ClinicalTrials.gov record NCT07531745

ASCEND: Safety and Tolerability of ION337 for the Treatment of Dravet Syndrome

Record copied from ClinicalTrials.gov: Oct 10, 2026AI summaries generated: Aug 22, 2026

Phase 1-2, Open-Label, Single and Multiple Ascending Dose Study to Evaluate Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Intrathecally-Administered ION337 in Patients With Dravet Syndrome

StatusRecruitingThe study is currently enrolling participants. Only the study team can say whether a particular person can join.
Study typeInterventionalA study in which researchers assign participants to one or more interventions, such as a drug, procedure, device, behavioural programme or other approach, to measure their effects.
PhasePhase 1/2A study that combines safety and dose-finding (phase 1) with a first look at whether the treatment has an effect (phase 2).
Age2 years old to 12 years old
SexAll
LocationCanada, United States
AI summaryWhat this study is about, in plain languageShow ▾Hide ▴

AI-written from the registry record, not the study's own wording. May contain errors or omissions. Check the registry text on this page and the original record ↗ before acting on it.

This open-label phase 1–2 study evaluates intrathecal ION337 in children aged 2 to 12 with Dravet syndrome. Part 1 gives a single ascending dose and follows participants for about 6 months; Part 2 gives multiple ascending doses over 24 months with a 7-month safety follow-up. The main focus is safety and tolerability; the study also measures drug levels and collects seizure frequency data.

What it is studying. The study is testing the safety and tolerability of ION337 given into the spinal fluid, and measuring how the drug behaves in the body (pharmacokinetics) and its biological effects (pharmacodynamics). It also collects data on seizure frequency as a secondary measure.

What the researchers hope to learn. To evaluate safety and tolerability of intrathecal ION337, to measure drug levels in blood and cerebrospinal fluid, to assess pharmacodynamic effects, and to collect seizure-frequency data.

What this study is about

The study's own summary, as published on ClinicalTrials.gov. Underlined terms have a short explanation.

The primary purpose of this study is to evaluate the safety and tolerability of ION337 in participants with Dravet syndrome (DS).

Interventions being studied

Being studied in this trial does not mean the treatment or procedure is approved or available for this condition.

Drug
  • ION337

Eligibility

The criteria exactly as listed on ClinicalTrials.gov. Only the study team can say whether they apply to you.

Inclusion criteria

  • Participant is aged ≥ 2 to ≤ 12 years old at the time of informed consent.
  • Participant has at least 1 parent or caregiver ≥ 18 years old who is willing and able to provide informed consent (signed and dated) and attend all scheduled study visits.
  • Has a documented diagnosis of DS according to the International League Against Epilepsy (ILAE) criteria and as agreed by the Epilepsy Study Consortium, Inc (ESCI).
  • Has confirmation of a pathogenic or likely pathogenic SCN1A variant.
  • Must be currently receiving ≥ 1 concomitant ASM at a stable dose/regimen for ≥ 4 weeks prior to informed consent.
  • Must have all other interventions for epilepsy (including ketogenic diet or VNS) as well as any other concomitant medications including medications for behavioral management, sleep, and supplements or nutritional support stable for ≥ 4 weeks prior to informed consent. Vagus nerve stimulator implantation must have occurred ≥ 6 months prior to informed consent.
  • Experiences the required number of major motor seizures during the Screening Period.
  • Key

Exclusion criteria

  • Known brain or spinal disease that would interfere with the LP procedure or CSF circulation, or presence of other factors that would affect the safety of the LP procedure.
  • Pathogenic or likely pathogenic variant in another gene that causes epilepsy.
  • Has had prior treatment with or is currently enrolled in an interventional clinical trial for a gene therapy or for another antisense oligonucleotide (ASO) for the treatment of DS.
  • Has had treatment with or is currently enrolled in an interventional clinical trial of any other investigational drug, biological agent, or device within 30 days prior to Screening, or 5 half-lives of investigational agent, whichever is longer.
  • Current treatment with an anti-seizure medication (ASM) acting primarily as a sodium channel blocker, as maintenance treatment.
  • Prior brain surgeries including: corpus callosotomy, implantation of device for deep brain stimulation or any other palliative brain surgery intended to reduce seizure burden.
  • Note: Other protocol pre-specified inclusion/exclusion criteria may apply.

Study description and what participation involves

The study's detailed description, as published on ClinicalTrials.gov.

Detailed description from the registry

This is an open-label study of ION337 in people with DS between the ages of 2 and 12 years old (inclusive). The study consists of 2 parts: Part 1) 6-month single ascending dose (SAD) and Part 2) 24-month multiple ascending dose (MAD), followed by a 7-month safety follow up.

AI summaryWhat participation may involve, in plain languageShow ▾Hide ▴

AI-written from the registry record, not the study's own wording. May contain errors or omissions. Check the registry text on this page and the original record ↗ before acting on it.

Participants receive ION337 by intrathecal (spinal) injection. Part 1 is a single ascending dose with follow-up up to about 6 months; participants who complete Part 1 may be eligible for Part 2, which involves multiple ascending doses over 24 months followed by a 7-month safety follow-up. The study includes lumbar punctures for dosing and CSF sampling, blood samples for drug level measurements, regular safety checks (laboratory tests, vital signs, ECGs), physical and neurological exams, and questionnaires including the Columbia Suicidality Severity Rating Scale. Seizure frequency will be recorded to assess changes in major motor seizures.

How the study is structured. Interventional, open-label, non-randomized study with sequential dose escalation. Children receive a single intrathecal dose in Part 1 (single ascending dose, ~6 months follow-up) and, if eligible, may continue to Part 2 for repeated intrathecal doses (multiple ascending dose, 24 months) followed by a 7-month safety follow-up. No masking (participants and researchers know the treatment).

Questions you could ask

These questions are suggestions for a conversation with the study team or your own clinician, not advice.

  • The registry lists this study under Dravet Syndrome. Does it apply to my diagnosis?
  • This is an early-phase study, mainly about safety and dose. What is already known about this treatment?
  • The listed sites are in Canada, United States. Is any of them reachable for me, and does the study help with travel?
  • Which of the eligibility criteria would need to be checked with tests before I could join?

More on CDKL5 deficiency disorder

This trial is also listed on this site under Dravet syndrome.

Clinical trials22 trials listed for CDKL5 deficiency disorderEvery trial the registry lists for CDKL5 deficiency disorder, with recruitment status, phase and sites, updated from ClinicalTrials.gov.See all trials →Research updatesWhat changed in CDKL5 deficiency disorder researchLatest monthly update: September 2026. Includes: EEG background changes. New research summarized each month in plain language, with links to every source paper.Read the latest update →

Important dates

Study start
May 21, 2026
Primary completion
December 2030 (estimated)
Study completion
December 2030 (estimated)
Target enrollment
32 participants (estimated)
Last updated on registry
Sep 3, 2026
Data verified
Oct 10, 2026

Sponsor and research team

The lead sponsor funds and oversees the trial. A pharmaceutical or biotech company sponsor typically means the study is testing that company's drug or device; a hospital, university, or government agency usually indicates investigator-initiated or publicly funded research.

Lead sponsor
Ionis Pharmaceuticals, Inc.

Central study contact

If you're interested in participating, the central contact can answer general questions about the study — including eligibility requirements and how to find a recruiting site near you. Actual eligibility is determined by the site's medical team.

Participating sites (6)

  • University of Michigan Health SystemRecruiting

    Ann Arbor, Michigan, 48109 · United States

  • Mayo ClinicRecruiting

    Rochester, Minnesota, 55905 · United States

  • Duke University Health SystemsRecruiting

    Durham, North Carolina, 27705 · United States

  • Le Bonheur Children's HospitalRecruiting

    Memphis, Tennessee, 38103 · United States

  • Seattle Children's HospitalRecruiting

    Seattle, Washington, 98105 · United States

  • McGill University Health Center - Research InstituteRecruiting

    Montreal, H4A 3J1 · Canada

Terms used on this page · explanations by MedicalUpdates.ai

primary purpose
The main reason an interventional study is being done, for example treatment, prevention, diagnosis, supportive care or basic science.
informed consent
The process of explaining a study, including its risks and what participation involves, so that a person can decide freely whether to take part. Consent is usually documented in writing, and a participant can choose to leave the study later.
stable dose
A dose that has not changed for a defined period before the study starts. Studies may require this so that background treatment is relatively stable when study measurements begin.
concomitant medications
Other medicines a participant takes during the study. Some must be reported; some are restricted.
Screening Period
The checks done before enrolment to see whether a person qualifies, such as tests, scans or a review of medical history.
prior treatment
Treatment a person has already had for the condition. A 'line of therapy' is one course of treatment; studies often require, or limit, the number of prior lines.
investigational drug
A treatment that is being tested and has not been approved for this use. It may be approved for a different condition. Being studied does not mean it works or is available outside the study.
5 half-lives
The time it takes for the amount of a drug in the body to fall by half. 'Five half-lives' is often used as the point at which a previous drug has essentially left the body.
exclusion criteria
The conditions that rule a person out even if they meet the inclusion criteria, for example other illnesses, certain medicines or pregnancy.
Key Inclusion Criteria
The conditions a person must meet to be considered for the study, for example a confirmed diagnosis, an age range or a test result.
open-label
No masking is used, so the assigned intervention is not deliberately hidden from participants or study staff.
ascending dose
Groups of participants receive increasing doses of a treatment, one group after another, to find a dose that can be given safely.
follow up
The period after treatment or enrolment during which participants are observed or contacted, for example to record side effects or outcomes.

The study record on this page is reproduced from ClinicalTrials.gov, a database of the U.S. National Library of Medicine, where it was submitted by the study sponsor. MedicalUpdates.ai does not own this content, is not affiliated with or endorsed by ClinicalTrials.gov, NIH, or the U.S. Government, and does not verify the record. Plain-language notes, the glossary and the questions above are added by this site; text in the boxes marked "AI summary" was written by an AI model and may contain errors. Registry records change over time. Check the original record for the current version and discuss eligibility or participation with a qualified healthcare professional.

← Back to clinical trials