This is a FIH, open-label, single-arm, and single-center exploratory clinical study of SPOT-03 administered via IV infusion for DMD patients. SPOT-03 is a muscle-targeted extracellular vesicles (EVs) loaded with full-length dystrophin nucleic acid. The targeting ability of SPOT-03 is conferred by molecular targeting peptides on the EVs membrane, enabling the delivery of dystrophin nucleic acid as a gene therapy product for DMD.

The study has two dose groups:

Group I: 4.0E+11 dystrophin nucleic acid copies/kg, administered 8 times Group II: 4.0E+11 dystrophin nucleic acid copies/kg, administered 32 times The study will have a Screening Period of 30 days, during which patients or their legal guardian written informed consent will be obtained before Screening assessments and eligibility will be determined. A total of 6 to 9 DMD patients aged 2 to less than 8 years will be enrolled in this study according to the inclusion criteria. Complete data from at least 3 subjects will be obtained for Group II. All subjects will begin oral tacrolimus (0.05-0.2 mg/kg/d, adjustable according to actual clinical conditions) 3 days before the initial administration of SPOT-03 (D-3) and, with the duration aligned to the treatment schedule: 4 weeks for Group I and 16 weeks for Group II. In group I, the first dose of SPOT-03 will be administered by intravenous infusion on D1, followed by twice a week administration (once every 4 days) for a total of 8 doses. In group II, the first dose of SPOT-03 will be administered by intravenous infusion on D1, followed by twice a week administration (once every 4 days) for a total of 32 doses.

After all subjects in the previous dose group have completed SPOT-03 administrations, the next dose group may proceed after the investigators and sponsors have discussed and determined that there are no serious adverse reactions related to the drug.

Safety tests and evaluations will be conducted for the patients during each administration and follow-up.