Supreme Court Introduces a Doctrine of Equivalents in the UK

The Supreme Court, in a judgment handed down today, determined that the claims of a UK patent may extend beyond the scope of what a skilled person would understand the language of the claims to mean. In doing so, it swept away the previous practice of the UK courts whereby a patent claim would provide only that monopoly which a reasonable skilled person, reading the claims in context, would think that the patentee was intending to claim.

The facts at issue concerned a claim that made reference to the drug "pemetrexed disodium". One allegedly infringing product contained pemetrexed dipotassium in place of the pemetrexed disodium. The lower courts had held that there was no direct infringement, on the basis that the language of the claims clearly required pemetrexed disodium, and that specific compound was not present in the product at issue.

On appeal, the Supreme Court held that a patent claim in the UK can in principle cover products and processes that are not embraced by the language of the claims as a matter of normal interpretation. In particular, products and processes that contain features differing from those specified in a patent claim (so-called "variant features") can nevertheless infringe if the variant features differ from the claimed invention only in immaterial ways. The Court set out a three-part test for determining whether or not a given variant product or process would infringe. The relevant considerations focus on whether or not the variant makes use of the inventive concept revealed by the patent, whether or not that would be clear to a skilled person, and whether or not the patent as a whole makes it clear thatstrict compliance with the literal meaning of the claims was essential.

On the facts of the case, the patentee was able to argue successfully that a patent claim that referred to pemetrexed disodium did indeed cover a product that contained pemetrexed dipotassium in place of the pemetrexed disodium.