title: The ionic charge of copper-64 complexes conjugated to an engineered antibody affects biodistribution.
abstract: The development of biomolecules as imaging probes requires radiolabeling methods that do not significantly influence their biodistribution. Sarcophagine (Sar) chelators form extremely stable complexes with copper and are therefore a promising option for labeling proteins with (64)Cu. However, initial studies using the first-generation sarcophagine bifunctional chelator SarAr to label the engineered antibody fragment ch14.18-ΔCH2 (MW 120 kDa) with (64)Cu showed high tracer retention in the kidneys, presumably because the high local positive charge on the Cu(II)-SarAr moiety resulted in increased binding of the labeled protein to the negatively charged basal cells of the glomerulus. To test this hypothesis, ch14.18-ΔCH2 was conjugated with a series of Sar derivatives of decreasing positive charge and three commonly used macrocyclic polyaza polycarboxylate (PAC) bifunctional chelators (BFC). The immunoconjugates were labeled with (64)Cu and injected into mice, and PET/CT images were obtained at 24 and 48 h postinjection (p.i.). At 48 h p.i., ex vivo biodistribution was assessed. In addition, to demonstrate the potential of metastasis detection using (64)Cu-labeled ch14.18-ΔCH2, a preclinical imaging study of intrahepatic neuroblastoma tumors was performed. Reducing the positive charge on the Sar chelators decreased kidney uptake of Cu-labeled ch14.18-ΔCH2 by more than 6-fold, from >45 to <6% ID/g, whereas the uptake in most other tissues, including liver, was relatively unchanged. However, despite this dramatic decrease, the renal uptake of the PAC BFCs was generally lower than that of the Sar derivatives, as was the liver uptake. Uptake of (64)Cu-labeled ch14.18-ΔCH2 in neuroblastoma hepatic metastases was detected using PET.
authors.affiliation: †Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Boston Children's Hospital, Boston, Massachusetts 02115, United States.|‡Harvard Medical School, Boston, Massachusetts 02115, United States.
authors.forename: Jason L J
authors.initials: JL
authors.lastname: Dearling
authors.affiliation: §School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC 3010, Australia.
authors.forename: Brett M
authors.initials: BM
authors.lastname: Paterson
authors.affiliation: †Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Boston Children's Hospital, Boston, Massachusetts 02115, United States.|‡Harvard Medical School, Boston, Massachusetts 02115, United States.
authors.forename: Vamsidhar
authors.initials: V
authors.lastname: Akurathi
authors.affiliation: †Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Boston Children's Hospital, Boston, Massachusetts 02115, United States.
authors.forename: Soledad
authors.initials: S
authors.lastname: Betanzos-Lara
authors.affiliation: †Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Boston Children's Hospital, Boston, Massachusetts 02115, United States.|‡Harvard Medical School, Boston, Massachusetts 02115, United States.
authors.forename: S Ted
authors.initials: ST
authors.lastname: Treves
authors.affiliation: †Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Boston Children's Hospital, Boston, Massachusetts 02115, United States.|‡Harvard Medical School, Boston, Massachusetts 02115, United States.
authors.forename: Stephan D
authors.initials: SD
authors.lastname: Voss
authors.affiliation: §School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC 3010, Australia.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: White
authors.forename: James S
authors.initials: JS
authors.lastname: Huston
authors.affiliation: #Brookhaven National Laboratory, Upton, New York 11973, United States.
authors.forename: Suzanne V
authors.initials: SV
authors.lastname: Smith
authors.affiliation: §School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC 3010, Australia.
authors.forename: Paul S
authors.initials: PS
authors.lastname: Donnelly
authors.affiliation: †Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Boston Children's Hospital, Boston, Massachusetts 02115, United States.|‡Harvard Medical School, Boston, Massachusetts 02115, United States.
authors.forename: Alan B
authors.initials: AB
authors.lastname: Packard
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry*; D001372:Aza Compounds / Q000737:chemistry; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000737:chemistry; D003301:Copper Radioisotopes / Q000737:chemistry*; D004151:Dipeptides / Q000737:chemistry; D005260:Female; D018796:Immunoconjugates / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics*; D007668:Kidney / Q000000981:diagnostic imaging / Q000378:metabolism / Q000648:ultrastructure; D008099:Liver / Q000000981:diagnostic imaging / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D008819:Mice, Nude; D015335:Molecular Probes / Q000138:chemical synthesis / Q000378:metabolism / Q000493:pharmacokinetics*; D009362:Neoplasm Metastasis; D009368:Neoplasm Transplantation; D009447:Neuroblastoma / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000648:ultrastructure; D009928:Organ Specificity; D049268:Positron-Emission Tomography; D015202:Protein Engineering; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000378:metabolism / Q000493:pharmacokinetics*; D055672:Static Electricity
chemical_list: D000911:Antibodies, Monoclonal; D001372:Aza Compounds; D002614:Chelating Agents; D003301:Copper Radioisotopes; D004151:Dipeptides; D018796:Immunoconjugates; D015335:Molecular Probes; D019275:Radiopharmaceuticals; C016968:alanyltyrosine; C112746:dinutuximab