Monday, 18 July 2011

Second medical use patent not infringed by generic manufacturer

"Swiss Style Claims", as my Dictionary will tell you, were designed to overcome the exclusion in Article 52(4) the European Patent Convention of "methods for treatment of the human or animal body by surgery or therapy and diagnostic methods practised on the human or animal body." The Swiss Federal Intellectual Property Office published Legal Advice (way back on 30 May 1984, reproduced by the EPO in OJ EPO 581) on the patentability of compounds used in the manufacture of a medicine for the treatment of a disease. Such claims have historically been encountered in "second medical use" situations (also defined in my Dictionary), where a compound used to treat condition A is found to work for condition B too. Sindinafel citrate is a good example: it is a vasodilator, a drug that has the effect of dilating the blood vessels which works by improving blood circulation, and was originally used to treat angina. A second medical use was spotted and it has been very successful under the brand name Viagra.

Swiss style claims became unnecessary after the revisions to the EPC in 2000, but because the patent in suit remained pending for so long the recent case of Ranbaxy (UK) Ltd. v AstraZeneca AB [2011] EWHC 1831 (Pat) (15 July 2011) required Kitchin J to interpret one. Ranbaxy wanted a declaration of non-infringement to clear the way to import a generic drug for treating gastric acid related conditions from India. The claim in question 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.
In Ranbaxy's product the compound was diluted by the addition of omeprazole racemate, so the optical purity in the drugs was not as high as the claim stipulated. The judge interpreted the claim, purposively, to be to the use of that compound with that level of purity. The specification did not mention any variation of the compound or adding other active ingredients, and as the claim was to a new therapeutic use of a medicament containing a known active compound, the medicament must contain that compound. A non-Swiss style claim might have been capable of a wider interpretation, but the form of the claim meant that it was strictly limited to the compound it stipulated. Ranbaxy got their declaration.

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