An Open-label Extension Study Following a Double-blind, Randomized, Placebo-controlled, Multi-centre Study to Assess the Efficacy and Safety of Adjunctive Zonisamide in Pediatric Partial Onset Seizures

Those subjects who completed the double-blind study (E2090-E044-312) will be invited to participate in this extension study. The study consists of two main parts: Transition Period (double-blind) and Open Label Period. The study will start with the Transition Period during which subjects already on zonisamide will continue on the same dose of zonisamide and those who were taking placebo will be up-titrated to an appropriate dose of zonisamide. After all subjects have completed the Transition Period, the study will become open-label with every subject on the study receiving zonisamide. The study medication will be taken once daily in the evening. For those subjects previously in the placebo group, dosing with zonisamide will start with a dose of approximately 1 mg/kg. In order that the blind is maintained from the previous study, these subjects will initially continue taking the same number of placebo capsules as they were taking in the Maintenance Period of the E2090-E044-312 study until the up- titration is completed. Those subjects previously in the zonisamide arm will continue on the same dose which they received during the Maintenance Period of the E2090-E044-312 study. In order that the blind is maintained, they will also take placebo capsules in order to mirror the up- titration dose regimen of the subjects previously randomized to receive placebo in the E2090-E044-312 study. All subjects will stop taking placebo capsules after the Transition Period is complete. The duration of the Transition Period depends on the dose the subject appeared to have received when completing the core study E2090-E044-312. For those who completed on 8 mg/kg, the Transition Period will last 7 weeks. For those on 6 mg/kg, the Transition Period will last 5 weeks. However, during the double-blind Transition Period, some subjects may experience adverse events (AEs). If this should occur, the subject may be down titrated to one level above the minimal dose. The overall duration of the study will be up to 59 weeks. The overall duration of the Transition Period may thus be as short as 2 weeks or prolonged to as many as 11 weeks.

The Open Label Period will continue for up to a maximum of 59 weeks (approximately 15 months).

At the end of the study, Eisai will continue to supply zonisamide as part of this open-label extension protocol until the marketing authorisation of zonisamide for this indication or further development in this indication is stopped. In countries where no marketing authorisation will be applied for, Eisai has a compassionate use policy which can be applied for, if required.