Figure 3. IACS-13909 suppresses the proliferation and MAPK pathway signaling of EGFR TKI-resistant EGFR^mut NSCLC models harboring an EGFR-dependent resistance mutation.

Anti-proliferative activity of osimertinib (A) and IACS-13909 (B) in NCI-H1975 parental and NCI-H1975 CS cells, determined by a 14-day clonogenic assay. The NCI-H1975 parental cells harbor EGFR^L858R/T790M, and the NCI-H1975 CS cells harbor EGFR^{L858R/T790M/C797S}, where the C797S mutation on EGFR was introduced through CRISPR. N=3. Confirmation of the C797S mutation was provided in Figure S2. (C) The impact of osimertinib or IACS-13909 on pERK1/2 ^T202/Y204 and pEGFR^Y1068 levels in NCI-H1975 CS cells in vitro. Cells were treated with IACS-13909 or osimertinib for two hours and processed for Western blotting. (D-E) Anti-proliferative activity of osimertinib (D) and IACS-13909 (E) on primary cells isolated from NSCLC PDX LD1-0025-200717 harboring EGFR^{ex19del/T790M/C797S}, determined by a 6-day ex vivo spheroid assay. The dotted horizontal line indicates the relative viable cell number when compound was added. N=4. (F) Tumor growth curve of the NCI-H1975 parental subcutaneous xenograft model in mice, when treated with either vehicle, erlotinib 10 mg/kg QD, osimertinib 5 mg/kg QD or IACS-13909 at 70 mg/kg QD orally, for 21 days. N=10 mice per group. 2-way ANOVA was used to compare the growth curve of IACS-13909-treated tumors vs vehicle treated tumors. **, p<0.01. (G) Tumor growth curve of the NCI-H1975 CS subcutaneous xenograft model in mice, when treated with either vehicle, osimertinib 5 mg/kg QD or IACS-13909 at 70 mg/kg QD orally, for 12 days. The dotted vertical line denotes the final dose. N=10 mice per group. 2-way ANOVA was used to compare the growth curve of IACS-13909-treated tumors vs osimertinib-treated tumors and vehicle-treated tumors. **, p<0.01.