Patents and Plausibility - G2/21 Syngenta Ltd v Sumitomo Chemical Co. Ltd.
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Enlarged Board of Appeal (C. Josefsson, I. Beckedorf, F. Blumer, T. Bokor, P. Catallozzi, P. Gryczka and A. Ritzka) G 0002/21 Syngenta Ltd v Sumitomo Chemical Co. Ltd 23 March 2023
European patent No. 2 484 209 ("the patent") has been granted to Sumitomo Chemical Co. Ltd. ("Sumitomo") for a mixture of thiamethoxam and other compounds in accordance with a formula disclosed in the specification. That mixture produces an insecticidal activity that is greater than would be achieved by any of those compounds administered on its own ("the invention"). Syngenta Limited ("Syngenta") objected to the patent on the grounds that the invention was not new or obvious, that it had not been properly disclosed and it included added matter.
The European Patent Convention ("EPC") provides a procedure for the revocation of a patent known as "opposition." Art 99 (1) of the EPC enables anybody who objects to a patent to give notice of opposition to the European Patent Office ("EPO") within 9 months of the grant. The grounds for opposition are set out in art 100:
"(a) the subject matter of the European patent is not patentable under Articles 52 to 57;
(b) the European patent does not disclose the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art;
(c) the subject matter of the European patent extends beyond the content of the application as filed, or, if the patent was granted on a divisional application or on a new application filed under Article 61, beyond the content of the earlier application as filed."
Oppositions are considered by an organ of the EPO known as an "Opposition Division" (see art 19 (1) of the EPC). A party that is dissatisfied with a decision of an Opposition Division may appeal to a tribunal established by art 21 known as a "Board of Appeal". If a Board of Appeal requires guidance on a point of law it may refer the point to an Enlarged Board of Appeal pursuant to art 22 (1) (a) and art 112 (1). There is no equivalent to opposition in the UK Patents Act 1977.
Syngenta opposed the grant under art 99 on all the grounds in art 100. The Opposition Division rejected the opposition so Syngenta appealed to the Technical Board of Appeal. The appeal came on before the Board (M. O. Müller, A. Lenzen and P. de Heij) on 11 Oct 2021. The case is referred to as T 0116/18.
The Technical Board was satisfied that there had been sufficient disclosure of the claimed invention. It decided that the question of whether any synergy could be achieved should be assessed under art 100 (a) and art 56 of the EPC rather than art 100 (b). In respect of want of novelty, the Board was satisfied that none of the prior art disclosed by the opponent had anticipated the invention. As for obviousness, the Board reasoned that the assessment of the inventive step of the subject matter of the patent hinged on whether evidence not published before the filing date of the patent and made available after that date could be taken into consideration in view of the so-called plausibility case law. That was because the patentee relied on evidence that had come to light after the publication of the patent application. Both parties lodged opposing requests as to whether such evidence should be taken into consideration.
As there were conflicting lines of authority on the issue, the Technical Board referred the following questions to the Enlarged Board of Appeal:
"If for acknowledgement of inventive step the patent proprietor relies on a technical effect and has submitted evidence, such as experimental data, to prove such an effect, this evidence not having been public before the filing date of the patent in suit and having been filed after that date (post-published evidence):
2. If the answer is yes (the post-published evidence must be disregarded if the proof of the effect rests exclusively on this evidence), can the post-published evidence be taken into consideration if, based on the information in the patent application in suit or the common general knowledge, the skilled person at the filing date of the patent application in suit would have considered the effect plausible (ab initio plausibility)?
3. If the answer to the first question is yes (the post-published evidence must be disregarded if the proof of the effect rests exclusively on this evidence), can the post-published evidence be taken into consideration if, based on the information in the patent application in suit or the common general knowledge, the skilled person at the filing date of the patent application in suit would have seen no reason to consider the effect implausible (ab initio implausibility)?"
However, there are circumstances when the issue becomes relevant. As Lord Sumption explained in para  of Warner-Lambert Company LLC v Generics (UK) Ltd (t/a Mylan) and another  UKSC 56,  Bus LR 360, (2019) 165 BMLR 14,  RPC 21,  3 All ER 95:
"The main problem about this result is that it would enable a patent to be obtained on a wholly speculative basis. Without some disclosure of how or why the known product can be expected to work in the new application, it would be possible to patent the manufacture of known compounds for the purpose of treating every conceivably relevant condition without having invented anything at all, in the hope that trial and error might in due course show that the product was efficacious in treating at least some of them."
The EPO is aware of this problem. In fact, Lord Sunmption said at para  of his judgment that "the concept of plausibility originates in the case law of the EPO as a response to over-broad claims, in particular claims to whole classes of chemical compounds supported by a description which fails to show which compounds can be expected to work."
The Enlarged Board of Appeal took question 1 of the Technical Board's questions first. After reviewing its case law and the rules of evidence in the courts of England and Wales, France, Germany, the Netherlands and Switzerland the Board held at para 55 of the reasons that the principle of free evaluation of evidence qualifies as a universally applicable principle in assessing any means of evidence by a board of appeal. There was one important exception to this "universally accepted principle" in that the principle of free evaluation of evidence does not exist in England's common law system. Nevertheless, in view of the adoption of the principle just about everywhere else, the Board concluded at para 56 that:
"An effect could not be validly used in the formulation of the technical problem if the effect required additional information not at the disposal of the skilled person even after taking into account the content of the application in question...."
"A patent applicant or proprietor may rely upon a technical effect for inventive step if the skilled person, having the common general knowledge in mind, and based on the application as originally filed, would derive said effect as being encompassed by the technical teaching and embodied by the same originally disclosed invention."
The Enlarged Board does not function as a court of appeal in cases such as this. It is much more like the Court of Justice of the European Union when determining an issue of EU law upon a preliminary reference from a national court pursuant to art 267 of the Treaty on the Functioning of the European Union. In due course, the appeal against the Opposition Division's decision will go back to the Technical Board of Appeal. In deciding this appeal the Technical Board is likely to have something to say about the plausibility of the invention in relation to whether it involves an inventive step.
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