Abstract A160: Combination of necitumumab with second- or third-generation EGFR tyrosine kinase inhibitors downregulates DNA repair mechanisms and induces durable tumor remissions in xenograft NSCLC models with EGFR mutations

First- , second- , and third-generation EGFR tyrosine kinase inhibitors (TKIs) demonstrate profound tumor responses in EGFR mutation-positive NSCLC. Nevertheless, most patients invariably develop acquired resistance. The objective of the present study was to evaluate the effects of dual EGFR blockade using a ligand-blocking antibody (necitumumab) and second- or third-generation TKIs (afatinib or osimertinib) in preclinical NSCLC models with EGFR mutations. Afatinib and osimertinib (AZD9291), second- and third-generation EGFR TKIs, respectively, are irreversible covalent inhibitors of the EGFR tyrosine kinase, with the latter specifically targeting a mutant form of the receptor (EGFR-T790M). We sought to investigate whether combination of necitumumab (LY3012211) with afatinib and osimertinib would provide any benefit over the monotherapies in preclinical mouse models of lung cancer. Using PC-9 and NCI-H1975 xenograft models of NSCLC that harbor EGFR mutations, we observed that dual EGFR blockade of ligand binding and receptor tyrosine kinase activity improved the antitumor efficacy and, more importantly, resulted in durable tumor remissions compared to either single-agent therapy. Additionally, we explored two dosing schedules of necitumumab/osimertinib combination treatment (concurrent versus phased). Concurrent administration of both agents for four weeks was significantly more efficacious compared to the phased schedule (e.g., administration of osimertinib for one week followed by necitumumab and osimertinib combination for additional three weeks). To provide mechanistic insights into the combinatorial activity observed, we employed high-content gene expression analysis using nCounter Pan-Cancer Pathways assay. Pathway analysis of the combination and single-agent treatment groups identified multiple shared and treatment-specific pathway alterations. Genes implicated in FGFR, PI3K pathways and extracellular remodeling appeared to be upregulated by combination and monotherapies and suggested potential common mechanisms of acquired resistance to EGFR inhibitors, whereas compromised DNA repair mechanisms were identified in PC-9 and NCI-H1975 tumors upon treatment with both combinations. In conclusion, these data demonstrate that combination of necitumumab with second- or third-generation EGFR TKIs results in an improved antitumor efficacy compared to the respective monotherapies; a more profound inhibition of EGFR pathway and compromised DNA repair mechanisms may underlie this effect. A phase I clinical trial of necitumumab and osimertinib in EGFR mutation-positive stage IV or recurrent NSCLC who have progressed on a previous EGFR TKI is currently ongoing (NCT02496663). Citation Format: Amelie Forest, Erik R. Rasmussen, Thompson N. Doman, Michael Amatulli, Rajiv Bassi, Gerald E. Hall, Jason R. Manro, Manisha Brahmachary, David Surguladze, Yung-mae M. Yao, Michael D. Kalos, Ruslan D. Novosiadly. Combination of necitumumab with second- or third-generation EGFR tyrosine kinase inhibitors downregulates DNA repair mechanisms and induces durable tumor remissions in xenograft NSCLC models with EGFR mutations [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A160.