An improved Improver? - Part 2

Here as promised is the second part of this GuestKat's commentary on Eli Lilly v Actavis UK [2017] UKSC 48, which promises to have much ink spilled and air of various temperatures emitted on its behalf in the coming weeks, months and years. As noted in the first post, the Supreme Court reformulated the Improver questions, originally posed by Lord Hoffmann when at first instance and subsequently further evaluated by him in the House of Lords in Kirin-Amgen, which thoroughly examined the UK approach to patent claims. This GuestKat has regarded Lord Hoffmann's judgment in that case as a definitive guide to interpretation and construction and it is a bit of a shock to see his analysis criticised as "wrong in principle" by the Supreme Court. More on that later. Now we should move on to the other aspects of the case, starting with the question of the role of the prosecution history in interpreting the scope of claims.

The file was not extensive ...

The starting point for the claims of the patent was a claim to "use of a methylmalonic acid lowering agent in the preparation of a medicament useful in lowering the mammalian toxicity associated with an antifolate, and the medicament is administered in combination with an antifolate". Here the "methylmalonic acid lowering agent" is something like vitamin B12 and the antifolate is the pemetrexed derivative. 

In a first attempt at amendment of the claims during prosecution, Lilly offered limitation of the antifolate to "pemetrexed" and of the methylmalonic acid lowering agent to vitamin B12, but the examiner objected that the amendments introduced subject matter beyond that originally filed, contrary to article 123(2) EPC. Reference to "pemetrexed" did not find any basis in the application documents, which referred only to pemetrexed disodium. That, according to the examiner, is a distinct compound from pemetrexed (the free acid). In response, Lilly filed claims limited to the use of pemetrexed disodium in combination with vitamin B12. This led the Supreme Court to the consideration of two important questions: when is it permissible to have recourse to the prosecution history of a patent when considering whether a variant infringes, and whether the prosecution history in this case should alter the provisional conclusion the court had reached on direct infringement.

After looking at the comments of Lord Hoffmann in Kirin-Amgen about the undesirable consequences of permitting reference to prosecution history, and at the approach of courts in other EPC states, the court concluded that it was appropriate to take "a sceptical, but not absolutist, attitude" to reference to the prosecution file "along substantially the same lines as the German and Dutch courts". The comments of the court on the practicalities of reference to the file are interesting. They thought it was tempting to exclude the file on the basis that anyone should be entitled to rely on the content of the patent itself, without reference to other material, "as a matter of both principle and practicality". However, given that the contents of the file are publicly available, there might be occasions when justice might require reference to the file. The court seems to have been influenced in that conclusion by having been told that the contents of the file "are unlikely to be extensive". However, the circumstances in which a court can rely on the prosecution history "must be limited". That meant where (i) the point at issue is truly unclear if one confines oneself to the specification and claims, and the contents of the file would unambiguously resolve the point, or (ii) it would be contrary to the public interest for the contents of the file to be ignored. An example of (ii) would be where the patentee had made it clear to the EPO that he was not seeking to contend that his patent, if granted, would extend to the sort of variant which he now claims infringes.

Applying that to the facts of the case, the court didn't think the prosecution file justified departing from its conclusion on direct infringement. The reason the examiner thought the claims should be limited to pemetrexed disodium was because the specification did not expressly extend to any other anti-folates (although the court seemed to think the examiner was wrong about that, without explaining why). But in the court's opinion, "the whole point of the doctrine [of equivalents] is that it entitles a patentee to contend that the scope of protection "extends beyond the ambit of its claims as construed according to normal principles of interpretation". 

This GuestKat has noted with interest comments which suggest that this case opens the way to a doctrine of "file wrapper estoppel" in the UK, but wonders whether the case really goes much further than existing UK case law which has admitted reference to the file in cases of "admissions against interest" - see for example Rohm & Haas v Collag [2002] F.S.R. 28 and Furr v Truline [1985] F.S.R. 553. The refusal of the court to admit reference to the file in this case is consistent with the court not regarding the limitation to the disodium salt during prosecution as determinative of whether the patentee could argue for scope of the claim to include other salts or the free acid after grant based on the reference to equivalents in Article 2 of the Protocol. Presumably the court took the view that Lilly had not "made it clear to the EPO that [it] was not seeking to contend" that the patent, if granted, would extend to other salts such as pemetrexed dipotassium. 

Such an approach might open the door to more difficulty in interpreting a claim from the point of view of infringement, if one cannot decide on the question of equivalents without recourse to external resources such as expert evidence. Note that the court itself says that answering its question (ii) "does the variant nonetheless infringe because it varies from the invention in away or ways which is or are immaterial?" raises questions "which would normally have to be answered by reference to the facts and expert evidence". This seems potentially to admit far more extraneous material into the process of claim construction than reference to the file, which at least is self contained, even it may sometimes be more "extensive" than the court had been led to believe. 

This GuestKat is impressed with the number of comments which the first post on this case has generated on the question of claim scope and interpretation, and thanks those who have contributed to an intelligent debate on the subject. The Supreme Court was clearly influenced in its decision by its study of the case law in other European countries, for example these quotations from the Bundesgerichtshof: that a variant will infringe if (i) “it solves the problem underlying the invention with modified but objectively equivalent means”, (ii) this would be recognised by the person skilled in the relevant art, and (iii) that person “focus[sing] on the essential meaning of the technical teaching protected in the patent” would regard the variant “as being equivalent to the solution” offered by the invention (Case No X ZR 168/00, 2002 GRUR 519 (Schneidmesser I). It seems to this GuestKat that in the context of the present case, this leads to a focus on the practical and technical solutions which an appropriately skilled person might regard as "equivalent" to the solution defined by the claim, with less regard to the actual words which the drafter has used to express that solution. It is not clear to this Kat whether this makes a patent attorney's job easier or more difficult, particularly if the object of clear wording in the claim might be to exclude embodiments which the drafter wants to exclude, for example if they fall within the prior art. It also surely means that the scope of a claim can't be definitively determined without recourse to material outside the patent specification, such as expert evidence (as considered above), which surely makes the job of advising on infringement more difficult. No doubt debate on the meaning and consequences of this decision will continue for some time to come. 

Taking another pause for breath at this point, the remaining aspects of this case will be explored in Part 3 of this series.