(2R,3S)-PD-1/PD-L1-IN-38 (Compound (±)-13e) is an orally active Ah receptor ( AhR ) antagonist with in vivo and in vitro anticancer activity. (2R,3S)-PD-1/PD-L1-IN-38 promotes the secretion of INF-γ by CD8 + T cells and inhibits the signal transduction of PD-1/PD-L1.