Targeting Exon 20 Insertion-Mutant Lung Adenocarcinoma with a Novel Tyrosine Kinase Inhibitor Mobocertinib.

No targeted treatments are currently approved for exon 20 insertion-mutant lung adenocarcinoma patients. Mobocertinib (TAK-788) is a potent irreversible tyrosine kinase inhibitor (TKI) designed to target human epidermal growth factor receptor 2 () exon 20 insertion mutations. However, the function of mobocertinib on exon 20 insertion-mutant lung cancer is still unclear. Here we conducted systematic characterization of preclinical models to understand the activity profile of mobocertinib against exon 20 insertions. In exon 20 insertion-mutant cell lines, the IC of mobocertinib was higher than poziotinib and comparable with or slightly lower than afatinib, neratinib, and pyrotinib. Mobocertinib had the lowest HER2 exon 20 insertion IC/wild-type (WT) EGFR IC ratio, indicating that mobocertinib displayed the best selectivity profile in these models. Also, mobocertinib showed strong inhibitory activity in exon 20 allograft and patient-derived xenograft models. In genetically engineered mouse models, exon 20 lung tumors exhibited a sustained complete response to mobocertinib, whereas exon 20 tumors showed only partial and transient response. Combined treatment with a second antibody-drug conjugate (ADC) against , ado-trastuzumab emtansine (T-DM1), synergized with mobocertinib in exon 20 tumors. In addition to the tumor cell autonomous effect, sustained tumor growth control derived from M1 macrophage infiltration and CD4 T-cell activation. These findings support the ongoing clinical development of mobocertinib (NCT02716116) and provide a rationale for future clinical evaluation of T-DM1 combinational therapy in exon 20 insertion-mutant lung adenocarcinoma patients. SIGNIFICANCE: This study elucidates the potent inhibitory activity of mobocertinib against exon 20 insertion-mutant lung cancer and the synergic effect of combined mobocertinib and T-DM1, providing a strong rationale for clinical investigation.