A Clinical Trial of CAP-002 Gene Therapy in Pediatric Patients With Syntaxin-Binding Protein 1 (STXBP1) Encephalopathy

NCT06983158 | Suspended Phase 1 FDA Drug

• 2 other identifiers: CAP-002-101SYNRGY
• Study Type: interventional
• Target: 12
• Locations: 1 country
• Sites: 4

Brief Summary

The goal of this clinical trial is to learn about the safety of CAP-002 gene therapy in children with Syntaxin-Binding Protein 1 (STXBP1) Encephalopathy. It will also provide information about whether CAP-002 demonstrates efficacy in treating children with STXBP1 with and without seizures. Participants will have a single infusion of CAP-002, visit the clinic regularly for 2 years for checkups and tests and have seizures recorded in a diary by their caregiver.

Conditions

Developmental and Epileptic Encephalopathy

Keywords

STXBP1; Gene therapy

Outcome Measures

Primary Outcomes (1)

• Primary Safety

  Incidence of Adverse Events and Serious Adverse Events assessed through Clinical safety laboratory tests (hematology, chemistry, liver function, and urinalysis), ECG, vital sign measurements, and Physical Examinations

  2 years

Secondary Outcomes (13)

• Bayley Scales of Infant and Toddler Development- Fourth Edition

  Baseline, Month 6, Month 12, Month 18 and Month 24

• Gross Motor Function Measure

  Baseline, Month 6, Month 12, Month 18 and Month 24

• Peabody Developmental Motor Scales-Third Edition

  Baseline, Month 6, Month 12, Month 18 and Month 24

• STXBP1-Clinical Severity Assessment-Clinician

  Baseline, Month 6, Month 12, Month 18 and Month 24

• Vineland Adaptive Behavior Scales | Third Edition

  Baseline, Month 6, Month 12, Month 18 and Month 24

Study Arms (2)

Dose Level 1

EXPERIMENTAL

Participants will receive a single dose of STXBP1, administered IV

Drug: gene therapy

Dose Level 2

EXPERIMENTAL

Participants will receive a single dose of STXBP1, administered IV

Drug: gene therapy

Interventions

gene therapy DRUG

Intra-venous gene therapy

Dose Level 1; Dose Level 2

Eligibility Criteria

• Age: 18 Months - 7 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Child (0-17)

You may qualify if:

• Male or female, ≥18 months to \<8 years of age;
• Has diagnosis of developmental encephalopathy due to an STXBP1 mutation with confirmation of a pathogenic or likely pathogenic STXBP1 gene mutation.
• Has a legally authorized representative (LAR) willing and able to complete the informed consent process, willing to comply with trial procedures, and able to travel for repeat visits.
• Is stable on any medication regimens (if being administered to control the signs and symptoms of underlying disease) for at least 6 weeks prior to trial entry and expected to be stable for at least 12 weeks post-CAP-002 administration.

You may not qualify if:

• History of prior gene therapy;
• Treatment with antisense oligonucleotide therapy within 6 months;
• Presence of a confirmed mutation in a gene other than STXBP1 that is known to contribute to a neurodevelopmental disability or epilepsy;
• Has presence of a significant non-STXBP1-related central nervous impairment/behavioral disturbance that would confound the scientific rigor or interpretation of results of the trial;
• History of prematurity (defined as gestational age \<35 weeks), history of low birth weight (\<2.5 kg) and/or intra-uterine growth restriction, significant interventricular hemorrhage, structural brain deficit, or congenital heart disease;
• Known contraindication to immunosuppression or other protocol-defined medications, including but not limited to corticosteroids or PPIs;
• Clinically significant abnormalities in safety lab tests, vital signs;
• Other illnesses or medications that may affect the interpretation of the study results;
• Positive anti-capsid antibody test result.

Sponsors & Collaborators

• Capsida Biotherapeutics, Inc.: lead

Study Sites (4)

Colorado Child Health Research Institute

Aurora, Colorado, 80045, United States

Location

Weill Cornell Medicine

New York, New York, 10021, United States

Location

Buerger Center for Advanced Pediatric Care, Children's Hospital of Philadelphia

Philadelphia, Pennsylvania, 19146, United States

Location

Texas Children's Hospital

Houston, Texas, 77030, United States

Location

MeSH Terms

Interventions

Genetic Therapy

Intervention Hierarchy (Ancestors)

Biological Therapy; Therapeutics; Genetic Engineering; Genetic Techniques; Investigative Techniques

Study Officials

• Melanie Brandabur, MD

  Capsida Biotherapeutics

  STUDY DIRECTOR

Study Design

• Study Type: interventional
• Phase: phase 1
• Allocation: NON RANDOMIZED
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SEQUENTIAL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: May 5, 2025
• First Posted: May 21, 2025
• Study Start: July 3, 2025
• Primary Completion (Estimated): December 20, 2028
• Study Completion (Estimated): December 20, 2028
• Last Updated: October 1, 2025

Record last verified: 2025-07

Data Sharing

• IPD Sharing: Will not share

Locations

US (4)