Armchair inventions: plausibility at the EPO (G2/21)


Will it get harder to use post-filed data at the European Patent Office (EPO)?

The issue of plausibility has now been formally referred to the highest judicial authority at the EPO to clarify the circumstances in which post-filed data can be used to assist with patentability of a patent application or validity of a patent.

Background to using post-published data at the EPO

The EPO uses the “problem/solution” approach to assess inventive step. This approach involves determining the technical effect that the invention contributes over the closest prior art. It has become common practice before the EPO to look at whether the technical effect of an invention is “plausible” from a patent application or patent and therefore if it is permissible to file post-published data to confirm the technical effect. This is often critical to whether or not subject matter is considered to be inventive.

However, divergent approaches have developed regarding the circumstances in which post-published data can be taken into account. Firstly, there has been divergence in how the “plausible” standard is applied. Some Boards have decided that post-published should be considered provided the technical effect is not “implausible”, a lower bar than requiring the technical effect to be “plausible”. Secondly, there has been divergence away from the “plausible/implausible” concept entirely, with some Boards holding that this approach is incompatible with the EPO’s requirement that the “problem/solution” approach is used to analyse inventive step. The rationale here is that an applicant cannot be expected to necessarily know what the closest prior art is when the application is filed.

The case underlying the referral

The particular case underlying the referral is an opposition against a patent (EP2484209) relating to an insecticide comprising thiamethoxam and a compound having "formula 1a". The difference between the patent and the closest prior art is the combination of these two components, with the purported technical effect being synergistic activity of the combination. The patent contains experimental data showing that two specific compounds falling within “formula 1a” provide a synergistic effect when combined with thiamethoxam. Post-published data are necessary to confirm that the synergistic effect is achieved with all combinations falling within the scope of the claim, as these data were not present in the application as filed. The Appeal Board in question reviewed the diverging case law on the issue and referred the following questions.

The referred questions

If for acknowledgement of inventive step the patent proprietor relies on a technical effect and has submitted evidence, such as experimental data, to prove such an effect, this evidence not having been public before the filing date of the patent in suit and having been filed after that date (post-published evidence):

1. Should an exception to the principle of free evaluation of evidence (see e.g. G 3/97, Reasons 5, and G 1/12, Reasons 31) be accepted in that post-published evidence must be disregarded on the ground that the proof of the effect rests exclusively on the post-published evidence.

2. If the answer is yes (the post-published evidence must be disregarded if the proof of the effect rests exclusively on this evidence), can the post-published evidence be taken into consideration if, based on the information in the patent application in suit or the common general knowledge, the skilled person at the filing date of the patent application in suit would have considered the effect plausible (ab initio plausibility)?

3. If the answer to the first question is yes (the post-published evidence must be disregarded if the proof of the effect rests exclusively on this evidence), can the post-published evidence be taken into consideration if, based on the information in the patent application in suit or the common general knowledge, the skilled person at the filing date of the patent application in suit would have seen no reason to consider the effect implausible (ab initio implausibility)?

Likely outcome and impact

European Patent Office

The most widely applied approach in practice is the requirement that the technical effect is “plausible” from the original application or patent. It will therefore be surprising if the Enlarged Board’s decision relaxes the standard such that there is no minimum threshold that must be overcome based on the contents of an application or patent before post-filed data can be taken into account. However, as has been pointed out by the referring Board of Appeal, it does not seem equitable that an opponent can file data in any circumstances to try and show that a technical effect is not plausible from a patent application or patent, yet a patentee may not be able to use their own data if the “plausibility” threshold is not met by the contents of the application as filed.

A further point related to these issues is whether the issue of plausibility should be considered in relation to inventive step or sufficiency. If the technical effect is not defined in the claim (as in the case underlying the referral, where the synergistic effect is not referred to in the claim), the EPO currently considers “plausibility” under the heading of inventive step, whereas if the technical effect is defined in the claim, it is considered under “sufficiency”. However, the UK courts generally consider “plausibility” in relation to sufficiency, which may be more appropriate in view of the afore mentioned difficulties with aligning the requirement for “plausibility” with the “problem/solution” approach. However, this point is not directly addressed by the questions being referred and it is therefore quite possible that the EBA will focus on the issue of plausibility under inventive step only.

View from the UK

Plausibility is not a separate ground of objection to the validity of the patent. Rather, it is generallytreated as one element of “sufficiency” and falls to be considered within the context of that statutory framework. It is often described as a “threshold test”, which is satisfied by a credible disclosure. Its purpose is to prevent “armchair inventors” filing speculative patent applications without disclosing an actual contribution to the art.

Prior to the Supreme Court decision in Warner Lambert plausibility was generally considered in two stages: (i) establish whether the disclosure of the patent is credible, as opposed to speculative in light of the CGK of the skilled team; then (ii) the disclosure may be confirmed or refuted by evidence obtained after the priority date. In order to address (ii) it was common for the Court to consider post-priority evidence in the UK. The Supreme Court in Warner Lambert arguably shut down the ability to rely on post-priority evidence, stating: “it is not enough that the patentee can prove that the product can reasonably be expected to work in the designated use, if the skilled person would not derive this from the teaching of the patent”. However, it must be born in mind that the Supreme Court’s comments arose in the context of second medical use claims (i.e. where a new medical use is found for known molecules), and there remains an open question as to how widely the comments can be applied. Parties are certainly continuing to rely on post-priority evidence to support plausibility. That said, looking at plausibility through the lens of “sufficiency”, the date for assessing sufficiency pursuant to Art 83 EPC is the date of the application. As such, perhaps it is right that under the current legislative framework post-priority evidence should not be relied on to support plausibility if the disclosure is not credible from the teaching of the patent itself.


The outcome of this referral will be significant to practice before the EPO but the Enlarged Board of Appeal’s track record suggests that we will probably have to wait a year or two for the result. In the meantime, if the outcome of a case rests solely on whether or not post-filed data can be considered, the EPO should stay the case until the questions are answered. However, given the number of cases that this could affect, we understand unofficially that it is likely to be difficult to convince the EPO that a stay is appropriate. We are happy to discuss any questions, whether general or in relation to specific cases and advise on how best to proceed.

The full appeal decision, including the referral, can be found here.