Overcoming EGFRG724S-mediated osimertinib resistance through unique binding characteristics of second-generation EGFR inhibitors

Jana Fassunke,Johannes Brägelmann,Ernst Rodermann,Michael Püsken,Jürgen Wolf,Fabienne Müller,Reinhard Büttner,Michaela A Ihle,Ilona Dahmen,Yannic Alber,Anna Schmitt,Hans Christian Reinhardt ,Stefan M Kast,Konrad Frank,Marina Keul,Vanessa Priesner,Daniel Rauh,Carina Heydt,Egbert F Smit,Sebastian Michels,Hannah L Tumbrink,Alena Heimsoeth,Katia Garbert,Thorsten Persigehl,Bernhard Schaaf,Enriqueta Felip,Andreas H Scheel,Svenja Wagener,Dennis Plenker,Stefan Haneder,Matthias Scheffler,Marcel A Dammert,Sebastian Klein,Anna Kron,Jonas Lategahn,Rudolf‐Josef Fischer ,Sabine Merkelbach‐Bruse ,Walburga Engel-Riedel,Martin L Sos

doi:10.1038/s41467-018-07078-0

Abstract

The emergence of acquired resistance against targeted drugs remains a major clinical challenge in lung adenocarcinoma patients. In a subgroup of these patients we identified an association between selection of EGFRT790M-negative but EGFRG724S-positive subclones and osimertinib resistance. We demonstrate that EGFRG724S limits the activity of third-generation EGFR inhibitors both in vitro and in vivo. Structural analyses and computational modeling indicate that EGFRG724S mutations may induce a conformation of the glycine-rich loop, which is incompatible with the binding of third-generation TKIs. Systematic inhibitor screening and in-depth kinetic profiling validate these findings and show that second-generation EGFR inhibitors retain kinase affinity and overcome EGFRG724S-mediated resistance. In the case of afatinib this profile translates into a robust reduction of colony formation and tumor growth of EGFRG724S-driven cells. Our data provide a mechanistic basis for the osimertinib-induced selection of EGFRG724S-mutant clones and a rationale to treat these patients with clinically approved second-generation EGFR inhibitors.

Highlights

The emergence of acquired resistance against targeted drugs remains a major clinical challenge in lung adenocarcinoma patients
Osimertinib treatment resulted in a partial response (54% reduction based on RECIST 1.1) (Supplementary Fig. 1B, 1D)
Even though progression occurred after 8.2 months with the growth of target lesions and a new EGFRT790M-negative and EGFRG724S-positive pleural effusion with a molecular fraction (MF, estimate of allelic fraction without calculating the purity and ploidy) of 6.3% (T2) (Supplementary Table 1C)

Summary

Introduction

The emergence of acquired resistance against targeted drugs remains a major clinical challenge in lung adenocarcinoma patients. Our data provide a mechanistic basis for the osimertinib-induced selection of EGFRG724S-mutant clones and a rationale to treat these patients with clinically approved second-generation EGFR inhibitors. Selective inhibition of EGFR with tyrosine kinase inhibitors (TKI), such as erlotinib or gefitinib, significantly prolongs the progression-free survival (PFS) up to 13.6 months in the first-line setting[4,5,6]. Third-generation EGFR inhibitors such as osimertinib have been designed to overcome acquired resistance induced by the EGFRT790M gatekeeper mutation[10]. More recent data indicate that osimertinib treatment is even superior to single agent first-generation inhibitors such as erlotinib or gefitinib in terms of PFS and overall survival (OS) in the first-line setting[13]. We characterized the role of the acquired EGFRG724S mutation that was diagnosed in osimertinib-resistant lesions of four individual EGFR19del-mutant LADC patients. Cellular, and structural analyses to determine the functional relevance of this mutation in the context of targeted EGFR inhibition

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