Résumé
BACKGROUND: Monoclonal antibodies (mAbs) are an important part of targeted therapies in many fields and particularly in cancerology by reaching their targets overexpressed on tumour cells (“on target - on tumour”). However, most of these targets are also expressed at basal level by healthy tissues generating some toxicities (“on target - off tumour”). Moreover, the diffusion of antibodies in the tumour is a poorly studied subject and closely related to the targeting efficiency of the mAb. Affinity antibody properties for their targets is a key component of this targeting efficiency.The aim of this project is to study the role of antibody affinity/avidity in tumour binding, diffusion and in the decrease of “on target - off tumour”.METHOD: We developed a range of human antibodies by phage display processing on human EGFR target with different affinity levels checked by enzyme-linked immunosorbent assay (ELISA). We concluded this in vitro validation by cytometry assays on cell lines characterized by a gradient of EGFR level (from 103 to 106 receptors/cells).RESULTS: Phage display processing allowed us to select and produce 6 human antibodies specifically directed against human EGFR. In vitro, using ELISA, we ranked these antibodies produced as full IgG format as low, medium and high affinity against EGFR compare with the high affinity positive control Cetuximab and Panitumumab. Cytometry experiments on the different cell lines showed that only medium affinity level antibodies could bind overexpressed EGFR cell lines but not cell lines with medium and low expression of EGFR (that could mimic healthy tissues).PERSPECTIVES: Next, our hypothesis will be confirmed in vivo. Antibodies will be screened by IHC and then they will be radiolabelled with Zirconium-89 to perform non-invasive quantitative bio distribution study with Positron Emission Tomography. On both tumor xenograft and “healthy tissue”, the binding and diffusion of antibodies will be quantified.