An orally bioavailable selective inhibitor of the aryl hydrocarbon receptor (AhR; class E basic helix-loop-helix protein 76; bHLHe76), with potential immunomodulating and antineoplastic activities. Upon oral administration, AhR inhibitor IK-175 specifically targets and binds to AhR, inhibits AhR activation, prevents AhR-mediated signaling, and AhR-dependent tumor cell proliferation. Abrogation of AhR activation prevents the activation of immune-tolerant dendritic cells (DCs), regulatory T-cells (Tregs) and decreases suppressive cytokines in the tumor microenvironment (TME). It stimulates cytotoxic T-cell activation and expansion. This may restore the immune response against tumor cells. AhR, a member of the basic helix-loop-helix/Per-Arnt-Sim (bHLH/PAS) family of transcription factors, plays key roles in regulating immunity and cellular differentiation. It mediates the expression of multiple immune related and tumor cell signal transduction and proliferation genes.