Figure 1.

Hypoxia-activated prodrug strategies. (A) Schematic representation of complementary cell killing achieved by radiation in combination with a high-$K_{{\mathrm{O}}_{\mathrm{2}}}$ HAP and a low-$K_{{\mathrm{O}}_{\mathrm{2}}}$ HAP that generates active metabolites that diffuse out of prodrug-activating zones to kill neighboring cells (bystander). (B) Examples of Class I (SN30000) and Class II (PR-104A) HAP are shown.