“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 frequent debate 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 a Turkish wording for an equivalent legal term.

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

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 under Turkish law, is a particularly relevant issue for pharmaceutical patents. However, it is difficult to obtain all the clinical test data by the patent application date due to the long duration and complexity of efficacy tests.

Therefore, considering the inherent urgency of patent applications, 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.

A similar effect to that of this requirement can be achieved in invalidation actions by asserting in the context of “sufficiency of disclosure” or “lack of inventive step” despite the lack of any such requirement in the Agreement on Trade-Related Aspects of Intellectual Property Rights or the European Patent Convention, to which Turkey is a party.

Indeed, arguments including the concept of plausibility before the intellectual and industrial rights law courts did so under both headings.

EPO Case law on Plausibility

The concept of plausibility is also associated with inventive step and sufficiency of disclosure in EPO case law. Even though 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.

Others argue that 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.

Turkish Case Law Regarding the 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, a 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 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 their 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. No evaluation was made regarding the plaintiff’s plausibility argument and therefore no steps were taken to form case law on plausibility.

Unifying EPO Case Law Will Be Instructive to Turkish Courts

The current state of IP law in Turkey does not allow for advanced plausibility arguments or for the recruitment of case law as a criterion in plausibility evaluations to be made by the courts.

However, despite the fact that EPO case law does not constitute a direct precedent for Turkish courts, in our opinion, the decision issued regarding the G 2/21 application by the EPO Enlarged Board of Appeal following the oral hearing held on November 24, 2022, will help to establish a uniform approach to applications by that Turkish courts may follow, especially considering that Turkey is a party to the European Patent Convention. In this context, we believe that there will be a clearer practice before Turkish courts when the patent owner relies on the post-published evidence to support the inventive step criteria of the patent.  However, the determination of the Enlarged Board that the question of whether or not an invention is sufficiently disclosed when post-published evidence is used in support of a technical effect should be evaluated on a case-by-case basis did not, of course, remove the uncertainty before the Turkish courts' assessments.  

The industry is very excited to see the reflections of the decision of the EPO Enlarged Board of Appeal in Turkish IP law.

First published by ManagingIP in Jan 04, 2023.

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