Abstract 3632: Combination of EGFR antibody with PD-1 pathway inhibitors improves anti-tumor efficacy and enhances intra-tumor immune response in preclinical mouse tumor models

Necitumumab (EGFR inhibitor) in combination with chemotherapy provides a modest, yet a significant improvement in overall survival over chemotherapy alone in patients with advanced squamous non-small cell lung carcinoma (NSCLC). However, combination therapies targeting EGFR and PD-1 pathway blockers may represent a better way to extend clinical benefit to more cancer patients given that PD-(L)1 antibodies have emerged as a standard of care in NSCLC. Antibodies targeting EGFR have the potential to promote an inflamed tumor microenvironment through engagement of Fc-gamma receptors (FcγR) on innate immune cells resulting in an improved antigen presentation and T cell priming. Therefore, the present study was initiated to understand the combinatorial effect of immune checkpoint (PD-(L)1) inhibitors with necitumumab. Preclinical modeling of EGFR/PD-(L)1 mAb combination in mice is challenging due to the lack of cross-reactivity of necitumumab with mouse EGFR. Syngeneic mouse tumor models widely used to study effects of immunomodulatory agents express low or no EGFR. To overcome this limitation, we used two immunocompetent model systems to study the combination effect of EGFR mAb with PD-1 (RMP1-14) or PD-L1 (178G7) mAbs: 1) genetically engineered mouse model of lung adenocarcinoma (TD model) driven by mutant forms of human EGFR (exon 19 deletion and T790M mutation) and 2) CT26 syngeneic mouse tumor model with ectopic expression of human EGFR (CT26-hEGFR). To engage mouse immune cells more efficiently, a murinized version of necitumumab was generated through antibody engineering, with human EGFR binding Fabs and a mouse Fc backbone. Intratumor immune response was evaluated by immunohistochemistry and a custom-made immune profiling Quantigene Plex (QGP) gene expression panel. In both models, targeting EGFR and PD-1 pathway resulted in the combinatorial antitumor efficacy exemplified by decreased tumor burden compared to the monotherapy groups. QGP analysis of CT26-hEGFR tumor tissue revealed that the combination treatment enhanced intra-tumor immune response exemplified by an upregulation of immune-related genes indicative of T cell infiltration (Cd3e, Cd4, Cd8b1), T cell activation (Ifng, Cd274, Pdcd1lg2, Icos, Tnfrsf4, Tnfrsf18, Cd69, Ido1, Havcr2, Lag3), myeloid cell infiltration (Cd86, Timd4, Vista, Cd68, Mpo, Nos2). Histopathological analysis confirmed an increase in T cell infiltration indicating an improved immune response in the combination therapy group.