Eilidh Pugh, Pharmaceutical Patent Attorney, AdamsonJones.

The UK Supreme Court has handed down its much-anticipated decision in WarnerLambert Company LLC v Generics (UK) Ltd t/a Mylan and Actavis. The case is important because it is the first time the Supreme Court has provided direction on two important issues: the role of “plausibility” in deciding whether an invention based on a new medical use is adequately disclosed in a patent, and how infringement of such a patent is to be assessed.


The patent in question concerned the use of pregabalin for the treatment of pain.

Pregabalin was already known for the treatment of other indications, so the claims of the patent are in the “Swiss” form, i.e. purpose-limited process claims: “Use of pregabalin for the preparation of a pharmaceutical composition for treating pain”.

Actavis manufactures a generic pregabalin product that was suitable for treating pain but was not explicitly marketed for that use.

The lower Courts held the patent to be invalid because the invention was not adequately disclosed, and the Supreme Court rejected Warner-Lambert’s appeal against that decision.

Sufficiency and the plausibility test

The majority of the judges took the view that a plausible disclosure of efficacy requires there to be technical information in the specification to show how the invention works for the uses covered by the claim. As a result, they held that, while the disclosure of the patent supported claims referring to the treatment of inflammatory pain, it did not do so for any kind of neuropathic pain.

Their decision highlights the importance of including a technical rationale for any assertion of therapeutic efficacy in a patent application.


The judges agreed that if the relevant claims had been valid, they would not have been infringed. However, their remarks on this topic were obiter and not binding, and there were considerable differences in their reasoning. Some considered the sole criterion for infringement of Swiss claims to be whether the product, including any labelling or accompanying leaflet, is presented as suitable for the new patented use. If not, there is no infringement. This appears to be good news for generics as it indicates that generic products which do not identify the patented use on their packaging or instructions (“skinny labelling”) would not infringe a Swiss claim in the UK. However, other judges felt the intention of the manufacturer should also be taken into account. Generics therefore cannot rely solely on skinny labelling just yet.

More to come

This decision means that for a patentee it is important to include enough technical information in a patent for a new use of a known drug for that new use to be plausible. For a generic manufacturer seeking to avoid infringement, however, the position remains unclear: is skinny labelling sufficient, or is it necessary to make it clear that the generic product is not to be used for the patented use, or even to take active steps to prevent it being used in that way? Hopefully, definitive rulings on this point will be forthcoming soon.

If you have any queries on this topic, please contact Eilidh Pugh at eilidh.pugh@adamson-jones.co.uk.