The UK Supreme Court has today handed down its highly-anticipated decision in a patent dispute between Pfizer and two generic pharmaceutical manufacturers, Actavis and Mylan, relating to Pfizer’s blockbuster pregabalin product, which it sells under the trade name “Lyrica”.

The Court ruled that Pfizer’s patent was invalid as it had not properly established the claimed therapeutic indication of treating neuropathic pain and that Actavis’ sale of its generic version of pregabalin for indications other than neuropathic pain did not infringe the patent.

Dr Yohan Liyanage, partner at Linklaters, comments: “Today’s judgment addresses a number of significant issues, including whether the plausibility test is an element of assessing whether a patent is sufficient, whether patents can be amended after trial and what is required to establish infringement of a second medical use patent.

“Overall, the judgment will be disappointing for innovator pharmaceutical companies, as it maintains a threshold plausibility test for therapeutic uses of previously known drugs, while simultaneously making it difficult for owners of these patents to prove that their patents are being infringed.

“The UK High Court and Court of Appeal held that Pfizer’s patent was invalid because it was insufficient across the breadth of the claim for the treatment of pain. Both courts held that the patent made plausible the use of pregabalin for the treatment of certain types of pain (namely inflammatory pain and peripheral neuropathic pain), but did not make plausible the treatment of all types of pain (in particular, central neuropathic pain). Pfizer applied to amend the patent after the first instance judgment to limit the claims to the treatment of neuropathic pain, but both the High Court and Court of Appeal held that it was too late to apply to amend the patent at that stage, as it would require a further trial on this issue.  

“Pfizer argued on appeal to the Supreme Court that plausibility of disclosure was not a requirement for sufficiency under UK law, and all that is required is to show that the invention works. However, the Supreme Court, drawing on the case law of the European Patent Office, agreed with the lower courts that plausibility of disclosure is a requirement for sufficiency under UK law, holding that there must be a “reasonable prospect” that the claimed indication would prove to be true.

“The Supreme Court went even further than the lower courts in finding that Pfizer’s patent did not make plausible any type of neuropathic pain, and confirmed that Pfizer’s patent was invalid. The Supreme Court also confirmed that Pfizer’s application to amend the patent after trial was made too late. Pfizer should have applied to amend its patent before the trial started.

“The Supreme Court also unanimously held that Actavis was not infringing Pfizer’s patent, although the judges did not agree on what was required to establish infringement of second medical use patents: some said that Actavis’ intention was relevant, while others said that the labeling on the product packaging was determinative. The judgment, therefore, does not provide legal clarity on this area, and leaves scope for further dispute in the future as to the requirements for establishing infringement of second medical use products.”