On 14 November, the Supreme Court handed down its judgment on the validity and infringement of the second medical use patent that protected Pfizer’s Lyrica® (pregabalin) for the treatment of various types of pain. In Warner-Lambert Company LLC v Generics (UK) Ltd (t/a Mylan) & Anor [2018] UKSC 56, the Court decided that the patent held by Warner-Lambert (a company in the Pfizer group) was invalid for insufficiency, because it did not render it plausible that pregabalin would be effective to treat all of the claimed types of pain. The Court also held that, had the claims been valid, they would not have been infringed by a “skinny label” generic version of pregabalin that had the protected indications carved out. However, the five judges of the Court were not in agreement on several key points.

Background to the case

Warner-Lambert’s patent included claims to pain, inflammatory pain (caused by external stimuli) and neuropathic pain (caused by damage to the nervous system). The patent disclosed the results of three pre-clinical animal models used to test drugs for various kinds of pain, which demonstrated that pregabalin was effective in treating inflammatory pain; the parties disputed whether these results, together with the other material in the patent, rendered it plausible that pregabalin would also be effective to treat neuropathic pain (peripheral or central).

Pfizer Limited holds the marketing authorisation for Lyrica (pregabalin) for the treatment of both peripheral and central neuropathic pain, as well as epilepsy and GAD, these latter two indications no longer benefiting from any form of exclusivity. Issues have arisen as to the steps those obtaining authorisation of copy products should take to avoid infringement of the protected indications.

Actavis marketed a “skinny label” generic version of pregabalin, which included in its summary of product characteristics and patient information leaflet only the epilepsy and GAD indications. This is because the pain indications were “carved out” of the product information to avoid infringing Pfizer’s patent. However, in 2014 Mylan and Actavis brought patent proceedings arguing that the claims of Warner-Lambert’s patent that covered pain and neuropathic pain were invalid, and Actavis argued that, even if the claims were valid, the sale of its skinny label products did not infringe these claims.

Decisions of the Court

The dispute about the pregabalin patent has been long-running. In 2015, at first instance, Arnold J held the patent partially invalid for insufficiency and also held that, had the relevant claims been valid, they would not have been infringed. Following the trial, Warner-Lambert applied to amend its patent, to narrow its claim to neuropathic pain to cover only peripheral neuropathic pain, but this application was refused. In 2016, the Court of Appeal upheld Arnold J’s decisions on amendment, construction and insufficiency; the Court of Appeal proposed a different test for infringement but, since the relevant claims of the patent were held to be invalid, nothing turned on this point.

The judgment of the Supreme Court, which was delayed a number of times, makes clear that the judges had different views on the various questions to be answered:

  • Amendment: The Court unanimously rejected Warner-Lambert’s appeal against the refusal of its amendment. The Court held that a patentee’s right to amend its patent under the European Patent Convention 2000 is subject to the national court’s rules of procedure, and it maintained the Court of Appeal’s application of the English procedural rules on post-trial amendments.
  • Construction: The Court upheld the decisions of the High Court and Court of Appeal on the construction of the “neuropathic pain” claim in the patent. Warner-Lambert had argued that this claim should be construed narrowly as referring only to peripheral neuropathic pain, in light of the description of the patent and applying a presumption that the court should prefer the construction that results in the claim being valid. However, the Court held that the claim (read in light of the description) should be construed broadly to cover all types of neuropathic pain and, as the claim was not ambiguous, there was no need to use the “validating principle” to prefer a narrower construction.
  • Sufficiency: Three of the five judges held that the material in Warner-Lambert’s patent did not render it plausible that pregabalin would be effective to treat neuropathic pain generally, or peripheral neuropathic pain specifically. The judges said that in the context of a second medical use claim, the patent must disclose a “reasonable prospect” that the claimed compound would be effective in treating the claimed disease, and that this must be based on a “direct effect on a metabolic mechanism specifically involved in the disease”. However, the two dissenting judges said that this requirement puts the test for sufficiency too high; they said that when applying the lower threshold, Warner-Lambert’s patent contained enough material to make it plausible that pregabalin would be effective to treat peripheral neuropathic pain.
  • Infringement: While the Court found the patent claims to be invalid, the judges did comment on infringement. However, these comments are obiter and not binding in future cases. Four of the five judges held that Warner-Lambert’s second medical use claims (if valid) would not have been infringed by the sale of skinny labelled product. However, they differed as to the reasons. Lord Reed and Lord Sumption held that the sole criterion for infringement is “whether the product as it emerges from the manufacturing process, including any labelling or accompanying leaflet, is presented as suitable for the uses which enjoy patent protection.” Since the product information for the skinny labelled product only referred to the treatment of epilepsy and GAD, its sale would not infringe the pain patent. In contrast, Lord Hodge and Lord Briggs said that infringement depends on whether the alleged infringer subjectively intended to target the patent protected market which, on the facts, Actavis did not. Lord Mance took a different approach again, holding that the test depends on the objective appearance of the product but that (i) in rare cases, the context may make it obvious that this is not to be taken at face value, and (ii) there may be circumstances in which the generic manufacturer should positively exclude use for the patent-protected purpose. He declined to express a view on how that test would be applied in this case.


Whether a second medical use patent contains sufficient material to render it plausible that the claimed compound will be effective to treat the claimed disease will always be a highly fact-specific issue, dependent on the detailed information contained in the patent and the state of the common general knowledge at its priority date. However, in light of the difference of opinion between the Supreme Court judges, there will also be plenty of scope for future argument as to the legal principles and their correct application.

In relation to the Supreme Court’s non-binding comments on infringement, the different tests proposed by the Court will lead to uncertainty for patent holders in the future, although it seems likely that it will be more difficult for patent holders to prove their second medical use patents have been infringed.