Retinoid drugs find major applications in the topical treatment of cutaneous proliferative disorders such as acne, psoriasis, and photoaging and cutaneous cancers such as cutaneous Tâcell lymphoma (CTCL) and Kaposi's sarcoma. Oral retinoids are successfully used to treat nodular/cystic acne, systemic CTCL, and acute promyelocytic leukemia. This overview of available retinoid drugs and those in the preclinical or clinical pipeline covers their development, indications, clinical trial results, adverse effects, and pharmacology/metabolism. Retinoids have been described historically and functionally in the context of interaction with their nuclear receptorsâretinoic acid receptors (RARs) and retinoid X receptors (RXRs)âin inducing gene transcription. RARâselective retinoids or their prodrugs include firstâgeneration allâ
trans
âretinoic acid (tretinoin) and its 13â
cis
isomer (isotretinoin), and secondâgeneration acitretin and its ethyl ester (etretinate), both having an aromatic 2,3,6âtrimethylâ4âmethoxyphenyl terminus. Thirdâgeneration more aromatic analogs include ethyl ester tazarotene (TazoracÂŽ) and adapalene (DifferinÂŽ), both selective for RAR subtypes β and Îł, and RARÎąâselective pipeline candidates Am80 and NRX 195183, which are in clinical trials. RAR and RXR transcriptional panagonist 9â
cis
âretinoic acid is next and is followed by RXRâselective bexarotene (Targretinâ˘) and two RXRâselective clinical trial candidates, 9cUAB and NRX 194204. The fourth generation includes three compounds that may have applications in the treatment or prevention of cancer. While originally considered as retinoids, such as
N
â(4âhydroxyphenyl) retinamide, or as retinoidârelated or derived, such as ST1926 (AHPC) and SHetA2, they subsequently were found to function independently of the RARs and RXRs in inhibiting cancer cell proliferation and inducing apoptosis.