Patients & Families

Mucopolysaccharidosis Type II (MPS II)

Mucopolysaccharidosis Type II (MPS II), also known as Hunter syndrome, is a rare genetic disorder caused by mutation(s) in the gene that are responsible for making iduronate-2-sulfatase (IDS), an enzyme needed by cells to break down long chains of sugar molecules known as mucopolysaccharides.

These sugar molecules are cellular waste products. As they build up in tissues, like the central nervous system (CNS), they cause progressive damage to these tissues and to many organs in the body, including the brain.

In severe forms of MPS II, early developmental milestones in a child may be met, but delays become apparent by 18 to 24 months, with decline reported around six years of age. Children with MPS II may also show symptoms of severe behavioral effects. There remains a significant unmet medical need to prevent decline in cognition and other neurological aspects of the disease.

The Phase I/II/III CAMPSIITE™ trial of RGX-121 is enrolling patients. Learn more: NCT03566043

Our investigational therapy, RGX-121, is designed to use the AAV9 vector to deliver the IDS gene directly to the CNS. We believe that once the AAV9 vector delivers the gene to cells, the cells can begin making the needed IDS enzyme, potentially preventing the onset and/or further progression of cognitive deficits.

REGENXBIO has the following studies enrolling MPS II patients:

Phase I/II clinical trial of RGX-121 in children 4 months to 5 years old This study aims to determine whether RGX-121 is safe, well-tolerated and potentially effective in children over four months and under the age of five years with severe MPS II.
Learn more about this study: NCT03566043

Phase I/II clinical trial in children 5 years and older This study aims to determine whether RGX-121 is safe, well-tolerated, and potentially effective in children five years of age and over with severe MPS II.
Learn more about this study: NCT04571970