Radiosynthesis, radiochemical, and biological characterization of 177Lu‐labeled diethylenetriamine penta‐acetic acid

Diethylenetriamine penta‐acetic acid (DTPA), when complexed with a gamma (γ)‐emitter radioisotope like 99mTc, is used for renal function diagnosis and many other diagnostic applications. The main aim of this study was to develop a novel and versatile single‐step methodology for the synthesis of a new 177Lu‐labeled radiopharmaceutical with high radiochemical yield, which can be used for diagnostic purposes and therapeutic purposes also. The single and well‐defined 177Lu‐DTPA complex was radiochemically characterized by paper chromatography, thin‐layer chromatography, high‐performance liquid chromatography, and electrophoresis techniques. Dependence of the labeling yield of 177Lu‐DTPA complex on different factors was studied in detail. Biological evaluation was also performed in a normal rabbit by developing images under a γ camera at various time intervals. More than 99% labeling yield was obtained by reacting DTPA with 177Lu at specific conditions (pH 7.0, 15 minutes reaction time at 100 °C). 177Lu‐DTPA complex showed high stability both at room temperature and in vitro. Biodistribution studies in normal mice indicated the fractional renal uptake of intravenously administered 177Lu‐DTPA complex, which reached in the kidneys within 2‐3 minutes. Scintigraphy showed rapid clearance from the body. Based on these results, we propose that 177Lu‐DTPA complex might be used as an ideal candidate for functional evaluation of kidneys and the urinary tract, especially when needed to be transported to long‐range consumer sites, because of its suitable half‐life. Single‐step radiolabeling of diethylenetriamine penta‐acetic acid (DTPA) with 177Lu was successfully achieved with high labeling yield (99 ± 1.0%). The labeled 177Lu‐DTPA complex had excellent stability at room temperature and in human serum. The factors controlling the labeling efficiency of 177Lu‐DTPA were investigated in detail. The current study demonstrates a high potential approach for kidney and bladder imaging (evaluation of renal function) and treatment in case of abnormalities (cancer/infection) using 177Lu‐DTPA complex. Given the stability, labeling yield, and half‐life of our complex, we propose that 177Lu‐DTPA might be used as an ideal candidate for functional evaluation of kidneys and the urinary tract, especially when needed to be transported to long‐range consumer sites because it has suitable half‐life for such conditions.