Lundbeck has been boosted by the news that regulators in the USA have given the green light to its severe epilepsy drug Onfi.

The US Food and Drug Administration has approved Onfi (clobazam) as adjunctive therapy for seizures associated with Lennox-Gastaut Syndrome in patients two years and older. LGS is a rare and severe form of epilepsy that is typically diagnosed in childhood.

The FDA approval is based on two studies, including a Phase III trail in 238 patients with a current or prior diagnosis of LGS. The latter demonstrated that high doses of Onfi decreased weekly seizures by an average of 68% compared with a placebo.

Lundbeck head of R&D, Anders Gersel Pedersen, noted that Onfi "has in the largest clinical study ever conducted in LGS patients showed very solid clinical data which was further supported by several key secondary efficacy endpoints". He told Bloomberg that annual sales of the drug could reach 1 billion kroner (about $187 million).

The FDA, which has also granted Onfi a seven-year exclusivity period, noted that Onfi may slow thinking and impair motor skills "so it is important that people taking the drug not drive, operate heavy machinery, or engage in other dangerous activities until they know how the drug affects them".

The agency added that Onfi "can cause abuse and dependence" and it has been categorised as a Schedule IV drug under the Controlled Substances Act.