A 99mTc-Labeled Misonidazole Analogue: Step Toward a 99mTc-Alternative to [18F]Fluromisonidazole for Detecting Tumor Hypoxia.

The PET radiopharmaceutical [18F]Fluromisonidazole ([18F]FMISO) is presently the agent of choice for the clinical imaging of tumor hypoxia. Considering the logistic advantages of 99mTc and wider availability of SPECT machines, a 99mTc-radiopharmaceutical for this purpose constitutes an attractive choice. In the work presented here, a misonidazole analogue was radiolabeled with 99mTc(CO)3 core and the complex was evaluated in Swiss mice bearing fibrosarcoma tumor. The results obtained are compared with the biodistribution of [18F]FMISO carried out in the same tumor-bearing animal model. Misonidazole-99mTc(CO)3 complex showed significant uptake and retention in tumor. Notably, the rate of clearance of misonidazole complex from the tumor was slower than that of [18F]FMISO. The maximum tumor/muscle ratio obtained with misonidazole-99mTc(CO)3 complex was significantly higher than that of [18F]FMISO. The study constitutes a positive step toward the development of a 99mTc-analogue of [18F]FMISO. [ABSTRACT FROM AUTHOR]