A preliminary study on radiolabeling and quality control of [99mTc]Tc-6-mercaptopurine to develop tumor scintigraphic agent

Aim: Cancer is one of the most cause of deaths in worldwide. 6-mercaptopurine (6-MP) is successfully to treat leukemia. In recent years, 6-MP has remarkable properties for treating solid tumors. The aim of this study is to radiolabel 6-MP with [99mTc]Tc under appropriate conditions to develop tumor scintigraphic agent. Methods: In this work, 6-MP was radiolabeled using [99mTc]Tc radionuclide, and quality control experiment of [99mTc]Tc-6-MP were assessed via radioactive thin layer chromatography (RTLC). Also, the effect of critical parameters affecting the radiolabeling efficiency (reducing and antioxidant agent, incubation time, pH value, radiation dose) was evaluated. Then, the stability and lipophilicity tests of [99mTc]Tc-6-MP was performed. Results: According to the results, [99mTc]Tc-6-MP was prepared with over 93% labeling efficiency by a novel, easy, and quick direct method with 15-min incubation time at pH 7. To achieve the best radiolabeling condition; 0.5 mg.mL-1 of 6-MP solution, 250 µg of stannous tartrate (reducing agent), 0.050 mg ascorbic acid (antioxidant agent), and 37 MBq [99mTc]Tc was used. The RTLC studies indicated that [99mTc]Tc-6-MP is stable up to 6-h in room temperature. The logP of the [99mTc]Tc-6-MP were found to be -0.021 ± -0.001. Conclusions: The obtained results showed that radiolabeled 6-MP may be a promising tumor diagnostic agent. Further studies are in progress in order to evaluate tumor cell binding capacity and biodistribution of the complex in experimental animals.