title: Tumor targeting with newly designed biparatopic antibodies directed against two different epitopes of the carcinoembryonic antigen (CEA).
abstract: In an attempt to improve tumor targeting and tumor retention time of monoclonal antibodies (MAbs), we prepared biparatopic antibodies (BpAbs) having the capability of binding 2 different non-overlapping epitopes on the same target antigen molecule, namely, the carcinoembryonic antigen (CEA). Six BpAbs were constructed by coupling 2 different Fab' fragments from 4 different specific anti-CEA MAbs recognizing 4 CEA epitopes (Gold 1-4). Demonstration of the double paratopic binding of these antibodies for CEA was confirmed in vitro by inhibition radioimmunoassay and cross-inhibition analysis by surface plasmon resonance (SPR; BIACORE) technology. Using the latter technique, the affinity constants for CEA immobilized onto the sensor chip were found to range from 0.37 to 1.54 x 10(9) M(-1) for the 4 parental F(ab')2 fragments and from 1.88 to 10.14 x 10(9) M(-1) for the BpAbs, demonstrating the advantage of biparatopic binding over conventional F(ab')2 binding. The Ka improvement was particularly high for BpAb F6/35A7 and BpAb F6/B17 with a 9.5- and 8.1-fold increase, respectively, as compared with the parental F(ab')2. In vivo, the 6 BpAbs were compared with their 2 respective parental F(ab')2 by injection of 131I-BpAb/125I-F(ab')2 parental fragments into nude mice xenografted with the human colon carcinoma T380. Dissection 72 hr post-injection demonstrated that BpAb B17/CE25 and BpAb F6/B17 gave higher tumor uptake than that of their parental F(ab')2. This finding is particularly interesting for BpAb F6/B17, which compared favorably with the F6 F(ab')2, one of the best parental F(ab')2 fragments used in our study.
authors: Cancer Research Center, Institute Val d'Aurelle-Paul Lamarque, Montpellier, France.
authors: B
authors: B
authors: Robert
authors: M
authors: M
authors: Dorvillius
authors: F
authors: F
authors: Buchegger
authors: V
authors: V
authors: Garambois
authors: J C
authors: JC
authors: Mani
authors: M
authors: M
authors: Pugnières
authors: J P
authors: JP
authors: Mach
authors: A
authors: A
authors: Pèlegrin
mesh_terms: D000818:Animals; D018033:Antibodies, Bispecific / Q000276:immunology*; D000911:Antibodies, Monoclonal; D002272:Carcinoembryonic Antigen / Q000276:immunology*; D000939:Epitopes / Q000276:immunology*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007700:Kinetics; D051379:Mice; D008819:Mice, Nude; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
chemical_list: D018033:Antibodies, Bispecific; D000911:Antibodies, Monoclonal; D002272:Carcinoembryonic Antigen; D000939:Epitopes; D007140:Immunoglobulin Fab Fragments