5α-Dihydroethisterone
5α-Dihydroethisterone (5α-DHET; developmental code name HE-3562) is an active metabolite of the formerly clinically used but now-discontinued progestin ethisterone and the experimental and never-marketed hormonal antineoplastic agent ethynylandrostanediol (HE-3235).[1][2] Its formation from its parent drugs is catalyzed by 5α-reductase in tissues that express the enzyme in high amounts like the liver, skin, hair follicles, and prostate gland.[1][2][3] 5α-DHET has significant affinity for steroid hormone receptors and may contribute importantly to the activities of its parent drugs.[2] In regards to the estrogen receptors, 5α-DHET has weak affinity for the ERα of about 3.5% of that of estradiol, and does not bind to the ERβ (Ki > 10 μM).The steroidal antiandrogen zanoterone (WIN-49596), which was investigated in the 1990s for the treatment of benign prostatic hyperplasia but was never marketed, was derived from 5α-DHET.