Ose Immunotherapeutics : Documents made available to the shareholders for the combined general meeting of June 25th, 2025

Documents made available to the shareholders for the combined general meeting of June 25^th, 2025

Nantes, June 4^th, 2025, 8 a.m. - OSE Immunotherapeutics SA (ISIN: FR0012127173; Mnemo: OSE) announces the publication of the preparatory documents for the combined general meeting to be held on June 25^th, 2025 at 10 a.m. at the Drawing House Hotel - 21, rue Vercingétorix - 75014 Paris.

The convening notice (avis de reunion valant avis de convocation) containing the agenda and the resolutions, as well as the conditions for attending and voting at this General Meeting, was published in the BALO on May 21^st, 2025 and the convening notice will be published in the BALO and in a legal gazette on June 6^th, 2025.

The preparatory documents required by Article R. 22-10-23 of the French Commercial Code are available on the Company's website: https://-immuno.com/assemblees-generales/.

In accordance with the applicable regulations:

• Registered shareholders may, up to and including the fifth calendar day before the General Meeting, ask the Company to send them the documents referred to in Articles R.225-81 and R.225-83 of the French Commercial Code, where applicable at their express request by electronic means. For shareholders in bearer form, the exercise of this right is subject to the provision of a certificate of participation in the accounts in bearer form held by the authorized intermediary.
• Any shareholder may consult the documents referred to in Articles L. 225-115 and R.225-83 of the French Commercial Code at the registered office of the Company (22, Boulevard Benoni Goullin - 44200 Nantes).

Context of the General Meeting and commitment of the Board of Directors

For several years, OSE has pursued a clear strategy aimed at creating sustainable value for all its shareholders. The Board of Directors ensures good governance, transparency of information and consistency of strategic decisions. It reiterates its commitment to balanced, independent governance focused on long-term value creation, in the interests of all shareholders.

In this context, the Board invites shareholders to consider carefully the implications of the resolutions put to the vote, in particular those that may affect the stability and continuity of the implementation of the Company's strategy.

For a better comprehension of the foundations and ambitions of the strategy pursued by the Board of Directors, shareholders are also invited to consult the press release published in parallel today, which sets out the Company's long-term objectives and outlook¹.

Competing resolutions proposed by a group of concerted shareholders

In accordance with applicable regulations, the convening brochure sets out all the resolutions put to the vote, including ten draft resolutions proposed by a group of shareholders acting in concert, declaring holding approximately 24% of the voting rights under the terms of a shareholders’ agreement published on June 3^rd, 2025 on the AMF website².

The Board of Directors emphasizes that the sole purpose of these resolutions is to reorganize the Board of Directors almost entirely. If adopted, these resolutions would be particularly destabilizing for the governance of the Company, and the Board of Directors considers that they are likely to undermine its stability and interrupt the implementation of its strategy, to the detriment of its attractiveness, credibility and development trajectory. They appear disproportionate in view of the context, the governance in place and the effective representation of the initiating group.

After careful consideration, the Board of Directors recommends voting against all the resolutions proposed by these shareholders. Detailed explanations and voting recommendations can be found in the convening brochure and in the communication to shareholders available on the company's website: https://-immuno.com/assemblees-generales/.

Respect of shareholder democracy and governance principles

The Company reaffirms its commitment to the proper functioning of the democratic process specific to general meetings, based on transparency, fairness between shareholders and respect for each shareholder's right to information.

The Board of Directors draws the attention of shareholders to the resolutions proposed by the group of shareholders acting in concert, whose shareholders' agreement was not made public on the French financial market authority (Autorité des marchés financiers) website until June 3^rd, 2025. At this stage, the elements made public are being carefully analyzed by the Company as to their completeness, timing and effective scope.

The Company remains fully committed to ensure that the General Meeting will be conducted in a fair and transparent manner, while respecting the rights of all shareholders and the interests of the Company. In this respect, the Company reserves the right to take any appropriate action, including regulatory or legal action, should circumstances so require.

The Board of Directors reiterates its commitment to balanced, independent governance focused on long-term value creation, in the interests of all shareholders.

The brochure also sets out the terms and conditions for participation, distance voting and proxy voting, in accordance with the applicable regulations.

For further information, shareholders are invited to consult the documents made available on the Company's website: -immuno.com/assemblees-generales/

ABOUT OSE IMMUNOTHERAPEUTICS

OSE Immunotherapeutics is a biotechnology company developing first-in-class products in immuno-oncology (IO) and immuno-inflammation (I&I) to address the unmet needs of today's and tomorrow's patients. We partner with leading academic institutions and biopharmaceutical companies to combine our efforts to develop and bring to market transformative medicines for people suffering from serious diseases. OSE Immunotherapeutics is based in Nantes and Paris and is listed on Euronext. More information on OSE Immunotherapeutics' assets is available on the Company's website: http:

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Forward-looking statements

This press release contains express or implied forward-looking information and statements about OSE Immunotherapeutics. They are not historical facts. Such information and statements include financial projections based on assumptions or suppositions made by the management of OSE Immunotherapeutics in light of their experience and perception of historical trends, current economic and industry conditions, future developments and other factors they deem relevant.

These forward-looking statements can often be identified by the use of the conditional tense and by the verbs "expects", "anticipates", "believes", "plans" or "estimates" and their declinations and conjugations, as well as by other similar terms.

Although OSE Immunotherapeutics' management believes that the expectations reflected in such forward-looking statements are reasonable, OSE Immunotherapeutics' shareholders and other investors are cautioned that the realization of such expectations is subject to numerous risks and uncertainties, known and unknown, that are difficult to predict and that are beyond OSE Immunotherapeutics' control. These risks could cause actual results and developments to differ materially from those expressed or implied in such forward-looking statements. These risks include, but are not limited to, 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 summary information only and should be read in conjunction with OSE Immunotherapeutics' Universal Registration Document, registered by the AMF on 30 April 2024, including the 2023 annual financial report, available on OSE Immunotherapeutics' website.

OSE Immunotherapeutics does not undertake any obligation to update any forward-looking information or statements at any particular time.

Except as required by applicable laws and regulations.

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