Selectively Targeting Tumor Hypoxia with the Hypoxia-Activated Prodrug CP-506

Alexander M A van der Wiel, Victoria Jackson-Patel, Raymon Niemans, Ala Yaromina, Emily Liu, Damiënne Marcus, Alexandra M Mowday, Natasja G Lieuwes, Rianne Biemans, Xiaojing Lin, Zhe Fu, Sisira Kumara, Arthur Jochems, Amir Ashoorzadeh, Robert F Anderson, Kevin O Hicks, Matthew R Bull, Maria R Abbattista, Christopher P Guise, Sofie DeschoemaekerSophie Thiolloy, Arne Heyerick, Morwena J Solivio, Silvia Balbo, Jeff B Smaill, Jan Theys, Ludwig J Dubois, Adam V Patterson, Philippe Lambin

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Hypoxia-activated prodrugs (HAPs) are a promising class of antineoplastic agents that can selectively eliminate hypoxic tumor cells. The present study evaluates the hypoxia-selectivity and antitumor activity of CP-506, a DNA alkylating HAP with favorable pharmacological properties. Stoichiometry of reduction, one-electron affinity, and back-oxidation rate of CP-506 were characterized by fast-reaction radiolytic methods with observed parameters fulfilling requirements for oxygen-sensitive bioactivation. Net reduction, metabolism, and cytotoxicity of CP-506 were maximally inhibited at oxygen concentrations above 1 μM (0.1% O2). CP-506 demonstrated cytotoxicity selectively in hypoxic 2D and 3D cell cultures with normoxic/anoxic IC50 ratios up to 203. Complete resistance to aerobic (two-electron) metabolism by aldo-keto reductase 1C3 was confirmed through gain-of-function studies whilst retention of hypoxic (one-electron) bioactivation by various diflavin oxidoreductases was also demonstrated. In vivo, the antitumor effects of CP-506 were selective for hypoxic tumor cells and causally related to tumor oxygenation. CP-506 effectively decreased the hypoxic fraction and inhibited growth of a wide range of hypoxic xenografts. A multivariate regression analysis revealed baseline tumor hypoxia and in vitro sensitivity to CP-506 to significantly correlate with treatment response. Our results demonstrate that CP-506 selectively targets hypoxic tumor cells and has broad antitumor activity. Our data indicates that tumor hypoxia and cellular sensitivity to CP-506 are strong determinants of the antitumor effects of CP-506.

Original languageEnglish
JournalMolecular Cancer Therapeutics
Publication statusE-pub ahead of print - 8 Oct 2021

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