Xenon Pharmaceuticals Highlights Strong Phase III Azetukalner Data, Q3 NDA Plans at Bloom Burton Conference

Key Points

• Phase III success: Xenon’s X-TOLE2 trial met its primary endpoint for focal onset seizures, with the 25 mg dose delivering a 43% placebo‑adjusted effect (53.2% vs 10.4%), showing a clear dose‑response and rapid separation from placebo; the company plans a Q3 NDA filing and expects a pre‑NDA meeting soon.
• Durability and commercial outlook: Open‑label data show seizure reduction deepening to nearly 90% at four years and about 40% of long‑term patients achieving 12+ months seizure freedom, and Xenon estimates an addressable U.S. patient population of up to ~1 million while building a commercial team.
• Pipeline expansion: Xenon is pursuing a Phase III psychiatry program for azetukalner (first readout expected H1 2027) and advancing two pain candidates from Phase I toward Phase II acute pain studies this year.

Xenon Pharmaceuticals NASDAQ: XENE provided an update on its clinical and pipeline progress at the Bloom Burton conference, with CEO Ian Mortimer highlighting recent Phase III results for lead program azetukalner, plans for regulatory filings, and continued expansion into psychiatry and pain.

Lead program focuses on epilepsy with recent Phase III data

Mortimer described Xenon as a CNS-focused company with deep expertise in drugs and ion channels, emphasizing azetukalner, a Kv7 potassium channel modulator. He said the drug’s attributes include once-daily, single-pill dosing, no titration, and “no meaningful drug-drug interactions,” which he positioned as beneficial for patients on polypharmacy.

In epilepsy, Mortimer said Xenon reported “really strong Phase III data” in focal onset seizures in early March from its X-TOLE2 study. The randomized, placebo-controlled trial included two active doses (15 mg and 25 mg) during a 12-week double-blind period and enrolled slightly more than the targeted ~360 participants across three arms, according to Mortimer.

Mortimer said the study met its primary endpoint, based on median percent change (MPC) in monthly seizure burden from baseline. He highlighted a dose-response relationship, describing efficacy as increasing “almost in a linear fashion” from placebo to 15 mg and 25 mg. He also emphasized rapid onset, saying the 25 mg dose achieved a statistically significant separation from placebo at week one because patients start at a therapeutic dose on day one.

Efficacy and long-term data highlighted

Mortimer pointed to the 25 mg arm’s placebo-adjusted MPC as a key result, describing it as a 43% placebo-adjusted effect (53.2% for 25 mg versus 10.4% for placebo). He called the result “the best efficacy ever seen in a focal onset seizure study in the most severe patient population ever trialed,” while noting his comparison was based on cross-trial benchmarking against labeled studies for other branded epilepsy drugs.

He also discussed long-term open-label extension data presented at the American Epilepsy Society meeting in December, referencing four-year follow-up from Xenon’s Phase II program. According to Mortimer, patients who completed blinded studies have shown a high rollover rate into open-label extension—about 97%—allowing the company to track longer-term outcomes.

Mortimer said seizure reduction deepened over time, with the population approaching a “close to a 90% reduction” in seizure burden at four years, compared with roughly 50% during the double-blind period. He added that a subset of less severe patients—those on one or two background medications instead of three—showed a “100% reduction” in seizure burden in the open-label dataset.

He also highlighted seizure freedom metrics, saying that among patients on therapy for more than four years, “about two in five, or almost 40%,” achieved 12 months or more of seizure freedom. Mortimer framed 12-month seizure freedom as a meaningful milestone because it can enable patients to drive again in many jurisdictions.

Safety profile and regulatory timeline

On safety, Mortimer said azetukalner’s adverse event profile has been consistent over time and aligns with expectations for a CNS-active drug aimed at dampening hyperexcitability. He cited common adverse events including dizziness, somnolence, fatigue, and headache, and said serious adverse events were “very few” and “reasonably well balanced across the treatment groups.” He added that some patients have been treated for more than five years.

Mortimer said Xenon plans to file a New Drug Application for focal onset seizures in the third quarter of this year. In the Q&A, he said the company previously conducted an end-of-Phase II meeting with the FDA after its Phase IIb X-TOLE study, and that the agency “signed off on the Phase III program” and protocols. He added that Xenon expects to hold a pre-NDA meeting “in the coming months” as the next regulatory interaction ahead of the planned submission.

Broader epilepsy work and commercial preparations

Beyond focal onset seizures, Mortimer said Xenon is running an ongoing Phase III trial in primary generalized tonic-clonic seizures, the most common form of generalized epilepsy, which he described using the older term “grand mal.” He said the company hopes to read out that study “in the coming years.”

Asked about commercial opportunity and pricing, Mortimer acknowledged epilepsy is a “highly genericized market” with more than 20 available drugs, but said up to 50% of patients still need better seizure control. Focusing on the U.S., he estimated that after accounting for focal epilepsy patients with breakthrough seizures—including adolescent and pediatric patients—the addressable group could be “upwards of 1 million patients” needing improved control.

Mortimer also discussed reimbursement dynamics, saying epilepsy is a protected class under Medicare, supporting coverage through commercial and government programs. He said Xenon is building its commercial infrastructure and currently has “about 15 people,” with key leadership roles filled, including a Chief Commercial Officer, and that the commercial team has epilepsy experience.

Psychiatry Phase III program and early-stage pain assets

Mortimer said Xenon believes azetukalner may have antidepressant effects and is conducting a Phase III psychiatry program, with the first Phase III readout expected in the first half of 2027. He summarized prior Phase II proof-of-concept results from the X-NOVA study in major depressive disorder, which evaluated 10 mg and 20 mg versus placebo.

According to Mortimer, the study showed separation from placebo and a dose response on depression scales, including a three-point separation on the MADRS scale that narrowly missed statistical significance due to sample size and variability. He said a three-point separation on the HAMD17 scale achieved a nominal p-value below 0.05, and Xenon selected HAMD17 as the primary endpoint for Phase III. He also highlighted a signal on anhedonia measured by the SHAPS scale, also with a nominal p-value below 0.05, which he said will be a key secondary endpoint in Phase III.

Mortimer said the Phase III psychiatry program includes:

• X-NOVA2 and X-NOVA3 in major depressive disorder
• A Phase III trial in bipolar depression using 20 mg of azetukalner, initiated toward the end of last year

He added that tolerability in psychiatric patients appeared better than in epilepsy patients in cross-trial comparisons, potentially because psychiatry trials are run as monotherapy while epilepsy patients often take multiple background medications.

Finally, Mortimer outlined early-stage development work in pain. He said Xenon advanced two new molecules into Phase I healthy volunteer studies last year and expects both to move into Phase II proof-of-concept acute pain studies later this year. He highlighted a Nav1.7 program, calling it a “remarkable” but historically challenging target, and said Xenon has already reached doses and exposures in Phase I where it is seeing receptor occupancy levels consistent with what would be needed to mimic human genetics. He also referenced a Kv7 program, XEN1120, on a similar development timeline.

Mortimer concluded that Xenon aims to build a “fully integrated neurology company,” with expectations for its first commercial launch in the next few years, anchored by azetukalner’s epilepsy program and supported by expansion into psychiatry and pain.

About Xenon Pharmaceuticals NASDAQ: XENE

Xenon Pharmaceuticals Inc is a clinical‐stage biopharmaceutical company dedicated to discovering and developing novel, small‐molecule drugs targeting ion channels in the central and peripheral nervous system. The company's research focus centers on neurological and pain disorders—including epilepsy, migraine, and neuropathic pain—by modulating key ion‐channel proteins to restore normal neuronal function. Xenon's scientific platform draws upon advances in ion‐channel biology and structure‐based drug design to identify and optimize therapeutic candidates with the potential for improved safety and efficacy profiles compared with existing treatments.

The company's pipeline comprises multiple preclinical and clinical programs.

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