REGENXBIO Inc. (Nasdaq: RGNX), a US-based clinical-stage biotechnology company, announced on Friday positive interim data from the Phase I/II trial of RGX-111 to treat severe Mucopolysaccharidosis Type I (MPS I).

Data from the Phase I/II trial and single-patient Investigational New Drug (IND) application of RGX-111 were presented by Ray Wang, M.D., Campbell Foundation director of the Multidisciplinary Lysosomal Program, Division of Metabolic Disorders, CHOC Children's Hospital, Department of Pediatrics, University of California, Irvine, at the 19th Annual WORLDSymposium.

RGX-111 is an investigational one-time gene therapy designed to deliver the gene that encodes the IDUA enzyme using the AAV9 vector. RGX-111 is administered directly to the central nervous system (CNS). The primary endpoint of the trial is to evaluate the safety of RGX-111. Secondary and exploratory endpoints include biomarkers of IDUA enzyme activity in the cerebrospinal fluid (CSF), serum and urine, neurodevelopmental assessments, and caregiver reported outcomes. Patients were treated across two dose cohorts: 1.0x1010 genome copies per gram (GC/g) of brain mass (n=2) and 5.0x1010 GC/g of brain mass (n=6). In the single-patient IND for RGX-111, a severe MPS I patient was dosed with 1x1010 GC/g of brain mass.

REGENXBIO plans to continue having early and frequent communication with regulatory agencies about pathways to expedite the development of its neurodegenerative disease pipeline. In the first half of 2023, REGENXBIO expects to use its Manufacturing Innovation Center to produce RGX-111 commercial-scale cGMP material from its proprietary, high-yielding suspension-based manufacturing process, named NAVXPress.