Dyne Therapeutics Receives Orphan Drug Designation in Japan for DYNE-251 in Duchenne Muscular Dystrophy
Tuesday, September 30, 2025
Dyne Therapeutics has received Orphan Drug designation in Japan for DYNE-251, an investigational therapy for individuals with Duchenne muscular dystrophy (DMD) who have mutations in the DMD gene amenable to exon 51 skipping.
Duchenne muscular dystrophy is a rare, progressive neuromuscular condition caused by mutations in the DMD gene, leading to an absence of dystrophin. It is the most common childhood-onset muscular dystrophy, affecting around 12,000 individuals in the United States and 16,000 in Europe. Symptoms usually begin between the ages of three and five and include muscle weakness that worsens over time, along with possible cognitive and behavioural challenges. Despite available treatments, there remains a strong need for therapies that provide meaningful functional improvement.
DYNE-251 is being studied in the global Phase 1/2 DELIVER trial, which is assessing its safety, tolerability and effectiveness. The trial has identified a registrational dose of 20 mg/kg given every four weeks. A registrational expansion cohort has been fully enrolled to support a potential Accelerated Approval application in the United States, with the main goal of measuring changes in dystrophin protein levels over six months.
The designation was granted by the Ministry of Health, Labour and Welfare (MHLW) and follows similar designations already received in the United States and Europe. In Japan, Orphan Drug status is given to treatments for rare diseases affecting fewer than 50,000 patients and where medical need remains high. Benefits include development subsidies and the possibility of up to 10 years of market exclusivity once approved.
DYNE-251 is designed to produce near full-length dystrophin in muscle and the central nervous system by combining a phosphorodiamidate morpholino oligomer (PMO) with an antigen-binding fragment targeting the transferrin receptor 1.
The therapy has already received Breakthrough Therapy, Fast Track and Rare Paediatric Disease designations from the US Food and Drug Administration (FDA), as well as Orphan Drug status from both the FDA and European Medicines Agency (EMA).
Source: globenewswire.com
