<unk>  is believed to be the endogenous ligand (a substance that naturally occurs in the body that activates this receptor) for retinoid X receptor, but it also activates the retinoic acid receptor.
Alitretinoin
Tretinoin
Isotretinoin
Clobetasol
Clobetasol propionate
Ulobetasol propionate
Urodilatin
Cortistatin 