Treatment of cerebral adrenoleukodystrophy: allogeneic transplantation and lentiviral gene therapy

Introduction Adrenoleukodystrophy (ALD) is an X-linked peroxisomal disorder with an incidence of 1 in 14-17,000 male births, caused by pathogenic variants within the ABCD1 gene. By adulthood, approximately 40% of the patients develop cerebral ALD, a severe, neuroinflammatory condition that is generally progressive and fatal without intervention. Areas covered Historically, only allogeneic hematopoietic stem cell transplantation (HSCT) has been shown to halt progression of cerebral ALD, with superior outcomes obtained when HSCT is performed early in the disease process. More recently, a lentiviral-based gene therapy approach has been investigated as therapy for cerebral ALD as an alternative to allogeneic transplantation. A focused literature review was performed using the terms 'hematopoietic stem cell transplantation,' 'gene therapy' and 'adrenoleukodystrophy' to include relevant literature, especially comparing the experience with gene therapy and HSCT outcomes. We review the history and experience with HSCT in cerebral ALD and its limitations, as well as the information currently available in association with the gene therapy trials for cerebral ALD. Expert opinion The data regarding this lentiviral-based gene therapy approach and its relative risks and benefits is still being evaluated. This information is explored in the context of the experience with allogeneic HSCT for cerebral ALD.