Since M2-like macrophage that showed high expression of Arg-1 was one of the major immunosuppressive cell types in PDAC, we thus combined a small molecule compound Arg-1 inhibitor (PubChem CID 66833213) with anti-PD-1 antibody to treat KPC and PancO2 tumor-bearing mice. The gene discussed is ARG1; the disease is neoplasm.