Sarepta’s Duchenne Drugs AMONDYS 45 and VYONDYS 53 Advance Toward Full FDA Approval

The U.S. Food and Drug Administration has accepted supplemental New Drug Applications (sNDAs) for AMONDYS 45 (casimersen) and VYONDYS 53 (golodirsen), Sarepta Therapeutics’ exon-skipping therapies for Duchenne muscular dystrophy (DMD). The applications seek to convert the drugs’ accelerated approvals into traditional approvals. The FDA assigned a Prescription Drug User Fee Act target action date of February 28, 2027.

The submissions are supported by data from the Phase 3 ESSENCE confirmatory study (NCT02500381), published real-world evidence, and long-term safety data collected across Sarepta’s exon-skipping portfolio. If approved, the decision would reinforce the clinical evidence supporting these mutation-specific therapies for patients with DMD amenable to exon 45 or exon 53 skipping.

Exon-skipping therapy targets specific DMD mutations

Duchenne muscular dystrophy is a rare, progressive genetic disorder caused by mutations in the DMD gene that prevent production of functional dystrophin, a protein essential for maintaining muscle integrity. Progressive muscle degeneration ultimately leads to loss of ambulation, respiratory failure, cardiomyopathy, and premature death.

AMONDYS 45 and VYONDYS 53 use Sarepta’s phosphorodiamidate morpholino oligomer (PMO) technology to skip specific exons during dystrophin pre-mRNA processing. This approach restores the reading frame and enables production of a shortened but functional dystrophin protein in patients with mutations amenable to exon 45 or exon 53 skipping. Both therapies previously received accelerated approval based on increased dystrophin production in skeletal muscle.

ESSENCE study provides confirmatory evidence

The Phase 3 ESSENCE trial compared casimersen and golodirsen with placebo in patients with DMD. Although the study did not meet its primary endpoint, treatment consistently favored active therapy across multiple efficacy analyses.

Post-hoc analyses that accounted for disease progression variability and disruptions related to the COVID-19 pandemic showed increased dystrophin expression at Week 96 and consistent reductions in decline on the four-step stair climb assessment. Both therapies maintained favorable safety profiles through 144 weeks, with no new safety signals beyond those already established in clinical development and real-world practice.

Additional real-world evidence strengthened the submissions. Treatment with VYONDYS 53 has been associated with a 7.5-year delay in the need for nighttime ventilation, while AMONDYS 45 has shown statistically significant slowing of lung function decline and delayed need for cough-assist devices. Across Sarepta’s PMO portfolio, observational studies have also reported prolonged survival, delayed loss of ambulation, improved cardiac outcomes, and fewer hospitalizations.

Real-world evidence strengthens regulatory package

Sarepta said the applications combine confirmatory clinical trial findings with more than a decade of real-world experience treating over 1,800 patients worldwide. Company leadership noted that long-term observational data are particularly valuable in Duchenne because each exon-skipping therapy addresses an ultra-rare genetic subgroup, making large traditional trials challenging.

Parent Project Muscular Dystrophy also welcomed the FDA’s acceptance, emphasizing the importance of regulatory flexibility while maintaining rigorous evaluation standards for rare disease therapies.

Regulatory Path

The FDA will review both applications under the standard review timeline, with a decision expected by February 28, 2027. A positive outcome would convert AMONDYS 45 and VYONDYS 53 from accelerated to full FDA approval, providing stronger regulatory validation for Sarepta’s exon-skipping platform and expanding long-term confidence in these mutation-specific treatments for Duchenne muscular dystrophy.

Reference

Sarepta Announces FDA Acceptance of sNDAs for AMONDYS 45® and VYONDYS 53® | Sarepta Therapeutics, Inc.