Sumitomo Chemical v Syngenta (EPO, G 2/21, 2023)

Dhenne Avocats · 11 October 2026

Our analysis

Summary

On a referral from Technical Board of Appeal 3.3.02, the Enlarged Board of Appeal of the EPO held that evidence filed by an applicant or proprietor to prove a technical effect relied on for inventive step may not be disregarded solely because it was not public before the filing date and was filed after it (Order, point 1). The proprietor may rely on such an effect if the skilled person, with the common general knowledge in mind and based on the application as originally filed, would derive it as encompassed by the technical teaching and embodied by the same originally disclosed invention (Order, point 2). « Plausibility » is not a distinct requirement of patentability (point 92). The decision sets the framework for post-published data on inventive step and confirms that such data play a far narrower role for sufficiency, notably for second medical use claims (point 77).

Facts and procedure

Sumitomo Chemical’s European Patent No 2 484 209, which derives from a divisional application, concerns insecticide compositions combining thiamethoxam with compounds of formula Ia, to which the patent attributes a synergistic effect (points II and VI). Syngenta’s opposition on all grounds under Article 100 EPC was rejected and the opponent appealed (points IV and V). The Board accepted sufficiency and novelty but found that inventive step turned on whether the proprietor’s post-published test data D21, the only proof of synergy, could be taken into account, having itself admitted the opponent’s post-published data D23 (point VI). By interlocutory decision T 116/18 of 11 October 2021, it referred three questions to the Enlarged Board (point I).

The applicable law

The Enlarged Board started from Article 56 EPC and the problem and solution approach, under which the proprietor must show that the purported advantages are achieved (points 24 to 26). It restated the principle of free evaluation of evidence, already affirmed in G 3/97, G 4/97 and G 1/12, rooted in the right to give evidence under Articles 113(1) and 117(1) EPC and shared by the civil law Contracting States, which Article 125 EPC brings into play (points 29 to 53). It then reviewed the Boards’ case law on inventive step (points 60 to 72) and on sufficiency (points 73 to 77), followed by national case law (points 78 to 87).

Question

Must post-published evidence filed by the proprietor as the sole support for a technical effect relied on for inventive step be disregarded, by way of exception to the principle of free evaluation of evidence, and if so, may it nonetheless be considered where the skilled person would have found the effect plausible, or would have seen no reason to find it implausible, at the filing date (point I)?

Decision

The principle of free evaluation of evidence applies universally (point 55) and cannot be used to disregard, as a matter of principle, evidence that is filed and decisive, since that would deprive the party of the right enshrined in Articles 113(1) and 117(1) EPC (points 32 and 90). Post-published evidence therefore cannot be disregarded solely on account of its date (points 56 and 91). Plausibility is neither a distinct legal concept nor a specific requirement under Articles 56 and 83 EPC (point 92); it describes a criterion for relying on a contested technical effect (point 58). Whatever the terminology, the common ground in the Boards’ case law is what the skilled person, at the filing date, would understand from the application as originally filed as the technical teaching of the invention (points 71 and 72). The effect relied on, even at a later stage, must be encompassed by that teaching and embody the same invention, since it does not change the nature of the claimed invention (points 93 and 94). For sufficiency, the scope for post-published evidence is much narrower: proof of a claimed therapeutic effect must be provided in the application as filed, and a deficiency cannot be remedied by post-published evidence (point 77). The Enlarged Board acknowledged the abstract nature of these criteria, whose application depends on the circumstances of each case and the technical field (point 95).

Key points for practice

• Post-published data remain admissible to establish a technical effect for inventive step; their date alone is no ground for disregarding them (Order, point 1).
• The decisive yardstick is the technical teaching of the application as originally filed, read by the skilled person with the common general knowledge (points 93 and 94).
• For a second medical use claim, the therapeutic effect is a feature of the claim, examined under sufficiency, and must be made credible by the application itself (points 74 and 77).
• Practical point: the application should set out the technical effects that may later be relied on, since post-published evidence can only establish an effect already encompassed by the original teaching (points 93 and 94).

Provisions applied

European Patent Convention

Art. 52; Art. 56; Art. 83; Art. 112; Art. 113; Art. 117; Art. 125

Other provisions

Rules of Procedure of the Boards of Appeal (RPBA 2020), Art. 22

Case law cited

EPO, G 3/97, G 4/97, G 1/12, G 2/08, G 1/03; T 116/18 (referring decision), T 609/02, T 1329/04, T 488/16, T 578/06, T 1599/06, T 760/12; Warner-Lambert v Generics, [2018] UKSC 56; Sandoz v Bristol-Myers Squibb, [2022] EWHC 822 (Pat); Court of Appeal The Hague, Leo Pharma v Sandoz (200.195.459/01); BGH, Anthradipyrazol (X ZB 3/69); Swiss Federal Supreme Court, 4A_149/2021

Related decisions

• T 609/02, Salk Institute, EPO, 27 October 2004, cited on sufficiency for second medical use claims (point 75).
• T 1329/04, Johns Hopkins University, EPO, 28 June 2005, cited on assessing inventive step at the effective date (point 23).
• T 488/16, Bristol-Myers Squibb v Apotex, EPO, 1 February 2017, cited among the decisions disregarding post-published evidence (point 61).
• Warner-Lambert v Generics, UK Supreme Court, 14 November 2018, cited on post-published evidence for sufficiency (point 85).

Prepared by Dhenne Avocats from the text of the decision (EPO Official Journal 2023, A85, epo.org, English version), consulted on 11 October 2026. Only the official text is authoritative.