First Evaluation of a 99mTc-Tricarbonyl Complex, 99mTc(CO)3(LAN), as a New Renal Radiopharmaceutical in Humans

ethylene-cysteine (99mTc-MAEC) contain N3S or N2S2 ligands designed to accommodate the 4 ligating sites of the (99mTcO)31 core; they are all excellent renal imaging agents but have renal clearances lower than that of 131I-orthoiodohippurate (131I-OIH). To explore the potential of the newly accessible but less polar [99mTc(CO)3]1 core with 3 ligating sites, we decided to build on the success of 99mTc-EC, with its N2S2 ligand and 2 dangling car-boxylate groups; we chose an N2S ligand that also has 2 dangling carboxylate groups, lanthionine, to form 99mTc(CO)3(LAN), a new renal radiopharmaceutical. Methods: Biodistribution studies were performed on Sprague–Dawley rats with 99mTc(CO)3(LAN) isomers, meso-LAN and DD,LL-LAN (an enantiomeric mixture), coinjected with 131I-OIH. Human studies also were performed by coinjecting each 99mTc-labeled product (;74 MBq [;2 mCi]) and 131I-OIH (;7.4 MBq [;0.2 mCi]) into 3 healthy volunteer