Antimony-Chelating Compositions and Their Use in Nuclear Medicine

ORNL researchers have identified a chelator that can form a highly stable complex with radio-Sb. This chelator can quantitatively bind Sb-1xx near neutral pH at relatively low chelator concentrations. The resulting complex remains intact over at least one-half life of Sb-119 (half-life = 38 h) when incubated in human serum and in excess cysteine. Ex vivo biodistribution, positron emission tomography (PET) imaging, and single photon emission computed tomography (SPECT) imaging separately quantify and demonstrate distinct biological clearance routes for the Sb-1xx-chelator complex in comparison to unchelated Sb-1xx.  These results suggest that the Sb-1xx complex remains intact in vivo. As such, this chelator will be of significant value for use with Sb-119 for targeted Auger therapy. It will also be valuable for use with imaging isotopes of radioantimony, such as Sb-117.