title: Preclinical evaluation of DO3P-AME-DO3P: a polyazamacrocyclic methylene phosphonate for diagnosis and therapy of skeletal metastases.
abstract: A phosphonate derivative 10'-bis(acetamido)-ethane-bis[1,4,7-tri(methylene phosphonic acid)-1,4,7,10-tetraazacyclododecane] (DO3P-AME-DO3P), was synthesized with 90% yield in high purity. It was labeled with (99m)Tc in 97.5% efficiency and specific activity of 112-250 MBq/μmol. The binding affinity of (99m)Tc-DO3P-AME-DO3P towards bone minerals was tested in vitro by using hydroxy apatite as a bone model with absorption of 93% during the first hour of the experiment. Receptor binding assay on human bone cell line SAOS-2 demonstrated K(d) value of 1.07 nM. Cell binding studies of DO3P-AME-DO3P on osteoblasts and osteoclasts cells performed in vitro displayed preferential affinity of the compound towards osteoclast (167.95 ± 3.56% dose/mg protein). The serum stability of (99m)Tc complex was found to be 96.8% after 24 h. Blood kinetics of (99m)Tc-DO3P-AME-DO3P performed on normal rabbits showed fast clearance with t(1/2)(F) = 15 min ± 0.014 min and t(1/2)(S) = 4 h 3 min ± 0.09 min. Biodistribution studies carried out in normal BALB/c mice showed bone-to-blood ratio of 20 and bone-to-muscle ratio of 33. The bone tissue demonstrated highest concentration of bound radioactivity with 10.73% ID/g at 1 h post injection. The protonation and stability constants were determined by pH-potentiometry titrations. The stability constants of DO3P-AME-DO3P with Lu(III), Sm(III), and Ho(III) were 19.7, 21.8, and 20.2 determined by "out of cell" method. The excellent bone seeking properties of DO3P-AME-DO3P make it a candidate of choice for SPECT imaging and preferential uptake of the compound in osteoclasts in comparison to osteoblasts; BMM and BMC can be used to understand the pathway of pathogenesis of osteoporosis and skeletal metastases.
authors.affiliation: Division of Cyclotron and Radiopharmaceutical Sciences, Institute of Nuclear Medicine and Allied Sciences, Defence Research and Development Organization, Brig S K. Mazumdar Road, Delhi 54, India.
authors.forename: Jyoti
authors.initials: J
authors.lastname: Tanwar
authors.forename: Anupama
authors.initials: A
authors.lastname: Datta
authors.forename: Anjani Kumar
authors.initials: AK
authors.lastname: Tiwari
authors.forename: Meganathan
authors.initials: M
authors.lastname: Thirumal
authors.forename: Krishna
authors.initials: K
authors.lastname: Chuttani
authors.forename: Anil Kumar
authors.initials: AK
authors.lastname: Mishra
mesh_terms: D000081:Acetamides / Q000493:pharmacokinetics / Q000627:therapeutic use*; D000818:Animals; D001859:Bone Neoplasms / Q000175:diagnosis* / Q000188:drug therapy*; D002478:Cells, Cultured; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D023421:Models, Animal; D015394:Molecular Structure; D009943:Organophosphorus Compounds / Q000493:pharmacokinetics / Q000627:therapeutic use*; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics / Q000627:therapeutic use*; D011817:Rabbits
chemical_list: C558688:10'-bis(acetamido)-ethane-bis(1,4,7-tri(methylene phosphonic acid)-1,4,7,10-tetraazacyclododecane); D000081:Acetamides; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds