IDO1 and cancer: The rationale for this innovative approach is based on evidence that IDO inhibitors and certain chemotherapeutic agents synergize to drive more effective immune-mediated tumor clearance in mice [64-66]; indeed Phase I clinical trials in cancer patients to test the efficacy of the IDO inhibitor 1-methyl-[D]-tryptophan (D-1MT) as a vaccine adjuvant are underway at two US medical centers.