AHR and cancer: Despite a robust read-across and weight of evidence approach, including early AhR-specific tiered screening assays, small molecule, and newer modality programs would likely require a 6-month transgenic (Tg.rasH2) mouse and 2-year rat bioassay study to assess carcinogenicity and support approval based on designation of the AhR as a susceptibility gene across various cancers and established procarcinogen action of specific AhR ligands (e.g., benzo(a)pyrene).