title: Full preclinical validation of the 123I-labeled anti-PSMA antibody fragment ScFvD2B for prostate cancer imaging.
abstract: OBJECTIVE
  In the context of prostate cancer (PCa) imaging, the aim of this study was to optimize (in vitro) the specificity and assess preclinically (in vivo) the tumor targeting properties of the 123I-scFvD2B antibody specific for prostate-specific membrane antigen (PSMA).
  
  
  METHODS
  The 123I-labeling conditions of the antibody fragment scFvD2B, produced in an eukaryotic system under GMP-compliant conditions, were optimized and assessed for purity and immunoreactivity. The specificity and potency of tumor uptake were tested in three preclinical in vivo models of subcutaneously xenografted human tumors expressing different levels of PSMA (LNCaP, naturally expressing PSMA; PC3-PIP and LS174T-PSMA, transfected with PSMA) or PC3 and LS174T, as negative controls, to assess the clearance, biodistribution and imaging potential of 123I-scFvD2B.
  
  
  RESULTS
  The set conditions of production and radiolabeling yielded a reagent suitable for human delivery thanks to the purity of the formulation and the high immunoreactivity. In all preclinical models 123I-scFvD2B showed specific targeting only to PSMA-positive tumors with the final specific activity ranging up to 1500 MBq/mg. Despite different levels of PSMA expression, biodistribution analyses and SPECT/CT imaging demonstrated similar results and maximal signal-to-background ratios 24 hours after injection.
  
  
  CONCLUSIONS
  Due to its in vitro and in vivo properties, 123I-scFvD2B could be a promising tool for the early diagnosis of PCa, and may represent a molecular imaging option to monitor disease progression and assist in the clinical management of PCa patients.
authors.affiliation: Department of Experimental Oncology and Molecular Medicine, S.S. Molecular Therapies, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Frigerio
authors.affiliation: Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Gerben
authors.initials: G
authors.lastname: Franssen
authors.affiliation: Department of Experimental Oncology and Molecular Medicine, S.S. Molecular Therapies, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Luison
authors.affiliation: Department of Experimental Oncology and Molecular Medicine, S.S. Molecular Therapies, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Satta
authors.affiliation: S.C. Nuclear Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Ettore
authors.initials: E
authors.lastname: Seregni
authors.affiliation: Department of Medicine, University of Verona, Verona, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Colombatti
authors.affiliation: Department of Medicine, University of Verona, Verona, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: Fracasso
authors.affiliation: Department of Oncology and Hemato-Oncology, Università degli Studi di Milano, Radiation Oncology 1, Prostate Cancer Program, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Valdagni
authors.affiliation: Department of Experimental Oncology and Molecular Medicine, S.S. Molecular Therapies, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Delia
authors.initials: D
authors.lastname: Mezzanzanica
authors.affiliation: Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Otto
authors.initials: O
authors.lastname: Boerman
authors.affiliation: Department of Experimental Oncology and Molecular Medicine, S.S. Molecular Therapies, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Silvana
authors.initials: S
authors.lastname: Canevari
authors.affiliation: Department of Experimental Oncology and Molecular Medicine, S.S. Molecular Therapies, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Mariangela
authors.initials: M
authors.lastname: Figini
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000276:immunology / Q000378:metabolism*; D045744:Cell Line, Tumor; D043425:Glutamate Carboxypeptidase II / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics; D008297:Male; D008819:Mice, Nude; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D000072098:Single Photon Emission Computed Tomography Computed Tomography / Q000379:methods*; D057127:Single-Chain Antibodies / Q000276:immunology / Q000493:pharmacokinetics*; D014018:Tissue Distribution; D014183:Transplantation, Heterologous
chemical_list: D000954:Antigens, Surface; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D057127:Single-Chain Antibodies; C473848:FOLH1 protein, human; D043425:Glutamate Carboxypeptidase II
keywords: 123I-radiolabeled antibody; imaging; prostate cancer; prostate-specific membrane antigen; scFv antibody fragment