Jason Luke, MD, FACP, UPMC Hillman Cancer Center, Pittsburgh, PA, describes the role of the Indoleamine 2,3 dioxygenase (IDO) pathway in regulating immune function. The IDO pathway leads to several downstream events including the activation of the aryl hydrocarbon receptor (AHR), high levels of which are found in several types of human cancers and is associated with resistance to immune checkpoint inhibitors. Dr. Luke describes an ongoing Phase Ia/b trial (NCT04200963) investigating IK-175, an oral AHR inhibitor, alone and in combination with nivolumab, a PD-1 checkpoint inhibitor, in patients with locally advanced or metastatic solid tumors and urothelial carcinoma (UC). This Phase Ia/b trial aims to explore whether IK-175 will potentiate the immune activating effect of anti-PD-1 immunotherapy. This interview took place during the 36th Society for Immunotherapy of Cancer (SITC) Annual Meeting in Washington, D.C.