Nonetheless, diseases for which a cure has been attempted include β-thalassemia, X-linked severe combined immunodeficiency (X-SCID), adenosine deaminase deficiency (ADA-SCID), cystic fibrosis, hemophilia, liver enzyme ornithine transcarbamylase (OTC) deficiency, head and neck cancer, metastatic melanoma, HIV, Leber's congenital amaurosis, Wiskott-Aldrich syndrome (WAS), metachromatic leukodystrophy (MLD), and severe lipoprotein lipase deficiency disorder (LPLD) (52, 71). This evidence concerns the gene ADA and metachromatic leukodystrophy.