Xenon Pharmaceuticals Presents Corporate Update on Neurology-Focused Pipeline at the Jefferies 2019 Healthcare Conference

Company Highlights Recent Regulatory Feedback Guiding the Clinical Development of XEN901 into Pediatric SCN8A-EE Patients

Webcast of Conference Presentation at 11:00 am ET Today

BURNABY, British Columbia, June 05, 2019 (GLOBE NEWSWIRE) -- Xenon Pharmaceuticals Inc. XENE, a clinical stage biopharmaceutical company, announced that Dr. Simon Pimstone, Xenon's Chief Executive Officer, will present a business update today at the Jefferies 2019 Healthcare Conference in New York, NY at 11:00 am ET.

The presentation will focus on the company's proprietary clinical stage epilepsy products, including XEN496, XEN1101, and XEN901, and will highlight recent regulatory feedback guiding the clinical development of XEN901, a potent, highly selective Nav1.6 sodium channel inhibitor being developed for the treatment of epilepsy.

Dr. Simon Pimstone said, "We continue to execute on the clinical development plans for the promising neurology product candidates within our proprietary pipeline, with the aim of having multiple products in Phase 2 or later stage development this year. Recently, we received important feedback from the FDA regarding the requirements for clinical development of our XEN901 program, including feedback to support advancing XEN901 directly into a pediatric clinical trial examining its efficacy in pediatric patients with SCN8A epileptic encephalopathy (SCN8A-EE). We are currently in the process of completing a pediatric formulation of XEN901 and juvenile toxicology studies to support pediatric development activities."

Dr. Pimstone continued, "Looking ahead to next steps, we intend to run a Phase 1 pharmacokinetic (PK) study in adults with the new XEN901 pediatric formulation beginning late in the third quarter of this year, and then submit an IND to start a proposed Phase 2/3 clinical trial in SCN8A-EE patients. More details about the final trial design, criteria and endpoints will be disclosed over the coming months. As we continue to define a clinical development pathway forward that is focused on pediatric patients, we look forward to advancing therapeutics that may address rare and severe epilepsies and potentially provide much-needed new treatments for young patients, such as those children diagnosed with SCN8A-EE."

Summary of XEN901 Phase 1 Clinical Trial Results and Next Steps

Xenon has completed a randomized, double-blind, placebo-controlled Phase 1 clinical trial to evaluate XEN901's safety, tolerability and PK in both SAD and MAD cohorts of healthy adult subjects, and a related transcranial magnetic stimulation (TMS) study. To summarize the promising Phase 1 results:

• XEN901 PK data demonstrated dose proportionality with a predicted half-life of 8 to 11 hours, which suggests that XEN901 could be compatible with a once or twice daily dosing regimen.
   
• The majority of adverse events (AEs) in the Phase 1 trial were deemed unrelated to XEN901; all were mild or moderate, transient and resolved spontaneously.  There have been no serious AEs, or clinically significant ECG, vital signs or laboratory findings.
   
• Within a pilot TMS study, like with XEN1101, the observed changes in baseline EEG, TMS-EMG and TMS-EEG parameters suggest activity of XEN901 in the target CNS tissue.

Based on pre-clinical results and the PK and safety profile demonstrated by XEN901 in the Phase 1 clinical trial, Xenon is planning for Phase 2 development. Feedback from the FDA suggests that Xenon may be able to advance XEN901 directly into a Phase 2, or later stage, clinical trial examining efficacy in pediatric patients with SCN8A-EE, without requiring an adult clinical trial first. Xenon is currently in the process of completing a pediatric formulation of XEN901 and juvenile toxicology studies to support pediatric development activities. Xenon intends to run a Phase 1 pharmacokinetic (PK) study in adults with the new pediatric formulation beginning late in the third quarter of this year, and then initiate a Phase 2/3 clinical trial in SCN8A-EE patients. More details about the final trial design, anticipated timing, criteria, and endpoints will be disclosed over the coming months.

About XEN901
Xenon is developing XEN901, a potent, highly selective Nav1.6 sodium channel inhibitor, for the treatment of epilepsy. By selectively targeting Nav1.6, it is anticipated that XEN901 may achieve efficacy conferred by this well-validated epilepsy target, but with a potentially improved therapeutic index compared with currently available non-selective sodium channel inhibitors. There is strong human genetic validation supporting the rationale for treating epilepsy by blocking the Nav1.6 sodium channel. Nav1.6 is the most highly expressed sodium channel in the excitatory pathways in the CNS. When mutations in the SCN8A gene, which encodes the Nav1.6 sodium channel, result in a gain of function in the Nav1.6 sodium channel, children can present with a very severe form of SCN8A Epileptic Encephalopathy, or SCN8A-EE (also known as EIEE13).

About SCN8A-EE
SCN8A Epileptic Encephalopathy (SCN8A-EE), also known as EIEE13, is a rare, extremely severe, single-gene epilepsy caused by mutations in the SCN8A gene that result in a gain-of-function in the Nav1.6 sodium channel. SCN8A-EE typically presents with seizure onset between birth and 18 months of age. Most children diagnosed with SCN8A-EE have seizures that can occur multiple times a day and are often difficult to treat. Other symptoms include learning difficulties, muscle spasms, low or high muscle tone, poor coordination, developmental delay, and features similar to autism. The extent of physical disability leaves some children able to make little or no voluntary movement. Most children will have trouble learning to speak, and some will need assistance from feeding tubes to get the nourishment they need to grow. It is also believed that children and teenagers with SCN8A-EE are at risk for Sudden Unexpected Death in Epilepsy (SUDEP).

Webcast Information
Xenon will host a webcast presentation today at 11:00 am Eastern Time (8:00 am Pacific Time) at the Jefferies 2019 Healthcare Conference. The webcast will be broadcast live on the "Investors" section of Xenon's website at www.xenon-pharma.com and will be available for replay following the conference.

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 XEN496, XEN901, XEN1101 and our other product candidates; the potential efficacy, safety profile, future development plans, addressable market, regulatory success and commercial potential of XEN496, XEN901, XEN1101, and our other product candidates; the anticipated timing of IND, or IND equivalent, submissions and the initiation of future clinical trials for XEN496, XEN901, XEN1101 and our other product candidates; the efficacy of our clinical trial designs; our ability to successfully develop and achieve milestones in the XEN496, XEN901, XEN1101 and other development programs; the timing and results of our interactions with regulators; the potential to advance certain of our product candidates directly into Phase 2 or later stage clinical trials; anticipated enrollment in our clinical trials; the progress and potential of our other ongoing development programs; 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; regulatory agencies may not permit certain of our product candidates to advance directly into a Phase 2 or later clinical trials, may impose additional requirements or delay the initiation of clinical trials; 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.

"Xenon" and the Xenon logo are registered trademarks or trademarks of Xenon Pharmaceuticals Inc. in various jurisdictions. All other trademarks belong to their respective owner.

Investor/Media Contact:
Jodi Regts
Xenon Pharmaceuticals Inc.
Phone: 604.484.3353
Email: investors@xenon-pharma.com