Identification of a novel nitroflavone-based scaffold for designing mutant-selective EGFR tyrosine kinase inhibitors targeting T790M and C797S resistance in advanced NSCLC

The inhibition of the Epidermal Growth Factor (EGFR) represents one of the most promising strategies in non-small cell lung cancer (NSCLC) therapy. The recently identified C797S mutation causes resistance of EGFRL858R/T790M against osimertinib, the latest approved third generation EGFR inhibitor. The identification of small molecules capable of selectively inhibiting the T790M mutations also in the late-onset C797S mutation is a desirable strategy and novel chemical structures might provide new insight in the overcoming resistance mechanisms. Here we report the identification of a novel mutant-selective privileged molecular core; guided by a structure-based drug design, a flavone skeleton has been rationally modified, and a virtual library generated. Reversible EGFR inhibitors targeting both L858R/T790M and L858R/T790M/C797S mutations with a higher affinity with respect to the wild type one are discovered via a three-track virtual screening. Selected hits were synthesized and tested in an activity-based enzyme assay against wild-type EGFR, L858R/T790M, as well as L858R/T790M/C797S. The results showed that a nitroflavone-based compound inhibits the phosphorylation of EGFR mutants at low-micromolar concentration showing selectivity over the wild type ones. Structurally similar flavone analogues have been synthesized and the following inhibition assays underlied the importance of both the presence and position of the nitrophenoxy moiety.