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"[L]ife is too short" to consult the prosecution history when dealing with issues of claim interpretation. Those were the words of Lord Hoffmann in Kirin Amgen v Amgen [2005] RPC 9. And many believe that this sentiment has been representative of the attitude of courts in the UK and the rest of Europe to prosecution history estoppel for many years. This differs from the approach taken in other jurisdictions, such as the US, where recourse to the "file wrapper" is relatively common in the context of claim interpretation and infringement by equivalents. With the Unified Patent Court (UPC) being in its infancy, its position on prosecution history estoppel is still developing. As the law of the UPC is based on the law of its European member states, one might expect the UPC to reflect the typical European approach of avoiding reliance on prosecution history. But, so far, has this been the case?
The UPC Court of Appeal sets a new precedent
The leading authority on the relevance of the prosecution history at the UPC is the Court of Appeal order, Alexion v Samsung, UPC_CoA_402/2024 and 405/2024 (20 December 2024).
When interpreting a patent claim directed to an antibody defined by heavy and light chain amino acid sequences, the UPC Court of Appeal stated the following (which became a headnote for the order).
The patent claim must be interpreted from the perspective of the person skilled in the art. The applicant's assertions during the grant proceedings, and in particular the [EPO Technical Board of Appeal's] endorsement thereof, can be seen as an indication of the view of the person skilled in the art at the filing date.
So, in this case, the UPC Court of Appeal seems to have opened the door to use of the prosecution history by referring to the EPO Board of Appeal decision when interpreting the claim. This principle was restated by a different panel of the UPC Court of Appeal in Philips v Belkin, UPC_CoA_534/2024 and 19/2025 (3 October 2025). However, in that case, the parts of the prosecution history referred to by the defendant were considered not to provide any indication of the meaning of the relevant claim integer from the perspective of the skilled person.
Application in first instance decisions
UPC_CoA_402/2024 and 405/2024 has since been applied in two first instance decisions.
Occlutech v. Lepu Medical, UPC_CFI_630/2025 (31 October 2025) related to "[a]n occlusion device comprising a hub (5) and a braiding (2) of thin wires or threads (4)...". At EPO opposition, the patentee successfully argued that the occlusion device disclosed in the prior art consisted of only one wire, whereas the claimed device was an occlusion device comprising several wires or threads.
Citing UPC_CoA_402/2024 and 405/2024, the Düsseldorf Local Division held that the patentee's argument and its confirmation by the EPO opposition division was an indication that the skilled person would interpret the claim such that a mesh made of a single wire or thread does not fall within its scope. Consequently, the Düsseldorf Local Division held that the allegedly infringing product did not fall within the scope of the claim, because the patentee had not shown that the allegedly infringing product included more than a single wire or thread.
Raccords et Plastiques Nicoll v. First Plast, UPC_CFI_612/2024 (24 October 2025) related to a gutter having at least two spacer elements for abutting lining elements on either side (e.g. to space apart adjacent floor tiles). Claim 1 required the spacer elements to be aligned in an alignment direction and separated in that alignment direction by an opening.
The European search opinion alleged lack of novelty over a prior art document disclosing an arrangement in which adjacent floor tiles were spaced apart by two parallel, longitudinal walls. In response to this objection, the patentee argued that the two parallel walls in the prior art document together formed a single spacer element. The patentee also amended claim 1 to specify that the alignment direction is a longitudinal direction, and explained that the two parallel walls of the prior art were spaced apart in a transverse direction, rather than the longitudinal direction.
The alleged infringement included a single, continuous spacer having a square wave shape including a plurality of longitudinal portions for abutting against one of two adjacent floor tiles as well as transverse portions connecting the longitudinal portions. Considering the case, the Paris Local Division referred to the fact that statements during grant proceedings may be indicative of the view of the person skilled in the art, citing UPC_CoA_402/2024, and then went on to hold that:
"in this case, the applicant acted on its statements and implemented them by amending its patent application to avoid the objection of lack of novelty. This demonstrates that [the patentee] itself considered at that time that the two parallel walls of [the prior art] were necessary to space the [floor tiles] and therefore constituted a single spacer element... [I]t cannot therefore declare in these proceedings that the [alleged infringement], being made of a single piece, must be considered as two spacer elements."
Thus, the fact that, in response to a novelty objection, the patentee had made certain statements alongside amendments that were in accordance with those statements meant that attempts to argue for different interpretations in the UPC proceedings were unsuccessful. This seems to be a more straightforward application of prosecution history estoppel than that seen in UPC_CoA_402/2024 and 405/2024 and UPC_CFI_612/2024, relying less heavily on the views of the skilled person as a basis for considering the prosecution history.
Implications for practitioners
So, relative to the traditional European reluctance, the UPC seems to be showing considerable openness to considering the prosecution history. Thus, prosecution history estoppel is a potentially powerful tool that should be considered by litigators during proceedings at the UPC.
For patent attorneys, the early signs of the UPC's receptivity to the prosecution history highlights the importance of taking care when submitting arguments and amendments during prosecution and at opposition. But this need for care is not new: while recourse to the prosecution history has historically been rare, it has not been non-existent. Further, patent attorneys should be aware that submissions made in EPO proceedings may be considered relevant in proceedings in other jurisdictions in respect of related patents, as shown in the US by K-fee v Nespresso, Case No. 22-2042, Fed. Cir. Dec. 26, 2023.
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