Coinage Metal NHC Complexes as Novel Antibiotics and Anticancer Drugs

The synthesis and biological evaluation against cancer cells and pathogenic bacteria as well as fungi of five coinage metal NHC complexes derived from copper (WBC4), silver (SBC1/SBC3) and gold (NHC-Au-Cl/NHC-Au-SR) is reviewed. The NHC ligand for these compounds is 1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene or derivatives closely related, since this ligand is proven suitable for drug-like molecules. The NHC-silver acetate complex SBC1 failed as an anticancer drug candidate in vivo, while its highly related compound SBC3 succeeded in vivo as an experimental antibiotic in Galleria mellonella larvae showing survival advantage against pathogenic bacteria and fungi. The corresponding gold complexes of NHC-Au-Cl and NHC-Au-SR (R = thioglucoside) as well as the NHC-copper bromide derivative WBC4 exhibited significant growth inhibition, when tested against xenografted human renal-cell cancer Caki-1 in nude mice; WBC4 showed tolerable toxicity in the form of reversible body weight loss, while the two gold compounds did not induce body weight loss in the xenograft mouse model experiment.