IDO1 and neoplasm: IDO1 inhibitory activities and anti-tumor effects of epacadostat [19, 20], 1-methyl-L-tryptophan (1-L-MT) [21, 22] and RY103 [23–25] in CT26 colorectal cancer, KPIC pancreatic carcinoma, GL261 glioma and B16F10 melanoma mouse models have been demonstrated.