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

Stopped early · Phase 1/Phase 2

Conditions studied: Developmental and Epileptic Encephalopathy

In brief

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.

Key facts

Study ID

NCT06983158

Run by

Capsida Biotherapeutics, Inc.

People needed

1

Starts

2025-07-03

Expected to finish

2026-05-26

Last updated by the study team

2026-06-10

Who can join

Age: 2 and older, up to 7. Sex: any. Healthy volunteers: not accepted.

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.

Where it is running

• Colorado Child Health Research Institute — Aurora, Colorado, United States
• Weill Cornell Medicine — New York, New York, United States
• Buerger Center for Advanced Pediatric Care, Children's Hospital of Philadelphia — Philadelphia, Pennsylvania, United States
• Texas Children's Hospital — Houston, Texas, United States

Full record on ClinicalTrials.gov

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