Belinostat is a hydroxamate-type histone deacetylase inhibitor indicated for the treatment of relapsed or refractory peripheal T-cell lymphoma. The compound received orphan drug designation for the treatment of malignant thymomas. Acting on a histone deacetylase Belinostat causes the accumulation of acetylated histones and other proteins, inducing cell cycle arrest and/or apoptosis of some transformed cells. Belinostat targets HDAC enzymes, thereby inhibiting tumor cell proliferation, inducing apoptosis, promoting cellular differentiation, and inhibiting angiogenesis. This agent may sensitize drug-resistant tumor cells to other antineoplastic agents, possibly through a mechanism involving the down-regulation of thymidylate synthase. PXD101 has been shown in preclinical studies to have the potential to treat a wide range of solid and hematologic malignancies either as a monotherapy or in combination with other active agents, and both an oral and intravenous formulation of the drug are being evaluated in clinical trials.

CG-200745 is a novel inhibitor of histone deacetylases (HDACs), initially developed by CrystalGenomics, Inc for treatment of various hematological and solid cancers. Combinations of CG-200745 with SN38 (the active form of irinotecan), or oxaliplatin were more effective than the agents alone when used to inhibit the growth of HCT116 cells. The protein expressions of acetyl-H3, p21, caspase-3, -8, and -9, PARP, and XIAP were affected in a time- and dose-dependent manner in HCT116 cells treated with the CG-200745 alone or combined CG-200745 and SN-38. In HCT116 xenografts, the HDACI CG-200745 in combination with irinotecan dramatically inhibited tumor growth without showing additive toxicity.