A Gene Transfer Therapy to Evaluate the Safety and Efficacy of Delandistrogene Moxeparvovec (SRP-9001) Following Therapeutic Plasma Exchange (Plasmapheresis) in Participants With Duchenne Muscular Dystrophy (DMD) and Pre-existing Antibodies to AAVrh74

Inclusion Criteria:

• Ambulatory per protocol specified criteria.

• Has a definitive diagnosis of DMD prior to Screening based on documentation ofclinical findings and prior confirmatory genetic testing.

• Ability to cooperate with motor assessment testing.

• Has elevated AAVrh74 antibody titers per protocol-specified requirements.

• A pathogenic frameshift mutation, nonsense mutation or premature stop codon orpathogenic variant in the DMD gene that is expected to lead to absence of dystrophinprotein with exception of a mutation in exon 8 and/or 9.

• Stable daily dose of oral corticosteroids for at least 12 weeks prior to Screening,and the dose is expected to remain constant throughout the study (except formodifications to accommodate changes in weight).

Exclusion Criteria:

• Has reduced left ventricular ejection fraction on the screening ECHO or clinicalsigns and/or symptoms of cardiomyopathy.

• Presence of any other clinically significant illness, including cardiac, pulmonary,hepatic, renal, hematologic, immunologic, or behavioral disease, or infection ormalignancy or concomitant illness or requirement for chronic drug treatment that inthe opinion of the Investigator creates unnecessary risks for gene transfer or amedical condition or extenuating circumstance that, in the opinion of theInvestigator, might compromise the participant's ability to comply with the protocolrequired testing or procedures or compromise the participant's wellbeing, safety, orclinical interpretability.

• Exposure to gene therapy, investigational medication, or other protocol-specifiedtreatment within the protocol specified time limits.

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

Note: Other inclusion or exclusion criteria could apply.