Synthesis and evaluation of the 99mtc-complexes of L-cysteine acetyldiglycine (a hybrid of MAG3 and LL-EC) and of l-beta-homocysteine acetyldiglycine

Conjugates of For-MLFK and For-NleLFNleYK with S-benzyl mercaptoacetyl dipeptides containing, respectively, zero, one, and two carboxyl functions in their structures were prepared and labeled with 99mTc. In vitro binding studies using isolated human granulocytes indicated specific receptor binding of the radiolabeled conjugates. The fraction of granulocyteassociated activity was determined after incubation with total blood. Biodistribution studies of the 99mTc-peptides in normal mice revealed a very fast blood clearance proceeding mainly via the hepatobiliary system. Urinary excretion was higher for conjugates containing carboxyl functions in their ligand structures.