Emerging clinical studies suggest that the use of IDO inhibitors, e.g., d-1-methyl-tryptophan and INCB24360 with classical chemo- or radiotherapy, and PCC0208009, INCB024360 and NLG919 could restore a correct immune response and provide a therapeutic response to generally resistant human neoplasms. The gene discussed is IDO1; the disease is neoplasm.