Following the (in)famous Amgen v. Sanofi decision, which has declared invalid generic antibody claiming for failure to enable the full scope of the invention, antibody applications drafted in the United States focus on structural characterization by complementarity-determining regions and variable domains. However, functional antibody claiming offers a broader scope of protection and economic efficiency by bundling multiple antibodies under the roof of a common property, which is of great interest to companies developing therapeutic antibodies.

Defining an antibody by its epitope is one type of functional antibody claiming, which came into the limelight in Europe when Amgen's PCSK9 epitope claims were challenged in multiple EPO oppositions. While Amgen managed to avoid a potentially negative Board of Appeal decision on epitope claims in the first opposition against EP 2215124 by narrowing the claims to structurally defined antibodies (T 845/19), epitope claims of the divisional patent EP 3666797 are presently being challenged in an ongoing opposition as well as before the UPC. The decision of the Munich Central Division of the UPC of 16 July 2024 (UPC 1/2023) rejecting the epitope claims garnered much attention as one of the first UPC decisions on the merits. 

On the background of the Amgen saga and of the recent decision in T 435/20 rejecting as insufficient a claim to IL-23 antibodies defined by a conformational epitope, the decision in T 326/22 taken in the oral proceedings on August 1 this year is a welcome game changer. The Board of Appeal confirmed that epitope claiming, in particular conformational epitope claiming, is valid, provided the patent contains sufficient information on antibody generation.

The underlying case EP 2812443 concerned CD47 antibodies characterized by their binding to a conformational epitope defined by its sequence using open "comprising" language. The insufficiency objection was based on an alleged undue burden associated with de novo production of antibodies binding to a conformational epitope. The opponent emphasized the "elite event" nature of antibody generation by such classical methods as hybridoma or phage display, as well as the need for laborious X-ray crystallography ("XRC")-based epitope screening. The board, however, disagreed, confirming the EPO position that generating antibodies to a specific antigen as well as epitope determination, in particular by XRC, is a routine, albeit time-consuming, exercise. 

This decision gives a welcome boost to epitope claiming in Europe. Applicants should keep in mind the advantages of epitope claims when drafting patent applications.

Jones Day represented the patentee in T 326/22.