New insights into acquired resistance mechanisms to third-generation EGFR tyrosine kinase inhibitor therapy in lung cancer

Background: The emergence of acquired resistance (AR) against third-generation epidermal growth factor receptor tyrosine kinase inhibitors (TKI) remain a major clinical challenge in lung adenocarcinoma patients. Here we characterized the role of acquired resistance mechanism with a focus on inter-individual heterogeneity and co-occurring genetic aberrations. We could analyze pre- and post-treatment samples of patients treated with third-generation EGFR TKIs. Methods: We characterized 128 patients, which are EGFR p.T790M positive to early generation EGFR TKIs within thedatabases of the Network Genomic Medicine (NGM), the NOWEL network, the Department of Thoracic Oncology of the Netherlands Cancer Institute and the Vall d’Hebron University Hospital. In 60 patients, corresponding analyses of third generation EGFR TKI treatment outcomes and molecular analyses were practicable. Results: Co-occurring aberrations were found in 75% of the samples with acquired resistance to early-generation TKI. TP53mutations were the most frequent aberrations detected. In MET, copy number variants were found (n = 6). In a subgroup, we identified 4 patients with the new EGFRresistance mutation p.G724S after third-generation TKI treatment. Still, loss of the EGFRp.T790M mutation and METamplification are the most common aberrations after third-generation TKI treatment. Conclusions: EGFR inhibitors represent a powerful tool for precision cancer medicine in genetically selected patients. We could show in this study that additional genetic aberrations are frequent in the setting of AR to EGFR TKIs and may mediate innate and acquired resistance to third-generation EGFR TKIs. Amplification of METwas strongly associated with primary treatment failure and thus the strongest factor in innate resistance. AR to third-generation EGFR TKI (p.G724S) can possibly be overcome with second-generation EGFR TKI. Legal entity responsible for the study: The authors. Funding: Deutsche Forschungsgemeinschaft, Cluster of Excellence RESOLV, the Bundesministerium für Bildung und Forschung, Else Kröner-Fresenius Stiftung, Deutsche Krebshilfe, European Union, (NRW) as part of the EFRE initiative (EMODI, grant no. EFRE-0800397 to R.B. and M.L.S.) and by the German Ministry of Science and Education (BMBF) as part of the e:Med program (grant no. 01ZX1303A to R.B. and J.W). E.F. received funding by the Instituto de Salud Carlos III (PI17/00938), NEGECA, ITMC of TU Dortmund. Disclosure: J. Fassunke: Honoraria: AstraZeneca. C. Heydt, S. Merkelbach-Bruse: Speaking honoraria: AstraZeneca. J. Wolf: Consulting, lecture fees: AbbVie, AstraZeneca, BMS, Boehringer Ingelheim, Chugai, Ignyta, Lilly, MSD, Novartis, Pfizer, Roche; Funding for scientific research: BMS, Johnson&Johnson, MSD, Novartis, Pfizer. R. Buettner: Employee: Targos Molecular Pathology. M.L. Sos: Commercial research grant: Novartis. D. Rauh: Consultant, lecture fees: AstraZeneca, Merck-Serono, Takeda, Pfizer, Novartis, Boehringer Ingelheim, Sanofi-Aventis. All other authors have declared no conflicts of interest.