New test for patent infringement in the UK

On Wednesday 12 July 2017, the Supreme Court, the country’s highest court, handed down a judgment on patent infringement that delivers the most significant change in the law of patent infringement in the last decade, and probably the biggest change in the career of most patent attorneys. 

The decision covered a number of issues, but the most important aspect of the decision means that patents might in future be found to be infringed by actions that would not previously have been considered infringing.  The case moves the balance between providing fair protection to the patent owner and providing legal certainty to third parties firmly in favour of the patent owner, to the detriment of competitors.


The case (Actavis v Eli Lilly) concerned a drug for treating cancer, specifically an “antifolate” called pemetrexed disodium, sold under the trade name Alimta.  This compound was known to have anti-cancer properties, but had such violent, sometimes even fatal, side effects that it could not be used.

However, Eli Lilly discovered that when combined with vitamin B12, the side effects were largely avoided.  Eli Lilly therefore sought a patent claiming the combination of an antifolate and a methylmalonic acid lowering agent, of which vitamin B12 is an example.

During examination of the patent application, the patent office objected that Lilly had not shown that the invention would work with any antifolate and any methylmalonic acid lowering agent.  Accordingly, Lilly were forced to limit their claims initially to pemetrexed (rather than the general class of antifolates) and vitamin B12 (as opposed to methylmalonic acid lowering agents generally). Eventually, to secure grant, the claims (which define the scope of protection) were limited to the combination of vitamin B12 and the specific compound of pemetrexed, pemetrexed disodium.

Actavis sought to produce a competing product using vitamin B12 with a different pemetrexed compound, specifically (a) pemetrexed diacid, (b) pemetrexed ditromethamine, or (c) pemetrexed dipotassium.

These compounds all contain the same active ingredient, pemetrexed, and work in exactly the same way, but they lack the “disodium” ion, using chemically equivalent, but different, ions in its place.  Actavis asked the court to declare that none of these compounds would directly infringe the patent.


Both the High Court and the Court of Appeal, following the normal approach to patent infringement, found that although the active ingredient was the same, there was no direct patent infringement, since having specified the disodium compound of pemetrexed in their claims, the scope of Lilly’s monopoly was limited to drugs including that compound.

The Supreme Court has now overturned that decision. The Court agreed that “[a]s a matter of ordinary language, it is quite clear that the only type of pemetrexed compound to which the Patent’s claims expressly extend is pemetrexed disodium”. 

But that was not the end of the story, the Court has now explicitly approved a test that makes it possible to find patent infringement even where under normal interpretation, there would be no infringement, setting out a two-step test for determining infringement, where a variant of a product is produced:

(i) does the variant infringe any of the claims as a matter of normal interpretation; and, if not,

(ii) does the variant nonetheless infringe because it varies from the invention in a way or ways which is or are immaterial?

Thus, whilst it was clear that, for example, the dipotassium salt is not a disodium salt, the difference was considered immaterial to the way the product worked. 

In justifying that the difference was immaterial, the Court determined that it was obvious that the variant achieved substantially the same result in substantially the same way and that the reader of the patent would not conclude that the patentee intended that strict compliance with the literal meaning of the relevant claim was an essential requirement of the invention.


This decision may be welcomed by patent owners as it extends the scope of protection available in the UK, to cover competing products that use the same inventive concept, even if they do not fall within the words used to define the invention.  The decision was intended to make the UK position more similar to that elsewhere in the EU, and harmonisation may also be appreciated by the business community.

On the other hand, the decision is bad news for copycats and indeed legitimate competitors, who look to produce competing products because it makes it more difficult to ascertain the scope of protection and reduces legal certainty.


It would be advisable to revisit any infringement opinions in light of this decision.  In particular, if you have been advised that your product should not infringe a competitor’s patent, there is now a risk that the patent might be infringed by “equivalence”. 

Similarly, if you have been advised that one of your competitors does not infringe your patent, on the basis that they have worked around the scope of the invention defined in the claims, it would be worth having the opinion revisited, since if the inventive concept has been taken, there may be infringement nonetheless.

If you have any questions, do not hesitate to contact one of our patent attorneys.

© 2018 Wilson Gunn