Abstract IA20: The impact of RAS inhibition on tumor immune evasion

Abstract

Abstract The approval of two KRAS G12C mutant-specific inhibitory drugs, sotorasib and adagrasib, has markedly improved the treatment of lung cancer patients harbouring KRAS G12C oncogenic mutations. However, development of acquired drug resistance is very common after initial responses, and impact on overall survival is small. Additional therapies will therefore need to be combined with KRASG12C inhibitors if long-term cures are to be achieved. Due to the immunosuppressive nature of the signaling network controlled by oncogenic KRAS, targeted KRAS G12C inhibition can indirectly affect anti-tumour immunity. This has served as a rationale for combination with immune checkpoint blockade (ICB), which we have shown leads to additional therapeutic benefit in immunogenic/hot, but not immune evasive/cold, pre-clinical lung tumour models. However, in clinical trials in KRAS G12C mutant lung cancer, combination of KRAS G12C inhibitors with PD-(L)1 blockade has yet to show improved outcome, either due to toxicities or lack of efficacy, possibly linked to prior progression on immunotherapy. Study of the response of KRAS G12C mutant lung tumours to KRAS G12C inhibitory drugs using spatial and multi-omic technologies has highlighted the role of particular populations of immune cells in the tumor microenvironment in impeding immune attack on the tumor. In immune evasive lung cancer, following KRAS G12C inhibitor treatment a community of cells is identified within the tumor containing dendritic cells, CD8+ T cells and dying tumor cells, which appears to function as an antigen presentation hub. This community is restrained by T reg cells, whose coordinate targeting markedly improves the impact of KRAS G12C inhibitors. In an immunogenic/hot mouse model of KRAS G12C mutant lung cancer, tertiary lymphoid structures are seen along with tumor-binding antibodies, which target endogenous retrovirus (ERV) envelope glycoproteins on the tumor cells. ERV-targeting B cell responses are amplified by ICB in both humans and mice, and by targeted KRAS G12C inhibition in the murine model. ERV-reactive antibodies exert anti-tumour activity that extend survival in the murine model and ERV expression predicts the outcome of ICB in human lung adenocarcinoma. Rational, mechanism-based exploitation of the impact of KRAS inhibition on tumor immune evasion provides opportunities for successful combination therapy of RAS mutant cancers. Citation Format: Julian Downward. The impact of RAS inhibition on tumor immune evasion [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 IA20.