Ranbaxy (UK) Ltd v Astrazeneca AB

A patent claim must be construed purposively by asking what the skilled person would understand the patentee to mean in the context of the specification and common general knowledge. The court must respect the language chosen and cannot ignore a claim integer or add a new one.

A Swiss-form claim for using an active ingredient to manufacture a medicament will normally be understood to require the resulting medicament to contain that active ingredient. The precise meaning remains dependent on the claim, specification and common general knowledge. A claim should not ordinarily be construed so broadly that it lacks enabling disclosure.

Ranbaxy sought a declaration that its proposed imported generic pharmaceutical would not infringe AstraZeneca’s patent for the use of high-optical-purity magnesium esomeprazole in manufacturing a medicament for inhibiting gastric acid secretion. AstraZeneca counterclaimed for infringement.

The product began with magnesium esomeprazole meeting the claimed optical-purity threshold, but racemate was added during manufacture so that the finished product no longer contained magnesium esomeprazole of that purity. The issue was whether the Swiss-form claim covered that process notwithstanding the composition of the finished medicament.

1. Construction of patent claims. Following Kirin Amgen v Hoechst Marion Roussel [2004] UKHL 46, [2005] RPC 9, and Virgin Atlantic Airways v Premium Aircraft Interiors [2009] EWCA Civ 1062, [2010] RPC 8, the words of the claim had to be construed purposively in context. The court could not ignore an integer or write a new integer into the claim.
2. Swiss-form claims. The history and purpose of Swiss-form claims, including the reasoning in EISAI/second medical indication G5/83, [1985] OJ EPO 64, supported the conclusion that the skilled person would normally understand such a claim to require the medicament to contain the active ingredient for which the new therapeutic use had been found. The claim’s exact meaning remained dependent on its language, specification and common general knowledge, as recognised in Monsanto & Company v Merck & Co Inc [2000] RPC 77.
3. The specification disclosed only the production and therapeutic use of magnesium esomeprazole of at least 99.8% enantiomeric excess, formulated with conventional carriers. It disclosed no analogue, derivative, alternative active ingredient or new method of making a medicament. Claim 1 therefore required the manufactured medicament to contain magnesium esomeprazole of that optical purity. The contrary construction would also create a serious insufficiency problem, illustrated by American Home Products Corporation v Novartis Pharmaceuticals [2001] RPC 8.
4. Ranbaxy’s finished product did not contain magnesium esomeprazole meeting the claimed optical-purity threshold. Ranbaxy was accordingly entitled to a declaration of non-infringement and AstraZeneca’s infringement counterclaim failed. The judge reserved the form of order if not agreed.