Radiochemical Evaluation of New 99mTc-labelled Bombesin Derivatives with Tripeptidic (Ser- Ser - Ser) and (Gly-Gly-Gly) Spacer for Targeting GRP Receptor Positive-tumors

Background and Bombesin shows very high-affinity for the Gasterin releasing peptide (GRP) receptors which are over expressed in different human tumors such as breast and prostate. The aim of this study was to identify a new bombesin derivative labeled with 99mTc via HYNIC that might be used as a noninvasive tool for diagnosis of GRP receptor expressing tumors. Prepared bombein derivatives were radiolabeled with 99mTc at 100 °C for 10 min by exchange method and radiochemical analysis was performed using ITLC and HPLC methods. The stability of radiopeptide was checked in the presence of human serum at 37 °C and saline for up to 24 h. [99mTc-EDDA/tricin/HYNIC-(Ser)3-D-Phe13]BN(7-14) and [99mTc-EDDA/tricin/ HYNIC-(Gly)3-D-Phe13]BN (7-14) were obtained with radiochemical purities of >95%. Results of in-vitro studies demonstrated a high stability in serum and saline. Radiolabeling of this novel conjugates with 99mTc were easily performed using exchange labeling. The prepared 99mTc-HYNIC-BN conjugates demonstrated some potential as site-directed diagnostic radiopharmaceuticals. Therefore, more in vivo studies are required.