The first of two judgments handed down by Mr Justice Kitchin this morning, Ranbaxy v AstraZeneca [2011] EWHC 1831 (Pat) concerns a declaration for non infringement sought by Ranbaxy in respect of its proposed importation of a product for the treatment of complaints caused by excess gastric acid.

AstraZeneca is the proprietor of a patent (EP(UK) 1 020 461) on the use of esomeprazole (right) for the inhibition of gastric acid secretion. It markets this treatment under the trade name “Nexium”. Esomeprazole is the S, or (-), enantiomer of the racemic mixture known as omeprazole (itself marketed since 1988 as “Losec”).

The patent requires the use of magnesium esomeprazole with a high optical purity (expressed in terms of enantiomeric excess (e.e.), i.e. the fraction of the compound present as the major enantiomer less the fraction of the compound present as the minor enantiomer). It was drafted in the “Swiss form”, and claims were directed to the use of magnesium esomeprazole with an optical purity of ≥ 99.8 % e.e. for the manufacture of a medicament for the inhibition of gastric acid secretion.

Ranbaxy is an importer of generic pharmaceuticals. As noted, it sought a declaration of non-infringement in respect of plans to import a pharmaceutical product that it (unsurprisingly given the nature of the declaration sought) considered did not infringe AstraZeneca’s patent. AstraZeneca, for its part, counterclaimed alleging that it did.

The product for which Ranbaxy sought its declaration was formed from a starting material of magnesium esomeprazole with an optical purity of ≥ 99.8 % e.e. To this was added a quantity of omeprazole racemate. The resultant product accordingly no longer contained magnesium esomeprazole of that optical purity.

AstraZeneca contended that this was still an infringement – arguing that the product Ranbaxy wished to import “was the direct product of a process in which magnesium esomeprazole with an optical purity of ≥ 99.8 % e.e. is used to make a medicament for the inhibition of gastric acid secretion.”

Ranbaxy, by contrast, contended for a different interpretation – arguing that the product it wished to import was not formulated using, and did not contain, magnesium esomeprazole with an optical purity of ≥ 99.8 % e.e.

It all came down to the interpretation of the claims. Claim 1 read:
“The use of a magnesium salt of (-)-5-methoxy-2[[(4-methoxy-3,5-dimethyl-2-pyridinyl)methyl]sulfinyl]-1H-benzimidazole ((-)-omeprazole) with an optical purity of ≥ 99.8% enantiomeric excess (e.e.) for the manufacture of a medicament for the inhibition of gastric acid secretion.”
Ranbaxy contended that this was limited to use of magnesium esomeprazole with an optical purity of ≥ 99.8% e.e. for the manufacture of a medicament which contains magnesium esomeprazole of that purity. AstraZeneca, however, argued that this was a simple process claim and that as such, it was not limited to the manufacture of specific products but extended to the use of the claimed process to make any product. Accordingly, it stated that the claim covered use of a magnesium salt of esomeprazole with an optical purity of ≥ 99.8% e.e. for the manufacture of a medicament for the inhibition of gastric acid secretion irrespective of whether or not the medicament itself contained magnesium esomeprazole at all.

Following a rather nice potted history of “Swiss form” claims and second medical use (found between [42] and [61]), the Judge addressed the “crucial question, namely what the skilled person would have understood the patentee to be using the words of claim 1 to mean.” Diving into the specification, Kitchin J noted that the skilled person:
[67] “Recognising the teaching of the specification that magnesium esomeprazole with an optical purity of ≥ 99.8 % e.e. is new, he would nevertheless understand claim 1 to be directed to the use of such magnesium esomeprazole to manufacture a medicament which contains that active ingredient.”
This understanding would be backed up by appreciation that the claims themselves fell into various sets
[69] “Claim 1, as a Swiss form claim, and forming as it does the first of a cascade of claims directed to the use of optically pure magnesium esomeprazole to manufacture a medicament for the treatment of different or more specific uses, would … naturally be understood as requiring the medicament to contain the active ingredient for which the claimed use has been found.”
Accordingly, Ranbaxy was entitled to its declaration of non infringement and AstraZeneca’s counterclaim for infringement failed.

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