REGENXBIO's RGX-202 Achieves 93% Microdystrophin Expression, Eyes Accelerated 2027 Approval
REGENXBIO's Phase III AFFINITY DUCHENNE trial for RGX-202 met its primary endpoint (p<0.0001), with 93% of patients achieving over 10% microdystrophin expression at Week 12. Interim data reveal significant correlation with NSAA functional gains and a favorable safety profile, positioning the therapy for accelerated approval in 2027.
1. Trial Results Overview
The pivotal Phase III portion of the AFFINITY DUCHENNE trial evaluated RGX-202 at 2×10^14 GC/kg in 31 ambulatory boys and achieved its primary endpoint with 93% of participants exceeding 10% microdystrophin expression at Week 12 (p<0.0001). Dosing across pivotal and confirmatory cohorts reached 60 patients, with full enrollment expected by mid-year.
2. Biomarker and Functional Correlation
Microdystrophin expression averaged 71.1% across all participants and 41.6% in boys older than eight years, with 80% of patients surpassing 40% expression; protein localized correctly to the sarcolemma. Interim functional assessments in nine boys showed statistically significant improvements in North Star Ambulatory Assessment and timed function tests versus external controls.
3. Safety and Tolerability
RGX-202 was well tolerated, with mean liver inflammation markers (GGT, bilirubin) remaining within normal limits up to one year post-treatment (n=9). Two serious adverse events—a subacute myocarditis and an asymptomatic liver injury—were managed successfully and resolved without sequelae; common mild events included vomiting, fatigue and nausea.
4. Regulatory and Enrollment Update
Regulatory discussions have endorsed microdystrophin expression as a surrogate endpoint supporting potential accelerated approval in 2027, with external control data deemed sufficient for efficacy. REGENXBIO has scheduled a webcast and plans further meetings with the FDA to finalize confirmatory trial design and approval pathway.