Design of 99mTc‐DTPA‐CLP and Preliminary Evaluation in Rats

Radiopharmaceuticals are localized in (malignant) tumor tissues by different mechanisms. One of these mechanisms, gelatinase enzyme activity, is associated with poor prognosis in cancer patients and potential targets for tumor imaging. There are some gelatinases to be associated with metastatic potential for tumor imaging to possibly predict metastases. In this study, a cyclic decapeptide conjugate, DTPA‐CLP (DTPA‐Cys‐Leu‐Pro‐Gly‐His‐Trp‐Gly‐Phe‐Pro‐Ser‐Cys), was selected as a peptide conjugate because of its selective inhibitory activity toward gelatinases. Peptide‐conjugated DTPA‐CLP was labeled with ^99mTc with a radiolabeling efficiency of 97.0 ± 2.8%. After determining optimization conditions for radiolabeling, a biodistribution study of radiolabeled peptide in albino Wistar rats was performed. According to biodistribution data, ^99mTc‐DTPA‐CLP showed high uptake in the lung, liver, uterus, and spleen. These results show that ^99mTc‐DTPA‐CLP may be used for the imaging of gelatinase activity in metastatic tumors.