Full renewal of the Board of Directors
Election of Dr. Markus Cappel as Chairman of the Board of Directors

Nantes, September 30, 2025, 7:30 p.m. CET – OSE Immunotherapeutics (ISIN: FR0012127173; Mnemonic: OSE) held its Annual General Meeting today in Paris and welcomed the participation of shareholders in this key moment for the company’s future. The shareholders who voted on the resolutions represented approximately 56% of OSE’s share capital and more than 62% of the voting rights.

During this General Meeting, shareholders notably voted in favor of the appointment of the following directors:

• Caroline Mary, as representative of employee shareholders.
• Pascale Briand, Markus Cappel, Jonathan Cool, Marc Le Bozec, Shihong Nicolaou

and Alexis Peyroles.

Following the General Meeting, the new Board of Directors held its first meeting and elected Dr. Markus Cappel as Chairman.

"I am truly honored and enthusiastic to join OSE Immunotherapeutics' Board of Directors as Chairman. I look forward to working closely with the new Board and the talented OSE team to advance their promising pipeline and bring exciting, novel medicines to patients in need," said Dr. Markus Cappel, Chairman of the Board.

“The excitement around OSE Immunotherapeutics stems from its strong pipeline of innovative, first-in-class drug candidates, its positive clinical trial results, and its ability to forge strategic partnerships with global pharmaceutical leaders, all of which position the company as a key player in the evolving landscape of immunotherapy.”

OSE Immunotherapeutics extends its deepest gratitude to the outgoing members of the Board of Directors for their dedicated service. The Company is profoundly thankful for their time, expertise, and invaluable contributions and wishes them all the best in their future endeavors.

The Board confirms its confidence in OSE’s employees and their commitment to continuing the development of novel medicines.

Biographical highlights on Dr. Markus Cappel:

Dr. Markus Cappel has over thirty years of experience in the biotechnology sector. He is widely recognized for his entrepreneurial spirit and for his outstanding achievements.

As Chief Business Officer of ChemoCentryx, he led product development and key initiatives supporting the commercialization of TAVNEOS® across seven market countries. He also led multi-party negotiations with major pharmaceutical companies, securing agreements that preserved commercial rights and development control in the United States.

He played a pivotal role in the acquisition of ChemoCentryx by Amgen for $4 billion, representing a 116% premium, after having raised $435 million at the IPO, $138 million through private equity fundraising, and over $250 million in non-dilutive financing.

Prior to ChemoCentryx, Dr. Cappel served as Vice-President of Business Development at Advanced Inhalation Research (AIR), where he negotiated an exclusive agreement with Eli Lilly and built a strategic alliance with GlaxoSmithKline, securing an upfront payment of $125 million.

Dr. Cappel holds an MBA from Harvard Business School and a PhD in Pharmaceutical Sciences from J.W. Goethe University in Germany.

Full results are available on the Company website:

The full results of the votes from the Combined General Meeting are available on the Company’s website, under the Investors/General Meeting section: https://www.ose-immuno.com/assemblees-generales/

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.

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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.

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, 2025, including the annual financial report for the fiscal year 2024, 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.

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