Discovery of HCD3514 as a potent EGFR inhibitor against C797S mutation in vitro and in vivo

Osimertinib (AZD9291), a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI), has significantly improved the survival of non-small cell lung cancer (NSCLC) patients with EGFR(T790M) mutation, the major mechanism of acquired resistance to first-generation EGFR TKI. However, resistance to AZD9291 arises eventually and EGFR(C797S) mutation was reported to be a major resistance mechanism. Thus, it is highly valuable to develop novel EGFR fourth-generation inhibitors targeting C797S mutation to override the acquired resistance. In this study, we identified HCD3514 as a novel EGFR fourth-generation inhibitors targeting C797S triple mutation. It strongly inhibited EGFR(L858R/T790M/C797S) and EGFR(19del/T790M/C797S) mutations with IC(50) values of 1.0 and 2.0 nM, respectively. HCD3514 dose-dependently inhibited the activation of EGFR in both engineered BaF3 cells and tumor cells harboring EGFR(C797S) triple mutant and thus effectively suppressed the proliferation of the cells. Moreover, HCD3514 caused a dose-dependent increase of apoptosis in C797S triple mutant cells accompanied by increased levels of cleaved caspase-3 and cleaved PARP. Furthermore, HCD3514 induced tumor growth inhibition in EGFR(19del/T790M/C797S) xenograft model as a single oral agent by decreasing the activation of EGFR. In addition to EGFR(C797S) triple mutations, HCD3514 also potently and selectively inhibited EGFR(T790M) double mutations (L858R/T790M and 19del/T790M). Collectively, HCD3514 is a highly selective and potent EGFR inhibitor against EGFR(C797S) triple mutations as well as EGFR(T790M) double mutations and is confirmed potently anti-tumor activity in preclinical models.