Kirin-Amgen Inc v Hoechst Marion Roussel Ltd

Ratio Decidendi

Facts

Kirin-Amgen held a patent for the production of erythropoietin (EPO), a hormone that stimulates red-blood-cell production, made by recombinant DNA technology. Hoechst Marion Roussel (with TKT) manufactured EPO by a different method known as gene activation, which switched on the EPO gene already present in human cells rather than introducing an exogenous DNA sequence. Kirin-Amgen alleged infringement; the defendants said their process fell outside the claims and counterclaimed that the patent was invalid. The dispute turned on how the claims of the patent should be construed and whether the rival process fell within them.

Judgment Summary

The House of Lords held that the defendants' gene-activation process did not infringe, and took the opportunity to restate the English approach to patent construction. Lord Hoffmann, giving the leading speech, held that a patent claim must be interpreted purposively: the question is always what a person skilled in the relevant art would have understood the patentee to have been using the language of the claim to mean, read in the light of the specification and the common general knowledge at the priority date. He explained that this purposive construction is the bedrock, and that the older 'Protocol questions' derived from Catnic and Improver are merely guidelines that may help answer that single question — not a separate doctrine of equivalents, which English law did not then recognise as a means of extending protection beyond the claims. Applying that approach, the skilled reader would not have understood Amgen's claims, framed around a particular DNA sequence, to cover the conceptually different gene-activation route. Kirin-Amgen became the leading modern authority on claim construction, though the Supreme Court later reintroduced a doctrine of equivalents in Actavis v Eli Lilly [2017] UKSC 48.

Key Quotes

Subsequent Treatment