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Ovation Pharmaceuticals has announced that an FDA advisory committee has voted unanimously to recommend Sabril (vigabatrin) for the treatment of two severe forms of epilepsy. If approved, Sabril will be the first FDA-approved monotherapy for infantile spasms. However, low historic uptake in the EU and concerns regarding visual field defects suggest that the drug's commercial prospects are limited.
The Peripheral and Central Nervous System Drugs Advisory Committee appointed by the FDA has voted unanimously to recommend Sabril (vigabatrin) as a monotherapy for infantile spasms, and an adjunctive treatment for adults with refractory complex partial seizures who have inadequately responded to several anticonvulsant drugs.
Sanofi-Aventis markets vigabatrin, a selective, irreversible enzyme-activated GABA transamine inhibitor, in many countries worldwide outside of the US for the treatment of partial seizures and infantile spasms. However, the drug has a long history with the FDA, which has previously denied it approval in the US. Therefore, the FDA advisory panel's recommendation to approve Sabril will be well received by Ovation, which acquired the North American rights to the drug in April 2004. In view of the recommendation, Datamonitor believes that regulatory approval of Sabril is highly likely and expects US launch to take place in Q1 2009.
According to key opinion leaders interviewed by Datamonitor, the development of effective treatments for the 20-30% of epilepsy patients who suffer from uncontrolled seizures (known as refractory epilepsy), as well as the development of greater treatment options for pediatric epilepsy, represent two key unmet needs. The anticipated approval of Sabril in complex partial seizures and infantile spasms will go some way to addressing these unmet needs. In addition, upon approval, Sabril would be the first and only drug approved in the US for the treatment of infantile spasms, thereby offering hope to patients suffering from this rare, yet serious condition.
Nevertheless, Sabril has experienced low uptake in the five major EU markets (France, Germany, Italy, Spain and the UK) and, as a result, Datamonitor does not expect the drug to achieve future sales comparable to those of key marketed brands. More importantly, Sabril has been reported to induce a permanent visual field defect in some patients, causing the FDA's advisory panel to recommend that the drug be available under a Risk Evaluation and Mitigation Strategy (REMS). Datamonitor believes that the serious nature of this side effect will further serve to limit uptake of Sabril in its approved indications in the US, while also inhibiting off-label prescribing of the drug in more prevalent epilepsy conditions. Therefore, Datamonitor forecasts Sabril to achieve epilepsy-specific sales of just $68m across the seven major markets by 2017.
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