Solid Biosciences has reported encouraging interim results from its ongoing Phase 1/2 INSPIRE DUCHENNE clinical trial, evaluating the investigational gene therapy SGT-003 for Duchenne muscular dystrophy (DMD). The data suggest the therapy may help restore critical muscle proteins, improve biomarkers of muscle health, and stabilize heart function in treated participants.
The update was presented at the 2026 Muscular Dystrophy Association (MDA) Annual Meeting, highlighting new findings from muscle biopsies, blood biomarkers, cardiac assessments, and safety monitoring.
INSPIRE DUCHENNE Trial Overview
INSPIRE DUCHENNE is a first-in-human Phase 1/2 clinical trial designed to evaluate the safety, tolerability, and biological activity of SGT-003 in children with Duchenne muscular dystrophy. Read Now: Frequently Asked Questions About Solid Biosciences SGT-003 Gene Therapy
Key features of the study include:
- Single-dose gene therapy infusion
- Dose level of 1E14 vg/kg
- Open-label, multicenter design
- Conducted across 15 clinical sites in the U.S., Canada, Italy, and the United Kingdom
As of March 11, 2026, a total of 40 participants have received SGT-003.
Strong Microdystrophin Expression Observed
Muscle biopsy results showed robust microdystrophin production after treatment. Microdystrophin is a shortened version of the dystrophin protein designed to help stabilize muscle cells in people with Duchenne.
Researchers also observed restoration of key components of the dystrophin-associated protein complex (DAPC), including:
- Beta-sarcoglycan
- Neuronal nitric oxide synthase (nNOS)
These proteins play a critical role in maintaining muscle integrity. In Duchenne muscular dystrophy, the absence of dystrophin destabilizes this complex, leading to muscle damage and degeneration.
SGT-003 is notable because its microdystrophin construct contains the R16/R17 binding domain, which helps correctly localize nNOS in muscle tissue—something not present in many other gene therapy designs.
Biomarker Improvements Suggest Healthier Muscle Fibers
The study also measured multiple biomarkers associated with muscle damage and repair. Results suggest that SGT-003 treatment may help stabilize muscle fibers and reduce ongoing degeneration. Learn More: Biomarkers
One important marker evaluated was embryonic myosin heavy chain (eMHC).
- eMHC is normally expressed during fetal development.
- In Duchenne, it reappears when muscles attempt to repair ongoing damage.
Researchers observed a 44% average reduction in eMHC-positive fibers at Day 90, indicating that the therapy may help interrupt the cycle of muscle degeneration and regeneration commonly seen in Duchenne.
These biomarker improvements suggest:
- Reduced muscle damage
- Improved muscle fiber stability
- Preservation of muscle stem cells
Signs of Stabilized Cardiac Function
Although cardiac measurements were originally included only for safety monitoring, researchers observed stabilization and improvement in heart function following treatment.
Heart function was assessed using left ventricular ejection fraction (LVEF), a measure of how effectively the heart pumps blood.
The improvements were particularly noticeable in participants who had low-normal LVEF levels before treatment.
This finding is especially important because cardiomyopathy is a leading cause of death in Duchenne muscular dystrophy. Studies suggest:
- About 25% of patients show signs of cardiomyopathy by age 6
- Nearly 59% show signs by age 10
Safety and Tolerability
SGT-003 has demonstrated a favorable safety profile so far.
Among the 40 participants treated:
- The therapy has been generally well tolerated
- No major safety concerns have been reported in the interim analysis
Another distinguishing aspect of the treatment is its simplified immune management approach. The therapy is administered using a steroid-only prophylactic immunomodulation regimen, which may reduce treatment burden compared with more complex protocols used in some other gene therapies.
SGT-003 Gene Therapy: INSPIRE DUCHENNE Phase 3 (NCT06138639)
This study is investigating a gene therapy called SGT-003 for patients with Duchenne muscular dystrophy (DMD). There are specific criteria that patients must meet to participate.
Learn More: How Does My Child Participate in Clinical Trials for Duchenne?
Who Can Participate? (Inclusion Criteria)
Age groups:
- Group 1: 4 to under 7 years
- Group 2: 7 to under 12 years
- Group 3: Birth to under 4 years
- Group 4: 12 to under 18 years
- Group 5: 10 to under 18 years
Walking ability:
- Groups 1, 2, and 4: Must be able to walk
- Group 3: Can be walking or non-walking
- Group 5: Must not currently be walking, but must have been able to walk in the past
In addition, participants (where applicable) must be able to complete a 10-meter walk/run in under 30 seconds.
Diagnosis and genetics:
- Must have a confirmed diagnosis of Duchenne muscular dystrophy
- Must have a dystrophin gene mutation consistent with DMD
- In some cases, a muscle biopsy may be required to measure dystrophin levels
Immune status:
- Must test negative for AAV (viral vector) antibodies
Steroid use:
- Groups 1, 2, 4, and 5:
- Must be on a stable daily steroid regimen for at least 12 weeks
- This includes prednisone (at least 0.5 mg/kg/day) or deflazacort (at least 0.75 mg/kg/day)
- Group 3: No steroid requirement
Physical assessments:
- Must meet the 10-meter walk/run test criteria
- Must meet the time-to-stand (from lying down) criteria
- Group 5 must also meet upper limb function requirements (PUL 2.0 test)
Other requirement:
- Body weight must be 90 kg or less
Learn More: NCT06138639
Who Cannot Participate? (Exclusion Criteria)
Participants cannot join the study if they:
- Have used dystrophin-modifying drugs within the last 3 months
- Have previously received any gene therapy (approved or experimental)
- Have taken certain medications within the last 3 months, or before the drug has fully cleared from the body
- Established clinical diagnosis of DMD that is associated with any deletion mutation invariant or variant predicted to not express exons 1 to 11 or, exons 42 to 45, or exons 57 to 69, inclusive, in the DMD gene as documented by a genetic report and confirmed by Sponsor genetic testing.
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