Study of Safety, Tolerability and Efficacy of GB221 in Infants With Spinal Muscular Atrophy Type 1

Inclusion criteria

• Symptomatic Participants

• Diagnosis of SMA Type 1 based on gene mutation analysis with bi-allelic SMN1 mutations (deletion or point mutations) and up to 3 copies of SMN2
• Participants must be 2 weeks to < 12 months of age at the time of dosing with disease onset of during the first 6 months of life.
• Presymptomatic Participants

• At risk of SMA Type 1 based on gene mutation analysis with bi-allelic SMN1 mutations (deletion or point mutations) and up to 2 copies of SMN2
• Participants must be 2 weeks to < 5 months (< 150 days) of age at the time of dosing.

Exclusion criteria

• Any suspected or confirmed active viral infection at screening baseline (including HIV, Hepatitis B or C, or human T Cell lymphotropic viruses [HTLV])
• History of invasive ventilatory support (tracheotomy with positive pressure) or pulse oximetry <95% saturation.
• Ongoing immunosuppressive therapy or immunosuppressive therapy within 3 months of starting the trial (e.g. corticosteroids, cyclosporine, tacrolimus, methotrexate, cyclophosphamide, intravenous immunoglobulin, rituximab)
• Participation in a recent SMA treatment clinical trial that, in the opinion of the Investigator, creates unnecessary risks for gene transfer.
• Prior history of gene therapy for any indication, hematopoietic transplant or solid organ transplant
• Subjects with severe scoliosis
• Known allergy or hypersensitivity to prednisolone or other glucocorticosteroids or their excipients.