Randomized, Double-Blind Study to Evaluate Efficacy and Safety of Cenobamate Adjunctive Therapy in PGTC Seizures

This randomized, double-blind, placebo controlled trial is designed to evaluate safety, efficacy, and pharmacokinetics of cenobamate adjunctive therapy as compared to placebo on PGTC seizures in subject with idiopathic generalized epilepsy. Subjects will be randomized to receive either cenobamate or placebo on a 1:1 basis. The study will have three periods, pre-randomization period where a baseline seizure frequency is established, treatment period and follow up period. The treatment period consists of a 10 week titration phase where subjects are titrated slowly until they reach the target dose and a maintenance phase. During the titration phase, subjects will receive 12.5 mg study drug, followed by 25 mg, 50 mg, 100 mg, and 150 mg study drug every two weeks. During the maintenance phase, subjects will receive the target dose of 200 mg study drug or adolescent equivalent. Subjects will take their once daily dose of study drug at approximately the same in the morning with or without food. If tolerability issues arise, subjects can switch to evening dosing. There is also an option to down-titrate to 150 mg study drug, one time only. If tolerability issues continue, subjects may be discontinued. Upon completion of the maintenance phase, eligible subjects will have an opportunity to enroll in an open-label safety study. Subjects who discontinue early or do not wish to participate in this additional study will complete the three week follow up period. Subjects may receive a one week down titration to 100 mg and return for a follow up visit 2 weeks later. Adolescents will follow the same every two week regimen and receive cenobamate as an oral suspension based on weight Throughout the study, subjects will keep a diary containing the type and frequency of seizures. This will be the primary efficacy measure.