I know what it says, but what does it mean? The complexities of claim construction.

‘Words are free. It’s how you use them that may cost you.’ KushandWizdom (Tumblr.com)

The above quote was not originally intended to relate to the protection of intellectual property, but it is particularly applicable in relation to patent law. The protection afforded by any patent is determined by the wording of the claims and how those words are understood by a Court. Loose language or a poor choice of words in a claim can have disastrous consequences for the patent owner.

In any contentious patent matter, an initial consideration of the decision maker is to arrive at a construction of the patent claims so that issues of novelty, inventive step and infringement can be determined. Although there are well set-out principles to guide claim construction, in certain circumstances the choice of words in the claims may not achieve the patentee’s intended meaning. For example, a Judge may decide, based on the wording of a claim, that a feature is not essential to the invention and thus read the claim as though that feature was not present. Alternatively, the wording of the claim may lead a Judge to impose one or more limitations on the claim that were not intended by the patentee.

Unfortunately for the patentee, in the Full Federal Court decision in Otsuka Pharmaceutical Co. Ltd v Generic Health Pty Ltd (No 2) [2016] FCAFC 111, the court affirmed the trial Judge’s opinion that the claims at issue fell into both of these potential traps.

The patent in question related to the treatment of certain medical conditions using a known compound.

The method claim read as follows:

A method for treating a patient suffering from disorders of the central nervous system associated with [the] 5 HT1A receptor sub-type, which disorder
(i) [is] selected from cognitive impairment caused by treatment-resistant schizophrenia, cognitive impairment caused by inveterate schizophrenia, or cognitive impairment caused by chronic schizophrenia, and

(ii) fails to [respond] to antipsychotic drugs selected from chlorpromazine, haloperidol, sulpiride, fluphenazine, perphenazine, thioridazine, pimozide, zotepine, risperidone, olanzapine, quetiapine, or amisulpride, comprising administering to said patient a therapeutically effective amount of a carbostyril compound of [the given structural formula] … or a pharmaceutically acceptable salt or solvate thereof.

There were two main construction issues. The first was the feature in the claim that described the named disorders as associated with [the] 5 HT1A receptor subtype – the association feature. The second issue was the feature in the claims which referred to the failure to respond to antipsychotic drugs selected from the drugs named in the claims – the failure to respond feature. In both instances, the court construed the claim in a way that was adverse to the patentee.

The association feature

At trial, the patentee argued that the association feature was essential as it distinguished between two distinct types of disorders, namely (i) those associated with the receptor, and (ii) those that were not. The Judge was of the opinion that the patentee took this view as it would make it harder for the other side to prove its case on invalidity.

In construing the phrase ‘disorders of the central nervous system associated with [the] 5 HT1A receptor subtype’, the Judge at first instance was of the opinion that this did not define an essential feature that meaningfully added to the identification of the disorders to be treated. This finding was based on the fact that the patent specification did not support the patentee’s contention that there were, in fact, distinct types of disorder. Rather, the receptor played an important role in the disorders claimed. Accordingly, the trial Judge found that the named disorders and the association with the receptor defined a single essential integer and were to be read together. This finding was affirmed on appeal, with the effect that the claims lacked novelty and inventive step, notwithstanding that the prior art did not specifically mention the ‘association of the disorders with [the] 5 HT1A receptor subtype’. The patentee’s own words from the patent specification came back to haunt them.

The failure to respond feature

The issue was whether this was an essential feature, and if so, what was meant by the selected wording. The parties disputed whether the limitation referred to a second line treatment (where only one other drug had failed) or whether it referred to a third and later line treatments (failure of two or more treatments). Due to the wording of the specification and claims, the Judge construed the feature as relating to third or later line treatments. This decision was driven by the use of the plural ‘drugs’ rather than the singular ‘drug’ in the claim, as well as the examples that referred to the failure to respond to numerous drugs. While it was not relevant given the findings on novelty and inventive step, this construction had the potential to make it very difficult to enforce the claim on any potential infringer.

In determining whether the feature was essential, the Judge was of the opinion that it constituted an arbitrary limitation. Consequently, he gave it little weight in the assessment of novelty and inventive step, and therefore treated it almost as an inessential feature.

On appeal, the trial Judge’s construction of this feature was upheld, with particular emphasis placed on the examples which related to a failure to respond to multiple drugs.


In a minority judgement, while agreeing with the majority on the outcome, Beach J made reference to how the claims were affected with “parameteritis”. This occurs where a patent claim includes reference to one or more parameters not mentioned in the prior art which appear on their face to be limitations. In many instances, they are merely an attempt to re-patent the prior art. As such, the Judge found that to inject the parameter ‘associated with [the] 5 HT1A receptor subtype’ added nothing to the invention. The Judge then proceeded to state that ‘the artificiality of such a result and the nebulous verbiage of the claim language gives me confidence that the phrase disorders of the central nervous system associated with [the] 5 HT1A receptor subtype is not a separate and essential integer.’


This case reinforces the principal that the wording of both the patent specification and the claims are crucial in determining the construction that will be afforded to the claims. Following this judgment, it is clear that the presence of inherent or arbitrary limitations in a claim will not necessarily be given significant weight in claim construction, and ultimately in the assessment of novelty, inventive step and infringement.


Neil is a Principal in the Chemistry and Life Sciences practice group. He has 20 years’ patenting experience across a wide range of chemical technologies, with particular expertise in pharmaceutically active small molecules, polymers and nanotechnology. He specialises in the drafting and prosecution of patent applications in the pharmaceutical and specialty chemicals areas, where he assists clients in obtaining patent protection in Australia and other jurisdictions of interest.