Azetukalner

Focal seizures are more common than generalized seizures, with a median focal seizure incidence rate of 30.4 per 100,000 per year compared with 19.6 per 100,000 per year for generalized seizures, and focal epilepsy comprises about 55.7% to 61.1% of the overall epilepsy population. In 2021, 1.1% of US adults, approximately 2,865,000 people, reported active epilepsy. Approximately 40% of people with epilepsy are drug resistant, and among US adults using antiseizure medications for focal epilepsy, 66.4% had persistent seizures of more than one per year. Mortality is elevated: the weighted median standardized mortality ratio was 2.3 across population-based incidence cohorts, sudden unexpected death in epilepsy occurs at 1.2 per 1,000 patient-years in adults and at up to 6.3 per 1,000 people in drug-resistant focal epilepsy, and the suicide-specific standardized mortality ratio is 3.3. Quality of life tracks with seizure control: the mean QOLIE-31-P total score was 56.4 in drug-resistant focal epilepsy compared with 70.8 in drug-responsive focal epilepsy. US spending attributable to epilepsy or seizure was $6,853 per person per year above matched controls, an aggregate of $24.5 billion, and adjusted total direct costs rose from $18,600 per year at less than one seizure per year to $43,708 per year at one or more seizures per week.

Two randomized, double-blind, placebo-controlled trials support the New Drug Application. In the Phase 2b X-TOLE trial, 325 participants were randomized and treated and 323 were analyzed for efficacy. The median percent reduction in monthly focal onset seizure frequency over the 8-week double-blind period was 52.8% at 25 mg, 46.4% at 20 mg, and 33.2% at 10 mg, compared with 18.2% for placebo. The proportions of participants with at least a 50% reduction were 54.5%, 43.1%, and 28.3%, compared with 14.9% for placebo. In the Phase 3 X-TOLE2 trial, 380 participants were randomized and 374 were analyzed. The median percent change was -53.2% at 25 mg and -34.5% at 15 mg, compared with -10.4% for placebo, and the proportions with at least a 50% reduction were 54.8% and 37.6%, compared with 20.8% for placebo. The placebo-adjusted median percent change in the X-TOLE2 25 mg group was -42.7%.

In the X-TOLE open-label extension, among participants treated for at least 48 months (n = 131) the median percent reduction in monthly focal onset seizure frequency rose from 69.8% in the first month to 90.9% at month 48, and seizure freedom for any consecutive period of at least 12 months was attained by 38.2% of that group. The most common treatment-emergent adverse events in X-TOLE2 across both azetukalner doses were dizziness (20.5%), headache (8.8%), somnolence (8.8%), and fatigue (7.6%), compared with 3.2%, 6.4%, 7.2%, and 6.4% for placebo. Discontinuation for a treatment-emergent adverse event occurred in 14.5% of the 25 mg group, 4.8% of the 15 mg group, and 3.2% of the placebo group. No retinal pigment epithelium or macular abnormalities occurred during the X-TOLE2 double-blind period, and the epilepsy trials have generated more than 1,500 patient-years of safety and exposure data.

No price has been announced for azetukalner, and no budget impact model, cost-effectiveness analysis, or health technology assessment of the product has been published. Xenon Pharmaceuticals reports no products approved for sale and no revenue from product sales. One published forecast, produced by GlobalData and reported by Pharmaceutical Technology in 2024, projects US revenue of $651 million a year by 2035; that forecast predates the Phase 3 X-TOLE2 readout.

Cost benchmarks therefore come from recently launched branded adjunctive antiseizure medications for focal epilepsy. In the US National Average Drug Acquisition Cost file for the week of 16 September 2026, the acquisition cost per tablet was $39.86819 for cenobamate 200 mg, $24.07624 for brivaracetam 100 mg, and $39.07764 for perampanel 12 mg. Across the 2013 to 2023 National Average Drug Acquisition Cost series, the average price of brand-name antiseizure medications rose from $8.71 to $15.43 per unit while generic prices fell from $1.39 to $1.26, widening the brand-to-generic price gap from 1452.39% to 3399.26%. National Average Drug Acquisition Cost is a pharmacy acquisition benchmark, not a wholesale acquisition cost.

Where adjunctive antiseizure medications have been modeled, the modeled budget effect has been favorable, although all such models are non-US. A Belgian budget impact model estimated that introducing cenobamate would reduce the national payer budget by 8,105,616 euros over three years, because reduced seizure-related medical costs offset the drug cost. A budget impact analysis submitted to the Canadian reimbursement review estimated a three-year budget impact of 1,773,123 Canadian dollars in savings. Cost-effectiveness analyses in the United Kingdom, the Netherlands, and Italy each found cenobamate to yield more quality-adjusted life years at lower total cost than brivaracetam, eslicarbazepine acetate, lacosamide, and perampanel.

Azetukalner is an investigational once-daily oral KV7.2 and KV7.3 potassium channel opener. A New Drug Application for focal seizures was submitted to the US Food and Drug Administration on 17 September 2026, based on the Phase 2b X-TOLE trial and the Phase 3 X-TOLE2 trial. No filing acceptance, review designation, or action date has been announced, and no US launch date has been stated.

Both randomized trials met their primary endpoint of median percent change in monthly focal onset seizure frequency, in populations that had failed a median of five to six prior antiseizure medications and, in X-TOLE2, included approximately 40% of participants taking concomitant cenobamate. If approved, azetukalner would be the only KV7 potassium channel opener available for epilepsy, since ezogabine, the first agent of this class, was withdrawn from the US market in 2017 and its European marketing authorisation was withdrawn in 2018. The reported safety experience across more than 1,500 patient-years does not show the retinal and skin pigmentary changes that limited ezogabine, although pigmentary changes with that predecessor were generally reported after two or more years of treatment. Urinary retention, reported in 1.1% of open-label extension participants, is described as a possible class effect of KV7 channel openers.

Limits on the evidence should be weighed. As of September 2026 no peer-reviewed publication and no registry results record exist for X-TOLE2, so confidence intervals, the statistical testing hierarchy, and full adverse event tables are not publicly available. Both double-blind periods were short, 8 weeks in X-TOLE and 12 weeks in X-TOLE2, and long-term seizure outcomes come from an uncontrolled open-label extension in which retention was 60% at 24 months. Seizure freedom during the randomized period was uncommon, at 6.5% for 25 mg compared with 0.8% for placebo in X-TOLE2. Enrollment was restricted to adults with at least two prior failed antiseizure medications who were taking one to three concomitant medications, so the evidence does not address monotherapy, pediatric use, or newly diagnosed epilepsy. In September 2026 Xenon paused enrollment of new participants in its major depressive disorder and bipolar depression trials after an analysis of neuropsychiatric adverse events; the company states this action does not affect the epilepsy trials, but the finding is relevant to assessment of the neuropsychiatric profile of the molecule.