XEN496 (Ezogabine) in Children With KCNQ2 Developmental and Epileptic Encephalopathy

Overview

To investigate the potential antiseizure effects of adjunctive XEN496 (ezogabine) compared with placebo in children with KCNQ2 Developmental and Epileptic Encephalopathy (KCNQ2-DEE).

Full Title of Study: “A Phase 3 Study of Adjunctive XEN496 in Pediatric Subjects With KCNQ2 Developmental and Epileptic Encephalopathy”

Study Type

  • Study Type: Interventional
  • Study Design
    • Allocation: Randomized
    • Intervention Model: Parallel Assignment
    • Primary Purpose: Treatment
    • Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
  • Study Primary Completion Date: November 2022

Detailed Description

The EPIK Phase 3 clinical trial is designed as a randomized, double-blind, placebo-controlled, multicenter study targeting to enroll approximately 40 pediatric subjects (aged from 1 month to less than 6 years) with documented genetic evidence consistent with a diagnosis of KCNQ2 Developmental and Epileptic Encephalopathy (KCNQ2-DEE). After screening, subjects will enter a baseline period before being randomized to receive either XEN496 (ezogabine) or placebo, added to their existing antiseizure medications (ASMs), for 12 weeks (maintenance), once a titration period of up to 24 days is complete. At the end of the maintenance phase, eligible subjects will have the opportunity to qualify for and participate in the separate open-label extension (OLE) study and receive XEN496 or, should they choose to exit the study, will undergo a dose taper period of up to 18 days and 4-week follow-up.

Interventions

  • Drug: XEN496
    • XEN496 sprinkle capsules. Parents / caregivers will be instructed to sprinkle and mix the contents of the capsules into soft foods or liquids and feed it to the child.
  • Drug: Placebo
    • Placebo sprinkle capsules. Parents / caregivers will be instructed to sprinkle and mix the contents of the capsules into soft foods or liquids and feed it to the child.

Arms, Groups and Cohorts

  • Experimental: XEN496
    • 24-day dose titration period to a top dose of 21 mg/kg/day. Subjects continue at the top dose, or the highest tolerated dose up to the top dose, for 12-week maintenance period. If the subject does not immediately enter into the separate open-label extension (OLE) study, the maintenance period will be followed by a 18-day taper period.
  • Placebo Comparator: Placebo
    • To maintain the blinded aspect of the study, subjects will be titrated on placebo over the 24-day period and remain at this dose for the 12-week maintenance period. If the subject does not immediately enter into the separate OLE study, the maintenance period will be followed by a 18-day taper period.

Clinical Trial Outcome Measures

Primary Measures

  • Percent change from baseline in monthly (28 day) countable motor seizure frequency during the blinded treatment period
    • Time Frame: From baseline to the end of the double-blind, 12 week treatment period (maintenance)
    • Parent/caregiver seizure diary record will be used to assess frequency, type and duration of seizure activity

Secondary Measures

  • Proportion of subjects with ≥50 percent reduction in monthly (28 day) seizure frequency
    • Time Frame: From baseline to the end of the double-blind, 12 week treatment period (maintenance)
    • Parent/caregiver seizure diary record will be used to assess frequency, type and duration
  • Caregiver Global Impression of Change (CaGI-C) scores for the subject’s overall condition and for seizures
    • Time Frame: Study Days 24, 67, 88 and 109
    • CaGI-C scale is a caregiver-reported assessment for the subject’s overall condition and for seizures. Responses to the CaGI-C questionnaire are to be rated on a 7 item Likert scale ranging from very much improved to very much worse.
  • Change from baseline in the Caregiver Global Impression of Severity (CaGI-S) for the subject’s overall condition and for seizures
    • Time Frame: Study Days 1, 24, 67, 88 and 109
    • CaGI-S scale is Caregiver-reported assessment of the severity of the subject’s seizures and overall condition over the previous 7 days. Responses to the CaGI-S questionnaire are to be rated on a 5 item Likert scale ranging from none to very severe.

Participating in This Clinical Trial

Inclusion Criteria

  • Male or female subjects aged from 1 month to less than 6 years, with a body weight of ≥3.0 kg at screening. – Documented evidence of a genetic test result from an appropriately accredited laboratory, consistent with a diagnosis of KCNQ2-DEE (pathogenic, likely pathogenic, variant of unknown significance, or inconclusive but unlikely to support an alternate diagnosis). – Seizure onset within 2 weeks after birth and EEG and documented clinical history consistent with KCNQ2-DEE. – Magnetic resonance imaging has been performed and is without evidence of structural abnormalities, including but not limited to, hypoxia, hypoxia-ischemia, ischemia (arterial or venous), stroke, sinovenous thrombosis, intracranial hemorrhage, or focal or global brain malformation. – Must have had focal tonic or other countable motor seizures in the 28 days prior to screening. – Taking 1 and no more than 4 concomitant antiseizure medications (ASMs). All doses must be stable for at least 1 week prior to screening and expected to be maintained throughout the duration of the study. – Vagal nerve stimulation (VNS) is allowed and will not be counted as a concomitant ASM. The VNS device must be implanted for at least 6 months before screening, and the device settings must be stable for at least 6 weeks prior to screening and throughout the duration of the study. Use of the VNS device magnet is allowed. – Ketogenic diet is allowed and will not be counted as a concomitant ASM. Must must be on a stable dietary regimen that produces ketosis for at least 6 weeks prior to screening, and expected to be maintained throughout the study. – Additional inclusion criteria apply, and will be assessed by the study team. Exclusion Criteria:
  • Presence of a pathogenic or likely pathogenic variant in an additional gene associated with other epilepsy syndromes. – Presence of a known gain-of-function variant in the KCNQ2 gene, or clinical characteristics consistent with previously reported pathogenic gain-of-function variants in the KCNQ2 gene. – Seizures secondary to infection, neoplasia, demyelinating disease, degenerative neurological disease, or Central nervous system (CNS) disease deemed progressive, metabolic illness, or progressive degenerative disease. – Confirmed diagnosis of infantile spasms within the past month prior to screening. – History or presence of any significant medical or surgical condition or uncontrolled medical illness at screening including, but not limited to, cardiovascular, gastrointestinal, hematologic, hepatic, ocular, pulmonary, renal, or urogenital systems, or other conditions that would not justify the subject's participation in the study, as determined by the investigator's risk benefit assessment. – QT interval corrected for heart rate by Fridericia's formula (QTcF) of >440 msec. In addition, subjects with a history of arrhythmia, prolonged QT, heart disease or subjects taking medications known to increase the QT interval. – History of hyperbilirubinemia, which lasts longer than 1 week will require exclusion of hepatic disease before entering the study. – History of bilirubin-induced neurological dysfunction. – Current disturbance of micturition or known urinary obstructions or history of bladder or urinary dysfunction including abnormal post-void residual bladder ultrasound, vesicoureteral reflux, urinary retention, or required urinary catheterization in the preceding 6 months. – Known to have a terminal illness. – Any clinically significant laboratory abnormalities or clinically significant abnormalities on pre-study physical examination, vital signs, or ECG that in the judgment of the investigator indicates a medical problem that would preclude study participation. – Planned to begin a ketogenic or other specialized dietary therapy during the study. – Caregiver history of chronic noncompliance with their child's prescribed drug regimens that has not been corrected. – Exposure to any other investigational drug or device within 5 half-lives or 30 days prior to screening, whichever is longer or plans to participate in another drug or device trial at any time during the study. – Concurrent enrollment in any other type of medical research judged by the investigator not to be scientifically or medically compatible with this study. – Using felbamate presenting with clinically significant abnormalities and/or hepatic dysfunction during felbamate treatment, and subjects who have taken felbamate for less than 6 months prior to screening. – Currently taking adrenocorticotropic hormone. – Did not tolerate ezogabine when taken previously. – Other exclusion criteria apply, and will be assessed by the study team.
  • Gender Eligibility: All

    Minimum Age: 1 Month

    Maximum Age: 6 Years

    Are Healthy Volunteers Accepted: No

    Investigator Details

    • Lead Sponsor
      • Xenon Pharmaceuticals Inc.
    • Provider of Information About this Clinical Study
      • Sponsor
    • Overall Contact(s)
      • Xenon Pharmaceuticals Inc., 1-604-484-3300, clinicaltrials@xenon-pharma.com

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