A research team led by Professor Zhang Sanqi of the School of Pharmacy at Xi'an Jiaotong University (XJTU) has made important progress in epidermal growth factor receptor (EGFR) mutant proteolytic targeting chimeras (PROTACs).

The team has been working on tyrosine kinase inhibitors (EGFR-TKIs), hoping to overcome or circumvent the resistance caused by EGFR mutations through PROTACs technology.

Based on previous work, the team obtained a series of covalent EGFR mutants and discovered new highly active covalent EGFR-TKIs containing purine backbones as EGFR ligands PROTACs, and finally found PROTACCP17, which has high anti-proliferative activity, good degradation activity, and high selectivity. It can simultaneously induce single mutation EGFR (EGFRdel19) and double mutation EGFR (EGFRL858R/T790M).

(A) The structure of the reversible PROTAC previously reported by the team

(B) Docking model of compound 9 (green) and EGFRT790M (yellow, PDB:3ika)

(C) Design of purine backbone-containing EGFR-TKIs and purine fragment-containing covalent EGFR mutant PROTACs

(A, C) CP17 assay results for EGFRL858R/T790M and EGFRdel19 DC50 values

(B, D) Statistical graphs of (A, C) respectively

In a western blot test, the DC50 value of CP17 to the drug-resistant mutant EGFRL858R/T790M reached 1.56 nM, and the DC50 value of EGFRdel19 reached 0.49 nmol/L.

CP17 showed strong anti-proliferative activity against HCC827 (EGFRdel19) and H1975 (EGFRL858R/T790M) cells simultaneously, with IC50 values of 1.60 and 32 nmol/L, respectively.

A series of degradation mechanism studies have shown that CP17 binds to both EGFR and VHL to form a ternary complex, and promotes the ubiquitination of EGFR, which in turn degrades EGFR.

Moreover, the degradation of EGFR is associated with lysosomes. This research demonstrates that covalent binding is an effective strategy to discover highly active EGFRL858R/T790M PROTACs.

(A) Structures of reversible PROTACR1 and covalent PROTACCP17

(B,C) Results of assay of R1 and CP17 anti-proliferative activities of H1975 and HCC827 cells

(D,E) Degradation activity of R1 and CP17 on EGFRL858R/T790M and EGFRdel19

(F) The statistical result of (D,E)

The research results were published in the Journal of Medicinal Chemistry with the title Discovery of Potent PROTACs Targeting EGFR Mutantsthrough Optimization of Covalent EGFR Ligand. (Link to the paper: https://doi.org/10.1021/acs.jmedchem.1c01827)

The first author of the paper is doctoral student Zhao Hongyi, the corresponding author is Professor Zhang, and XJTU is the only communication unit. The research was funded by the National Natural Science Foundation of China.