Alex Bone, Patent Attorney, Partner,  AA Thornton

The market exclusivity provided by a patent can be crucial for allowing a company to obtain a return on their R&D investment.

A patent is essentially a deal in which, in return for an applicant disclosing their invention, a government grants the applicant the right to prevent third parties from exploiting that invention without the applicant’s permission. The idea is to encourage sharing of innovations to facilitate further technical developments. An applicant may consider limiting the disclosure to avoid giving competitors the full benefit of their R&D efforts, but this can cause problems with plausibility and prevent a patent from being granted so a balance must be found.

Neither the UK Patents Act, nor the European Patent Convention, explicitly refer to plausibility. Nonetheless, the concept features in decisions from both the UK Intellectual Property Office (UK IPO) and European Patent Office (EPO) and is generally used to prevent speculative applications, for example those containing broad claims but little or no technical information, from resulting in granted patents.

The UK IPO and EPO assess plausibility of an invention alongside sufficiency of disclosure. The assessment is based upon the information in the application as originally filed together with the common general knowledge of the skilled person in the technical field at the time of filing. An applicant cannot refer to data published, or made available, after an application has been filed in support of plausibility. If it was not plausible that an invention would work across the full breadth of the claim at the time of filing, it will remain not plausible even if data is later filed to show that it actually does work across the breadth of the claim.

There is no requirement to provide experimental data or test results in a patent application. For applications in many technical fields this is not a problem as a particular technical result may be self-evident, or at least predictable. However, in technical fields like pharmaceuticals, where results can be difficult to predict and beneficial effects may require experimental data to confirm, it is important to provide sufficient detail on filing to render a technical effect plausible across the entire breadth of the claimed invention. Merely stating that an effect is provided (instead of providing a range of examples and/or a reasoned explanation) may well be considered insufficient basis for plausibility.

The EPO may also consider plausibility in another situation. Where a technical effect is relied upon to justify that an invention is not obvious (i.e. that it possesses an inventive step) the plausibility of that technical effect being provided can be important. When considering inventive step, and depending upon the plausibility of the technical effect, the EPO may consider data published, or made available, after an application has been filed as evidence of that effect. Unfortunately the EPO’s current approach is not uniform.

Some EPO Boards of Appeal consider that a claimed technical effect must be plausible before they will consider such data in support. If sufficient detail or data is not present in the specification as originally filed this can lead to a squeeze in which the applicant must argue that the effect is plausible, for example with reference to published documents or common general knowledge, for data to be considered. Unfortunately arguments that a technical effect might be predictable from what is already known may lead the EPO to consider that the invention itself is obvious.

Other EPO Boards have adopted a much lower hurdle and will consider additional data in support of a claimed technical effect provided the claimed effect is not implausible, while yet other EPO Boards appear to consider that neither approach is appropriate due to incompatibility with the EPO approach to assessing inventive step using the “Problem/Solution” approach.

Some clarity regarding the approach that should be taken may be provided following a referral in October 2021 to the Enlarged Board of Appeal at the EPO (case G2/21) to look at this issue. The Enlarged Board is likely to take time to provide useful clarity so it remains advisable when filing a patent application to provide as much data as possible regarding the invention and any technical effects to try to avoid plausibility problems. Producing the experimental data that might be required takes time and there is often a compromise required between filing as soon as possible and delaying filing to ensure that sufficient data can be included.

If you have any queries regarding this topic, or other pharmaceutical or biotechnological matters, please contact Alex Bone at or visit