FDA mulls investigational epilepsy drug

January 27, 2009

The FDA is weighing approval of an investigational epilepsy drug for adults and children that has reportedly caused vision loss in certain patients.

In January, the Food & Drug Administration's advisory committee on neurology drugs was considering potential approval of an investigational epilepsy drug that has reportedly caused irreparable vision loss in certain patients.

Ovation Pharma, maker of vigabatrin (Sabril), is pursuing approval for the drug as an adjunctive therapy to treat refractory complex partial seizures in adults, and for monotherapy for infantile spasms in children.

Three studies have shown that the drug, in trials since the 1980s, has lowered seizures in adults and kids. But the US has raised concerns over a bilateral and concentric peripheral visual field defect linked to vigabatrin. In one study of 500 adults and children with refractory partial epilepsy, researchers found that vigabatrin was responsible for a peripheral visual field defect in 25% of adults, and 15% of children.

According to an FDA briefing document for the Peripheral and Central Nervous System Advisory Committee, the risk of acquiring the visual defect is related to dose, and repeated use of vigabatrin. Further, even after stopping the drug, patients are still at risk for the defect.

Yet, one of vigabatrin's plusses is that its mechanism of action increases the level of gamma-aminobutyric acid in the brain, and may provide a solution for patients who have not responded to other anti-epilepsy drugs, the FDA reports. No approved medications to treat infantile seizures are yet available on the US market.