Antibody patenting at the EPO

Over recent years, antibodies have become increasingly important as therapeutics, as well as in other applications, such as diagnostics. The new EPO Guidelines for Examination that came into force on March 1, 2021 now include for the first time a subsection detailing EPO practice in relation to antibodies (G-II, 5.6). This newly introduced subsection provides in particular guidance on allowable claim formats and the assessment of inventive step for antibody inventions.

For a new antibody to a known antigen, it is usually necessary to define the antibody by sequences. The Guidelines formalise the position taken by EPO Examiners for many years: a requirement that a conventional antibody (having both heavy and light chain variable domains) is defined by a minimum of six CDR sequences.

Contrary to some other jurisdictions (e.g. US), a unique structure does not automatically confer an inventive step on an antibody to a known target. Instead, an unexpected effect and/or superior properties relative to pre-existing antibodies to the same target have to be made plausible for an inventive step to be acknowledged. Alternatively, antibodies can be inventive if the application overcomes technical difficulties in producing or manufacturing the claimed antibodies.

The Guidelines note that if this surprising technical effect involves the binding affinity, the claim should recite the six CDRs and the framework regions because the EPO considers that the framework regions can also influence the affinity of an antibody.

In some situations, e.g. where it can be shown that one or more of the CDRs do not interact with the target epitope, defining an antibody by less than 6 CDRs may be allowed.

It is also fairly rare to be allowed by an EPO Examiner to claim variation in the CDRs or the sequences of the variable domains. Nevertheless, when combined with a clear functional feature, an antibody may be characterised by the sequences of both variable domains or by the CDRs with less than 100% sequence identity. Accordingly, in some cases an allowable definition for antibodies is by a combination of structural and functional features.

According to the Guidelines, it can in some circumstances still be allowed to broadly define antibodies based on functional features alone. Such features may correspond to in vivo and/or in vitro activities and also include those determined in cell-free assays (e.g. antibody affinity, cross-reactivity) and/or in cell cultures (e.g. anti-proliferative or stimulatory activity).

Also, where the invention lies in the target, such as where the target is a newly identified molecule broad antibody claims may still be available.

In practice, however, it can be particularly challenging to obtain patents at the EPO to antibodies defined without including structural features. The EPO’s position is that it is routine for the skilled person to generate an antibody to a known target, and that prior art antibodies directed to the same antigen using an immunisation and screening protocol as used for the claimed antibodies, inherently display the same functional properties.

The new Guidelines also caution that for antibodies defined only by functional features, it must be considered whether the application provides an enabling disclosure across the whole scope of the claim and whether the definition permits the skilled person to clearly determine the limits of the claim scope. It is thus advisable to have a plausible/technical teaching in the patent application that supports the corresponding functional feature, and to adequately specify in the description tests or procedures to verify the feature.

Where this ensures a particular technical effect, an antibody can also be defined by its epitope, provided it is clearly defined using closed language and, similar as for other functional features, that the application provides an enabling disclosure across the whole scope claimed, and that the functional definition allows the skilled person to clearly determine the limits of the claim.

It is also possible to define antibodies by the process of their production e.g. based on immunisation by an antigen, or through a deposited hybridoma cell producing the antibodies. While the former may allow similar coverage as a functional features, the latter is limited to one antibody sequence and of limited added value if sequence information is available.

Finally it is noted that in a second medical use claim, where the novelty and inventive step is derived from the therapeutic effect, the EPO will often still accept a more generic definition of the antibody by the functional feature which ensures this technical effect.  

In conclusion, the EPO’s current examination practice and its well-established case law on the patentability of antibodies have have now been formalized in these new Guidelines. It remains of interest however to consider on a case-by-case basis how your antibody-related invention can be optimally protected. Please do not hesitate to contact our experts at De Clercq & Partners.