The combination of BCL-xL PROTAC and mTOR inhibitor sensitizes pancreatic ductal adenocarcinoma to KRAS G12D inhibitor treatment by enhancing apoptosis induction

ABSTRACT Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive cancer with a five-year survival rate of approximately 13%, partly because of limited treatment options and resistance to therapies. Although the recently discovered KRAS G12D inhibitor MRTX1133 has shown promise for PDAC treatment in preclinical studies, its clinical efficacy as a single agent is expected to be limited, as is the case with KRAS G12C inhibitors. Therefore, in this study, we evaluated potential combination strategies to enhance the therapeutic effect of MRTX1133. We rationally combined MRTX1133 with the BCL-xL proteolysis-targeting chimera (PROTAC) DT2216 and the mTOR inhibitor everolimus, which significantly potentiated the anti-tumor activity of MRTX1133 in multiple G12D-mutated PDAC cells in vitro by enhancing apoptosis induction. Mechanistically, MRTX1133 treatment increased BIM and decreased NOXA levels, while the combination of DT2216/everolimus was shown to simultaneously enhance BIM release and stabilize NOXA. In vivo, DT2216/everolimus combination significantly potentiated the anti-tumor activity of MRTX1133 in AsPC1 PDAC xenograft model. Furthermore, the triple combination of MRTX1133, DT2216, and everolimus effectively overcame acquired resistance to MRTX1133 in AsPC1 cells in vitro and in xenograft model. Collectively, our findings suggest that the single-agent efficacy of MRTX1133 is limited by apoptosis inhibition, and that its combination with DT2216/everolimus can enhance apoptosis and potentially overcome resistance in KRAS G12D-mutated PDAC. SIGNIFICANCE KRAS inhibitors, including KRAS G12D inhibitor MRTX1133, are promising therapeutics against KRAS-mutated pancreatic ductal adenocarcinoma (PDAC), but drug resistance limits their efficacy. Our study reveals that robust induction of apoptosis using a combination of BCL-xL PROTAC degrader and an mTOR inhibitor, significantly enhances MRTX1133 efficacy in PDAC models without increasing toxicity to normal tissues. Competing Interest Statement P. Zhang , G. Zheng, D. Zhou and S. Khan are inventors of patent applications for the use of BCL-xL PROTACs (including DT2216) as antitumor agents. G. Zheng and D. Zhou are co-founders of and have equity in Dialectic Therapeutics, which develops BCL-xL PROTACs to treat cancer.