Abstract 1938: WEE1 inhibition prevents and overcomes resistance to KRAS inhibitors in lung cancer by enhancing MCL1-mediated apoptosis

Abstract Background: While novel covalent inhibitors of KRAS G12C have been approved in non-small-cell lung cancer (NSCLC), their efficacies are known to be limited. To enhance the therapeutic potential of KRAS inhibitors, combination strategies need to be developed. In this study, we conducted a large-scale screening to identify novel combination partners that induced synergistic efficacy with KRAS inhibitors. Additionally, mechanistic analyses were conducted to clarify the synergistic effects in combination and their role in conferring resistance to KRAS inhibitors. Methods: To identify novel combination partners of KRAS inhibitors, we conducted high-throughput screening (HTS) using a chemical library composed of 1,400 kinase inhibitors. Sotorasib was used as a KRAS inhibitor. Anti-proliferative and apoptotic effects in vitro were assessed by ATP-based cell viability assay, and caspase 3/7 assay and/or Annexin V assay, respectively. Protein expression levels were assessed by immunoblotting. In vivo studies were performed using a H358 xenograft nude mouse model and a patient-derived xenograft model (PDX). PDX samples were provided by the National Cancer Center J-PDX library, Japan. Results: HTS identified the WEE1 inhibitor AZD1775, a G2/M checkpoint abrogator in clinical-stage development, as a promising combination partner of KRAS inhibitors in KRAS G12C mutant NSCLC. Synergistic effects of KRAS and WEE1 inhibitors were confirmed across multiple KRAS G12C mutant NSCLC cell lines, independently of their co-occurring oncogenic mutation profiles. The combination treatment enhanced apoptotic cell death, being upregulated pro-apoptotic protein BIM, while downregulated anti-apoptotic protein MCL1. In vivo efficacy studies in combination with sotorasib and AZD1775 also demonstrated remarkable tumor regression and durable response in both CDX and PDX models. We also generated sotorasib-resistant H23 (H23-SR) cells, confirming upregulation of both WEE1 and MCL1 in the resistant cells. Ectopic overexpression of WEE1 in H23, on the contrary, conferred resistance to sotorasib. Furthermore, WEE1 inhibition re-sensitized H23-SR cells to KRAS inhibitors. Conclusion: Our results suggest that the WEE1-MCL1 axis plays an important role in both the initial therapeutic efficacy and the acquired resistance to KRAS inhibitors. These findings could pave the way for a novel therapeutic strategy for KRAS G12C mutant NSCLC. Citation Format: Gaku Yamamoto, Kosuke Tanaka, Ryo Kamata, Takehiro Nakao, Shunta Mori, Jie Liu, Susumu S. Kobayashi, Akihiro Ohashi. WEE1 inhibition prevents and overcomes resistance to KRAS inhibitors in lung cancer by enhancing MCL1-mediated apoptosis [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(6_Suppl):Abstract nr 1938.