Evaluation of Safety and Efficacy of Gene Therapy Drug in the Treatment of Spinal Muscular Atrophy (SMA) Type 3 Patients

Inclusion Criteria:

• ≥2 years of age on the day of signing the informed consent form;

• Genetic and clinical diagnosis of type 3 SMA with bi-allelic deletion of SMN1 of 5qSMA;

• Hammersmith Functional Motor Scale - Expanded (HFMSE) score is between 10 and 54 atscreening;

• Female patients of childbearing age who are pregnant or lactating, as well as allenrolled patients （both male and female), should take effective contraceptivemeasures within 6 months after the treatment;

• Patients or patient's legal guardian(s) must be able to understand the purpose andrisks of the study and voluntarily provide signed and dated informed consent priorto any study-related procedures being performed.

Exclusion Criteria:

• Patient who has participated in any previous gene therapy research trials;

• Patient who has AAV9 neutralizing antibody titer ≥1:200;

• Patient who has received Nusinersen within 120 days and Risdiplam within 15 daysbefore treatment;

• Patient who requires invasive or non-invasive ventilatory support averaging≥16hours/day at screening;

• SMN2 copy numbers >4；

• Patient who needs nasal or gastric tube feeding for eating;

• Patient who is positive for human immunodeficiency virus (HIV) antibody, hepatitis Bsurface antigen, hepatitis C antibody, or treponema pallidum antibody;

• Known allergy or hypersensitivity to prednisolone or other glucocorticosteroids ortheir excipients

• Severe contractures at screening that interfere with either the ability toattain/demonstrate functional measures or with the ability to receive intrathecal (IT) dosing;

• Patient who has other serious diseases, such as severe cardiovascular andcerebrovascular diseases, digestive system diseases, urinary system diseases,endocrine system diseases, hematological diseases, immune system diseases, nervoussystem diseases (including but not limited to epilepsy, meningitis, history ofconvulsions or seizures, cerebrospinal fluid circulation disorders), and mentalillnesses, etc.;

• Patient with previous injuries (such as upper or lower limb fractures) or surgicaloperations that have not fully recovered or reached a stable state;

• Vaccination no longer than 2 weeks before treatment;

• Patient who has any other condition that, in the opinion of the investigator, makesthe subject unsuitable for participation in the study.