title: Direct procedure for the production of 211At-labeled antibodies with an epsilon-lysyl-3-(trimethylstannyl)benzamide immunoconjugate.
abstract: (211)At-labeled tumor-specific antibodies have long been considered for the treatment of disseminated cancer. However, the limited availability of the nuclide and the poor efficacy of labeling procedures at clinical activity levels present major obstacles to their use. This study evaluated a procedure for the direct astatination of antibodies for the production of clinical activity levels.
  
  
  METHODS
  The monoclonal antibody trastuzumab was conjugated with the reagent N-succinimidyl-3-(trimethylstannyl)benzoate, and the immunoconjugate was labeled with astatine. Before astatination of the conjugated antibody, the nuclide was activated with N-iodosuccinimide. The labeling reaction was evaluated in terms of reaction time, volume of reaction solvent, immunoconjugate concentration, and applied activity. The quality of the astatinated antibodies was determined by in vitro analysis and biodistribution studies in nude mice.
  
  
  RESULTS
  The reaction proceeded almost instantaneously, and the results indicated a low dependence on immunoconjugate concentration and applied activity. Radiochemical labeling yields were in the range of 68%-81%, and a specific radioactivity of up to 1 GBq/mg could be achieved. Stability and radiochemical purity were equal to or better than those attained with a conventional 2-step procedure. Dissociation constants for directly astatinated, conventionally astatinated, and radioiodinated trastuzumab were 1.0+/-0.06 (mean+/-SD), 0.44+/-0.06, and 0.29+/-0.02 nM, respectively. The tissue distribution in non-tumor-bearing nude mice revealed only minor differences in organ uptake relative to that obtained with the conventional method.
  
  
  CONCLUSIONS
  The direct astatination procedure enables the high-yield production of astatinated antibodies with radioactivity in the amounts required for clinical applications.
authors.affiliation: Department of Radiation Physics, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. sture.lindegren@radfys.gu.se
authors.forename: Sture
authors.initials: S
authors.lastname: Lindegren
authors.forename: Sofia
authors.initials: S
authors.lastname: Frost
authors.forename: Tom
authors.initials: T
authors.lastname: Bäck
authors.forename: Elin
authors.initials: E
authors.lastname: Haglund
authors.forename: Jörgen
authors.initials: J
authors.lastname: Elgqvist
authors.forename: Holger
authors.initials: H
authors.lastname: Jensen
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000493:pharmacokinetics* / Q000627:therapeutic use; D001246:Astatine / Q000737:chemistry* / Q000493:pharmacokinetics* / Q000627:therapeutic use; D001549:Benzamides / Q000737:chemistry* / Q000493:pharmacokinetics* / Q000627:therapeutic use; D005260:Female; D018796:Immunoconjugates / Q000737:chemistry / Q000493:pharmacokinetics / Q000627:therapeutic use; D007553:Isotope Labeling / Q000379:methods; D008657:Metabolic Clearance Rate; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009928:Organ Specificity; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000493:pharmacokinetics / Q000627:therapeutic use; D014018:Tissue Distribution
chemical_list: D000911:Antibodies, Monoclonal; D001549:Benzamides; D018796:Immunoconjugates; D019275:Radiopharmaceuticals; C037689:benzamide; D001246:Astatine