REGENXBIO Presents Positive Twelve-Month Pivotal Data from Phase I/II/III CAMPSIITE® Trial of RGX-121 for Treatment of MPS II

Core Insights - REGENXBIO Inc. announced positive data from the Phase I/II/III CAMPSIITE trial for RGX-121, a treatment for Mucopolysaccharidosis Type II (MPS II), presented at the ICIEM 2025 [1][2] - The company submitted long-term pivotal results to the FDA as part of the ongoing Biologics License Application (BLA) review for RGX-121 [1] Data Summary - In the pivotal phase of the CAMPSIITE trial (n=13), participants showed an 82% median reduction in cerebrospinal fluid (CSF) levels of heparan sulfate (HS) D2S6, a key biomarker for MPS II, sustained over one year [3] - The primary endpoint of the trial was met with statistical significance (p < 0.0001) for the proportion of participants with CSF HS D2S6 below maximum attenuated levels at week 16 [3] - Positive neurodevelopmental outcomes were observed, with participants demonstrating skill acquisition or stability across all sub-scales of the Bayley Scales of Infant and Toddler Development at one year [4] Correlation and Biomarkers - Data from both the dose-finding and pivotal phases indicated a strong correlation between CSF HS D2S6 levels at week 16 and neurocognitive outcomes at one year, supporting its use as a surrogate endpoint for clinical benefit [5] - The buildup of glycosaminoglycans (GAGs) in MPS II correlates with clinical manifestations, including neurodevelopmental deficits [5][10] Regulatory Progress - The FDA completed a pre-license inspection for the RGX-121 BLA with no safety-related concerns raised, and the decision is expected by February 8, 2026 [6] - RGX-121 has received multiple designations from the FDA, including Orphan Drug Product and Fast Track [9] Product Overview - RGX-121 is a potential one-time AAV therapeutic designed to address the underlying genetic cause of Hunter syndrome, with over 80% reduction in CSF levels of HS D2S6 sustained through one year [7] - If approved, RGX-121 would be the first commercially available therapy targeting the genetic cause of Hunter syndrome [7] Company Background - REGENXBIO is a biotechnology company focused on gene therapy, with a late-stage pipeline including treatments for rare diseases [13] - The company has pioneered AAV gene therapy since its founding in 2009 and has treated thousands of patients with its AAV platform [13]