Inclusion Criteria:  Male subjects with either a confirmed diagnosis of AMN by genetic testing (mutation in the ATP binding cassette subfamily D (ABCD1 gene)) or a family history of X-linked adrenoleukodystrophy (ALD) together with an elevation in VLCFA obtained from overnight fasting plasma sample at Screening Visit (V1). Age: ≥ 18 to ≤ 65 years at informed consent signature. Normal brain magnetic resonance imaging (MRI) or brain MRI showing non-specific abnormalities that can be observed in AMN subjects without signs of cerebral form of ALD (C-ALD). MRI must be performed within 6 months prior to V2. If there is no available brain MRI within this period, a brain MRI must be performed before V2.  Exclusion Criteria:  Any progressive neurological disease other than AMN. Arrested or progressing C-ALD as defined by cerebral lesions (except for non-specific abnormalities that can be observed in AMN subjects). Prior receipt of an allogeneic hematopoietic stem cell transplant or gene therapy.