A Randomized Study of XEN1101 Versus Placebo in Focal-Onset Seizures (X-TOLE3)

Inclusion Criteria: * Be properly informed of the nature and risks of the study and give informed consent in writing, prior to entering the study * Diagnosis (≥2 years) of focal epilepsy according to the International League Against Epilepsy (ILAE) Classification of Epilepsy (2017). Subject must have had adequate trials of at least 2 ASMs, which were given (and tolerated) at adequate therapeutic doses, without achieving sustained seizure freedom. * Treatment with a stable dose of 1 to 3 allowable current ASMs for at least one month prior to screening, during baseline, and throughout the duration of the DBP * Able to keep accurate seizure diaries Exclusion Criteria: * Previously documented electroencephalogram which shows any pattern not consistent with focal etiology of seizures. * History of focal aware non-motor seizures only, non-epileptic psychogenic seizure, primary generalized seizure, developmental and epileptic encephalopathy, including Lennox-Gastaut syndrome. * Seizures secondary to drug or alcohol use, ongoing infection, neoplasia, demyelinating disease, degenerative neurological disease, metabolic illness, progressive structural lesion, encephalopathy, or progressive central nervous system (CNS) disease. * History of status epilepticus or repetitive seizures within the 12-month period preceding Visit 1 where the individual seizures cannot be counted. * History of neurosurgery for seizures \<1 year prior to Visit 1, or radiosurgery \<2 years prior to enrollment. * Any medical condition or personal circumstance that, in the opinion of the investigator, exposes the subject to unacceptable risk by participating in the study or prevents adherence to the protocol.