Abstract 3261: LNG-451, a Potent Inhibitor of EGFR Exon 20 Insertion Mutations with High CNS Exposure

Exon 20 insertion mutations (Ex20ins) are the 3rd most common type of EGFR oncogenic mutation in lung cancer patients and are often associated with brain metastases. While several small molecules have been approved (mobocertinib) or are in clinical development (e.g. CLN-081, BDTX-189) none have demonstrated meaningful CNS activity and they can be associated with treatment-limiting adverse events, including wild-type (WT) EGFR-mediated toxicities. LNG-451 is a potent covalent inhibitor of EGFR Ex20ins (IC50 7 - 78 nM) and other EGFR oncogenic mutations (e.g L858R IC50 = 3 nM, exon 19 deletion IC50 = 24 nM) while being selective against WT EGFR (IC50 = 1630 nM). LNG-451 causes tumor regression in both cell line-derived and patient-derived EGFR Ex20ins-dependent xenograft tumor models. In a rat CNS PK model, a single oral dose of 30 mg/kg LNG-451 achieved high exposures in plasma (AUC0 - 8h = 9771 ng•h/mL) and brain (AUC0 - 8h = 10,041 ng•h/g). In a rat steady-state CNS PK model, unbound partition coefficient for LNG-451 was determined to be Kpu,u = 0.66. To evaluate the potential for LNG-451 to treat metastatic brain disease driven by EGFR mutations, an intracranial PC9-luc xenograft mouse model harboring an EGFR exon 19 deletion mutation was used (LNG-451 cellular EGFR Del19 IC50 = 10.6 nM). LNG-451 had dose-dependent exposures in the plasma and brain with both high mean brain exposure (e.g 1074 ng/g with 25 mg/kg LNG-451) and high mean brain to plasma ratios (e.g. 0.451 for 25 mg/kg LNG-451). LNG-451 treatments were well-tolerated and produced significant anti-tumor activities with 99.5% (2.5 mg/kg LNG-451) and 99.9% (25 mg/kg LNG-451) reductions in total bioluminescence signal (BLI) and regression of tumor BLI (2.5 mg/kg LNG-451 28.8% regression; 25 mg/kg LNG-451, 80.3% regression). An ex vivo imaging analysis of the brain and spinal cords from all animals at the end of the study showed a dose-dependent decrease in the bioluminescent signal in both brain and spinal cords from mice treated with LNG-451 relative to the vehicle control animals. Taken together, LNG-451 is a CNS-penetrant, wild-type EGFR-sparing, EGFR Ex20ins inhibitor that is expected to provide strong anti-tumor efficacy for patients with advanced/metastatic solid cancers harboring oncogenic EGFR exon 20 insertions with reduced WT EGFR driven toxicities. Citation Format: Paul G. Pearson, Anjali Pandey, Bruce Roth, Tracy Saxton, Daniel J. Estes, Ravi Trivedi, Himanshu Agrawal, Gurulingappa Hallur, Ishtiyaque Ahmad, Helen Jenkins, Brion W. Murray. LNG-451, a potent inhibitor of EGFR exon 20 insertion mutations with high CNS exposure [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3261.