Perampanel as Adjunctive Therapy in Pediatrics With Partial Onset Seizures or Primary Generalized Tonic Clonic Seizures

This is a multicenter, open-label, single-arm study in children (age 4 to \<12 years) with inadequately controlled POS or PGTC seizures. The study will consist of a Core Phase and two Extension Phases (Extension Phase A \[for all countries in the study\], and Extension Phase B \[available for participants enrolled in Japan and in countries where an extended access program {EAP} cannot be implemented, after completion of Extension Phase A\]). The Core Phase will consist of the following 2 phases: Pretreatment and Treatment Phase. The Pretreatment Phase, during which participants will be assessed for eligibility, will consist of up to a 4-weeks +/- 3 days Screening/Baseline Period. The Treatment Phase will consist of 3 periods: Titration Period (up to an 11-weeks: dose titration on the basis of individual clinical response and tolerability), Maintenance Period (up to a 12-weeks: continuation of perampanel oral suspension once daily at the dose level achieved at the end of the Titration Period), and Follow-up Period (up to 4-weeks +/- 7 days: only for those participants not entering into Extension Phase A or those who prematurely discontinue from the study). Extension Phase A will consist of up to 29-weeks Maintenance Period and up to 4-weeks +/- 7 days Follow-up Period after the last dose of perampanel only for participants who did not enter into Extension Phase B. All participants who complete all scheduled visits up to and including Visit 9 in the Treatment Phase will be eligible to participate in Extension Phase A of the study. During the Maintenance Period of Extension Phase A, all participants will continue with their optimal perampanel dose (that is, dose level that they complete on during the Core Phase). After completing Extension Phase A, participants in Japan and in countries where EAP cannot be implemented, participants will be eligible to participate in Extension Phase B. In Japan, treatment will continue as long as clinically appropriate according to the judgment of the investigator. However, treatment of participants in Extension B will be completed when the participant reaches 12 years of age or when perampanel is commercially available in Japan for treatment of POS in pediatric participants (4 to less than 12 years of age). In countries where an EAP cannot be implemented, participation in Extension B will continue as long as clinically appropriate according to the judgment of the investigator, until the participants reaches 12 years of age or perampanel oral suspension is commercially available.