6.1.3 5.6.1.3 Definition by target antigen and further functional features

In addition to the functional definition by the their target antigen, antigen it binds to, claims directed to antibodies can be further characterised by functional features defining further their other properties of the antibodies; for example, the binding affinity, neutralising properties, induction of apoptosis, internalisation of receptors, inhibition or activation of receptors (c.f. e.g. T 299/86, Reasons 3 - 6, and T 1300/05, Reasons 4 - 7).

An antibody may also be claimed by reference to its epitope, i.e. the structurally defined part of the antigen that it specifically binds to. Claims are sometimes directed to antibodies defined by their ability to compete with a reference antibody which is disclosed for the first time in the application. However, this property will not normally be sufficient to identify antibodies in the state of the art. In such a case, a complete search cannot be carried out (B‑VIII, 3) and an invitation under Rule 63(1) to indicate subject-matter for search is sent (B‑VIII, 3.1).

In all these cases, in the absence of any indication to the contrary, it is to be assumed that a prior-art antibody binding the same target antigen will have the claimed functional properties. Therefore a novelty objection may be raised and the burden of proof lies with the applicant (cf. G‑VI, 5). If an antibody is claimed exclusively by functional features and the prior art discloses in an enabling manner an antibody directed to the same antigen using an immunisation and screening protocol that arrives at antibodies having the claimed properties, it has to be assumed that the prior-art antibody inherently displays the same functional properties as the claimed antibody, which thus lacks novelty G‑VI, 6). On the other hand, if the antibody is defined by unusual parameters, care has to be taken that these do not disguise a lack of novelty (F‑IV, 4.11.1). In both these cases the burden of proof of novelty resides with the applicant.

The application must enable the person skilled in the art to produce further antibodies having the claimed functional property without undue burden (cf. F‑III, 1 and F-III, 4). Furthermore, the functional definition must allow the skilled person to easily and unambiguously verify whether they are working inside or outside the scope of the claim. The claim should therefore normally include the relevant characteristics of the method used to determine and define the functional property (cf F‑IV, 4.11).

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 and whether the functional definition allows the skilled person to clearly determine the limits of the claim.