A benzotriazine di-N-oxide with potential antineoplastic activity. Tirapazamine is selectively activated by multiple reductases to form free radicals in hypoxic cells, thereby inducing single-and double-strand breaks in DNA, base damage, and cell death. This agent also sensitizes hypoxic cells to ionizing radiation and inhibits the repair of radiation-induced DNA strand breaks via inhibition of topoisomerase II. OR A substance that has been studied in the treatment of some types of cancer. It may cause damage to the DNA in cells that have a low level of oxygen, including cancer cells. This may make the cells easier to kill with radiation therapy and chemotherapy. Tirapazamine is a type of radiosensitizing agent and a type of chemosensitizing agent.