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Patent considerations in the immunotherapy space: Claiming by function or target

Following on from our previous article, which explored antibody claiming by structure, the present article delves into some detail around the second type of format that is commonly used when claiming antibodies: claiming by function or target.

As discussed in our previous article, claims that are directed solely towards protecting the functional aspect of the antibodies are typically too broad, in that the scope of the claim would extend to all antibodies that have those features, which likely leads to lack of support and enablement.

With respect to claiming by target, generally, it is difficult to obtain antibody patent protection by relying only on definitions that refer to the target antigen, in the absence of any mention of a specific antibody. However, if the target antigen is novel and not obvious, then it may be possible to have broad patent claims for those antibodies binding to new epitopes, without limiting those claims to antibody structure. To achieve such, depends heavily on the ability to satisfy the requirements for support and enablement, as the specification should disclose at least one of said antibodies that target the new antigen or epitope. Furthermore, the target should be fully disclosed in the specification.

(i)           Europe

Claims that seek to broadly protect antibodies based on the target antigen, requires the target antigen to be fully disclosed, including its protein sequence, without using language that may introduce some variability to the target antigen, such as “an antigen comprising…”. Use of such language may result in a lack of novelty, especially if there may be existing antibodies that bind to undefined areas of the target antigen. Nonetheless, the types of claims that have been permitted through the EPO with respect to novel target antigens or epitopes, include for example claims that are directed to “an antibody that specifically bind to SEQ ID NO: 1”, which avoids the need to specify and define the antibody. Thus, in Europe, claims that define an antibody according to its target are permitted, if the target per se is defined or if a new epitope on a known target is defined (either linear or conformational). The latter (defining an antibody by a new epitope) is generally favoured by the EPO.

On the other hand, if the target antigen is known, typically the EPO will consider this as part of common general knowledge to be able to produce antibodies against said known target antigen. Thus, a lack of inventive step is usually raised, unless an unexpected technical effect can be proven by experimental data (Boards of Appeal in T0735/00).

With respect to claims that rely on functional features, instead of target antigens, it will need to be proven that the claimed antibodies are novel over existing antibodies that target the same antigen. Functional features may include binding affinity, activation or suppression of receptor-based activity, neutralizing activity, amongst other features. Claims that rely on reciting functional features must allow the skilled person to distinguish the claimed antibody from other existing antibodies in the art, based on the functional features defined. In other words, the specific biological activities that are uniquely triggered by action of the antibody must be defined.

In Europe, it is also possible to have antibody claims that are directed to the competitive binding efficiency with a reference antibody. Such claims require the techniques and methods for determining such competitive binding efficiencies to be described in the specification. A number of supporting example antibodies should be included in the specification to ensure that there is not an undue burden placed upon the skilled person to reproduce the antibody as claimed.

Furthermore, in Europe, antibody claims can also utilize functional language if the claims are directed to a medical use of said antibody. For example, in the treatment of disease. The advantage of utilizing this format of claiming is that it could potentially avoid any antibodies in the prior art that may not be used for the purposes of the specified medical treatment.

(ii)           Australia

As mentioned in our previous article, the Raising The Bar (RTB) regime in Australia has brought Australian practice closer in line with that in Europe, the UK and the US. Claims which define antibodies only in relation to their functional limitations, such as their binding affinity or pharmacokinetic capabilities, are more likely to face challenges with respect to novelty, given that all antibodies exhibiting those functional features would be encompassed by the claim. If the antibody claimed is directed to a known antigen, it is usual to disclose each of the complementarity-determining regions (CDR sequences) as well as the surrounding framework region to satisfy the enablement requirement, even if antibody specificity may rely on a single heavy chain and light chain CDR to carry out its function. Unless the specification discloses evidence of the invention exerting a broad technical contribution, for example, if it can be demonstrated through experimental evidence that particular CDR sequences are non-functional, it is likely that there will be a finding of lack of support, despite the possibility that the invention could theoretically be performed across the breadth of the claim in light of technical advancements in the field.

To avoid such objections, it is generally advised that Applicants should at least include claims directed to specific embodiment(s), as a backup to any broader claims, to reduce the risk of a finding of patent invalidity, particularly under the RTB regime.

In Australia, methods for generating an antibody are considered routine in the art. Thus, it may be of interest to note that the Australian Patent Office permits claims which are directed towards an antibody that is capable of competing with a reference antibody for an antigen. For claims directed towards such protection, it is recommended that the specification includes disclosures surrounding how competition between the two antibodies is determined, as well as any details on any binding thresholds, preferably with the inclusion of some examples.

(iii)          US

Along similar lines to Europe and Australia, functional antibody claiming in the US relies heavily on support and enablement. The case of Amgen Inc v Sanofi 987 F.3d 1080 (Fed. Cir. 2021) has been discussed in our previous article, whereby the approach of broadly defining antibodies according to their functional properties was found to lack enablement, due to undue experimentation imparted on the skilled person to produce the invention as claimed, according to its full scope. There is therefore a much higher hurdle in fulfilling the enablement requirement for claims with broad functional language.

Although the case of Amgen Inc v Sanofi covered “double-function claims”, in that the claims were limited to those antibodies that possessed the defined binding function, as well as the defined blocking function, the Federal Court discussed that the binding function limitation on its own was sufficient to draw the finding of lack of enablement. The Court further discussed that with respect to the unpredictable nature of antibodies, a substitution in an amino acid sequence often affects antibody function, such that “testing would be required to ensure that a substitution does not alter the binding and blocking functions”. Whilst the need to test this does not lead to a finding of lack of enablement in itself, the Court held that what was crucial was the inability for a skilled person to predictability perform the invention across the full scope of the broad claims, according to the methods as described by the patent specification. It would have otherwise required a skilled person to first generate the antibodies and then screen each candidate antibody to determine whether or not it meets the double-function claim limitations. Hence, the finding of undue experimentation.

It is therefore advised to avoid claiming using only functional language in the US. Disclosing the methods for making the antibodies is not enough to fulfill the enablement requirements where functional limitations are applied. Claiming by function or target should be accompanied by the disclosure of a number of exemplified antibodies that meet said limitations. Combining functional limitations with some structural features further helps to improve the chances of allowance of such claims before the US Patent Office.  

Claiming by function or target therefore carries greater success before the European and Australian Patent Offices when compared with the USPTO, as it is considered routine in Europe to generate multiple antibodies to a target, which consequently means that the enablement and support requirements are less of a concern, provided the function or target is fully described and at least one antibody satisfying all the features of the claim is disclosed in the specification.

If you have any questions in relation to any of the above, please do not hesitate to reach out to our Life Sciences team. In the meantime, please look out for our next article in this series, which will discuss the third type of claim formatting that are conventionally used by Applicants when seeking to obtain a patent for antibody inventions.