Regenxbio Inc. has announced positive results from the Phase I/II/III CAMPSIITE® trial of their gene therapy RGX-121 for treating Mucopolysaccharidosis Type II (MPS II), also known as Hunter syndrome. The trial data, presented at the International Congress of Inborn Errors of Metabolism (ICIEM) 2025, indicated that a one-time treatment with RGX-121 achieved over 80% reduction in cerebrospinal fluid $(CSF)$ levels of the HS D2S6 biomarker, sustained for one year. This reduction correlates with improvements in neurodevelopmental outcomes. Regenxbio has submitted these pivotal results to the U.S. Food and Drug Administration (FDA) as part of the ongoing Biologics License Application (BLA) review process. The FDA is expected to make a decision on the application by February 8, 2026.