CTLA4

Immuno-Oncology Results from Research Collaboration with Léon Bérard Cancer Center Presented at AACR Annual Meeting 2025 New gene expression signature for cancer patients to predict clinical response to immune checkpoint. Potential of signature to enhance personalized treatment for patients, regardless of cancer type. NANTES, France – April 30, 2025, 7:30 a.m. CET - OSE Immunotherapeutics SA (ISIN: FR0012127173; Mnemo: OSE), a biotech company dedicated to developing first-in-class therapies in immuno-oncology and immuno-inflammation, today reported on an oral presentation from a research collaboration with the renowned Léon Bérard Cancer Center in Lyon at the American Association for Cancer Research (AACR) Annual Meeting held April 25 – 30, 2025, in Chicago. Immune checkpoint blockade (ICB) therapies, targeting PD-1, PD-L1, and CTLA-4, have revolutionized cancer treatment by helping the immune system recognize and attack cancer cells more effectively. These therapies offer lasting responses and significant survival benefits across various cancers. However, current biomarkers like PD-L1 expression and tumor mutational burden (TMB) are not always reliable. PD-L1 expression can vary within tumors and between patients, making predictions inconsistent. Therefore, more universally applicable biomarkers are needed to predict patient responses and guide treatment decisions. While RNA sequencing has created detailed gene expression signatures (GES) that describe the tumor environment, their use in everyday clinical practice is limited due to their specificity and lack of widespread adoption. The presentation, entitled “A tumor agnostic composite gene expression signature identifies three groups of patients treated with immune checkpoint blockade with distinct clinical outcome”, reported on the development and validation of a robust and tumor-agnostic composite gene expression signature (cGES) that can predict overall survival and progression free survival in cancer patients treated with immune checkpoint blockers (e.g. Anti PD-L1, Anti PD-1 and Anti CTLA-4). This signature could be useful in clinical practice to better stratify patients on risk and potentially guide treatment decisions of multiple cancer types. Professor Pierre Saintigny of Université Claude Bernard Lyon 1, Centre Léon Bérard Comprehensive Cancer Center and Team leader Inserm/Inria at Cancer Research Centre of Lyon stated: “Our collaborative research program validated a composite gene expression signature with a strong potential for stratifying and predicting clinical outcomes more accurately, which could significantly improve personalized treatment in clinical practice for ICB-treated patients, regardless of cancer type. We were very pleased to present the results of our translational research at the AACR conference on this cutting-edge program conducted in collaboration with OSE Immunotherapeutics’ teams.” ABOUT THE LÉON BÉRARD CENTERThe Centre Léon Bérard (CLB) is part of the twenty French Comprehensive Cancer Centres in France, providing a global management of cancer patients on a unique area, from diagnosis to treatment and beyond. The Centre is a regional, national and international recognized reference cancer Centre assigned with three essential missions: Care, Research and Education and is willing to continuously improve the quality and accessibility of care for cancer patients. ABOUT OSE IMMUNOTHERAPEUTICS OSE Immunotherapeutics is a biotech company dedicated to developing first-in-class assets in immuno-oncology (IO) and immuno-inflammation (I&I) that address the unmet patient needs of today and tomorrow. We partner with leading academic institutions and biopharmaceutical companies in our efforts to develop and bring to the market transformative medicines for people with serious diseases. OSE Immunotherapeutics is based between Nantes and Paris and is quoted on Euronext. Additional information about OSE Immunotherapeutics assets is available on the Company’s website: www.ose-immuno.com. Follow us on LinkedIn. Contacts Fiona Olivierfiona.olivier@ose-immuno.comSylvie Détrysylvie.detry@ose-immuno.comFrench Media Contact FP2COMFlorence Portejoiefportejoie@fp2com.fr+33 6 07 768 283U.S. Media ContactRooney Partners LLCKate Barrettekbarrette@rooneypartners.com+1 212 223 0561 Forward-looking statementsThis press release contains express or implied information and statements that might be deemed forward-looking information and statements in respect of OSE Immunotherapeutics. They do not constitute historical facts. These information and statements include financial projections that are based upon certain assumptions and assessments made by OSE Immunotherapeutics’ management considering its experience and its perception of historical trends, current economic and industry conditions, expected future developments and other factors they believe to be appropriate. These forward-looking statements include statements typically using conditional and containing verbs such as “expect”, “anticipate”, “believe”, “target”, “plan”, or “estimate”, their declensions and conjugations and words of similar import. Although the OSE Immunotherapeutics management believes that the forward-looking statements and information are reasonable, the OSE Immunotherapeutics’ shareholders and other investors are cautioned that the completion of such expectations is by nature subject to various risks, known or not, and uncertainties which are difficult to predict and generally beyond the control of OSE Immunotherapeutics. These risks could cause actual results and developments to differ materially from those expressed in or implied or projected by the forward-looking statements. These risks include those discussed or identified in the public filings made by OSE Immunotherapeutics with the AMF. Such forward-looking statements are not guarantees of future performance. This press release includes only summary information and should be read with the OSE Immunotherapeutics Universal Registration Document filed with the AMF on April 30, 2024, including the annual financial report for the fiscal year 2023, available on the OSE Immunotherapeutics’ website. Other than as required by applicable law, OSE Immunotherapeutics issues this press release at the date hereof and does not undertake any obligation to update or revise the forward-looking information or statements. Attachment EN_250430_AACR_Oral presentation

Mesothelioma is a type of cancer that develops in the lining that covers the outer surface of some of the body’s organs and is usually linked to asbestos exposure. Image credit: Shutterstock / Wirestock Creators. GSK’s Zejula (niraparib) has reduced the risk of death or progression by 27% in patients with mesothelioma in an investigator-led Phase II trial. The NERO study (NCT05455424) investigated the efficacy of Zejula in 88 mesothelioma patients who relapsed after previously receiving platinum-based systemic therapy. The study is sponsored by the University Hospital Southampton NHS Foundation Trust and funded by Asthma + Lung UK, with support from Mesothelioma UK and the Mavis Nye Foundation. Mesothelioma is a highly aggressive cancer that forms in the protective lining surrounding certain internal organs, most commonly the lungs, and is usually linked to asbestos exposure. Treatments are limited, and the standard of care (SOC) includes surgery, chemotherapy, radiation therapy, and immunotherapy. Those treated with Zejula benefited from an average of 1.5 months progression-free survival (PFS) compared to SOC – marking a 27% reduction in the risk of the cancer progressing or death. Professor Gareth Griffiths, director of the Southampton Clinical Trials Unit and co-lead of the trial, said: “Although this increase may seem small, for this group of patients who have very few treatment options and a generally poor prognosis, this is a significant step forward. GlobalData Strategic Intelligence US Tariffs are shifting - will you react or anticipate? Don’t let policy changes catch you off guard. Stay proactive with real-time data and expert analysis. By GlobalData Learn more about Strategic Intelligence “We have shown for the first time that this kind of drug can improve progression-free survival for mesothelioma patients compared with their usual treatment in the NHS. This gives enormous hope to those patients and their families and means we can now carry out further research to find out more about how these treatments could be tailored and enhanced to stimulate an even better response in more people.” The data was presented at the American Association of Cancer Research (AACR) Annual Meeting 2025 in Chicago, US, on 29 April. The University Hospital Southampton NHS Foundation Trust is now keen to initiate a new study, SELECTmeso, which will be a Phase II platform trial in patients with confirmed histological diagnosis of mesothelioma with evidence of MTAP loss on immunohistochemistry, and evidence of disease progression following prior standard systemic therapy on CT scan. Griffiths added: “This trial will see patients tested for certain biomarkers, or genetic signals, in their tumours and then given the drug that is most likely to work for them. We really hope this step into more personalised medicine could further help these patients who desperately need better treatment options.” Other PARP inhibitors being investigated in mesothelioma Zejula is an oral poly-ADP ribose polymerase (PARP) inhibitor that was approved on 27 March 2017 by the US Food and Drug Administration (FDA) for the maintenance treatment of adult patients with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer. Other PARP inhibitors being investigated in patients with mesothelioma include AstraZeneca’s Lynparza (olaparib), which is currently in a Phase II trial (NCT04515836); and Pfizer’s Talzenna (talazoparib), which is also in a Phase II study (NCT04462809). AstraZeneca is also studying volrustomig , a bispecific antibody immunotherapy that targets and blocks PD-1 and CTLA-4. The drug is currently being evaluated in a Phase III trial for malignant pleural mesothelioma (NCT06097728). In September 2024, the FDA approved MSD’s Keytruda in combination with chemotherapy as a treatment for unresectable advanced or metastatic malignant pleural mesothelioma, based on data from the KEYNOTE-483 (NCT02784171) study.

MEDIA RELEASE Agreement offers rights to commercialize proposed biosimilar of Yervoy®* for treatment of variety of cancer types, targeting net reference medicine sales of USD 2.5 billion[1]Henlius to develop and manufacture biosimilar, with Sandoz to register and commercialize after expiry of relevant patents across global marketsCombination therapy of ipilimumab and nivolumab used in 95% of eligible patients[2]; ipilimumab highly complementary to proposed Sandoz nivolumab biosimilarPotential to address considerable unmet medical needs and increase worldwide access; reinforces Sandoz commitment to expand patient access and drive sustainable savings for healthcare systems Basel, April 29, 2025 – Sandoz (SIX:SDZ/OTCQX:SDZNY), the global leader in generic and biosimilar medicines, announced today that it has signed a global collaboration agreement with Shanghai Henlius Biotech, Inc. (Henlius, HKEX:02696) to commercialize a biosimilar of leading oncology therapy, ipilimumab. The agreement is milestone-based for a total consideration of up to USD 301 million, including an upfront payment of USD 31 million, and will target net reference-medicine sales of USD 2.5 billion[1]. Under the terms of the agreement, Sandoz has exclusive commercial rights for a biosimilar of ipilimumab in Australia, Canada, Europe, Japan and the US. The core sequence patent for ipilimumab expired in March 2025 in the US and will expire no later than February 2026 in the EU. Richard Saynor, CEO of Sandoz, said: “The global burden of cancer continues to grow and the potential to address unmet patient needs has never been greater.[3] This agreement offers us the chance to reach many more millions of patients, while helping to drive the long-term sustainability of healthcare systems.” The reference medicine, ipilimumab, is a monoclonal (CTLA-4) antibody-blocking medication, which is used alone or with other medicines to treat certain types of colorectal cancer, esophageal cancer, hepatocellular carcinoma (a type of liver cancer), malignant pleural mesothelioma, melanoma, non-small cell lung cancer, and renal cell carcinoma (a type of kidney cancer).[4,5,6] Henlius is developing its own proposed biosimilar of ipilimumab in an integrated Phase I/III trial in the unresectable hepatocellular carcinoma setting, targeting 656 patients to be enrolled (NCT06841185). Sandoz is developing its own proposed biosimilar of nivolumab in an integrated Phase I/III trial in the advanced melanoma setting, targeting 720 patients to be enrolled (NCT06587451). The reference medicine, nivolumab, (Opdivo®**) is a monoclonal (PD-1) antibody-blocking medication, which is used alone or with other medicines to treat more than 10 different cancer types. In combination with ipilimumab, nivolumab is indicated for the treatment of melanoma, malignant pleural mesothelioma, renal cell carcinoma, certain types of colorectal cancer, esophageal cancer, non-small cell lung cancer and hepatocellular carcinoma.[7,8] Sandoz is the leading biosimilar provider globally and has recently moved up to third position in the US, with a strategic ambition to occupy the leading position in that market.[9] The Company’s industry-leading biosimilars pipeline comprises 28 molecules, complemented by around 450 generic pipeline medicines to support its goal of sustainable and broadly-based long-term growth. The marketed biosimilar oncology portfolio includes Rixathon®, Zarzio®, Ziextenzo®, and Binocrit®. This year, Sandoz expects to launch its biosimilars Wyost®/Jubbonti® (denosumab) in the US in the second quarter and in Europe in the fourth quarter. * Yervoy® is a registered trademark of Bristol-Myers Squibb (US)** Opdivo® is a registered trademark of Bristol-Myers Squibb (US) DISCLAIMERThis Media Release contains forward-looking statements, which offer no guarantee with regard to future performance. These statements are made on the basis of management’s views and assumptions regarding future events and business performance at the time the statements are made. They are subject to risks and uncertainties including, but not confined to, future global economic conditions, exchange rates, legal provisions, market conditions, activities by competitors and other factors outside of the control of Sandoz. Should one or more of these risks or uncertainties materialize or should underlying assumptions prove incorrect, actual outcomes may vary materially from those forecasted or expected. Each forward-looking statement speaks only as of the date of the particular statement, and Sandoz undertakes no obligation to publicly revise any forward-looking statements, except as required by law. REFERENCES1. Loss-of-exclusivity (LoE) dates based on IP databases; originator-sales data at LoE-1 from internal analysis and Evaluate Pharma [November 2024]2. Decisions Resource Group (DRG) database of total treated population with Yervoy® (G7 markets) [accessed April 2025]3. Cancer Today [accessed March 2025]4. Yervoy® US Prescribing Information [accessed March 2025]5. Yervoy® EMEA Summary of Product Characteristics [accessed March 2025]6. Definition of Yervoy® - NCI Dictionary of Cancer Terms - NCI [accessed March 2025]7. Opdivo® US: Prescribing Information [accessed March 2025]8. Opdivo® EMEA Summary of Product Characteristics [accessed March 2025]9. IQVIA [download February 2025] ABOUT SANDOZSandoz (SIX: SDZ; OTCQX: SDZNY) is the global leader in generic and biosimilar medicines, with a growth strategy driven by its Purpose: pioneering access for patients. More than 20,000 people of 100 nationalities work together to ensure 900 million patient treatments are provided by Sandoz, generating substantial global healthcare savings and an even larger social impact. Its leading portfolio of approximately 1,300 products addresses diseases from the common cold to cancer. Headquartered in Basel, Switzerland, Sandoz traces its heritage back to 1886. Its history of breakthroughs includes Calcium Sandoz in 1929, the world’s first oral penicillin in 1951, and the world’s first biosimilar in 2006. In 2024, Sandoz recorded net sales of USD 10.4 billion. CONTACTS Global Media RelationsInvestor RelationsGlobal.MediaRelations@sandoz.comInvestor.Relations@sandoz.comAlex Kalomparis+41 79 279 0285Craig Marks+44 7818 942 383Joerg E. Allgaeuer+49 171 838 4838Rupreet Sandhu+41 79 410 5472 Attachment Media release_collaboration license agreement