In a recent decision, the UPC Court of Appeal ruled on the correction of errors in a patent by interpretation. This case, concerning Alexion Pharmaceuticals’ patent (EP3167888), underscores the importance of precise drafting and consistency in arguments used during patent litigation.
EP’888 was granted in May 2024 after an EPO ex parte appeal, containing two claims designed to cover the antibody eculizumab, marketed as Soliris®:
However, due to an error in SEQ ID NO: 4, eculizumab was not directly covered by the claims.
In March 2024 Alexion sought preliminary injunctions before the UPC against two manufacturers of eculizumab biosimilars (Amgen and Samsung-Bioepis), despite eculizumab not being literally covered by the granted claims. Meanwhile, an opposition was filed against EP’888 by Samsung-Bioepis in May 2024 (later followed by Amgen in October 2024). The application for the preliminary injunctions were heard by the UPC Local Division Hamburg in June 2024.
During pre-grant appeal proceedings the EPO Board of Appeal denied correction of the error in SEQ ID NO: 4 under Rule 139 EPC, as the error was not immediately evident to a skilled person. While acknowledging the possibility that the skilled person might “doubt that the depicted sequence was the sequence it purported to represent”, the Board held that such doubt was insufficient to meet the requirement that the error be immediately evident.
Despite this, when granting the patent the EPO Board of Appeal accepted that claims referencing the incorrect sequence were sufficient, on the premise that even an antibody with the incorrect sequence would still bind C5.
In a decision issued after the first EPO opposition had been filed, the UPC Local Division Hamburg acknowledged that infringement might be found because the skilled person would interpret the claims as covering the corrected sequence, i.e. that they would spot the error in SEQ ID NO: 4 and assume the correct sequence listing should be used.
However, the injunction was nonetheless denied based on the court’s belief that the patent would likely be found invalid by the EPO Opposition Division for lack of sufficiency. The court reasoned that the literally claimed antibody, with the incorrect SEQ ID NO: 4, could not bind C5 as required by the claims, a point which was admitted by Alexion during the UPC proceedings. This admission contradicted Alexion’s earlier arguments made during the pre-grant appeal proceedings at the EPO, and the court suggested that this admission might prompt the EPO to revisit the issue of sufficiency during the post-grant opposition procedure.
The court’s stance on validity seemingly conflicted with its own view on infringement. While it assumed the skilled person would use the correct sequence in assessing infringement, the court evaluated validity based on the incorrect sequence. They justified this inconsistency by stating that “the Court is not at all convinced that the Opposition Division of the EPO will share the opinion of the Court on the question of claim construction”. In other words, the court evaluated validity from the expected perspective of the EPO Opposition Division rather than adhering to its own interpretation of the claims.
The court suggested that following its interpretation of the claims the patent would likely be sufficient. However, it admitted the EPO would probably decide differently during the opposition proceedings. This conclusion was based partly on the fact that the arguments presented by Alexion before the UPC seemingly undermined the sole reason given by the EPO Board of Appeal in support of sufficiency in the pre-grant proceedings.
Effectively, the Local Division indicated that it would have ruled in favour of Alexion, but chose to defer to the expected outcome of the EPO’s opposition proceedings, reasoning that the EPO was likely to reach the opposite conclusion. This deferral to the anticipated EPO decision seems reasonable when deciding on a preliminary injunction, as such decisions require a reasonable certainty that the patent will survive the EPO’s post-grant opposition procedure. This is especially relevant here, given that Alexion’s arguments before the UPC undermined their own arguments previously used to convince the EPO to grant the patent.
In December 2024 the UPC Court of Appeal issued a decision disagreeing with the Local Division on claim interpretation, and siding with the EPO’s strict test under Rule 139 EPC. The test proposed by the Court of Appeal aligns closely with Rule 139 EPC:
“A linguistic error, a spelling mistake or any other inaccuracy in a patent claim can only be corrected by way of interpretation of the patent claim if the existence of an error and the precise way to correct it are sufficiently certain to the average skilled person on the basis of the patent claim, taking into account the description and the drawings and using common general knowledge.” – Headnote of the Court of Appeal decision
“Linguistic errors, errors of transcription and mistakes in any document filed with the European Patent Office may be corrected on request. However, if the request for such correction concerns the description, claims or drawings, the correction must be obvious in the sense that it is immediately evident that nothing else would have been intended than what is offered as the correction.” – Rule 139 EPC
The Court of Appeal found that the existence of an error in SEQ ID NO: 4 and its correction were “not sufficiently certain to the average skilled person”. In reaching this conclusion, the court used Alexion’s EPO arguments against them, reasoning that if an antibody with the incorrect sequence could still bind C5 (as Alexion had argued during the ex parte proceedings before the EPO), then no unequivocal error existed.
Having disagreed about the issue of claim interpretation, the Court of Appeal agreed with the Local Division that the patent was likely invalid, stating that “it is more likely than not that the subject matter of claim 2 is insufficiently disclosed within the meaning of Art. 83 EPC”.
By employing Alexion’s own arguments for sufficiency to reject the correction of the error and simultaneously using Alexion’s arguments made in support of the correction to suggest insufficient disclosure, the Court of Appeal has demonstrated the risks of parties assuming inconsistent positions between EPO and UPC proceedings.
Interestingly, the Court of Appeal chosen not to comment on infringement, but interpreting the claims as written (with the error) would suggest there would be no infringement. This reasoning might have provided a stronger basis for denying the injunction than reliance on the anticipated EPO decision. It remains to be seen if the eventual EPO decision will align with these expectations.
The UPC has, for now, aligned itself with the EPO on the test for correcting errors in a patent, a move that supports consistency between the EPO and UPC. However, this provides little comfort to Alexion or its drafting attorneys.
This decision highlights the importance of precise drafting and consistent arguments in patent litigation. Contradictions between positions taken in different forums can weaken a case, especially given the UPC’s readiness to reference EPO proceedings. An effective patent strategy requires clarity, precision, and alignment across all jurisdictions, especially between the EPO and UPC.