CA-2025-001040 - [2025] EWCA Civ 903

Grounds 1-3: interpretation of the Patent

Ground 1 is that the judge wrongly assessed the disclosure of the Patent at [238]-[241] when he found that it did not comprise a verbal statement of an experimental result. AstraZeneca relies on the principle, which is not in dispute, that the skilled person or team reads a patent with a “mind willing to understand, not a mind desirous of misunderstanding” (Generics (UK) Ltd v Yeda Research and Development Co Ltd [2012] EWHC 1848 (Pat) at [192]). Given that the Patent is all about dapagliflozin, that it contains repeated references to “the SGLT2 inhibitor of formula I” and that the purpose of the assay described in [0115] is to measure “SGLT2 activity of the compounds of the invention” as stated in [0114], AstraZeneca contends that the skilled team would understand that the “inhibitor” referred to in [0115] must be dapagliflozin.

The Claimants point out that, as Lord Diplock emphasised in Catnic Components Ltd v Hill & Smith Ltd [1982] RPC 183 at 242, “a patent specification is a unilateral statement by the patentee, in words of his own choosing”. Even so, if the issue were one purely of language, AstraZeneca’s argument might have some merit. A patent, however, is a technical document addressed to technical readers. It is to be read through the eyes of the skilled person or team having the common general knowledge. Read in that way, I have no hesitation in agreeing with the judge.

What would immediately strike the skilled team about [0115] is that it does not identify the “inhibitor”. It is purely a description of a method. If one is looking for linguistic clues, it is noticeable that it does not even refer to “the inhibitor”, which might be taken to be a reference to a specific, even if unidentified, inhibitor. It simply uses the word “inhibitor” as a generic term for the substance being tested. If [0115] was intended to record a test that had been performed on dapagliflozin, then it would surely have said so. Nothing would have been easier, and there is no good reason why that statement should not have been made, if that were the case.

Furthermore, the skilled team would note that [0115] does not itself contain even a verbal statement of a result. It does not say, for example, “the inhibitor was found to have SGLT2 activity”, let alone “significant [or suitable or some other such term] SGLT2 activity”. Again, nothing would have been easier, and there is no good reason why that statement should not have been made, if that were the case.

AstraZeneca contended in paragraph 4 of its grounds of appeal and paragraph 16 of its skeleton argument that the judge ought not to have relied upon the expert evidence to which he referred at [239] to resolve what is properly a matter of documentary interpretation for the court. I did not understand counsel for AstraZeneca to pursue this contention in oral argument, but in any event I would reject it. The judge made a finding in [239], based on the expert evidence, as to a technical consideration which would bear upon the skilled team’s reading of the Patent, namely that the assay described in [0115] could have been performed on other compounds either in validating the assay or in assessing the SGLT2 inhibitory activity of other compounds (such as one or more of those described in WO 128). It follows that the Patent must be interpreted with that consideration in mind. The judge did not make the mistake of treating the expert evidence as determinative of the issue of interpretation.

Instead, counsel for AstraZeneca focussed his argument on the proposition that the evidence did not establish that the skilled team would think that only other compounds had been tested and dapagliflozin had not. This argument makes the very mistake which AstraZeneca’s abandoned argument accused the judge of making, namely of treating the issue of interpretation as being one for expert evidence. In interpreting the Patent, what matters is that [0115] gives the skilled team no reason to think that dapagliflozin has been tested when there are alternative possibilities which are equally consistent with the language used.

Ground 2 is that the judge wrongly assessed the disclosure of the Patent at [253]-[260] when he found that the Patent did not disclose enough to make it plausible that dapagliflozin will treat diabetes. AstraZeneca contends that the judge should have found that the assay result was that dapagliflozin had been shown to be an SGLT2 inhibitor at a useful level of activity. The sole basis for this contention is the repeated references in the specification to dapagliflozin as an SGLT2 inhibitor useful for the treatment of diabetes.

This argument can only get off the ground if AstraZeneca succeeds on ground 1. Even on that assumption, however, I do not accept it. As the judge rightly said, it is a bootstraps argument. The repeated references in the specification to dapagliflozin being an SGLT2 inhibitor useful for the treatment of diabetes are pure assertion. Even if the skilled team understood [0115] to mean that dapagliflozin had been tested and found to demonstrate some unspecified degree of SGLT2 inhibition, there is no information in the Patent as to: (i) what level of SGLT2 potency was obtained, even in purely verbal terms; or (ii) more specifically, the EC₅₀ value that was determined; let alone (iii) whether the EC₅₀ value was sufficient to confer utility. The judge made findings in [254] and [257], based on the expert evidence, that the potency could have been in the millimolar range, which would not have been enough for practical utility, and that not every compound which produced a measurable EC₅₀ in an in vitro SGLT2 inhibition assay would have been regarded as plausibly having a useful effect on the diabetes disease state.

AstraZeneca’s only real answer to this was to attack the judge’s findings as being unsupported by the evidence of Prof Bailey which the judge quoted in [256]. This is not a ground of appeal for which AstraZeneca has permission. In any event, it is a hopeless argument. The evidence of Prof Bailey provided ample support for the judge’s finding and it did not stand alone, as the judge made clear. Counsel for AstraZeneca pointed out that the first passage quoted by the judge was in the context of WO 128, and only the second in the context of the Patent, but there is nothing in this point because the disclosures of the documents are the same with respect to the assay.

Ground 3 is that, had the judge correctly interpreted the patent, he should have concluded that the claimed inventions were plausible even applying the standard laid down in Warner-Lambert. This depends on AstraZeneca succeeding on both grounds 1 and 2, and therefore does not arise.