A Study of PGN-EDO51 or Placebo in People With Duchenne Muscular Dystrophy Amenable to Exon 51-Skipping Treatment

The study consists of 3 periods: A Screening Period (up to 45 days), a double-blind, placebo-controlled Multiple Ascending Dose (MAD) Period (28 weeks), and a Long-Term Extension (LTE) Period (108 weeks). The primary purpose of the MAD period is to evaluate the safety and tolerability and levels of dystrophin after multiple ascending intravenous (IV) doses of PGN-EDO51 administered to participants with Duchenne muscular dystrophy (DMD). During the MAD period, participants will be randomized to either receive PGN-EDO51 or placebo in a 3:1 fashion, meaning that participants have a 75% chance of receiving PGN-EDO51 and a 25% chance of receiving placebo during this period. The primary purpose of the open-label LTE period is to evaluate the long-term safety and tolerability of PGN-EDO51 in participants who have completed the MAD period. All participants who roll-over into the LTE will receive PGN-EDO51 (no placebo in the LTE).