Belgium’s UCB announced the Food and Drug Administration (FDA) has approved its epilepsy drug Vimpat (lacosamide) as an add-on therapy for the treatment of partial-onset seizures in adults.

The U.S. approval follows the EU Commission’s approval in August for the same condition, although it has been rejected by the European Medicines Agency (EMEA) as a treatment for diabetic neuropathic pain.

A spokeswoman for the company said UCB believed Vimpat was a potential blockbuster -meaning peak annual sales of at least $1 billion dollars - in epilepsy, and a successor to its mainstay Keppra, which is set to face competition from generics from November – its patent protection lasts until 2010 in Europe.

UCB withdrew its EU application to sell Vimpat (lacosamide) as a treatment for diabetic neuropathic pain at the end of September after a negative view from EMEA.

Vimpat had already received a "not approvable" letter in diabetic neuropathic pain from the FDA in July.

Analysts at West LB said the news was particularly good in light of that setback, and company shares rose.