AGN 193109 is a highly effective antagonist of retinoic acid receptors, with Kds of 2 nM, 2 nM, and 3 nM for RARα, RARβ, and RARγ, respectively. AGN 193109 is completely RAR specific, because it does not bind to or transactivate through any of the RXRs. AGN 193109 (100 nM) inhibits the TTNPB (a retinoic acid receptor agonist)-dependent morphological change in ECE16-1 cells. AGN193109 half-reverses retinoid-dependent growth suppression at 10 nM, and completely shows this effect at 100 nM in ECE16-1 cells. AGN193109 (100 nM) also eliminates TTNPB-induced decrease in levels of K5, K6, K14, K16, and K17 and increase in levels of K7, K8, and K19.