title: Improved tumor targeting by combined use of two antitenascin antibodies.
abstract: OBJECTIVE
  In the pretargeted antibody-guided radioimmunotherapy (PAGRIT) system, the combined use of two different antibodies directed against the same tumor antigen could represent a valid approach for improving tumor targeting and therapeutic efficacy. We developed a novel monoclonal antitenascin antibody, ST2485, and studied its biochemical and functional properties by in vitro and in vivo assays. We then investigated the first of the three-step therapy combining ST2485 with another antitenascin antibody, ST2146, previously described, to increase accumulation of biotinylated antibodies at the tumor site.
  
  
  METHODS
  Studies of immunoreactivity, affinity, immunohistochemistry, and biodistribution in xenograft model were carried out on ST2485. Analysis of the ST2485 and ST2146 combination was preliminary carried out by ELISA and BiaCore tests and then by in vivo distribution studies after administration of the radiolabeled biotinylated antibodies, followed by a chase with avidin as clearing agent.
  
  
  RESULTS
  ST2485 was found to be a suitable antibody for therapeutic applications. Indeed, for its behavior in all tests, it was comparable with ST2146 and better than BC2, an antibody already used for clinical trials. The additivity of ST2146 and ST2485 in tenascin C binding, shown by in vitro tests, was confirmed by biodistribution studies in a xenograft model where tumor localization of the antibodies was near the sum of each antibody alone, with a tumor-to-blood ratio higher than 24.
  
  
  CONCLUSIONS
  The results reported in this study suggest that a monoclonal antitenascin antibody mixture can improve tumor targeting. This strategy could represent progress for therapeutic approaches such as PAGRIT.
authors.affiliation: Immunology Department, Sigma-Tau SpA R&D, Pomezia, Rome, Italy.
authors.forename: Fiorella
authors.initials: F
authors.lastname: Petronzelli
authors.forename: Angela
authors.initials: A
authors.lastname: Pelliccia
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Anastasi
authors.forename: Valeria
authors.initials: V
authors.lastname: D'Alessio
authors.forename: Claudio
authors.initials: C
authors.lastname: Albertoni
authors.forename: Antonio
authors.initials: A
authors.lastname: Rosi
authors.forename: Barbara
authors.initials: B
authors.lastname: Leoni
authors.forename: Clara
authors.initials: C
authors.lastname: De Angelis
authors.forename: Giovanni
authors.initials: G
authors.lastname: Paganelli
authors.forename: Giovanna
authors.initials: G
authors.lastname: Palombo
authors.forename: Maria
authors.initials: M
authors.lastname: Dani
authors.forename: Paolo
authors.initials: P
authors.lastname: Carminati
authors.forename: Rita
authors.initials: R
authors.lastname: De Santis
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000737:chemistry* / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000737:chemistry; D000918:Antibody Specificity; D000951:Antigens, Neoplasm / Q000737:chemistry; D019921:Biotinylation; D045744:Cell Line, Tumor; D002986:Clinical Trials as Topic; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping; D006801:Humans; D007150:Immunohistochemistry; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000628:therapy*; D010455:Peptides / Q000737:chemistry; D017434:Protein Structure, Tertiary; D016719:Radioimmunodetection / Q000379:methods; D016499:Radioimmunotherapy / Q000379:methods*; D011994:Recombinant Proteins / Q000737:chemistry; D019809:Streptavidin / Q000737:chemistry; D019063:Tenascin / Q000737:chemistry* / Q000276:immunology*; D013997:Time Factors; D014018:Tissue Distribution
chemical_list: D000906:Antibodies; D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D010455:Peptides; D011994:Recombinant Proteins; D019063:Tenascin; D019809:Streptavidin