EMA Grants Orphan Drug Status to Dyne's DYNE-251 for Duchenne Muscular Dystrophy

Dyne Therapeutics, Inc., a clinical-stage biotechnology company specializing in therapies for genetically driven neuromuscular diseases, has recently achieved a significant milestone with its investigational drug, DYNE-251. The European Commission has granted orphan drug designation to DYNE-251, a potential treatment for Duchenne muscular dystrophy (DMD), specifically targeting patients amenable to exon 51 skipping. This designation is a vital step forward for Dyne, allowing the company access to various regulatory benefits in the European Union, such as reduced fees, protocol assistance, research grants, and potentially up to a decade of market exclusivity upon approval.

DMD is a severe genetic disorder characterized by mutations that prevent the production of dystrophin, a protein essential for muscle function. This progressive condition predominantly affects males, with symptoms typically appearing in early childhood. As DMD advances, patients experience significant loss of muscle strength and function, often resulting in complete dependency on a wheelchair by their teens, accompanied by serious cardiac and respiratory complications. Despite the gravity of the condition, current treatments offer only limited relief, underscoring the urgency for more effective therapies.

The innovative approach of DYNE-251 involves a phosphorodiamidate morpholino oligomer (PMO) linked to an antibody fragment that targets the transferrin receptor 1, prevalent in muscle tissue. This design aims to deliver the therapeutic directly to muscle cells, facilitating exon skipping and promoting the production of a near full-length dystrophin protein. This process is intended to halt or even reverse the progression of DMD, offering new hope to patients and families affected by this debilitating disease.

The Phase 1/2 DELIVER clinical trial, assessing DYNE-251, has shown promising results. Presented at the 2025 Muscular Dystrophy Association Clinical & Scientific Conference, long-term data from the trial highlighted significant, sustained functional improvements over an 18-month period at the chosen registrational dose. The trial employs Stride Velocity 95th Centile (SV95C) as a primary endpoint, a recognized and objective digital metric for DMD trials in Europe. These findings suggest a viable path toward regulatory approval in the EU, as emphasized by Dr. Doug Kerr, Dyne's Chief Medical Officer. With the European Commission's orphan drug designation reinforcing the potential of DYNE-251, Dyne is poised to advance its regulatory submissions.

Furthermore, the DELIVER trial's registrational expansion cohort is fully enrolled, comprising 32 patients. This aspect of the trial is crucial for gathering the necessary data to support regulatory applications, with results expected by late 2025. Following this, Dyne plans to submit a Biologics License Application for accelerated approval in the United States in early 2026.

Dyne Therapeutics is not only focusing on DYNE-251 but is also expanding its DMD franchise to include preclinical programs targeting other exons, such as 53, 45, and 44. This strategic development is part of the company's broader mission to provide cutting-edge therapies for neuromuscular diseases using its FORCE™ platform. This platform is designed to deliver targeted therapeutics to muscle and central nervous system tissues, leveraging the platform's modularity for various applications. Dyne is concurrently advancing programs for myotonic dystrophy type 1 (DM1) and exploring solutions for facioscapulohumeral muscular dystrophy (FSHD) and Pompe disease.

In summary, the recent orphan drug designation for DYNE-251 marks a critical advancement in Dyne Therapeutics' efforts to combat Duchenne muscular dystrophy. Through ongoing trials and strategic expansion of their DMD programs, Dyne is setting the stage for potentially transformative therapies that could significantly improve the lives of those living with this challenging condition.