The purpose of ATA-003-GSAR study is to evaluate the safety and tolerability of a single intravenous infusion of ATA-200 in pediatric patients with limb girdle muscular dystrophy type 2c/R5 (LGMD R5).

This is a multicenter Phase 1b assessing the safety and tolerability of intravenous ATA-200 for the treatment of LGMDR5.

The study will enroll ambulant patients with LGMDR5. Patients will be enrolled sequentially and enrollment will be staggered with at least 4-week interval between 2 patient treatments. Patients will receive a potentially effective dose corresponding to the minimum effective dose (MED) in preclinical studies.

Time point of primary interest for safety evaluation and dose selection for future studies is at 6 months.

All subjects will be followed up for an additional 4.5 years after completion of the initial evaluation period.

Inclusion Criteria:

• Confirmed diagnosis of LGMDR5 before age of 10, based on clinical presentation and genotyping
• Ambulant male or female patients aged 6 to less than 12 years of age at screening
• Able to perform the 10-meter walk test (10MWT) in less than 15 sec and to rise from chair with or without arm support

Exclusion Criteria:

• Detectable neutralizing antibodies against AAV8
• Cardiomyopathy with left ventricular ejection fraction (LVEF) < 50%
• Respiratory assistance
• Concomitant medical condition that might interfere with LGMDR5 evolution
• Acute illness within 4 weeks of anticipated IMP administration
• Current participation in another clinical trial with investigational medicinal product
• Previous participation in gene and cell therapy trials
• Any condition that would contraindicate immunosuppressant treatment
• Presence of any permanent items (e.g., metal braces) precluding undergoing MRI
• Any vaccination 1 month prior to planned IMP administration
• Serology consistent with HIV exposure or active hepatitis B or C infection
• Grade 2 or higher lab abnormalities for liver function tests, creatinine, hemogram and coagulation