In a decision following a long series of judgments which raise a number of novel and interesting legal and commercial points, the Supreme Court has finally held1 that Warner Lambert's second medical use patent for the use of pregabalin in the treatment of neuropathic pain is invalid on grounds of insufficiency.
The judges of the Supreme Court have provided clarification as to what degree of evidence of efficacy must be included in the patent specification to satisfy the statutory requirement of sufficiency. The judges also opined, obiter, as to the correct test for infringement of a second medical use patent drafted in the so-called 'Swiss form' – use of substance X for the preparation of a medicament for treating indication Y. The judges were unable to agree on this latter issue, and as second medical use patents are of increasing importance to the pharmaceutical industry, this is unlikely to be the last word on the subject.
In this article, rather than attempting to summarise each technical issue discussed by their Lordships, the authors will draw out and discuss the principles decided which are of general applicability to second medical use patents containing Swiss form claims. The authors also consider the applicability of the decision to patents containing second medical use product claims, which are now the only form in which new second medical use patents can be granted.
Background
The case concerns the pharmaceutical compound pregabalin, marketed by Warner-Lambert (part of the Pfizer group) as Lyrica. The drug is used for treatment of epilepsy, generalised anxiety disorder and neuropathic pain. Pregabalin itself was protected by a patent which expired in May 2013. The patent in dispute, EP(UK)0934061 ('the patent'), is concerned with the use of pregabalin for treatment of pain, particularly neuropathic pain. The drug is a best-seller for Warner-Lambert – in Arnold J's first judgment in respect of Warner Lambert's application for an interim injunction,2 annual sales in the United Kingdom alone were said to be in excess of £200 million in 2013. According to the evidence submitted to the court, at least 50 per cent of those sales related to treatment of pain.
After expiry of the patent protecting pregabalin per se, Actavis obtained marketing authorisation to launch a generic pregabalin product (which it intended to sell under the name Lecaent). This dispute concerns whether Warner-Lambert can compel Actavis to take steps to ensure that Lecaent is not dispensed for the treatment of pain, in respect of which the patent applies.
Second Medical Use Patents
Given the enormous costs involved in developing new pharmaceutical compounds, the pharmaceutical industry has been active for many years in searching for new medical uses for known compounds. The advantages are obvious: known compounds will already have been tested for safety, and can therefore be brought to market for new uses far more quickly and cheaply than entirely new compounds.
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