1909PEvaluation of antibody-dependent cell cytotoxicity (ADCC) in lung cancer cell lines treated with combined anti-EGFR and anti-PD-L1 therapy

Abstract Background Previous studies have demonstrated that IgG1 mAbs as cetuximab, stimulate Antibody-Dependent Cell Cytotoxicity (ADCC). Among immune checkpoint inhibitors, avelumab is the only fully human IgG1 anti-PD-L1 mAb with ADCC properties. Anti-PD-L1 and anti-EGFR mediated NK cytotoxicity is evaluated. Methods LDH release was analyzed to study NK-mediated cytotoxicity by LDH Cytotoxicity Assay Kit and results was correlated to the level of PD-L1, EGFR and MHC-I cell surface expression analyzed by flow cytometry. NK-mediated cytotoxicity of the combination of anti-PD-L1 and anti-EGFR mAbs was studied in a panel of NSCLC cells lines encompassing different tumor types, using as effector NK cells isolated from healthy donors or NSCLC patients. Results PD-L1/EGFR/MHC-I expression levels correlated with enhanced ADCC lysis by the combination of avelumab and cetuximab as demonstrated by LDH assay, CD16 and CD107a mRNA. No significant difference in avelumab plus cetuximab-mediated ADCC between NK cells from healthy donors or from NSCLC patients was observed with a trend in favor of cancer patients, indicating that NK from cancer patients maintain lytic activity. ADCC capability of NK cells isolated from patients enrolled in the phase II study CAVE (Cetuximab-AVElumab)-lung, a single arm phase II clinical study of the combination of avelumab plus cetuximab in the second line treatment of metastatic non small cell lung cancer (NSCLC) patients (EUDRACT 2017- 004195-58) study resulted significantly enhanced after the experimental treatment compared to untreated baseline and healthy donors samples. Conclusions The combination of anti-EGFR and anti PD-L1 IgG1 antibodies is synergistic in terms of ADCC, where each antibody complements each other by promoting a more permissive immune reaction against the tumor, active also in otherwise immune-resistant cancers. Legal entity responsible for the study Universita degli studi della Campania Luigi Vanvitelli. Funding Merck KGaA. Disclosure F. Ciardiello: Advisory / Consultancy, Research grant / Funding (institution): Roche; Advisory / Consultancy, Research grant / Funding (institution): Bayer; Advisory / Consultancy, Research grant / Funding (institution): Amgen; Advisory / Consultancy: Merck; Advisory / Consultancy: Pfizer; Advisory / Consultancy: Sanofi; Advisory / Consultancy: Servier; Advisory / Consultancy: BMS; Advisory / Consultancy: Cellgene; Advisory / Consultancy: Lilly; Research grant / Funding (institution): AstraZeneca; Research grant / Funding (institution): Ipsen. F. Morgillo: Advisory / Consultancy: MSD; Advisory / Consultancy: Lilly; Research grant / Funding (institution): AstraZeneca. All other authors have declared no conflicts of interest.