The Influences Of Drug-Resistant Mutations Of Egfr To The Inhibitor Binding Affinity And The Drug Target Selectivity Profiles

Small molecular inhibitors of receptor kinases suppress cellular signaling pathways mediated by the proteins that lead to malignant cell growth and division. We have studied molecular interactions between epidermal grow factor receptor (EGFR) and the small molecular inhibitors targeting the protein, using free energy molecular dynamics (MD) simulations. First we quantified the influence of a mutation (T790M) known to cause drug-resistance. After prolonged application of an inhibitor, cancer cells begin to express the drug-resistant somatic mutation that reduces the efficacy of the EGFR selective inhibitors. Using thermodynamic integration MD simulations, we show that the mutation (T790M) reduces the binding affinity of several reversible inhibitors of EGFR to the enzymatically active conformation of the protein. Metadynamics MD simulations of WT and mutant EGFRs in apo show that the mutation causes a conformational equilibrium shift toward the active conformation. The binding energy penalty to the active conformation and the equilibrium shift toward the active state explain the observed dissociation constant profile of gefitinib. Second, we quantified the target selectivity of the EGFR inhibitors. Based on a series of metadynamics MD simulations of EGFRs bound to gefitinib, we demonstrate that the inhibitor recognizes both the active and the Src/Cdk-like inactive conformations. The results agree well with a recent crystallographic study that showed gefitinib interacts with the inactive conformation of the T790M/L858R dual mutant EGFR. These computational results provide fine details of the inhibitor-protein interactions, which will guide further development of the receptor kinase inhibitors.