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The claims of a patent application must concisely define the matter for which patent protection is sought2. In patent applications that relate to antibodies, the claims generally define the antibodies by reference to one or more of the following: the antigen to which the antibody binds; a hybridoma; or the sequence of the antibody polypeptide. The BOX gives some examples of the different ways that antibodies can be claimed.

Antibodies defined by antigens

Traditionally, the European Patent Office (EPO) has readily granted claims of the following format, particularly if the protein antigen itself satisfies the criterion for patentability: “An antibody which binds specifically to protein X” (Box, example 1). In such claims, the antibody is being defined indirectly — that is, by reference to the antigen to which it binds. Care needs to be taken, however, to ensure that such claims do not inherently cover known antibodies, particularly if the protein is a member of a family of well-known proteins and antibodies against such proteins are already known. In such circumstances, a claim of the following format should be considered: “An antibody which binds to protein X, but not to protein Y”, where protein X is the novel protein and protein Y is a known one having epitopes in common with the novel protein.

In the US, claims of the above formats are allowable, but the US courts have recently imposed a requirement that the antigen to which the antibodies bind must be a “fully characterized antigen”3.

Antibodies defined by hybridoma

In cases in which the antigen that the antibody binds to is already known and some antibodies to that antigen have already been publicly disclosed, a general claim to antibodies against that antigen will lack novelty. However, claims to antibodies that are directed to specific epitopes on that antigen might still be possible (assuming that the known antibodies are not directed to those epitopes).

If the invention relates to a specific monoclonal antibody which is produced by a hybridoma, the invention can be claimed by reference to that hybridoma (see Box, example 2). The question then arises as to how it is possible to describe the hybridoma in the patent application in a manner which will allow the skilled person to put the invention into practice. The answer is to make a deposit of the hybridoma under the Budapest Treaty with an International Depository Authority4.

The scope of a claim to a monoclonal antibody defined by a hybridoma will in general be relatively narrow — that is, it will generally only provide protection for the specifically deposited antibody and not other antibodies that are directed to the same epitope. However, deposited hybridomas can also be used to define an epitope on a particular protein and a claim can then be tailored to any antibodies which bind to that epitope5.

Antibodies defined by sequence

With the advent of phage-display libraries and readily available DNA-sequencing apparatus, antibodies are now often defined by reference to specific amino-acid or nucleic-acid sequences (see Box, example 3).

It should be noted, however, that if an antibody is known (for example, an antibody that is produced by a known hybridoma), merely determining the sequence of that antibody will not render that antibody novel — it is still the same (known) chemical entity. However, specific fragments of that known antibody might still be patentable, particularly if they have surprising or unexpected properties.