This decision highlights the importance of technical data or technical reasoning on the filing date to demonstrate plausibility and hence inventive step and sufficiency.

The UK Court of Appeal recently issued a decision on plausibility in relation to a European Patent No. 1427415. This patent is for a compound called Apixaban, marketed by BMS under the trademark Eliquis. Apixaban is a factor Xa inhibitor which is used to treat thromboembolic disorders.

The patent was invalidated by the UK High Court because it was found that the specification did not make it plausible that Apixaban would have any useful factor Xa inhibitory activity.

The patent application did not disclose any specific data related to Apixaban but asserted that;

a number of compounds of the present invention were found to exhibit a Ki of <10 µM, thereby confirming the utility of the compounds of the present invention as effective Xa inhibitors”.

BMS (the patentee) appealed the decision and argued that there is no requirement for the specification to make it plausible that a compound is useful, and that it should be enough for the specification to disclose the structure of the compound, a method of synthesis, and contain an assertion of utility for the compound provided that that assertion is not manifestly speculative or wrong.

BMS argued that the Court should not have assessed plausibility based on the Warner-Lambert decision, which they said was limited to ‘second medical use’ claims. That decision said that a technical effect on which a claim is based, must be made plausible by technical reasoning or data – not merely by an assertion of efficacy. BMS’s reasoning was that because their claim was directed to a single compound, rather than to a ‘medical use claim’ (e.g. ‘Apixaban for treating a particular condition’), the test for plausibility should be different to the one in Warner-Lambert. This distinction was rejected by the Court.

Lord Justice Arnold reviewed the more recent EPO decision of G2/21 and concluded that this decision does not justify a departure from the Warner-Lambert principles. He explained that when considering inventive step, it is necessary to consider the technical problem which the claimed invention solves, and when considering sufficiency it is necessary to consider whether the specification sufficiently discloses the claimed invention. If either of these is not plausible from the application as filed, then the patentee has made no technical contribution and the specification does not disclose any invention. Furthermore, it was clarified that the ‘plausibility’ test is the same for sufficiency and inventive step  –  one must demonstrate a technical effect using technical evidence, or provide technical reasoning as to why a technical effect is plausible. The Judge concluded:

in order for a claim to a single chemical compound to be patentable, the application must make it plausible, …that the compound has the utility asserted for it. It makes no difference whether the claim incorporates the use of the compound as a technical feature or whether the claim is simply to the compound per se and the assertion of utility is only to be found in the specification. This is because there is no invention in merely identifying a new chemical compound; invention can only lie in identifying its utility.”

The application as filed did not identify which of the 74 compounds mentioned in the original application were tested and hence did not explicitly or implicitly disclose that Apixaban was tested and found to have a Ki of <10 µM.

Moreover, the Judge found that;

in the absence of any theory based on e.g. its structure or any data in the specification, there is simply nothing in the Application to support the assertion that Apixaban is a factor Xa inhibitor, let alone a factor Xa inhibitor of sufficient potency to be useful in therapy. It is irrelevant that BMS subsequently proved that the assertion was well founded and limited the claim to Apixaban.

The patent was therefore invalidated for a lack of plausibility as the Judge concluded that the patent made no technical contribution to the art. What is surprising is that there were hints in the application that the applicant might have actually known that Apixaban was a particularly active compound and had the data to prove it. But, as the previous case law demonstrates, you don’t get something for nothing. If you don’t show data/reasoning which makes the invention plausible, you won’t get a patent.

It will be interesting to see whether the EPO provides guidance on their stricter approach to plausibility for sufficiency relative to plausibility for inventive step, as was foreshadowed in G2/21. The EPO approach looks like it could be at odds with the approach of the UK courts.

We don’t think that this decision has an impact on best practice for drafting patent specifications. It does however highlight the importance of technical data or technical reasoning on the filing date to demonstrate plausibility and hence inventive step and sufficiency. This applies to justifying both broad inventive concepts and to subsidiary narrower, but nonetheless inventive subject matter.

If you would like further information on this matter, please get in touch with one of our patent attorneys.


Khushbu Solanki

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