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Evaluating XEN1101 for Focal-Onset Seizures

A Randomized, Double-blind, Placebo-Controlled, Multicenter Phase 3 Study to Evaluate the Safety, Tolerability, and Efficacy of XEN1101 as Adjunctive Therapy in Focal-Onset Seizures

Phase 3 Interventional Xenon Pharmaceuticals Inc. · NCT05716100

This study is testing if a new medication called XEN1101 can help people with focal-onset seizures when added to their current seizure treatments.

Quick facts

PhasePhase 3
Study typeInterventional
Enrollment360 (estimated)
Ages18 Years and up
SexAll
SponsorXenon Pharmaceuticals Inc. Industry-sponsored
Locations94 sites (Little Rock, Arkansas and 93 other locations)
Trial IDNCT05716100 on ClinicalTrials.gov

What this trial studies

The X-TOLE3 Phase 3 clinical trial is a randomized, double-blind, placebo-controlled study designed to assess the efficacy, safety, and tolerability of XEN1101 as an adjunctive therapy for patients with focal-onset seizures. Approximately 360 participants will be randomly assigned to receive either XEN1101 at two different dosages or a placebo over a 12-week treatment period. Eligible participants must have a diagnosis of focal epilepsy and have been on stable doses of antiseizure medications prior to the study. The trial includes a baseline period to monitor seizure frequency and allows for an open-label extension for those who complete the initial treatment phase.

Who should consider this trial

Good fit: Ideal candidates are adults diagnosed with focal epilepsy who have not achieved sustained seizure freedom despite treatment with multiple antiseizure medications.

Not a fit: Patients with non-focal seizures or those who have not tolerated previous antiseizure medications may not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could significantly reduce the frequency of seizures in patients with focal-onset epilepsy.

How similar studies have performed: Previous studies have shown promise in using similar adjunctive therapies for epilepsy, indicating potential for success in this approach.

Eligibility criteria

Show full inclusion / exclusion criteria 
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.

Where this trial is running

Little Rock, Arkansas and 93 other locations

+44 more sites — see ClinicalTrials.gov for the full list.

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Focal Onset SeizuresEpilepsy
Last reviewed 2026-06-15 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.