New epilepsy drug filed for approval

2 November 2009

GlaxoSmithKline and Valeant Pharmaceuticals have submitted a marketing authorisation application to the European Medicines Agency for their epilepsy treatment, retigabine.

Retigabine is thought to cause a hyperpolarising shift in the neuronal potassium current and thereby reduce the excitability of neuronal cells.

The companies are seeking approval for retigabine as an adjunctive treatment in adults with refractory partial-onset seizures. If approved, the drug would be the first in a new class of neuronal potassium channel openers.

Retigabine has been evaluated in two randomised, double-blind, placebo-controlled Phase III trials in patients receiving up to three antiepileptic medications. The drug met its primary efficacy end points at all doses tested.

RESTORE 1 enrolled 306 patients to receive either retigabine 1200mg daily in three divided doses, or placebo. The study lasted for a total of 32 weeks and a response to treatment was defined as a reduction of at least 50% in 28-day total partial seizure frequency during the maintenance phase.

In the intention to treat analysis, the rate of response in the retigabine group (55.5%) was more than twice as high as that in the placebo group (22.6%).

RESTORE 2 tested 600mg and 900mg divided daily doses of retigabine in a total of 539 patients over 30 weeks. As in RESTORE 1, the proportion of patients who achieved a response was significantly greater in the retigabine groups than in the placebo group.

The adverse effects most commonly associated with retigabine in the RESTORE trials included dizziness, somnolence, fatigue, confusion, slurring of speech, ataxia, blurred vision, tremor, and nausea.