LAUSR

Background: Epidermal growth factor receptor (EGFR) activating mutations have been reported in 10-50% of patients with non-small cell lung cancer (NSCLC). The common mutations, ex19del (D) and L858R (L) substitution, are sensitive to first- and second-generation EGFR-TKIs. However, acquired on-target resistance, especially T790M (T) mutation, comprises the anti-tumor effects of these inhibitors. Though the third-generation EGFR-TKI Osimertinib potently inhibits both EGFR common mutations and T790M mutation, 10-24% of patients acquire C797S (C) resistant mutation. Here, we report a highly potent and selective fourth-generation EGFR-TKI, PH009-1, designed to overcome both EGFR common mutations and T790M/C797S-mediated resistance in NSCLC. Methods: Kinase selectivity of Ph009-1 was assessed by KINOMEscan against 468 human kinases. A functional safety panel including 47 targets contributing to clinical adverse drug reactions was used to evaluate pharmacological profiling of PH009-1. Biochemical enzyme activities were detected with kinase assays and anti-proliferative activities were measured in various tumor and engineered Ba/F3 cell lines. The in vivo anti-tumor efficacy was tested in four cell derived xenograft (CDX) mouse cancer models with tumor harboring single, double or triple mutant EGFR. The in vitro and in vivo pharmacokinetic (microsome metabolic stability, hepatocyte metabolic stability, plasma protein binding, drug-drug interaction, oral absorption, et al) and safety properties (hERG potassium channel assay, Ames assay, repeated dosing study, et al) of PH009-1 were assessed in various species with corresponding assay methods. Results: High kinase selectivity and very low off-target effects were observed in KINOMEscan and safety panel assays, respectively. PH009-1 inhibited kinase activity of all tested EGFR mutants with IC50<4 nM. Furthermore, PH009-1 displayed potent anti-proliferation activity against Ba/F3 (EGFR L, D, LC, DC, DT, LTC, DTC) with IC50 of 3.6, 3.1, 1.6, 1.7, 0.3, 3.9, 3.1 nM, respectively. Excellent selectivity of PH009-1 was observed when compared the above values to IC50 against Ba/F3 (WT, 93.3 nM), A431 (WT, 2415 nM), LoVo (WT, 3700 nM) and NCI-H23 (WT, 2359 nM). In all four CDX cancer models including HCC827 (D), Ba/F3 (DC), Ba/F3 (LC) and Ba/F3 (DTC), PH009-1 at a dose of 40 mg/kg BID induced tumor regression or eradication without significant effect on mouse body weight. Favorable pharmacokinetic and safety profiles were suggested in in vitro and in vivo pharmacokinetic and safety evaluations. Conclusion: The present data suggest that PH009-1 is a promising and highly selective fourth-generation EGFR TKI with potent in vitro and in vivo activity against single, double and triple EGFR mutations including T790M and C797S. Citation Format: Feng Gao, Bin Liu, YongYong Wu, Liandong Jing, Pengzhi Zhang, Jing Wang, Shuai Yuan, Hui Zhao, Yu Gao, Zhizhong Li, Xiaofan Wang, Yongqi Guo. PH009-1, a highly potent and selective fourth-generation EGFR-TKI overcoming EGFR common mutations and T790M/C797S-mediated resistance in NSCLC. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4005.