The High Court has refused three Ranbaxy companies a declaration that manufacturing, importing or selling their proposed atorvastatin calcium product in Ireland would not infringe Warner-Lambert’s Irish patent. Mr Justice Clarke ruled on 10 July 2007 that the patent covers both individual trans enantiomers and mixtures of them, so Ranbaxy’s product, based on the R-trans enantiomer, would infringe.
The case concerned the meaning of Warner-Lambert’s Irish Patent No. 60014. The patent relates to compounds intended to inhibit an enzyme involved in cholesterol production. Ranbaxy argued that, properly interpreted, it covered only a racemic mixture: equal amounts of two mirror-image forms of a compound. It said its proposed product was not such a mixture. Warner-Lambert argued that the patent also covered the individual forms and other mixtures.
The dispute was about the scope of the patent, not its validity. The judgment notes that validity was the subject of separate proceedings, and no challenge to validity was brought in this case.
In construing the patent, the judge considered its claims, description and drawings from the perspective of a skilled reader in the relevant field. The patent described four possible forms of the compounds and expressly excluded the two “cis” forms. The judge considered that a natural reading left the two “trans” forms within the claimed invention. He also found that the chemical diagrams had to be read in context, rather than treated as necessarily indicating a racemic mixture wherever the same drawing appeared.
Ranbaxy relied on the patent’s reaction sequence, which the experts agreed ended in a racemic mixture, and argued that the identical diagram in the main claim should carry the same meaning. The judge rejected that interpretation. He also considered whether it was rational to read the patent as excluding the R-trans form, which the skilled reader would understand to hold most of the compound’s potency. He was not satisfied that the patent clearly limited its claims to a racemate.
The judge considered related decisions from other jurisdictions, including the United Kingdom, Australia, the United States and Canada, while noting that differences in the patents, law and evidence required caution. He found the UK Court of Appeal’s reasoning persuasive and applied it in construing the Irish patent.
Having concluded that the patent included both trans forms and any mixture of them, the judge found that Ranbaxy’s proposed R-trans-based product would infringe. The requested declaration was therefore refused. The judgment does not determine the separate patent-validity proceedings.