UK divergence from the EPO on plausibility (Sandoz v BMS), Part 2: Interpretation of G 2/21

This is the second post considering the Court of Appeal decision on plausibility in Sandoz v BMS ([2023] EWCA Civ 472), in the context of the Enlarged Board of Appeal decision in G 2/21. To this Kat there are some crucial differences between the approach of the UK courts and EPO to the question of the standard of evidence required to support a patent. As discussed in Part 1, unlike the EPO, the UK courts appear reluctant to move away from the language of "plausibility" itself, despite it being dismissed by the EBA as a generic catch-word that does not amount to a distinctive legal concept. Furthermore, as discussed below, in attempting to reconcile G 2/21 with the Supreme Court decision in Warner-Lambert, Lord Justice Arnold (Arnold LJ) in Sandoz v BMS is forced to disagree with the interpretation that G 2/21 supports the established "lack of ab initio implausibility" standard. The UK therefore appears at risk of continued divergence from the EPO on the correct legal test for the standard of evidence in sufficiency and inventive step.

Sandoz v BMS: Facts of the case

The case in Sandoz v BMS related to BMS's European (UK) patent EP 1427415. The patent claimed the chemical compound apixaban. The technical effect relied on for inventive step was the efficacy of apixaban as a factor Xa inhibitor. However, the application as filed did not provide data specifically showing the inhibitory effects of apixaban on factor Xa. The question before the Court of Appeal in Sandoz v BMS was similar to that considered in G 2/21. Particularly, how much evidence is needed to support a (non-claimed) technical effect relied on for inventive step?

The High Court ([2022] EWHC 822 (Pat)) found the patent to lack sufficiency and inventive step. Particularly, the judge found that it would not have been plausible to a skilled person at the filing date that apixaban was a factor Xa inhibitor. BMS appealed the decision on several grounds (para. 89), mostly relating to whether the High Court had appropriately applied the law on plausibility as established by the UK Supreme Court in Warner-Lambert v Actavis [2018] UKSC 56. A key question on appeal was also how the recent EBA decision in G 2/21 influenced how the "plausibility" test should be applied. 

Was G 2/21 even about plausibility?

The EBA in G 2/21 provided some self-confessedly "abstract" principles, the implications of which are still open to interpretation (IPKat). Particularly, in G 2/21, the EBA found that the test for whether a purported technical effect can be relied on for inventive step is whether "the skilled person, having the common general knowledge in mind, and based on the application as originally filed, would derive said effect as being encompassed by the technical teaching and embodied by the same originally disclosed invention" (G 2/21, headnote 2). 

The referring Board of Appeal in G 2/21 (to which the case has now been remitted) recently invited the parties to submit their interpretations on G 2/21 (IPKat). According to one interpretation proposed by the Board itself, the decision in G 2/21 actually has nothing to do with plausibility. Under this interpretation, G 2/21 merely provides guidance on whether a technical effect relied on for inventive step has to be "mentioned" in the application as filed. This is a separate question to whether, if mentioned, a skilled person would have substantiated doubt about the invention achieving the technical effect.

Did the Court of Appeal fall off
the wall on plausibility?

A second interpretation of G 2/21 proposed by the referring Board is that the decision confirms the existing case law on the standard of evidence required for inventive step. Particularly, G 2/21 confirms that, in order to be relied on for inventive step, there should not be substantiated doubt that the invention actually achieves the said technical effect (i.e. ab initio lack of implausibility) (IPKat). This interpretation leaves open the question of whether the technical effect needs to be explicitly identified in the application as filed, or whether it can be identified post hoc. 

Taking either of the interpretations of G 2/21 proposed by the referring Board, it is difficult to argue that G 2/21 supports an "ab initio plausibility" test for a technical effect relied on for inventive step.  In G 2/21, the EBA also took pains to move the language of the debate away from "plausibility", a term that lacks any basis in the EPC. The EBA instead favoured the established language from the EPO case law that there should not be "any substantiated doubt, supported by verifiable facts," over a claimed invention or its technical effect. This language is more closely aligned with the "lack of ab initio implausibility" test (IPKat). 

Are G2/21 and Warner Lambert aligned?

In Sandoz v BMS, Arnold LJ considered G 2/21 in the context of the decision of the UK Supreme Court in Warner-Lambert. In Warner-Lambert, the majority view found that a broad claim to the therapeutic use of a compound to treat neuropathic pain was not sufficiently disclosed over the full scope of the claim. Particularly, it was found that it would not have been plausible to a skilled person at the priority date that the compound could be used to treat neuropathic pain. Arnold LJ characterised the majority view of the Supreme Court in Warner-Lambert as corresponding to an "ab initio plausibility" test. In other words, with regards to inventive step, it must be plausible from the application as filed that the invention solves the problem it purports to solve. 

Arnold LJ disagreed with the EBA in G 2/21 that the ab initio plausibility test of Warner-Lambert could be reconciled with the alternative "lack of ab initio implausibility" test, i.e. the test whereby it must just not be implausible in view of the application as filed that an invention achieves the purported technical effect. Particularly, Arnold LJ pointed to the disagreement amongst the judges in Warner-Lambert as evidence that the "ab initio plausibility" and "lack of ab initio implausibility" tests, if applied to the same facts, may have different practical consequences (para. 94). However, unlike the the referring Board of Appeal in G 2/21 (IPKat), Arnold LJ interpreted G 2/21 as endorsing the "ab initio plausibility" test expounded by the majority view in Warner-Lambert. As such, Arnold LJ found that G 2/21 provided no justification for deviating from Warner-Lambert (para. 94).

Applying G2/21

The focus of the EBA in G 2/21 was very much on what a skilled person would understand as the technical teaching of the application as filed, in view of CGK. For Arnold LJ in Sandoz v BMS, it was clear from the case law that it is not sufficient for the application to merely "encourage the skilled person to carry out tests" that might confirm the efficacy of the claimed product (para. 94). This reasoning corresponds most closely to the ab initio plausibility standard. Having reviewed the decision of the EBA in G 2/21 in the context of Warner-Lambert, Arnold LJ found no error in the judgment of the High Court that the patent was invalid for lack of sufficiency and inventive step. Arnold LJ dismissed all of the grounds of appeal submitted by BMS. 

Crucially, however, in this reasoning, Arnold LJ is applying the test for sufficiency, not inventive step. As such, the decision is not entirely aligned with G 2/21. As the EBA in G 2/21 itself noted "the scope of reliance on post published evidence is much narrower under sufficiency of disclosure (Article 83 EPC) compared to the situation under inventive step (Article 56 EPC)" (r. 77).  The problem faced by the Court of Appeal in applying G 2/21 is thus the natural consequence of not recognising that G 2/21 is about the standard of evidence or disclosure of a non-claimed technical effect relied on for inventive step, not sufficiency. 

Final thoughts (Part 2)

Whilst the correct interpretation of G 2/21 still requires some interpretation from the Boards of Appeal, the decision in Sandoz v BMS is at odds with the view that G 2/21 supports an ab initio lack of implausibility standard of evidence for a purported technical effect relied on for inventive step. To this Kat, the EPO approach to plausibility in inventive step and sufficiency is broadly consistent, and confirmed in G 2/21. The approach of the UK courts to plausibility, on the other hand, still fits Sir Robin Jacob' characterisation of it as a humpty-dumpty-ish approach (i.e. the Humpty Dumpty of Lewis Carroll's Alice through the looking glass, for whom words have flexible meanings: "'When I use a word', Humpty Dumpty said in rather a scornful tone, 'it means just what I choose it to mean.'"). The decision of the Court of Appeal in Sandoz v BMS does nothing to assuage this impression. 

If readers are interested in hearing more about plausibility, tickets are still available for CIPA Congress on 3 October. PatKat will be joining Ian Jones (GJE), James St.Ville KC (8 New Square), Sarah J. Rodriguez (Finnegan), in an afternoon panel discussion on plausibility in all its guises, chaired by Greg Corcoran (ASML).

Further reading

UK courts

• No pain, no gain: Plausibility in Warner-Lambert v Actavis (2018)
• Takeda v Roche: "Is it plausible? Is it true?" (Aug 2019)
• UK divergence from the EPO on plausibility (Sandoz v BMS), Part 1: Is the "plausibility" test the same for both sufficiency and inventive step? (July 2023)

EPO

• Plausibility demystified - a review of EPO case law before G 2/21 (Feb 2023)
• G 2/21: Is the technical effect embodied by the invention as originally disclosed? (March 2023)
• To encompass and embody: Applying the abstract principles of G 2/21 (March 2023)
• Applying G 2/21: Preliminary opinion from the referring Board of Appeal on post-filed evidence appeal (T 0116/18) (June 2023)

US (Enablement & Written Description)

• Patenting Antibodies: The epitope claim is dead, long live the epitope claim (Nov 2021)
• Strict US written description requirement applied to CAR-T-cell therapy (Juno v Kite) (Jan 2022)
• US Supreme Court decision in Amgen v Sanofi: The European Perspective