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

Abstract

Purpose:HER2 (or ERBB2) aberrations, including both amplification and mutations, have been classified as oncogenic drivers that contribute to 2% to 6% of lung adenocarcinomas. HER2 amplification is also an important mechanism for acquired resistance to EGFR tyrosine kinase inhibitors (TKI). 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 patients with non-small cell lung cancer (NSCLC), we performed a comprehensive preclinical study to evaluate the efficacy of a third-generation TKI, osimertinib (AZD9291).Experimental Design: Three genetically modified mouse models (GEMM) mimicking individual HER2 alterations in NSCLC were generated, and osimertinib was tested for its efficacy against these HER2 aberrations in vivoResults: Osimertinib treatment showed robust efficacy in HER2^wt 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, whereas JQ1 single treatment did not show efficacy.Conclusions: Overall, our data indicated robust antitumor 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 patients with NSCLC. Clin Cancer Res; 24(11); 2594-604. ©2018 AACRSee related commentary by Cappuzzo and Landi, p. 2470.

Figure 1.

Overexpression of hHER2 drives development of lung adenocarcinoma. A, Ba/F3-HER2^wt cells stably expressing wild-type human HER2 were treated with either osimertinib or erlotinib for 6 hours at indicated concentrations before pHER2 was detected. B, Ba/F3-HER2^wt cells were plated into 96-well plates and treated with osimertinib and erlotinib for 72 hours, and growth inhibition rate (GI₅₀) was calculated based on the CCK-8 assay. C, Schematic of transgene used to generate tet-op-hHER2 cohort and breeding strategy into tet-op-hHER2/CCSP-rtTA (HW) mice. D, HW mice were fed with either normal diet or with doxy food for 1 week, 5 weeks, or 11 weeks or 5 weeks of doxy then switched to normal diet for 3 days. HER2 expression and phosphorylation were detected in whole-lung lysate samples from these mice. w, week(s). E, Representative MRI images of HW mice fed with doxy food for 6, 12, and 16 weeks. F, H&E staining and IHC analysis for HER2 and pHER2, and adeno/squamous markers TTF1, p63, and SOX2. Scale bar, 100 μm. G, Representative MRI image of an HW mouse fed with doxy food for 14 weeks and then switched to normal food for 2 weeks.

Figure 2.

Osimertinib induces tumor regression in wild-type HER2 GEMMs. A, Representative MRI image of HW mice before and after treatment with vehicle, erlotinib, osimertinib, or afatinib for 4 weeks. B, Waterfall plots show tumor volume change compared with before treatment, and each column represents one individual mouse. C, HW mice were treated with vehicle, osimertinib (Osi), or erlotinib (Erl) for 3 days, and tumor nodules were collected and lysates used in Western blot to detect pHER2 and downstream signaling. Two representative tumor samples from each group are shown.

Figure 3.

Osimertinib demonstrates long-term survival benefit in wild-type HER2 lung cancer. A, Long-term monitoring of tumor volume change with erlotinib or osimertinib in HW mice. B, PFS of HW mice with each treatment. C, OS of HW mice with each treatment.

Figure 4.

Osimertinib induces regression in lung tumors codriven by both EGFR^{del 19} and HER2^wt. A, Breeding scheme of DH mice. B, Long-term tumor change for DH mice following treatment with vehicle, erlotinib, or osimertinib. C, Lungs from two representative mice, one without treatment and another treated with erlotinib for 12 weeks, were harvested. pEGFR, HER2, and pHER2 were examined by IHC. Scale bar, 100 μm. D, PFS of DH mice treated with vehicle, erlotinib, or osimertinib.

Figure 5.

Combined osimertinib and JQ1 therapy suppresses NSCLC with HER2 exon 20 insertions in vitro. A, Ba/F3-HER2^YVMA cells stably expressing human HER2 exon 20 insertion (YVMA) were treated with either osimertinib (Osi) or erlotinib (Erl) for 6 hours at indicated concentrations, and then pHER2 was detected. B, Ba/F3-HER2^YVMA cells were plated into 96-well plates and treated with osimertinib and erlotinib for 3 days. Growth inhibition rate (GI₅₀) was calculated based on the CCK-8 assay. C, H1781 cells were treated with osimertinib and/or JQ1 for indicated time, and then HER2 signaling was evaluated. D, H1781 cells were treated with osimertinib and/or JQ1 for 5 days, and growth rate was measured with CCK-8.

Figure 6.

Osimertinib and JQ1 combination induces tumor regression and long-term survival benefit in HER2^YVMA GEMMs. A and B, SH26 mice were treated with osimertinib, JQ1, or their combination for 2 weeks (A) or for 4 weeks (B), and tumor volume change was calculated compared with before treatment based on MRI quantification. C, PFS of SH26 mice treated with vehicle, osimertinib, JQ1, or combination. P values reported were considered statistically significant: *, P < 0.05; **, P < 0.01; ***, P < 0.001.