Histone deacetylases comprise a family of 18 related enzymes found in most human cells. Eleven of these enzymes, also referred to as HDACs, utilize zinc atoms to catalyze the removal of acetyl groups from both histone and cytoplasmic proteins.

Histone proteins are closely associated with the double-helix strands of DNA in the nucleus of a cell. Acetylation of histones causes structural changes in the DNA-histone complex (“chromatin”) resulting in altered rates of DNA transcription and protein synthesis in cells.

Chemical inhibition of Class I HDACs results in the hyperacetylation of histones which revearses transcriptional repression and triggers the production of proteins that are deleterious to cancer cell proliferation and survival.