Plausibility and post-filed data at the EPO part II – the technical and legal facts of G 2/21

Plausibility and post-filed data at the EPO part II – the technical and legal facts of G 2/21

This is the second part of our three-part article on EPO Enlarged Board of Appeal referral G 2/21. Here, we analyse the technical/legal facts of the appeal behind G 2/21 and provide a digest of post-filed data/plausibility issues in practice. Part I provides a five-minute summary of what you need to know (in a hurry), followed by practical implications for attorneys and applicants to help ensure applications are (plausibly) fit-for-filing and prosecution before the EPO. Part III is a deep-dive into the case law for those looking for the detail, and includes insights that can be gleaned from historical decisions on this area of law.


G 2/21 originated in a still-pending EPO Appeal against granted European patent no. EP2484209. This was opposed and a key issue related to whether or not a claimed combination of compounds provided a synergistic technical effect/advantage as compared with the prior art. 

The claim in question

Claim 1 of EP2484209 relates to a composition comprising two insecticidal compounds: thiamethoxam and a “compound of formula 1a”. D4, also relating to insecticides, was identified as the closest prior art. In D4, thiamethoxam and the compound of formula 1a were mentioned in two separate lists of insecticides. However, there was no individualised embodiment/example comprising both insecticides together, in a single composition. Under these circumstances, the EPO considers claim 1 of EP2484209 novel (under the EPO “two-list principle”).
Claim 1 therefore is then assessed under EPO inventive step rules relating to “selection inventions”. Here, if the patentee can prove that there is an unexpected synergy in combining the two insecticides into a single composition, then inventive step will generally be acknowledged. In other words, does the composition provide greater insecticidal activity than the sum of its parts (the sum of thiamethoxam and compound of formula 1a)?

The opposition

The patent application as filed did contain data allegedly showing that the claimed insecticides act synergistically against certain species of moths (Spodoptera litura and Plutella xylostella). However, an opponent filed their own data showing that thiamethoxam and chlorantraniliprole (a representative compound of formula 1a) did not always act synergistically against these species and that the technical effect was therefore not achieved across the entire scope of the claims (i.e. not for all compounds of formula 1a). 
The opposition-appeal is being heard by the EPO Technical Board of Appeal (TBA) in T 116/18. The TBA noted, with respect to the application as filed, that “arbitrarily combining compounds known to have insecticidal activity to achieve an alternative insecticide composition does not require an inventive step”. 
However, the patentee filed further data demonstrating synergy for thiamethoxam and a representative sample of compounds of formula 1a, now against a different species of moth as compared with the data in the application as originally filed (species Chilo suppressalis). The TBA acknowledged that “the provision of an insecticide composition in which the insecticides act synergistically against Chilo suppressalis” would be inventive over D4 and acknowledged that the post-filed data (also known as post-published data) supported this synergy across the scope of the claims. The only question is whether the post-filed data can actually be relied upon. These post-filed data were the only proof of synergy for the insecticidal composition against Chilo suppressalis
Hence, the outcome of the EBA referral will dictate whether or not inventive step can be acknowledged, and therefore whether the patent can be maintained.

What would each threshold standard being considered in G 2/21 mean for this patent?

The referring TBA in T 116/18 did not comment on how the case in question would be decided under each of the three standards. Nonetheless, the fact that the TBA has referred questions to the EBA implies that the outcome will determine whether they will accept the post-filed data and therefore whether inventive step will be acknowledged.
Our predictions, depending on the threshold standard decided in G 2/21, are as follows:
(a)        No plausibility standard: low bar

  • No consideration of plausibility would be necessary since no data (or other information supporting technical effects/advantages) would be required on filing to support inventive step, so the post-filed data would be admitted. 

  • Technical problem solved: providing synergistic insecticidal activity.

  • Inventive step would be acknowledged.

(b)        “Ab initio implausibility” standard (plausibility is assumed on filing): medium bar

  • The referring TBA implies that there were no legitimate reasons to suspect that the claimed composition demonstrated synergistic insecticidal activity against Chilo suppressalis was implausible at the time of filing.

  • The post-filed data would therefore likely be admitted.

  • Technical problem solved: providing synergistic insecticidal activity.

  • Inventive step would likely be acknowledged.

  • On 13 October 2022, the EBA issued a preliminary, non-binding, opinion that this was the standard they preferred. However, this position could change during the oral hearing scheduled for 24 November 2022.

(c)        “Ab initio plausibility” standard (plausibility to be proven on filing): high bar

  • We suspect the TBA does not consider the application as filed to plausibly show that the claimed composition demonstrated synergistic insecticidal activity against Chilo suppressalis.

  • The post-filed data would therefore likely not be admitted.

  • Technical problem must be reformulated in a much less ambitious way: providing an alternative insecticide.

  • Inventive step would likely not be acknowledged.


Inventive step vs. sufficiency

As a final comment, although G 2/21 and T 116/18 relate to inventive step, it should be noted that plausibility can also arise under the umbrella of sufficiency of disclosure. Here, the facts at issue may not relate to the prior art and instead arise when the technical effect/advantage is itself explicitly claimed. This commonly arises where a claim includes a functional feature or method step (e.g. if a claim is directed to the treatment of a specific medical condition as a functional feature). Here, it is vital to ensure that any explicitly-claimed technical effects or advantages are well-supported.
As mentioned, a preliminary, non-binding, opinion was issued by the EBA on 13 October 2022. This indicates that the outcome of G 2/21 may apply only to cases of inventive step plausibility, and may not extend to sufficiency. This stems from the fact that the particular issue referred to the EBA relates to the acknowledgement of inventive step – in the EBA’s view, it may not be appropriate to extend the scope of the referral to include the context of sufficiency. We therefore expect cases of sufficiency plausibility to be largely unchanged by G 2/21, and that EPO Boards of Appeal and Examiners will continue to decide these on a case-by-case basis.
A notable point raised in some of the G 2/21 amicus briefs (written opinions by non-parties to the case) is that inventive step and sufficiency plausibility should be assessed on different levels. Edgar Wunder’s brief gives an interesting legal justification for this: the wording of Article 56 EPC (inventive step) refers to an “invention”, whereas the wording of Article 83 EPC (sufficiency) refers to an “application”. Wunder interprets this distinction as meaning that sufficiency of disclosure should be established at the filing date, while inventive step can be assessed later in proceedings (and there should therefore be less of a hurdle for inventive step plausibility). Perhaps, following G 2/21, this interpretation will move closer to reality.

We’re closely monitoring developments: we’ll report further as G 2/21 progresses and the legal landscape becomes clearer. For more information please contact Nick Lee, James Snaith, Joseph Etherington, or your usual Kilburn & Strode advisor.

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