Xenon Pharmaceuticals (XENE) filed its first new drug application with the FDA for azetukalner to treat focal-onset seizures and simultaneously paused its psychiatry pipeline after safety signals emerged in late-stage trials, the company told attendees at the TD Cowen 6th Annual Novel Mechanisms in Neuropsychiatry Summit on Wednesday.
The NDA, filed in September, covers four dose strengths of azetukalner — 10 mg, 15 mg, 20 mg and 25 mg — and is supported by two Phase III randomized placebo-controlled trials, X-TOLE and X-TOLE2. The second study, X-TOLE2, concluded in March 2026. Management expects a standard 12-month FDA review period, followed by a separate three-month DEA scheduling process once the drug is approved. Dosing would be once daily with no required titration and minimal drug-drug interaction risk, Xenon said. The 15 mg strength is expected to be the likely starting dose in clinical practice.
CEO Ian Mortimer described the X-TOLE2 results as showing "incredibly robust separation" between the 25 mg dose and placebo, calling it potentially the best placebo-adjusted efficacy ever demonstrated in a focal-onset seizure trial. He added that all four filed dose strengths proved efficacious regardless of starting point.
The epilepsy program has accumulated approximately 1,500 patient-years of exposure, including patients on treatment for more than five years continuously. Data from the open-label extension of X-TOLE covering 60 months of follow-up is expected to be presented at the American Epilepsy Society meeting in December 2026.
In contrast, Xenon announced a pause on its major depressive disorder and bipolar depression programs after neuropsychiatric adverse events surfaced in Phase III trials. Events included confusion, concentration difficulties, aphasia, word-finding problems, dizziness and somnolence, exhibiting a dose- and exposure-related pattern. The X-NOVA2 study was more than 80% enrolled at the time of the pause. Phase II proof-of-concept data from X-NOVA, which enrolled just over 50 subjects per arm, will provide earlier signals, with unblinded efficacy results expected in Q1 2027. A separate bipolar depression study, X-CEED, is also part of the paused portfolio.
Mortimer characterized the adverse events as consistent with prior knowledge of the mechanism rather than novel safety concerns, noting the data remain blinded in psychiatry.
The company's pain franchise, featuring Nav1.7 inhibitor XEN1701 and KV7 modulator XEN1120, is advancing toward Phase II proof-of-concept studies in acute post-surgical pain models — bunionectomy and abdominoplasty — expected to begin in 2027. A third Nav1.7 molecule recently entered Phase I. Three molecules have entered Phase I over the past 15 months.
Shares of Xenon traded at $36.49, near its 52-week low of $35.97, having declined 31% over the past week following the psychiatry pause announcement. Wall Street price targets range from $46 to $100. The company's market capitalization stands at $3.53 billion, with a current ratio of 21.02. Revenue growth is forecast at 100% for fiscal 2026. Azetukalner would represent the first novel-mechanism approval for focal-onset seizures since 2019.
