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RecruitingNCT07531745Updated Nov 2, 2026

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

A Phase 1/2 interventional study of ION337 in Dravet Syndrome, sponsored by Ionis Pharmaceuticals, Inc.. Recruiting at 7 sites in 2 countries. Open to participants aged 2 Years to 12 Years. Per ClinicalTrials.gov, last updated 2026-11-02.

Sponsored by Ionis Pharmaceuticals, Inc. · Phase 1/2, Interventional, and Treatment

From the registry’s dates

  • Started May 2026; still recruiting 5 months later.
Updated Nov 2, 20261 site addedGo to Updates ↓
Phase
Phase 1/2
Study type
Interventional
Enrollment
32
Allocation
Non-randomized
Ages
2 Years to 12 Years
Sex
All
01

Study summary

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

Read the detailed description

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.

02

Conditions studied

  • Dravet Syndrome

Browse trials for

Keywords

  • Dravet syndrome
03

In context

Epilepsies, Myoclonic

92 studies on the registry are indexed under Epilepsies, Myoclonic; 21 are open to participants now.

This study's planned enrollment of 32 is close to the median of 31 across 56 interventional studies indexed under Epilepsies, Myoclonic.

Browse Epilepsies, Myoclonic studies →

Lead sponsor

Ionis Pharmaceuticals, Inc. is the lead sponsor of 118 studies on the registry; 10 are open to participants now.

Of its 49 completed or terminated interventional studies of FDA-regulated products, 22 (45%) have results posted.

Browse Ionis Pharmaceuticals, Inc. studies →

Counted across the registry records on this site, refreshed daily.

04

Who can participate

Ages eligible
2 Years to 12 Years
Sexes eligible
All
Accepts healthy volunteers
No

Eligibility criteria

Key Inclusion Criteria:

  1. Participant is aged ≥ 2 to ≤ 12 years old at the time of .
  2. 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.
  3. 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).
  4. Has confirmation of a pathogenic or likely pathogenic SCN1A variant.
  5. Must be currently receiving ≥ 1 concomitant ASM at a stable dose/regimen for ≥ 4 weeks prior to informed consent.
  6. 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.
  7. Experiences the required number of major motor seizures during the Screening Period.

Key Exclusion Criteria:

  1. 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.
  2. Pathogenic or likely pathogenic variant in another gene that causes epilepsy.
  3. 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.
  4. Has had treatment with or is currently enrolled in an interventional clinical trial of any other drug, biological agent, or device within 30 days prior to Screening, or 5 half-lives of investigational agent, whichever is longer.
  5. Current treatment with an anti-seizure medication (ASM) acting primarily as a sodium channel blocker, as maintenance treatment.
  6. 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.

Terms in these criteria, in plain language(2)

Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.

Informed consent

Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.

You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.

Investigational drug or device

A drug or device being studied in a clinical trial.

It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.

05

Study design

Phase
Phase 1 / Phase 2
Primary purpose
Treatment
Allocation
Non-randomized
Intervention model
Sequential assignment
Masking
None (open label)
Enrollment
32 participants (estimated)

Study arms

  • Experimental
    Part 1: Single Ascending Dose (SAD): Dose Level 1

    Participants aged 2 to ≤ 12 years will receive a single intrathecal bolus (ITB) injection of ION337.

    Drug: ION337

  • Experimental
    Part 1: SAD: Dose Level 2

    Participants aged 2 to ≤ 12 will receive a single dose of ION337.

    Drug: ION337

  • Experimental
    Part 1: SAD: Dose Level 3

    Participants aged 2 to ≤ 12 will receive a single dose of ION337.

    Drug: ION337

  • Experimental
    Part 1: SAD: Dose Level 4

    Participants aged 2 to ≤ 12 will receive a single dose of ION337.

    Drug: ION337

  • Experimental
    Part 2: Multiple Ascending Dose (MAD): Dose Level 1-4

    Only participants who complete Part 1 will be eligible to participate in Part 2. Participants will receive multiple doses of ION337. Participants will begin treatment at the same dose level assigned in Part 1.

    Drug: ION337

Interventions

  • DrugION337

    ION337 will be administered by ITB injection.

06

What researchers measure

Primary outcomes

  1. Parts 1 and 2: Number of Participants with Treatment-emergent Adverse Events (TEAEs) and Serious TEAEs

    Time frame: Part 1: up to 6 months; Part 2: up to 31 months

  2. Number of Participants With Clinically Significant Change From Baseline in Safety Laboratory Values

    Time frame: Part 1: up to 6 months; Part 2: up to 31 months

  3. Parts 1 and 2: Number of Participants With Clinically Significant Change From Baseline in Vital Signs

    Time frame: Part 1: up to 6 months; Part 2: up to 31 months

  4. Parts 1 and 2: Number of Participants With Clinically Significant Change From Baseline in Electrocardiogram (ECG)

    Time frame: Part 1: up to 6 months; Part 2: up to 31 months

  5. Parts 1 and 2: Number of Participants With Clinically Significant Change From Baseline in Physical and Neurological Examination Findings

    Time frame: Part 1: up to 6 months; Part 2: up to 31 months

  6. Parts 1 and 2: Number of Participants with Change in Columbia Suicidality Severity Rating Scale (C-SSRS)

    Time frame: Part 1: up to 6 months; Part 2: up to 31 months

Secondary outcomes

  1. Pharmacokinetic (PK) Parameters Measure Description: Analysis of plasma concentrations of ION337

    Time frame: Pre-Dose Day 1 (Dosing) until 6 months after dosing in Part 1 and up to 31 months in Part 2

  2. Exposure of ION337 in Cerebrospinal Fluid (CSF) Measure Description: Measurement of ION337 concentrations

    Time frame: Pre-dose Day 1 (Dosing) until 6 months after dosing in Part 1 and up to 31 months in Part 2

  3. Parts 1 and 2: Percent Change From Baseline in 28-day Normalized Major Motor Seizure (MMS) Frequency

    Time frame: Part 1: up to 6 months; Part 2: up to 31 months

07

Study locations

7 of 7 sites recruiting
08

References and documents

Individual participant data

Plan to share: Yes — Ionis may share anonymized individual participant data, aggregated clinical data, and other types of data that support the results in this study. Data requests from qualified researchers will be considered once all three of the following criteria are met: (1) 12 months from marketing approval of the study drug in both the United States and European Union; (2) 18 months from conclusion of the study; and (3) 6 months from publication of study article. Access would be via a secure environment and is contingent upon approval of a research proposal and entry into an appropriate data use agreement. Requests to access data can be submitted via the website https://vivli.org/ourmember/ionis/.

Data sharing details ↗ · vivli.org

No publications or documents are linked to this record.

09

Timeline

1 registry update since Sep 25, 2026
ElapsedEstimatedEstimated, not yet reached

Started May 2026 (actual). Primary completion is estimated for Dec 2030, 55 months after the start.

How these figures are worked out, and which studies are left out of them.

Registered
Apr 8, 2026
First posted
Apr 15, 2026
StartActual
May 21, 2026
Primary completionEst.
Dec 2030
CompletionEst.
Dec 2030
Last update
Nov 2, 2026
What these dates mean
Start.
When the first participant enrolled; while estimated, when the study expects to open to recruitment.
Primary completion.
When the last participant was examined or treated to collect data for the study's main question, its primary outcome. A study that stopped early gives the date its data collection stopped.
Completion.
When the last participant's last visit took place, for every outcome, secondary ones and side effects included: the end of the study. Often later than primary completion, sometimes the same day.
Actual and Est.
Actual means the registry says the date has happened. Est. (estimated) is a date the sponsor plans or expects. It can still move, and the sponsor is expected to change it to actual once it has passed.
Sites
1 site added
Show site
  • The Children's Hospital of Philadelphia (CHOP) · Philadelphia, United States
Nov 2, 2026
Show all 1 update
  1. Nov 2, 2026
    1 site added
    Show site
    • The Children's Hospital of Philadelphia (CHOP) · Philadelphia, United States
    + 1 other change: verification date

From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗

10

Registry details

Key details

Study ID
NCT07531745
Lead sponsor
Ionis Pharmaceuticals, Inc.
Responsible party
Sponsor
First posted
Apr 15, 2026
Start date
May 21, 2026
Primary completion
Dec 2030 (estimated)
Completion
Dec 2030 (estimated)
Last update
Nov 2, 2026

Study contacts

Ionis Pharmaceuticals, Inc.
Contact
IonisDravetSyndrome@clinicaltrialmedia.com
(844) 867-4309

Oversight

Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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Discussion

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