Experimental Gene Therapy Program for Hunter Syndrome (MPS II) Begins Expanding

According to a story from PR Newswire, the biotechnology company REGENXBIO Inc. has recently announced plans to expand its RGX-121 developmental program. RGX-121 is being developed as a potential one-time gene therapy treatment for mucopolysaccharidosis II (MPS II), also known as Hunter syndrome. They aim to further evaluate the treatment in a larger population of patients while gaining greater insight into the disorder’s neurodegenerative characteristics.

About Hunter Syndrome

Hunter syndrome, which is also known as mucopolysaccharidosis II (MPS II), is a rare lysosomal storage disease. This X-linked disorder is caused by mutations of the IPS gene and affects males almost exclusively. This mutation causes a deficiency of a certain enzyme which allows other substances to accumulate in the body and cause symptoms. These symptoms include ear infections, abdominal hernia, enlarged tongue, distinct facial features, developmental declines, joint stiffness, enlarged spleen and liver, heart problems, skin lesions, behavioral abnormalities, retinal degeneration, and hearing loss. Treatment for Hunter syndrome includes enzyme replacement therapy and bone marrow or stem cell transplantation; these treatments cannot address neurological symptoms. Research into gene therapy for this disease is also ongoing. There are around 2,000 people worldwide that are known to have the disorder. To learn more about Hunter syndrome, click here.

Planned Natural History Study

Gene therapy is often seen as the best possible option for Hunter syndrome and related diseases, as current treatment do not address some of the major, debilitating symptoms. The company is planning a natural history study as part of the expansion with the aim of getting a better handle on the cognitive development of patients. REGENXBIO says that the findings of this study would be freely available to advocates and the patient community. Enrollment is expected to begin before the end of the year. The study is expected to include around 40 patients between a month and eight years of age.

Ongoing Trial

Meanwhile, RGX-121 is being investigated in a phase 1/2 trial of severely affected patients that are less than five years old; six patients have so far been dosed, at two different dosages. The therapy appears well tolerated so far, with plans to dose six more patients. 

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