Abstract 4029: Combination of KRASG12C(ON) and SHP2 inhibitors overcomes adaptive resistance and enhances anti-tumor immunity

Abstract

Abstract Oncogenic mutations in KRAS are frequent in non-small cell lung cancer and have been associated with poor prognosis. The recent development and approval of KRASG12C mutant-specific inhibitors could change the clinical practice of lung cancer patients harboring KRASG12C mutations. However, early clinical data indicate the development of acquired resistance after initial responses. All of the KRASG12C inhibitors being tested in clinical trials to date target GDP-bound KRAS (OFF state), which makes them vulnerable to upstream pathway reactivation, as this will increase KRAS in a GTP-bound (ON) state and therefore reduce drug efficacy. In this study we use a covalent tri-complex KRASG12C(ON) inhibitor which targets KRASG12C in the active state. In vitro, the KRASG12C(ON) inhibitor RM-029 exhibited higher efficacy than the KRASG12C(OFF) inhibitor MRTX849 (adagrasib). However, treatment with RM-029 also showed adaptive RAS pathway reactivation after 24 hours of treatment, which can be blocked using the SHP2 inhibitor RMC-4550, suggesting that pathway reactivation is mediated by signaling from RTKs to RAS proteins. In vivo, KRASG12C(ON) treatment led to strong regression of KRASG12C tumors and addition of a SHP2 inhibitor significantly increased anti-tumor responses. Single treatments with KRASG12C(ON) or SHP2 inhibitors led to complete responses in some animals and immunological memory in an immune responsive KRASG12C lung tumor model, with all tumors showing complete responses when the inhibitors were combined. Consistent with this finding, both KRASG12C(ON) and SHP2 inhibition resulted in a profound remodeling of the lung tumor microenvironment (TME), with increased infiltration and activation of T cells accompanied by a reduction of tumor-promoting myeloid cells. Interestingly, similar changes were obtained in an immune evasive KRASG12C lung cancer model. Besides acting upstream RAS, SHP2 has also specific roles in immune cells, including regulation of T cell function. As comparison, responses to SOS1 inhibition, which acts only upstream RAS, have also been analyzed. Overall, our preclinical results show that the anti-tumor activity of the combination of KRASG12C(ON) with SHP2 inhibition is the result of different mechanisms. First, a KRASG12C(ON) inhibitor potently inhibits oncogenic RAS and addition of a SHP2 inhibitor blocks RAS pathway reactivation increasing tumor responses. Second, both inhibitors have beneficial effects in the TME which can be potentiated when combined. Finally, addition of a SHP2 inhibitor could potentially overcome intrinsic resistant populations by directly targeting cells resistant to G12C inhibition and/or by increasing anti-tumor immunity. Citation Format: Panayiotis Anastasiou, Edurne Mugarza, Jesse Boumelha, Sareena Rana, Christopher Moore, Miriam Molina-Arcas, Julian Downward. Combination of KRASG12C(ON) and SHP2 inhibitors overcomes adaptive resistance and enhances anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4029.