Atamyo Therapeutics Shows Promising Early Clinical Data for AAV Gene Therapy ATA-200 in LGMD-R5 Muscular Dystrophy

Evry, France (March 9, 2026) –

Atamyo Therapeutics has reported encouraging early clinical results from its AAV gene therapy ATA-200 for the treatment of limb-girdle muscular dystrophy type R5 (LGMD-R5), also known as gamma-sarcoglycanopathy. The results were presented at the 2026 Muscular Dystrophy Association (MDA) Conference and represent the first safety, pharmacodynamic, and efficacy data from patients treated in the ongoing Phase 1b/2 clinical trial.

The study is being conducted at the Powell Gene Therapy Center at the University of Florida, led by principal investigator Dr. Barry Byrne. To date, four patients have received the investigational AAV gene therapy, which delivers a functional copy of the SGCG gene responsible for producing the γ-sarcoglycan protein.

Nine-month follow-up data from the first two treated patients demonstrated a strong biological response to the therapy. Muscle biopsies performed six months after treatment showed that over 90% of muscle fibers expressed the γ-sarcoglycan protein, indicating successful delivery and expression of the therapeutic gene across nearly all muscle fibers.

In addition to gene expression, the AAV gene therapy produced sustained reductions in creatine phosphokinase (CPK) levels, a key biomarker of muscle damage. Improvements in transaminase levels were also observed nine months after treatment, supporting the potential therapeutic effect of the gene therapy.

Researchers also reported early clinical benefits in functional assessments, including improvements in timed mobility tests among ambulatory patients. Importantly, no serious adverse events have been observed in the four patients treated so far, supporting the safety profile of the therapy in the early stages of the study.

The ongoing Phase 1b/2 trial (NCT05973630) is evaluating ATA-200 in children aged 6 to 13 years with LGMD-R5. The therapy is administered as a single intravenous infusion at a dose of 1.0×10¹⁴ vg/kg. ATA-200 uses an adeno-associated virus (AAV) vector to deliver a functional copy of the SGCG gene, enabling muscle cells to produce the missing γ-sarcoglycan protein.

LGMD-R5 is a severe inherited neuromuscular disease that typically begins in childhood and leads to progressive muscle weakness, loss of ambulation before adulthood, and potentially life-threatening respiratory and cardiac complications. Currently, no curative treatments exist, and patient care remains largely supportive.

ATA-200 has received Orphan Drug designation in both the United States and Europe, as well as Rare Pediatric Disease designation from the FDA, supporting its continued development as a potential disease-modifying AAV gene therapy for this rare muscular disorder.