Covalent vs. Non-Covalent Inhibition: Tackling Drug Resistance in EGFR - A Thorough Dynamic Perspective.

A persistent challenge in the treatment of non-small cell lung cancer (NSCLC) with EGFR is the emergence of drug-resistant caused by somatic mutations. The EGFR L858R/T790 M double mutant (EGFRDM ) was found to be the most alarming variant. Despite the development of a wide range of inhibitors, none of them could inhibit EGFRDM effectively. Recently, 11h and 45a, have been found to be potent inhibitors against EGFRDM through two distinctive mechanisms, non-covalent and covalent binding, respectively. However, the structural and dynamic implications of the two modes of inhibitions remain unexplored. Herein, two molecular dynamics simulation protocols, coupled with free-energy calculations, were applied to gain insight into the atomistic nature of each binding mode. The comparative analysis confirmed that there is a significant difference in the binding free energy between 11h and 45a (ΔΔGbind =-21.17 kcal/mol). The main binding force that governs the binding of both inhibitors is vdW, with a higher contribution for 45a. Two residues ARG841 and THR854 were found to have curtailed role in the binding of 45a to EGFRDM by stabilizing its flexible alcohol chain. The 45a binding to EGFRDM induces structural rearrangement in the active site to allow easier accessibility of 45a to target residue CYS797. The findings of this work can substantially shed light on new strategies for developing novel classes of covalent and non-covalent inhibitors with increased specificity and potency.