Inhibitor Evolution: How Drug Design Evolved to Overcome Mutation Mechanisms

Targeting the epidermal growth factor receptor (EGFR) in cells with tyrosine kinase inhibitors (TKIs) is an established strategy to block oncogenic phosphorylation cascades and tumor growth in non-small cell lung cancer (NSCLC). However, tumors frequently develop resistance through the T790M gatekeeper mutation, mitigating the effect of early-generation TKIs. Consequently, later generations of TKIs have been developed to combat these mutations. Our experiment computationally compared five TKIs spanning three drug generations (Erlotinib, Gefitinib, Afatinib, Dacomitinib, and Osimertinib) against wild-type and T790M mutant EGFR to provide an effective evaluation of TKI-generation evolution. Standardized molecular docking via AutoDock Vina was utilized for each TKI-receptor combination, revealing minimal free energy changes across TKI generation and receptor state (ΔΔG = −0.30 to +0.46 kcal/mol), demonstrating that docking scores fail to explain inhibitor generation efficacy differences. Consequently, Python Molecule 3D Rendering (PyMOL) and Protein-Ligand Interaction Profiling (PLIP) analysis determined Third-generation TKIs optimally increased gatekeeper clearance distance when met with the mutated receptor (3.07 Å to 4.31 Å) to remain in an ideal position to block unwanted cell signals while increasing hydrophobic contact (2 to 4 contacts) to block ATP and oncogenic phosphorylation cascades, which the first-generation TKIs failed to achieve. Ultimately, this study demonstrates the specific structural shifts that Third-generation TKIs utilize to remain more effective than first-generation TKIs when faced with mutated receptors.