title: The humoral immune response to macrocyclic chelating agent DOTA depends on the carrier molecule.
abstract: The chelating agent 1,4,7,10-tetraazacyclododecane-N,N', N",N"'-tetraacetic acid (DOTA) is used to label monoclonal antibodies (mAbs) and peptides with (90)Y. DOTA allows the generation of clinically useful stable metallic radioconjugates for the treatment of a variety of tumors, but its immunogenicity has remained controversial. In this study, we evaluated the immune response to DOTA in a preclinical mouse model and in patients entered in a clinical trial.
  
  
  METHODS
  Sera were obtained from BALB/c mice injected intraperitoneally or subcutaneously with different doses and formulations of syngeneic and xenogeneic mAbs or peptide (murine mAb Mov19 [mM19]; its chimeric version; murine V/human C ChiMov19 [cM19]; or Tyr(3)-octreotide)-DOTA conjugates. Sera from patients with neuroendocrine tumors, enrolled in a protocol for somatostatin receptor-mediated radionuclide therapy with (90)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide (DOTATOC), were also collected before and after each treatment. Levels and specificity of antibody response to relevant (Mov19, ChiMov19, or Tyr(3)-octreotide) and nonrelevant (human serum albumin) DOTA targets were tested by enzyme-linked immunosorbent assay and competition assays. An anti-DOTA mAb (IgG1) derived from a ChiMov19-DOTA immunized mouse was used, in a competitive radioimmunoassay, to determine the efficiency of DOTA presentation on the different carriers.
  
  
  RESULTS
  Depending on the immunogenicity and dosage of the mAb, a specific anti-DOTA response was revealed in the preclinical system. However, DOTA-peptide conjugate induced no immune-detectable response against either chelator or carrier. DOTA was poorly presented on small peptides, as determined using the anti-DOTA mAb.
  
  
  CONCLUSIONS
  A humoral response against DOTA is possible, but only as a consequence of the response elicited against the carrier. Octreotide was not immunogenic. Thus, (90)Y-DOTATOC can be considered a safe and useful tool for receptor-mediated radionuclide therapy of somatostatin receptor-overexpressing tumors.
authors.affiliation: Unit of Molecular Therapies, Department of Experimental Oncology, Istituto Nazionale Tumori, Milan, Italy.
authors.forename: M E
authors.initials: ME
authors.lastname: Perico
authors.forename: M
authors.initials: M
authors.lastname: Chinol
authors.forename: A
authors.initials: A
authors.lastname: Nacca
authors.forename: E
authors.initials: E
authors.lastname: Luison
authors.forename: G
authors.initials: G
authors.lastname: Paganelli
authors.forename: S
authors.initials: S
authors.lastname: Canevari
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000917:Antibody Formation / Q000276:immunology*; D001710:Biotin / Q000031:analogs & derivatives* / Q000276:immunology*; D002614:Chelating Agents / Q000737:chemistry*; D004337:Drug Carriers; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D018358:Neuroendocrine Tumors / Q000532:radiotherapy; D009942:Organometallic Compounds / Q000276:immunology*; D019275:Radiopharmaceuticals / Q000276:immunology* / Q000627:therapeutic use
chemical_list: D000911:Antibodies, Monoclonal; D002614:Chelating Agents; C405616:DOTA-biotin; D004337:Drug Carriers; D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; D001710:Biotin