News | 8. November 2022

Plausibility – an unsolved problem in patent granting

This article was originally published in German on JUVE Handbuch Wirtschaftskanzleien 2022/2023.

The decision of the Enlarged Board of Appeal (GBK) of the European Patent Office (EPO) in the currently pending proceedings G2/21 is awaited with great excitement. This could have a significant impact on the future filing strategy of applicants, because at its core is the question of when an invention is “ready” to file.

Securing an early filing date for an invention is an important aspect of a patent strategy in order to secure one’s own legal position vis-à-vis competitors. For time and cost reasons, the question arises as to how much experimental effort must be expended under patent law aspects before filing a patent application in order to support the claimed effects, or whether corresponding evidence can be submitted subsequently.

Until a decision G2/21 is issued to finally clarify relevant submission questions, this article will discuss practical scenarios that will continue to exist regardless of the answer to the referred questions, but will have to be – possibly re – evaluated with the help of decision G2/21.

Suitability of “evidence” from product development as support of an invention

In the context of a product development, the product of a competitor or the internal ‘gold standard’ is often used as a reference product, regardless of whether the structure or composition of this reference product is known precisely. Such comparative data are often not usable in the context of the ‘problem-solution approach’ applied by the EPO, since, according to established case law, the claimed effect must be clearly attributable to the distinguishing characteristic.

Experimentally investigating the influence of all potentially relevant parameters on the claimed effect and thus exploring the limits of the invention can be time-consuming and financially expensive and usually does not appear to be expedient from the inventor’s point of view.

Irrespective of this, the proof of technical effects can often only be produced with pinpoint accuracy in the knowledge of the objectively closest prior art, e.g. in the examination procedure, since only then will the objectively fitting (because closest to the claimed invention) comparative form be known.

For such reasons, experimental investigations are often postponed to a later point in time. Whether this postponement is possible at all, however, is now to be clarified by the GBK.

Underlying question of G2/21

According to the questions referred, the GBK is primarily concerned with the question of whether evidence such as experimental data must be disregarded only after the patent application has been filed if it constitutes the exclusive evidence for a claimed effect. Three approaches are presented to the GBK, all of which revolve around the criterion of whether or to what extent the information originally provided in the application must render a claimed effect plausible:

The most generous scenario for the applicant would be if the exclusive evidence for a claimed effect could readily be provided after the filing date, i.e., no plausibility requirement at all. This would allow filing an invention in an early, possibly speculative (“immature”) state to secure an early filing date.

However, should the GKB come to the conclusion that minimum plausibility requirements are to be set with regard to the claimed effects in the application itself, a corresponding “ab-initio plausibility” could be applied as a standard for the technical effects.

In a third case, it could be required as a minimum that the claimed effects are at least not implausible from the outset, i.e. that there is no “ab-initio implausibility“.

State of maturity – when is an invention ready to be submitted

Regardless of how the GBK will decide, we always consider it useful to file an application only when advantages over the prior art can at least be named; proof of the technical effects, e.g. by comparative experiments, should be checked before filing.

The “state of maturity” of an invention could be classified as follows:

(i) effects are not (yet) known, only the features characterizing the desired product can be stated.

In this case, if an early filing date is a priority, one could include a “laundry list” of potential effects in the application text, and then pick the desired effect if needed. Although a lack of disclosure does not arise directly from the failure to obtain effects from the application as long as they are not reflected in the claim wording, an entirely speculative invention description could, in some circumstances, call into question the consideration of late evidence or even reworkability.

(ii) Effects are expected and the features of the invention that are causally responsible are suspected.

Here, the expected effects can already be specifically named; these should then at least not be “ab-initio implausible”. From a technical point of view, no doubts should be justified against the possible achievement of the named effects. In the description of the invention in the original application, the challenge is that it is not known which features/parameters are causal for the achievement of the effect. Regardless of decision G2/21, if possible, the “causality” between effects and the corresponding features of the invention should be investigated and explained in the application text. Previously published literature can help to substantiate this causal relationship. Patent law only requires that something works or that a set task is solved; a scientific explanation of how a claimed problem solution works is not necessarily required.

(iii) Effects are expected, it can be concluded on the basis of technical considerations which features of the invention should be causally responsible for them.

A technical explanation that the claimed effects are expected can be given in the patent application (“ab-initio plausibility”). However, a real experimental proof is still missing. In such a case, the prospects of grant – assuming the required novelty – are likely to be good, but it is to be expected that e.g. in possible opposition proceedings the opposing party could attack this “plausibility”, e.g. by submitting reasonable doubts that the theory underlying the plausibility is not correct. Without wanting to anticipate the final decision in the current referral G2/21, however, it should be possible in these case constellations on the basis of the existing “ab initio plausibility” to substantiate the expected technical effects in the factual instance – i.e. not only in appeal or appeal – by means of subsequently supplied experiments and data.

(iv) Effects are known and proven

Here, there should be nothing to argue against filing a patent application. If new prior art is invoked, e.g. in the examination procedure, it should be possible to provide further (post-published) experimental data to support the effects already shown in the application, if required.

Special cases

Special cases exist if technical effects are only proven or expected for a part of a claimed subject-matter, or if a technical effect itself constitutes a claimed feature – e.g. in a use claim. In the first case, the question then arises whether the technical effect can plausibly be generalized to the remaining part of the claim, and in the second case the criterion of “plausibility” will also be relevant in the context of examining whether the invention is sufficiently disclosed at all and thus practicable. Here, too, however, considerations similar to those explained earlier should play a role.


• The decision of the GBK in the proceedings G2/21 will hopefully provide clarity as to the “state of maturity” in which an invention must be filed in order for claimed effects to be recognized.
• In many cases, regardless of the standard to be applied under G2/21, early submission will be desired.
• It is already apparent that the question of “plausibility” does not constitute a patenting requirement in its own right, but is an important criterion in the examination for inventive step and possibly even the practicability of a claimed invention.
• In any case, it is wise to check the maturity of the invention before filing a patent application in order to achieve the best possible result and obtain a strong patent.


Dr. Susanne Sonnenhauser
Ms. Sonnenhauser has been working in the field of intellectual property since 2005 and is admitted as a German Patent Attorney and European Patent Attorney. She joined Prüfer & Partner in 2008.

Her main practice areas are patent and trademark law, mainly in the fields of pharmaceuticals and life science.
Ms. Sonnenhauser represents her clients in both patent grant and opposition proceedings. In addition, she provides expert opinions regarding the validity and infringement of intellectual property rights.

Dr. Andreas Oser, LL.M.
Andreas Oser (Dipl.-Chem. University of Freiburg; Ph.D. Max-Planck-Institute for Biochemistry Munich) has been working in the field of intellectual property since 1991, was admitted as a German and European patent attorney in 1995 and has been a managing partner at Prüfer & Partner since 2002.

Mr. Oser’s main areas of expertise are chemistry, pharmaceuticals and life science.

His practice includes patent prosecution (drafting, examination), opposition and appeal proceedings, patent litigation, infringement and validity opinions, freedom-to-operate analyses and due diligence examinations.

Prüfer & Partner mbB
Sohnckestrasse 12, 81479 München
Tel. +49 89 69 39 21 0, E-Mail,

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