Preparation and Preliminary Evaluation of the in vivo and in vitro hypoxic selectivity of a novel hypoxic agent 99Tcm-N4IPA

Objective To develop a novel hypoxic agent with simple structure、excellent performance and easily labeled technique. Method A new hypoxic ligand 1-(4-Nitroimidazole-1-yl)-propanhydroxyiminoamide (N4IPA) was labeled with 99Tcm, then the products were analyzed by TLC and HPLC and were detected the in vitro stability、the octanol-water partition coefficient and the pattern of blood clearance. Finally, the in vivo and in vitro hypoxic selectivity of the products were researched by cell up-take test in vitro and biodistribution and imaging in vivo with nude mice bearing U87 glioma. Results The labeling yield was >90% and the octanol-water partition coefficient was 2.71±0.05 (n=3), and the products kept pretty good stability in room temperature、37 ℃ and in 37 ℃ with human serum albumin. The cell up-take test showed that the Chinese hamster ovary (CHO) cell took more products in hypoxic system than that in normal oxygen system (p<0.05), and the up-take percent in hypoxic system increased with time. Pattern of blood clearance of 99mTc-N4IPA was defined as two-compartment model（T1/2α＝15 min，T1/2β＝10.2h）. Imaging and distribution in nude mice bearing U87 glioma revealed that the products were excreted mainly by kidneys and partly by liver and intestines. 99mTc-N4IPA could be accumulated in tumor, and the tumor-blood ratio in 2 hours and 4hours was 1.57±0.31 and 1.98±0.25, respectively, and the tumor-muscle ratio in 2 hours and 4hours was 11.89±1.64 and 13.11±1.47.Conclusion 99Tcm－N4IPA possessed hypoxic selectivity with clear tumor imaging，so it would be a potential hypoxic-agent, but it would need more research work.