“…However, solid tumors possess a few unique and important microenvironmental properties such as localized hypoxia, nutrient deprivation, and low pH [156]. Taking advantage of these findings, Kwon et al [158] devised a hypoxia-selective alkylating bioprecursor prodrug (Figure 28.46a). The oxidation to the sulfone is the dominant process under normal physiological conditions, but the reduction to the sulfide becomes significant under anaerobiotic conditions [157].…”