Dawn of an English Doctrine of Equivalents: immaterial variants infringe

The Supreme Court's landmark judgment in the case of Actavis v Eli Lilly is a change of direction for the English law on patent infringement. It rewrites the existing infringement test and longstanding Improver/Protocol questions. In doing so it has adopted a doctrine of equivalents into the English approach. In our briefing, we examine the new two-step infringement test and consider how this approach, which focusses on immaterial variants, will impact patentees and defendants. We also review the Supreme Court's judgment on the use of a patent's prosecution history as an aid to interpreting a patent and the practical significance this will have for patentees during the prosecution stage of a patent and on future conduct of patent litigation.