Efficacy, Safety, and Tolerability of Zeleciment Rostudirsen (DYNE-251) Administered Intravenously Every 4 Weeks in Ambulatory Participants With Duchenne Muscular Dystrophy (FORZETTO)

Prior treatment

• Receipt of ongoing immunosuppressive therapy (other than glucocorticoids) within 12 weeks prior to randomization
• Use of any pharmacologic treatment (other than glucocorticoids) that may have an effect on muscle strength or function within 12 weeks prior to randomization
• Any change in prophylaxis/treatment for congestive heart failure (CHF) within 12 weeks prior to randomization
• Receipt of eteplirsen within 1 week prior to randomization
• Receipt of alternative exon-skipping or dystrophin-modifying therapy or zeleciment rostudirsen within 24 weeks prior to randomization
• Receipt of givinostat within 12 weeks prior to randomization
• Receipt of gene therapy at any time
  • Note: Other inclusion or exclusion criteria may apply

• Ambulatory male with confirmed diagnosis of DMD and with a mutation in the dystrophin gene characterized by exon deletion amenable to exon 51 skipping .
• Rise From Floor (RFF) time must be \< 10 seconds for both screening assessments .
• Receiving a stable daily or weekend dosage of glucocorticoids for at least 24 weeks prior to randomization with the expectation of maintaining a stable dose during the Placebo-Controlled Period of the study (unless dose adjustment is required by weight change)