REGENXBIO reported positive Phase III AFFINITY DUCHENNE trial results for RGX-202, with 93% of evaluable Duchenne Muscular Dystrophy patients achieving significant microdystrophin expression and interim functional improvements supporting accelerated approval plans.
Written By: Farha Farheen, PharmD
Reviewed By: Pharmacally Editorial Team
REGENXBIO reported positive topline data from the pivotal Phase III portion of the AFFINITY DUCHENNE® trial (NCT05693142), supporting plans to pursue accelerated approval of RGX-202, an investigational gene therapy for Duchenne Muscular Dystrophy (DMD). The therapy is designed to deliver a differentiated microdystrophin construct that includes the C-Terminal (CT) domain, which may help preserve muscle function.
The latest findings build on REGENXBIO’s March 2026 interim update by adding pivotal Phase III evidence supporting accelerated approval of RGX-202
DMD is a rare, progressive X-linked neuromuscular disease marked by worsening muscle weakness, loss of mobility, cardiomyopathy, respiratory decline, and premature death. AFFINITY DUCHENNE principal investigator Aravindhan Veerapandiyan noted that there remains a critical unmet need for therapies capable of reliably altering disease progression, particularly in older boys with advancing disease.
The pivotal study evaluated a single intravenous dose of RGX-202 at 2 × 10¹⁴ GC/kg in 31 ambulatory boys aged one year and older. The trial met its primary endpoint with high statistical significance (p<0.0001), with 93% of evaluable participants achieving at least 10% microdystrophin expression at Week 12. Mean microdystrophin expression reached 71.1% across all participants and 41.6% in boys older than eight years. Additionally, 80% of participants exceeded 40% microdystrophin expression.
Researchers reported that RGX-202 microdystrophin appropriately localized to the sarcolemma, supporting effective muscle targeting. Steve Pakola, M.D., Chief Medical Officer of REGENXBIO said the differentiated construct and therapeutic approach support the therapy’s potential clinical benefit and favorable safety profile, including in older patients where progressive decline is expected.
Interim one-year functional data from nine participants aged approximately five to twelve years showed statistically significant improvements in North Star Ambulatory Assessment (NSAA) scores and timed function tests, including Time to Stand, 10-Meter Walk-Run, and Time to Climb, compared with external controls using propensity score weighting analysis. The study also demonstrated statistically significant correlations between Week 12 microdystrophin expression and one-year NSAA functional improvement. Pakola noted that RGX-202 is the first Duchenne gene therapy in development to demonstrate statistically significant correlation between microdystrophin expression and functional improvement.
RGX-202 was generally well tolerated with a manageable safety profile. Common treatment-related adverse events included vomiting, fatigue, and nausea, which were mostly mild to moderate and resolved without sequelae. Two serious adverse events were reported, including subacute myocarditis in an 8-year-old participant and asymptomatic liver injury in a 10-year-old participant. Both resolved within weeks following standard medical management.
Pat Furlong, Founding President of Parent Project for Muscular Dystrophy said the topline findings provide renewed optimism for Duchenne families and reinforce the importance of regulatory flexibility for innovative rare disease therapies.
REGENXBIO said recent FDA discussions indicated the agency would evaluate microdystrophin expression as a surrogate endpoint based on its correlation with clinical outcomes. The company expects to complete dosing across all 60 participants in the pivotal and confirmatory studies by mid-2026 and is preparing for a potential commercial launch in 2027.
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About the Writer
Farha Farheen, PharmD (LinkedIn) is a pharmacy professional with a strong interest in pharmacovigilance and clinical research. She has completed her Doctor of Pharmacy (Pharm.D) along with her internship as a Clinical Pharmacist. She has hands-on experience in adverse drug reaction (ADR) reporting, safety data documentation, and pharmacovigilance workflows, and is proficient in using VigiFlow. She is also a patent holder for an antibacterial formulation enriched with bioactive substances, granted by the German Patent and Trademark Office.