CD34 and metachromatic leukodystrophy: Transplantation of LV-modified CD34+ has been studied in animals model [85,88,89] and MLD patients [52,87,91], and the results of these studies have been presented in a number of publications by A. Biffi et al. In 2010, the first clinical trials of this approach were initiated (NCT01560182, NCT04283227, and NCT03392987), and after 10 years of productive research, the EMA approved Libmeldy, which contains autologous CD34+ cells encoding the ARSA gene, for the treatment of MLD.