Development of a feline Cetuximab with therapeutic potential against feline oral squamous cell carcinoma

: Cetuximab is a chimeric murine-human anti-epidermal growth factor receptor (EGFR) monoclonal antibody (mAb) employed in the therapy of head and neck squamous cell carcinoma (HNSCC). Feline oral squamous cell carcinoma (FOSCC), the counterpart of HNSCC, is unresponsive to standard treatments and often lethal for affected cats. As EGFR is highly conserved between humans and cats, our research group attempted to test anti-cancer properties of Cetuximab in EGFR-positive FOSCC preclinical models, obtaining encouraging results in recent work. With the present study, we aimed at generating a "felinized" version of Cetuximab suitable for conducting future clinical trials in cat. A chimeric murine-feline IgG composed of variable regions of clinical Cetuximab fused with feline κ and γ constant regions was successfully generated with molecular biology methods. Immunofluorescence assays showed that the purified feline Cetuximab (f-Cetuximab) efficiently bound to human target in transfected cells (J-EGFR) as well as cancer cells endogenously overexpressing EGFR (MDA-MB-231, CAL-27); additionally, flow cytometry demonstrated that the engineered mAb bound feline EGFR in FOSCC cell lines SCCF1/2/3. Most importantly, f-Cetuximab impaired EGFR activity and inhibited cell proliferation in feline (SCCF1/3) and human (CAL-27) oral SCC cell lines. Moreover, LDH-based assays conducted by co-culturing SCCF3 cells and feline peripheral blood mononuclear cells revealed that f-Cetuximab elicited antibody-dependent cell-mediated cytotoxicity, which might be pivotal for therapeutic efficacy of this mAb in vivo. In conclusion, with this study we established a highly specific and effective candidate for an innovative mAb-based therapeutic approach against FOSCC, paving the way for the introduction of molecular targeted therapy in veterinary oncology.