WALTHAM, Mass., July 20, 2026
Dyne Therapeutics, Inc. (Nasdaq: DYN) announced that the U.S. Food and Drug Administration (FDA) has accepted the Biologics License Application (BLA) for zeleciment rostudirsen (z-rostudirsen, DYNE-251) for the treatment of Duchenne muscular dystrophy (DMD) patients amenable to exon 51 skipping. The FDA also granted Priority Review and assigned a Prescription Drug User Fee Act (PDUFA) target action date of January 21, 2027. The BLA seeks Accelerated Approval based on dystrophin production as a surrogate endpoint, supported by positive data from the registrational expansion cohort of the Phase 1/2 DELIVER trial. Dyne reported that patients receiving once-every-four-week dosing demonstrated a statistically significant increase in near-full-length dystrophin production, accompanied by functional improvements across multiple clinical endpoints and a favorable safety profile, positioning the therapy for a potential U.S. commercial launch in the first quarter of 2027, subject to FDA approval.
Priority Review Backed by Strong DELIVER Trial Results
The FDA’s acceptance of the BLA represents a significant regulatory milestone for z-rostudirsen, which is designed to restore production of near-full-length dystrophin, the critical protein missing in patients with Duchenne muscular dystrophy caused by mutations amenable to exon 51 skipping. The application is supported by results from the global Phase 1/2 DELIVER clinical trial, where the registrational expansion cohort successfully met its primary endpoint by demonstrating robust dystrophin restoration together with functional improvements across multiple measures of muscle performance. The therapy continues to be evaluated in the long-term extension portion of the DELIVER trial and the global Phase 3 FORZETTO confirmatory study, which is intended to verify clinical benefit following potential accelerated approval. The FDA’s Priority Review designation recognizes the potential of z-rostudirsen to provide a significant improvement for patients living with this serious, progressive neuromuscular disease.
Targeted Exon Skipping Technology Designed for Functional Improvement
Z-rostudirsen combines a phosphorodiamidate morpholino oligomer (PMO) with an antigen-binding fragment (Fab) that targets the transferrin receptor 1 (TfR1), enabling enhanced delivery into skeletal muscle and the central nervous system (CNS). This targeted delivery platform is designed to improve exon-skipping efficiency, increase dystrophin production, and ultimately deliver meaningful functional improvement for individuals with DMD amenable to exon 51 skipping. The investigational therapy has already received multiple regulatory incentives, including Breakthrough Therapy, Fast Track, Rare Pediatric Disease, and Orphan Drug Designations from the FDA, as well as Orphan Drug Designation from both the European Medicines Agency (EMA) and Japan’s Ministry of Health, Labour and Welfare, reflecting the significant unmet medical need in Duchenne muscular dystrophy.
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Dyne Builds Broad Duchenne Muscular Dystrophy Franchise
The FDA filing further strengthens Dyne Therapeutics’ strategy to build a comprehensive Duchenne muscular dystrophy franchise addressing multiple genetic mutations through its FORCE™ platform. Beyond z-rostudirsen, the company is advancing DYNE-253, DYNE-245, DYNE-244, and DYNE-255 for patients amenable to exon 53, exon 45, exon 44, and exon 55 skipping, respectively. Dyne is also developing therapies for myotonic dystrophy type 1 (DM1), facioscapulohumeral muscular dystrophy (FSHD), and Pompe disease, expanding its portfolio of targeted neuromuscular treatments. With FDA review now underway and a January 2027 PDUFA decision date, Dyne is preparing for commercialization while continuing to advance its pipeline of next-generation therapies designed to address the root causes of genetically driven muscle diseases.
Source: Dyne Therapeutics press release
