Discovery of novel 9-heterocyclyl substituted 9H-purines as L858R/T790M/C797S mutant EGFR tyrosine kinase inhibitors

Targeting L858R/T790M/C797S mutant EGFR is a major challenge in the new-generation EGFR tyrosine kinase inhibitors development for conquering drug resistant NSCLC. In this study, a series of novel 9-heterocyclyl substituted 9H-purine derivatives were designed as EGFR^{L858 R/T790 M/C797S} tyrosine kinase inhibitors. Among these compounds, D4, D9, D11 and D12 showed significantly potent anti-proliferation and EGFR^{L858 R/T790 M/C797S} inhibition activity. In particular, the most potent compound D9 showed anti-proliferation against HCC827 and H1975 cell lines with the IC₅₀ values of 0.00088 and 0.20 μM, respectively. And D9 inhibited the EGFR^{L858 R/T790 M/C797S} with an IC₅₀ value of 18 nM. Furtherly, D9 could significantly suppress the EGFR phosphorylation, induce the apoptosis, arrest cell cycle at G0/G1, and inhibit colony formation in HCC827 cell line by a concentration-dependent manner. Molecular docking indicated that the introduction of a cyclopropylsulfonamide group in D9 led to the formation of additional two hydrogen bonds with mutant Ser797 which played key roles in generating efficient EGFR^{L858 R/T790 M/C797S} inhibitory activity. These findings strongly indicated that 9-heterocyclyl substituted 9H-purine derivatives were promising L858R/T790M/C797S mutant EGFR-TKIs. The introduction of extra hydrogen bond interaction with mutant Ser797 is efficient method for the design of the fourth-generation EGFR-TKIs.