Ratio Decidendi
Patent infringement should be assessed in two stages: (1) does the variant infringe on a normal (purposive) interpretation of the claim? (2) if not, does the variant nonetheless infringe because it varies from the invention in a way that is immaterial? The reformulated Improver/Protocol questions apply to the second stage.
Facts
Eli Lilly held a patent for pemetrexed disodium, a cancer treatment. Actavis sought to market a product using pemetrexed diacid, a different salt form.
Judgment Summary
The Supreme Court held the Actavis product infringed. Lord Neuberger reformulated the approach to equivalents, holding that a two-stage test applies and that the doctrine of equivalents is part of English patent law.
Key Quotes
"The problem of infringement must be approached by addressing two issues, each relating to the scope of the monopoly: (i) does the variant infringe any of the claims as a matter of normal interpretation? (ii) if not, does the variant nonetheless infringe because it varies from the invention in a way or ways which is or are immaterial?"
— Lord Neuberger
Subsequent Treatment
The leading authority on patent infringement by equivalents in UK law.