Amicus curiae brief for case G 1/25 before the Enlarged Board of Appeal

The Life Sciences Committee (‘LSC’), with support from the Patents Committee, submitted an amicus curiae brief in case G1/25 before the Enlarged Board of Appeal of the European Patent Office. The case sought to resolve conflicting case law on whether inconsistencies between the description and claims are permissible. An LSC working group was set up in October 2025, where it was agreed that post-grant claim amendments should not generally require a change in the description. Due to differing perspectives between those practising in the life sciences and chemical fields and those working primarily in mechanical fields, the working group (led by LSC member Alice Wales with support from other LSC members Joel Beevers, Lawrence Cullen, Simon Kremer, Marion Rees and Sheila Wallace) prepared a balanced brief to reflect these views. The amicus curiae was submitted to the EPO on 30 January and can be read here.

Executive Summary

CIPA’s view on the referred questions may be summarised as follows:

Question 1:     Where a post-grant claim amendment introduces an inconsistency between the description and the claims of a granted European patent, adaptation of the description to remove the inconsistency is not generally necessary to comply with the requirements of the EPC. The burden of proof for establishing that adaptation of the description is necessary in any such case rests with the person who alleges such necessity.

Question 2:     Since the first question is not answered in the affirmative, no answer is required. The EPC does not include a universal requirement which always necessitates adaptation of the description in the circumstances of referred question 1.

Question 3:     The answers above apply equally in the case of pre-grant amendment to the claims of a pending European patent application.

Question 1

1.1        Referred question 1 pertains in general terms to cases in which a post-grant amendment to the claims gives rise to an inconsistency with the description. Any such inconsistency is identifiable when the amended claims are interpreted with reference to the description to examine their compliance with the requirements of the EPC (G1/24).

1.2        Such a claim amendment may, on examination, be found to contravene the requirements of the EPC:

1.2.1    Adding a feature to the claims that is at odds with the technical teaching of the description will violate Article 123(2) EPC if this feature was not directly and unambiguously disclosed in the patent application as filed.

1.2.2    Deleting a claim feature which has from the outset been unequivocally characterised as essential in the description may contravene Article 83 and/or Article 123(3) EPC.

1.2.3    Subject to the restrictions outlined in Decision G 3/14, deploying a technical term in the claims in a manner which appears contradictory to its consistent usage in the description may engender a lack of clarity which is objectionable under Article 84 EPC.

1.3        In such cases, an objection will be levelled against the claims.  Where the amended claims fail to meet the requirements of the EPC, adaptation of the description to the claims will not come into question. Such adaptation is not necessary and is typically impermissible.

1.4        From this analysis, it becomes clear that in practice, referred question 1 arises only when the amended claims are judged, on examination, to be in principle allowable; that is, where no substantive objections are levelled against the amended claims under the provisions of the EPC. Referred question 1 asks whether, in these circumstances, the description must be adapted to the allowable claims to remove the introduced inconsistency before a decision can be taken to maintain the patent.

1.5        CIPA advocates that in such cases:

1.5.1    It is not generally necessary for the description to be adapted to the allowable set of amended claims in order to remove the inconsistency introduced by the claim amendment.  Neither law nor policy supports a universal requirement for adaptation of the description in these circumstances.

1.5.2    The need for adaptation of the description in any specific case must be determined on a case-by-case basis with reference to the specific facts and circumstances of the case, including the nature and effect of the inconsistency.

1.5.3    The burden of proof for establishing that adaptation of the description is necessary in any such case rests with the person who alleges such necessity.

1.6        Adaptation of the description in the specified circumstances is not generally necessary, because the mere fact of an inconsistency between an allowable claim set and the description does not violate the requirements of the EPC.

1.6.1    The EPC formally establishes the claims and description as distinct documentary elements of the patent (Article 78 EPC).  The claims and description are subject to different formalities and linguistic conventions (Rules 42 and 43 EPC).  They each perform a unique role in the patent.  Specifically, it is the exclusive statutory function of the claims to clearly define the matter for which patent protection is sought, whilst the description must support the claims (Article 84 EPC).

1.6.2    Given these well-recognised differences in nature, purpose and content, a formal mismatch (inconsistency) between the claims and description is not in principle objectionable under the EPC, provided that all the applicable statutory requirements are met.

1.6.3    There are no good policy reasons for establishing a universal requirement for adaptation of the description in the specified circumstances.  The public interest is not harmed by the maintenance of patents which meet the existing requirements of the EPC.  The patentee’s interests will, on the other hand, be substantially harmed by the imposition of an additional onerous requirement which is not justified by the law.

1.7        The need for adaptation of the description in any specific case, in order to meet the requirements of the EPC, must be determined on a case-by-case basis with reference to the specific facts and circumstances of the case, including the nature and effect of the inconsistency.

1.7.1    It may be the case that in certain unusual and fact-specific scenarios, adaptation of the description to the claims could arguendo be essential in order to meet the requirements of the EPC.  For example, if the claims of a patent were to be limited by amendment to specific embodiments which, owing to previous limiting description amendment, are no longer mentioned in the description, then it is possible that the adaptation of the description to the amended claims, such as by reinstating the deleted examples, could be judged necessary in order to meet the requirements of Article 83 EPC.

1.7.2    However, in cases where the claims are limited by allowable amendment to exclude embodiments which remain in the description, there is no general principle why adaptation of the description should be judged necessary to meet the requirements of the EPC, including those of Article 84 EPC.  The presence of unclaimed subject matter in the description will not in principle cast doubt on the scope of the allowable claims, since the reader knows that it is the claims and not the description which define the protection sought by the patent.  Indeed, the mention of unclaimed alternatives in the description may positively assist the reader in better understanding the allowable claims, whilst also supporting the claims. In these circumstances, the requirements of the EPC, including those of Article 84 EPC, should be judged to be met without adaptation of the description.  It should be the preserve of the applicant/patentee to determine whether to delete such unclaimed alternatives, particularly in light of divergent practices in European litigation.

1.8        The burden of proof for establishing that adaptation of the description is necessary rests with the person who alleges such necessity.

1.8.1    According to principles of fair treatment followed by the EPO, the burden of proof for establishing any objection lies with the person who brings that objection (Guidelines, G-IV 7.5.3). This principle provides an important safeguard for the interests of the patentee, whose freedom of action and expression should be constrained only in line with the law.  Accordingly, any call for the mandatory adaptation of the description must be reasoned and substantiated and must show, on the balance of probabilities, that such adaptation is necessary to meet the requirements of the EPC.  In view of the lack of a general principle requiring amendment of the description, we believe that such cases will be relatively rare.

Question 2

Since the first question is not answered in the affirmative, no answer is required. The EPC does not include a universal requirement which always necessitates adaptation of the description in the circumstances of referred question 1.

Question 3

The answers above apply equally in the case of pre-grant amendment to the claims of a pending European patent application.