Tumor targeting with newly designed biparatopic antibodies directed against two different epitopes of the carcinoembryonic antigen (CEA)
✍ Scribed by Bruno Robert; Mylène Dorvillius; Franz Buchegger; Véronique Garambois; Jean-Claude Mani; Martine Pugnières; Jean-Pierre Mach; André Pèlegrin
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- French
- Weight
- 89 KB
- Volume
- 81
- Category
- Article
- ISSN
- 0020-7136
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✦ Synopsis
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 FabЈ 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 crossinhibition 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 ؋ 10 9 M ؊1 for the 4 parental F(abЈ) 2 fragments and from 1.88 to 10.14 ؋ 10 9 M ؊1 for the BpAbs, demonstrating the advantage of biparatopic binding over conventional F(abЈ) 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(abЈ) 2 . In vivo, the 6 BpAbs were compared with their 2 respective parental F(abЈ) 2 by injection of 131 I-BpAb/ 125 I-F(abЈ) 2 parental fragments into nude mice xenografted with the human colon carcinoma T380. Dissection 72 hr postinjection demonstrated that BpAb B17/CE25 and BpAb F6/ B17 gave higher tumor uptake than that of their parental F(abЈ) 2 . This finding is particularly interesting for BpAb F6/B17, which compared favorably with the F6 F(abЈ) 2 , one of the best parental F(abЈ) 2 fragments used in our study. Int.