EPO upholds SOT201 patent for SOTIO's PD-1 immunocytokine
SOTIO Biotech has secured a significant intellectual property win after the Boards of Appeal of the European Patent Office upheld European Patent EP 3 444 271 B1, confirming protection for SOT201, its PD-1-targeting immunocytokine currently in Phase 1 testing. The decision came following oral proceedings held in early July and overturned a challenge that had been pursued, on appeal, by Sanofi.
The patent, co-owned by SOTIO's affiliate Cytune Pharma, the Parisian hospital group AP-HP and French research institute INSERM, covers immunocytokine constructs comprising interleukin-15 conjugated with the sushi domain of the IL-15 receptor alpha and an immunomodulatory antibody, specifically including PD-1 antagonists. Opposition proceedings were originally brought by both Sanofi and Strawman Limited before Sanofi alone pursued the subsequent appeal.
What SOT201 does
SOT201 is designed as a cis-acting, attenuated IL-15 agonist that preferentially activates PD-1-positive CD8-positive T cells, aiming to boost anti-tumour immune responses selectively at the site of disease. The candidate is under evaluation in the international VICTORIA-01 Phase 1 study, which enrols patients with advanced unresectable or metastatic solid tumours.
The company reported that the programme has generated what it describes as a high disease control rate, including objective responses in heavily pre-treated patients, though no specific response-rate figures or hazard ratios were disclosed in the announcement. Full clinical data have not yet been presented at a major medical congress.
Radek Spisek, chief executive of SOTIO, said: "The decision validates the strength of the underlying invention and reinforces the intellectual property supporting SOT201. Importantly, this milestone comes as the programme continues to generate encouraging clinical data."
Market context and competitive positioning
The immunocytokine field sits at the intersection of cytokine engineering and checkpoint biology, and has attracted growing investment from both large pharma and specialist biotechs. IL-15 agonism, in particular, is viewed as a promising alternative to the more widely explored IL-2 pathway, given IL-15's capacity to expand CD8-positive T cells without substantially expanding regulatory T cells, a limitation that has historically constrained IL-2-based approaches.
Sanofi's decision to oppose and then appeal the patent underlines the commercial interest major players are directing at this space, and the confirmed grant meaningfully narrows freedom-to-operate for competitors pursuing structurally similar IL-15-antibody conjugates in Europe. SOTIO's co-ownership structure, spanning a private biotech, a French academic hospital network and a national research institute, is a relatively unusual arrangement and may shape any future licensing or partnership conversations.
SOTIO, owned by Czech conglomerate PPF Group, is primarily known for its antibody-drug conjugate pipeline. SOT109, targeting CDH17 in colorectal cancer, received FDA Fast Track Designation in July 2026, while LRRC15-targeting SOT106 received Orphan Drug Designation in May 2026. SOT201 sits alongside these programmes as a distinct immunological approach rather than the company's flagship ADC strategy. Investors watching SOTIO will now focus on when VICTORIA-01 Phase 1 dose-escalation data will be presented and whether an optimal biological dose has been established, which would be the clearest signal of clinical viability ahead of any potential Phase 2 design.