An Endogenous Reactive Oxygen Species (ROS)-Activated Histone Deacetylase Inhibitor Prodrug for Cancer Chemotherapy

Suberoylanilide hydroxamic acid (SAHA, vorinostat) is a potent small-molecule pan-inhibitor of histone deacetylases (HDACs) approved for treatment of cutaneous T-cell lymphoma (CTCL). However, SAHA exhibits poor selectivity for cancer cells over noncancer cells. With an aim to improving its selectivity for cancer cells, we generated a novel SAHA prodrug (SAHA-OBP) that is activated in the presence of hydrogen peroxide, a reactive oxygen species (ROS) known to be overexpressed in cancer cells. The high endogenous ROS content in cancer cells triggers rapid removal of the 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl carbonyl (OBP) cap to release active SAHA. The SAHA-OBP prodrug demonstrates selective activity against multiple cancer cell lines such as HeLa, MCF-7, MDA-MB-231, and B16-F10, while remaining benign toward noncancer cells. The downstream effects of SAHA released from SAHA-OBP in cancer cells is the induction of apoptosis. SAHA-OBP was also found to be effective on multicellular tumor spheroids (MCTS). The SAHA prodrug designed in this study undergoes rapid ROS-dependent activation and imparts much-needed selectivity to SAHA for cancer cells.