Oxendolone

Oxendolone (INN, USAN, JAN) (brand names Prostetin, Roxenone; former developmental code name TSAA-291), also known as 16β-ethyl-19-nortestosterone or 16β-ethylestr-4-en-17β-ol-3-one, is a steroidal antiandrogen and progestin of the 19-nortestosterone group that has been marketed in Japan by Takeda for the treatment of benign prostatic hyperplasia (BPH) since 1981. It binds to the androgen receptor (AR) (K_i = 320 nM) and progesterone receptor (K_i = 20 nM) and acts as a weak but clinically relevant inhibitor of 5α-reductase (IC₅₀ = 1.4 μM). The binding affinity of oxendolone for the AR is far lower than that of cyproterone acetate. At the AR, oxendolone is not a silent antagonist but is rather predominantly antagonistic with weak agonistic activity; for this reason, it has been described as a selective androgen receptor modulator. The drug has antigonadotropic properties via its progestogenic actions. Although oxendolone is approved for the treatment of BPH in Japan, concerns have been raised about its use for this condition due to poor efficacy seen in clinical trials.