SB939 is a potent histone deacetylase (HDAC) inhibitor used primarily in cancer research and therapy. It demonstrates strong antiproliferative effects in various tumor cell lines by inducing cell cycle arrest, apoptosis, and differentiation. Its ability to cross the blood-brain barrier makes it particularly valuable in studies involving central nervous system malignancies. SB939 enhances the efficacy of other anticancer agents when used in combination therapies, especially with DNA-damaging drugs or radiation, by increasing chromatin accessibility and promoting gene re-expression. It has shown promising results in preclinical models of hematological cancers such as leukemia and lymphoma, as well as solid tumors including breast and lung cancer. Due to its favorable pharmacokinetic profile and oral bioavailability, SB939 has advanced into clinical trials for evaluating its safety and effectiveness in treating advanced malignancies.