7.3. Level of disclosure required for antibodies

In T 431/96 the skilled person seeking to reproduce the invention would have had to produce monoclonal antibodies by routine methods and test them singly in an assay. Although this might possibly involve some tedious and time-consuming work, it was nothing out of the ordinary since the techniques for the production and selection of hybridomas were common routine techniques at the priority date of the patent in suit.

In T 435/20 the board acknowledged by reference to T 431/96 that raising and screening antibodies involved only routine experimentation. However, this was ony the case if the skilled person knew from the disclosure in the patent or from common general knowledge (i) which antigens were suitable for raising antibodies having the desired properties and (ii) which screening processes should be used to select these antibodies without undue burden. In decision T 435/20 the board said that the conclusion reached in decision T 431/96, that the generation of antibodies to known antigens was routine, did not apply.

The board in decision T 1103/22 (definition of active site disputed by parties in relation to sufficiency of disclosure) notably said – with reference to T 435/20 – that it was common general knowledge that it was not a matter of routine to make antibodies against some epitopes (in particular non-linear ones) and this could require considerable inventive skill. Since insufficient disclosure cannot be remedied by post-published documents, they were not taken into account.

Concerning screening processes for selecting antibodies, contrary to the appellant’s (opponent’s) view, the board in T 326/22 considered that the case differed from T 435/20, T 1466/05 and T 657/10. For the board, it was credible that the skilled person would arrive without undue burden at further antibodies falling within the scope of claim 1. The board also referred to T 431/96.

In T 2164/21 neither the application as filed nor common general knowledge provided the skilled person with any information that would reliably guide them to the amino acid substitutions which resulted in an antibody fulfilling the functional requirements of the claim. The fact that methods for generating an antibody with a specific mutation, methods for assessing deamidation and methods for antigen-binding activity were described in the application, were well known to the skilled person and were routine on the priority date of the application did not mean that the invention could be put into practice without undue burden. The board then considered the settled case law as to when experimentation and testing was reasonable.

The board found that the essential issue to be considered in T 601/05 of 2 December 2009 date: 2009-12-02 was whether or not the patent enabled the production of human monoclonal antibodies binding with high affinity to soluble TNF and, consequently, whether or not the skilled person could practise the invention over the whole scope of the claim (following T 792/00). On the evidence before the board it did not.

In T 1466/05 the question arose whether the availability of a hybridoma producing one specific antibody together with a general description of the epitope recognised by this antibody put the skilled person in the position to obtain further antibodies with the same specificity. The board observed that similar questions had arisen in various cases decided by the boards of appeal, and different boards had given different answers depending on the circumstances of each case (T 510/94, T 513/94, T 349/91, T 716/01).

In T 1466/05 the claim was not restricted to monoclonal antibodies defined by reference to the deposited hybridoma. As the application did not disclose any specific antigen for preparing further antibodies as claimed, the board considered that a skilled person seeking to prepare such antibodies would have had to embark on a research programme without any teaching in the application as how to achieve the desired specificity which amounted to an undue burden (cited in this respect by T 760/12; see also T 435/20, including on technical aspects very detailed reasons, where the facts were considered by the board comparable to the facts underlying T 1466/05).

In T 424/21 (therapeutic antibodies and Fc fusion proteins) the disputed claim was formulated in the form of a first medical use. According to the board, the Enlarged Board in G 5/83, although not commenting explicitly on Art. 83 EPC, also 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 in the case in hand 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. 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 present case was different from the situation underlying decision T 604/04 (sufficiency of disclosure denied in relation to a first medical use).

Concerning the second medical use claims (claim 6 in the "Swiss-type" format, claim 7 in the purpose-restricted product claim format) in T 760/12, the technical effect, which was the therapeutic effect, was expressed in the claim. When the technical effect is expressed in the claim, the issue of whether this effect is indeed achieved over the whole scope of the claim is a question of sufficiency of disclosure (G 1/03, OJ 2004, 413, point 2.5.2 of the Reasons). Hence, under Art. 83 EPC, 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 (T 609/02, point 9 of the Reasons). The board 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.

The claim at issue in T 405/06 was directed to immunoglobulins with certain stated features. The question to be answered was whether a skilled person would have found at the filing date in the application as filed a sufficiently clear and complete disclosure of the precise structure of such an immunoglobulin in order to be in a position to prepare it over the broad range of the claim. Although the claim was not limited to immunoglobulins obtained from camelids, the experimental part of the description as a whole and the corresponding figures dealt exclusively with camel immunoglobulins and the general part of the description did not contain a complete disclosure of any non-camelid immunoglobulin either. The requirements of Art. 83 EPC 1973 were thus not satisfied, as the skilled person would be left with the task and burden of finding out how the teaching relating to camelid immunoglobulins could be extended to products of different origins (e.g. human immunoglobulins) falling within the broad area of the claim.

The application the subject of T 433/07 concerned broadly reactive opsonic antibodies that react with common staphylococcal antigens. The board held that the invention was insufficiently disclosed; the application did not disclose either any serotype cross reactive monoclonal antibody or the isolation of an antigen associated with the serotype cross protective response required by the claim. A European patent application containing a claim referring to a method of production had to provide the skilled person with the means to produce the desired product. If this was not the case, this shortcoming could not be overcome by telling him exactly how the desired product had to look and which screening criteria had to be applied to find it.

In T 617/07 the claim at issue concerned monoclonal antibodies and synthetic and biotechnological derivatives thereof defined by structural and functional features. The board found that, given his common general knowledge, the skilled person would be able, in a possibly time-consuming but straightforward manner, to provide antibody variants having the functional requirements indicated in the claim. There was no doubt that the structural definition in the claim included antibodies that did not have the desired function but, when attempting to rework the invention the skilled person would on the basis of his knowledge be able to avoid non-functional variants. Therefore, because the skilled person knew how to achieve antibodies with the desired function on the basis of a particular known antibody, he was not in the situation of having to sort out non-functional variants in a burdensome manner.

In T 386/08 the patent concerned humanised antibodies with framework sequences. It disclosed not only one, but many examples. The board pointed out that the concept of sufficiency of disclosure over the whole scope of the claim did not mean that, for a disclosure to be considered as sufficient, it had to be demonstrated that each and every conceivable embodiment of a claim could be obtained; see G 1/03 (OJ 2004, 413). There may be situations where the specification contains sufficient information on the relevant criteria for finding appropriate alternatives ("variants") over the claimed range with reasonable effort. Under these circumstances the non-availability of certain variants encompassed by the claim at the priority date is considered immaterial for the sufficiency of disclosure. For an example where this was not so, see T 601/05 date: 2009-12-02. The current situation however was different in that the patent described quite a number of appropriate alternatives and in that the allegedly non-obtainable variants were "hypothetical" variants. The requirements of Art. 83 EPC were fulfilled.

Article 83 EPC was not complied with in T 941/16 (anti-PSMA antibody). The board decided that, in the absence of any examples of a claimed antibody/fragment, the general information in the patent application and the common general knowledge, taken together, could not be considered to provide the information necessary to allow the skilled person to reliably obtain substantially all of the claimed antibodies/fragments fulfilling the functional requirements of the claim. For particular combinations of complementarity-determining regions (CDRs) it was not credible that a humanised antibody/fragment with the properties defined in claim 1 would be obtained. Readily performing the invention across the entire scope of the claim placed an undue burden on the skilled person. Lastly, the board, with reference to G 1/03 (OJ 2004, 413, point 2.5.2 of the Reasons), dealt with the argument made by the appellant (applicant) that patent applications in the field of biochemistry should not be treated worse than those in the other fields of classical chemistry (presence of non-working embodiments in a generic chemical formula).

As regards claims directed to antibodies defined by functional features (i.e. by their ability to perform a certain function), it was stated in the Guidelines G‑II, 5.6.1.3 – March 2023 version: "If an antibody is defined exclusively by functional properties, it has to be carefully assessed whether the application provides an enabling disclosure across the whole scope claimed". As to the related case law, the boards held Art. 83 EPC not to be met in the following decisions: T 1466/05, T 601/05 date: 2009-12-02, T 1389/13. For examples of cases in which sufficient disclosure was established, see T 2045/09 and T 845/19 (antibody defined, after limitation, by structural and functional features). See also EPC Guidelines G‑II, 6 – April 2025 version .

For other decisions concerning antibodies, see T 32/17 (definition of an antibody by reference to a deposited hybridoma – R. 31 EPC); T 1708/18 (several aspects related to the antibodies discussed in the context of novelty).