<qa>  What is the name of the enzyme that converts tryptophan to kynurIDO is an enzyme that converts the essential amino acid tryptophan to kynurenine. The availability of tryptophan is essential to sustaining both helper T cell and effector T cell activation. Overexpression of IDO by tumor cells or antigen presenting cells serves to arrest T cell activation thus acting as an immunosuppressive enzyme. Epacadostat INCB024360 is an inhibitor of the enzyme indoleamine 2,3-dioxygenase 1 IDO1 that has shown promise in the treatment of solid tumors and lymphomas in ongoing Phase III studies. 