Update on Information Relating to the General Meeting of September 30, 2025

Core Points - A shareholders' agreement has been executed by 61 founding, historical, employee, and executive shareholders of OSE Immunotherapeutics, representing approximately 20.1% of voting rights, concerning the vote on resolutions for the Board of Directors at the general meeting scheduled for September 30, 2025 [1][2]. Group 1: Shareholders' Agreement - The Shareholders' Group holds approximately 15.7% of the share capital and approximately 20.1% of the voting rights of the Company [2]. - The Shareholders' Group has committed to vote in favor of the Board of Directors' proposed resolutions regarding its own composition and against the resolutions proposed by minority shareholders [3]. Group 2: General Meeting Participation - Shareholders can participate in the General Meeting either in person, by mail, online via VOTACCESS, or by granting proxy to the Chairman or another person of their choice [4][8]. - For any proxy granted without naming a proxyholder, the Chairman will vote in favor of the Board's resolutions and against all other resolutions [4]. Group 3: Company Overview - OSE Immunotherapeutics is a biotech company focused on developing first-in-class assets in immuno-oncology and immuno-inflammation, partnering with leading academic institutions and biopharmaceutical companies [6].