Stiripentol for the treatment of Dravet syndrome

Catherine Chiron1–31INSERM U1129, Paris, France; 2Paris Descartes University, Paris, France; 3CEA, Gif-sur-Yvette, FranceAbstract: Stiripentol (marketed by Biocodex as Diacomit®) is an anticonvulsant drug, structurally unrelated to any other compound, which has recently been approved as adjunctive therapy with clobazam and valproate for Dravet syndrome in Europe, Canada, and Japan. This rare form of early childhood epilepsy is associated with subsequent cognitive impairment, significant risk of death, and high pharmacoresistance. Based on an efficacy signal of stiripentol added to clobazam and valproate in an observational, prospectively conducted, exploratory study including 10% of children with Dravet syndrome, a randomized placebo-controlled trial was specifically dedicated to patients with Dravet syndrome inadequately controlled by clobazam and valproate. Results showed significantly higher responder rates (71% versus 5%; P<0.0001) and decrease in seizure frequency (-69% versus +7%; P<0.002) on stiripentol than on placebo. A second, independently performed, randomized controlled trial confirmed these results 2 years later, and both trials were plotted in a meta-analysis. Efficacy was supported by three subsequent observational studies, with, respectively, 46 (France), 23 (Japan), and 82 (USA) children with Dravet syndrome treated with stiripentol for up to 5 years. Based on the experiences of more than 2,000 patients with Dravet syndrome who were exposed to stiripentol, drowsiness, loss of appetite, and weight loss are the most frequent adverse events and may be reduced by decreasing the dosage of co-medication. The inhibition of stiripentol by the cytochrome P450 complex (CYP2C19, and CYP3A4) leads to clinically significant interactions. Experimental data, both in vitro and in vivo, have definitively established that stiripentol is a GABAergic anticonvulsant and acts on different sites than benzodiazepines. The pharmacodynamic interactions also enhance the anticonvulsant effect of the stiripentol–clobazam combination in patients with Dravet syndrome, irrespective of the GABAergic effect. Stiripentol is currently the only drug specifically indicated in Dravet syndrome.Keywords: childhood epilepsy, antiepileptic drug trials, orphan drugs, clobazam, GABAergic drugs, CYP45