The intertwined concepts of plausibility and post-published evidence in relation to sufficiency and inventive step have become embedded in European patent practice over the years. The concept originates with the 2005 Board of Appeal decision T1329/04, which held that, firstly, for inventive step to be recognised, the patent application must at least make plausible that the problem addressed by the invention is solved; and secondly that post-published data confirming that the problem has been solved can be used in evidence, but if the initial plausibility threshold is not met, then this data should not be taken into account. For a recent example where these concepts are applied, see our article on T2015/20, concerning the treatment of asthma.

However, some case law suggests that the plausibility threshold may not be such a high bar to meet - T0578/06 held that plausibility is only relevant when the particular case supports doubts over whether the claimed invention is solved. In other words, is the solution actually implausible.

Now, in decision T0116/18, the Enlarged Board of Appeal has been asked to rule on this difference in approach. The patent in question, EP 2 484 209 to Sumitomo Chemical Company Ltd, is directed to combination insecticides which are said to be synergistic, with claim 1 referring to a combination of thiamethoxam and one or more compounds represented by a general formula. The patent itself does include experimental data showing synergy, but of only two examples covered by the claims, and against two moth species. During opposition, the opponent submitted data intended to show that a combination within the scope of claim 1 did not show synergy against one of these species or against one closely-related species. The patentee criticised this data, and submitted their own post-published data showing that the combination was indeed synergistic against various species. The patent survived opposition, with the EPO accepting that this data confirmed the presence of synergy, and hence an inventive step.

On appeal, the question of plausibility and post-published evidence was again critical for the case.  The Board considered, firstly, whether the patentee's post-published evidence was relevant for the assessment of inventive step. The Board took the view that, considering only the prior art, the two examples in the patent, and the opponent's evidence that some combinations are not synergistic, the objective technical problem to be solved would be formulated as "providing an alternative insecticide composition", and the claims as granted would not be considered inventive. When the patentee's evidence was considered, however, a more specific objective technical problem was formulated - namely provision of an insecticide composition which acts synergistically against a particular insect species. The Board considered that this problem was solved by the patent, and so the claims would be considered inventive.

Hence, the question of whether this post-published evidence can be taken into account would be critical for deciding on inventive step. Further, in view of the plausibility versus implausibility approaches both found in the case law, the Board considered that it is necessary for the Enlarged Board to provide a ruling on the correct approach to apply. As the Board note, the two can result in very different outcomes; particularly so when the technical problem, as here, is reformulated in light of the prior art.

The decision also contains useful points on the admittance of late-filed evidence before the Boards of Appeal generally on procedural grounds, rather than substantive grounds.

We await the decision of the Enlarged Board of Appeal with interest.

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