Developmental and Epileptic EncephalopathyPhase 1/2NCT06983158
A Clinical Trial of CAP-002 Gene Therapy in Pediatric Patients With Syntaxin-Binding Protein 1 (STXBP1) Encephalopathy
A Phase 1/2 study testing gene therapy in people with Developmental and Epileptic Encephalopathy, run by Capsida Biotherapeutics, Inc. at 4 sites in United States.
Trial 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. Read more about this study
- Who is it for?
- Ages 18 months to 7 years
- Conditions the study is for
- Developmental and Epileptic Encephalopathy
- What is being tested?
- gene therapy
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 1 participants
- Where
- 4 sitesUnited States
- Study dates
- 3 Jul 2025to 26 May 2026
- Phase
- Phase 1/2
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 months to 7 years
- All sexes
- No healthy volunteers
- Child
Who may be able to join
- 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.
Who cannot join
- 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;
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- 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.
Trial locations and contacts
4 sites in 1 country.
United States4 sites
Colorado Child Health Research Institute
Aurora, Colorado, 80045
Texas Children's Hospital
Houston, Texas, 77030
Weill Cornell Medicine
New York, New York, 10021
Buerger Center for Advanced Pediatric Care, Children's Hospital of Philadelphia
Philadelphia, Pennsylvania, 19146
About this study
Official title: A Phase 1/2a, Open-Label, Multi-Center, Dose-Escalation Trial to Assess Safety, Tolerability, and Efficacy of a Single Dose of CAP-002 Gene Therapy Administered to Pediatric Patients With Syntaxin-Binding Protein 1 (STXBP1) Encephalopathy
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.
Read the detailed description
This is a Phase 1/2a, FIH, open-label, multi-center, dose-escalation trial to assess the safety, tolerability, and efficacy of a single intravenous (IV) dose of CAP-002 administered to participants with syntaxin-binding protein#1 (STXBP1) encephalopathy ages ≥18 months to <8 years of age.
Approximately 12 participants will be dosed in this trial. Phase 1 is a dose escalation phase that will dose approximately 6 participants divided into 2 cohorts (Cohort 1 and Cohort 2) while Phase 2a will have 1 dose cohort and dose approximately 6 participants. Participants in Phase 1 will be dosed sequentially in each cohort. Phase 2a will allow participants to be dosed concurrently if safety and tolerability data from Phase 1 are deemed acceptable.
Participants will receive a single intravenous infusion of CAP-002 and will then be followed for 2 years with safety measures, assessments to measure changes from Baseline in development, language, cognition, motor skills and behavior, a seizure diary and structured caregiver interviews.
Upon completion of the study or at the participant's final visit they will be invited to participate in a 3 year safety follow up study.
- Being tested
- gene therapy
- Keywords
- STXBP1, Gene therapy
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
gene therapyDrug
Intra-venous gene therapy
| Study group | Role | What they receive |
|---|---|---|
| Dose Level 1 | Experimental | Participants will receive a single dose of STXBP1, administered IV Receives: Drug: gene therapy |
| Dose Level 2 | Experimental | Participants will receive a single dose of STXBP1, administered IV Receives: Drug: gene therapy |
What is being measured
The primary outcome is the main question the study is designed to answer.
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
Measured: 2 years
Secondary outcomes (13)
Bayley Scales of Infant and Toddler Development- Fourth Edition
Clinician Scores: 0 to 2; Total Scores: Cognitive 0-162; Receptive 0-84; Expressive 0-74; Fine Motor 0-92; Gross Motor 0-116; High score is a better outcome
Measured: Baseline, Month 6, Month 12, Month 18 and Month 24
Gross Motor Function Measure
Clinician Scores: 0 to 3; Total Score: 0 to 264; High score is a better outcome
Measured: Baseline, Month 6, Month 12, Month 18 and Month 24
Peabody Developmental Motor Scales-Third Edition
Clinician Scores: 0 to 2; High score is a better outcome
Measured: Baseline, Month 6, Month 12, Month 18 and Month 24
STXBP1-Clinical Severity Assessment-Clinician
Clinician Scores: 0 to 100; High score is a worse outcome
Measured: Baseline, Month 6, Month 12, Month 18 and Month 24
Vineland Adaptive Behavior Scales | Third Edition
Caregiver Scores: 0 to 2; Total Scores: Receptive 0-78; Expressive 0-98, Written 0-76, Personal 0-110, Domestic 0-60, Community 0-116, Interpersonal 0- 86, Play and Leisure 0-72, Coping 0-66, Fine Motor 0- 68; Gross Motor 0-86: High score is a better outcome
Measured: Baseline, Month 6, Month 12, Month 18 and Month 24
Observer-Reported Communication Ability
Caregiver Scores: No or only once; Sometimes, Yes, almost all the time; Yes, almost all the time is better outcome
Measured: Baseline, Month 6, Month 12, Month 18 and Month 24
Sensory Profile-2
Caregiver Scores: 1 to 5; Total Score: 0 to 625; High score is a worse outcome
Measured: Baseline, Month 6, Month 12, Month 18 and Month 24
Quality of Life Inventory-Disability
Caregiver Scores: Never, Rarely, Sometimes, Often, Very often; Very Often is better outcome
Measured: Baseline, Week 6, Month 6, Month 12, Month 18 and Month 24
STXBP1-Clinical Severity Assessment-Caregiver
Caregiver Scores: 0 to 100; High score is a worse outcome
Measured: Baseline, Week 4, Week 8, Week 12, Month 4, Month 6, Month 12, Month 18 and Month 24
Aberrant Behavior Checklist
Caregiver Scores: 0 to 3; Total Score: 0-174; High score is a worse outcome
Measured: Baseline, Month 6, Month 12, Month 18 and Month 24
Child Behavior Checklist
Caregiver Scores: 0 to 2; Total Behavior: 0 to 224; High score is a worse outcome
Measured: Baseline, Month 6, Month 12, Month 18 and Month 24
Child's Sleep Habits
Caregiver Scores: 1 to 3; High score is a worse outcome
Measured: Baseline, Month 6, Month 12, Month 18 and Month 24
Seizure frequency
Caregiver assessment: Change from baseline in seizure experience as recorded in a seizure diary
Measured: Baseline and daily though Month 24
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted21 May 2025
- Study start3 Jul 2025
- Primary completion25 Mar 2026
- Study completion26 May 2026
Why it stopped: Stopping rule for study was met
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Developmental and Epileptic EncephalopathyStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 1/2
- Primary purpose
- Treatment
- Allocation
- Non-randomised
- Intervention model
- Sequential
- Masking
- None (open label)
- Enrolment
- 1 participants (actual)
Sponsor and investigators
- Lead sponsor
- Capsida Biotherapeutics, Inc.
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Melanie Brandabur, MD, Study director, Capsida Biotherapeutics
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06983158
- Sponsor's protocol ID
- CAP-002-101
- Other IDs
- SYNRGY
- Status last verified
- Jun 2026
- First submitted
- 5 May 2025
- Last updated
- 10 Jun 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 10 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Phase 1/2a, Open-Label, Multi-Center, Dose-Escalation Trial to Assess Safety, Tolerability, and Efficacy of a Single Dose of CAP-002 Gene Therapy Administered to Pediatric Patients With Syntaxin-Binding Protein 1 (STXBP1) Encephalopathy
- ClinicalTrials.gov ID
- NCT06983158
- Acronym / sponsor ID
- CAP-002-101
- Keywords
- STXBP1, Gene therapy
- Phase
- Phase 1/2
- Study type
- Interventional
- Recruitment status
- TerminatedReason stopped: Stopping rule for study was met
- Enrolment
- 1 participants (actual)
- Lead sponsor
- Capsida Biotherapeutics, Inc.Industry (pharma, biotech, devices)
- Study start
- 3 Jul 2025 (actual)
- Primary completion
- 25 Mar 2026 (actual)
- Study completion
- 26 May 2026 (actual)
- First posted
- 21 May 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Detailed description
This is a Phase 1/2a, FIH, open-label, multi-center, dose-escalation trial to assess the safety, tolerability, and efficacy of a single intravenous (IV) dose of CAP-002 administered to participants with syntaxin-binding protein#1 (STXBP1) encephalopathy ages ≥18 months to <8 years of age.
Approximately 12 participants will be dosed in this trial. Phase 1 is a dose escalation phase that will dose approximately 6 participants divided into 2 cohorts (Cohort 1 and Cohort 2) while Phase 2a will have 1 dose cohort and dose approximately 6 participants. Participants in Phase 1 will be dosed sequentially in each cohort. Phase 2a will allow participants to be dosed concurrently if safety and tolerability data from Phase 1 are deemed acceptable.
Participants will receive a single intravenous infusion of CAP-002 and will then be followed for 2 years with safety measures, assessments to measure changes from Baseline in development, language, cognition, motor skills and behavior, a seizure diary and structured caregiver interviews.
Upon completion of the study or at the participant's final visit they will be invited to participate in a 3 year safety follow up study.
Study design
- Primary purpose
- Treatment
- Allocation
- Non-randomised
- Intervention model
- Sequential
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Dose Level 1 | Experimental | Drug: gene therapyParticipants will receive a single dose of STXBP1, administered IV |
| Dose Level 2 | Experimental | Drug: gene therapyParticipants will receive a single dose of STXBP1, administered IV |
Who may qualify
- Ages
- 18 months to 7 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Child
Key inclusion criteria (4 listed)
- 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.
Key exclusion criteria (9 listed)
- 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;
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| gene therapyIntra-venous gene therapy | Drug | Dose Level 1, Dose Level 2 |
Primary outcome
Primary Safety
Time frame: 2 years
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
13 secondary outcomes
Bayley Scales of Infant and Toddler Development- Fourth Edition
Time frame: Baseline, Month 6, Month 12, Month 18 and Month 24
Gross Motor Function Measure
Time frame: Baseline, Month 6, Month 12, Month 18 and Month 24
Peabody Developmental Motor Scales-Third Edition
Time frame: Baseline, Month 6, Month 12, Month 18 and Month 24
STXBP1-Clinical Severity Assessment-Clinician
Time frame: Baseline, Month 6, Month 12, Month 18 and Month 24
Vineland Adaptive Behavior Scales | Third Edition
Time frame: Baseline, Month 6, Month 12, Month 18 and Month 24
Observer-Reported Communication Ability
Time frame: Baseline, Month 6, Month 12, Month 18 and Month 24
Sensory Profile-2
Time frame: Baseline, Month 6, Month 12, Month 18 and Month 24
Quality of Life Inventory-Disability
Time frame: Baseline, Week 6, Month 6, Month 12, Month 18 and Month 24
STXBP1-Clinical Severity Assessment-Caregiver
Time frame: Baseline, Week 4, Week 8, Week 12, Month 4, Month 6, Month 12, Month 18 and Month 24
Aberrant Behavior Checklist
Time frame: Baseline, Month 6, Month 12, Month 18 and Month 24
Child Behavior Checklist
Time frame: Baseline, Month 6, Month 12, Month 18 and Month 24
Child's Sleep Habits
Time frame: Baseline, Month 6, Month 12, Month 18 and Month 24
Seizure frequency
Time frame: Baseline and daily though Month 24
Results and safety
The study was stopped early (reason given: Stopping rule for study was met). Results are not available in the source record.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 10 Jun 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Melanie Brandabur, MD study director
Capsida Biotherapeutics
4 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1/2 study testing gene therapy in people with Developmental and Epileptic Encephalopathy, run by Capsida Biotherapeutics, Inc. at 4 sites in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: stopped early, as of the sponsor's last update on 10 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 4 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this combined phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
The study was stopped early (reason given: Stopping rule for study was met). Results are not available in the source record.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Primary Safety (time frame: 2 years). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 10 Jun 2026.