Must the description of a European patent be consistent with patent claims amended pursuant to an opposition? The EPO’s Enlarged Board of Appeal is to tackle this question in case G1/25 for which 39 amicus curiae briefs have been submitted.

At the European Patent Office (EPO), an amicus curiae brief is a written submission from a non-party such as industry or practitioners’ associations, or legal scholars offering expert, neutral, or interested viewpoints on legal issues in cases pending before the EPO’s Enlarged Board of Appeal (EBoA).

In particularly significant cases, the EPO invites third parties to submit amicus curiae briefs within a set deadline.

One of such cases is G1/25 before the EBoA, arising from appeal proceedings in case T697/22 before the EPO’s Technical Board of Appeal.

The case concerns Rockwool’s opposition against a European patent application filed by Knaus Insulation for a hydroponics plant growth medium. The patent claims were amended as a result of the opposition, but a further dispute arose as to whether the patent could be granted without the description being adapted to reflect the amendment of the claims.

The questions referred to the EBoA are as follows:

• If the claims of a European patent are amended during opposition proceedings or opposition-appeal proceedings, and the amendment introduces an inconsistency between the amended claims and the description of the patent, is it necessary, to comply with the requirements of the European Patent Convention (EPC), to adapt the description to the amended claims so as to remove the inconsistency?
• If the first question is answered in the affirmative, which requirement(s) of the EPC necessitate(s) such an adaptation?
• Would the answer to questions 1 and 2 be different if the claims of a European patent application are amended during examination proceedings or examination-appeal proceedings, and the amendment introduces an inconsistency between the amended claims and the description of the patent application?

With the deadline of 30 January 2026 for submissions expired, the EP register now lists a total of 39 briefs received from AIPLA, Bardehle Pagenberg, Bayer AG, BIA (UK BioIndustry Association), Bugnion, Canon Inc., CIPA, CPI, D.X. Thomas, EFPIA, EP&C Patent Attorneys, EPI, EPO President, Ericsson, ETH Zurich, FEMIPI, FICPI, Francis Hagel, Greenwoods, GRUR, IP Federation, IPO (Intellectual Property Owners Association), “Jackson Lamb”, Japan Intellectual Property Association, JEITA, Martin Wilming, Michael Stadler et al, Michael Snodin, Ordine Dei Consulenti in Proprietà Industriale, Patentanwaltskammer, Patentwerk B.V., Peter De Lange, Richardt Patentanwälte, Roche, Roy Marsh, Samson & Partner (Apple Inc.), Siemens, UNION and VPP.

Based on the answers provided, it can be said that the majority of briefs suggest that the description should not be amended and therefore questions 1 and 3 should be answered in the negative (and question 2 be disregarded).

The EBoA will now set to work on examining the briefs, which of course are in no way binding, and proceed to issue a decision. We will continue to follow this interesting case closely.

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