Organometallic iron complexes as potential cancer therapeutics

Metal-containing drugs have long been used for medicinal purposes in more or less empirical way. The potential of these anticancer agents has only been fully realised and explored since the discovery of the biological activity of cisplatin. Cisplatin and carboplatin have been two of the most successful anti-cancer agents ever developed, and are currently used to treat ovarian, lung and testicular cancers. They share certain side effects, so their clinical use is severely limited by dose-limiting toxicity. Inherent or acquired resistance is a second problem often associated with platinum-based drugs, with further limits of their clinical use. These problems have prompted chemists to employ different strategies in development of the new metal-based anticancer agents with different mechanisms of action. There are various metal complexes still under development and investigation for the future cancer treatment use. In the search for novel bio-organometallic molecules, iron containing anti-tumoral agents are enjoying an increasing interest and appear very promising as the potential drug candidates. Iron, as an essential cofactor in a number of enzymes and physiological processes, may be less toxic than non essential metals, such as platinum. Up to now, some of iron complexes have been tested as cytotoxic agents and found to be endowed with an antitumor activity in several in vitro tests (on cultured cancer cell lines) and few in vivo experiments (e. g. on Ehrlich's ascites carcinoma). Although the precise molecular mechanism is yet to be defined, a number of observations suggest that the reactive oxygen species can play important role in iron-induced cytotoxicty. This review covers some relevant examples of research on the novel iron complexes.