Cancer-Specific, Intracellular, Reductive Activation of Anticancer Pt^IV Prodrugs

Because cellular uptake of anticancer Pt^II and Pt^IV drugs occurs by different mechanisms, the latter ones can exhibit substantial activity towards cells, which have either intrinsic or acquired resistance towards Pt^II drugs. However, this positive effect is diminished due to reductive activation of Pt^IV drugs in extracellular space that can be one of the reasons why they have not yet been approved for clinical use despite over 60 clinical trials conducted worldwide. Herein, we suggest a solution to this problem by achieving highly specific intracellular versus extracellular prodrug reduction. In particular, we prepared a hybrid Pt^IV prodrug containing two pro-reductants. This hybrid was uptaken by cells, the pro-reductants were activated in the cancer-specific microenvironment (high H₂ O₂ ), and reduced Pt^IV by two one-electron transfers. The drug formed in this way induced cell death both in cisplatin-sensitive and resistant cell lines, but remained nontoxic to normal cells.