How to Infringe Swiss Form Claims

Mr Justice Kitchin recently considered the scope of Swiss form claims in the context of the proton pump inhibitor esomeprazole. The patent in suit (EP1,020,461), held by AstraZeneca, seeks to protect the magnesium salt of the S enantiomer of omeprazole (magnesium esomeprazole) with an optical purity of 99.8% enantiomeric excess1 and the use of that salt for the manufacture of a medicament for inhibition of gastric acid secretion. The patent comprises claims in various forms, including product per se claims and “Swiss form” claims. For the purposes of the English action the case turned on the construction of claim 1 only.

Before the English High Court2 Ranbaxy sought a declaration of non-infringement to enable it to import product into the UK which had been manufactured in India. AstraZeneca counterclaimed for infringement. There was no dispute between the parties that the manufacturing process utilised by Ranbaxy started with magnesium esomeprazole with an optical purity of 99.8% e.e. During the manufacturing process a quantity of omeprazole racemate is added; thus the finished product does not have the same optical purity.

According to AstraZeneca this was irrelevant, as the product to be imported by Ranbaxy was a direct product of a process in which magnesium esomeprazole with the requisite optical purity was used to manufacture a medicament. The use of the claimed compound to make any product, regardless of its final optical purity, was protected.

Ranbaxy on the other hand argued that their product did not infringe the claim as the medicament was not formulated using, and did not contain, magnesium esomeprazole with the required optical purity. Ranbaxy contended that the claim required the final medicament also to contain magnesium esomeprazole with an optical purity of 99.8% e.e.

Kitchin J. was persuaded by the arguments of Ranbaxy, finding that the skilled man would believe the patent to be directed to the production of optically pure magnesium esomeprazole and its use in particular therapies. Recognising that magnesium esomeprazole with an optical purity of 99.8% e.e. was new, he would understand the teaching of the claim to be towards the use of this new compound for manufacture of a medicament containing that compound. This, he said, would be reinforced by the skilled man’s understanding of patent claims and in particular claim 9 of the patent which claimed the compound itself and was thus not asserted against Ranbaxy (as it was not importing a product containing the esomeprazole salt of sufficient purity). Thus in the Judge’s view the Swiss form claim 1 was directed to a medicament which contained magnesium esomeprazole with an optical purity of 99.8% e.e.

Such a construction of the claim does appear to read a limitation into the claim, which is not otherwise present on a strict literal interpretation. After all, the claim specifies only the use of the esomeprazole salt for the manufacture of a medicament for a specific purpose, there is no limitation in the claim regarding the composition of the final medicament. Conversely Astra– Zeneca accepted there was no infringement of the product claim, and logically there should be no broadening of the claimed invention simply because the claim is framed in a Swiss form as opposed to direct form.

This is not the last we will hear of this patent. It is likely this decision will be appealed; the outcome of that appeal will no doubt affect whether the validity side of the case is put before a judge at the trial scheduled for early 20123. In the meantime the KRKA action concerning infringement and validity comes before the High Court later this year.

In a further twist the Opposition Division at the EPO earlier this summer held the patent to be invalid for lack of inventive step. AstraZeneca have already lodged an appeal against this decision. Furthermore in July the District Court of the Hague in the Netherlands gave its judgment on the validity of the ‘461 patent, finding the patent to be valid. This decision was given after the OD had made its pronouncement, though the OD decision was not brought to the Court’s attention as the case had been heard and closed prior to the OD hearing.

We are thus left with a complex picture throughout Europe. Given the value of the product, it is certain that there will be many more chapters in the coming months and even years.