Abstract 1924: RTK signaling and WT RAS activity as vulnerabilities in tumors with acquired resistance to GDP-state selective KRASG12C inhibitors in preclinical models

Abstract Background: KRASG12C-GDP Inhibitors such as sotorasib and adagrasib have demonstrated clinical benefit in lung cancer patients harboring an oncogenic KRASG12C mutation. However, the durability of monotherapy benefit is limited by the development of resistance. Hence, identification of novel treatment approaches to overcome resistance and extend duration of benefit becomes necessary to address this unmet clinical need. Experimental Design: We generated two NSCLC models of KRASG12C−GDP inhibitor acquired resistance, named sotorasib-R LU65 (cell-line derived, in vitro) and adagrasib-R LUN156 (PDX-derived, in vivo) following extended treatment with sotorasib and adagrasib, respectively. We then performed transcriptomic and mass spectrometry-based phosphoproteomics analyses on baseline and KRASG12C-GDP inhibitor-resistant samples to determine resistance and escape mechanisms. Results: In the sotorasib-R LU65 cells, we discovered upregulation of various RTKs including HER2, HER3, and AXL using a mass spectrometry-based proteomics approach and Immunoblot analysis. Simultaneously, from a transcriptome analysis, we observed activation of RAS and PI3K/AKT signaling in these cells. In the adagrasib-R LUN156 model, increased phosphorylation of MET was observed via phospho-RTK array and by immunoblotting. Transcriptomic analysis revealed an enrichment for RAS pathway dependency in the adagrasib-R tumor models. RAS GTP-binding assessed by RAF-RBD pulldown and multiple reactions monitoring mass-spectrometry suggest increased GTP-bound RAS isoforms in sotorasib-R LU65 cells and active RAS signaling in adagrasib-R LUN156. Given the convergence of our findings on re-activation/maintenance of wild-type RAS signaling as a means of resistance to KRASG12C-GDP-state inhibitors, we hypothesized that RMC-7977, a tri-complex RASMULTI-GTP inhibitor, which inhibits signaling via mutant and wild-type RAS, had the potential to counteract these mechanisms. We tested RMC-7977 monotherapy, which drove complete tumor regressions in the adagrasib-R LUN156 model. Additionally, RMC-7977 attenuated tumor growth in sotorasib-R cell derived LU65 xenograft model wherein we observed co-activation of PI3K/AKT signaling. Thus, we tested a combination with the pan-PI3K inhibitor pictilisib and observed combinatorial activity consistent with our findings. Conclusions: These data suggest that in KRASG12C-GDP inhibitor-resistant models RTK activation maintains MAPK dependency and in the case of one model, PI3K signaling. Consistent with these mechanisms, RMC-7977 as a single agent or in combination with pictilisib drove significant tumor regressions in these models. These preclinical results indicate RASMULTI-GTP inhibition alone or combination with PI3K inhibition has the potential to address KRASG12C-GDP inhibitor resistance. Citation Format: Hitendra S. Solanki, Harshit Shah, Denis Imbody, Bina Desai, Paul A. Stewart, Bin Fang, Yaakov Stern, Lancia N. Darville, John M. Koomen, Andriy Marusyk, Ethan Ahler, Ida Aronchik, Mallika Singh, Eric B. Haura. RTK signaling and WT RAS activity as vulnerabilities in tumors with acquired resistance to GDP-state selective KRASG12C inhibitors in preclinical models abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 1924.