Recent Developments in Antitumor Activity of Organometallic Rhodium Complex Compounds with Macrocyclic Ligands

Currently, the most extensively utilized medical anticancer treatment is chemotherapy with metal-based chemotherapeutic agents. Platinum group metals and their complexes constitute one of the most widely used classes of anticancer candidates. The limitations, connected with the resistance and toxicity, posed by the classical antitumor metal-based drugs have stimulated the development of novel agents by using different metal cations to improve the activity with minimal adverse effects. Subsequently, there is excessive interest in the design of new coordination complexes of other platinum group metals, between them rhodium, which can be potent chemotherapeutics, since its equipotency to the platinum and ruthenium analogues and possess the benefit of being inert at the same physiological conditions. Many rhodium-based compounds has been obtained and established for their antineoplastic activity in the last decades. Most of them have exposed comparatively high cytotoxic activity and less toxicity. Rh(I), Rh(II) and Rh(III) complexes seem to have different profiles of bioactivity compared to the metal antitumor complexes in medical use. The design of macrocyclic ligands and their complexes is a developing research area in view of their existence in numerous biologically significant systems. That is why, rhodium coordination and organometallic compounds could be a possible additional alternative to classical metal-based medications, and their pharmacological properties deserve further investigations. Recent developments in the synthesis of rhodium organometallic and complex antineoplastic compounds with macrocyclic ligands have been summarized and discussed.