BRUSSELS (Reuters) - The U.S. Patent and Trademark Office (PTO) is to review UCB's patent for its epilepsy drug Vimpat, the latest round in a legal battle between the Belgian pharmaceutical company and generic rivals.
U.S. pharmaceuticals group Argentum Pharmaceuticals, which challenged UCB's patent, said in a statement late on Monday that the PTO had granted approval for a review of the sole remaining U.S. patent of UCB's Vimpat drug, due to expire in March 2022.
The PTO had concluded that Argentum had established a "reasonable likelihood that it would prevail" in showing that certain claims made by UCB in the patent are "unpatentable", Argentum said, adding a decision was likely within a year.
UCB shares fell more than 6 percent in Brussels on Tuesday to a nine-month low.
This is just the latest in a legal battle over UCB's epilepsy drug Vimpat, which had sales last year of 679 million euros ($759 mln), of which about three quarters were in the United States.
UCB filed a number of lawsuits in 2013 against generic drug companies that were planning to make their own version of Vimpat. The Delaware district court, which has grouped the lawsuits, is expected to deliver its verdict in June.
UCB said it was aware of the latest development and that it remained confident that its patent for Vimpat was valid and would be upheld.
Argentum, a generic drug maker, said it works with pharmaceutical companies to reduce the cost of prescription drugs by challenging patents that they consider are not innovative and artificially support high drug prices.
Its shares were down 6.1 percent at 63.79 euros at 0945 GMT, one of the worst performers in the FTSEurofirst 300 index of leading European stocks.
Jan De Kerpel, analyst at KBC Securities, said the market had assumed the patent would hold and that this had served as a wake-up call, even if it was not the start of legal action.
"They have not won anything but the PTO has accepted that it will review it ... In my opinion the district court decision is more important. It is higher up the hierarchy and it is imminent, most likely in June," he said.
Reporting by Wout Vergauwen; Editing by Philip Blenkinsop and Susan Fenton