Development of 166Ho-zoledronate as a bone marrow ablative agent

In this study, production, quality control and biodistribution studies of 166Ho-zoledronate have been presented as a possible bone marrow ablative agent. Ho-166 chloride was produced by thermal neutron irradiation of natural 165Ho(NO3)3 samples. 166Ho-zoledronate complex was prepared by adding the desired amount of zoledronate solution (0.2 mL, 150 mg/ml in 1 M NaOH) to appropriate amount of the 166HoCl3 solution. Radiochemical purity of the complex was monitored by instant thin layer chromatography (ITLC). Stability studies of the complex in the final preparation and in the presence of human serum were performed up to 48 h. The biodistribution of 166Ho-zoledronate and 166HoCl3 in wild-type mice was checked up to 72 h. 166Ho-zoledronate complex was prepared in high radiochemical purity (> 99%, ITLC) and specific activity of 4.4 GBq/mmol. The major accumulation of radiolabelled complex was observed in the bone tissue. These findings suggest 166Ho-zoledronatehas can be a possible candidate for bone marrow ablation in patients with multiple myeloma.