Atamyo Therapeutics, which specialises in the development of gene therapies for limb-girdle muscular dystrophy (LGMD), has announced the first safety, pharmacodynamics, and efficacy results for its ATA-200 gene therapy in LGMD-2C/R5 limb-girdle muscular dystrophy associated with γ-sarcoglycan deficiency (SGCG, gamma-sarcoglycanopathy).
The results, from the first patients treated in the clinical trial conducted at the Powell Gene Therapy Center, were presented at the ASGCT (American Society of Gene and Cell Therapy) Annual meeting 2026.
LGMD-2C/R5 is a severe form of muscular dystrophy that appears in childhood and causes loss of walking ability before adulthood, respiratory and heart failure, and premature death. The phase 1b/2 clinical trial is a single-centre study evaluating the safety, pharmacodynamics, efficacy, and immunogenicity of ATA-200 in children aged six to 13 years. ATA-200 is an adeno-associated virus (AAV) gene therapy carrying a normal copy of the human SGCG gene and administered as a single intravenous injection at a dose of 1.0E+14 vg/kg. The gene therapy product was developed by Isabelle Richard, a pioneer in the study of limb-girdle muscular dystrophies and the development of innovative therapies at Genethon.
At a dose of 1.0E+14 vg/kg, the first two patients treated with ATA-200 had more than 90% of muscle fibres expressing the SGCG protein, demonstrating that almost all muscle fibres express the therapeutic gene (90.2% for patient 1 and 92.1% for patient 2, biopsies at 6 months).
A significant and sustained reduction in CPK levels (a biomarker of muscle damage) and a decrease in transaminases 12 months after treatment was seen, showing the significant efficacy of ATA-200 gene therapy.
Also, 12 months post-treatment, clinical benefits were observed on several other important parameters in ambulatory patients, particularly in timed functional tests.
No serious side effects were observed in the four patients treated.
“These initial results are very encouraging and demonstrate the potential of our product with biological data rarely seen in neuromuscular diseases and at such an early stage of the trial. I would like to commend the quality of the work done by the teams at Atamyo Therapeutics and, in particular, the commitment and determination of Isabelle Richard, which has made it possible to offer this hope to patients and their families. We are deeply grateful for the support of the Dion Foundation and Cure SCG as well as our collaboration with Dr. Barry Byrne of the Powell Gene Therapy Center and proud to offer children with LGMD-R5 the opportunity to receive a treatment that could change their lives,” said Angela Columbano, CEO, Atamyo Therapeutics.
Further results from the ongoing study are expected to be published in the coming months, when new longer-term follow-up data becomes available.