Abstract 5863: Enhanced antitumor activity of zipalertinib and amivantamab combination in EGFR mutant NSCLC models

Abstract Zipalertinib is a selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) that targets mutations in exon 20 insertions (ex20ins) and has demonstrated clinical efficacy in patients with EGFR ex20ins-positive non-small cell lung cancer (NSCLC), including those previously treated with amivantamab and chemotherapy. Currently, amivantamab plus platinum-based chemotherapy is the standard first-line treatment for NSCLC harboring EGFR ex20ins. However, efficacy of EGFR-TKIs combined with amivantamab in EGFR ex20ins positive patient remains unclear. In this preclinical study, we aimed to investigate the therapeutic potential of zipalertinib and amivantamab combination therapy. EGFR mutant cell lines NCI-H1975, H1975insSVD (EGFR D770_N771insSVD), II-18 (EGFR L858R), and HCC827OR8 (EGFR del19 with MET amplification) were used for in vitro and in vivo experiments. The binding of amivantamab to the cell surface was quantified in the presence or absence of zipalertinib. An antibody-dependent cellular cytotoxicity (ADCC) assay was conducted using H1975insSVD cells cocultured with peripheral blood mononuclear cells (PBMCs) to assess amivantamab-mediated cytotoxicity with or without zipalertinib treatment. In vivo antitumor efficacy was evaluated using human cell-derived xenograft (CDX) mouse models, and tumor volumes were analyzed for statistical significance using the Aspin-Welch’s t-test. Zipalertinib treatment increased EGFR protein expression and enhanced amivantamab binding to the cell surface. Amivantamab induced ADCC in H1975insSVD cells cocultured with PBMCs, and zipalertinib co-treatment further potentiated this cytotoxicity. Additionally, compared to zipalertinib monotherapy, the combination of zipalertinib and amivantamab exhibited significant antitumor efficacy (p < 0.05) across all three CDX models, without notable changes in body weight. Complete tumor regression was observed in the H1975insSVD CDX model. Zipalertinib upregulates EGFR protein expression and enhances amivantamab binding to the cell surface. These results provide mechanistic insights into the observed combinatorial efficacy of zipalertinib and amivantamab, both in vitro and in vivo. Further, our findings support the therapeutic potential of zipalertinib and amivantamab in EGFR-mutant NSCLC and further clinical investigations. Citation Format: Kohei Hayashi, Yoshimi Aoyagi, Akihiro Hashimoto, Tomoaki Hitotsumachi, Shuichi Ohkubo, . Enhanced antitumor activity of zipalertinib and amivantamab combination in EGFR mutant NSCLC models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 5863.