Achieved primary endpoint with high statistical significance; 93% of patients achieved microdystrophin expression above 10% (pStatistically significant correlation between RGX-202 microdystrophin expression and functional improvement (NSAA n=9), supporting validity of surrogate endpoint
Well-tolerated, differentiated safety profile
Company preparing for potential accelerated approval in 2027
Webcast to be held at 8:00 a.m. ET today
May 14, 2026 -- REGENXBIO Inc. (Nasdaq: RGNX) announced positive topline and interim functional data from the pivotal Phase III portion of the Phase I/II/III AFFINITY DUCHENNE® trial of RGX-202, a potential best-in-class gene therapy for Duchenne Muscular Dystrophy. The trial met its primary endpoint with high statistical significance (p<0.0001), with 93% of participants reaching at least 10% microdystrophin expression at Week 12 (n=30). Additionally, RGX-202 demonstrated statistically significant correlation between microdystrophin expression and interim functional improvement.
"These topline results are exciting for the Duchenne community," said Pat Furlong, Founding President of Parent Project for Muscular Dystrophy. "For decades, our community has pushed for therapies that can change the trajectory of this disease, and today's news gives us renewed optimism. Our families cannot wait; regulatory flexibility for innovative medicines to treat rare disease remains an urgent priority. We applaud the dedication of the patients and families who participated in this research and look forward to continued progress toward delivering stronger futures for people with Duchenne."
"Duchenne muscular dystrophy is a rare, progressive neuromuscular disease characterized by worsening muscle weakness and loss of function, and there continues to be a critical unmet need for therapies that can reliably alter the course of the disease", said AFFINITY DUCHENNE principal investigator Aravindhan Veerapandiyan, M.D., Arkansas Children's Hospital. "It's encouraging to see robust microdystrophin expression, correlation with functional outcomes, and a manageable safety profile. These data give us hope and reinforce the potential of RGX-202 to positively impact disease progression in individuals with Duchenne."
"RGX-202 is the first gene therapy in development for Duchenne to demonstrate strong, statistically significant correlation between microdystrophin expression and functional improvement, a landmark distinction in the field," said Steve Pakola, M.D., Chief Medical Officer of REGENXBIO. "Today's topline results underscore how our novel construct and differentiated therapeutic approach support a favorable safety profile and potential clinical benefit, including in older patients where progressive decline is expected. These data support the potential of RGX-202 to become a best-in-class gene therapy for Duchenne patients."
The pivotal portion of the Phase I/II/III AFFINITY DUCHENNE trial evaluated RGX-202 at 2x1014 GC/kg in 31 ambulatory boys aged 1 year of age and older. Key topline interim results include safety (n=31), biomarker (n=30), and functional data (n=9 aged >4 years, 12 months post-treatment).1
More than 20 additional participants have been enrolled in the confirmatory trial of RGX-202 (n=30), and the Company expects to have completed dosing in all 60 patients across the pivotal and confirmatory trials by mid-year.
93% of participants achieved >10% RGX-202 microdystrophin expression at Week 12 (pMicrodystrophin expression averaged 71.1% across all participants, and 41.6% in older boys, aged >8 years. Additionally, 80% of participants achieved >40% microdystrophin expression.
RGX-202 was appropriately localized to the sarcolemma, demonstrating that the differentiated construct with the inclusion of the C-Terminal (CT) domain is appropriately targeting the muscle. Additionally, robust vector copies per nucleus and percent positive fibers observed support the potential for sustained microdystrophin expression.
Duchenne is a severe, progressive, degenerative muscle disease, affecting 1 in 3,500 to 5,000 boys born each year worldwide. Duchenne is caused by mutations in the Duchenne gene which encodes for dystrophin, a protein involved in muscle cell structure and signaling pathways. Without dystrophin, muscles throughout the body degenerate and become weak, eventually leading to loss of movement and independence, required support for breathing, cardiomyopathy and premature death.
REGENXBIO is a biotechnology company on a mission to improve lives through the curative potential of gene therapy. Since its founding in 2009, REGENXBIO has pioneered the field of AAV gene therapy. REGENXBIO is advancing a late-stage pipeline of one-time treatments for rare and retinal diseases, including RGX-202 for the treatment of Duchenne; clemidsogene lanparvovec (RGX-121) for the treatment of MPS II and RGX-111 for the treatment of MPS I, both in partnership with Nippon Shinyaku; and surabgene lomparvovec (ABBV-RGX-314) for the treatment of wet AMD and diabetic retinopathy, in collaboration with AbbVie. Thousands of patients have been treated with REGENXBIO's AAV platform, including those receiving Novartis' ZOLGENSMA®. REGENXBIO's investigational gene therapies have the potential to change the way healthcare is delivered for millions of people.
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