Open letter to the OSE Immunotherapeutics Shareholders

Dear OSE Immunotherapeutics Shareholders,

As co-founders and former directors of OSE Immunotherapeutics, we intimately understand the company’s innovations, their commercial potential, and the paths to success.

We remain major shareholders because we believe in the immense promise of what we created.

Though we entrusted the company’s leadership to others, their direction has proven misguided.

Now, we feel it is our responsibility to step in and realign OSE with a strategic, sustainable course.

Why Change Is Needed

The current board is pursuing an overly aggressive, debt-driven expansion through Venture debt funds, centered on Phase 2b clinical trials for Lusvertikimab

A high-risk approach in today’s biopharmaceutical climate. In particular for the employees of the company like what happened in the other French biotechs that followed the same dangerous path.

This strategy fails to consider the immense cost of large-scale trials, and the challenges of patient enrollment in the ulcerative colitis indication.

Instead, Lusvertikimab’s development should follow the proven path of securing strategic partners who can provide the financial and operational support needed to advance the program responsibly.

Our Plan for Sustainable Growth

Our resolutions prioritize a measured, value-driven strategy built on six pillars:

1. Prudent Cash Management – Ensuring financial stability through 2027 without risky debt or unnecessary dilution.
2. Strategic Resource Allocation – Supporting the right programs with the right resources while leveraging partnerships for costly initiatives.
3. Balanced Partnerships – Retaining ownership of programs we can finance independently, while partnering on those requiring larger-scale support.
4. Core Asset Strengthening – Advancing breakthrough products like Tedopi for lung cancer and Lusvertikimab, while fortifying existing and upcoming partnerships.
5. Innovation Preservation – Maintaining our R&D hub in Nantes, a vital center of first-in-class discoveries and non-dilutive funding.
6. Experienced Leadership – Assembling an internationally seasoned Board with expertise in biotech financing, licensing, and commercialization.

Securing a Strong Future

With your support, we can restore financial discipline, reinvigorate OSE’s innovative spirit, and drive sustainable growth—ultimately maximizing value for all shareholders, employees, and patients.

Together, we can set OSE Immunotherapeutics on the right path forward.