Discovery of Potent PROTACs Targeting EGFR Mutants through the Optimization of Covalent EGFR Ligands

Drug resistance caused by epidermal growth factor receptor (EGFR) mutation has largely limited the clinical use of EGFR tyrosine kinase inhibitors (EGFR-TKIs) for the treatment of non-small-cell lung cancer (NSCLC). Herein, to overcome the intractable problem of drug resistance, proteolysis targeting chimeras (PROTACs) targeting EGFR mutants were developed by optimizing covalent EGFR ligands. Covalent or reversible covalent pyrimidine- or purine-containing PROTACs were designed, synthesized, and evaluated. As a consequence, covalent PROTAC CP17, with a novel purine-containing EGFR ligand, was discovered as a highly potent degrader against EGFR^L858R/T790M and EGFR^del19, reaching the lowest DC₅₀ values among all reported EGFR-targeting PROTACs. Furthermore, CP17 exhibited excellent cellular activity against the H1975 and HCC827 cell lines with high selectivity. Mechanism investigation indicated that the lysosome was involved in the degradation process. Importantly, the covalent binding strategy was proven to be an effective approach for the design of PROTACs targeting EGFR^L858R/T790M, which laid the practical foundation for further development of potent EGFR-targeting PROTACs.