Oncogenic Kras targeting with MRTX1133 or Daraxonrasib specifically synergize with anti-CTLA4 to promote anti-tumor immunity in pancreatic cancer

Lack of sustained response to oncogenic Kras (Kras*) inhibition in pancreatic ductal adenocarcinoma (PDAC) underscores the need to identify effective combination therapies. Here, we demonstrate that Kras* targeting using MRTX1133 or Daraxonrasib recruits diverse T-cell infiltrates, including regulatory (Tregs), effector and exhausted T cells into the PDAC microenvironment. Kras* inhibition induces T-cell influx and offers a therapeutic window to specifically prime PDAC to anti-CTLA4 immune checkpoint blockade efficacy, in contrast to anti-PD1, anti-Tim3, anti-Lag3, anti-Vista, and anti-4-1BB agonist combination therapy. Mechanistically, anti-CTLA4 combination therapy transcriptionally reprograms effector Tregs to a naive phenotype, reverses CD8+ T-cell exhaustion, and promotes recruitment of functional tertiary lymphoid structures to mediate anti-tumor immunity. Single-cell ATAC sequencing reveals that Treg reprogramming by anti-CTLA4 is epigenetically regulated by downregulation of AP-1 family transcription factors in the IL-35 promoter region. This study reveals an actionable vulnerability in the adaptive immune response in Kras* targeted PDAC with immediate clinical implications. Kras mutations have been associated with immune suppression in pancreatic cancer. Here the authors show that KRAS targeting with MRTX1133 or Daraxonrasib specifically synergizes with anti-CTLA4, but not other immune checkpoint inhibitors, in inducing tertiary lymphoid structures and promoting anti-tumor immune responses in preclinical pancreatic cancer models.