Ex vivo lipopolysaccharide (LPS) plus IFN-γ stimulation of whole blood samples from patients enrolled on a phase I trial in advanced cancers recently showed that > 90% inhibition of IDO1 could be achieved in a dose-dependent manner, and it was well tolerated with grade 1-2 fatigue as the most common adverse event [25, 26]. This evidence concerns the gene IFNG and cancer.