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TerminatedNCT04873869Updated Oct 16, 2025Results posted

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

A Phase 2 interventional study of NBI-921352 and Placebo in SCN8A Developmental and Epileptic Encephalopathy Syndrome, sponsored by Neurocrine Biosciences. Terminated at 4 sites in United States. Open to participants aged 2 Years to 21 Years. Per ClinicalTrials.gov, last updated 2025-10-16.

Sponsored by Neurocrine Biosciences · Phase 2, Interventional, and Treatment

Why this study was terminated
This study was prematurely terminated due to sponsor decision.
Phase
Phase 2
Study type
Interventional
Enrollment
8
Allocation
Randomized
Ages
2 Years to 21 Years
Sex
All
01

Study summary

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).

02

Conditions studied

  • SCN8A Developmental and Epileptic Encephalopathy Syndrome

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Keywords

  • Epilepsy
  • Sodium channel
  • voltage-gated
  • type VIII
  • alpha subunit (SCN8A)
  • NaV1.6 inhibitor
03

In context

Epilepsy

1,805 studies on the registry are indexed under Epilepsy; 417 are open to participants now.

This study's enrollment of 8 is below the median of 50 across 1,206 interventional studies indexed under Epilepsy.

Browse Epilepsy studies →

Lead sponsor

Neurocrine Biosciences is the lead sponsor of 85 studies on the registry; 16 are open to participants now.

Of its 35 completed or terminated interventional studies of FDA-regulated products, 23 (66%) have results posted.

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

04

Who can participate

Ages eligible
2 Years to 21 Years
Sexes eligible
All
Accepts healthy volunteers
No

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

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.
05

Study design

Phase
Phase 2
Primary purpose
Treatment
Allocation
Randomized
Intervention model
Parallel assignment
Masking
Triple (Participant, Care provider, Investigator)
Enrollment
8 participants (actual)

Study arms

  • Placebo comparator
    Placebo

    Participants will receive matching placebo for up to 18 weeks.

    Drug: Placebo

  • 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

Interventions

  • DrugNBI-921352

    Administered orally

  • DrugPlacebo

    Administered orally

06

What researchers measure

Primary outcomes

  1. 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

Secondary outcomes

  1. Percentage of Participants With a Treatment Response

    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.

    Time frame: Planned time frame: Baseline to Week 16

  2. 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

  3. Percentage of Participants With a ≥ 25%, ≥ 75%, or 100% Treatment Response During the 16-week Treatment Period

    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.

    Time frame: Planned time frame: Baseline to Week 16

  4. Percentage of Participants With a ≥25%, ≥50%, ≥75%, or 100% Treatment Response During the 10-week Maintenance Period

    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.

    Time frame: Planned time frame: Baseline, Week 6 to Week 16

  5. Clinical Global Impression of Change (CGIC) Score at Each Visit During the 16-week Treatment Period

    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).

    Time frame: Planned time frame: Up to Week 16

  6. Parent/Caregiver Global Impression of Change (GIC) Score at Each Visit During the 16-week Treatment Period

    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).

    Time frame: Planned time frame: Up to Week 16

  7. Change From Baseline in Clinical Global Impression of Severity (CGIS) Scores at Each Visit During the 16-week Treatment Period

    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).

    Time frame: Planned time frame: Baseline to Week 16

  8. Change From Baseline in Parent/Caregiver Global Impression of Severity (GIS) Scores at Each Visit During the 16-week Treatment Period

    The GIS scale was used to assess overall severity on a 5-point scale (range: 1=none to 5=very severe).

    Time frame: Planned time frame: Baseline through Week 16

07

Results

Posted Oct 16, 2025
Limitations and caveats
Due to the early termination, only 8 participants were enrolled and completed the study.

Participant flow

Study was prematurely terminated due to sponsor decision. Due to the early termination, only 8 participants were enrolled and completed the study. As prespecified, analyses were pooled by treatment received (NBI-921352 or placebo), rather than specific dose level received.

Participant flow — Overall Study
MilestoneNBI-921352Placebo
Started44
Received study drug44
Completed44
Not completed00

Outcome measures

PrimaryPercentage 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

No measurements were reported for this outcome.

SecondaryPercentage of Participants With a Treatment Response

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.

Time frame:
Planned time frame: Baseline to Week 16

No measurements were reported for this outcome.

SecondaryPercentage 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

No measurements were reported for this outcome.

SecondaryPercentage of Participants With a ≥ 25%, ≥ 75%, or 100% Treatment Response During the 16-week Treatment Period

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.

Time frame:
Planned time frame: Baseline to Week 16

No measurements were reported for this outcome.

SecondaryPercentage of Participants With a ≥25%, ≥50%, ≥75%, or 100% Treatment Response During the 10-week Maintenance Period

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.

Time frame:
Planned time frame: Baseline, Week 6 to Week 16

No measurements were reported for this outcome.

SecondaryClinical Global Impression of Change (CGIC) Score at Each Visit During the 16-week Treatment Period

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).

Time frame:
Planned time frame: Up to Week 16

No measurements were reported for this outcome.

SecondaryParent/Caregiver Global Impression of Change (GIC) Score at Each Visit During the 16-week Treatment Period

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).

Time frame:
Planned time frame: Up to Week 16

No measurements were reported for this outcome.

SecondaryChange From Baseline in Clinical Global Impression of Severity (CGIS) Scores at Each Visit During the 16-week Treatment Period

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).

Time frame:
Planned time frame: Baseline to Week 16

No measurements were reported for this outcome.

SecondaryChange From Baseline in Parent/Caregiver Global Impression of Severity (GIS) Scores at Each Visit During the 16-week Treatment Period

The GIS scale was used to assess overall severity on a 5-point scale (range: 1=none to 5=very severe).

Time frame:
Planned time frame: Baseline through Week 16

No measurements were reported for this outcome.

Adverse events

Collected over Up to 30 weeks. Non-serious events are listed at a 0% frequency threshold.

Adverse event summary by group
GroupDeathsSeriousOther
NBI-9213520/4 (0%)2/4 (50%)4/4 (100%)
Placebo0/4 (0%)1/4 (25%)4/4 (100%)
Most frequent serious events
Most frequent serious events
EventNBI-921352Placebo
Parainfluenzae virus infectionInfections and infestations1/40/4
Urinary tract infectionInfections and infestations0/41/4
SeizureNervous system disorders1/40/4
Acute respiratory failureRespiratory, thoracic and mediastinal disorders0/41/4
Most frequent other events
Showing 10 of 32
Most frequent other events
EventNBI-921352Placebo
VomitingGastrointestinal disorders2/40/4
Gait disturbanceGeneral disorders0/42/4
NasopharyngitisInfections and infestations0/42/4
Urinary tract infectionInfections and infestations0/42/4
TachycardiaCardiac disorders1/40/4
ConstipationGastrointestinal disorders1/41/4
PyrexiaGeneral disorders0/41/4
COVID-19Infections and infestations0/41/4
Enterovirus infectionInfections and infestations0/41/4
Otitis mediaInfections and infestations1/40/4

Baseline characteristics

Safety analysis set: Included all participants who received at least 1 dose of study treatment.

Age, Continuous
Age, Continuous(years)NBI-921352PlaceboTotal
Mean4.46 ± 2.609.17 ± 4.876.81 ± 4.40
Sex: Female, Male
Sex: Female, Male(Participants)NBI-921352PlaceboTotal
Female224
Male224
Ethnicity (NIH/OMB)
Ethnicity (NIH/OMB)(Participants)NBI-921352PlaceboTotal
Hispanic or Latino101
Not Hispanic or Latino347
Unknown or Not Reported000
Race (NIH/OMB)
Race (NIH/OMB)(Participants)NBI-921352PlaceboTotal
American Indian or Alaska Native000
Asian000
Native Hawaiian or Other Pacific Islander000
Black or African American000
White448
More than one race000
Unknown or Not Reported000
08

Study locations

4 sites
  • UCSF Medical Center
    San Francisco, California 94158, United States
  • Children's National Hospital
    Washington D.C., District of Columbia 20010, United States
  • University of Rochester
    Rochester, New York 14642, United States
  • Cook Children's Medical Center
    Fort Worth, Texas 76104, United States
09

References and documents

Study documents

  • Study protocol · Nov 30, 2021
  • Statistical analysis plan · Dec 12, 2024

Documents are hosted by the registry — open the source record to download them.

Individual participant data

Plan to share: No

10

Updates

Tracking since Sep 25, 2026
No changes since tracking began. The registry record was last updated on Oct 16, 2025, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗
11

Registry details

Key details

Study ID
NCT04873869
Lead sponsor
Neurocrine Biosciences
Responsible party
Sponsor
First posted
May 5, 2021
Start date
Jan 31, 2022
Primary completion
Mar 17, 2023
Completion
Mar 17, 2023
Results posted
Oct 16, 2025
Last update
Oct 16, 2025

Study contacts

Clinical Development Lead
study director · Neurocrine Biosciences

Oversight

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

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