Résumé de Article 083 EPC pour la décision T0709/23 du 17.06.2025

In T 709/23 the board explained that claim 1 was drafted as a purpose-limited product claim under Art. 54(5) EPC. The therapeutic indication "for use in treating a pruritic or allergic condition in cats" constituted a functional technical feature of the claim. The antibody was defined solely by two functional features: its specific binding to feline IL-31 and its inhibition of IL-31-mediated pSTAT signalling. However, the board noted that defining the antibody in terms of functional features did not, in itself, establish a credible link to the claimed therapeutic indication. The application as filed had to provide clear and direct disclosure demonstrating that the functionally defined antibody was indeed suitable for achieving the claimed therapeutic effect. The board observed that, while the extrapolation of the therapeutic effect from dogs to cats was disputed, its assessment under Art. 83 EPC was based on the objection that the claimed invention could not be carried out across the entire scope claimed. Accordingly, it was not necessary for the board to decide whether the skilled person would have credibly extrapolated the data on IL-31 in dogs to cats. The board explained that while the patent application showed that feline IL-31 could activate pSTAT in canine DH-82 cells, it did not demonstrate that antibody 11E12 or 34D03 inhibited IL-31-mediated pSTAT signalling in feline cells or was effective in treating pruritic or allergic conditions in cats in vivo. A person skilled in the art attempting to carry out the invention in cats as claimed, would have selected one of the few antibodies disclosed, which were described as binding to an epitope conserved between canine and feline IL-31 and felinised it as disclosed for antibody 34D03 in Example 11. The skilled person would have expected that each of the disclosed antibodies, i.e. both 11E12 and 34D03, would be capable of achieving the claimed effect in cats. Whether the approach would have worked with antibody 34D03 remained speculative. However, in post-published document D51, an in vivo effect in cats was demonstrated only for antibody 15H05, which binds to a distinct epitope on IL-31. Contrary to the central teaching of the patent application that inhibition of feline IL-31- mediated pSTAT signalling correlated with therapeutic efficacy in vivo, the data generated in D51 using 11E12 antibody variants showed that an antibody targeting the conserved antigenic region on IL-31 according to the patent application, while being able to inhibit feline IL-31- mediated pSTAT signalling in cat cells, failed to achieve significant therapeutic effects in cats. The board found that, as shown by document D51, additional research was necessary to arrive at an anti-IL-31 antibody capable of treating a pruritic or allergic condition in cats. Hence, there were serious doubts substantiated by verifiable facts whether, following the teaching of the patent application, a skilled person would arrive without undue burden at an antibody suitable for treating a pruritic or allergic condition in cats. The board concluded that the patent application did not disclose the invention as defined in claim 1 of the main request in a manner sufficiently clear and complete for it to be carried out by the person skilled in the art (Art. 83 EPC). The reasons provided for the invention according to claim 1 of the main request applied mutatis mutandis to the invention according to claim 1 of auxiliary requests 1 to 20 which also failed to fulfil the requirements of Art. 83 EPC.