REGENXBIO INITIATES PIVOTAL PHASE OF AFFINITY DUCHENNE® TRIAL OF RGX-202 GENE THERAPY AND REPORTS POSITIVE FUNCTIONAL DATA

Core Insights - REGENXBIO Inc. has achieved alignment with the FDA on the AFFINITY DUCHENNE® pivotal program for RGX-202, a gene therapy for Duchenne muscular dystrophy, with a Biologics License Application (BLA) expected in 2026 [1][2] - The pivotal trial has commenced, enrolling ambulatory patients aged 1 and above, with the first patient already dosed [1][2] - Positive Phase I/II data indicate that RGX-202 recipients are exceeding external natural history benchmarks for clinical outcomes, showing functional improvements at both dose levels [1][3][4] Functional Data - Positive functional results were reported from the first five participants in the Phase I/II trial, with 12-month data from three patients at dose level 1 and nine-month data from two patients at dose level 2 [3][4] - All five participants demonstrated stable or improved function on the North Star Ambulatory Assessment (NSAA) and timed function tests, outperforming external natural history controls [4][5] Pivotal Dose Functional Data - Participants at the pivotal dose level showed a mean NSAA score improvement of 5.5 points at nine months, exceeding external natural history controls [5] - Dose level 1 participants also demonstrated improved performance, surpassing minimal clinically important difference (MCID) benchmarks at 12 months [5] Biomarker Data - New biomarker data confirms high expression and localization of RGX-202 microdystrophin in muscle tissue, with levels reported as the highest across approved or investigational gene therapies [6][7] - RGX-202 microdystrophin expression results in ambulatory patients aged 8 and above show significant levels, indicating effective targeting of muscle [6][7] Safety and Tolerability Data - As of November 1, 2024, RGX-202 has shown a favorable safety profile with no serious adverse events or adverse events of special interest reported [7][8] - Common drug-related adverse events included nausea, vomiting, and fatigue, all of which resolved and are typical for gene therapy administration [7][8] Pivotal Study Design - The pivotal trial is designed to support a BLA submission using the accelerated approval pathway, with a primary endpoint focused on microdystrophin expression and secondary endpoints on functional tests [11][12] - The trial will evaluate approximately 30 ambulatory patients aged 1 and older, with specific assessments for younger patients [11][12]