This is an Open Label Extension study of the following Phase 3 clinical studies: XPF-010-301 (X-TOLE2), XPF-010-302 (X-TOLE3), and XPF-010-303 (X-ACKT). This study will evaluate the long term safety, tolerability, PK, and efficacy of XEN1101 25 mg QD taken orally once daily (QD) in subjects with FOS or PGTCS for the treatment of seizures for up to 3 years. Subjects who successfully completed and did not terminate early from one of the antecedent studies (X-TOLE2, X-TOLE3, or X-ACKT) are eligible to participate in X-TOLE4.~Following enrollment into X-TOLE4, subjects will undergo a treatment period of up to 3 years, during which there will be a visit at 2-, 4-, and 13-weeks post-entry, with subsequent visits occurring at 13 week intervals during the first year, and then at 26-week intervals (with a telephone call in between) until dosing is completed. All subjects will be initially assigned to receive 25 mg QD of XEN1101. Subjects will be instructed to orally take XEN1101 once daily with an evening meal. Subjects will be expected to keep a daily seizure eDiary with a minimum of 80% compliance for the duration of the extension study (reporting on ≥80% of days between visits).~Upon completion of dosing at the end of the treatment period, there will be an 8-week follow up period.
This study will evaluate the long term safety, tolerability, PK, and efficacy of XEN1101 25 mg QD taken orally in subjects with Focal Onset Seizures (FOS) or Primary Generalized Tonic-Clonic Seizures (PGTCS) for the treatment of seizures for up to 3 years.