Xenon Pharmaceuticals Provides Updates on Partnered Neurology Pipeline Programs at the 2019 American Epilepsy Society (AES) Annual Meeting

Overview of Clinical Stage XEN901 and Related Patient Survey to be Presented in the "Genetic Epilepsies ? Updates in the Science and Diagnosis" Exhibit in Room 318-319 on Sunday, December 8^th

Pre-Clinical Work Suggests Selective Sodium Channel Inhibitors that Reduce Action Potential Firing in Excitatory Neurons, While Sparing Inhibitory Interneurons, May Provide Promising Drug Profile

BURNABY, British Columbia, Dec. 07, 2019 (GLOBE NEWSWIRE) -- Xenon Pharmaceuticals Inc. (Nasdaq:XENE), a clinical stage biopharmaceutical company, announced today that it will provide updates on its partnered epilepsy programs at the American Epilepsy Society (AES) Annual Meeting held in Baltimore, MD.

Dr. Simon Pimstone, Xenon's Chief Executive Officer, said, "There are a number of presentations at the AES meeting related to our recently announced license and collaboration with Neurocrine Biosciences. Our presentations provide details on the clinical stage XEN901 epilepsy program and other pre-clinical licensed Nav1.6 and dual Nav1.2/1.6 programs. In addition to the scientific poster sessions at AES, we will be presenting information on both our partnered and proprietary programs at the BioMarin scientific exhibit on Sunday."

On December 2, 2019, Xenon announced a license and collaboration agreement with Neurocrine Biosciences, Inc. (Nasdaq:NBIX) to develop first-in-class treatments for epilepsy. Neurocrine Biosciences has an exclusive license to XEN901, a clinical stage selective Nav1.6 sodium channel inhibitor with potential in SCN8A developmental and epileptic encephalopathy (SCN8A-DEE) and other forms of epilepsy, including focal epilepsy. In addition, Neurocrine Biosciences gained an exclusive license to pre-clinical compounds for development, including selective Nav1.6 inhibitors and dual Nav1.2/1.6 inhibitors. The agreement also included a multi-year research collaboration to discover, identify and develop additional novel Nav1.6 and Nav1.2/1.6 inhibitors.

The presentations related to XEN901 and earlier stage selective Nav1.6 inhibitors and dual Nav1.2/1.6 inhibitor partnered programs at the AES meeting include:

• XEN901: A poster presentation entitled, "A Phase 1 Study in Healthy Subjects to Assess the Safety, Tolerability and Pharmacokinetics of XEN901, a Novel, Selective Nav1.6 Sodium Channel Inhibitor for the Treatment of SCN8A-Related Epilepsy" will be presented as Poster #15 in the BioMarin exhibit. A Phase 1 clinical trial was completed using a powder-in-capsule formulation of XEN901 in healthy adult subjects. Xenon developed a pediatric-specific, granule formulation of XEN901, and juvenile toxicology studies to support pediatric development activities have recently been completed. Neurocrine Biosciences anticipates filing an IND application with the FDA in the middle of 2020 in order to start a proposed clinical trial for XEN901 in SCN8A-DEE patients. Additionally, the results from an online survey of caregivers will be presented in Poster #18, entitled "An Online Survey of Caregivers of Patients with SCN8A Related Epilepsy." The survey results help to improve the knowledge of disease course and phenotypic heterogeneity, as well as inform clinical trial design for later stages of development.
  
  
• Nav1.6 and Dual Nav1.2/1.6 Inhibitors: In a poster entitled, "XEN393, A Novel Selective Dual Inhibitor of Nav1.2/Nav1.6 Channels Prevents Electrically-Induced Seizures in Mice and Rats," data are presented that show dual Nav1.2/1.6 inhibitors may provide a novel, mechanistically differentiated profile distinct from all marketed non isoform selective sodium channel blockers. Because of the dynamic nature of sodium channel expression during development, a number of childhood genetic epilepsies that could benefit from a dual Nav1.2/1.6 inhibitor. In a poster entitled, "Nav1.6 Selective and Nav1.2/Nav1.6 Dual Inhibitors Reduce Action Potential Firing in Mouse Cortical Pyramidal Neurons While Sparing Inhibitory Interneuron Firing," pre-clinical data is presented to support the hypothesis that selective Nav1.6 and Nav1.2/1.6 inhibitors that reduce action potential firing in excitatory neurons, while sparing inhibitory interneurons, could provide a better pharmacologic profile for new anti-seizure medicines. A compilation of this pre-clinical work ? showing that novel small molecule modulators of brain voltage gated sodium channels have the potential to drive new personalized therapies for patients with both gain- and loss-of-function mutations ? will be presented in the BioMarin exhibit as Poster #14 entitled "Selective Sodium Channel Inhibitors and Potentiators; Pharmacology in Cortical Slices from Wild Type and Dravet Mice."

About the BioMarin Scientific Exhibit: "Genetic Epilepsies ? Updates in the Science and Diagnosis"
Xenon, in collaboration with Invitae and Stoke Therapeutics, is participating in the BioMarin Scientific Exhibit entitled "Genetic Epilepsies ? Updates in the Science and Diagnosis" on Sunday, December 8, 2019 from 8:00 am ET to 5:00 pm ET in the Convention Center, Room 318-319 on Level 300 at the AES 2019 Annual Meeting.

About Xenon Pharmaceuticals Inc.

We are a clinical stage biopharmaceutical company committed to developing innovative therapeutics to improve the lives of patients with neurological disorders, including rare central nervous system (CNS) conditions. We are advancing a novel product pipeline of neurology therapies to address areas of high unmet medical need, with a focus on epilepsy. For more information, please visit www.xenon-pharma.com.

Safe Harbor Statement

This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934 and the Private Securities Litigation Reform Act of 1995 and Canadian securities laws. These forward-looking statements and supporting assumptions are not based on historical fact, and include statements regarding the timing of and results from clinical trials and pre-clinical development activities, including those related to XEN901 and our and our collaborators' other product candidates; the potential efficacy, safety profile, future development plans, addressable market, regulatory success and commercial potential of XEN901 and our and our collaborators' other product candidates; the anticipated timing of IND, or IND-equivalent, submissions and the initiation of future clinical trials for XEN901 and our and our collaborators' other product candidates; our and our collaborators' ability to successfully develop and achieve milestones in development programs; the timing and results of interactions with regulators; the progress and potential of our other ongoing development programs; the potential receipt of milestone payments and royalties from our collaborators and partners; and the timing of potential publication or presentation of future clinical data. 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 trials may not demonstrate safety and efficacy of any of our or our collaborators' product candidates; our ongoing discovery and pre-clinical efforts may not yield additional product candidates; any of our or our collaborators' product candidates 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; the impact of competition; the impact of expanded product development and clinical activities on operating expenses; adverse conditions in the general domestic and global economic markets; as well as the other risks identified in our filings with the 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.

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Investor/Media Contact:
Jodi Regts
Xenon Pharmaceuticals Inc.
Phone: 604.484.3353
Email: [email protected]