The EPO provides further guidance on plausibility – T184/16


Plausibility is frequently debated at the EPO in the context of both sufficiency and inventive step. Typically, the EPO considers a patent application to be lacking in plausibility if the patent application in question is considered to contain overly speculative claims that, at the time of filing, were based purely on assertion.

Plausibility is determined upon the information contained in the patent application, as well as the common general knowledge and prior art available at the time of filing. An applicant therefore needs to strike a careful balance between obtaining an early filing date and potentially risking the patent application lacking plausibility, or filing the application at a later stage but with experimental data demonstrating the plausibility of the claims contained.

In the recent decision T184/16, further guidance is provided on the EPO’s plausibility requirement.

Background of the case

The patent, EP1651658, upheld in amended form following proceedings before the opposition division, claims a compound having an inhibitory effect against sodium-dependent glucose transporters (SGLT) present in the intestine or kidneys. Owing to this inhibitory effect, the compounds can be used in the treatment of diabetes-related conditions.

The appellant contested the decision of the opposition division and argued that the claims were insufficiently disclosed and did not involve an inventive step. The arguments put forward by the appellant centred on the absence of data in the patent, with the appellant concluding that owing to the alleged lack of data, the patent lacked plausibility.


The Board stated that to acknowledge the plausibility of a technical effect relied on in an application, then plausibility must be judged on the basis of the disclosure in the application as filed taking into account the common general knowledge and prior art available on the filing date of that application.

The Board acknowledged that the application in question did not contain any experimental evidence with regard to the disputed plausibility. As a consequence, the Board assessed plausibility in view of the common general knowledge and prior art available at the date of filing.

The application as filed contained references to post-published evidence. Upon considering the post-published evidence, the Board decided that the patent was plausible. As explained in the decision, owing to the post-published evidence referring to compounds with the same core structure as the compounds recited in the patent as being SGLT inhibitors, then it is plausible that a skilled person would consider the claimed compounds as SGLT inhibitors. The patentee was therefore able to rely on post-published evidence to show that the claimed compounds were indeed SGLT inhibitors, without including any data in the patent itself demonstrating the inhibitory effect. Thus, it was possible for the patentee to rely solely on common general knowledge and prior art to demonstrate plausibility.

The Board applied a different criterion for assessing inventive step. To assess inventive step, the Board decided that it was not sufficient that a prior art document discloses compounds with the same core structure with a similar effect, the prior art document must actually suggest the solution to the objective technical problem. The Board decided that, owing to the prior art not teaching the solution, it would not have been obvious to a skilled person to modify the teaching of the prior art to arrive at the claimed compounds.


The Board found that the patent in amended form was allowable.

In reaching their decision, the Board confirmed that the criteria for assessing plausibility and inventive step are different. Plausibility of a claimed effect can be acknowledged on the basis of the common general knowledge and the prior art. On the other hand, the problem and solution approach is used to decide inventive step. As stated by the Board, it must be considered whether the claimed solution is suggested, and therefore made obvious by the prior art.