Romidepsin is an anticancer agent undergoing clinical trials as a treatment for cutaneous T-cell lymphoma (CTCL), peripheral T-cell lymphoma, and a variety of other cancers. Romidepsin is a natural product obtained from the bacteria Chromobacterium violaceum, and works by blocking enzymes known as histone deacetylases and inducing apoptosis. It is sometimes referred to as depsipeptide, after the class of molecules to which it belongs. Romidepsin acts as a prodrug with the disulfide bond undergoing reduction within the cell to release a zinc-binding thiol. The thiol reversibly interacts with a zinc atom in the binding pocket of Zn-dependent histone deacetylase to block its activity. Thus it is an HDAC inhibitor. Many HDAC inhibitors are potential treatments for cancer through the ability to restore normal expression of genes, which may result in cell cycle arrest, differentiation, and apoptosis.