An overview of anticancer platinum N-heterocyclic carbene complexes

Heterocyclic carbenes (NHCs) have been introduced as a new platform for the development of anticancer metal complexes for several decades. NHCs as strong r-donors can coordinate firmly with different noble metals, thereby giving rise to many types of metal NHC complexes. Among them, platinum NHC complexes are regarded as the direct descendants of cisplatin as they have the same central metal ions. Inspiringly, platinum NHC complexes showed comparable activities as cisplatin in many human cancer cell lines while maintaining their activity in cisplatin-resistant cell lines. This lies in the fact that platinum NHC complexes can elicit different mechanisms of action other than those known for conventional platinum complexes. Additionally, platinum NHC complexes were recently reported to elicit biochemical hallmarks of immunogenic cell death (ICD) as a type II ICD inducer. Herein, platinum NHC complexes are categorized according to their structural features, and their anticancer activities are also discussed in detail. Meanwhile, other types of carbene structures are introduced that may be able to be used as platforms for the next generation of platinum NHC complexes. (C) 2021 Elsevier B.V. All rights reserved.