title: Development of a rhenium-186-labeled MAG3-conjugated bisphosphonate for the palliation of metastatic bone pain based on the concept of bifunctional radiopharmaceuticals.
abstract: Rhenium-186-1-hydroxyethylidene-1,1-diphosphonate (186Re-HEDP) has been used for the palliation of metastatic bone pain. Delayed blood clearance and high gastric uptake of radioactivity have been observed upon injection, due to the instability of (186)Re-HEDP in vivo. In this study, on the basis of the concept of bifunctional radiopharmaceuticals, we designed a stable 186Re-mercaptoacetylglycylglycylglycine (MAG3) complex-conjugated bisphosphonate, [[[[(4-hydroxy-4,4-diphosphonobutyl)carbamoylmethyl]carbamoylmethyl]carbamoylmethyl]carbamoylmethanethiolate]oxorhenium(V) (186Re-MAG3-HBP). As a precursor, [1-hydroxy-1-phosphono-4-[2-[2-[2-(2-tritylmercaptoacetylamino)acetylamino]acetylamino]acetylamino]butyl]phosphonic acid (Tr-MAG3-HBP) was synthesized by the conjugation of N-[(tritylmercapto)acetyl]glycylglycylglycine (Tr-MAG3) with the bisphosphonate analogue. After deprotection of the trityl group of Tr-MAG3-HBP, 186Re-labeling was performed by reacting 186ReO4- with SnCl2 in citrate buffer. After purification by HPLC, 186Re-MAG3-HBP showed a radiochemical purity of over 95%. To compare the stability of 186Re-MAG3-HBP and 186Re-HEDP, these (186)Re complexes were incubated in phosphate buffer. No measurable decomposition of 186Re-MAG3-HBP occurred over a 24-h period, while only approximately 30% of 186Re-HEDP remained intact 24 h postincubation. In biodistribution experiments, the radioactivity level of 186Re-MAG3-HBP in bone was significantly higher than that of (186)Re-HEDP. Blood clearance of 186Re-MAG3-HBP was faster than that of 186Re-HEDP. In addition, the gastric accumulation of 186Re-MAG3-HBP radioactivity was lower than that of 186Re-HEDP. In conclusion, 186Re-MAG3-HBP is expected to be a useful radiopharmaceutical for the palliation of metastatic bone pain.
authors: Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan.
authors: Kazuma
authors: K
authors: Ogawa
authors: Takahiro
authors: T
authors: Mukai
authors: Yasushi
authors: Y
authors: Arano
authors: Masahiro
authors: M
authors: Ono
authors: Hirofumi
authors: H
authors: Hanaoka
authors: Seigo
authors: S
authors: Ishino
authors: Kazuyuki
authors: K
authors: Hashimoto
authors: Hiroshi
authors: H
authors: Nishimura
authors: Hideo
authors: H
authors: Saji
mesh_terms: D001859:Bone Neoplasms / Q000532:radiotherapy* / Q000556:secondary*; D004164:Diphosphonates / Q000737:chemistry / Q000627:therapeutic use*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D009842:Oligopeptides / Q000737:chemistry / Q000627:therapeutic use*; D009942:Organometallic Compounds / Q000737:chemistry / Q000627:therapeutic use*; D019275:Radiopharmaceuticals / Q000627:therapeutic use*; D012211:Rhenium / Q000737:chemistry / Q000627:therapeutic use*; D016339:Spectrometry, Mass, Fast Atom Bombardment
chemical_list: D004164:Diphosphonates; D009842:Oligopeptides; D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; C114893:rhenium-mercaptoacetyltriglycine; D012211:Rhenium