# Gene Therapy for Hunter Syndrome Hits Regulatory Wall: What the RGX-121 Rejection Means for Rare Disease Treatments - Date: 2026-03-16 - Category: Biotech & Life Sciences **Regenxbio's RGX-121 showed remarkable biomarker reduction in clinical trials, but the FDA isn't convinced that's enough** --- In November 2025, a three-year-old boy named Ollie made headlines when doctors at Manchester Children's Hospital described his response to an experimental gene therapy... ---