Thus, several key considerations should be addressed when designing AAV-based gene therapy for X-ALD, including the genetic background of the disease and requisite transgene expression levels, the biochemical function of the adrenoleukodystrophy protein (ALDP), the identification of target cells and their role in pathogenesis, the regulation of expression within the genetic construct, the route of administration, the selection of an AAV serotype with high tropism for the central and peripheral nervous systems, and the development of robust in vitro and in vivo models. This evidence concerns the gene ABCD1 and X-linked adrenoleukodystrophy.