Kirin-Amgen Inc v Hoechst Marion Roussel Ltd

Kirin-Amgen, Inc. v Hoechst Marion Roussel Ltd.^[1] is a decision by the House of Lords of England and Wales. The judgment was issued on 21 October 2004 and relates to the scope to be accorded to patent claims, including the doctrine of equivalents. The case and subsequent judgment affirmed principles from a prior case, Catnic Components Ltd. v. Hill & Smith Ltd.

The issue was whether the claims of a European patent granted to Kirin-Amgen, Inc. were infringed by Transkaryotic Therapies Inc. ("TKT") and Hoechst Marion Roussel Ltd in a situation where there was a remarkable similarity between the technologies employed by the two parties for producing the hormone erythropoietin. Infringement was not found due to the language used in the claims of the Amgen patent.

The reasoning in the judgment has presently formed a basis for the current practice of the UK Intellectual Property Office, and other countries that take great consideration of the legal implications of British case law when assessing whether a patent has been infringed by a device or process which is equivalent to the patented invention under the doctrine of equivalents.