HDAC9 and ovarian cancer: Here, we demonstrated that the platinum(IV) complex, compound B, which has a cisplatin-core and two phenylbutyrate HDAC inhibitor axial ligands, not only causes reduced cell viability in ovarian cancer cell lines that are cisplatin-sensitive and -resistant, but at lower dosages than cisplatin, has comparable in vivo efficacy to reduce cisplatin-resistant ovarian cancer cell metastasis and general organismal toxicity.