Recourse To The Prosecution History In The UK

"[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, and perhaps still is, representative of the attitude of courts in the UK to prosecution history estoppel. 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. This briefing examines whether the UK's disinclination to consider the prosecution history has persisted in recent years.

The Actavis framework

The present situation in the UK originates from Actavis UK Ltd v Eli Lilly & Co [2017] UKSC 48, in which Lord Neuberger stated that "it is appropriate for the UK courts to adopt a sceptical, but not absolutist, attitude to a suggestion that the contents of the prosecution file of a patent should be referred to...". Lord Neuberger went on to state that it would be appropriate to refer to the prosecution history where:

• "the point at issue is truly unclear if one confines oneself to the specification and claims of the patent, and the contents of the file unambiguously resolve the point", or
• "it would be contrary to the public interest for the contents of the file to be ignored. ... [This] would be exemplified by a case where the patentee had made it clear to the EPO that he was not seeking to contend that his patent, if granted, would extend its scope to the sort of variant which he now claims infringes."

Shortly after Actavis, the two circumstances set out by Lord Neuberger were considered in Icescape v Ice-World International [2018] EWCA Civ 2219. During prosecution of the patent-in-suit, a claim directed to a system for use in the cooling member of claim 1 was deleted in response to a novelty objection. The defendants in the infringement action argued that the deletion of this claim meant that the patentee had deliberately limited the scope of protection to a cooling member having all of the features of claim 1, including the features of claim 1 that were missing from the defendant's product. On this basis, the defendant argued that there could not be any infringement under the doctrine of equivalents.

This argument was considered to be without merit. This was because the court held that it was not possible to determine whether the novelty objection raised by the examiner was a sound one, or whether it was necessary to delete the system claim to resolve the objection. Moreover, the court held that it was not possible to discern from the correspondence in the prosecution history any suggestion that the patentee was surrendering an ability to argue that the features missing from the defendant's product were inessential, or that the patentee was accepting that the scope of the claims did not extend to a system configured in the manner of the defendant's product. Consequently, it was held that the situation did not fall under either of Lord Neuberger's circumstances. Lord Kitchin concluded the analysis by stating "[i]n my view this is a very good illustration of why it is generally so unprofitable to explore the prosecution history."

A rare example of recourse to the prosecution history

An example of a post-Actavis case in which the prosecution history was considered is Akebia Therapeutics Inc v Fibrogen, Inc [2020] EWHC 866 (Pat). During the prosecution of the patent-in-suit, the patentee had chosen to limit the scope of claim 1 to a specific formula (Formula I) in order to overcome a novelty objection. Arnold LJ held that, in doing so, the patentee had represented that it was not seeking to contend that the patent, if granted, would have a scope that extended to compounds beyond the confines of Formula I. Arnold LJ went on to hold that the patentee's infringement case relied on them seeking to extend the scope in this way, and so stated that:

"this is one of those cases referred to by Lord Neuberger in Actavis v Lilly at [88] where it would be contrary to the public interest for the contents of the prosecution file to be ignored."

Interestingly, when limiting claim 1 to Formula I during prosecution, the patentee stated "[a]ny deleted subject matter is not abandoned" and "[a]lthough the applicant maintains that the previous claims were patentable, the applicant has amended the claims to simplify the outstanding issues in the hope of progressing the applicant to grant". These statements were given no weight at all, with Arnold LJ stating:

"[the patentee] cannot have it both ways. If it wanted a broader claim, it should have maintained its position in the face of the examiner's objection and, if necessary, appealed to the Board of Appeal (as was its right). It did not do so, but accepted a narrower claim. It is inconsistent with that acceptance for it now to say that the claim extends beyond that."

This example of prosecution history estoppel in a UK court is, though, a rare one, and it is much easier to find examples of cases in which attempts by defendants to rely on the prosecution history failed because the situation was considered not to fall under either of Lord Neuberger's two circumstances.

Recent clarification of the Actavis framework

Recently, there has been some clarification of the two circumstances in Siemens Gamesa v GE Energy [2022] EWHC 3034 (Pat), restated in Samsung Bioepis UK Ltd v Alexion Pharmaceuticals Inc [2025] EWHC 1240 (Pat).

In the Samsung case, reviewing Lord Neuberger's comments in Actavis, Meade J held that circumstances (i) and (ii) "have to be read in the light of the scepticism expressed at the start [the passage]; one expects that they will only rarely arise and that the conditions for them to do so will be stringent."

With regard to circumstance (i), Meade J stated the following:

"[The requirements of circumstance (i) are that] the point of interpretation has to be truly unclear and that the file unambiguously resolves the point. The first requirement will not be met merely because some point of interpretation is arguable both ways in the context of the specification; that happens all the time. More is needed. The second requires that the file provides a clear answer, and will not be met just because the file says something that might be relevant. It is not legitimate to promote the file into a sort of adjunct to the specification and of equal value with it."

With regard to circumstance (ii), Meade J noted that:

"the requirements are that the patentee made it clear that he was not seeking to extend the claims to the sort of variant said to infringe. Again, the mere fact that the file provides something that would have been of some potential relevance to claim scope had it been in the specification is not enough."

By elaborating on the type of situations in which it is not appropriate for the prosecution history to be consulted, these comments can have only restricted the scope for the application of prosecution history estoppel in the UK.

Given Meade J's comments, it is unsurprising that, in the Samsung case, it was concluded that the situation did not fall under either of Lord Neuberger's two circumstances. (The judgement in the Siemens case is not publicly available.)

Conclusions

So, while the door to consideration of the prosecution history is not completely shut in the UK, the courts will consider the prosecution history only very rarely. This approach seems to differ from that of the UPC, where various courts have shown openness to using the prosecution history in claim interpretation. For a review of the approach of the UPC to prosecution history estoppel, see our briefing here.

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