UPC: The advent of file wrapper estoppel?

In two recent decisions before the UPC (UPC_CoA_402/2024, UPC_CoA_405/2024), the Court of Appeal rejected an appeal by Alexion Pharmaceuticals requesting grant of an application for provisional measures against Amgen and Samsung Bioepis in view of suspected infringement of their European patent. The patent in suit claims an antibody and pharmaceutical composition thereof suitable for use in the treatment of paroxysmal nocturnal hemoglobinuria. In particular, Claim 1 of the patent reads: “An antibody that binds C5 comprising a heavy chain consisting of SEQ ID NO: 2 and a light chain consisting of SEQ ID NO: 4”.

The central point of contention in proceedings before the EPO and UPC relates to the interpretation of the sequence of amino acids disclosed as SEQ ID NO: 4. Although the patent discloses SEQ ID NO: 4 under the heading of “Eculizumab Light Chain”, the sequence reproduced in the description in fact contains an extra 22 amino acids at the beginning of its sequence which are not present in eculizumab. An attempt by Alexion to amend the claims to exclude these 22 amino acids was denied on added matter grounds.

During prosecution, Alexion argued that the skilled person would interpret SEQ ID NO: 4 with the first 22 amino acids present, but that one skilled in the art would understand the sections of the sequence that would function in the manner required by the invention. Alexion abandoned this argument at UPC first instance proceedings, and argued instead that the skilled person would interpret SEQ ID NO: 4 without the first 22 amino acids as the overall sequence disclosed was in fact not functional. Expert evidence presented to the court agreed that a sequence including these extra amino acids would be “highly likely” not to function in the manner required by the invention.

On appeal, the COA considered that the view taken before the UPC Court of First Instance ignored the fact that a patent claim must be interpreted from the perspective of a person skilled in the art. The arguments initially submitted by Alexion during grant proceedings, that the person skilled in the art would interpret SEQ ID NO: 4 with the first 22 amino acids present, were held to be an indication of the view of the skilled person at the filing date and were consequently relied upon by the COA.  

Reliance on statements made during prosecution are exceptionally rare in European litigation. The fact that the prosecution history of the patent has been relied upon by the highest panel of the UPC suggests that there is a potential for a file wrapper estoppel to become part of the UPC’s practice.