TH-302 is a hypoxia-activated prodrug and DNA alkylating agent with anticancer activity. It is selectively cytotoxic to H460 human non-small cell lung cancer (NSCLC) cells grown under hypoxic over normoxic conditions (IC50s = 0.019 and 5.1 μM, respectively). Under hypoxic conditions, TH-302 undergoes a one-electron reduction to form an active radical intermediate that is then further reduced to form a DNA-intercalating hydroxylamine. Under normoxic conditions, the radical intermediate is quenched and induces reformation of the inactive nitroazole prodrug. TH-302 reduces survival of H460 and HT-29 cells in a clonogenic assay (IC50s = 0.2 and 0.2 μM, respectively). In vivo, TH-302 (33 mg/kg per day) inhibits primary tumor growth by 41% in an MIA PaCa-2-RFP mouse orthotopic xenograft model. It inhibits tumor growth by greater than 40% in Calu-6 NSCLC, H82 small cell lung, A375 melanoma, PC-3 prostate, and BxPC-3 pancreatic cancer mouse xenograft models when administered at 50 mg/kg.
