Fluorinated 2-nitroimidazole derivative hypoxic cell radiosensitizers: radiosensitizing activities and pharmacokinetics.
OBJECTIVE
To assess the effects of incorporation of a CF2 group into the side chain of a 2-nitroimidazole derivative, we evaluated the in vitro and in vivo radiosensitizing activities of KU-2285 (a 2-nitroimidazole derivative with an N1-substituent of -CH2CF2CONH(CH2)nOH, n = 2) and its related compounds in comparison with those of comparable nonfluorinated compounds. The pharmacokinetics of these compounds in murine tumors was also tested.


METHODS
KU-2285, KU-3202 (n = 3) and KU-3207 (n = 4) are fluorinated 2-nitroimidazole derivative compounds with similar structures. Etanidazole (a 2-nitroimidazole derivative with an N1-substituent of -CH2CONH(CH2)nOH, n = 2) and its related compounds, KU-3205 (n = 3) and KU-3206 (n = 4) were also tested. The in vitro radiosensitizing activities of each compound for hypoxic cells was evaluated with a standard colony formation method. The in vivo radiosensitizing activities of these compounds were tested in female C3H/He mice bearing SCCVII tumors using an in vivo/in vitro clonogenic assay. The pharmacokinetic studies were performed in C3H/He mice bearing the SCCVII tumor. Samples were analyzed by reverse-phase high-performance liquid chromatography.


RESULTS
The in vitro radiosensitizing activities of fluorinated 2-nitroimidazoles were higher than those of the nonfluorinated compounds. Although the in vivo radiosensitizing activity of KU-2285 was higher than that of etanidazole (p < 0.05), other fluorinated 2-nitroimidazoles showed less radiosensitizing activity than the comparable nonfluorinated compounds. The compound was eliminated from serum more rapidly with the increase in the number of CH2 group in the side chain of the compound in each series.


CONCLUSIONS
Although the in vitro sensitizing activity of the fluorinated compounds was higher than that of the comparable nonfluorinated compounds, the in vivo radiosensitizing activity of all fluorinated compounds but KU-2285 was lower than that of comparable etanidazole group compounds, probably due to their lower molecular concentrations in tumor and rapid elimination.
Sasai
K
K
Department of Radiology, Faculty of Medicine, Kyoto University, Japan.
Iwai
H
H
Yoshizawa
T
T
Nishimoto
S
S
Shibamoto
Y
Y
Oya
N
N
Shibata
T
T
Abe
M
M
D000818:Animals; D005260:Female; D051379:Mice; D008809:Mice, Inbred C3H; D009593:Nitroimidazoles / Q000494:pharmacology*; D011838:Radiation-Sensitizing Agents / Q000493:pharmacokinetics / Q000494:pharmacology*; D012995:Solubility
D009593:Nitroimidazoles; D011838:Radiation-Sensitizing Agents; C069296:KU 2285