Xenon Pharmaceuticals Inc. (Nasdaq: XENE) submitted a New Drug Application (NDA) to the U.S. Food and Drug Administration (FDA) for azetukalner as a treatment for focal seizures, the company announced Sept. 17, 2026.

The NDA is supported by data from two randomized, double-blind, placebo-controlled trials — the Phase 2b X-TOLE study and Phase 3 X-TOLE2 study — in which all four doses of azetukalner showed a statistically significant reduction in monthly seizure frequency compared with placebo. The epilepsy program has generated more than 1,500 patient-years of safety and exposure data. The ongoing Phase 3 X-TOLE3 and X-ACKT studies continue to enroll patients with focal seizures and primary generalized tonic-clonic seizures, respectively.

Separately, Xenon said it has voluntarily paused enrollment of new patients in its ongoing psychiatry clinical studies in major depressive disorder (MDD) and bipolar depression, following an analysis of neuropsychiatric adverse events. The company stated the observed events are consistent with the known safety profile of azetukalner, but had not previously been seen in the earlier Phase 2 X-NOVA MDD study. Patients already enrolled in those studies will continue participation. The pause does not affect epilepsy studies.

Enrollment in the X-NOVA2 MDD study reached approximately 360 patients, or about 80% of its initial target of 450, which the company said is sufficiently powered to detect a clinically meaningful change in the primary endpoint. Xenon plans to complete the six-week dosing period for currently enrolled patients and unblind the data, with topline results now expected in the first quarter of 2027.

Xenon said it is evaluating potential dosing modifications in psychiatry indications to address tolerability. The enrollment pause was implemented in consultation with the company's Data Safety Monitoring Board and is described as temporary.