Extension Study to Evaluate How Safe and Tolerable NBI-921352 is as an Adjunctive Therapy for Participants With SCN8A-DEE

NCT05226780 | Active Not Recruiting Phase 2 DMC FDA Drug

• 2 other identifiers: NBI-921352-DEE20132021-004393-62
• Study Type: interventional
• Target: 8
• Locations: 1 country
• Sites: 4

Brief Summary

Extension study to evaluate how safe and tolerable the drug NBI-921352 is when used as adjunctive therapy in participants with SCN8A developmental and epileptic encephalopathy syndrome (SCN8A-DEE).

Conditions

SCN8A Developmental and Epileptic Encephalopathy Syndrome

Keywords

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

Outcome Measures

Primary Outcomes (1)

• The participant incidence of serious treatment-emergent adverse events (TEAEs), TEAEs leading to discontinuation of study treatment, and fatal TEAEs

  Day 1 to Week 168

Secondary Outcomes (1)

• Percentage change from baseline in 28-day seizure frequency for countable motor seizures

  Baseline, up to Week 162

Study Arms (1)

NBI-921352

EXPERIMENTAL

NBI-921352 administered for up to 164 weeks.

Drug: NBI-921352

Interventions

NBI-921352 DRUG

Administered orally

NBI-921352

Eligibility Criteria

• Age: 2 Years - 22 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Child (0-17), Adult (18-64)

You may qualify if:

• For Participants Who Participated in NBI-921352-DEE2012:
• Written or oral pediatric assent from the participant and written informed consent from the participant's parent(s) or legal guardian(s) for pediatric participants and adult participants who are not capable of providing consent. Adult participant who are ≥18 years of age and capable of providing consent should sign an Informed Consent Form (ICF).
• Completed 16 weeks of treatment in Study NBI-921352-DEE2012.
• Continue to use a nocturnal alerting system or practice consistent with standards of care for the duration of the study.
• Have an adequate rescue medication regimen per the investigator's judgment in place for the duration of the study.
• For Participants Who did not Participate in NBI-921352-DEE2012:
• Written or oral pediatric assent from the participant if deemed capable of providing assent and written informed consent from the participant's parent(s) or legal guardian(s) for pediatric participants and for adult participants who are not capable of providing consent. Adult participants who are capable of providing consent should sign an ICF.
• Be a male or female 2 to 21 years of age, inclusive.
• Have a diagnosis of SCN8A-DEE supported by both clinical and genetic findings.
• Have on average at least 1 countable motor seizure per week and not be seizure-free for more than 20 consecutive days.
• Being treated with at least 1 other antiseizure medication (ASM), but no more than 4 ASMs.
• Have failed to achieve seizure freedom with at least 2 ASMs.
• Have a body weight of at least 10 kilograms.

You may not qualify if:

• For Participants Who Participated in NBI-921352-DEE2012:
• \- Have developed any other disorder for which the treatment takes priority over treatment of SCN8A-DEE or is likely to interfere with study treatment or impair treatment compliance.
• For Participants Who did not Participate in NBI-921352-DEE2012:
• Have symptoms that would be more consistent with another epilepsy disorder such as Dravet syndrome (for example, fever-induced episodes of status epilepticus, frequent myoclonic seizures, worsening on sodium channel blockers, absence seizures with generalized spike-and-wave electroencephalogram \[EEG\] as the sole seizure type).
• Currently receiving cannabinoids or medical marijuana except Epidiolex/Epidyolex, unless approved by the Sponsor.
• 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.
• Have a clinically significant medical condition or chronic disease, that in the opinion of the investigator would preclude the participant from participating in and completing the study or that could confound interpretation of study outcome.
• Have clinically significant abnormal vital signs at the screening visit, as determined by the investigator.
• 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 participants safety as determined by the investigator.
• Have, at the screening visit, an electrocardiogram (ECG) finding of a corrected QT interval using Fridericia's formula (QTcF) \> 450 milliseconds (msec) or presence of any significant cardiac abnormality.

Sponsors & Collaborators

• Neurocrine Biosciences: lead

Study Sites (4)

UCSF Medical Center

San Francisco, California, 94143, United States

Location

Children's National Hospital

Washington D.C., District of Columbia, 20010, United States

Location

University of Rochester

Rochester, New York, 14642, United States

Location

Cook Children's Medical Center

Fort Worth, Texas, 76104, United States

Location

MeSH Terms

Conditions

Epilepsy

Condition Hierarchy (Ancestors)

Brain Diseases; Central Nervous System Diseases; Nervous System Diseases

Study Officials

• Clinical Development Lead

  Neurocrine Biosciences

  STUDY DIRECTOR

Study Design

• Study Type: interventional
• Phase: phase 2
• Allocation: NA
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SINGLE GROUP
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: January 26, 2022
• First Posted: February 7, 2022
• Study Start: July 12, 2022
• Primary Completion: March 1, 2026
• Study Completion: March 1, 2026
• Last Updated: July 17, 2025

Record last verified: 2025-07

Data Sharing

• IPD Sharing: Will not share

Locations

US (4)