title: Coligand effects on the solution stability, biodistribution and metabolism of the (99m)Tc-labeled cyclic RGDfK tetramer.
abstract: In this study, we present the evaluation of two new ternary ligand (99m)Tc complexes [(99m)Tc(HYNIC tetramer)(tricine)(L)] [L=isonicotinic acid (ISONIC) and 2,5-pyridinedicarboxylic acid (PDA)] as potential radiotracers for tumor imaging. Athymic nude mice bearing MDA-MB-435 human breast cancer xenografts were used to evaluate their biodistribution and metabolic properties. Solution stability data showed that [(99m)Tc(HYNIC tetramer)(tricine)(L)] (L=ISONIC and PDA) had significant decomposition (14% and 35%, respectively) at 6 h in the absence of excess ISONIC or PDA coligand. Biodistribution data clearly showed that [(99m)Tc(HYNIC tetramer)(tricine)(PDA)] had a much lower uptake in most organs of interest than [(99m)Tc(HYNIC tetramer)(tricine)(ISONIC)] during the 2-h study period. Results from metabolism studies revealed that approximately 50% of [(99m)Tc(HYNIC tetramer)(tricine)(ISONIC)] remained intact in fecal samples at 120 min postinjection, whereas only 10% of [(99m)Tc(HYNIC tetramer)(tricine)(PDA)] remained intact in fecal samples. The extent of metabolism correlated well with radiotracer solution stability. The results from this and our previous studies clearly demonstrated that coligands [trisodium triphenylphosphine-3,3',3''-trisulfonate (TPPTS), ISONIC and PDA] have a significant impact on the tumor uptake, excretion kinetics and metabolism of the (99m)Tc-labeled cyclic RGDfK tetramer. Among the three radiotracers evaluated in this tumor-bearing animal model, [(99m)Tc(HYNIC tetramer)(tricine)(TPPTS)] remained the best with respect to blood clearance, tumor uptake and target/background ratios.
authors.affiliation: School of Health Sciences, Purdue University, West Lafayette, IN 47907, USA. lius@pharmacy.purdue.edu
authors.forename: Shuang
authors.initials: S
authors.lastname: Liu
authors.forename: Young-Seung
authors.initials: YS
authors.lastname: Kim
authors.forename: Wen-Yuan
authors.initials: WY
authors.lastname: Hsieh
authors.forename: Subramanya
authors.initials: S
authors.lastname: Gupta Sreerama
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006801:Humans; D008024:Ligands; D051379:Mice; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000000981:diagnostic imaging / Q000378:metabolism*; D015609:Organotechnetium Compounds; D010456:Peptides, Cyclic / Q000378:metabolism*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000378:metabolism*; D014018:Tissue Distribution; D014183:Transplantation, Heterologous
chemical_list: D008024:Ligands; D015609:Organotechnetium Compounds; D010456:Peptides, Cyclic; D019275:Radiopharmaceuticals; C507169:cyclic arginine-glycine-aspartic acid peptide