Hematopoietic Stem Cell Transplantation and Hematopoietic Stem Cell Gene Therapy in X‐Linked Adrenoleukodystrophy

Abstract Allogeneic hematopoietic stem cell transplantation (HSCT) is the only therapeutic approach that can arrest cerebral demyelination of X‐linked adrenoleukodystrophy (ALD) in boys and results in long‐term in a good quality of life, provided the procedure is performed at an early stage of disease. Similar benefits of allogeneic HSCT have been demonstrated in adults with cerebral ALD. However, it is not yet known whether allogeneic HSCT can prevent or rescue adrenomyeloneuropathy. Allogeneic HSCT remains associated with significant morbidity and mortality risks, particularly in adults, and not all ALD patients have donors despite the availability of cord blood. The absence of biological markers that can predict the evolutivity of cerebral disease is a major limitation to propose in due time allogeneic HSCT to ALD patients. Recently, HSC gene therapy using lentiviral vector was shown to have comparable efficacy than allogeneic HSCT in two boys with cerebral ALD who had no Human‐leukocyte‐antigen (HLA)‐matched donor. If these results are confirmed in an extended series of patients, HSC gene therapy may become the first therapeutic option for all ALD male patients who develop cerebral demyelination.