Metachromatic Leukodystrophy (MLD)
https://www.jci.org/articles/view/185001
Metachromatic leukodystrophy (MLD) is a rare, inherited neurodegenerative disorder caused by harmful changes in the ARSA gene. This gene normally makes an enzyme called arylsulfatase A (ARSA), which is essential for breaking down fatty molecules known as sulfatides. Without enough ARSA, sulfatides accumulate in the brain, spinal cord, and peripheral nerves. Over time, this build-up destroys the protective myelin coating around nerve cells, leading to loss of movement, speech, learning abilities, and eventually shortened life expectancy. At present, the current approved therapy is atidarsagene autotemcel, a stem-cell gene therapy that replaces the faulty ARSA gene in blood stem cells. However, this treatment can only be given before symptoms appear, leaving very few families eligible. For most children and adults affected by MLD, there is still a considerable unmet need for treatment options. In this study, researchers developed a new experimental treatment called AAV.GMU01 gene therapy. This approach uses an adeno-associated virus (AAV) to carry a healthy copy of the ARSA gene directly into the nervous system. In mouse models of MLD, the therapy successfully restored ARSA enzyme activity, reduced sulfatide accumulation, and improved brain health and nerve function, including hearing. Encouragingly, these benefits were sustained over time. Safety tests in non-human primates (rhesus macaques) showed the treatment was well tolerated and distributed widely throughout the brain and spinal cord. Importantly, ARSA enzyme levels matched or even exceeded those seen in healthy individuals. These results provide compelling preclinical evidence that AAV.GMU01 could become a one-time treatment, offering real hope for families living with MLD.