Since the three CDRs of each of the variable domains of the light and heavy chains are normally responsible for binding to the antigen, the conventional antibody, in order to be uniquely defined by its structure only and have its characteristic binding specificity, needs to be defined by at least these six CDRs to fulfil the requirements of Art. 84.
CDRs when not defined by their specific sequence must be defined according to a numbering scheme, for example, chosen from that of Kabat, Chothia or IMGT.
If a conventional antibody is defined by fewer than the sequences of the six CDRs, the claim will be objected to under Art. 84 because it lacks an essential technical feature.
A claim to an antibody defined by its structure by fewer than six CDRs will be considered to fulfil the requirements of Art. 84 only if it is experimentally shown that one or more of the six CDRs do not interact with the target epitope or if it concerns a specific antibody format allowing for epitope recognition by fewer CDRs.
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/g_ii_5_6_1_1.htm
Date retrieved: 17 May 2021