Atamyo Therapeutics Doses First Three Pediatric Patients with AAV Gene Therapy ATA-200 for LGMD-R5

Évry, France and Boston, MA, February 3, 2026 — Atamyo Therapeutics and The Dion Foundation for Children with Rare Diseases announced the dosing of a third pediatric patient in the ongoing first-in-human Phase 1b/2 clinical trial of ATA-200, an investigational adeno-associated virus (AAV) gene replacement therapy for γ-sarcoglycan–related limb-girdle muscular dystrophy type 2C/R5 (LGMD-R5). The two organizations also confirmed an extension of their partnership to support continued financing of the dose-escalation study.

The Phase 1b/2 open-label trial (NCT05973630) is evaluating the safety, pharmacodynamics, efficacy, and immunogenicity of a single intravenous dose of ATA-200 in pediatric patients. The study is being conducted at the Powell Gene Therapy Center at the University of Florida, under the leadership of Dr. Barry Byrne, with first clinical results expected to be published in the coming months.

ATA-200 is an AAV-based gene therapy designed to deliver a functional copy of the human γ-sarcoglycan gene, addressing the underlying genetic cause of LGMD-R5. The disease is one of the most severe forms of limb-girdle muscular dystrophy, with childhood onset, progressive muscle weakness, early loss of ambulation, and frequent cardiac involvement, including dilated cardiomyopathy.

The expanded partnership with the Dion Foundation enables continued enrollment of U.S. pediatric patients and supports the advancement of ATA-200 as a potential disease-modifying AAV gene therapy. Preclinical studies demonstrated favorable tolerability and correction of disease biomarkers and functional deficits in animal models.

ATA-200 has received Orphan Drug Designation in both the United States and Europe, as well as Rare Pediatric Disease Designation from the U.S. Food and Drug Administration. The program is based on foundational research led by Isabelle Richard, Ph.D., Chief Scientific Officer of Atamyo and Research Director at CNRS, who heads the Progressive Muscular Dystrophies Laboratory at Genethon.