A Gene Transfer Therapy Study to Evaluate the Safety of and Expression From Delandistrogene Moxeparvovec (SRP-9001) in Participants With Duchenne Muscular Dystrophy (DMD)

Inclusion Criteria: * For Cohorts 1-8: Has a definitive diagnosis of DMD based on documented clinical findings and prior genetic testing. * Cohort 1: Is ambulatory, and ≥4 to \<8 years of age at the time of Screening. * Cohort 2: Is ambulatory, and ≥8 to \<18 years of age at the time of Screening. * Cohort 3: Non-ambulatory per protocol specified criteria at the time of Screening. * Cohort 4: Is ambulatory and ≥3 to \<4 years of age at the time of Screening. * Cohort 5a: Is ambulatory and ≥4 to \<9 years of age with time to rise from the floor ≤7 seconds at the screening visit. * Cohort 5b: Non-ambulatory per protocol specified criteria at the time of Screening. * Cohort 6: Is ambulatory, and ≥2 to \<3 years of age at the time of Screening. * Cohort 7: Non-ambulatory per protocol-specified criteria at the time of Screening. * Cohort 8: Non-ambulatory per protocol-specified criteria at the time of Screening, has a performance upper limb (PUL) entry item score ≥3 at the Screening visit and has a total PUL score of ≥20 and ≤40 at the time of Screening. * Ability to cooperate with motor assessment testing. * Cohorts 1, 2, 3, 5, 7 and 8 only: Stable dose equivalent of oral glucocorticoids for at least 12 weeks before screening and the dose is expected to remain constant (except for modifications to accommodate changes in weight) throughout the first year of the study. * Cohorts 4 and 6: Do not yet require use of chronic steroids for treatment of their DMD, in the opinion of the I…