ROCKVILLE, Md., Jan. 28, 2026 /PRNewswire/ -- REGENXBIO Inc. (Nasdaq: RGNX) today announced that the U.S. Food and Drug Administration (FDA) placed a clinical hold on its investigational gene therapy, RGX- 111, for the treatment of MPS I, also known as Hurler syndrome, following preliminary analysis of a single case of neoplasm (intraventricular CNS tumor) in a participant treated in its Phase I/II study. The FDA also placed a clinical hold on RGX-121, for the treatment of MPS II, also known as Hunter Syndr ...