Fighting against Drug-Resistant Tumors using a Dual-Responsive Pt(IV)/Ru(II) Bimetallic Polymer

Drug resistance is a major problem in cancer treatment. Herein, the design of a dual-responsive Pt(IV)/Ru(II) bimetallic polymer (PolyPt/Ru) to treat cisplatin-resistant tumors in a patient-derived xenograft (PDX) model is reported. PolyPt/Ru is an amphiphilic ABA-type triblock copolymer. The hydrophilic A blocks consist of biocompatible poly(ethylene glycol) (PEG). The hydrophobic B block contains reduction-responsive Pt(IV) and red-light-responsive Ru(II) moieties. PolyPt/Ru self-assembles into nanoparticles that are efficiently taken up by cisplatin-resistant cancer cells. Irradiation of cancer cells containing PolyPt/Ru nanoparticles with red light generates 1 O2 , induces polymer degradation, and triggers the release of the Ru(II) anticancer agent. Meanwhile, the anticancer drug, cisplatin, is released in the intracellular environment via reduction of the Pt(IV) moieties. The released Ru(II) anticancer agent, cisplatin, and the generated 1 O2 have different anticancer mechanisms; their synergistic effects inhibit the growth of drug-resistant cancer cells. Furthermore, PolyPt/Ru nanoparticles inhibit tumor growth in a PDX mouse model because they circulate in the bloodstream, accumulate at tumor sites, exhibit good biocompatibility, and do not cause side effects. The results demonstrate that the development of stimuli-responsive multi-metallic polymers provides a new strategy to overcome drug resistance.