Valparaiso

Researchers are investigating the safety, tolerability, and effectiveness of XEN1101 as an additional treatment for people with primary generalized tonic-clonic seizures (PGTCS) who have generalized epilepsy and are already taking 1 to 3 anti-seizure medications. This phase 3, multicenter, randomized, double-blind, placebo-controlled study includes participants aged 12 years and older and aims to better understand how XEN1101 affects seizure frequency compared to placebo. Participants will be randomly assigned to receive either XEN1101 or a placebo capsule once daily with their evening meal during a 12-week double-blind treatment period. Those aged 18 and older will take a 25 mg dose of XEN1101 or placebo, while those aged 12 to under 18 may receive 15 mg, 25 mg, or placebo. Before this period, participants will have up to 9.5 weeks to record their baseline seizure frequency. After completing the double-blind period, participants can join an open-label extension study for continued XEN1101 treatment or enter an 8-week follow-up phase if they do not enroll in the extension. During the study, participants will keep detailed seizure diaries and maintain stable doses of their anti-seizure medications. Researchers will monitor seizure frequency changes, safety, and tolerability throughout the treatment. The main measurement is the median percent change in monthly primary generalized tonic-clonic seizure frequency from baseline through the 12-week treatment. Safety follow-up and monitoring will continue during the post-treatment follow-up or open-label extension periods, with total participation lasting several months depending on extension enrollment.