Inherent anticipation of second medical use claims in New Zealand and Australia

A recent decision by the New Zealand Patent Office (IPONZ) highlights the issue of inherent anticipation that can arise when seeking to claim a second medical use. This article considers lessons from recent cases in New Zealand and Australia relating to inherent anticipation of such claims.

Second medical use claims in New Zealand and Australia

Under New Zealand law, methods of treating humans are excluded from patentability, and second medical uses are typically claimed using Swiss‑style claims. Such claims are considered patentable where they are based on the discovery of previously unrecognised properties of known pharmaceutical compounds (per National Research Development Corporation v Commissioner of Patents [1959] HCA 67).

Australia is perhaps unique in that it allows both method of treatment and Swiss‑style claims. Second medical use claims are considered patentable where they relate to "a known compound for a hitherto unknown and unexpected, but nevertheless useful, therapeutic use" (AstraZeneca AB v Apotex Pty Ltd [2014] FCAFC 99 at [296]).

In both jurisdictions, novelty and inventiveness can be conferred by a new therapeutic effect, patient group, route of administration, dosage, or dosing regimen, and the like. However, claims defining new information about an existing therapeutic use may be considered a "mere discovery" in New Zealand or "parameteritis" in Australia.

New Zealand – Lessons from Chemocentryx

In Chemocentryx, Inc. [2025] NZIPOPAT 11, the relevant claims were directed to:

Use of a therapeutically effective amount of avacopan: [structural formula], or a pharmaceutically acceptable salt thereof, for the manufacture of a medicament for maintaining plasma complement factors Bb, C3a, C5b-9 and C5a in the treatment of ANCA-associated vasculitis in a human, wherein the medicament is to be administered to the human such that the level of plasma complement factor Bb, C3a, C5b-9 and C5a following administration of the avacopan or the pharmaceutically acceptable salt thereof is within about 30% of the level before the administration.

Second Medical Use Kat

Prior art documents D1 and D2 disclosed treatment of ANCA-associated vasculitis (AAV) with avacopan. While neither D1 nor D2 measured plasma complement levels of the AAV patients, in the absence of any technical feature in the claim that would impact the recited levels (such as a dose or regimen), the Hearing Officer considered these levels inherent in D1 and D2. Accordingly, the claims were found to be directed to a "mere discovery" that was an inevitable result of carrying out the directions of D1 and D2.

Australia – Lessons from Otsuka and Neurim

In Otsuka Pharmaceutical Co., Ltd v Generic Health Pty Ltd (No 2) [2016] FCAFC 111, the relevant claims were directed to:

Use of a carbostyril compound of [structural formula] … or a pharmaceutically acceptable salt or solvate thereof, for the production of a medicament, effective in the treatment of disorders of the central nervous system associated with [the] 5-HT1A receptor subtype, which disorder ... is selected from cognitive impairment caused by treatment-resistant schizophrenia, cognitive impairment caused by inveterate schizophrenia, or cognitive impairment caused by chronic schizophrenia ...

The prior art taught the use of aripiprazole for treating schizophrenia. The Full Court found that the claims lacked novelty because they merely define a subset of the use described in the prior art and using a new scientific theory to justify the narrowing (i.e., the association with the 5-HT1A receptor subtype). The Court considered this to be "a variant form of parametritis" (Otsuka at [177]).

In Neurim Pharmaceuticals (1991) Ltd v Generic Partners Pty Ltd (No 5) [2024] FCA 360, the relevant claims were directed to:

Use of melatonin in the manufacture of a medicament for treating a patient suffering from primary insomnia characterized by non-restorative sleep and improving the restorative quality of sleep in said patient ...

The prior art documents disclosed the use of melatonin to treat insomnia. While none of the prior art documents taught the treatment of primary insomnia characterized by non-restorative sleep and improving the restorative quality of sleep, Generic Partners argued this was mere "parameteritis". In contrast to Otsuka, the Court in Neurim considered this feature was not inherently anticipated because it related to the "new and surprising result that melatonin could, additionally, be used to improve the restorative quality of sleep in a specific group of insomnia patients that had not previously been addressed in the prior art" (Neurim at [330]).

Key takeaways 

Inherent anticipation may arise in New Zealand and Australia where a second medical use claim (or any claim, for that matter) relies on a "mere discovery" that does not impart a technical effect. In this regard, novelty cannot be not conferred merely by (Otsuka at [176]; per Bristol-Myers Squibb v Baker Norton Pharmaceuticals Inc [1999] RPC 253 at [277] and Actavis UK Ltd v Janssen Pharmaceutical NV [2008] FSR 35 at [99]):

• providing more information about an old use;
• explaining the scientific theory for the mechanism which underlines a use already described in the prior art; or
• claiming a narrower use of an old product, where that narrower use fits within the broader use for the old product already described in the prior art.

Such features are considered mere "parameteritis". In contrast, novelty can be conferred by parameters that "have a technical effect, are part of the invention, and are directly related to a claimed advantage of the invention" (Neurim at [331]; per Austal Ships Pty Ltd v Stena Rederi Aktiebolag (2005) 66 IPR 420 at [108]).