NSC 721648 is a cell-permeable benzothiazole compound that exhibits potent in vitro antiproliferative activity against HCC 2998, IGROV1, MCF-7, MDA 468, SR, and T-47D (GI50 <1 nM), while showing much reduced effect against 50 other human tumor cells in a panel screening. Although it is a high affinity AhR ligand (IC50 = 25 nM; Ki = 6.8 nM in a TCDD competitive binding study) and a known CYP1A1 inducer, neither property can fully account for its antitumor activity.
