OSE Immunotherapeutics to Present a Novel, First-in-Class, FPR2 Agonist Monoclonal Antibody in the Resolution of Chronic Inflammation at the AAI 2026 Meeting

Nantes, France, April 15, 2026 – 7:30am CEST - OSE Immunotherapeutics SA (ISIN: FR0012127173; Mnemo: OSE), a clinical-stage biotech company dedicated to developing first-in-class therapiesin immuno-oncology and immuno-inflammation, today announced that an abstract on a novel agonist monoclonal antibody targeting FPR2, a key receptor involved in the triggering resolution of inflammation, has been selected for an oral presentation at the 2026 Annual Meeting of the American Association of Immunologists (AAI) in Boston, Massachusetts, United States (April 15-19, 2026).

Aurore Morello, PhD, Chief Scientific Officer of OSE Immunotherapeutics, will unveil for the first time a novel, first-in-class therapeutic strategy targeting the FPR2 G-protein–coupled receptor (GPCR). This approach aims to activate the body’s natural inflammation-resolution mechanisms for the treatment of chronic inflammatory diseases.

“Chronic inflammatory diseases are associated with significant unmet medical needs on a global scale, yet current treatments largely focus on long-term suppression of immune cells rather than restoration of physiological balance,” commented Dr. Aurore Morello, Chief Scientific Officer. “Our strategy targeting the FPR2 receptor reflects a deliberate shift toward resolution biology—an area with the potential to open new therapeutic opportunities and build differentiated, durable value in inflammation.”

“New FPR2 agonist decreases neutrophil accumulation and initiates chronic inflammation resolution”

• Oral Presentation
• Session: Cellular Adhesion, Migration and Inflammation (CAM)
• Location: 102
• April 17, 2026, 9.45-10.00 EST

Resolution of inflammation is an active process mediated by specialized receptors such as Formyl Peptide Receptor 2 (FPR2), a G-Protein Coupled Receptor (GPCR) expressed on neutrophils, monocytes and macrophages.

The first-in-class FPR2 specific agonist antibody developed by OSE introduces a novel strategy to switch off inflammation to actively trigger the resolution of inflammation by limiting neutrophils recruitment and reprogramming macrophages through pro-resolutive anti-inflammatory state. Its pro-resolutive agonist activity and robust preclinical efficacy in multiple inflammatory disease models leverage new opportunities for treating acute and chronic inflammatory disorders.

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 listed on Euronext. Additional information about OSE Immunotherapeutics assets is available on the Company’s website: www.ose-immuno.com. Follow us on LinkedIn.

Contacts

OSE Immunotherapeutics: investors@ose-immuno.com

FP2COM (Media Relations): Florence Portejoie: fportejoie@fp2com.fr I +33 6 07 768 283

LifeSci Advisors (Investor Relations): Guillaume van Renterghem: gvanrenterghem@lifesciadvisors.com I +41 76 735 01 31

Forward-looking statements

This 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.

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