Pifzer has lost its appeal of a UK patent dispute with Allergan over Lyrica, one of the US pharmaceutical giant blockbuster drugs, with annual global sales of around $5 billion. It now hopes to take the appeal to the UK Supreme Court.

In its verdict last week, the London court upheld last year’s High Court ruling that the generic pregabalin, produced by Allergan‘s Actavis unit – at the time an independent company and recently acquired by Israel’s Teva Pharmaceutical Industries – did not infringe Pfizer patents. That court at the same time overturned Pfizer’s patent UK patent for use of Lyrica as a pain relief drug.

The High Court also charged Pfizer with threatened doctors and pharmacists for prescribing the generic. The company denied using threats but acknowledged at the time mistakes in communicating with the UK medical sector. Lyrica was initially developed by Pfizer as a treatment for epilepsy. Following the expiration of the patent for this indication in 2014, Actavis launched its low-priced version as a painkiller. Pfizer has also sued Dr. Reddy’s Laboratories of  India as well as Teva over their generic pregabalin products.

Lawyers for Actavis said the case has international implications as other European courts in Europe are having to deal with drug patents for secondary uses. The London decision “gives guidance,” they said. Pfizer’s UK sales of Lyrica total just under £250m, with most sales in the pain relief indication.  Lyrica is not only Pfizer’s best-selling drug but is seen to be as the world’s best-selling medication for treating diseases of the central nervous system.