Dyne Therapeutics Reports Breakthrough Results for Duchenne Muscular Dystrophy Gene Therapy
Key Insights
Dyne Therapeutics' z-rostudirsen (search) achieved a statistically significant 5.46% dystrophin (search) expression in the Phase 1/2 DELIVER trial, representing a 7-fold increase from baseline in patients with Duchenne muscular dystrophy (search) amenable to exon 51 skipping.
The therapy demonstrated functional improvements across multiple clinical endpoints at 6 months, with sustained benefits observed through 24 months in long-term extension studies.
The company plans to submit for U.S. Accelerated Approval in Q2 2026, targeting a potential Q1 2027 launch for approximately 1,600 eligible patients with significant unmet medical needs.
Dyne Therapeutics announced positive topline results from the Registrational Expansion Cohort (REC) of its Phase 1/2 DELIVER trial evaluating zeleciment rostudirsen (search) (z-rostudirsen (search)) in individuals with Duchenne muscular dystrophy (search) (DMD (search)) amenable to exon 51 skipping. The trial met its primary endpoint, demonstrating a statistically significant increase in muscle content-adjusted dystrophin (search) expression to 5.46% of normal at six months (p<0.0001).
Primary Efficacy Results
The REC enrolled 32 ambulant and non-ambulant males with DMD (search) aged 4 to 16 at baseline, with 24 participants receiving 20 mg/kg z-rostudirsen (search) every four weeks and 8 receiving placebo. The therapy achieved a mean absolute dystrophin (search) expression of 5.46% of normal when adjusted for muscle content, replicating the 7-fold increase previously observed at the registrational dose.
When unadjusted for muscle content, the mean absolute dystrophin (search) expression was 2.87% of normal (p < 0.0001), approximately 10-fold higher than the 0.3% reported for eteplirsen, the current standard of care for DMD (search) exon 51 in the United States.
Functional Improvements Across Multiple Endpoints
Functional improvement was observed across all six prespecified clinical endpoints at six months. Two measures, Time to Rise (TTR) Velocity and 10-Meter Walk/Run (10MWR) Velocity, showed nominal statistical significance (p<0.05) compared to placebo, despite the study not being powered for formal functional comparisons.
Additional functional improvements were seen in Stride Velocity 95th Centile (SV95C) and Performance of Upper Limb (PUL2.0). Critically, lung function as measured by Forced Vital Capacity Percent Predicted (FVC%p) was preserved at 6 months compared to decline in placebo, addressing a leading cause of mortality in DMD (search).
Long-Term Durability Data
New long-term results from the DELIVER trial showed sustained functional improvement across all assessed endpoints through 24 months. The data included 24-month functional results from participants initially treated with 10 mg/kg who were dose-escalated to 20 mg/kg, and 18-month data from those who received 20 mg/kg from the start.
"The clinical results from DELIVER, taken together, are unprecedented in terms of the breadth, magnitude and duration of effect," said Doug Kerr, M.D., Ph.D., chief medical officer of Dyne.
Safety Profile
Z-rostudirsen (search) demonstrated a favorable safety profile across 86 participants followed for up to 36 months, representing 113 patient-years of follow-up. Most treatment-emergent adverse events were mild or moderate, with pyrexia (fever) and headache being the most commonly reported related events. No related serious adverse events were observed in the REC cohort.
Regulatory Timeline and Market Opportunity
Dyne plans to submit a Biologics License Application for U.S. Accelerated Approval in Q2 2026, with a potential Q1 2027 launch assuming Priority Review. The company will also initiate a global Phase 3 clinical trial in Q2 2026 to support worldwide approvals.
"With these unprecedented clinical data in hand, we are on track to submit for U.S. Accelerated Approval in Q2 2026, positioning us for a potential Q1 2027 launch into an established market of approximately 1,600 people with significant unmet need," said John Cox, president and CEO of Dyne.
Mechanism and Disease Context
Z-rostudirsen (search) consists of a phosphorodiamidate morpholino oligomer (PMO) conjugated to an antigen-binding fragment (Fab) that binds to the transferrin receptor 1 (search) (TfR1 (search)). It is designed to enable production of near full-length dystrophin (search) in muscle and the central nervous system.
Duchenne muscular dystrophy (search) is a rare X-linked progressive neuromuscular disorder affecting approximately 12,000 individuals in the U.S. and 16,000 in the EU. The disease is caused by mutations in the DMD gene (search) that result in complete or near-complete absence of dystrophin (search), a protein critical for maintaining muscle structure and function.
The therapy has received Breakthrough Therapy, Fast Track and Rare Pediatric Disease designations from the FDA, as well as Orphan Drug designation from the FDA, European Medicines Agency, and Japan's Ministry of Health, Labour and Welfare.
Perry Shieh, M.D., Ph.D., professor of neurology and pediatrics at UCLA and principal investigator for the DELIVER trial, noted: "The Duchenne community has long awaited therapies that deliver meaningful and sustained functional improvement. I am highly encouraged by these new results and look forward to being able to offer z-rostudirsen (search) to eligible DMD (search) patients, if approved."