This thesis explores the role of histone deacetylase inhibitors (HDACis) as promising epigenetic therapies in cancer treatment. HDACis modulate gene expression by inhibiting histone deacetylases, leading to the reactivation of tumor suppressor genes, induction of apoptosis, and inhibition of cancer cell proliferation. While they have shown significant efficacy in hematologic malignancies, challenges such as drug resistance, off-target effects, and toxicity limit their broader application. The thesis highlights the potential of isoform-selective HDACis and combination therapies to enhance clinical outcomes and reduce adverse effects. Additionally, it discusses emerging applications of HDACis beyond oncology, including their roles in neurological disorders and personalized medicine. Overall, HDACis represent a transformative approach to targeting cancer’s epigenetic landscape, with ongoing research paving the way for more effective, tailored therapies.