European Patent Office (EPO) level of disclosure required for antibodies - first medical use


As a complement to the 10th edition of the EPO "Case Law of the Boards of Appeal" (CLB), the EPO has published an Annual Review containing summaries of decisions from 2022. The review provides a thematic overview of selected decisions of the Boards of Appeal published in 2022. There are a number of notable decisions in the summary, although it has been a somewhat quiet year for significant decisions in the antibody area.  Most decisions in this technical area consolidate what is now fairly settled practice at the EPO for antibody cases, where inventive step continues to be a major challenge. This consolidation is in part due to the uniformity introduced by the new antibody section of the EPO Guidelines G-II 5.6  (introduced in 2021 and revised in 2022) as discussed in our earlier article here. The only antibody-related decision in the 2022 Annual Review is T 424/21 concerning the level of disclosure required for a first medical use claim for an antibody ("antibody X for use as a medicament").


When the technical effect is expressed in a claim, as it is in medical use claims, the issue of whether this effect is indeed achieved over the whole scope of the claim is a question of sufficiency of disclosure under Article 83 EPC.

The level of disclosure required for antibodies  is not discussed in the EPO Guidelines G-II 5.6 but rather is covered in the CLB. The current CLB, II.C.7.3 relating to antibodies addresses the level of disclosure required under Article 83 EPC for medical use claims but does not specifically mention first medical use claims.  Second medical use claims are however mentioned in the context of T 760/12 whereby the therapeutic effect was expressed in the claim ("Swiss-type" format and purpose-restricted product claim format). The Board in T 760/12 decided that for a second medical use claim, unless this is already known to the skilled person at the priority date, the application must disclose the suitability of the product to be manufactured for the claimed therapeutic application. The Board in T 760/02 concluded that it was not sufficiently disclosed in the patent that a single monoclonal antibody as defined in the claim potentially exerted the therapeutic effect as claimed.

First medical use claims are specifically referenced elsewhere in the CLB at section I.C7.1.1 where it is stated in general terms in the context of novelty that according to the case law of the Boards of Appeal, the first to show a use of a substance or composition in a medical method should receive broad protection covering any use in a medical method, even if only one specific use is disclosed in the application (see T 128/82, OJ 1984, 164; T 36/83 OJ 1986, 295).

T 424/21

The claim at issue in T 424/21 concerned an “antibody or an Fc fusion protein comprising an Fc variant of a wild-type human IgG1 Fc region”. The examples in the patent showed that the mutated antibodies bind to their antigen targets and are therapeutically effective. The Board saw no general issue of sufficiency of disclosure for a broad first medical use claim and did not see the need for the inventor to "restrict himself ... to a specified therapeutic purpose". The Board could not derive any requirement from the EPC whereby a patent would have to show that a compound was suitable for each and every disease in order for a first medical use to be sufficiently disclosed (Reasons 40). Instead, it was sufficient to show that the compound was suitable for at least one particular medical use, as was the case in the patent at issue.

The Board distinguished over T 604/04, where sufficiency of disclosure of a claim to a monoclonal antibody "for use in therapy or diagnosis", i.e. a first medical use, was denied because "the mere disclosure of a monoclonal antibody against the polypeptides of Figure 4 or 5 without identifying a diseased state caused by the 'misfunctioning' of these polypeptides is not sufficient to acknowledge a use in therapy for the monoclonal antibody" (Reasons 25).


This decision confirms existing EPO practice that the first to show a use of a substance or composition (in this case an antibody) in a medical method should receive broad protection covering any use in a medical method, even if only one specific use is disclosed in the application. The decision provides a clear finding that, in these circumstances, the requirements of Article 83 EPC will be considered to be met. Whilst this decision is positive for applicants, it can be contrasted with the requirement under Article 83 EPC “that the skilled person can put the invention into practice over the whole scope of the claim” (CLB II.C.7.1.2).

The EPO’s somewhat generous approach to Article 83 EPC for first medical use claims is in line with the similarly generous approach to basis under Article 123(2) EPC for such claims whereby disclosure of one therapeutic application will, in practice, typically be accepted by examiners as basis for a first medical use claim. Again, this can be contrasted with the gold-standard assessment under Article 123(2) EPC of what a skilled person would derive directly and unambiguously, using common general knowledge.

Whilst applicants can guard against falling foul of Article 123(2) if there is a change in practice at the EPO by drafting their patent applications to contain explicit language for a first medical use claim, guarding against a future attack under Article 83 EPC of a first medical use claim in the event of a change in practice will be more difficult. If there are technical reasons e.g., available from the art as to why it is plausible that the claimed product is suitable for more than one therapeutic application, then applicants should consider including these reasons in the patent application at the time of drafting. Second medical use claims reciting specific therapeutic indications should also be included. In the meantime, at least in the context of first medical use claims, the EPO is happy to grant broad claims.