Xenon to Highlight Phase 3 X-TOLE2 & Long-Term Data for Azetukalner in Focal Onset Seizures at 2026 AAN Annual Meeting

• Five abstracts accepted including Late-breaking Science oral and poster presentations of Phase 3 X-TOLE2 study results for azetukalner in focal onset seizures

• Poster presentations also include long-term efficacy and safety data from X-TOLE open-label extension study of azetukalner, as well as real-world data regarding the burden of titration and need for no-titration options in epilepsy

VANCOUVER, British Columbia and BOSTON, MA, April 07, 2026 (GLOBE NEWSWIRE) -- Xenon Pharmaceuticals Inc. (Nasdaq: XENE), a neuroscience-focused biopharmaceutical company dedicated to drug discovery, clinical development and commercialization of life-changing therapeutics for patients in need, today announced multiple presentations at the upcoming American Academy of Neurology (AAN) Annual Meeting, taking place April 18-22, 2026 in Chicago, Illinois. Five abstracts will be presented, including a Late-breaking Science oral and poster presentation of the topline Phase 3 X-TOLE2 study results for azetukalner in focal onset seizures (FOS), as well as a poster presentation of long-term 48-month azetukalner data from the X-TOLE open label extension study. The Company will also present real-world data highlighting unmet needs in epilepsy, including patient and clinician perspectives on the burden of antiseizure medication (ASM) titration and the impact of comorbidities in epilepsy, as well as data for its preclinical NaV1.1 program in Dravet syndrome.

• Oral & Poster Presentation #7:Resultsfrom the Phase 3 X-TOLE2 Study Evaluating Azetukalner, a Novel, Potent KV7 Channel Opener, in AdultswithFocal Onset Seizures (FOS)Session: LS1 – Late-breaking Science Session 1Date & Time: Sunday, April 19, 5:36-5:42 pm CT; Poster presentation to follow from 5:54 pm-6:15 pm CT

• Poster Presentation #10-001:Azetukalner, a Novel, Potent KV7 Channel Opener, in Adultswith Focal Epilepsy: ≥48-Month Interim Analysis of the Ongoing 7-Year X-TOLE Open-Label ExtensionSession: P11 – Poster Session 11Date & Time: Wednesday, April 22, 11:45-12:45 pm CT

• Poster Presentation #11-007:Treatment Experiences with Anti-seizure Medications (ASMs): Patient–Clinician Perspectives on Titration Burden, Quality of Life, and No-Titration OptionsSession: P3 – Poster Session 3Date & Time: Sunday, April 19, 5:00-6:00 pm CT

• Oral Presentation #002:Examining the Impact of Comorbid Depression on Healthcare Utilization, Cost, and Outcomes in Patients with Newly Diagnosed Epilepsy in the USSession: S41 – Epilepsy: Public Health and EpidemiologyDate & Time: Wednesday, April 22, 1:12-1:24 pm CT

• Oral Presentation #004:Selective Potentiation of NaV1.1 Channels by Small Molecule XPC-837 in Dravet Mice Suppresses Spontaneous Seizures, Prevents SUDEP, and Increases Long Term PotentiationSession: S19 – Emerging Therapies in Child NeurologyDate & Time: Monday, April 20, 4:06-4:18 pm CT

Exhibit HallXenon is hosting Booth #2330 in the AAN Exhibit Hall, which is scheduled to open at 11:30 am CT on Sunday, April 19 and close on Wednesday, April 22 at 4:00 pm CT. For more information about Xenon’s planned participation at AAN 2026, please visitthis link. Posters will be available after the live presentations.

About Xenon Pharmaceuticals Inc.Xenon Pharmaceuticals (Nasdaq: XENE) is a neuroscience-focused biopharmaceutical company dedicated to drug discovery, clinical development, and commercialization of life-changing therapeutics for patients in need. Xenon’s lead molecule, azetukalner, is a novel, potent, selective KV7 potassium channel opener in Phase 3 clinical trials for the treatment of epilepsy, major depressive disorder (MDD), and bipolar depression (BPD). Xenon is also advancing an early-stage portfolio of multiple promising potassium and sodium channel modulators, including KV7 and NaV1.7 programs in Phase 1 development for the potential treatment of pain. Xenon has offices in Vancouver, British Columbia, and Boston, Massachusetts. For more information, visitwww.xenon-pharma.comand follow us onLinkedInandX.

Xenon and the Xenon logo are registered trademarks or trademarks of Xenon Pharmaceuticals Inc. in the US, Canada, and elsewhere. All other trademarks belong to their respective owner.

Safe Harbor StatementThis press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, and the Private Securities Litigation Reform Act of 1995 and Canadian securities laws. These forward-looking statements are not based on historical fact, and include statements regarding the timing of and potential results from clinical studies; the potential efficacy, safety profile, future development plans in current and anticipated indications, addressable market, regulatory success, and commercial potential of our and our partners’ product candidates; the efficacy of our clinical study designs; our ability to successfully develop and achieve milestones in our azetukalner and other pipeline and development programs, including the anticipated filing of investigational new drug applications and NDAs; the timing and results of our interactions with regulators, including the timing of any NDA submission; our ability to successfully develop and obtain regulatory approval of azetukalner and our other product candidates; and anticipated timing of topline data readout from our clinical studies of azetukalner. These forward-looking statements are based on current assumptions that involve risks, uncertainties and other factors that may cause the actual results, events, or developments to be materially different from those expressed or implied by such forward-looking statements. These risks and uncertainties, many of which are beyond our control, include, but are not limited to: clinical studies may not demonstrate safety and efficacy of any of our or our collaborators’ product candidates; promising results from pre-clinical development activities or early clinical study results may not be replicated in later clinical studies; our assumptions regarding our planned expenditures and sufficiency of our cash to fund operations may be incorrect; our ongoing discovery and pre-clinical efforts may not yield additional product candidates; any of our or our collaborators’ product candidates, including azetukalner, may fail in development, may not receive required regulatory approvals, or may be delayed to a point where they are not commercially viable; we may not achieve additional milestones in our proprietary or partnered programs; regulatory agencies may impose additional requirements or delay the initiation or completion of clinical studies; the impact of market, industry, and regulatory conditions on clinical study enrollment; the impact of competition; the impact of expanded product development and clinical activities on operating expenses; the impact of new or changing laws and regulations; the impact of unstable economic conditions in the general domestic and global economic markets; adverse conditions from geopolitical events; as well as the other risks identified in our filings with the U.S. Securities and Exchange Commission and the securities commissions in British Columbia, Alberta, and Ontario. These forward-looking statements speak only as of the date hereof and we assume no obligation to update these forward-looking statements, and readers are cautioned not to place undue reliance on such forward-looking statements.

For Media:Colleen AlabisoSenior Vice President, Corporate Affairsmedia@xenon-pharma.com