OTL-200 is a cryopreserved dispersion for infusion containing autologous CD34+ cell enriched population that contains haematopoietic stem and progenitor cells (HSPC) transduced ex vivo using a lentiviral vector encoding the human arylsulfatase A (ARSA) gene. MLD is an autosomal recessive lysosomal storage disorder (LSD) characterized by severe and progressive demyelination affecting the central and peripheral nervous system. The aim of this clinical study is to assess the pharmacodynamic effect and long-term clinical efficacy and safety of OTL-200 in Late Juvenile MLD patients.