Dyne Therapeutics has announced positive topline results from its Registrational Expansion Cohort (REC) of the Phase 1/2 DELIVER trial of zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251) in people living with Duchenne who are amenable to exon 51 skipping. Z-rostudirsen is an exon skipping product designed to enable targeted muscle tissue delivery and promote exon skipping, allowing muscle cells to create a truncated, functional dystrophin protein.

According to Dyne, the REC met its primary endpoint, demonstrating a statistically significant increase in dystrophin protein expression compared to baseline at six months. Additionally, functional improvement relative to baseline, compared with declines in the pooled placebo (all cohorts), at six months was seen across all six endpoints, evaluating both upper and lower limb function as well as lung function. 

Dyne also announced new positive long-term clinical data from the ongoing open-label extension (OLE) and long-term extension (LTE) portions of DELIVER. Results indicate sustained improvement in upper and lower limb and pulmonary function from baseline through 18 and 24 months for participants (n=12) in the multiple ascending dose (MAD) cohort who were escalated to 20mg/kg or initially dose at 20mg/kg .

According to Dyne, the company plans to submit a BLA (Biologics License Application) for accelerated approval in the U.S. Q2 2026, and expects a potential U.S. launch of z-rostudirsen in early 2027, assuming the U.S. Food and Drug Agency (FDA) grants Priority Review. A global Phase 3 clinical trial of z-rostudirsen is anticipated in Q2 2026, and Dyne continues to pursue approval pathways outside of the U.S. for z-rostudirsen.

PPMD is pleased to learn this news from Dyne. Evidence of sustained functional improvement across multiple measures is promising, and continued improvements over 18–24 months are especially meaningful for individuals living with Duchenne and their families, as maintaining function over time significantly impacts independence and quality of life.

We look forward to further updates from Dyne and will share any additional information with the community as it becomes available.

Read Dyne’s press release here.