Dyne Therapeutics is plotting an approval application for z-rostudirsen in the back half of 2026—a push that will only be bolstered by the departure of controversial CBER chief Vinay Prasad, according to analysts at Stifel.
Dyne Therapeutics’ investigational exon skipping therapy sustained its respiratory and heart benefits through two years of follow-up in a Phase 1/2 Duchenne muscular dystrophy study.
These long-term findings, Stifel told investors in a Monday note, “continue to support the strong profile of z-rostudirsen,” or zeleciment rostudirsen. Previously released data had already positioned the asset as a “highly competitive” therapy for patients with Duchenne who are amenable to exon 51 skipping, the analysts continued, and Dyne’s latest readout further builds on this profile.
“While these results are in small samples and compared to external controls, the cardiac endpoints in particular are unlikely to be influenced by bias, and altogether these data further support the benefit/risk of z-rostudirsen, which in our view already had a best-in-class profile,” Stifel wrote.
Dyne’s Duchenne data comes days after The Wall Street Journal reported that Vinay Prasad, director of the FDA’s Center for Biologics Evaluation and Rersearch, would be departing the agency. Prasad has been linked to a number of controversial FDA decisions, including one in November 2025 where the regulator changed its mind about uniQure’s Huntington’s disease gene therapy, saying that it “no longer agrees” that an externally-controlled study using natural history data would suffice for the drug application. Dyne employs a similar comparator group in its Phase 1/2 study of z-rostudirsen.
Dyne did not reveal specific data from the Phase 1/2 DELIVER study in its Monday news release, pointing instead to an upcoming presentation on Wednesday at the 2026 Muscular Dystrophy Association congress in Florida. But in summarizing the results, the company stated that z-rostudirsen maintained improvements in lung function, as measured by forced vital capacity, through 24 months of follow-up. Natural history data, which the biotech used as a comparator, showed that lung function is expected to deteriorate in untreated patients.
Aside from respiratory benefits, z-rostudirsen also sustained its cardiovascular effects through 24 months, Dyne said, including improvements in circumferential strain and left ventricular ejection fraction, measures of cardiac performance and the heart’s ability to pump, respectively. Both metrics declined over time in natural history controls.
As for safety, DELIVER provided up to 36 months of follow-up data and showed that z-rostudirsen’s profile remained favorable, with most treatment-emergent adverse events being mild or moderate in severity.
Monday’s findings add to a December 2025 readout from DELIVER, which found that a monthly dose of z-rostudirsen elicited mean dystrophin expression levels reaching 5.46% of normal—a level that Stifel analysts said at the time points to a “highly differentiated” efficacy profile.
Z-rostudirsen also elicited strong functional improvements, such as in the time-to-rise and 10-meter walk/run tests. And while DELIVER is not powered to determine the significance of these therapeutic effects, Stifel in December said that z-rostudirsen showed the “best ever” functional outcomes for a Duchenne exon skipper.
In November last year, this drug class suffered a blow when Sarepta Therapeutics’ Vyondys 53 and Amondys 54, both on the market under accelerated approval, failed to significantly improve motor function in the confirmatory Phase 3 ESSENCE study. Despite the miss, however, the company is continuing to seek full approval for the two assets.
Dyne said on Monday that it will build up to a regulatory submission for z-rostudirsen in the second half of 2026—plans that Stifel said will only be bolstered by Prasad’s upcoming exit. “We believe the departure of Dr. Vinay Prasad as Head of CBER should be a tailwind for DYN’s regulatory prospects,” Stifel wrote on Monday, particularly in Duchenne. “While there’s always uncertainty on the replacement, we expect someone friendlier on rare disease, given FDA/health policy will be in the spotlight for upcoming mid-term elections.”
