IDO1 and cancer: Nevertheless, our results indicate an advantage of combining agonistic CD40 mAb therapy with IDO1-inhibitors, and support continued development of IDO1-inhibitors or alternative targeting of the Trp-Kyn-AhR pathway to block compensatory mechanisms from other tryptophan catabolizing enzymes.43 The present study also indicates that combining IDO1 vaccination with agonistic CD40-therapy might represent an attractive approach to treat cancer.