A Phase 3 interventional study of XEN1101 and Placebo in Primary Generalized Tonic-Clonic Seizures, sponsored by Xenon Pharmaceuticals Inc.. Recruiting at 141 sites in 20 countries. Open to participants aged 12 Years and older. Per ClinicalTrials.gov, last updated 2026-11-02.
Sponsored by Xenon Pharmaceuticals Inc. · Phase 3, Interventional, and Treatment
This is a Phase 3, multicenter, randomized, double-blind, placebo-controlled study to evaluate the clinical efficacy, safety, and tolerability of XEN1101 administered as adjunctive treatment in primary generalized tonic-clonic seizures (PGTCS).
This is a Phase 3, multicenter, randomized, double-blind, placebo-controlled study to evaluate the clinical efficacy, safety, and tolerability of XEN1101 administered as adjunctive treatment in subjects diagnosed with generalized epilepsy and experiencing probable or possible PGTCS (with or without other subtypes of generalized seizures), and taking 1 to 3 anti-seizure medications (ASMs). Eligible subjects will be randomly assigned 1:1 to XEN1101 or placebo: subjects aged ≥ 18 years will receive XEN1101 25 mg or placebo, and subjects aged ≥12 years and \<18 years will receive either XEN1101 15 mg, 25 mg, or placebo. Randomization will be stratified based on region, age group, and background use of CYP3A4-inducer ASMs. Eligible subjects will have up to 9.5 weeks durations to assess the baseline frequency of seizures, followed by a double-blind treatment period (DBP) where subjects will receive 12 weeks of blinded treatment. During the DBP, subjects will be instructed to orally take XEN1101 or placebo once daily with an evening meal.
Subjects who complete the 12-week DBP will have the opportunity to enroll in a separate open-label-extension (OLE) study for continued treatment with XEN1101. Subjects who do not enroll in the OLE will enter an 8-week post-treatment follow-up period.
1,848 studies on the registry are indexed under Epilepsy; 422 are open to participants now.
This study's planned enrollment of 160 is above the median of 50 across 1,239 interventional studies indexed under Epilepsy.
Browse Epilepsy studies →Xenon Pharmaceuticals Inc. is the lead sponsor of 23 studies on the registry; 3 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Key Inclusion Criteria:
Key Exclusion Criteria:
Subject has any laboratory abnormalities or clinically significant abnormalities on prestudy physical examination, vital signs, or that, in the judgment of the investigator, indicate a medical problem that would preclude study participation, including but not limited to:
a. History or presence of long syndrome; QTcF >450 msec at baseline; family history of sudden death of unknown cause.
The criteria to be eligible for randomization are:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
A recording of the heart’s electrical activity, taken with stickers on the chest, arms and legs. It takes a few minutes and does not hurt.
On an ECG, the QT interval is the time the heart’s lower chambers take to activate electrically and recover in each beat. QTc is that time adjusted for heart rate (QTcF by Fridericia’s formula, QTcB by Bazett’s). Some medicines lengthen it, and a long QTc can raise the risk of a dangerous heart rhythm.
The study may name a correction formula and a limit in milliseconds, often around 450–480.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECG (electrocardiogram)
A recording of the heart’s electrical activity, taken with stickers on the chest, arms and legs. It takes a few minutes and does not hurt.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
QT and QTc
On an ECG, the QT interval is the time the heart’s lower chambers take to activate electrically and recover in each beat. QTc is that time adjusted for heart rate (QTcF by Fridericia’s formula, QTcB by Bazett’s). Some medicines lengthen it, and a long QTc can raise the risk of a dangerous heart rhythm.
The study may name a correction formula and a limit in milliseconds, often around 450–480.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
XEN1101 25 mg/day
Drug: XEN1101
XEN1101 15 mg/day
Drug: XEN1101
Placebo
Drug: Placebo
XEN1101 capsules
Also known as: Azetukalner
Placebo capsules
Median percent change (MPC) in monthly (28 days) PGTCS frequency
Median percent change (MPC) in monthly (28 days) PGTCS frequency from baseline through the DBP for XEN1101 versus placebo.
Time frame: Baseline through DBP (Week 12)
Proportion of subjects
Proportion of subjects experiencing ≥50% reduction in monthly (28 days) PGTCS frequency from baseline through the DBP for XEN1101 versus placebo.
Time frame: Baseline through DBP (Week 12)
Proportion of subjects
Proportion of subjects experiencing PGTCS freedom from baseline through the DBP for XEN1101 versus placebo.
Time frame: Baseline through Week 12
Incidence of adverse events
To assess the safety and tolerability of XEN1101 in subjects with PGTCS (e.g., adverse events).
Time frame: From Screening Through to 56 Days Post-Final Dose
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From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drug tested here: XEN1101