This is a multicenter, prospective, observational Phase 4 study including a post marketing safety requirement, designed to collect both medical history data and prospective data on Duchenne muscular dystrophy (DMD) treatment outcomes in participants receiving delandistrogene moxeparvovec (ELEVIDYS) as part of clinical care, compared to participants with DMD receiving or prescribed to start chronic glucocorticoid treatment at the time of study enrollment in routine clinical practice.

Inclusion Criteria:

• Has an established clinical diagnosis of DMD based on documentation of clinical findings and prior confirmatory genetic testing using a clinical diagnostic genetic test.
• Is currently receiving or has been prescribed to start chronic glucocorticoid therapy at the time of this observational study enrollment.

For ELEVIDYS-treated Participants (Cohorts 1a, 1b, and 1c):

• Is at least 4 years of age at the time of infusion
• Will either: a) be initiating or has initiated ELEVIDYS within the last 30 days in routine clinical practice at the time of this observational study enrollment, or b) was administered ELEVIDYS in routine clinical practice and has the required minimum dataset for entry into the observational study per Sponsor approval

For Standard of Care Comparators (Cohort 2):

• Is at least 4 years of age at the time of enrollment
• Is unexposed to DMD gene therapy at the time of this observational study enrollment

Exclusion Criteria:

• Has any deletion of exon 8 and/or exon 9 in the DMD gene.

• Is currently participating in any DMD interventional study at the time of this observational study enrollment.

• Has any prior exposure to DMD gene therapy other than that described for Cohort 1c (ELEVIDYS Retrospectively Treated Cohort).

• Has a medical condition or confounding circumstances (for example, prior traumatic limitation for mobility or significant behavioral comorbidity) that, in the opinion of the Investigator, might compromise:

  • The participant's ability to comply with the protocol-required procedures,
  • The participant's wellbeing or safety, and/or
  • The clinical interpretability of the data collected from the participant.

Other inclusion/exclusion criteria may apply.

DMD participants within each prescriber's practice who either (1) have been prescribed delandistrogene moxeparvovec or (2) are receiving or have been prescribed to begin chronic glucocorticoid therapy in routine clinical practice, and who meet the study eligibility criteria, will be invited to enroll into the study and will be followed according to the protocol.