Abstract B080: Mutant-selective KRASG12D(ON) inhibitor suppresses proliferation in vitro and tumor growth in vivo of KrasG12D GEMM-derived PDAC organoids

Abstract

Abstract KRAS is the most frequently mutated oncogene in pancreatic ductal adenocarcinoma (PDAC), with KRASG12D driving initiation and progression of ~40% of tumors. Mutant KRAS proteins exist predominantly in the GTP-bound (RAS(ON)) state, leading to excessive downstream signaling via interaction with effectors such as RAF kinases. RMC-9805 is an orally bioavailable, mutant-selective covalent inhibitor of the active state of KRASG12D. RM-044, used here, is the corresponding representative preclinical tool compound. RM-044, KRASG12D and cyclophilin A form a stable, high affinity tri-complex resulting in the disruption of interactions with downstream KRAS effectors and suppression of KRASG12D(ON) signaling. RM-044 decreased RAS pathway activity and inhibited proliferation in multiple human KRASG12D PDAC cell lines in vitro. While these data are encouraging, we sought to study models that more faithfully represent the heterogeneity and complex tumor microenvironment found in the tumors of patients with KRASG12D PDAC. To address this, we generated and characterized pancreatic organoids from the lox-STOP-lox-KrasG12D genetically engineered mouse model (GEMM) and introduced expression of the KrasG12D mutation and p53 loss (KP) through a vector containing a p53 sgRNA and Cre recombinase. GEMM-derived KP pancreatic organoid lines treated with RM-044 showed concentration-dependent proliferation inhibition in vitro. KP organoids were implanted orthotopically into mouse pancreas leading to the development of PDAC tumors in immunocompetent mice. Histopathological examination of KP organoid derived tumors revealed molecular and phenotypic features translatable to the tumors of patients with PDAC. In this orthotopic model, oral administration of RM-044 inhibited MAPK pathway activation and led to deep and durable tumor growth suppression at a well-tolerated dose. In summary, mutant-selective, covalent inhibition of KRASG12D(ON) inhibits cell proliferation and drives tumor growth suppression in both human and murine preclinical models of KRASG12D PDAC. The generation of preclinical models that allow for in-depth translational analyses of KRASG12D(ON) inhibition in vitro and in vivo can support identification of optimal therapeutic regimens. Collectively, these preclinical results indicate that direct targeting of KRASG12D(ON) in PDAC has the potential to translate into clinical benefit for patients with pancreatic cancer. Citation Format: Mark P. Labrecque, Lingyan Jiang, Nicole Nasholm, Biswadeep Nayak, Xinxing Yu, Avian Song, Caroline Weller, James W. Evans, Maria Paz Zafra, Marie Parsons, Marie Menard, Lukas E. Dow, Jingjing Jiang, Ida Aronchik, Mallika Singh. Mutant-selective KRASG12D(ON) inhibitor suppresses proliferation in vitro and tumor growth in vivo of KrasG12D GEMM-derived PDAC organoids [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B080.