Directly targeting RAS is a desirable approach for treating RAS-mutated tumors because direct RAS inhibitors block all RAS effector pathways simultaneously. Recently, several groups have developed agents that directly target KRAS by covalently modifying KRASG12C. KRAS is commonly altered in adult malignancies such as lung, pancreatic, and colorectal adenocarcinoma, but is less commonly altered in pediatric cancer. However, rare pediatric tumors harboring K-, H-, or NRASG12C are observed. The efficacy of KRASG12C inhibitors in pediatric malignancies is currently unknown, and the ability of these drugs to modify H- and NRASG12C has been incompletely characterized. Here we show that the KRASG12C inhibitors AMG 510, MRTX849, and ARS-1620 slow the release of GDP from H-, N-, and KRASG12C in vitro. Using RASless MEFs, we show that the activity of AMG 510 is specific for H-, N- or KRASG12C, while MRTX849 has both G12C and RAS-independent effects on cell viability. The KRASG12C inhibitors decreased cell viability in KRAS-mutant cell lines derived from patients with the pediatric solid tumor neuroblastoma. MRTX849 was more potent than AMG 510 in neuroblastoma cell lines but was less efficacious and less G12C-specific. The KRASG12C inhibitors also decreased cell viability in an NRASG12C-mutant T-cell ALL cell line derived from an adolescent patient but only MTRX849 decreased cell viability in an HRASG12C-mutant rhabdomyosarcoma cell line. These results suggest that KRASG12C inhibitors may be a treatment option for pediatric patients with H-, N- or KRASG12C mutant solid tumors or leukemia. Future studies will be aimed at testing the efficacy of these inhibitors in xenograft models of pediatric cancer and identifying non-RAS targets of MRTX849.

Citation Format: Hannah Price, Stacey Stauffer, Katie Powell, Andrew Baker, Andrew Perciaccante, Edjay Ralph Hernandez, Patience Odeniyide, Christine Pratilas, William Burgan, Lisa Jenkins, Kent L. Rossman, Marielle Yohe. Preclinical efficacy of KRASG12C inhibitors in models of pediatric cancer [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 B038.