Engineering Hypoxia-Responsive 6-Aminonicotinamide Prodrugs for On-Demand NADPH Depletion and Redox Manipulation

Glucose-6-phosphate dehydrogenase (G6PD) is a promising target in cancer therapy. However, poor cellular uptake and off-target toxicity impeded the clinical translation of a canonical G6PD inhibitor (6-aminonicotinamide/6AN). Here, we report a prodrug strategy to address this issue. The tailored 6AN prodrug contains an azo-bearing protection moiety. The hydrophobic prodrug showed increased cellular uptake than 6AN and is vulnerable to hypoxia, resulting in NAD(P)H quinone dehydrogenase 1 (NQO1)-triggered cleavage of azo bonds. Intriguingly, the prodrug shows configuration-dependent anti-cancer potency. Despite the lower thermodynamic stability, the cis isomer showed enhanced cellular uptake compared to the trans counterpart due to the increased aqueous solubility. Moreover, the boosted potency of cis isomer compared to the trans isomer resulted from the enhancement of NOQ1-catalyzed 6AN release under hypoxia, a hallmark of solid tumors. The discovery of hypoxia-responsive 6AN prodrugs in the current work opens new avenues of G6PD-targeting cancer medicines via redox manipulation.