FDA Accepts sNDAs for Sarepta's AMONDYS 45 and VYONDYS 53, Targeting Traditional Approval in Duchenne

Sarepta Therapeutics announced today that the FDA has accepted for filing supplemental New Drug Applications (sNDAs) for casimersen (Amondys 45) and golodirsen (Vyondys 53), two exon-skipping therapies for Duchenne muscular dystrophy (DMD).¹ The agency has assigned a Prescription Drug User Fee Act (PDUFA) target action date of February 28, 2027.¹ The filings mark the latest development in Sarepta's broader effort to solidify the regulatory standing of its exon-skipping portfolio, which has anchored the company's position in DMD for nearly a decade.

What are Amondys 45 and Vyondys 53 seeking to achieve with this filing?

The sNDA submissions seek to convert the existing accelerated approvals of Amondys 45 and Vyondys 53 to traditional, full approvals.¹ Both therapies currently hold accelerated approval based on the surrogate endpoint of increased dystrophin production in skeletal muscle; conversion to traditional approval would remove the requirement for ongoing confirmatory verification and solidify their long-term market status.

The applications draw on two evidence sources: data from the Phase 3 ESSENCE confirmatory study, and a substantial body of published real-world evidence accumulated since the therapies' original approvals.¹ Both drugs use Sarepta's proprietary phosphorodiamidate morpholino oligomer (PMO) chemistry, an antisense technology that binds to dystrophin pre-mRNA and induces exon skipping — allowing production of an internally truncated, partially functional dystrophin protein in patients with amenable mutations.¹

What did the ESSENCE trial show?

In the Phase 3 ESSENCE study evaluating Amondys 45 and Vyondys 53 against placebo, the primary endpoint was not met, though numerical trends favored treatment.¹ Sarepta conducted additional post-hoc analyses to account for heterogeneity in DMD disease progression and the confounding impact of running the trial during the COVID-19 pandemic. At week 96, treatment was associated with increased dystrophin expression and a consistent reduction in decline on the 4-step ascend test across multiple analyses, with no new safety signals observed over 144 weeks.¹

The sNDA filings lean heavily on supplementary real-world data to bolster the ESSENCE findings. Published real-world studies cited by Sarepta indicate that Vyondys 53 treatment is associated with a 7.5-year delay in the need for nighttime ventilation, while Amondys 45 treatment is associated with a statistically significant slowing of lung function decline and a potentially meaningful delay in time to cough-assist device use.¹ Across Sarepta's broader PMO portfolio, real-world evidence also points to multi-year survival benefits, delays of three to four years in time to loss of ambulation, and a substantial reduction in the risk of declining left ventricular ejection fraction.¹,²

Why does real-world evidence matter so much in this filing?

DMD exon-skipping therapies serve genetically defined, ultra-rare subpopulations — exon 45 and exon 53 mutations are each estimated to affect roughly 8% to 9% of the overall DMD population.³ That fragmentation makes traditional randomized confirmatory trials difficult to power adequately, a challenge Sarepta's leadership emphasized directly.

"Within Duchenne, each amenable mutation defines an ultra-rare population — a small subset of an already rare disease," said Louise Rodino-Klapac, PhD, president of research and development and technical operations at Sarepta. "Across our exon skipping therapies, more than 1,800 people worldwide have been treated, and we continue to observe preservation of muscle function and slowed disease progression. In populations this small and in a disease where damage unfolds over years, real-world experience is essential to understanding how these therapies impact the disease course."¹

The FDA's willingness to weigh real-world evidence alongside trial data reflects an evolving regulatory posture toward ultra-rare disease populations, an approach also visible in the agency's recent clearance of Sarepta's in-vivo gene editing program PBGENE-DMD for patients with exon 45-55 mutations.

What does the patient advocacy community say about this filing?

Patient advocacy groups have closely tracked Sarepta's regulatory pathway given the rarity and severity of DMD. "We appreciate the FDA's continued willingness to apply regulatory adaptability in addressing the unique challenges of rare disease drug development," said Pat Furlong, president and founder of Parent Project Muscular Dystrophy. "The acceptance of these supplemental applications for review reflects both the progress the Duchenne community has made over the past several years and the needs that remain, while maintaining a commitment to evaluating therapies with rigor."¹

"Within Duchenne, each amenable mutation defines an ultra-rare population — a small subset of an already rare disease... we continue to observe preservation of muscle function and slowed disease progression."

—Louise Rodino-Klapac, PhD, President of R&D and Technical Operations, Sarepta Therapeutics¹

References

1. Sarepta Therapeutics, Inc. Sarepta Announces FDA Acceptance of sNDAs for AMONDYS 45® and VYONDYS 53®. (2026 Jun 30). Business Wire. https://www.businesswire.com/news/home/20260630779541/en/Sarepta-Announces-FDA-Acceptance-of-sNDAs-for-AMONDYS-45-and-VYONDYS-53
2. Iff J, et al. (2024 Jul). Survival among patients receiving eteplirsen for up to 8 years for the treatment of Duchenne muscular dystrophy and contextualization with natural history controls. Muscle Nerve. https://pubmed.ncbi.nlm.nih.gov/38482981/
3. FDA grants accelerated approval to first targeted treatment for rare Duchenne muscular dystrophy mutation. (2021 Feb 25). U.S. Food and Drug Administration. https://www.fda.gov/news-events/press-announcements/fda-grants-accelerated-approval-first-targeted-treatment-rare-duchenne-muscular-dystrophy-mutation
4. Confirmatory Study With Casimersen and Golodirsen in Ambulatory and Non-Ambulatory Participants With DMD (ESSENCE). ClinicalTrials.gov. NCT02500381. https://clinicaltrials.gov/study/NCT02500381
5. Mendell JR, et al. (2013 Nov). Eteplirsen for the treatment of Duchenne muscular dystrophy. Ann Neurol. https://pubmed.ncbi.nlm.nih.gov/23907995/