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

Abstract

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 DC 50 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 EGFRtargeting PROTACs.

Discovery of small molecule ligands for the von Hippel-Lindau (VHL) E3 ligase and their use as inhibitors and PROTAC degraders

“…Further EGFR targeting VHL-recruiting PROTACs have been developed since, [161][162][163][164][165] including the recently disclosed covalent EGFR degrader CP17, with single-digit nanomolar DC 50 values the most potent EGFR degrader reported to date. 165 4.2.8. Serum/glucocorticoid-inducible protein kinase (SGK) targeting PROTACs.…”

“…27) induced almost complete, selective degradation of the Exon19 del and L858R mutations of EGFR, while sparing wild-type EGFR, showcasing that choice of the right ligand can allow differentiation between different mutational states of the target POI. Further EGFR targeting VHL-recruiting PROTACs have been developed since, [161][162][163][164][165] including the recently disclosed covalent EGFR degrader CP17, with single-digit nanomolar DC 50 values the most potent EGFR degrader reported to date. 165 4.2.8.…”

Homobivalent, Trivalent, and Covalent PROTACs: Emerging Strategies for Protein Degradation

“…The Zhang group designed a novel EGFR covalent PROTAC CP17 ( 70 ) based on a purine-containing EGFR inhibitor and a VHL ligand . This compound could effectively degrade EGFR L858R/T790M (H1975 cells, DC 50 = 1.56 nM) and EGFR del19 (HCC827 cells, DC 50 = 0.49 nM), representing the lowest DC 50 values among all of the reported EGFR PROTACs.…”

Proteolysis Targeting Chimeras (PROTACs): A Perspective on Integral Membrane Protein Degradation

“…However, this usually reverses in cellular assays, where the PROTACs exhibit a much stronger effect, thereby demonstrating that degradation of the target has a stronger and wider impact on the cell than its inhibition. Clearly, PROTACs not only inhibit the enzymatic activity due to decreased abundance of the integral membrane protein but also attenuate any scaffolding role the POI may have had and prevent development of compensatory feedback pathways. ,,,, …”