Histone deacetylases (HDACs) are enzymes that modulate histone function by removing acetyl groups from lysine residues, thereby playing crucial roles in regulating gene transcription and contributing to aberrant gene expression in various cancers.[29] HDAC inhibitors (HDACis) have become attractive targets for treating hematological or solid tumors in different phases of clinical trials.[30] Although several HDACis have been approved by the US Food and Drug Administration (FDA) for various cancer types, their efficacy as monotherapies has been modest. This evidence concerns the gene HDAC9 and cancer.