title: Novel chelating agents for potential clinical applications of copper.
abstract: Copper offers a unique selection of radioisotopes ((60)Cu, (61)Cu, (62)Cu, (64)Cu, and (67)Cu) with half-lives ranging from 9.8 min to 61.9 h suitable for imaging and/or radiotherapy. In peptide/antibody targeted radiotherapy one of the most studied chelating agents for copper, 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid (TETA), has been employed in clinical trials, but transchelation to ceruloplasmin and/or superoxide dismutase in vivo has been noted. In this study, a series of novel hexadentate chelating agents based on N,N',N"-tris(2-pyridylmethyl)-1,3,5-cis,cis,-triaminocyclohexane (tachpyr) have been synthesized and the serum stability of their copper complexes was evaluated as compared to TETA. Copper complexes of tachpyr modified at the 3, 4, or 5 position or with replacement of pyridine by imidazole have serum stability comparable to Cu[TETA]. When the complexes were cross-challenged, Cu[TETA] versus tachpyr or 1,3,5-cis,cis,-triaminocyclohexane- N,N',N"-tris-(2-methyl-(N-methylimidazole)) (IM), tachpyr and IM appear to have superior copper chelation ability to TETA. When challenged by a large excess of non-radioactive copper, copper exchange with the tachpyr radio-copper complex was observed. However, tachpyr clearly exhibited a significant preference for Cu(II) over Zn(II) or Fe(III). Therefore, tachpyr, 1,3,5-cis,cis,-triaminocyclohexane-N,N',N"-tri-(3-methyl-2-methylpyridineimine) (tachpyr(3-Me)), 1,3,5-cis,cis,-triaminocyclohexane-N,N',N"-tri-(4-methyl-2-methylpyridineimine) (tachpyr(4-Me)), 1,3,5-cis,cis,-triaminocyclohexane-N,N',N"-tri-(5-methyl-2-methylpyridineimine) (tachpyr(5-Me)) and IM easily form copper complexes with high stability. These novel chelating agents provide an attractive lead for creation of new copper radiopharmaceuticals for diagnosis and therapy applications.
authors.affiliation: Radioimmune & Inorganic Chemistry Section, Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Building 10, Room B3B69, 9000 Rockville Pike, Bethesda, MD 20892, USA.
authors.forename: Dangshe
authors.initials: D
authors.lastname: Ma
authors.forename: Francis
authors.initials: F
authors.lastname: Lu
authors.forename: Terrish
authors.initials: T
authors.lastname: Overstreet
authors.forename: Diane E
authors.initials: DE
authors.lastname: Milenic
authors.forename: Martin W
authors.initials: MW
authors.lastname: Brechbiel
mesh_terms: D002614:Chelating Agents / Q000138:chemical synthesis / Q000493:pharmacokinetics / Q000627:therapeutic use; D003301:Copper Radioisotopes; D004355:Drug Stability; D006801:Humans; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000493:pharmacokinetics / Q000627:therapeutic use
chemical_list: D002614:Chelating Agents; D003301:Copper Radioisotopes; D019275:Radiopharmaceuticals