Court of Appeal confirms $5b Pfizer drug patent invalid.

The Court of Appeal has handed down its decision in the patent dispute relating to Pfizer’s $5 billion drug Lyrica® and its prescribed use to treat neuropathic pain. In summary, the Court of Appeal upheld the first instance decision, maintaining the finding of insufficiency and non-infringement. A finding that Pfizer was liable for making groundless threats was also upheld. Pfizer has indicated that it will seek leave to appeal to the UK Supreme Court.

The use of pregabalin, the active ingredient of Lyrica®, in the treatment of pain is the subject of European (UK) Patent No.0934061 (the Patent) owned by Warner-Lambert. Pfizer has the rights to market Lyrica® in the UK. At first instance, Generics (UK) Limited (trading as Mylan) and Actavis made an application to revoke the Patent, whilst Pfizer counter-claimed against Actavis for infringement on account of the sale of its generic pregabalin. There were a number of associated decisions including an application by Pfizer for a preliminary injunction against Actavis.

At the heart of the decision at first instance and appeal were claim 1 of the Patent, directed to the treatment of pain, and also claim 3, limited to neuropathic pain. At first instance, the High Court ruled that both claims were invalid as a result of being insufficient. Also, even if certain claims were valid, it was deemed Actavis did not infringe. The insufficiency attack was centred around whether it was plausible from the Patent that pregabalin would be effective in treating any type of pain other than those for which animal models were provided. For much of the proceedings the attacks were focussed on claim 1 and the distinction between neuropathic and inflammatory pain. Only at a late stage was an argument raised based on the difference between peripheral and central neuropathic pain. Ultimately this latter argument proved successful in invalidating claim 3, since it was found that the Patent did not plausibly teach that treatment of central neuropathic pain would be successful, although it was considered to plausibly teach the treatment of peripheral neuropathic pain and therefore be sufficient for this subject matter. The significance of the distinction between peripheral and central neuropathic pain appeared not to be recognised until late in proceedings. On this basis and following the trial, Pfizer applied to amend claim 3 but the post-trial timing of the request was considered an abuse of process, since it was deemed the application could have been made earlier and the amendment may have necessitated a further trial on validity.

The concept of “plausibility” is an increasingly referred to test in patent litigation and was discussed at length, with the Court of Appeal considering that the requirement of plausibility is a “low threshold test”, designed to prohibit speculative claiming but also allowing patents to be valid when a prediction based on little evidence turns out to be correct. Despite this low threshold, and Pfizer's argument that the claim construction adopted by the Judge at first instance was wrong and that inter alia claim 3 should have been construed narrowly to exclude central neuropathic pain, the Court of Appeal agreed with the judge at first instance thereby upholding the earlier finding of insufficiency.

With respect to Pfizer's application to amend, the Court of Appeal also upheld the initial decision, stating that for amendment to have been allowed, Pfizer should have indicated no later than commencement of the first trial that amendment of claim 3 would be sought in the event that it was found invalid. Whilst there was no case of infringement to answer, the Court of Appeal made a number of obiter comments regarding infringement of Swiss-form claims. It recognised that the scope of such claims is not uniformly interpreted between jurisdictions but commented that a manufacturer should take “all reasonable steps” in their power to prevent a drug from being used to treat a patented indication. These comments mirror earlier comments made in the associated appeal of Pfizer's preliminary injunction.

Patent holders may be pleased to see that the hurdle of plausibility has been defined as a low one to overcome. Generic companies on the other hand have been put on notice that the act of carving out a patented indication from a drug label is required, but not necessarily enough, to avoid a potential finding of infringement of a second medical use patent. Patent holders in general should also be mindful that any desired claim amendments should be identified, even on a conditional basis, as early as reasonably appropriate.