Study to Evaluate NBI-921352 as Adjunctive Therapy in Subjects With SCN8A Developmental and Epileptic Encephalopathy Syndrome (SCN8A-DEE)

September 30, 2025 updated by: Neurocrine Biosciences

A Phase 2 Randomized, Double-Blind, Placebo-Controlled Study to Evaluate the Efficacy, Safety, Tolerability, and Pharmacokinetics of NBI-921352 as Adjunctive Therapy in Subjects With SCN8A Developmental and Epileptic Encephalopathy Syndrome (SCN8A-DEE)

The objective of this study is to assess the efficacy, safety, and pharmacokinetics of NBI-921352 as adjunctive therapy for seizures in subjects with SCN8A Developmental and Epileptic Encephalopathy Syndrome (SCN8A-DEE).

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Terminated

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
8

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • United States
    • California
      • San Francisco, California, United States, 94158
        • UCSF Medical Center
    • District of Columbia
      • Washington D.C., District of Columbia, United States, 20010
        • Children's National Hospital
    • New York
      • Rochester, New York, United States, 14642
        • University of Rochester
    • Texas
      • Fort Worth, Texas, United States, 76104
        • Cook Children's Medical Center

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

2 years to 21 years (Child, Adult)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  1. Male or female 2 to 21 years of age, inclusive.
  2. Have a diagnosis of SCN8A-DEE supported by both clinical and genetic findings
  3. Have on average at least 1 countable motor seizure per week and not be seizure-free for more than 20 consecutive days
  4. Being treated with at least 1 other antiseizure medication (ASM), but no more than 4 ASMs
  5. Have failed to achieve seizure freedom with at least 2 ASMs
  6. Must be using a nocturnal alerting system or practice consistent with standards of care at the time of screening and continue to use this for the duration of the study
  7. Must have an adequate rescue medication regimen per the investigator's judgment in place at the time of screening and for the duration of the study
  8. Have a body weight of at least 10 kg
  9. The subject's parent/caregiver is able to accurately identify seizure types, especially countable motor seizures (defined as GTCS, tonic, atonic or FOS with noticeable motor component) and is able to complete seizure diary

Exclusion Criteria:

  1. Have previously been enrolled in this study and received blinded treatment
  2. Have participated in an interventional clinical trial < 30 days prior to screening
  3. Have symptoms that would be more consistent with another epilepsy disorder such as Dravet syndrome (eg, fever-induced episodes of status epilepticus, frequent myoclonic seizures, worsening on sodium channel blockers, absence seizures with generalized spike-and-wave EEG as the sole seizure type)
  4. Are currently receiving cannabinoids or medical marijuana except Epidiolex/Epidyolex, unless approved by the Sponsor
  5. Are currently taking systemic steroids (excluding inhaled medication for asthma treatments and intranasal steroids for allergies). If subject has received these medications in the past, must be off these medications for at least 3 months prior to the screening visit and these drugs may not be initiated during the duration of the study. Intermittent steroids to treat nonepilepsy related diseases (such as allergies or dermatological conditions) are not exclusionary
  6. Have a history of moderate or severe head trauma or other neurological disorders or systemic medical diseases that are, in the investigator's opinion, likely to affect nervous system functioning
  7. Have a clinically significant medical condition or chronic disease, that in the opinion of the investigator would preclude the subject from participating in and completing the study or that could confound interpretation of study outcome
  8. Have clinically significant abnormal vital signs at the screening visit as determined by the investigator
  9. Have one or more clinical laboratory test values outside the reference range, based on blood samples taken at the screening visit, that are of potential risk to the subject's safety as determined by the investigator
  10. Have, at the screening visit, an electrocardiogram (ECG) finding of a corrected QT interval using Fridericia's formula (QTcF) > 450 msec or presence of any significant cardiac abnormality.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Triple

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Placebo Comparator: Placebo
Participants will receive matching placebo for up to 18 weeks.
Drug: Placebo
Administered orally
Experimental: NBI-921352
In the first 6 weeks participants will receive increasing doses of NBI-921352 (Titration Period) based on weight, followed by 10 weeks of treatment at their final tolerated dose (Maintenance Period) and 2 weeks of treatment with decreasing doses (Taper Period).
Drug: NBI-921352
Administered orally

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Time Frame
Percentage Change From Baseline in 28-day Seizure Frequency for Countable Motor Seizures During the 16-week Treatment Period
Time Frame: Planned time frame: Baseline to Week 16
Planned time frame: Baseline to Week 16

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Percentage of Participants With a Treatment Response
Time Frame: Planned time frame: Baseline to Week 16
Treatment response was defined as a ≥50% decrease from baseline in 28-day seizure frequency for countable motor seizures during the treatment period of the study.
Planned time frame: Baseline to Week 16
Percentage Change From Baseline in 28-day Seizure Frequency for Countable Motor Seizures During the 10-week Maintenance Period
Time Frame: Planned time frame: Baseline, Week 6 to Week 16
Planned time frame: Baseline, Week 6 to Week 16
Percentage of Participants With a ≥ 25%, ≥ 75%, or 100% Treatment Response During the 16-week Treatment Period
Time Frame: Planned time frame: Baseline to Week 16
Treatment response was defined as a ≥25%, ≥50%, ≥75%, or 100% decrease from baseline in 28-day seizure frequency for countable motor seizures during the treatment period of the study.
Planned time frame: Baseline to Week 16
Percentage of Participants With a ≥25%, ≥50%, ≥75%, or 100% Treatment Response During the 10-week Maintenance Period
Time Frame: Planned time frame: Baseline, Week 6 to Week 16
Treatment response was defined as a ≥25%, ≥50%, ≥75%, or 100% decrease from baseline in 28-day seizure frequency for countable motor seizures during the treatment period of the study.
Planned time frame: Baseline, Week 6 to Week 16
Clinical Global Impression of Change (CGIC) Score at Each Visit During the 16-week Treatment Period
Time Frame: Planned time frame: Up to Week 16
The CGIC scale, which is based on a 7-point scale (range: 1=very much improved to 7=very much worse), was used to rate the overall global improvement since the initiation of study treatment dosing, as rated by the investigator (or qualified designee).
Planned time frame: Up to Week 16
Parent/Caregiver Global Impression of Change (GIC) Score at Each Visit During the 16-week Treatment Period
Time Frame: Planned time frame: Up to Week 16
The GIC scale was used to assess the parent/caregiver's impression of change in the participant's overall condition since starting study treatment and was rated on a 7-point scale (1=very much improved to 7=very much worse).
Planned time frame: Up to Week 16
Change From Baseline in Clinical Global Impression of Severity (CGIS) Scores at Each Visit During the 16-week Treatment Period
Time Frame: Planned time frame: Baseline to Week 16
The CGIS scale was used to assess overall severity on a 5-point scale (range: 1=normal, not at all ill to 5=among the most extremely ill).
Planned time frame: Baseline to Week 16
Change From Baseline in Parent/Caregiver Global Impression of Severity (GIS) Scores at Each Visit During the 16-week Treatment Period
Time Frame: Planned time frame: Baseline through Week 16
The GIS scale was used to assess overall severity on a 5-point scale (range: 1=none to 5=very severe).
Planned time frame: Baseline through Week 16

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Neurocrine Biosciences

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Study Director: Clinical Development Lead, Neurocrine Biosciences

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
January 31, 2022

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
March 17, 2023

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
March 17, 2023

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
April 30, 2021

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
April 30, 2021

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
May 5, 2021

Study Record Updates

Last Update Posted (Estimated)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
October 16, 2025

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 30, 2025

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
September 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • NBI-921352-DEE2012
  • 2020-003140-83 (EudraCT Number)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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