Xenon advances epilepsy drug filing, delays MDD readout to December
Xenon Pharmaceuticals reported third-quarter 2026 results alongside updates on its neuroscience pipeline. The company has submitted a U.S. application for azetukalner, its lead drug candidate, for focal seizures and is continuing late-stage studies in other epilepsy indications.
The update also included a revised timeline for a major depression trial, a pause on enrolling new patients in its Phase 3 depression studies, and plans to move two early-stage pain programs into Phase 2. Xenon said it had $1.2 billion in cash, cash equivalents and marketable securities at September 30, enough to fund operations into 2029.
Key details
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U.S. application submitted for focal seizures: Xenon submitted an application to the FDA for azetukalner in September. The company described the drug as a potassium-channel opener being developed for epilepsy and neuropsychiatric disorders. It cited efficacy and safety experience across more than 1,500 patient-years, while expressing confidence in the drug’s profile.
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More epilepsy studies are underway: The Phase 3 X-TOLE3 study in focal seizures continues to enroll and is intended to support regulatory applications outside the U.S. Enrollment outside Japan is expected to finish in 2026. The Phase 3 X-ACKT study is testing azetukalner in primary generalized tonic-clonic seizures, another potential epilepsy indication.
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A new study is planned for earlier use in focal seizures: Xenon plans to start the Phase 3b/4 X-FIRST study in the first quarter of 2027. The U.S. study will test azetukalner as a first add-on antiseizure medication for patients already taking either an SV2A modulator or a sodium-channel blocker. It is designed for patients who are less treatment-resistant and have lower baseline seizure frequency than participants in the X-TOLE studies. The open-label study will include 52 weeks of treatment.
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Major depression results expected in December: Enrollment is complete in the Phase 3 X-NOVA2 trial of azetukalner in major depressive disorder, with about 360 patients enrolled. Xenon now expects to report topline results in December 2026.
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New enrollment in depression studies is paused: Xenon said it voluntarily paused enrollment of new patients in its ongoing Phase 3 studies of azetukalner in major depressive disorder and bipolar depression in September. Patients already enrolled, including those in open-label extension studies, remain active.
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Pain candidates may move into Phase 2: Positive Phase 1 data for XEN1701, a NaV 1.7 program, and XEN1120, a KV 7 program, were presented at a pain congress. Xenon said the results support starting Phase 2 proof-of-concept studies in acute pain, which it plans to initiate in the first half of 2027.
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Further epilepsy data presentations are planned: Xenon presented six abstracts at the European Epilepsy Congress in September, including previously reported X-TOLE2 results and a presentation on azetukalner’s mechanism and potential use in combination with other treatments. The company expects to present additional azetukalner and epilepsy data at the American Epilepsy Society’s annual meeting in December.
Plain-English implications
Azetukalner is central to Xenon’s late-stage development program: the company is seeking U.S. approval for focal seizures while pursuing studies that could support additional epilepsy uses and a broader patient population. In parallel, the December MDD readout is a key near-term data milestone, even as new enrollment in the company’s depression studies remains paused. The cash position and stated runway into 2029 provide funding visibility for the planned clinical work.