Extended Release, Expeditious Rejection: Federal Court Invalidates Sun Pharma’s Aripiprazole PTE

Sun Pharma ANZ Pty Ltd v Otsuka Pharmaceutical Co Ltd [2025] FCA 44

Background

On 5 February 2025, Justice Downes of the Federal Court of Australia delivered her decision in the dispute between Otsuka Japan and its licensees (Lundbeck A/S and Australia and Otsuka Australia) (collectively referred to as Otsuka) and Sun Pharma ANZ Pty Ltd (Sun Pharma).

The dispute related to Otsuka Japan’s Australian Patent No. 2004285448, entitled “Controlled release sterile injectable aripiprazole formulation and method” (the Patent).  The Patent described and claimed controlled release formulations which contain aripiprazole as the active pharmaceutical ingredient (API).  Aripiprazole molecules bind to receptors (primarily D2 receptors) in the brain, which is useful in treating schizophrenia and bipolar I disorder.

Sun Pharma commenced proceedings against Otsuka seeking to “clear the way” ahead of their Australian launch on 1 April 2025 of their generic version of the ABILIFY MAINTENA (400 mg) powder and solvent for injection.

Key Issues

The key issues in dispute were:

(i) Whether the Patent’s patent term extension (PTE) had been wrongly granted and should be removed.  Otsuka argued that the PTE was valid, relying on eight claims of the Patent (known as the PTE Claims) and two products listed on the Australian Register of Therapeutic Goods which consisted of kits which included aripiprazole powder and solvent for prolonged release suspension for injection vial or pre-filled syringe (the ARTG Goods); and

(ii) Whether the PTE Claims were invalid for failure to comply with ss 40(2)(b) and 40(3) of the Patents Act 1990 (Cth) (the Act).  Sections 40(2)(b) and 40(3) respectively require that a complete specification must end with claims defining the invention; and that the claims must be clear and succinct and supported by matter disclosed in the specification.

Sun Pharma did not contest Otsuka’s cross-claim for threatened infringement arising from Sun Pharma’s proposed generic product, so that the proceeding could be heard and determined expeditiously.  Sun Pharma adopted this position on the basis that it was made without prejudice to Sun Pharma’s position on the proper construction of each of the claims, and in circumstances where it maintained its position concerning the invalidity of the PTE Claims and the PTE.

Her Honour ultimately found in Sun Pharma’s favour holding that the PTE Claims and PTE were invalid, and that the cross-claim should be dismissed.

Scope of the Australian PTE Regime

In Australia, section 70 of the Act sets out specific conditions which must be met to obtain a PTE for a pharmaceutical patent, including that:

• one or more pharmaceutical substances per se must in substance be disclosed in the complete specification of the patent and in substance fall within the scope of the claim(s) of that specification; and
• goods containing, or consisting of, the substance must be included in the Australian Register of Therapeutic Goods.

Her Honour held that the following principles emerged from the authorities for the purposes of identifying a claim for a pharmaceutical substance per se:

(1) only a claim for a pharmaceutical substance as such or alone is eligible for a PTE; and

(2) claims for the following inventions are not eligible for a PTE:

(a) a pharmaceutical substance which forms part of a method or process;

(b) an existing pharmaceutical substance prepared by a new and inventive process;

(c) a pharmaceutical substance when produced by a particular process (a product by process claim); and

(d) a new and inventive method of using an existing pharmaceutical substance (such as in a new method of treatment).

Her Honour also held that:

(i) The expression “in substance fall within the scope of the claim[s]” required that the pharmaceutical substance per se must take all of the essential integers of the claim.  Her Honour considered that to hold otherwise would result in an impermissible broadening of the patent monopoly during the extended term; and

(ii) Following Justice Perram’s decision in Cipla Australia Pty Ltd v Novo Nordisk A/S [2024] FCA 1414 (Cipla v Novo Nordisk), “pharmaceutical substance” included formulations.  Her Honour went on to state that, once one accepted that a pharmaceutical substance included a formulation, it necessarily followed that the focus was on whether that formulation (as a whole) was for therapeutic use and whether that formulation (as a whole) was one whose application involves one of the actions or interactions in (a) or (b) of the statutory definition of “pharmaceutical substance”, namely: (a) a chemical interaction, or physico-chemical interaction, with a human physiological system; or (b) action on an infectious agent, or on a toxin or other poison, in a human body.  There was nothing in the text of the statutory definition which required one to also analyse whether, and be satisfied that, each constituent part of the formulation satisfies both of those requirements before the formulation itself can be found to be a pharmaceutical substance.

Otsuka’s and Sun Pharma’s Arguments

Otsuka argued that the PTE was valid, relying on the PTE Claims and ten asserted pharmaceutical substances per se.

The PTE Claims fell into two categories: (i) those involving controlled release liquid (i.e. ready to use) injectable formulations (Controlled Release Injectable Formulation Claims); and (ii) those involving freeze-dried (i.e. lyophilised) controlled release formulations (Freeze-dried Controlled Release Formulation Claims).

An example of the Controlled Release Injectable Formulation Claims was Claim 1, which claimed:

A controlled release sterile 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,

(b)    a vehicle therefor, and

(c)    water for injection.

An example of the Freeze-dried Controlled Release Formulation Claims was Claim 16, which claimed:

A sterile freeze-dried controlled release aripiprazole formulation which comprises:

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

(b)    a vehicle therefor,

which formulation upon constitution with water forms a sterile injectable formulation which upon injection releases aripiprazole over a period of at least about two weeks.

The ten pharmaceutical substances per se were as follows:

(I) 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;

(II) further or in the alternative, (I) above, wherein the aripiprazole is in the form of a monohydrate or alternatively Aripiprazole Hydrate A;

(III) further or in the alternative, (I) or (II) above, also comprising sodium carmellose (carboxymethyl cellulose), mannitol, monobasic monohydrate sodium phosphate and sodium hydroxide;

(IV) further or in the alternative, (III) above, also comprising water for injection;

(V) further or in the alternative, (IV) above, which upon injection releases aripiprazole over at least about one week;

(VI) a sterile lyophilised/freeze-dried aripiprazole formulation comprising aripiprazole having a mean particle size of about 1 to 10 microns or alternatively within the range from about 2 to about 4 microns;

(VII) further or in the alternative, (VI) above, wherein the aripiprazole is in the form of a monohydrate or alternatively Aripiprazole Hydrate A;

(VIII) further or in the alternative, (VI) or (VII) above, also comprising sodium carmellose (carboxymethyl cellulose), mannitol, monobasic monohydrate sodium phosphate and sodium hydroxide;

(IX) further or in the alternative to (VIII) above, which upon constitution with water forms a sterile injectable formulation;

(X) further or in the alternative to (IX) above, which upon injection releases aripiprazole over a period of at least about two weeks.

Sun Pharma argued that the PTE was invalid because none of the asserted pharmaceutical substances per se, nor the PTE Claims on which they were based, met the Act’s section 70 requirements.  Sun Pharma put forward the following eight arguments in support of its position:

(1) The Freeze-dried Controlled Release Formulations did not meet the definition of “pharmaceutical substance”.

(2) If the Controlled Release Injectable Formulations were capable of being a “pharmaceutical substance” (which was denied), the ARTG Goods did not contain or consist of such substance, because the ARTG Goods comprised a freeze-dried powder in a vial.

(3) If the PTE Claims claimed anything other than the active ingredient aripiprazole simpliciter, such claims were not claims to a “pharmaceutical substance”, as the definition of “pharmaceutical substance” (properly construed) was confined to active ingredients and did not include formulations with excipients.

(4) If the Court determined that the definition of “pharmaceutical substance” did include formulations, neither the Freeze-dried Controlled Release Formulations nor the Controlled Release Injectable Formulations qualified, because the excipients within those formulations were not for a “therapeutic use” as defined and/or do not have an application (or one of whose applications) which involved a chemical interaction, or physico-chemical interaction, with a human physiological system.

(5) The majority of the asserted pharmaceutical substances per se impermissibly did not take all of the integers of the PTE Claims, and thus could not be relied upon for the purposes of section 70 of the Act.

(6) When regard was had to all of the integers of the PTE Claims, they included process features and/or features which limited the use of the formulations, contrary to Full Court authority.

(7) Contrary to s 70(3) of the Act, the ARTG Goods did not include each feature of the PTE Claims, in particular that they did not include the feature which required that “upon injection [the product] releases aripiprazole over a period of [a specified time]”.

(8) Each of the PTE Claims were invalid and should be revoked for lack of clarity and/or lack of definition pursuant to s 40(3) and/or s 40(2)(b) of the Act.

PTE Validity

Ultimately, Sun Pharma succeeded in invalidating the PTE on the basis that the majority of the asserted pharmaceutical substances per se (namely pharmaceutical substances (I) to (IV) and (VI) to (IX)) did not “fall within the scope of” any of the PTE Claims because they only took part of the PTE Claims.  As stated above, Justice Downes held that a pharmaceutical substance must take all of the integers of a claim to “fall within the scope” of the claim.

Her Honour rejected Sun Pharma’s remaining challenges to the PTE as follows:

(1) That the Freeze-dried Controlled Release Formulations did not meet the definition of “pharmaceutical substance” on the basis that such formulations were not (themselves) “applied” so as to “involve a chemical interaction, or physico-chemical interaction, with a human physiological system” because they needed first to be reconstituted with water to form injectable (liquid) formulations before those formulations (i.e. different substances) were “applied” so as to “involve a chemical interaction, or physico-chemical interaction, with a human physiological system”.  Her Honour rejected this contention on two bases:

(i) “Application” referred to the use to which the substance was put, and generally its purpose, not its physical application.  In this case, the “application” was the treatment of schizophrenia and related disorders.

(ii) The Federal Court had previously recognised that the pharmaceutical substance per se claimed in a patent “may not have the necessary therapeutic use or enable the required physico-chemical interaction unless formulated”.  The need to reconstitute a freeze-dried formulation was analogous to the need to formulate if the pharmaceutical substance per se was a single chemical compound.

(2) That the Controlled Release Injectable Formulations registered on the ARTG were not goods containing, or consisting of, the pharmaceutical substance which was in substance disclosed in the complete specification of the patent and in substance fell within the scope of the claims of that specification.  Sun Pharma argued that the Controlled Release Injectable Formulations registered on the ARTG consisted of a freeze-dried powder in a vial together with a separate vial containing the water for injection.  It therefore submitted that the Controlled Release Injectable Formulations registered on the ARTG did not contain or consist of the same pharmaceutical substance which was in substance disclosed in the complete specification of the patent and in substance fell within the scope of the claim or claims of that specification, being injectable formulations.

Justice Downes rejected this argument, stating that the correct approach required a simple comparison of the pharmaceutical substance identified which was in substance disclosed in the complete specification of the patent and in substance fell within the scope of the claim or claims of that specification, with the ingredients of the goods on the ARTG.  If the pharmaceutical substance was an ingredient, “[n]o further interrogation of the ARTG is necessary”.

(3) That pharmaceutical substances did not include formulations or did not include formulations which had excipients with no therapeutic application.  Her Honour rejected both arguments given her finding that, following Justice Perram’s decision in Cipla v Novo Nordisk, “pharmaceutical substance” included formulations.

(4) That the PTE claims were not to pharmaceutical substances per se because the claims included process features and/or limitations by result as follows:

(i) “controlled release”; “injectable formulation”; and/or “which upon injection releases aripiprazole over a period of [a specified period of time]”; and

(ii) “freeze-dried controlled release”; “which [freeze-dried] formulation upon constitution with water forms a sterile injectable formulation”; and/or “which [injectable formulation] upon injection releases aripiprazole over a period of [a specified period of time]”.

Justice Downes considered that the PTE Claims referred only incidentally to methods of process, so as to better describe the new and inventive substance, being the claimed injectable or freeze-dried formulations.  Her Honour also noted that Sun Pharma had not identified any authority supporting its submission that a claim which contains a limitation by result could not be a pharmaceutical substance per se.  On this point, her Honour noted that, in Spirit Pharmaceuticals Pty Ltd v Mundipharma Pty Ltd (2013) 216 FCR 344; [2013] FCA 658, the argument that certain claims were limited by result did not prevent a finding by Justice Rares that the formulation was a pharmaceutical substance per se.

(5) That the ARTG Goods did not take each feature of the PTE Claims, in particular that they did not take the feature which required that “upon injection [the product] releases aripiprazole over a period of [a specified time]”.  Her Honour rejected this argument in light of the expert witness’ views to the contrary in the joint expert report.

PTE Claims Validity

Sun Pharma argued that the PTE Claims were invalid for failure to comply with:

• section 40(2)(b) which requires that a complete specification must end with claims defining the invention; and
• section 40(3) which requires that the claims must be clear and succinct and supported by matter disclosed in the specification.

The validity challenge centred on the feature in each of the PTE Claims that “upon injection [the product] releases aripiprazole over a period of [a specified time]”.  Sun Pharma argued that the person skilled in the art would not be able to determine whether or not all aripiprazole formulations (i.e. all embodiments) that otherwise met the requirements of the PTE Claims would fall within or outside this feature based upon the information in the Patent and the common general knowledge (with or without routine experimentation).

Consideration of Sun Pharma’s validity challenge required her Honour to answer two questions:

(1) whether (as Sun Pharma submitted) the PTE Claims contained limitations by result, or whether (as Otsuka submitted) the specification taught that this feature was an inherent property of formulations prepared according to the invention; and

(2) whether the PTE Claims satisfied section 40(3) and/or s 40(2)(b) of the Act.

Her Honour held that:

(1) The PTE Claims were claims limited by reference to result with the implication that the conditions of the manufacture of the formulations could be adjusted to secure the specified result, being the feature in each of the PTE Claims that “upon injection [the product] releases aripiprazole over a period of [a specified time]”.  Her Honour reached this conclusion in light of the evidence which showed that there was a range of factors which would affect the release of the aripiprazole, including particle size.  As choices had to be made concerning these factors in order to achieve the minimum release period which was stated in the PTE Claims, it could not be concluded that all of the formulations which otherwise met each of the PTE Claims would release for more than one or two weeks.

(2) The Patent did not show the person skilled in the art how to determine whether or not each formulation that otherwise satisfied any of the PTE Claims fell inside or outside the release boundary. The Patent was silent as to how the person skilled in the art could extrapolate from the blood plasma concentration data disclosed in the Patent to a determination of the release of aripiprazole from the depot.  As the person skilled in the art was not given that information, they would not be able to use that information to enable them to determine whether all formulations which otherwise fell within any of the PTE Claims took this feature.

Further, even if the person skilled in the art was able to use blood plasma concentrations as an indirect means to identify whether a given formulation that otherwise meets the PTE Claims fell within the release boundaries, experiments would need to be performed.  Those experiments would be onerous, time-consuming, and would provide variable and unreliable results such that the person performing the experiments would be left in doubt as to whether any given formulation fell within the scope of the PTE Claims.

As a result, the PTE Claims were invalid because they failed to define the invention and lacked clarity, as required by sections 40(2)(b) and 40(3) of the Act.

Outcome and Implications

So, her Honour ultimately found in Sun Pharma’s favour holding that the PTE Claims and PTE were invalid.  This meant that the cross-claim was also dismissed.

Justice Downes’ decision is highly relevant for many reasons.  In particular, her Honour’s decision provides invaluable guidance on the scope of the Australian PTE regime; and on the circumstances in which patent claims will fail for lack of definition and lack of clarity.

Otsuka appealed her Honour’s decision, which was heard by the Full Court on 20 and 21 May 2025.  So, stay tuned for the appeal court’s judgment!

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