Abstract B026: Overcoming KRAS G12C inhibitor resistance with chaperone-mediated protein degrader in NSCLC

Abstract KRAS-G12C targeting inhibitors (G12Cis), such adagrasib and sotorasib, have shown specificity and promising anti-tumor potential in non-small cell lung carcinoma (NSCLC). However, acquired resistance to these inhibitors has recently been observed in the clinic. Mechanisms of resistance to G12Cis are associated with genetic alterations of several pro-growth signaling pathways. A strategy to overcome the multifarious resistance mechanisms to G12Cis that does not require further molecular characterization is needed. To develop an all-round strategy to overcome G12Ci resistance mechanisms, we exposed NCI-H358, NCI-H1373, and MIAPaCa2 cell lines harboring KRAS-G12C mutations to increasing concentrations of sotorasib or adagrasib over 6 months. The resulting resistant cells proliferate normally in the presence of 10 μM sotorasib or adagrasib. Sotorasib-resistant cells designated as NCI-H358S-R, NCI-H1373S-R, and MIAPaCa2S-R remarkably remain sensitive to adagrasib, suggesting but not proving that the resistant cells remain dependent on mutant KRAS for survival. Adagrasib-resistant cells designated as NCI-H358A-R, NCI-H1373A-R, and MIAPaCa2A-R in contrast remain resistant to both sotorasib and adagrasib. Treatment of adagrasib-resistant cells with 500 nM adagrasib attenuated KRAS activity, however, this was compensated by activation of varied receptor tyrosine kinases (RTKs) to restore phospho-ERK levels, a surrogate marker of RAS activity. Moreover, treatment of de novo resistant NSCLC cells lines NCI-H2030, NCI-H1792, and NCI-H23 or NSCLC patient derived organoids (PDOs) with 500 nM adagrasib resulted in sustained phospho-ERK levels through activation of RTKs. These results indicate the need to simultaneously reduce both KRAS G12C and compensating RTK activity to effectively treat NSCLC. The majority of oncogenic RTKs are dependent on the molecular chaperone HSP90 to maintain stability. Therefore, a heterobifunctional chaperone mediated protein (CHAMP) degrader, RNK07421, was designed to specifically target both KRAS G12C and HSP90. RNK07421 induces an artificial ternary complex between KRAS G12C and HSP90, while also inhibiting the activity of both proteins. The RNK07421 coordinated KRAS G12C-HSP90 interaction promotes the proteasome degradation of KRAS G12C likely via HSP90 associated E3-ligases. Treatment of adagrasib resistant NSCLC cells and PDOs with RNK07421 resulted in reduced levels of KRAS G12C and phospho-ERK along with resistance enabling RTKs: EGFR, BRAF and FGFR2. Furthermore, in vivo treatment of resistant NSCLC cells with RNK07421 demonstrated dramatic tumor reduction as compared to G12Ci. Together these observations indicate that the novel mechanisms of action of RNK07421 may provide several advantages to G12Cis and possibly other targeted protein degradation agents to effectively treat KRAS G12C dependent NSCLC. Citation Format: Ines Pulido, Jennifer M. Graeber, Brianna C. Borger, Kevin P. Foley, Weiwen Ying, Chenghao Ying, Jinhua Li, Yaya Wang, Yuetong Sun, Yan Dai, Guoqiang Wang, Thomas L. Prince, Takeshi Shimamura. Overcoming KRAS G12C inhibitor resistance with chaperone-mediated protein degrader in NSCLC [abstract]. In: Proceedings of the AACR Special Conference: Targeting RAS; 2023 Mar 5-8; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Res 2023;21(5_Suppl):Abstract nr B026.