EMI1 (EGFR MaMTH Inhibitor 1)

EMI1 (EGFR MaMTH Inhibitor 1) is a novel EGFR ex19del/T790M/C797S inhibitor.EMI1, while potently reducing the interaction of EGFR triple mutant with Shc1 in our MaMTH-DS assay, did not behave as a TKI and displayed no inhibition of the kinase activity of EGFR triple-mutant protein invitro.EMI1 did, however, more strongly inhibit the viability and increase the caspase 3/7 activ-ity of PC9 EGFR ex19del/T790M/C797S triple-mutant cells than noncancerous human bronchial epithelial (HBE) cells, as well as potently reduce PC9 EGFR ex19del/T790M/C797S organ-oid viability.EMI1 had a similar inhibi-tory effect on microtubule plus-end growth in both EGFR-WT and EGFR-C797S triple-mutant cells at 50–100 nM concentration. At 1 µM concentration, EMI1 strongly depolymerized inter-phase microtubules, perturbed spindle formation and induced strong mitotic block in PC9 EGFR ex19del/T790M/C797S cells after 20 h of treatment. EMI1 inhibited interaction of both proteins with EGFR at a level similar to that observed with Shc1, indicating it is not a specific inhibitor of the EGFR-Shc1 PPI interface. Rather, the loss of interaction mediated by EMI1 appears to be due to a more general alteration in EGFR activity.EMI1 induced EGFR degradation, and inhibited the activation of EGFR, ERK, AKT and S6 in PC9-ex19del and PC9-ex19del/T790M cells.