Tuning heavy metal compounds for anti-tumor activity: is diversity the key to ruthenium's success?

This review aims to bring the reader up to date with the more recent ruthenium compounds that have been synthesized and tested for their cytotoxicity. The chemistry of these transition metal complexes will be introduced and the basic principles that govern their common behavior outlined. The recent history of established compounds within this field will be presented alongside those that now represent the cutting-edge. The inherent variety within this class of compounds will lead the reader to appreciate their diversity and pose questions as to their similarities aside from the presence of a shared metal ion. This review aims to discuss and contextualize the state-of-the-art research within the context of the speculative advancement of this developing field. There is an evident need to specify the molecular and cellular targets of these drug molecules in order to ultimately elucidate their mode or modes of action. The evidence presented herein suggests that new avenues of research require novel analytical probes and methods for tracing the fate of ruthenium complexes in cells in order to understand their very promising cytotoxic activity.