Abstract B093: Treating KRAS(G12D) inhibitor resistance using a KRAS- and HSP90 chaperone-targeted hetero-bispecific small molecule agent

Abstract

Abstract KRAS is the most frequently mutated oncoprotein in human cancers. Although long considered “undruggable”, recent breakthroughs in medicinal chemistry have led to FDA-approval of the KRAS(G12C) mutation-specific inhibitors sotorasib and adagrasib for the treatment of KRAS(G12C)-positive non-small cell lung cancer. However, illustrating the need to develop additional novel agents targeting mutated KRAS, the 5-year relative survival rate for pancreatic cancer, which is commonly associated with a variety of different KRAS mutations, is only 12% (all SEER stages) due to poor early detection and a lack of effective treatments. In particular, KRAS(G12D) is the most common KRAS mutation, being found in 37% of pancreatic ductal adenocarcinomas (PDACs), as well as in 12.5% of colorectal cancer and 4.9% of lung adenocarcinoma (LUAD) patients. MRTX1133 is a highly-selective, non-covalent KRAS(G12D) inhibitor that has recently entered a phase 1 clinical trial. However, here we show that exposure of KRAS(G12D)-mutated PDAC (PANC-1 and AsPC-1) and LUAD (SK-LU-1) cell lines and a patient-derived organoid (PDO) PDAC model (RPAN001) to MRTX1133 resulted in varying degrees of in vitro efficacy. Decreased downstream KRAS signaling in the form of reduced phospho-ERK1/2 levels was observed to rapidly recover within 24 hours of treatment with 500 nM MRTX1133. Moreover, this rebound coincided with increased expression of KRAS, NRAS andHRAS mRNAs. Concurrently, activation of the receptor tyrosine kinases (RTKs) EGFR and MET was observed in PANC-1 and SK-LU-1 cells that displayed innate resistance to MRTX1133, while the sensitive AsPC-1 cells showed no such RTK activation. These results suggest that targeting of both KRAS(G12D) and RTKs may be needed to treat KRAS(G12D) inhibitor-resistant cancers. To address this, we employed a novel hetero-bispecific CHAMP molecule, RNK08179, that simultaneously targets both KRAS(G12D) and HSP90, an RTK-regulating chaperone protein. RNK08179 treatment demonstrated a striking reduction in phospho-ERK1/2 levels, RTK activation and cell viability in MRTX1133-resistant PANC-1 and SK-LU-1 cells. Furthermore, similar efficacy was observed in the MRTX1133-resistant RPAN001 PDO model. In summary, RNK08179 displayed promising efficacy in cancer models harboring KRAS(G12D) by suppressing both mutated KRAS and HSP90-supported RTK signaling. Citation Format: Ines Pulido, Qiyue Luan, Chenghao Yin, Zimo Yang, Jinhua Lin, Yaya Wang, Yuetong Sun, Chuche Liu, Haoxin Zhou, Marek Massad, Ian Papautsky, Thomas L. Prince, Guoqiang Wang, Kevin P. Foley, Weiwen Ying, Takeshi Shimamura. Treating KRAS(G12D) inhibitor resistance using a KRAS- and HSP90 chaperone-targeted hetero-bispecific small molecule agent [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B093.