Review of the Most Important Research Trends in Potential Chemotherapeutics Based on Coordination Compounds of Ruthenium, Rhodium and Iridium

This review paper presents a comprehensive literature analysis that elucidates the global engagement of research teams in addressing the important problem of finding effective oncology drugs based on the following platinum group metal ions: ruthenium, rhodium and iridium. The necessity to search for new drugs can be attributed, in part, to the predominance of platinum-based chemotherapeutics in clinical practice. However, these drugs face limitations in their clinical application due to their inherent toxicity and the development of resistance by cancer cells. A distinctive attribute of these metal compounds is the formation of diamagnetic stable complexes on +II (Ru) and +III (Rh, Ir) oxidation degrees with a d6 electron configuration, a coordination number of six and an octahedral or pseudo-octahedral structure. In this paper we have systematised the findings presented in the literature by classifying the most significant categories of ruthenium, rhodium and iridium compounds, namely piano-stool-type arenes, polypyridine and cyclometalated complexes, dimers and multinuclear complexes. Additionally, the most crucial research challenges connected with metal complexes that have been addressed by scientists have been presented: (i) the application of prodrugs in cancer therapy; (ii) the deployment of complexes as sensitizers in PDT and PACT; (iii) the exploration of complexes as inhibitors of enzymes and biocatalysts; and (iv) the investigation of multiple-target complexes. Furthermore, the objective was to emphasise the accomplishments in this domain in recent years by identifying compounds that have entered the clinical trial phase.