Targeting HER2 Aberrations in Non-Small Cell Lung Cancer with Osimertinib.

PURPOSE HER2 (or ERBB2) aberrations, including both amplification and mutations, have been classified as oncogenic drivers that contribute to 2-6 percent of lung adenocarcinomas. HER2 amplification is also an important mechanism for acquired resistance to EGFR tyrosine kinase inhibitors (TKIs). However, due to limited preclinical studies and clinical trials, currently there is still no available standard of care for lung cancer patients with HER2 aberrations. To fulfill the clinical need for targeting HER2 in non-small cell lung cancer (NSCLC) patients, we performed a comprehensive pre-clinical study to evaluate the efficacy of a third-generation TKI, osimertinib (AZD9291).  Experimental Design:Three genetically modified mouse models (GEMMs) mimicking individual HER2 alterations in NSCLC were generated and osimertinib was tested for its efficacy against these HER2 aberrations in vivo. RESULTS Osimertinib treatment showed robust efficacy in HER2wt overexpression and EGFR del19/HER2 models but not in HER2 exon 20 insertion tumors. Interestingly, we further identified that combined treatment with osimertinib and the BET inhibitor JQ1 significantly increased the response rate in HER2-mutant NSCLC while JQ1 single treatment did not show efficacy. CONCLUSIONS Overall, our data indicated robust anti-tumor efficacy of osimertinib against multiple HER2 aberrations in lung cancer, either as a single agent or in combination with JQ1. Our study provides a strong rationale for future clinical trials using osimertinib either alone or in combination with epigenetic drugs to target aberrant HER2 in NSCLC patients.