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 clinicalfindings 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 andhas 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 forat least 12 weeks before screening and the dose is expected to remain constant (except for modifications to accommodate changes in weight) throughout the firstyear of the study.

• Cohorts 4 and 6: Do not yet require use of chronic steroids for treatment of theirDMD, in the opinion of the Investigator, and are not receiving steroids at the timeof Screening.

• rAAVrh74 antibody titers are not elevated as per protocol-specified requirements.

• Genetic mutation inclusion criteria vary by cohort.

Exclusion Criteria:

• Has a concomitant illness, autoimmune disease, chronic drug treatment, and/orcognitive delay/impairment that in the opinion of the Investigator createsunnecessary risks for gene transfer.

• Exposure to gene therapy, investigational medication, or any treatment designed toincrease dystrophin expression within protocol-specified time limits.

• Abnormality in protocol-specified diagnostic evaluations or laboratory tests.

• Cohort 8: Any confounding factors that would prevent the use of oral sirolimusincluding a known hypersensitivity to sirolimus or any of its excipients.

Other inclusion/exclusion criteria apply.