FDA Grants Breakthrough Status to Dyne’s Duchenne Drug DYNE-251

Dyne Therapeutics said the U.S. Food and Drug Administration has granted Breakthrough Therapy Designation to DYNE-251, the company’s lead investigational treatment for Duchenne muscular dystrophy (DMD) patients who can benefit from exon 51 skipping. The RNA-based therapy is designed to deliver phosphorodiamidate morpholino oligomers directly to muscle tissue by conjugating them to the company’s proprietary FORCE platform antibody. The designation gives Dyne access to more intensive FDA guidance, rolling review and potential priority review, potentially shortening the path to market. It was supported by interim data from the Phase I/II DELIVER study that showed dose-dependent functional improvement and near full-length dystrophin expression in treated patients. Duchenne is a rare, progressive and fatal neuromuscular disorder that affects roughly 13% of boys with mutations addressable by exon 51 skipping. Existing exon-skipping drugs require weekly intravenous infusions and have shown limited restoration of the dystrophin protein. Dyne believes its targeted delivery approach can enable monthly sub-cutaneous dosing and materially higher dystrophin levels. The announcement lifted Dyne’s shares about 6% in morning New York trading on Monday. Management said it will discuss the DELIVER trial design and regulatory path with the FDA in the coming months while continuing enrollment at additional dose levels.