Synthesis and evaluation of the (99m)tc-complexes of L-cysteine acetyldiglycine (a hybrid of MAG3 and L,L-EC) and of L-beta-homocysteine acetyldiglycine.

L-Cysteine acetyldiglycine (L-CAG2), a hybrid compound of L,L-EC and MAG3, and its L-beta-homocysteine analogue L-HAG2 were synthesized. After labeling with (99m)Tc, (99m)Tc-L-CAG2 and (99m)Tc-L-HAG2 gave two peaks on high performance liquid chromatography. Urinary excretion of both isomers of (99m)Tc-L-CAG2 and (99m)Tc-L-HAG2 was slower than for the "parent" complexes (99m)Tc-MAG3 or (99m)Tc-L,L-EC. Isomer B of (99m)Tc-L-CAG2 showed pronounced kidney retention in mice (57% of ID in kidneys at 30 min postinjection), but further evaluation in baboon did not reproduce this phenomenon.