Discovery of mitochondrion-targeting copper(II)-plumbagin and -bipyridine complexes as chemodynamic therapy agents with enhanced antitumor activity.

Four copper(II)-plumbagin and -bipyridine complexes (Cu1-Cu4) were synthesized as chemodynamic therapy agents with enhanced antitumor activity. As lipophilic and positively charged compounds, Cu1-Cu4 were preferentially accumulated in mitochondria and activated the mitochondrial apoptosis pathway. Mechanistic studies showed that Cu1-Cu4 reacted with GSH to reduce Cu2+ ions to Cu+ ions, catalyzed the formation of toxic hydroxyl radicals (˙OH) from hydrogen peroxide (H2O2) through a Fenton-like reaction, induced mitochondrial dysfunction, and activated caspase-9/3, which eventually led to apoptosis. Cu1-Cu4 arrested HeLa cells in the S phase and eventually killed cancer cells. Cu2 showed a favorable pharmacokinetic profile in mice. Moreover, Cu2 effectively inhibited the growth of HeLa xenografts in nude mice and showed low toxicity in vivo.

Platinum-Based Mcl-1 Inhibitor Targeting Mitochondria Achieves Enhanced Antitumor Activity as a Single Agent or in Combination with ABT-199.

Discovery of small molecule inhibitors targeting Mcl-1 (Myeloid cell leukemia 1) confronts many challenges. Based on the fact that Mcl-1 is mainly localized in mitochondria, we propose a new strategy of targeting mitochondria to improve the binding efficiency of Mcl-1 inhibitors. We report the discovery of complex 9, the first mitochondrial targeting platinum-based inhibitor of Mcl-1, which selectively binds to Mcl-1 with high binding affinity. Complex 9 was mainly concentrated in the mitochondria of tumor cells which led to an enhanced antitumor efficacy. Complex 9 induced Bax/Bak-dependent apoptosis in LP-1 cells and synergized with ABT-199 to kill ABT-199 resistant cells in multiple cancer models. Complex 9 was effective and tolerable as a single agent or in combination with ABT-199 in mouse models. This research work demonstrated that developing mitochondria-targeting Mcl-1 inhibitors is a new potentially efficient strategy for tumor therapy.