Antibody inventions: Updates in the EPO Guidelines for Examination

The EPO Guidelines for Examination are set to undergo updates effective from 1 March 2024. The draft version of the updated Guidelines includes some interesting changes which relate to Antibody inventions (G-II, 6)1.  

One notable update is the removal of “definition by the epitope” as a separate type of definition for antibodies. This change does not significantly affect existing practice; instead, it consolidates the epitope definition under subsection G-II, 6.1.3 "Definition by target antigen and further functional features."

This reorganisation of the definitions clarifies that the epitope definition should be treated as any other functional feature, aligning well with current practice. Epitope claims define the antigen targeted by the antibody along with the functional feature of binding to a specific epitope, and were already assessed against all the relevant subsections of the Guidelines (i.e. subsection G-II, 6.1.2 which relates to the definition with reference to the antigen, and 6.1.3 which relates to further functional features).  

It is also worth mentioning that the Guidelines now refer to the possibility of defining an antibody by its ability to compete with a reference antibody. This approach allows applicants to disclose a novel antibody binding to a novel epitope, and draft claims covering any antibody competing for binding to the antigen with the novel (“reference”) antibody. This type of definition, which has been frequently used by applicants in recent years, effectively defines the epitope without specifying its exact structure in the claim, although it sometimes faces insufficiency objections requesting that the claim specifies how competition is determined. 

The Guidelines, however, caution that a complete search is normally not possible for such claims. This reflects a notion that identifying prior art antibodies based on this property is challenging and seemingly aims to discourage applicants from pursuing claims of this type over claims specifying the structure of the epitope. How this update will affect the examiners’ approach remains to be seen. However, we do not expect there will be a blanket position that a complete search cannot be performed for any claim directed to an antibody which competes with a reference antibody because, depending on the level of disclosure of the reference antibody and the antigen that it was raised against, a sensible comparison with prior art antibodies can be reasonably achieved.  

The distinction between “linear” and “discontinuous” epitope in the wording of the claims has been removed. Before this amendment, the Guidelines stated that if the epitope is “linear”, closed wording must be used in the claim to delimit the part of the antigen that the antibody interacts with, and if the epitope is “discontinuous”, the claim needs to specify the exact amino acid residues that are bound by the antibody. We do not expect that the way epitope claims are interpreted will be affected by the deletion of this terminology, as this subsection of the Guidelines was anyway not used as guidance for claim construction. This revision, however, might offer applicants greater flexibility in selecting the language used to define the epitope, irrespective of the nature the epitope (“linear” vs “discontinuous”). 

Although the requirement to specify the method for determining a "discontinuous" epitope in the claim is no longer explicitly mentioned in the Guidelines, the underlying principle is expected to largely remain unchanged. This is because the new paragraph relating to sufficiency of disclosure of antibodies defined by functional features (G-II, 6.1.3) maintains the point about reciting the characteristics of the method used to determine the functional property. Nonetheless, the deletion of this requirement which was specific for “discontinuous” epitopes, may imply that claims relating to this epitope type will face less scrutiny than previously.

As regards inventive step (G-II, 6.2), the list of exemplary unexpected technical effects has been updated to remove reference to ‘improved affinity’ for the antibody target and include improvement in ‘stability’. Reference to the requirement to define the complete variable regions for antibodies that rely on their binding affinity for inventive step has also been deleted. We do not expect that this amendment will mark a change in examination practice as it was made for presentational reasons, based on the EPO’s commentary2 during consultation cycles with the SACEPO Working Party on Guidelines. Finally, the end of the same section now highlights that new antibody platforms/formats may be considered inventive. 

In summary, the updated Guidelines include clarifying changes concerning epitope definitions. These amendments are not anticipated to lead to significant changes in the way epitope claims are treated at the EPO.



1 The draft updates Guidelines for Examination, Part G can be found here. 
2 Consultation results of the 26th SACEPO WP/G meeting on 10 October 2023

Our blog post summarising issues and considerations based on recent Board of Appeal decisions in relation to the “epitope definition” and other functional definitions can be found here.