Assessment of “plausibility” requirement from the EPO perspective

Assessment of “plausibility” requirement from the EPO perspective


This article considers how the EPO views the requirement of “plausibility”, which can arise during both the assessment of “sufficient disclosure” of the invention and “inventive step” in proceedings before the EPO, particularly in relation to inventions in the Pharmaceuticals and Life Sciences field.

The EPO Guidelines for Examination (EPO Part F-III, 12) state that if the claimed invention lacks reproducibility, this may become relevant under the requirements of sufficiency of disclosure or inventive step. If an invention lacks reproducibility because its desired technical effect as expressed in the claim is not achieved, this results in a lack of sufficient disclosure, which has to be objected to under Art. 83 EPC (sufficiency). Otherwise, i.e. if the technical effect is not expressed in the claim but is part of the problem to be solved, there is a problem of inventive step, which has to be objected under Art.56 EPC (inventive step).


Historically, the EPO considered the requirement of “plausibility” only in relation to sufficiency of disclosure of the invention. However, in T939/92 (AgrEvo) the EPO Board of Appeal considered “plausibility” under inventive step. In this case, the Board found that the application provided data only for a few compounds to support the technical effect and that it was not credible (plausible) whether the technical effect was achieved by all the compounds covered by the claim, and thus refused the application as not inventive. However, this is not what Article 56 EPC says! According to Article 56 EPC an invention involves an inventive step if, having regard to prior art, it is not obvious to a person skilled in the art.

The EPO Board of Appeal further stated in T 939/92 that the issue of plausibility when assessing sufficiency arises only when the technical effect is part of the claim. However, this does not mean that plausibility is irrelevant to the issue of inventive step under Article 56 EPC.

In other words, if the technical effect is expressed in a claim, for example in a second medical use claim, in which the technical effect (i.e. the new medical use) is defined in the claim, if doubts are raised as to the plausibility of achieving the new medical use, then an objection is likely to be raised under sufficiency. If the effect is not expressed in a claim but is part of the problem to be solved, then an objection is likely to be raised under inventive step.

Relevant EPO case law in relation for “plausibility”

In T 1329/04 (Factor-9/JOHN HOPKINS) the Board of Appeal stated that the definition of an invention as being a contribution to the art, i.e. as solving a technical problem and not merely putting forward one, requires that it is at least made plausible by the disclosure in the application that its teaching indeed solves the problem it purports to solve. In the absence of any data in the application, the Board took the view that post-published evidence to support that the claimed subject-matter solves the problem, can be taken into account only if it is already credible from the original disclosure that the problem is indeed solved. In this case, the post-published evidence was not taken into consideration since it was considered to be the first disclosure going beyond mere speculation of the technical effect in the application.

However, this does not mean that the application must always include some data to support plausibility. In the absence of any data which demonstrates the technical effect in the application as filed, it may still be possible to demonstrate plausibility based on prior art or common general knowledge. However, when relying on prior art or common general knowledge care should be taken as the EPO may rely on the same prior art to find that claimed subject matter lacks inventive step.

In T 0578/06 (Pancreatic cells/IPSEN, June 2011), the Board of Appeal stated that the EPC requires no experimental proof for patentability and considered that the disclosure of experimental data or results in the application as filed and/or post-published evidence is not always required to establish that the claimed subject-matter solves the objective technical problem. However, this is the case only if there is no substantiated doubt.

In T 1642/07 (Arch Development et al., December 2010) the Board viewed the post-published evidence as being a mere confirmation of the technical effect already made plausible based on a convincing theoretical explanation in the application as filed.

In T 433/05 (ConjuChem Biotechnologies Inc, June 2007), the Board took the view that in the light of the disclosure in the patent in suit, which was supported by a post-published document, the board was satisfied that the problem was solved by the subject-matter of the claims.

Thus, for post-published evidence to be taken into account, it is necessary to establish whether or not the asserted invention has been made sufficiently plausible at the effective date of the patent in suit. The basis for this assessment is the application as filed and the common general knowledge of the person skilled in the art at the priority date.

In a more recent decision T 0488/16 (Dasatinib/BRISTOL-MYERS SQUIB August 2017), the Board of Appeal decided that since the technical effect relied on had not been made plausible in the application by way of any data in the application, or similar information available to the skilled person as common general knowledge, post-published evidence could not be used and the problem to be solved was thus to be formulated as the mere provision of an alternative compound.

More specifically, if the nature of the invention is such that it relies on a technical effect, which is neither self-evident, nor predictable or based on a conclusive theoretical concept, at least some technical evidence is required in the application to show that a technical problem has indeed been solved. In T0488/16 decision, it was further confirmed that the issue is not the absence of any in vivo/clinical data, but rather the absence of any verifiable data with regard to the stated technical effect.


The EPO has issued a number of decisions on plausibility, however, none of these decisions are conclusive. The question of plausibility is assessed by the EPO case by case.

From the decisions discussed above, it appears that even if a claim is non-obvious with respect to the prior art or in the absence of any prior art, the EPO could still refuse a case if it is not plausible at the date of filing that the invention does solve the problem it purports to solve.

Likewise, the requirement of sufficiency of disclosure must be met at the date of filing and if the application or patent is found later that it does not meet the requirement, it is no longer possible to correct this deficiency.

In the recent past, the EPO appears to have become more strict with the requirement of plausibility, and therefore it is advisable not to be in a hurry to file an application, especially in the fields of pharmaceuticals and biotechnology, without any clear evidence which supports that the invention has some technical advantages.

It is thus advisable to provide as much information as possible with respect to technical advantage, including any experimental data, at the date of filing, as well as provide examples to show that the invention works. If the EPO or an Opponent raises any substantiated doubt with respect to the plausibility of the invention in opposition proceedings, the burden of proof shifts to patentee/applicant to show plausibility.

T 488/16 is an example of a case where not including any information either in the form of data or theoretical explanation in the application at the date of filing to support that the invention does solve the problem it purports to solve, can result in loss of commercially high value patents.

For commercially important inventions of high value, where there is a significant risk of being opposed by competitors, it is recommended to consider filing applications at national patent offices in parallel with an EPO application.

If you have any queries regarding Plausibility, or any other requirement that may arise during proceedings before the EPO, please contact a member of our Patent Team, who will be able to assist you.

Category: Latest Insights | Author: Leonita Paulraj | Published: | Read more