HX531 is an effective RXR antagonist with oral activity, with an IC 50 of 18 nM, with activity against black melanoma. HC531 can eliminate the anti- apoptotic effects of all-trans-retinoic acid (t-RA) and exerts anti-obesity and anti-diabetic effects through leptin-dependent pathways and the p53-p21Cip1 pathway, resulting in G0/G1 cell cycle arrest.