ROCKVILLE, Md., July 8, 2020 /PRNewswire/ -- REGENXBIO Inc. (Nasdaq: RGNX), a leading clinical-stage biotechnology company seeking to improve lives through the curative potential of gene therapy based on its proprietary NAV® Technology Platform, today announced that it has completed dosing of three patients in Cohort 2 of the Company's Phase I/II study of RGX-121 for the treatment of Mucopolysaccharidosis Type II (MPS II) and reported encouraging data under a single-patient investigator-initiated Investigational New Drug (IND) application for RGX-111 for the treatment of Mucopolysaccharidosis Type I (MPS I) conducted at CHOC Children's.