Site-specific labeling of ‘second generation’ annexin V with 99mTc(CO) 3 for improved imaging of apoptosis in vivo

μSPECT images of 99mTc(CO) 3-HIS- cys-AnxV before (normal) and after treatment with anti-Fas. In this study ‘second generation’ AnxV was specifically labeled with 99mTc in three different ways outside the binding region of the protein to obtain an improved target-to-background activity ratio. The compounds were tested in vitro and in vivo in normal mice and in a model of hepatic apoptosis (anti-Fas mAb). The apoptosis binding was most prominent for the HIS-tagged ‘second generation’ AnxV labeled with 99mTc(CO) 3 in comparison to 99mTc-HYNIC- cys-AnxV and 99mTc(CO) 3-DTPA- cys-AnxV.