The investigators' pre-clinical data suggests that decitabine treatment in the KPC model of pancreatic cancer leads to a significant up-regulation of interferon-related genes and a polarization of the infiltrating immune cells. Based on these results, the investigators have evaluated the effect of single agent decitabine or anti-PD1H (a homologue of PD1 with very similar function and expression pattern) compared to combination therapy (treatment with decitabine followed by PD1 blockade). The investigators' preliminary results showed minimal effect of either agent alone on tumor growth but marked decrease in tumor progression in the combination arm. These results form the foundation of this phase II study.