title: Bifunctional (64)Cu-labelled macrobicyclic cage amine isothiocyanates for immuno-positron emission tomography.
abstract: New macrobicyclic cage amine or "sarcophagine" (sar) bifunctional chelators have been synthesised that form copper complexes of exceptional in vivo stability and incorporate isothiocyanate (-NCS) functional groups for conjugation to an antibody. The chelators were synthesised from the methyl-capped complex [Mg(II)(CH3)(NH2)sar](2+). Coordination of Mg(II) within the cavity of the cage amine ligand protects the secondary amine atoms from reacting with the -NCS functional groups. Two different [Mg(II)(NCS-sar)](2+) derivatives were conjugated to the HER2/neu-targeting antibody trastuzumab and the progress of the reaction monitored by electrospray mass spectrometry. The Mg(II) ion was removed from the immunoconjugates under mild conditions (0.1 M citrate buffer, pH 6). Labelling of the (CH3)(p-NCS-Ph)sar-trastuzumab conjugate with (64)Cu(II), a radioisotope suitable for positron emission tomography (PET), was fast (∼5 min) and easily performed at room temperature with high radiochemical purity (>95%). Biodistribution and PET imaging studies in vivo showed that (64)Cu-labelled (CH3)(p-NCS-Ph)sar-trastuzumab maintained high stability under physiological conditions with high and selective uptake in a HER2-positive cancer cell line. The stability of the copper complex and the 12.7 h half-life of the radioisotope allows clear visualisation of tumours out to 48 h.
authors.affiliation: School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC, Australia. brettp@unimelb.edu.au pauld@unimelb.edu.au.
authors.forename: Brett M
authors.initials: BM
authors.lastname: Paterson
authors.forename: Gojko
authors.initials: G
authors.lastname: Buncic
authors.forename: Lachlan E
authors.initials: LE
authors.lastname: McInnes
authors.forename: Peter
authors.initials: P
authors.lastname: Roselt
authors.forename: Carleen
authors.initials: C
authors.lastname: Cullinane
authors.forename: David S
authors.initials: DS
authors.lastname: Binns
authors.forename: Charmaine M
authors.initials: CM
authors.lastname: Jeffery
authors.forename: Roger I
authors.initials: RI
authors.lastname: Price
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Hicks
authors.forename: Paul S
authors.initials: PS
authors.lastname: Donnelly
mesh_terms: D000588:Amines / Q000737:chemistry*; D000818:Animals; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000737:chemistry; D003301:Copper Radioisotopes; D004355:Drug Stability; D006801:Humans; D018796:Immunoconjugates / Q000737:chemistry / Q000493:pharmacokinetics; D017879:Isothiocyanates / Q000737:chemistry*; D007553:Isotope Labeling; D047028:Macrocyclic Compounds / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry; D008325:Mammary Neoplasms, Experimental / Q000000981:diagnostic imaging / Q000378:metabolism; D051379:Mice; D049268:Positron-Emission Tomography / Q000379:methods*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D000068878:Trastuzumab / Q000737:chemistry
chemical_list: D000588:Amines; D002614:Chelating Agents; D003301:Copper Radioisotopes; D018796:Immunoconjugates; D017879:Isothiocyanates; D047028:Macrocyclic Compounds; D008274:Magnesium; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; C037152:isothiocyanic acid; C508053:ERBB2 protein, human