March 12, 2026-
New interim data from the Phase 1/2 INSPIRE DUCHENNE clinical trial suggest that SGT-003, an investigational AAV (adeno-associated virus) gene therapy for Duchenne muscular dystrophy (DMD), can successfully deliver microdystrophin and help preserve muscle health in treated patients.
The findings were presented at the 2026 Muscular Dystrophy Association (MDA) Clinical & Scientific Conference in Orlando by Aravindhan Veerapandiyan, MD, principal investigator of the study at Arkansas Children’s Hospital.
SGT-003 is being developed by Solid Biosciences as a systemic AAV gene therapy administered as a single intravenous dose. The therapy uses an AAV vector to deliver a microdystrophin gene to muscle tissue. Patients with DMD lack dystrophin due to mutations in the DMD gene, causing progressive muscle degeneration. The therapy introduces a shortened but functional microdystrophin protein designed to restore muscle protection.
Strong microdystrophin expression observed
As of February, 39 boys aged 1–10 years had received treatment in the ongoing INSPIRE DUCHENNE study. Muscle biopsy data from 20 participants showed that the AAV gene therapy effectively delivered the microdystrophin gene to muscle cells.
After three months, approximately 60% of muscle fibers expressed microdystrophin, and expression remained detectable for up to one year in patients with longer follow-up. Researchers also observed increases in proteins that normally form a protective complex with dystrophin, suggesting broader restoration of muscle structure.
Markers associated with muscle degeneration and injury declined significantly, indicating improved muscle health after treatment.
“What stands out in these data is the biological consistency observed across multiple independent measures of muscle structure, health, and preservation,” Veerapandiyan said during the presentation.
Early signs of functional benefit
Although formal functional endpoints will be analyzed later, preliminary observations suggest improvements in daily physical activities. Videos presented during the conference showed treated patients performing tasks such as climbing stairs, getting into vehicles, and playing outdoors more easily months after receiving the AAV gene therapy.
Cardiac function also appeared stable or improved over time, particularly among patients with lower baseline heart function.
Favorable safety profile
Importantly, SGT-003 demonstrated a strong safety profile, with no evidence of treatment-related liver injury across multiple measures. Liver toxicity has been a concern for some systemically delivered AAV gene therapies, making these findings particularly notable.
The most common treatment-related side effects included nausea, vomiting, and decreased appetite, which were generally manageable.
Participants receive the therapy through a single intravenous infusion of the AAV vector, followed by a temporary high-dose steroid regimen during the first month to reduce immune-related reactions.
Advancing toward late-stage trials
INSPIRE DUCHENNE continues to recruit boys younger than 12 years at clinical sites in the United States, Canada, the United Kingdom, and Italy.
Meanwhile, Solid Biosciences has launched the Phase 3 IMPACT DUCHENNE trial, which plans to enroll approximately 80 ambulatory boys aged 7–11 years. The trial is currently recruiting patients in Australia and Canada, with potential expansion to additional regions including the U.S. and Europe.
According to Bo Cumbo, president and CEO of Solid Biosciences, the company is actively engaging with regulators regarding a potential accelerated approval pathway.
“These interim results reinforce our confidence in the potential of SGT-003 to meaningfully impact the disease course of Duchenne,” Cumbo said.
If confirmed in larger studies, SGT-003 could become a next-generation AAV gene therapy option for patients with Duchenne muscular dystrophy.
