May 14, 2026 —
Regenxbio reported that RGX-202, its investigational AAV-based gene therapy for Duchenne muscular dystrophy (DMD), met the primary endpoint in a pivotal Phase 3 trial, marking an important clinical milestone for the program. Twelve weeks after treatment, 28 of 30 patients achieved microdystrophin protein expression levels at or above 10% of healthy control, with average expression across all treated patients reaching 71.1%.
DMD is a severe, progressive neuromuscular disease caused by mutations in the dystrophin gene, resulting in little or no functional dystrophin protein. Because the dystrophin gene is too large to fit into standard AAV vectors, RGX-202 uses a shortened version of the gene to produce microdystrophin, a smaller protein designed to preserve key functional elements of dystrophin and support muscle integrity.
According to Regenxbio, RGX-202 showed high levels of microdystrophin expression, including in older ambulatory boys aged eight and above. The company also highlighted a potentially differentiated safety profile, reporting one case of severe liver injury among 31 treated patients. Liver toxicity has been a major concern for systemic AAV gene therapies in DMD, making safety and immune management important factors for future regulatory review and clinical adoption.
Regenxbio also reported evidence linking microdystrophin expression with functional benefit. In a subset of nine boys treated with RGX-202, improvements were observed across multiple measures of muscle function, including time to stand and time to run or walk, compared with expectations based on natural history data. The company believes the inclusion of key functional dystrophin domains, including the C-terminal domain, may contribute to the relationship between protein expression and clinical outcomes.
The results come at an important time for Regenxbio, following recent regulatory setbacks involving other gene therapy programs. The company is expected to engage regulators on a potential accelerated approval pathway for RGX-202, although the timing may depend on ongoing changes within FDA leadership. The program’s use of natural history comparators may also be an important regulatory discussion point, particularly as gene therapy developers continue to navigate trial design challenges in rare pediatric diseases.
Overall, the Phase 3 results position RGX-202 as a closely watched AAV microdystrophin gene therapy candidate in DMD. While longer-term durability, safety, and functional outcomes will remain critical, the reported protein expression data and early functional signals suggest RGX-202 could become an important competitor in the evolving DMD gene therapy landscape.
