Patent term extensions – Is the sun setting on claims limited by result?

In Sun Pharma ANZ Pty Ltd v Otsuka Pharmaceutical Co Ltd [2025] FCA 44, Sun Pharma successfully challenged the patent term extension of Otsuka’s patent for controlled release formulations of aripiprazole, an antipsychotic used to treat schizophrenia and bipolar disorder. While the Full Court’s decision on the important question of whether patents claiming formulations are eligible for extension is due to be handed down shortly, in this article we examine the two avenues on which Sun Pharma was successful in challenging the validity of a PTE for a formulation patent. 

Background

Otsuka’s patent number 2004285448 (the Patent) claimed controlled release injectable aripiprazole formulations, and was set to expire on 18 October 2024. Otsuka was granted a patent term extension (PTE) based on the registration of its ABILIFY MAINTENA products, which contained aripiprazole as the active pharmaceutical ingredient, on the Australian Register of Therapeutic Goods (ARTG), extending the Patent term to 25 July 2029. 

Having planned to launch a generic version of ABILIFY MAINTENA on 1 April 2025, Sun Pharma commenced proceedings alleging that Otsuka’s PTE was wrongly granted and sought to have it removed.  

In defending the validity of the PTE, Otsuka relied on eight claims of the Patent (PTE Claims). For example, claim 3 was to: 

A controlled release aripiprazole injectable formulation which upon injection releases aripiprazole over a period of at least one week, which comprises:

(a) aripiprazole having a mean particle size of about 1 to 10 microns, and 

(b) a vehicle therefor, said vehicle comprising: 

(1) one or more suspending agents,

(2) optionally one or more bulking agents, and

(3) optionally one or more buffering agents, and

(c) water for injection.

Otsuka proposed ten alternative “pharmaceutical substances” as satisfying the term extension requirements in s 70 of the Patents Act 1990 (Cth). Each of these alleged “pharmaceutical substances” included aripiprazole and various excipients. For example, Otsuka asserted that the PTE was validly granted based on a pharmaceutical substance per se disclosed and claimed in the Patent being: 

a controlled release sterile aripiprazole injectable formulation, comprising aripiprazole having a mean particle size of about 1 to 10 microns or alternatively about 2 to about 4 microns … also comprising sodium carmellose (carboxymethyl cellulose), mannitol, monobasic monohydrate sodium phosphate and sodium hydroxide.

Importantly, Sun Pharma reserved its position to argue in any appeal that for the purposes of s 70 of the Patents Act, a pharmaceutical substance per se cannot include a formulation – that is, the term extension regime applies to patents that disclose and claim new APIs, not subsequent patents claiming particular formulations of a known API. This question was raised by Cipla in Cipla Australia Pty Ltd v Novo Nordisk A/S [2024] FCA 1414, Perram J deciding that a claim to a formulation could satisfy the definition of "pharmaceutical substance”. 

For the purposes of argument in Sun Pharma v Otsuka, Sun Pharma reserved its position on appeal, and Downes J followed the decision in Cipla v Novo Nordisk that a formulation can be a “pharmaceutical substance” for the purpose of s 70. The result is that this question will now be determined by a Full Court in a decision that is expected shortly. 

The pharmaceutical substance must take all of the integers of a claim

Sun Pharma argued that the majority of Otsuka’s ten asserted “pharmaceutical substances” did not fall within the scope of any of the PTE Claims because they only took part of each claim. In response, Otsuka argued that it was sufficient for the asserted pharmaceutical substances to be included amongst the things claimed, but Downes J accepted Sun Pharma’s submission. Her Honour held that the “pharmaceutical substance per se” must take all of the essential integers of a claim to “fall within the scope” of that claim. 

In so holding, Downes J followed the Full Court decision in Boehringer Ingelheim International v Commissioner of Patents [2001] FCA 647, in which the Full Court accepted a submission that “the words ‘in substance fall within the scope of the claim or claims’ of the specification [in s 70(2)], refer to the elements that make up the claim or claims”, and that these words “prevent any extensions of term from having a broadening effect on the claims of the extended patent … when it did not, during its primary term, include protection for that substance alone”. Where a claim is to a formulation, rather than an API, the exploitation of the API itself would not be an infringement of the formulation claim. As for the test for infringement, only the formulation as claimed would take all the essential integers and thus “fall within the scope” of the claim.

On this basis, Downes J found that eight of Otsuka’s ten asserted pharmaceutical substances did not fall within the scope of any of the PTE Claims as they did not take all of the essential integers of those claims. 

Lack of clarity and definition

In addition to challenging the validity of the PTE, Sun Pharma asserted that the PTE Claims were invalid because they were unclear and did not define the invention. Before considering this question, Downes J first needed to consider whether the PTE Claims contained “limitations by result”, as Sun Pharma alleged. 

A claim “limited by result” is one that defines the invention by reference to a result that it is intended to achieve. Sun Pharma argued that the PTE Claims contained limitations by result as they each included a controlled release feature whereby the formulation “upon injection releases aripiprazole over a period of” a specified time (Controlled Release Feature). For example, as set out in the Background above, the Controlled Release Feature in claim 3 of the Patent covered a formulation with controlled release of aripiprazole over a period of at least one week. 

Justice Downes rejected Otsuka’s counter-argument that the specification of the Patent taught that the Controlled Release Feature was inherent in formulations prepared according to the invention. Her Honour pointed to several inconsistencies in the Patent specification, including references to various periods of time over which the controlled release of aripiprazole was said to occur (e.g. up to eight weeks). Downes J found that, in the only passage referring to controlled release occurring over a one-week period, there was no articulated (or even implied) correlation to any particular particle size and thus no suggestion that the release profile was inherently tied to the particular claimed formulations (which specified particle size). Downes J determined that the Controlled Release Feature was not an inherent property of formulations prepared according to the PTE Claims, agreeing with Sun Pharma that the PTE Claims were claims limited by result. 

For a claim defined by its result, it is important to specify the methods used to achieve that result; otherwise, the invention may lack sufficient definition or the claim may not be adequately supported by the disclosure in the specification. Her Honour determined on the basis of the expert evidence that the Patent did not provide sufficient guidance for a person skilled in the art to assess whether each formulation covered by the PTE Claims was within or outside the release boundary of the Controlled Release Feature of the claim. Her Honour found that the instructions in the Patent for achieving the Controlled Release Feature were meaningless to those skilled in the art. As a result, each of the PTE Claims was invalid because it failed to define the invention and lacked clarity, as required by ss 40(2)(b) and 40(3) of the Patents Act.

Orders were made that the PTE Claims be revoked and that, consequently, the PTE was wrongly granted so that the term of the Patent expired on 18 October 2024. Otsuka has appealed the decision, and Sun Pharma has cross-appealed, arguing that patents claiming pharmaceutical formulations are not eligible for term extensions. Argument was heard by the Full Court on 20 and 21 May 2025 and the decision is expected shortly. 

Key lessons

The impending decision of the Full Court on the eligibility of formulation patents for term extension will set a significant precedent for pharmaceutical patents in Australia. In the meantime, this decision demonstrates the way in which a lack of sufficient definition of patent claims limited by result can lead to invalidity, and the importance of definition as a ground of attack when it comes to granted PTEs. The pharmaceutical substance included on the ARTG that is relied on by a patentee as supporting a PTE must take all of the integers of the relevant claim(s) relied on.