Summary
Xenon Pharmaceuticals Inc. saw its stock rise 40% on Monday after announcing positive topline findings from its Phase 3 X-TOLE2 trial evaluating azetukalner in patients with focal onset seizures. The company reported that the trial met its primary endpoint in both dose groups and achieved its key secondary endpoint related to responder rates.
Primary and secondary outcomes
The X-TOLE2 study met the primary measure of median percent change from baseline in monthly focal onset seizure frequency. In the 25 mg dose group, the median percent change was -53.2% versus -10.4% for placebo, yielding a placebo-adjusted median percent change of -42.7% for the 25 mg cohort. That placebo-adjusted result exceeded the company’s earlier Phase 2b X-TOLE study, which showed a -34.6% placebo-adjusted median percent change for the 25 mg dose.
The trial also achieved its key secondary endpoint of Responder Rate 50. In the 25 mg group, 54.8% of participants experienced at least a 50% reduction in monthly focal onset seizure frequency from baseline. The 15 mg group posted a 37.6% responder rate, compared with 20.8% in the placebo arm.
Study population and completion
The randomized study enrolled 380 participants described as having highly treatment-resistant epilepsy. Patients had a median of five prior antiseizure medications and a baseline median seizure frequency of 12.75 per month. Of the 332 participants who completed the double-blind period, 322 went on to enter an open-label extension.
Safety profile
Azetukalner was generally well-tolerated in X-TOLE2, with a safety profile consistent with results reported in the earlier X-TOLE study. The most frequently reported treatment-emergent adverse events across both dose groups were dizziness, headache, somnolence, and fatigue.
Regulatory plans and market context
Xenon said it intends to submit a New Drug Application to the U.S. Food and Drug Administration for the treatment of focal onset seizures in the third quarter of 2026. If the FDA grants approval, azetukalner would be the only KV7 potassium channel opener available for epilepsy treatment.
Analyst comment
Stifel analysts noted that the strength of these results could prompt investors to reassess their assumptions about peak market penetration and peak sales for azetukalner.
Implications
The topline results provide data supporting Xenon’s regulatory timetable and underpin the company’s planned NDA submission. The reported efficacy and tolerability findings are central to the company’s clinical and commercial outlook for azetukalner in focal onset seizures.