Abstract 4574: Next generation nuclear export blocker KPT8602 synergizes with KRASG12D inhibitor MRTX1133 resulting in improved antitumor effects against pancreatic ductal adenocarcinoma

Abstract Introduction: A novel KRAS inhibitor, MRTX1133, specifically targeting the G12D isoform, prevalent in pancreatic ductal adenocarcinoma (PDAC), holds promise for a substantial PDAC patient population. Nevertheless, given the clinical experience with sotorasib (a KRASG12C inhibitor) in lung cancer, it's anticipated that resistance to the KRASG12D inhibitor will eventually emerge in most PDAC patients. This underscores the need to identify strategies that can enhance the efficacy of KRAS inhibitors in PDAC. Emerging evidence suggests that the nuclear export protein exportin 1 (XPO1) is a druggable vulnerability in KRAS mutant cancers. XPO1 plays a pivotal role in shuttling various critical tumor suppressors, genome surveillance proteins, and transcription factors out of the nucleus and is frequently overexpressed in various cancers, including PDAC. In this study, we employed both in vitro and in vivo models to assess the potential of KPT8602, an investigational and next-generation selective XPO1 inhibitor, to synergize with the KRASG12D inhibitor MRTX1133 and sensitize MRTX1133-resistant PDAC cells. Methods: We examined the cytotoxic and molecular effects of KRASG12D inhibitor MRTX1133 in combination with nuclear export blocker KPT8602 in KRASG12D mutant 2D and 3D cellular/spheroid models. The preclinical antitumor efficacy of the combination was evaluated in a KRASG12D mutant PDAC cell derived xenograft (CDX) model. Results: KPT8602 synergized with MRTX1133 in vitro yielding suppressed proliferation of KRASG12D mutant PDAC cells. Similar synergistic effects were also seen in 3D cultures of KRASG12D mutant PDAC cancer cell lines and patient derived primary tumor cells where the combination suppressed spheroid formation and reduced spheroid viability. Also, the combination inhibited the clonogenic potential of KRASG12D mutant PDAC cells. In addition, we developed a PDAC cell line resistant to MRTX1133 and observed that such MRTX1133-resistant cell line was acutely sensitive to treatment with KPT8602. Mechanistically, KPT8602 and MRTX1133 combination led to reduction in protein expression of KRAS downstream effectors and cell cycle markers. Furthermore, a combined administration of KPT8602 and MRTX1133 at sub-optimal doses resulted in remarkable tumor growth inhibition in a KRASG12D mutant HPAC CDX mice model. Moreover, KPT8602 as a maintenance therapy also prevented tumor relapse. Conclusion: This is the first study demonstrating that nuclear export blocker KPT8602 can synergize with KRASG12D inhibitor MRTX1133 and has the potential to target MRTX1133-resistant PDAC cells. This study provides a rationale for combining MRTX1133 with KPT8602 for the treatment of PDAC patients with KRASG12D mutant tumors. Citation Format: Husain Yar Khan, Amro Aboukameel, Md Hafiz Uddin, Sahar F. Bannoura, Khaled Keffri, Medha Jasti, Rachael Virga, Sarah Motorwala, Khalil Choucair, Tarik Hadid, Mohammad Najeeb Al-Hallak, Eliza Beal, Miguel Tobon, Rafic Beydoun, Greg Dyson, Steve Kim, Misako Nagasaka, Philip A. Philip, Basel El-Rayes, Herbert Chen, Anthony Shields, Ramzi Mohammad, Boris Pasche, Asfar Azmi. Next generation nuclear export blocker KPT8602 synergizes with KRASG12D inhibitor MRTX1133 resulting in improved antitumor effects against pancreatic ductal adenocarcinoma 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 4574.