Warner-Lambert v Generics (UK) (UKSC, [2018] UKSC 56, 2018)

Dhenne Avocats · 11 October 2026

Our analysis

Summary

The UK Supreme Court dismissed the appeal of Warner-Lambert (Pfizer Group) and allowed the cross-appeal of Actavis and Mylan: the Swiss-form claims to the use of pregabalin for treating pain (claim 1) and neuropathic pain (claim 3) were insufficient, since the specification made efficacy plausible only for inflammatory pain (para 15). The majority (Lord Sumption, Lord Reed and Lord Briggs) required the specification to disclose a scientific reason for thinking that the claimed therapeutic effect is real, across the full scope of the claim (paras 36 to 39). On infringement, the Justices agreed that there was none but differed on the applicable test (para 15). The judgment sets the English standard of plausibility for second medical use claims.

Facts and procedure

Warner-Lambert owns European Patent (UK) No 0934061, with a priority date of 24 July 1996, whose Swiss-form claims are directed to the use of pregabalin, marketed as Lyrica, for treating pain (paras 4 and 5). Since February 2015 Actavis has marketed a generic pregabalin, Lecaent, under a « skinny label » limited to epilepsy and generalised anxiety disorder, which are no longer patent-protected (para 8). Mylan and Actavis sought revocation of the patent; Warner-Lambert sued for infringement of claims 1 and 3 (para 9). Arnold J held those claims insufficient in so far as they covered central neuropathic pain, refused as an abuse of process an amendment sought after judgment, and found no infringement (paras 10 and 12). The Court of Appeal upheld the invalidity and the refusal to amend, but held that the wrong infringement test had been applied (paras 11 and 12).

The applicable law

Sufficiency is governed by sections 14(3) and 72(1)(c) of the Patents Act 1977, which correspond to Articles 83 and 138 EPC (para 18). For a Swiss-form claim, efficacy for the designated use is an implied technical feature of the claim, so that the specification must make the therapeutic effect plausible (paras 26 to 29, relying notably on T 609/02). Direct infringement falls under section 60(1)(c), the Swiss-form claim being a purpose-limited process claim (para 63).

Question

What disclosure does sufficiency require for a second medical use claim, must plausibility extend across the full scope of the claim, and can later data make up for the specification; and what test governs infringement of a Swiss-form claim by a generic sold under a skinny label (para 14)?

Decision

Plausibility is not a distinct condition of validity but the standard against which the specification must support the implied assertion of efficacy; the test is relatively undemanding but cannot be reduced to a test of good faith (para 36). A bare assertion or abstract possibility is not enough; the disclosure must give a reasonable prospect that the assertion will prove true, based on experimental data or a priori reasoning (para 37). Where the claimed condition embraces several pathologies, plausibility must be shown for each (para 39). Later data may confirm an effect already made plausible but cannot substitute for the disclosure (para 40). Here the animal models described predicted efficacy only for inflammatory pain, and neither the specification nor the common general knowledge gave any reason to suppose that pregabalin acts on central sensitisation (paras 42 and 48 to 51). The claims to neuropathic pain were invalid (para 54). Lord Hodge and Lord Mance, dissenting on this point, would have applied a lower threshold and upheld the claims limited to peripheral neuropathic pain (paras 181 to 185 and 195 to 196). On infringement, Lord Sumption and Lord Reed adopted an objective test based on the outward presentation of the product (packaging, labelling, patient leaflet) (para 84), Lord Briggs and Lord Hodge a test of subjective intention to target the protected market, and Lord Mance an objective test with reservations (para 15).

Key points for practice

• The specification of a second medical use claim must disclose a scientific reason, experimental or theoretical, for believing in the therapeutic effect (para 37).
• Where the claim covers several pathologies, plausibility must be established for each of them (para 39).
• Later data can only confirm an effect made plausible by the specification (para 40).
• Practical point: the scope of a therapeutic indication claim should match the data in the application; the judgment yields no majority on the infringement test for generics sold under a skinny label (para 15).

Provisions applied

European Patent Convention

Art. 54; Art. 69; Art. 83; Art. 84; Art. 138

National law

Patents Act 1977 (United Kingdom), sections 14(3), 14(5), 60(1)(c), 60(2) and 72(1)(c)

Case law cited

Warner-Lambert v Generics, [2016] EWCA Civ 1006 (decision under appeal) and [2015] EWHC 2548 (Pat); Biogen v Medeva, [1997] RPC 1; Conor Medsystems v Angiotech, [2008] RPC 28; Regeneron v Genentech, [2013] RPC 28; Prendergast’s Applications, [2000] RPC 446; Merrell Dow v Norton, [1996] RPC 76; Menashe Business Mercantile v William Hill, [2003] 1 WLR 1462; EPO, G 5/83, G 2/88, G 6/88, T 409/91, T 609/02, T 1329/04, T 578/06, T 1437/07, T 950/13, T 488/16, T 1673/11; BGH, Antivirusmittel (X ZR 51/86)

Related decisions

• T 609/02, Salk Institute, EPO, 27 October 2004, whose plausibility principle the Court adopted (paras 28 and 29).
• T 1329/04, Johns Hopkins University, EPO, 28 June 2005, cited on post-published data (paras 24 and 40).
• T 488/16, Bristol-Myers Squibb, EPO, 1 February 2017, cited to the same effect (para 24).
• G 5/83, Eisai, EPO, 5 December 1984, the origin of Swiss-form claims (para 2).

Prepared by Dhenne Avocats from the text of the decision (UK Supreme Court website, official PDF of the judgment), consulted on 11 October 2026. Only the official text is authoritative.