What we want

We believe that building a balanced portfolio of partnered and independent programs continues to be the best path forward for OSE.

We have built OSE’s strategy around two key pillars:

• Conducting high-performance research in immuno-oncology and immuno-inflammation.
• Developing multiple products in parallel, either in partnership with leading names in the pharmaceutical industry or independently depending on the indication, as appropriate.

Partnerships, especially licensing and co-development deals, provide upfront payments and milestone payments. This cash-flow allows OSE to fund its independent programs, such as Tepodi® without giving up additional equity, thus preserving shareholder value.

OSE would benefit tremendously from a pharma partnership to help finance Lusvertikimab’s late stage clinical development , as these studies in Ulcerative Colitis will involve up to 1,000 patients and entail an estimated total cost of €500 million. We can start seeking a pharma partner immediately, since the results published in early 2025 demonstrate Lusvertikimab’s effectiveness and safety in the target patient population.

As we have done for the past 12 years, we want OSE to make clear decisions based on the market potential and effectiveness of all its products, including those still in the R&D stage.

We also want OSE to communicate transparently about these decisions and the scientific results that support them.

This is essential to maintain the trust of all stakeholders — particularly current and future partners, shareholders employees, patients and the medical community.

We have a strategic disagreement with OSE’s Board of Directors.

The Board of Directors’ strategy for Lusvertikimab is to launch a Phase 2b study—costly and very lengthy—without an industrial partner, but with investment funds or debt funds that would then carry the program into Phase 3 with the objective of selling OSE, and that would, beforehand, require the company to focus solely on this product, to halt its other projects, and probably to scale back its R&D, if we refer to the example of other biotechs.

The Phase 2b study presented by OSE would require several subgroups in order to explore multiple avenues: assessment of two administration routes (intravenous and subcutaneous), a dose-ranging study with at least two doses, the use of a “predictive biomarker” (with some patients having this biomarker and others not), and, more traditionally, subgroups of patients who have already received biologic treatments and those who have not. We estimate that such a study would cost €60 to €80 million—far higher than the €30 to €50 million range announced by OSE on August 29, 2025.

Lusvertikimab is a treatment for ulcerative colitis, a condition for which several other therapies are under development at other biotechs and pharmaceutical companies. We therefore have a fairly precise idea of the overall cost of the necessary studies: €500 million. This figure is based on comparable market data.

This strategy would be highly risky, as it would force OSE to raise €500 million over several years and, immediately, €60 to €80 million for a Phase 2b study.

Raising such an amount when OSE’s market capitalization is around €140 million would be very difficult in the current financial context, where investors’ priorities lie elsewhere than in biotechs. It would be impossible through equity alone, not to mention the very significant dilution it would cause for shareholders. It would therefore require borrowing from funds that would demand high interest rates and guarantees over assets.

This strategy would also be very risky because it would result in concentrating all of OSE’s resources on a single product—indeed a standard requirement of investors—which would have a direct impact on the Nantes research center.

As OSE’s founding shareholders, we do not support this strategy.

On March 26, 2025, OSE published a press release presenting its 2024 results and outlining its strategy. This prompted many questions among the three of us.

We founded OSE, we know the company inside out, we collectively own 20% of its share capital, and we have known many of its Board members — in some cases, for years.

We therefore began by engaging in dialogue with the Board of Directors.

We held several meetings and exchanges in April and May, believing it would be possible to gently bring OSE back on track with the strategy that made it successful.

We proposed the appointment of three new directors to ensure our voices were heard, to reorient strategy, and to clarify communication:

• Alexis Peyroles, who from 2013 to early 2022 was one of OSE’s executives and later its CEO.
• Marc Le Bozec and Jonathan Cool, both with extensive experience in biotech development, financing, and partnerships with pharmaceutical companies.

We believed these three appointments would be sufficient.

These candidates went through the standard interview process with current Board members.

To our great surprise, the Board concluded that Alexis Peyroles and Marc Le Bozec could bring nothing to OSE. And that was not all.

On May 21, we discovered the full list of resolutions for the June General Meeting. Alongside the proposed appointment of Jonathan Cool, the Board also proposed appointing two new directors, increasing its size from nine to twelve members — further diluting Jonathan Cool’s now solitary voice.

We had to face the reality:

• The Board has no intention of listening to us.
• It has chosen the incoherent and risky strategy of conducting Lusvertikimab’s upcoming studies alone, without a partner.

We were left with only one option: to change the Board.

This was not a decision we took lightly — it was not our initial intention. On May 27, we signed a shareholders’ agreement forming a action in concert.

We sought dialogue. The same cannot be said of the Board of Directors.

• The Board rejected two of the three Board members we proposed — including Alexis Peyroles — on the surprising grounds that they would bring “nothing” to OSE.
• It asked for and obtained the postponement of the General Meeting from June 25 to September 30, and in the meantime initiated legal proceedings before the Nantes Commercial Court (hearing on September 8) to distort shareholder democracy and deprive us of nearly 60% of our voting rights.
• In June, Didier Hoch, Chairman of the Board, refused to meet with Markus Cappel and Jonathan Cool, two US-based nominees for director who had travelled to France to attend the General Meeting.

We nevertheless remained open to dialogue, which soon turned into a dialogue of the deaf—or even a monologue—when, in a communication dated August 25, the Board of Directors suggested that an agreement existed with us, an agreement that never existed. We were then compelled to state our firm opposition and to declare the end of the dialogue.

Here our Press release of September, 5

“The Board of Directors determines the company’s strategic direction and ensures its implementation.” – Article 22 of OSE’s bylaws.

The Board claims to value dialogue and transparency. By late May, it was clear that our meetings and exchanges had been fruitless.

We have a strategic disagreement with the current Board members, particularly regarding the clinical development of Lusvertikimab.

In our view, the Board’s strategy is incoherent and highly risky.

After 12 years serving as OSE’s CEO, Chair, and Director of Development & Strategy, we believe Lusvertikimab must move to Phase 3 and with a partner, given the estimated total cost of €500 million.

As founding shareholders holding 20% of the capital and 24% of the voting rights, our only option to bring OSE back to the strategy that made it successful is to change the Board.

This is why, at the General Meeting to be held on September 30, we are calling for the dismissal of the current directors and proposing six new director appointments, five of which had already been presented at the General Meeting initially scheduled for June 25.

The addition of a sixth nomination is intended to secure the future Board of Directors, since as a listed company, OSE is subject to obligations regarding gender representation among its directors. Any change in the current Board’s resolutions could jeopardize compliance with this obligation. These resolutions will be published on September 15.

Here our Press release of September, 5

We are also calling for votes against the renewal of expiring mandates, including that of Didier Hoch, Chairman of the Board of Directors.

We hereby present these resolutions, which have been officially filed, and for which we invite each shareholder to vote in favor