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Is means-plus-function claims the answer to US antibody claims?

In the US claims to antibodies generally require the inclusion of specific sequences, mechanisms of action and/or epitopes in order to be accepted.  This contrasts with the EPO where more functional language is often acceptable.  One of the factors determining this difference is that the EPO generally considers the preparation of antibodies to be a routine procedure for the skilled person, and so the function of the antibody can be considered novel.   In contrast, the USPTO generally considers the development of an antibody to be an inventive development but therefore requires the antibody to be very closely defined.

However, in a significant development we now report, means-plus-function language for a claim to an antibody complied with both of the USPTO requirements for written description and for the claim not to be indefinite.

Where functional language alone is used in US claims, such claims commonly attract written description and enablement objections.  Enablement requires that the skilled person be able to make and use the invention, while the requirement for a written description means the invention must be adequately described in the specification, with the inventor being able to disclose the technologic knowledge on which the invention is based and demonstrate that he or she was in possession of the full invention on filing.

In US16/803,609, https://patentcenter.uspto.gov/applications/16803690, in the name of Chamberlain, the Examiner objected to a claim directed to a method of treating a patient with an antibody on the grounds of lack of written description.  The claim in question was:-

A method of treating a patient by administering an anti-C5 antibody comprising: (a) means for binding human C5 protein; and (b) an Fc domain comprising amino acid substitutions M428L/N434S […], wherein said anti-C5 antibody with said amino acid substitutions has increased in vivo half-life as compared to said antibody without said substitutions.

This claim uses means-plus-function language to define the antibody, and critically does not include specific sequences, mechanism of action or epitopes as typically required under US practice.  While the specification described one example of an anti-CR5 antibody, this was already known in the prior art.

The Examiner rejected the claims, and an appeal was filed to the PTAB, which upheld the appeal.  A rehearing again upheld the rejection also finding the claim indefinite.

The case was appealed to the Federal Circuit, but after the filing of the opening brief by the applicant, the USPTO director requested that the case be remanded back to the ARP (Appeals Review Panel) for an analysis of means-plus function claim in biotechnology, and particular antibodies.  This remand request was granted.

The ARP considered two questions.  The first question was whether the preamble was limiting and lacked written description, and here the ARP found that the language was limiting, and because the specification did not describe the treatment of any disease with the antibody, it did lack written description.

The second question was whether the means-plus-function language for antibody claims was definite and satisfied the written description requirement.  Here the APR first noted that the language “means for binding human C5 protein” in the claim was a means-plus-function limitation, and then noted that the example in the description of the anti-CR5 antibody corresponded to this requirement.  Critically, the ARP also found that “it is not necessary for the specification to describe equivalents of [the antibody] to meet the definite requirement”.  In conclusion the ARP said:-

It is true that the section 12, rule 6 provides that a means plus function element “shall be construed to cover the corresponding structure, material or act describe in the specification and equivalents thereof”.  That is, the claim is interpreted to cover both the corresponding structure, material or act described in the specification, as well as equivalents of that structure, material or act.  Notably, section 112, rule 6 does not state that the specification must also describe equivalents of that structure.  If Congress had intended the statute to require a description of equivalents, it could have placed “and equivalents thereof” before “described in the specification”, which it did not do. “

Thus, the ARP concluded that the means-plus-function language for the antibody complied with the requirement for written description and that the claim could not be rejected for indefiniteness.  https://www.uspto.gov/sites/default/files/documents/2022001944_order_20240521.pdf

This decision does not solve the problem with antibody claims in the US, in particular in that it does not consider the question of enablement.  However, it does appear to be a step in the right direction. In this case, ultimately, the claim was still rejected, but promisingly the rejection was not in relation to the antibody definition.

Nevertheless, this does give hope that means-plus-function language could assist in antibody cases and it is “worth a go”.


Our articles are for general information only. They should not be considered specific legal advice, which is available upon request. All information in our articles is considered to be accurate at the date of publishing.

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