop immune-resistance mechanisms such as antigen escape. OncoMimics™ consist of bacteria-derived peptide antigens that closely mimic tumor-associated antigens (TAAs) of solid tumors, or cell linage markers as for B cell lymphomas. These antigens induce a fast and potent in vivo expansion of cytotoxic memory CD8+ T cells that were primed by gut bacteria, and are cross-reactive with TAAs/B cell markers. Because the peptides are “non-self”, OncoMimics™ avoid the self-tolerance that limits many cancer immunotherapies to enable rapid, potent, and durable responses to tumors. The synthetically produced peptides are designed in silico, mining Enterome’s proprietary database of 23 million commensal bacteria genes. Each product combines multiple high-affinity peptides to broaden target coverage and mitigate tumor heterogeneity. OncoMimics™ are easy to manufacture, store, distribute and administer as an “off-the-shelf” subcutaneous injection. OncoMimics™ have achieved rapid and potent responses in clinical testing in over 230 patients to date, with a benign safety profile. Enterome SA (www.enterome.com) is a privately held clinical-stage biopharmaceutical company developing OncoMimics™, a breakthrough in in vivo immune therapies for cancer. The three most advanced product candidates have shown positive early data in Phase 2 clinical development in more than 230 patients across solid tumors and hematological malignancies, showing correlation between clinical efficacy and induced immunogenicity and a benign safety profile, activating large quantities of endogenous memory T-cells. For more information, please contact: ENTEROMEINVESTOR & MEDIA RELATIONSPierre BelichardChief Executive Officer +33 (0)1 75 77 27 85communication@enterome.com Cohesion BureauGiovanni Ca’Zorzi / Douwe Miedema +33 (0)7 84 67 07 27 / +352 621 562 764enterome@cohesionbureau.com Attachment 20251209 - Enterome PR ASH posters (final)

New data from cohort 3 show EO2463 can be safely added to rituximab in first-line low-tumor-burden follicular lymphoma in need of treatmentAll six patients responded positively to the combination Overall response data in cohort 2 confirm EO2463 monotherapy produces marked efficacy in patients in watch-and-wait settingRegistrational Phase 3 trial could start in 2026 in the watch-and-wait setting Paris, France – 13 NOVEMBER 2025 (08:30 CET)Enterome, a clinical-stage company pioneering OncoMimics™, a new class of off-the-shelf, multi-targeted in vivo immune therapies that induce a fast and potent expansion of memory T-cells to fight cancer, today announced positive new interim data from two cohorts of patients with low tumor-burden follicular lymphoma in the ongoing Phase 2 study of its lead OncoMimics™ immunotherapy EO2463. In cohort 3, data from the SIDNEY study showed a benign safety profile for EO2463 in combination with rituximab as first-line treatment for previously untreated patients with low tumor-burden follicular lymphoma in need of treatment, adding only injection site reactions to the well-known safety profile of rituximab. In addition, all six patients in this feasibility assessment responded to the combination treatment. Data from cohort 2 continue to show that EO2463 monotherapy produces excellent response rates when offered to patients with newly diagnosed follicular lymphoma or marginal zone lymphoma as an alternative to standard watchful waiting, an unmet clinical need setting. Per the abstract, data from 19 evaluable patients as of July showed an overall response rate (ORR) of 47%, including 3 complete responses (CRs) and 6 partial responses (PRs). No treatment is given to patients who currently follow the standard watch and wait setting practice as long as they do not show troublesome symptoms, despite the fact that they can remain anxious about their disease, and have a decreased quality of life. The company will present the next update on both sets of data at the 67th American Society of Hematology (ASH) meeting in Orlando, Florida, in December. “These encouraging data further strengthen our conviction in the broad potential of EO2463 as a novel active immunotherapy. The data from the “watch-and-wait” setting confirm our earlier positive findings, while those from cohort 3 – which we had not reported on before – point in the same direction,” said Jan Fagerberg, Chief Medical Officer at Enterome. “This is another exciting set of new data, ahead of our lead asset EO2463 entering Phase 3 testing in the “watch-and-wait” setting in 2026. The data come shortly after we received Fast Track designation for EO2463 from the U.S. FDA for the watch-and-wait setting, raising our confidence that Enterome’s OncoMimics™ platform has the potential to be applied across a broad range of cancers,” said Pierre Belichard, Chief Executive Officer of Enterome. Details of the poster presentations:Abstract #5377 Title: EO2463 (EO) peptide immunotherapy in patients (pts) with newly diagnosed asymptomatic follicular lymphoma (FL) and marginal zone lymphoma (MZL): Study EONHL1-20/SIDNEY (NCT04669171) primary endpoint Lugano objective response analysisPresenting Author: Jose Caetano (JC) Villasboas, MD Mayo ClinicSession: 623. Mantle Cell, Follicular, Waldenstrom's, and Other Indolent B Cell Lymphomas: Clinical and Epidemiological: Poster IIISession date: 7 December 2025Presentation time: 06:00-08:00 PMLocation: Room OCCC, West Halls B3-B4 Abstract #3594 Title: EO2463 (EO) peptide immunotherapy combined with rituximab (R) for first-line treatment of low-tumor burden follicular lymphoma (FL): A feasibility evaluation in Study EONHL1-20/SIDNEY (NCT04669171)Presenting Author: Stephen Smith, M.D., UW Medicine, Fred Hutchinson Cancer Research CenterSession: 623. Mantle Cell, Follicular, Waldenstrom’s, and Other Indolent B Cell Lymphomas: Clinical and EpidemiologicalSession date: 8 December 2025Presentation time: 06:00-8:00 PMLocation: Room OCCC, West Halls B3-B4 Follicular Lymphoma, one of several types of indolent Non-Hodgkin Lymphoma, is a difficult to treat chronic condition with relapses, characterized by slow progression and few symptoms, and reduced life expectancy. It is usually diagnosed by the appearance of swollen lymph nodes, and the early stages of the disease can be characterized by a lack of troublesome symptoms such as night sweats, fever or weight loss. There is a widespread consensus among leading investigators on the need for a well-tolerated and effective monotherapy to stop or slow progression for patients in the watch-and-wait setting. EO2463 is an innovative, off-the-shelf OncoMimics™ active immunotherapy that combines four synthetic peptides. These non-self, microbial-derived peptides correspond to CD8 HLA-A2 epitopes that exhibit molecular mimicry with the B lymphocyte-specific lineage markers CD20, CD22, CD37, and CD268 (BAFF receptor). It also includes the helper peptide (CD4+ epitope) universal cancer peptide 2 (UCP2). The unique ability of EO2463 to selectively target multiple B cell markers enables the destruction of malignant B lymphocytes. By ensuring broad target coverage across malignant B cells, this novel approach aims to simultaneously improve safety and maximize efficacy, reducing the tumor cells’ capacity to develop immune-resistance mechanisms such as antigen escape. OncoMimics™ consist of bacteria-derived peptide antigens that closely mimic tumor-associated antigens (TAAs). These antigens induce a fast and potent in vivo expansion of cytotoxic memory CD8+ T cells that were primed by gut bacteria, and are cross-reactive with TAAs. Because the peptides are “non-self”, OncoMimics™ avoid the self-tolerance that limits many cancer immunotherapies to enable rapid, potent, and durable responses to tumors. The synthetically produced peptides are designed in silico, mining Enterome’s proprietary database of 23 million commensal bacteria genes. Each product combines multiple high-affinity peptides to broaden target coverage and mitigate tumor heterogeneity. OncoMimics™ are easy to manufacture, store, distribute and administer as an “off-the-shelf” subcutaneous injection. OncoMimics™ have achieved rapid and potent responses in clinical testing in over 230 patients to date, with a benign safety profile. Enterome SA (www.enterome.com) is a privately held clinical-stage biopharmaceutical company developing OncoMimics™, a breakthrough in in vivo immune therapies for cancer. The three most advanced product candidates have shown positive early data in Phase 2 clinical development in more than 230 patients across solid tumors and hematological malignancies, showing correlation between clinical efficacy and induced immunogenicity and a benign safety profile, activating large quantities of endogenous memory T-cells. For more information, please contact: ENTEROMEINVESTOR & MEDIA RELATIONSPierre BelichardChief Executive Officer +33 (0)1 75 77 27 85communication@enterome.com Cohesion BureauChris Maggos / Giovanni Ca’Zorzi +41 (0)79 367 6254 / +33 (0)7 84 67 07 27enterome@cohesionbureau.com Attachment 20251113 - Enterome PR ASH teaser (final)