Monofunctional Platinum(II) Anticancer Agents

Platinum-based anticancer drugs represented by cisplatin play important roles in the treatment of various solid tumors. However, their applications are largely compromised by drug resistance and side effects. Much effort has been made to circumvent the drug resistance and general toxicity of these drugs. Among multifarious designs, monofunctional platinum(II) complexes with a general formula of [Pt(3A)Cl]⁺ (A: Ammonia or amine) stand out as a class of "non-traditional" anticancer agents hopeful to overcome the defects of current platinum drugs. This review aims to summarize the development of monofunctional platinum(II) complexes in recent years. They are classified into four categories: fluorescent complexes, photoactive complexes, targeted complexes, and miscellaneous complexes. The intention behind the designs is either to visualize the cellular distribution, or to reduce the side effects, or to improve the tumor selectivity, or inhibit the cancer cells through non-DNA targets. The information provided by this review may inspire researchers to conceive more innovative complexes with potent efficacy to shake off the drawbacks of platinum anticancer drugs.

Novel Quinoline-based Ir(III) Complexes Exhibit High Antitumor Activity in Vitro and in Vivo

Eight novel Ir(III) complexes listed as [Ir(H-P)₂(P)]PF₆ (PyP-Ir), [Ir(H-P)₂(dMP)]PF₆ (PydMP-Ir), [Ir(H-P)₂(MP)]PF₆ (PyMP-Ir), [Ir(H-P)₂(tMP)]PF₆ (PytMP-Ir), [Ir(MPy)₂(P)]PF₆ (MPyP-Ir), [Ir(MPy)₂(dMP)]PF₆ (MPydMP-Ir), [Ir(MPy)₂(MP)]PF₆ (MPyMP-Ir), [Ir(MPy)₂((tMP)]PF₆ (MPytMP-Ir) with 2-phenylpyri-dine (H-P) and 3-methyl-2-phenylpyridine (MPy) as ancillary ligands and pyrido-[3,2-a]-pyrido[1',2':1,2]imidazo[4,5-c]phenazine (P), 12,13-dimethyl pyrido-[3,2-a]-pyrido[1',2':1,2]-imidazo-[4,5-c]-phenazine (dMP), 2-methylpyrido [3,2-a]-pyrido-[1',2':1,2]-imidazo-[4,5-c]-phenazine (MP), and 2,12,13-trimethylpyrido-[3,2-a]-pyrido-[1',2':1,2]-imidazo-[4,5-c]-phenazine (tMP) as main ligands, respectively, were designed and synthesized to fully characterize and explore the effect of their toxicity on cancer cells. Cytotoxic mechanism studies demonstrated that the eight Ir(III) complexes exhibited highly potent antitumor activity selectively against cancer cell lines NCI-H460, T-24, and HeLa, and no activity against HL-7702, a noncancerous cell line. Among the eight Ir(III) complexes, MPytMP-Ir exhibited the highest cytotoxicity with an IC₅₀ = 5.05 ± 0.22 nM against NCI-H460 cells. The antitumor activity of MPytMP-Ir in vitro could be contributed to the steric or electronic effect of the methyl groups, which induced telomerase inhibition and damaged mitochondria in NCI-H460 cells. More importantly, MPytMP-Ir displayed a superior inhibitory effect on NCI-H460 xenograft in vivo than cisplatin. Our work demonstrates that MPytMP-Ir could potentially be developed as a novel potent Ir-based antitumor drug.