Abstract 1649: Chemically induced chaperone-mediated protein degradation (CHAMP) of KRAS(G12C)

Abstract Covalent KRAS(G12C) inhibitors have recently shown promising efficacy in the clinic. However, the rapid development of drug resistance compromises their long-term benefits, indicating the need for additional approaches to treat KRAS-mutated cancers. Targeted protein degradation represents one such potential approach. We have therefore explored applying Chaperone-mediated Protein Degradation (CHAMP) technology to degrade KRAS(G12C) protein. CHAMPs are heterobifunctional small molecules that mediate protein degradation by inducing proximity between a target protein and the HSP90 chaperone complex, resulting in target ubiquitination and degradation by the proteasome. Due HSP90 being highly activated in cancer cells, CHAMPs also preferentially accumulate in tumors relative to normal tissues, resulting in an improved therapeutic index relative to typical inhibitors. In order to chemically induce KRAS(G12C) degradation, CHAMP compounds were synthesized by covalently coupling KRAS(G12C)- and HSP90-binding moieties through a short linker. CHAMP treatment of KRAS(G12C)-mutated cell lines resulted in formation of a KRAS(G12C)-CHAMP-HSP90 ternary complex and subsequent proteasome-dependent KRAS(G12C) degradation and inhibition of cell proliferation. In contrast, combination treatment with KRAS(G12C) and HSP90 inhibitors did not result in substantial KRAS(G12C) degradation. Importantly, CHAMPs retained potency in cell line models of resistance to covalent KRAS(G12C) inhibitors. Further, in mouse xenograft models, CHAMPs displayed prolonged pharmacokinetics in tumors relative to plasma and normal tissues and strongly inhibited tumor growth at tolerated doses. Based on these findings, KRAS(G12C)-degrading CHAMPs represents a promising approach to the treatment of KRAS(G12C)-mutated cancers. Citation Format: Kevin P. Foley, Chenghao Ying, Yaya Wang, Yan Dai, Zhiyong Wang, Jinhua Li, Zimo Yang, Yuetong Sun, Hao Xin Zhou, Thomas L. Prince, Guoqiang Wang, Weiwen Ying. Chemically induced chaperone-mediated protein degradation (CHAMP) of KRAS(G12C) [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 1649.