Combination of PARP and KRASG12D inhibitors enhances therapeutic efficacy by exploiting vulnerabilities in PDAC

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy driven predominantly by KRAS mutations, with KRAS^G12D present in ~40 % of cases. Although the selective KRAS^G12D inhibitor MRTX1133 shows promising activity, monotherapy responses are incomplete and resistance emerges rapidly. In this study, we show that KRAS^G12D blockade suppresses homologous-recombination (HR) repair by downregulating BRCA1, RAD51, and RPA32, creating a state of HR deficiency that sensitizes PDAC cells to poly(ADP-ribose) polymerase (PARP) inhibition. Combined MRTX1133 and olaparib treatment produced synergistic cytotoxicity in vitro and durable tumor regression in vivo, even in MRTX1133-resistant models, and remodeled the tumor immune microenvironment with enhanced CD8⁺ T-cell infiltration. These findings demonstrate that co-targeting KRAS^G12D and PARP exploits an induced DNA-repair vulnerability to achieve synthetic lethality and immune activation in KRAS^G12D-driven PDAC.