A Randomized Study of XEN1101 Versus Placebo in Focal-Onset Seizures

Inclusion Criteria:

• Be properly informed of the nature and risks of the study and give informed consentin writing, prior to entering the study

• Diagnosis (≥2 years) of focal epilepsy according to the International League AgainstEpilepsy (ILAE) Classification of Epilepsy (2017). Subject must have had adequatetrials of at least 2 ASMs, which were given (and tolerated) at adequate therapeuticdoses, without achieving sustained seizure freedom.

• Treatment with a stable dose of 1 to 3 allowable current ASMs for at least one monthprior 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 consistentwith focal etiology of seizures.

• History of focal aware non-motor seizures only, non-epileptic psychogenic seizure,primary generalized seizure, developmental and epileptic encephalopathy, includingLennox-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 periodpreceding Visit 1 where the individual seizures cannot be counted.

• History of neurosurgery for seizures <1 year prior to Visit 1, or radiosurgery <2years prior to enrollment.

• Any medical condition or personal circumstance that, in the opinion of theinvestigator, exposes the subject to unacceptable risk by participating in the studyor prevents adherence to the protocol.