Full Court warns against dangerous affliction of parameteritis (and confirms invalidity of aripiprazole patent)

On Wednesday the Full Court of the Federal Court of Australia handed down a decision in which it upheld Justice Yates’ findings that Otsuka’s patent relating to aripiprazole, a drug used in the treatment of schizophrenia, is invalid for want of novelty and inventive step.  Otsuka had alleged that Generic Health’s aripiprazole products, which were registered for the treatment of schizophrenia, infringed the patent.

The invention claimed in claim 1 was a “Swiss style claim”, that is, the use of a drug (aripiprazole) in the manufacture of a medicine for a supposedly new therapeutic use – the treatment of schizophrenia, associated with a particular receptor, which fails to respond to certain other antipsychotic drugs.

On appeal, Otsuka challenged the findings of invalidity on the grounds that the primary judge had improperly construed two aspects of the claimed invention – the association between schizophrenia and the receptor (“the association” feature) and the failure to respond to other antipsychotic drugs (“the failure to respond” feature). Ostuka’s failure to persuade the Full Court that Justice Yates’ construction was flawed meant that its challenge to the findings of invalidity (which you can read about in our post here) also failed.

While an appeal to the High Court may follow (subject to special leave being sought and granted), it is certainly a win for generic manufacturers who are interested in the aripiprazole market.

The association feature

The Court upheld Justice Yates’ finding that the association feature was not a free standing essential feature – it was not the case that the claim required the disorder (schizophrenia) to be solely or directly caused by the receptor. In doing so, the Full Court rejected Otsuka’s argument that the specification taught, and the claims distinguished between, two forms of schizophrenia, one associated with the particular receptor and one not so associated. The Court also noted that the grammatical structure of the claim did not support the feature being a separate integer.

On Otsuka’s construction, that is, that the association feature was a separate essential feature, Beach J also thought that the claims would be infected with parameteritis, an “affliction” involving an attempt to re-patent the prior art by limiting the claims by reference to a series of parameters not specifically mentioned in the prior art – something which could be measured on equipment that was not available at the time of the prior art for example.  Here, the parameter was a statement of scientific theory positing a link between the disorders and the receptor, but added nothing to the invention which was still an old use of an old product.

The failure to respond feature

At first instance, Justice Yates found that the “failure to respond” feature required a failure of the disorder to respond to other drugs (in the sense that the drug was being used as a third or fourth line treatment).  The Full Court agreed that because the claim referred to treatment of schizophrenia which failed to respond to other drugs (plural), the feature referred to at least a third line treatment. The Full Court also accepted Justice Yates’ conclusion that while this was an essential feature of the invention, it was an “arbitrarily imposed” limitation as there was no teaching in the specification against using aripiprazole as a first or second line treatment. The Full Court accepted this construction.

Novelty and inevitable result cases

The Full Court also seemed to accept Justice Yates’ acknowledgement at first instance of the limitations of the inevitable result cases in the context of a claim to the use of a known compound for a new therapeutic use.  The fact that the previously known use of a compound inevitably treated the claimed condition was not determinative.  Nevertheless, simply explaining the mechanism which underlies the use already described in the prior is not sufficient to give rise to novelty. Here, the claim was to an old use of a known compound (treatment of schizophrenia) and neither the failure to respond feature nor the association feature, even if providing new information (the mechanism of action of the compound) gave rise to novelty.

Cripps question and inventive step

The Court also approved the application of the well-known Cripps question when assessing inventive step, finding that a notional research group at the priority date, in light of the common general knowledge combined with the prior art, would have been directly lead as a matter of course to try aripiprazole in the treatment of a patient suffering from schizophrenia which does not respond to at least two other drugs and which is associated with a particular receptor, in the expectation that it might well produce a useful result. Here, the prior art disclosed that aripiprazole was useful in treating schizophrenia and the discovery that this utility was due to the action of aripiprazole at a particular receptor did not provide an inventive step. Similarly, there was nothing inventive in the addition of a requirement that the patient’s impairment had failed to respond to a previous medication.