OSE Immunotherapeutics Provides Update On Ongoing Proceedings Ahead Of Shareholders' Annual General Meeting Of September 30, 2025

NANTES, France, September 8, 2025, 6p.m. CET – OSE Immunotherapeutics SA (ISIN: FR0012127173; Mnemo: OSE) announces that, following today's hearing before the Nantes Commercial Court under the accelerated procedure (procédure dite“à bref délai”), the Court has taken under advisement the matter concerning the regularity of the declaration of the concerted action by a group of minority shareholders. The decision is expected on
September 23, 2025.

This procedure aims to safeguard the integrity of the voting process at the upcoming Annual General Meeting (AGM) on September 30, 2025. Its objective is to ensure that all shareholders can exercise their voting rights under fair, transparent, and informed conditions- fundamental principles of shareholder democracy. The Court's review focuses on the regularity of the concerted action declared in May 2025 by the group of minority shareholders.

OSE Immunotherapeutics remains firmly committed to defending the interests of the Company and all its shareholders and will publish any further updates on this matter as they become available.

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: Click and follow us on LinkedIn.

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Forward-looking statements
This press release contains express or implied information and statements that might be deemed forward-looking 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 can often be identified by the use of the conditional tense and by verbs such as“expect”,“anticipate”,“believe”,“target”,“plan”, or“estimate”, their declensions and conjugations as well as other similar terms. Although the management of OSE Immunotherapeutics believes that the forward-looking statements and information are reasonable, 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 within the AMF. Such forward-looking statements are not guarantees of future performance. This press release includes only summary information and should be read alongside OSE Immunotherapeutics Universal Registration Document filed with the AMF on April 30, 2025, including the annual financial report for the fiscal year 2024, available on OSE Immunotherapeutics' website. Other than as required by applicable laws, 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.

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