OSE Immunotherapeutics Acknowledges The Decision Of The Nantes Commercial Court

NANTES, France – September 23, 2025, 10:30 p.m. CET – OSE Immunotherapeutics SA (ISIN: FR0012127173; Mnemo: OSE) acknowledges the decision rendered on September 23, 2025, by the Nantes Commercial Court rejecting its claims in the proceedings concerning the declaration of concerted action by a group of minority shareholders.

In the best interests of the Company, in order to focus on the execution of its strategy and to allow the General Meeting on September 30 to proceed as planned, the Board of Directors has decided not to appeal this decision. The Board nonetheless reaffirms its conviction regarding the merits of the principles defended in this action.

As part of the preparation for the General Meeting, the Board of Directors identified a material error affecting the calculation of voting rights, related to the acceleration of the vesting period for free shares. Contrary to the false allegations communicated by the group of minority shareholders, this processing error-corrected and regularized by the Board of Directors this evening-did not result from any attempt at fraudulent conduct by the Board, but from an inaccurate legal qualification by one of the Company's corporate advisors. A corrective press release will be published as soon as possible.

OSE Immunotherapeutics remains fully committed to ensuring the proper conduct of the General Meeting on September 30, 2025, in a spirit of transparency, responsibility, and respect for the rights of all shareholders.

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: .

Follow us on LinkedIn.

Contacts

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.

Attachment

• EN_250923_Decision_Court_FINAL

MENAFN23092025004107003653ID1110101787