Background
On 28 May 2008 the Full Court of the Federal Court of Australia handed down its decision1 in the appeal from the 2006 decision in Ranbaxy Australia Pty Ltd v Warner-Lambert Company LLC. This case involved two patents relating to the anti-cholesterol drug atorvastatin, which has been marketed very successfully for a number of years by Pfizer under the trade mark Lipitor.
The two patents in question were AU 601981 (981 Patent), which includes claims covering a particular class of molecules known an HMG-CoA reductase inhibitors, and AU 628198 (Enantiomer Patent), which claims atorvastatin, a specific structural form or enantiomer of one of the class of compounds claimed in the 981 Patent.
Ranbaxy had not challenged the validity of the 981 Patent but had contended that its intended importation and sale of atorvastatin would not infringe the claims of this patent. At first instance, the court held that Ranbaxy’s proposed atorvastatin product would fall within the claims of the 981 Patent.
Ranbaxy was successful in challenging the validity of the Enantiomer Patent at first instance on the basis that the patent had been obtained by fraud, false suggestion or misrepresentation to the Patent Office.
The decision on both of the patents was the subject of the appeal.
Do the claims include atorvastatin?
Ranbaxy had contended that the structural formula in the claims of the 981 Patent could only be construed as relating to an equal mixture (racemate) of the two ‘R’ and ‘S’ enantiomer types for that class of compounds, as the method disclosed in the patent specification would produce racemates only. According to this construction, atorvastatin, which is the R enantiomer only, would be outside the scope of the claims.
The Full Court upheld the decision of the judge at first instance that the claims, when read in the context of the specification of the 981 Patent, related to equal and unequal mixtures of enantiomers as well as the individual enantiomers. In reaching this conclusion, the court relied on expert evidence on what would have been the common general knowledge of a synthetic organic chemist in 1986. This was relevantly found to have included an assumption that the ‘R’ enantiomer was likely to be the active or more active enantiomer, and a knowledge of various techniques for separating enantiomers or preferentially synthesising a particular enantiomer.
The judges further said that confining the subject matter of the 981 Patent to racemates ‘would be to exclude the very thing, namely the active or more active enantiomer, that any person working in the field as at the priority date would know to be the key to the useful activity of the compounds disclosed’.
False suggestion and misrepresentation
The specification of the Enantiomer Patent included data that appeared to indicate that the ‘R’ enantiomer (atorvastatin) had a ten-fold increase in ability to inhibit cholesterol biosynthesis than the racemate. At first instance, the judge found that these data were not representative of the actual relative activity of the enantiomer over the racemate, which was determined in other tests to be the expected two-fold increase. Such a two-fold increase represents what is effectively the dilution effect of the racemate having half active and half inactive enantiomer.
These data were used in submissions to the Patent Office to support the argument that there was a ‘surprising’ advantage of the enantiomer over the enantiomer mixtures disclosed in the 981 Patent. The significance of this is that the claims of the Enantiomer Patent were argued to be novel on the basis that they provided a selection of a member of the class of molecule disclosed in the earlier patent, that had surprising activity. In order for such a selection to be novel, it must possess something more than its expected properties.
The court held that the statements in respect of the data presented in the specification and in the correspondence with the Patent Office were false or misleading. Furthermore, the data were directly used to in the submissions to the Patent Office to demonstrate the apparently surprising efficacy of the ‘R’ enantiomer in response to an objection made by the examiner that the claims were not novel. As the examiner’s objection was overcome after these submissions, the court held that the inference could be drawn that the use of these false or misleading data resulted in the patent being obtained.
Outcome
As a result of this decision, the claims of the original 981 Patent have been reaffirmed as covering atorvastatin. This patent is due to expire on 18 May 2012 after its extended term.
This decision also further clarifies the scope of the false suggestion or misrepresentation ground of invalidity under Australian law.
This article was written by Kirstie Murdoch, Senior Associate, Melbourne.
Endnotes
1. Ranbaxy Australia Pty Ltd v Warner-Lambert Company LLC [2008] FCAFC 82
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