Supreme Court defines plausibility in the context of sufficiency

A majority postulates a new "outward presentation test" to deal with the infringement of second medical use patents.

For the first time the Supreme Court has grappled with the thorny questions of how the concepts of sufficiency and infringement are to be applied to a patent relating to a second medical use of a known pharmaceutical compound.


The dispute is between Pfizer (parent company of Warner-Lambert) and Generics (UK) Ltd (trading as Mylan) and Actavis Group concerning the validity of and infringement of Warner-Lambert's pregabalin patent. The patent claims pregabalin (marketed as "Lyrica") for the treatment of pain, using the "Swiss form" where the invention is identified as neither a product nor a method of treatment but as a manufacturing process for a novel purpose. Claim 2 of the patent is limited to the treatment of inflammatory pain, and claim 3 is limited to the treatment of neuropathic pain.

Actavis marketed a generic pregabalin product under the brand name “Lecaent”, under a “skinny label”, i.e. for the treatment of some indications only. The Summary of Product Characteristics and the Patient Information Leaflet state that the conditions for which Lecaent is indicated are epilepsy and general anxiety disorder (GAD), for both of which patent protection has expired.

Mylan and Actavis claimed the revocation of the patent on the ground of insufficiency, and Warner-Lambert claimed against Actavis for infringement of Claims 1 and 3.

At first instance Arnold J held that Claim 1 (pain) and Claim 3 (neuropathic pain) were invalid because there was only sufficient disclosure in the specification to support the claim that pregabalin was efficacious in the treatment of inflammatory pain and peripheral neuropathic pain, but not central neuropathic pain. Since the judge construed Claim 1 as extending to all pain and Claim 3 as extending to all neuropathic pain, including central neuropathic pain, both claims failed for insufficiency. The judge also rejected as an abuse of process an application after judgment to amend the patent by narrowing the claims in terms which would arguably have made them valid. Broadly the Court of Appeal upheld the judge’s findings including his decision on abuse of process. 

Summary of Conclusions

The court unanimously affirmed the view of both courts below that Claim 1 extends to all pain and Claim 3 to all neuropathic pain, whether peripheral or central. It also unanimously affirmed Arnold J’s decision rejecting Warner-Lambert’s application to amend the patent so as to limit the scope of these claims.


The court held by a majority (Lord Sumption, Lord Reed and Lord Briggs), that the disclosure in the specification supported the claims so far as they extend to inflammatory pain but not to any kind of neuropathic pain. It followed that Claims 1 and 3 failed for insufficiency, and that Warner-Lambert’s appeal must be dismissed and Actavis’s and Mylan’s cross-appeal allowed.


Lord Sumption, together with Lord Reed, Lord Hodge and Lord Briggs, held that if Claims 1 and 3 had been valid, they would not have been infringed. They differed, however, as to the reasons and in particular the test to be applied in order to determine infringement of purpose limited process claim.

Lord Sumption and Lord Reed considered that the intention of the alleged infringer is irrelevant and that the sole criterion of 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. This new test, derived from German law, was termed "the outward presentation test". The judge found that Lecaent was sold with patient information leaflets to the effect that it was for the treatment of epilepsy and GAD.

Lord Mance agreed that the test depends on the objective appearance and characteristics of the product as it is prepared, presented and put on the market, but left open the possibility that (i) in rare cases the context may make it obvious that these are 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.

Lord Hodge and Lord Briggs preferred the view of Arnold J that the test is whether the alleged infringer subjectively intended to target the patent-protected market. Arnold J found that they did not.

Looking at the judgment in more detail…

Sufficiency and Plausibility

Sufficiency and the related concepts of enablement and plausibility are designed to ensure the patentee provides full public disclosure of their invention in exchange for the granted patent.  Under section 72(1)(c) of the Patents Act 1977 a patent may be revoked on the grounds that "the specification of the patent does not disclose the invention clearly enough and completely enough for it to be performed by a person skilled in the art". A patent may be found invalid on the grounds that the invention is insufficiently disclosed.

Generally an invention for a new product or process will be sufficiently disclosed if the specification enables it to be “performed”. But the assumption is not correct in the case of a second medical use patent. The invention is not the compound or the process of its manufacture both of which the skilled person already knows from the prior art disclosed in the original patent. The invention consists in the new purpose for which the product is to be manufactured.

Without some disclosure of how or why the known product can be expected to work in the new application, it would be possible to patent the manufacture of known compounds on a wholly speculative basis, without having invented anything at all, in the hope that trial and error might in due course show that the…

Full article available on PatentHub

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