A glimpse into the developments, potential leads and future perspectives of anticancer cobalt complexes

The unanticipated finding of cisplatin's anticancer properties prompted extensive investigations into different platinum-containing complexes as anticancer agents. However, the side effects and resilience of cancerous cells to platinum complexes triggered investigations on non-platinum anticancer complexes. As a result, several non-platinum complexes have been developed. Among these, the anticancer potential of cobalt complexes has been recognized over the past few decades. Inorganic medicinal chemists are fascinated by cobalt complexes, as these complexes interact with cellular proteins and macromolecules, causing cellular disruption and stopping the division, growth and multiplication of cancer cells. Owing to the increasing interest of researchers in the development of anticancer cobalt complexes, this paper critically reviews the developments in the design and development of these complexes. The results of the in vitro and in vivo investigations of anticancer profiles of cobalt complexes with ligands such as Schiff bases, quinolines, carbonyl groups, polypyridyl ligands, macrocycles, thiosemicarbazones, active pharmaceuticals, natural products, etc. are reviewed. Importantly, the intervention of nanotechnological approaches in amplifying the therapeutic properties of anticancer cobalt complexes is discussed. Besides, the modes of action of anticancer cobalt complexes are highlighted. Moreover, pharmacologically significant cobalt complexes with equal or better anticancer effects than that of standard anticancer agents are identified. Finally, the existing challenges and future perspectives in research on the design and development of anticancer cobalt complexes are discussed.