Court of Appeal upholds invalidity of AstraZeneca's compound patent and clarifies the standard of plausibility

The Court held that the Judge had correctly followed Sandoz v BMS when concluding that the patent did not make it plausible that dapagliflozin was an SGLT2 inhibitor with sufficient efficacy to treat diabetes, as the specification contained only bare assertions. Although the patent focused on dapagliflozin and described in general terms an assay to assess an inhibitor’s efficacy, no result was described. This was therefore insufficient for the skilled person to conclude that dapagliflozin had been tested in the assay or that it had the necessary inhibitory activity to be effective. Furthermore, the Court rejected AstraZeneca’s arguments that the standard of plausibility should be lowered in light of the Enlarged Board of Appeal’s decision in G 2/21, finding that it is not yet possible to say that the Boards of Appeal or the courts of other EPC Contracting States have adopted a settled view as to how the test in G 2/21 is to be interpreted and applied. Therefore, there was no reason to depart from previous UK case law. The Court went on to find that even if the standard applicable is whether the skilled team would have legitimate reason to doubt that dapagliflozin would be useful for the treatment of diabetes (“ab initio implausibility”), legitimate reason would have been found.

The Court also found that the Judge was correct to hold that the patent did not make a technical contribution over the prior art, which was very similar to the patent in suit and disclosed a class of compounds encompassing dapagliflozin. The Court confirmed a selection from the prior-disclosed genus is only inventive if the selection makes a technical contribution because the selected compound in fact has some useful property. Mere plausibility is not enough for this purpose. It concluded that the Judge’s decision was rightly reached, despite the fact that dapagliflozin had proved to be successful, and emphasised the lack of basis in the patent in suit to distinguish dapagliflozin over the class disclosed in the prior art.

AstraZeneca sought to appeal the decision but was refused permission to appeal by the Supreme Court on 31 July.

Generics (UK) Limited & Ors v AstraZeneca AB [2025] EWCA Civ 903