OTL-200 in Patients With Late Juvenile Metachromatic Leukodystrophy (MLD)

Inclusion Criteria: All the following criteria need to be met: * Documented biochemical and molecular diagnosis of MLD, based on ARSA activity below the normal range and identification of two disease-causing ARSA alleles. Novel mutations will be analyzed with in silico prediction tools and excluded from being known common polymorphisms. In the case of a novel mutation(s), a 24-hour urine collection must show elevated sulfatide levels. * 0/R or R/R genotype or a genotype recognized as associated with the LJ variant of MLD. * a) If symptomatic: age at disease onset between ≥7 and \<17 years of age (i.e. before their 17th birthday). OR * b) If pre-symptomatic: participant must be \<17 years of age at treatment (i.e. before their 17th birthday) AND must have a sibling with a diagnosis of late-juvenile MLD variant based on age at disease onset (≥7 and \<17 years of age i.e. before sibling's 17th birthday), with biochemical and molecular diagnosis. * Normal cognitive function as defined by an IQ≥85 on age appropriate cognitive scales. * a) If the participant is \<7 years (i.e. before their 7th birthday): normal motor milestones achievement, normal gross motor function according to chronological age and normal neurological examination (if applicable based on the age of the subject, GMFC-MLD = 0) OR b) If participant is ≥7 years: normal gross motor function or mild gross motor function impairment, defined by a GMFC-MLD 0 or 1 (i.e. patient is able to walk independently). NOTE: The…