The clinical development of histone deacetylase inhibitors as targeted anticancer drugs

Importance of the field: Histone deacetylase (HDAC) inhibitors are being developed as a new, targeted class of anticancer drugs. Area covered in this review: This review focuses on the mechanisms of action of the HDAC inhibitors, which selectively induce cancer cell death. What the reader will gain: There are 11 zinc-dependent HDACs in humans and the biological roles of these lysine deacetylases are not completely understood. It is clear that these different HDACs are not redundant in their activity. This review focuses on the mechanisms by which HDAC inhibitors can induce transformed cell growth arrest and cell death, inhibit cell mobility and have antiangiogenesis activity. There are more than a dozen HDAC inhibitors, including hydroxamates, cyclic peptides, benzamides and fatty acids, in various stages of clinical trials and many more compounds in preclinical development. The chemically different HDAC inhibitors may target different HDACs. Take home message: There are extensive preclinical studies with transformed cells in culture and tumor-bearing animal models, as well as limited clinical studies reported to date, which indicate that HDAC inhibitors will be most useful when used in combination with cytotoxic or other targeted anticancer agents.