Organometallic Osmium Arene Complexes with Potent Cancer Cell Cytotoxicity

Iodido osmium(II) complexes [Os(eta(6)-arene)(XY)I](+) (XY = p-hydroxy or p-dimethylaminophenylazopyridine, arene = p-cymene or biphenyl) are potently cytotoxic at nanomolar concentrations toward a panel of human cancer cell lines; e.g., IC50 = 140 nM for [Os(eta(6)-bip)(azpy-NMe2)I](+) toward A2780 ovarian cancer cells. They exhibit low toxicity and negligible deleterious effects in a colon cancer xenograft model, giving rise to the possibility or, broad therapeutic window. The most active complexes are stable and inert toward aquation. Their cytotoxic activity appears to involve redox mechanisms.