Study of Perampanel as Adjunctive Treatment for Inadequately Controlled Seizures Associated With Lennox-Gastaut Syndrome

This is a multicenter, double-blind, randomized, placebo-controlled, parallel-group study of perampanel as adjunctive therapy in participants with inadequately controlled seizures associated with LGS. The study will consist of 3 phases: Prerandomization (4 to 8 weeks), Randomization (18 weeks), and an Extension A (52 weeks). An additional Extension B with open-label treatment will be available for optional participation to participants who reside in Japan and in countries where an expanded access program (EAP) cannot be implemented or has not yet been implemented.