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Hypoxic cell radiosensitizers: expectations and progress in drug development

Journal Article · · Int. J. Radiat. Oncol., Biol. Phys.; (United States)
When misonidazole (MISO) was introduced into clinical trials there were great expectations that the cure rate of many tumors would be dramatically increased. The lack of efficacy of MISO discouraged further studies with hypoxic cell sensitizers. In recent years superior sensitizers SR 2508 and RO-03-8799 have been introduced into the clinic. SR 2508 is less neurotoxic than MISO, allowing more than three times the total amount of drug to be administered. Furthermore, based on the analysis of a patient's plasma pharmacokinetic profile, neurotoxicity may be largely avoidable. RO-03-8799 is superior in that it produces a higher sensitizer enhancement ratio than MISO for the same administered dose. Unlike with MISO and SR 2508, the dose of RO-03-8799 that can be administered is limited by acute toxicity with no cumulative toxicity having yet been encountered. Study design has improved and the expected clinical benefit from sensitizers has been clarified. Sensitizers, like particle radiation therapy and hyperthemia will, if successful, effect the rate of local tumor control, but cannot improve the cure rate of patients with preexisting metastatic disease. Taking into account the need to optimize reoxygenation, the various reasons for tumor radioresistance other than hypoxia, and the lower oxygen and sensitizer enhancement ratios at 200 cGy per fraction, it is likely that sensitizers will provide some clinical benefit for patients with selected tumor types.
Research Organization:
Stanford Univ. Medical Center, CA
OSTI ID:
5652626
Journal Information:
Int. J. Radiat. Oncol., Biol. Phys.; (United States), Journal Name: Int. J. Radiat. Oncol., Biol. Phys.; (United States) Vol. 11:2; ISSN IOBPD
Country of Publication:
United States
Language:
English