Spirit Pharmaceuticals Pty Ltd v Mundipharma Pty Ltd [2013] FCA 658 In a recent judgment handed down by the Federal Court, Justice Rares found that a pharmaceutical formulation containing the known active agent oxycodone, although defined by a result to be achieved, nevertheless satisfied the requirement of being a pharmaceutical substance per se, and that therefore, the extension of term for Mundipharma's patent claiming these formulations had been validly granted under section 76 of The Patents Act 1990.

Brief background to the patent for Oxycontin

The patent1 related to controlled release oral dosage formulations of oxycodone (marketed under the brand name "OxyContin"). Whilst the claims specified the amount of oxycodone contained within the formulations, they did not set out amounts and proportions of excipients required to achieve the controlled release. Rather, the claims defined the pharmacokinetic parameters to be achieved upon administration of the formulation. The patent expired in November 2012, but an extension of term to July 2014 had been previously granted in 2000.

Spirit Pharmaceuticals seeks rectification of the register of patents

The controlled release formulation afforded distinct advantages over the previously available immediate release formulation, and in an attempt to bring their own generic version of the controlled release formulation to market, Spirit Pharmaceuticals launched proceedings seeking rectification of the Register of Patents by removal of the extension of term on the basis that the it had been invalidly granted. One of the grounds advanced by Spirit in support of the rectification of the Register: was that the controlled release formulation was not a pharmaceutical substance per se.

Did the claimed formulations satisfy the definition of a 'Pharmaceutical Substance'?

Section 70(2)(a) of the Australian Patents Act sets out the requirement that one or more pharmaceutical substances per se must be disclosed in the complete specification and in substance fall within the scope of the claim. The court was asked to consider whether the claimed formulations satisfied the statutory definition of a "pharmaceutical substance per se".

The Patents Act 1990, relevantly defines a pharmaceutical substance as:

"...a substance (including a mixture or compound of substances) for therapeutic use whose application (or one of whose applications) involves: (a) a chemical interaction, or a physico-chemical interaction, with a human physiological system;..."

It was common ground that the claims defined a product which was a mixture that included oxycodone and that the therapeutic use in this instance was to alleviate pain. However, the parties differed in their view as to what constituted the pharmaceutical substance per se. Spirit contended that the therapeutic effect was achieved solely by oxycodone, not the mixture of substances which made up the controlled release formulation, and that the claims did no more than define circumstances in which a desired result was to be achieved by various combinations.

His Honour considered the nature of the chemical interaction required by the definition of pharmaceutical substance, noting that the therapeutic result was achieved by two separate interactions: the interaction within the GI tract which causes the formulation to break down the excipients and release the oxycodone for absorption into the blood plasma in a controlled manner, and the nerve interaction, where the oxycodone in the blood plasma interacts with nerve cell receptors in the spinal chord and brain to alleviate pain. This provided a different result to that achieved by repeated doses of the immediate release formulation over the same period of administration. His Honour therefore reasoned that the mixture of substances of the controlled release formulation had a therapeutic use, being the controlled release and action of oxycodone over time, achieved by two separate interactions within the human physiological system and that the controlled release formulation therefore was a pharmaceutical substance per se.

The outcome for Mundipharma

The decision means that Mundipharma will retain their exclusive right to market Oxycontin in Australia until 23 July 2014. Patentees for patents claiming new pharmaceutical formulations of known active agents will also welcome the judicial confirmation that a "pharmaceutical substance" is not to be interpreted as being necessarily restricted to the active agent.