Synthesis, Cytotoxicity, and Mechanistic Investigation of Platinum(IV) Anticancer Complexes Conjugated with Poly(ADP-ribose) Polymerase Inhibitors

Many clinical trials using combinations of platinum drugs and PARP-1 inhibitors (PARPi) have been carried out, with the hope that such combinations will lead to enhanced therapeutic outcomes against tumors. Herein, we obtained seven potential PARPi with structural diversity and then conjugated them with cisplatin-based platinum(IV) complexes. Both the synthesized PARPi ligands and PARPi-Pt conjugates [PARPi-Pt(IV)] show inhibitory effects against PARP-1's catalytic activity. The PARPi-Pt(IV) conjugates are cytotoxic in a panel of human cancer cell lines, and the leading ones display the ability to overcome cisplatin resistance. A mechanistic investigation reveals that the representative PARPi-Pt(IV) conjugates efficiently enter cells, bind to genomic DNA, disturb cell cycle distribution, and induce apoptotic cell death in both cisplatin-sensitive and -resistant cells. Our study provides a strategy to improve the cytotoxicity of platinum(IV)-based anticancer complexes and overcome cisplatin resistance by using a small-molecule anticancer complex that simultaneously damages DNA and inhibits PARP.