Viagra® Patent Appeal Case Clarifies Best Method Disclosure Requirements in Australia

This article first appeared in The Watermark Journal Vol 23 No 1 (March 2006)

The full Federal Court in Pfizer Overseas Pharmaceuticals v Eli Lilly and Company [2005] FCA 67 (while confirming that the relevant claim was invalid) rejected Eli Lilly’s contention that a failure to include the best method known to the applicant of performing the invention in a patent application, at the date of filing cannot be overcome by later amendment.

Background
Pfizer Overseas Pharmaceuticals (“Pfizer’” is the owner of Australian Patent No 676571 (“the patent”) claiming inter alia methods of treating erectile dysfunction (commonly referred to as impotence) in males. Under the patent and corresponding patents in other countries Pfizer has marketed Viagra® which has had huge commercial success worldwide with sales of US$1.78 billion in 2002 and more thereafter.

Eli Lilly and Company (“Eli Lilly”) markets a rival product called Cialis®.
In September 2002 Eli Lilly commenced proceedings in the Federal Court for revocation of each of the claims of the patent. It also sought a declaration that the patent was, and had always been, invalid on a number of grounds including that the invention as claimed in claim 10 of the patent did not involve an inventive step, was not fairly based on the matter described in the specification, was not sufficiently described and that the specification did not describe the best method of performing the invention as claimed in claim 10.

Pfizer cross claimed against Eli Lilly alleging that Eli Lilly had infringed the patent with its product Cialis®.

In his decision (Eli Lilly and Company v Pfizer Overseas Pharmaceuticals [2005] FCA 67) handed down 10 February 2005, the trial judge, Heerey J, found claim 10 of the patent to be invalid on two grounds: (1) it did not involve an inventive step and (2) it was not fairly based on the matter disclosed in the specification.

Although the best method known to the applicant of performing the invention was not disclosed in the complete specification when filed, and was only disclosed subsequently by way of amendment, Heerey J, held that the invention as claimed in claim 10 of the patent was sufficiently described, and that the specification did indeed describe the best method of performing the invention as claimed in claim 10. His finding that the date of determining sufficiency and best method is at the earliest, the date of grant, rather than the then accepted view, the date of filing, was controversial, leaving open the question that where a new best method is identified before grant, the specification may need to be amended to include a description of the method.

The Patent
The patent describes the invention as one which relates to “the use of a series of pyrazole [4,3-d] pyrimidin-7-ones for the treatment of impotence” and describes as subsets, compounds defined in formula (1) in ascending levels of preference. (Compounds comprising the invention are however described in the specification as: “potential inhibitors of cyclic guanosine 3’,5’—monophosphate phosphodiesterases (PDEs).

Following amendment, the claims before the court were claims 1 to 8 and 10.

Claim 1 is an independent claim directed to “A method of treating a male animal requiring such treatment, including man, to cure or prevent erectile dysfunction which comprises treating said male animal with an effective amount of formula (1) wherein….” (The compound defined as formula (1) was then defined by its chemical formula.)

Claims 2 to 7 are directly or indirectly dependent on claim 1. Each of dependent claims 2 to 4 narrows the scope of claim 1 by limiting the various substitutable atoms in formula (1). Dependent claims 6 to 8 which are directed to treatment with specific compounds of formula (1) as recited in these claims were added by amendment after the filing date when responding to an Examiner’s report. The compound of formula (1) recited in claim 8 is known as sildenafil citrate, the active ingredient of Viagra®.

Claim 10 is a second independent claim and is directed to “A method of orally treating man to cure or prevent erectile dysfunction in a man in need of such treatment, which comprises treatment with an orally effective amount of cGMP PDEv inhibitor, or a pharmaceutically acceptable salt thereof, or a pharmaceutical composition containing either entity”. The validity of this claim was critical to the dispute as the Cialis® product did not fall within the scope of claims 1 to 8 of the patent in suit.

The Appeal
Pfizer appealed the decision of the trial judge arguing that the invention as claimed in claim 10 of the patent should have been found to be not obvious and to be fairly based on matter disclosed in the patent specification. A notice of contention was filed by Eli Lilly. Eli Lilly argued inter alia that the trial judge should have found that the invention as claimed was not sufficiently described, and that the best method of performing the invention was not disclosed.

Inventive Step and Fair Basis
Pfizer succeeded in its appeal on the point of obviousness only. The Full Court held that, on accepted tests of obviousness as enunciated by the High Court in Aktiebolaget Hassle and Another v Alphapharm Pty Ltd 56 IPR 129, the evidence did not disclose lack of an inventive step in relation to the invention claimed in claim 10.

On the point of fair basis, Pfizer failed in its challenge to the finding that claim 10 was not fairly based on the specification. In contrast to the other claims, the compounds of claim 10 were identified by their inhibitory properties rather than their chemical structure. The patent was found not to contain a real and reasonably clear description of the use of cGMP PDEv inhibitors (as recited in claim 10) outside the compounds of formula (1).

As claim 10 was held to be invalid the appeal was dismissed.

Sufficiency and Best Method
The Full Court also considered the other points of contention raised by Eli Lilly, including sufficiency and best method.
The issue to be resolved in the revocation action was whether the complete specification as granted, could in compliance with section 40(2)(a) of the Patents Act 1990 (“the Act”), be said to describe the invention fully, including the best method known to the applicant of performing the invention, in view of the fact that the best method, namely the use of sildenafil monocitrate, the active ingredient of Viagra® (as recited in claim 10) was only disclosed in the patent by virtue of an amendment subsequent to the filing date.

The Full Court found that the Act’s regime in providing for amendment of a complete specification, coupled with the dictionary definition of “complete specification”, signify that in each of the examination process, opposition proceedings, and revocation proceedings it is the specification as amended that must be considered in order to determine whether section 40(2) (a) of the Act is met.

This decision stands for the proposition that if a complete specification does not, at the time of filing, comply with section 40(2)(a) of the Act in that it does not describe the invention fully, including the best method known to the applicant at that time, then it may be amended after filing to include this best method, subject to the regime of amendments that are and are not allowable under sections 102 and 104 of the Act (and the regulations), and to the application of those provisions to the facts of the particular case.

In it’s decision, the Full Court emphasised that the disclosure requirement for the best method known to the applicant of performing the invention is for the best method known to the applicant as at the filing date of the specification.

Implications of Decision
Pfizer has applied for special leave to appeal to the High Court.

Unless the High Court overturns the decision of the Full Court (should the special leave application be successful), an inadvertent failure to include the best method at the time of filing need not necessarily be fatal to the validity of the claims of the potential patent. This depends upon the allowability at the relevant time of amendments to include the best method.

Further, unless the High Court overturns the decision, it seems there is no onus imposed on the applicant to disclose a new best method identified between the filing date of an application and grant of the patent.