Potent and specific aryl hydrocarbon receptor (AhR) antagonist. Displays no AhR agonist activity (at concentrations up to 100 μM). Blocks binding of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) to the AhR in a dose-dependent manner; also blocks TCDD-mediated translocation and DNA-binding activity of the AhR.