Chapters 3 and 4 of this book describe in detail the many positive aspects, and also the drawbacks, of cisplatin and of the other clinically used Pt chemotherapeutics. The major limitations of such drugs are a narrow range of activity (they are scarcely active against several malignancies with high social incidence), severe toxic side-effects, and intrinsic or acquired tumor resistance observed during treatment.

Compounds of almost all metals of the periodic table have been investigated for in vitro anticancer activity against cancer cell lines–the most widely used screening method–and in many cases some activity has been reported. However, most often in vitro cytotoxicity has not been paralleled by in vivo therapeutic activity, and only a few of the many metal compounds investigated in vitro have shown some realistic follow-up. Therefore, given that cytotoxic activity against cancer cells should not be mistaken for anticancer activity, this chapter will treat exclusively those non-platinum compounds, or classes of compounds, that have shown the most promising results in convincing tumor models or have even entered clinical trials. They include derivatives of titanium, gallium, iron, osmium, germanium, arsenic, lanthanides, and, above all, ruthenium. Gold compounds are treated separately in Chapter 7.