Beyond composition claims: Protecting antibody therapeutics in Australia

Defining the scope of the invention

For antibody inventions, the broadest commercially meaningful claim may not be the claim to the antibody itself. The inventor may have generated only one new antibody but also discovered that inhibition of its target provides an effective treatment for a disease with which that target had never previously been associated. In Australia, that distinction can materially affect the scope of protection available.

When assessing Australian claim scope, practitioners should be asking:

• what have the inventors made?
• what have the inventors discovered?

The extent to which the discovery represents a principle of general application justifying a broader claim scope depends on what was already known in the prior art.

Three scenarios for assessing claim scope

Scenario 1: a new target-disease relationship

Antibodies that inhibit protein X are already known, but nobody has previously associated inhibition of protein X with treatment of disease Y. The inventors make antibody A and find that it inhibits protein X therefore making it effective in treating disease Y.

If inhibition of protein X was not previously associated with treating disease Y there may be basis for seeking a claim extending beyond antibody A to encompass:

A method of treating disease Y by administration of an antibody that inhibits protein X.

The claim is generalised at the level of the newly identified therapeutic mechanism rather than the structure of the antibody used to establish it.

US practitioners will see some parallels with the recent US Federal Court decision in Teva Pharmaceuticals International GmbH v Eli Lilly and Company, No. 2024-1094 (Fed. Cir. Apr. 16, 2026). The claims at issue in Teva were directed to treating or reducing the incidence of headache by administering an effective amount of a humanised monoclonal anti-GCRP antagonist antibody. The Court made a distinction between an invention that lies in what the antibody genus is used to do versus the antibody genus itself, thus effectively permitting broader genus claims for the therapeutic method compared to a significantly narrower scope for the composition claims.

Scenario 2: a new epitope

Protein X is already a known therapeutic target for disease Y and antibodies that inhibit protein X are known. The inventors develop antibody B binding a particular epitope on protein X which produces a particular therapeutic effect such as improved efficacy or reduced side effect profile.

The principle of general application in this scenario, while narrower may still permit a claim as follows:

A method of treating disease Y in a subject, comprising administering an antibody that binds epitope Z of protein X.

Where the contribution resides at the epitope level, the specification should be drafted so that the epitope, its functional significance and the relationship between the epitope and the therapeutic effect are well defined.

Scenario 3: a new antibody but no general therapeutic principle

Where there are numerous known antibodies to protein X and their use in treating disease Y is known, and the inventors have developed antibody C which also treats disease Y. The contribution may reside primarily in the antibody and therefore the claim scope will need to focus on the particular antibody, including its heavy and light chain variable region sequences. Such a claim would be drafted as follows:

A method of treating disease Y by administering to the subject antibody C.

The potentially available scope differs because the prior-art landscape, and therefore the inventors' contribution, differs. Australian support law requires the scope of the claims to be justified by the disclosure and contribution to the art. The principle of general application identifies the level at which the invention may be generalised. Knowledge of the prior art can therefore inform drafting and the extent to which the invention can be generalised beyond a single antibody.

The Australian position

For an antibody invention, practitioners should consider:

• What was already known in the prior art concerning the disease target?
• What did the inventors discover? Was it a new antibody, an epitope-function relationship and/or a new targe-disease relationship?
• How far can that discovery legitimately be generalised?

Claiming therapeutic methods in Australia

Australia permits claims to both methods of therapeutic treatment and Swiss-style therapeutic use and treats them as claims of different scope. Therefore, where appropriate, practitioners should consider representative claims directed to:

A method of treating disease Y in a subject, comprising administering to the subject an antibody that inhibits protein X.

Use of an antibody that inhibits protein X in the manufacture of a medicament for treating disease Y.

The method of treatment claim is directed to the therapeutic method, typically requiring administration to the patient, however a Swiss-style claim is directed to the manufacture/use of the antibody in the manufacture of a medicament for the therapeutic purpose.

What data are necessary to support a broad therapeutic method claim?

To satisfy support and enablement requirements, practitioners should consider including experimental data that supports:

• Establishing a credible link between the claimed antibody characteristic and therapeutic effect
• Including data relevant to the therapeutic mechanism such as binding affinity, competition assays, receptor activation or inhibition, ligand blocking, internalisation, downstream signalling, cell proliferation or killing, cytotoxicity, disease-relevant assays, and animal efficacy.
• Defining the epitope including one or more of antigen sequence, residues forming the epitope, residues critical for binding, the relationship between that epitope and biological activity.
• Including comparative and unexpected-effect data such as improved potency, superior affinity, different epitope, improved selectively, improved receptor blockade, increased stability, reduced immunogenicity, better internalisation etc.

Ultimately, the Australian opportunity to claim the therapeutic use broadly should influence experimental design before filing, not claim drafting after filing.