UK drug giant GlaxoSmithKline and development partner Valeant Pharmaceuticals have scored a big win on the approval of their epilepsy drug Trobalt in Europe, marking its first license worldwide.

The European Commission has granted marketing authorisation for the use of Trobalt (retigabine) as an add-on therapy for partial onset seizures with or without secondary generalisation in adult patients with epilepsy.

The approval was widely expected given that the European Medicines Agency's Committee for Medicinal Products for Human Use backed the drug's use in this setting back in January, sparking hopes that patients would be given access to a new option to help control their disease.

Around one-third of patients with epilepsy continue to experience seizures despite treatment, underscoring the need for new effective treatment options to help better manage the condition and highlighting Trobalt's potential to take advantage of this unmet need.

European approval came on the back of results from two pivotal Phase III studies (RESTORE 1 and 2) as well as a Phase IIb study (205) showing that more patients with partial onset seizures saw a reduction of 50% or more in seizure frequency compared to placebo, when 600mg, 900mg or 1200mg doses of Troblat were added to existing anti-epileptic drug therapy. 

Safety precautions

On a cautionary note, however, observations in clinical trials have led regulators to include recommendations in the prescribing information that Trobalt is used with caution in patients at risk of urinary retention.

In addition, because of potential interference with the heart's electrical activity, it recommends that ECGs are carried out in patients taking any medication that may interfere with this, in those who may have congestive heart failure, ventricular hypertrophy, hypokalaemia or hypomagnesaemia, and in those aged 65 years and above.

Trobalt has received a preliminary approval from Swissmedic, the Swiss Agency for Therapeutic Products, in December last year, but the drug's application in the US, where it is known as Potiga (ezogabine), has temporarily stalled following a complete response letter from the Food and Drug Administration on non-clinical grounds.

Analysts have forecast peak sales for the drug - the first potassium channel opener in development for epilepsy - in the range of $200-$800 million.