Furthermore, three different HDAC inhibitor clinical trials were approved by the Food and Drug Administration (FDA) for treating neurodegenerative disorders, including sodium phenylbutyrate for the treatment of HD (Clinical Trial NCT00212316) [76] and ALS (Clinical Trial NCT00107770) [66], and valproic acid for the treatment of SMA (Clinical Trial NCT00227266) [68]. This evidence concerns the gene HDAC9 and Huntington disease.