A Gene Delivery Study to Evaluate the Safety and Expression of Elevidys in Participants Under the Age of Four With Duchenne Muscular Dystrophy (DMD) (ENVOL)

Receiving regular oral corticosteroids as a treatment for DMD or planning to receive oral corticosteroids as a treatment for DMD within 1 year of baseline

• Cohort A: >=3 years of age to <4 years of age
• Cohort B: >=2 years of age to <3 years of age
• Able to cooperate with age-appropriate motor assessment testing
• A pathogenic frameshift mutation or premature stop codon contained between exons 18 and 79 (inclusive)

• Exposure to gene therapy, investigational medication, or any treatment designed to increase dystrophin expression, within protocol-specified time limits
• Recombinant Adeno-Associated Virus Serotype rh74 (rAArh74) antibody titers are elevated, as per protocol-specified criteria
• Presence of any other clinically significant illness, medical condition, or requirement for chronic drug treatment that in the opinion of the Investigator creates unnecessary risk for gene transfer
• Medical condition or extenuating circumstance that, in the opinion of the investigator, might compromise the participant's ability to comply with the protocol required testing or procedures, or compromise the participant's well-being or safety, or clinical interpretability