Extending the term of a pharmaceutical patent

By Nicholas Tyacke and Jacqueline McStay.

Key Points:
The Federal Court holds that all compounds falling within a class disclosed in a patent, even if not specifically identified, are sufficiently disclosed for the purpose of extending the term of such a patent on the basis of any one of those compounds.

In Pfizer Inc v Commissioner of Patents [2005] FCA 137, the Federal Court considered whether a patent may be extended under section 70 of the Patents Act where the pharmaceutical substance upon which the application for extension is based merely falls within a novel class of compounds described and claimed in the patent, and is not itself specifically identified. In addressing this issue, the Court was also required to determine what, if any, impact the existence of a later selection patent that does specifically describe and claim the compound in question, may have on an application for extension of the parent patent.

Background

Pfizer owns a patent (the "parent patent") which describes and claims a novel class of compounds, which number in at least the millions, with anti-fungal activity. Pfizer also owns another patent (the "selection patent") which covers a subset of the original class of compounds which possess a surprisingly high level of anti-fungal activity. A compound called "voriconazole" was specifically disclosed and claimed in the selection patent but not in the parent patent.

In June 2004, Pfizer applied to IP Australia to have the term of both patents extended.

When may a patent term be extended?

The term of a standard patent is 20 years from the date of the patent (section 67). Patentees who own patents relating to pharmaceutical substances, however, may apply to have the term of such patents extended by up to five years. For the extension to be granted, strict criteria provided under section 70 of the Act must be met. A standard patent must firstly satisfy either or both of the following conditions under section 70(2):

(a) 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 or claims of that specification; or

(b) one or more pharmaceutical substances when produced by a process that involves the use of recombinant DNA technology, must in substance be disclosed in the complete specification of the patent and in substance fall within the scope of the claim or claims of that specification.

The qualification "per se" requires that the pharmaceutical substance is itself the subject of a claim. Extensions of the patent term are thus confined to patents that claim invention of the substance itself. It is not sufficient for a substance to appear in a claim only in combination with other products or integers or as part only of the description of a method of treatment or process of manufacture that is the subject of a claim.[1]

Further, under section 70(3), goods containing, or consisting of, the pharmaceutical substance must be included in the Australian Register of Therapeutic Goods. There must also have been a period of at least five years between the date of the patent and the first Australian regulatory approval. Finally, the patent must not have previously been extended (section 70(4)).

Decision of the Deputy Commissioner of Patents

The Deputy Commissioner of Patents allowed the extension of term for the selection patent, but denied the extension for the parent patent. He refused Pfizer's application in relation to the parent patent on the sole ground that it failed to satisfy section 70(2)(a) of the Act. This section, as noted above, requires that the compound be "in substance" disclosed in a patent's specification before an extension of that patent's term will be granted.

The Deputy Commissioner reasoned that voriconazole could not have been "in substance" disclosed in the parent patent because otherwise the claim to voriconazole in the selection patent would have been invalid as lacking novelty over the parent patent.

Pfizer appealed this decision. The critical question before the Federal Court was whether, despite voriconazole not being specifically identified in the specification of the parent patent, there had been "in substance" disclosure for the purposes of section 70(2)(a) of the Act.

Decision of the Federal Court

The Federal Court found in favour of Pfizer. The Court held that:

• In assessing whether section 70(2)(a) was satisfied, the validity of the patent sought to be extended is not to be considered. In doing so, the Court cited the recent High Court's decision in Lockwood Security Products Pty Ltd v Doric Products Pty Ltd (2004) 212 ALR 1 which held that in assessing one basis of invalidity, the other bases of invalidity should not be considered.
• The Deputy Commissioner should not have considered the selection patent in determining whether voriconazole was in substance disclosed in the specification of the parent patent.
• Comments made during the prosecution of the selection patent were not admissible in determining whether there had been "in substance" disclosure in the parent patent.
• The test in deciding whether there is "in substance" disclosure under section 70(2)(a) is, at its highest, whether there has been "a real and reasonably clear disclosure".
• Disclosure of a broad class of compounds discloses each member of that class, even where those members are not exemplified. This means that the express description of individual compounds which form part of the broad class is not required for there to be "a real and reasonably clear disclosure" of each of those compounds.
• As voriconazole was identifiable from the generic formula given in the parent patent by a person skilled in the art, there was a real and reasonably clear disclosure of voriconazole in the parent patent specification.

The Court then remitted the application back to the Commissioner as it did not have the power to grant the extension sought.

Conclusion

Due to this decision, it is now clear that where a claim is directed to a class of compounds, all compounds falling within that class, even if they are not specifically identified, are sufficiently disclosed for the purpose of extending the term of such a patent on the basis of any one of such compounds. This case also makes clear that issues of validity should not be considered in assessing whether a patent can be extended under the Act.

[1] Boehringer Ingelheim International GmbH v Commissioner of Patents (No 2) (2001) 52 IPR 529; and Prejay Holdings Ltd v Commissioner of Patents (2003) 57 IPR 424.