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.