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    “Plausibility” in Turkish Patent Law and Its Impact on Invalidation Proceedings

    The grounds for the invalidation of a patent within the scope of Industrial Property Law No. 6769 are listed per the numerus clausus principle. The concept of plausibility – which has been the subject of numerous evaluations, especially by the European Patent Office (“EPO”) and frequently debated in academic circles in recent years – has not yet found a place within the scope of any legal regulation in Turkey. Moreover, there is no consensus on the Turkish wording that meets this concept as a legal term.

    However, the concept of plausibility has started to be argued by the plaintiffs in Turkish invalidity proceedings and has been the subject of important conclusions by the EPO Enlarged Board of Appeal within the scope of application No. G 2/21, so the place of the concept of plausibility in Turkish legal practice must be scrutinized.

    Plausibility can be defined as the ability to demonstrate the technical effect claimed by the invention credibly and convincingly with appropriate evidence to be submitted or to deduce this situation from the state of the art or common general knowledge to avoid speculative patents that can be produced at the desk (Türk Patent Hukuku, Uğur Çolak, Adalet Yayınevi, Ankara, 2022; A Practitioner’s Guide to European Patent Law, Paul England, Hart Publishing, London, 2019).

    The requirement of plausibility, which is not defined as one of the invalidation grounds in the law, is particularly an issue concerning pharmaceutical patents. However, not all the test data of clinical studies may be obtained by the patent application date due to the long duration of efficacy tests and their complicated processes.

    Therefore, considering the necessity of making a patent application as soon as possible to avoid any loss of rights, there are issues around how much data indicating that the invention is applicable and working should be included in the patent application and to what extent post-published evidence can be used.

    In other words, the concept of plausibility can be regarded primarily as a prohibition of speculative patent applications which do not disclose a technical effect of a chemical substance and/or disclose a technical effect which is not normally expected.

    Although the lack of this requirement is not one of the invalidation grounds stipulated in Turkish legislation, in the Agreement on Trade-Related Aspects of Intellectual Property Rights or the European Patent Convention, to which Turkey is a party, it can be alleged in invalidation actions by asserting in the context of “sufficiency of disclosure” or “lack of inventive step”.

    Indeed, where the concept of plausibility has been used as an invalidation ground before the intellectual and industrial rights law courts, the allegations on this issue were included under both headings.

    EPO Case Law on Plausibility

    The issue of plausibility is also associated with inventive step and sufficiency of disclosure in the case law created before the EPO. Although given that the word “credible” was used instead of “plausible” in Case T 939/92 (AgrEvo), there are opinions claiming that this decision, which concluded that a technical effect should be reasonably predictable and credible, was the first to use the threshold of plausibility.

    However, according to the contrary views, Case T 1329/04 (John Hopkins) was the first to establish the plausibility threshold in explaining that it was at least made plausible that the claimed invention could be carried out.

    In contrast to these cases, Case T 609/02 (Salk) concerned the plausibility threshold about the sufficiency of disclosure, and it was concluded that there was a requirement to make the existence of a cause-and-effect relationship plausible.

    Finally, in a more recent case, T 488/16 (Dasatinib/BRISTOL-MYERS SQUIBB), the EPO Enlarged Board of Appeal clarified that even though there is not always a requirement to have experimental data in an application, the technical problem must at least shown to be plausibly solved at the filing date.

    The plausibility issue also raises a discussion regarding filing post-published documents. It is seen that there are many decisions of EPO Technical Boards of Appeal (see, in particular, T 578/06) addressing the plausibility issue together with evidence published after the date of filing. The majority of the decisions stress that post-published evidence can be considered on the condition that a certain effect was plausible at the filing date of the patent application. In that situation, post-published documents can be accepted.

    Case Law of Turkish Courts Regarding Plausibility Principle

    Given that the concept of plausibility is only just gaining currency in Turkish law and that it has not been put forward as a sound argument by plaintiff parties, it has not yet been included in any high court case law and has not been evaluated in any decision by a court of first instance.

    Indeed, the plaintiff claimed in a recent patent invalidation action that the subject patent was not plausible in the context of insufficient disclosure. However, the plausibility requirement was erroneously defined because of the presence of all the evidence in the patent document that directly and undoubtedly proved that the technical problem had been resolved. However, according to the EPO’s practices, for example, the submission of in vitro test results may be sufficient to make the solution to the technical problem foreseen in the patent plausible. In this respect, since the plaintiff could not prove its claim in accordance with the general principles of the law of proof, the court of first instance concluded that the invention was entirely and sufficiently disclosed to allow the implementation of the invention by the technical expert. No evaluation was made regarding the plaintiff’s plausibility argument; therefore, no steps were taken to form case law on plausibility.

    Unifying EPO Case Law Will Be Instructive to Turkish Courts

    At the point reached in the practice of intellectual property law today, it is not possible to talk about advanced plausibility arguments having been put forward or argue that case law can be used as a criterion in the plausibility evaluations to be made by the courts has been established.

    However, the decision to be issued regarding the G 2/21 application by the EPO Enlarged Board of Appeal following the oral hearing held on November 24 2022, is expected to bring about essential standards regarding the requirement of plausibility and addresses important questions about whether post-published documents should be taken into account in the examination of plausibility, and will have significant repercussions in the patent world. It would not be wrong to say that the effects of this decision will be seen in Turkey as well.

    While no case law can be taken as a precedent in national legal practice given that Turkey is a party to the European Patent Convention, in our opinion, the G 2/21 decision will help to establish a uniform approach to applications by constituting a direct precedent for Turkish patent law.

    The industry is very excited to see the written decision of the EPO Enlarged Board of Appeal, which will bring enlightenment to pending disputes in different types of jurisdictions.


    Tagged withGün + Partners, Selin Sinem Erciyas, Aysel Korkmaz Yatkın, Aysu Eryaşar, Intellectual Property

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