Abstract 417: Identification of next-generation EGFR degraders to treat non-small cell lung cancer (NSCLC) patients

Abstract Although EGFR-targeted tyrosine kinase inhibitors (TKIs) developed over a couple of decades have made great progress in the treatment of EGFR-mutant driven NSCLC, patients are at great risk to their lives due to drug resistance caused by constantly emerging EGFR mutations. Targeted protein degraders (TPDs), also known as heterobifunctional protein degraders or PROteolysis TArgeting Chimeras (PROTACs), have drawn great attention as a new modality to overcome drug resistance by achieving selective degradation of disease-causing proteins, like an EGFR mutant protein, which are required for the survival and proliferation of various malignant tumor cells. Therefore, we have developed a series of EGFR mutant degraders using BBT-176, a 4th generation EGFR TKI developed by Bridge BioTherapeutics, and novel EGFR inhibitors as warheads which are expected not only to treat various EGFR mutated NSCLC including C797S but also to delay drug resistant-mechanisms by further mutations in the EGFR TKI target site. We synthesized a set of heterobifunctional degraders applying Cyrus BiFx Degrader (CBD) library platform containing different types of linkers and E3 ligase binders. DC50 (half-maximal degradation concentrations) values of the EGFR degraders were obtained in multiple human EGFR mutant NSCLC cell lines, where C-2051, C-2482, and C-4383 showed excellent EGFR degradation potency (DC50 = 7-25 nM, Dmax at 100 nM = 80-97%) with high selectivity against WT EGFR. Among those compounds, C-4383 was potent in cell viability assays with EGFR mutant HCC827 (Del19) and NCI-H1975 (L858R, T790M) cell lines showing a range of GI50 values from 77 to 81 nM at 72 h of compound exposure. By contrast, the compound was much less potent in A549 cells harboring wild-type EGFR (GI50 value at 72 h of treatment, 4.2 μM). We also performed proteomic analysis of C-4383 in H1975 cells resulting that EGFR was the most degraded protein with no off-target events at 100 nM (Dmax dose). A PK study of C-4383 in rats showed good exposure with moderate CL when administered intravenously (CL = 8.51 mL/min/kg, AUC = 5911 ng•h/mL). In summary, we identified heterobifunctional degraders using a 4th generation EGFR inhibitor, BBT-176, that are active in EGFR mutant NSCLC cells harboring single or C797S-containing multiple mutations. We are currently making our efforts on the improvement of physicochemical properties of EGFR mutant targeted heterobifunctional compounds. Citation Format: Dong Hyuk Ki, Joonwoo Nam, Eunjung Kim, Hunmi Choi, Chulwon Kim, Jiyeon Kim, Jimmy Jin, Sang-Uk Kang, Wooseok Han. Identification of next-generation EGFR degraders to treat non-small cell lung cancer (NSCLC) patients [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 417.