Mepitiostane

Mepitiostane (INN, JAN) (brand name Thioderon), also known as epitiostanol 17β-methoxycyclopentyl ether, is a steroidal antiestrogen, androgen, and anabolic steroid that is used in Japan as an antineoplastic agent in the treatment of breast cancer and is also used in the treatment of anemia of renal failure. It is the 17-methyloxycyclopentyl ether of epitiostanol, and acts as an oral prodrug to it. Mepitiostane is described as similar to tamoxifen as an antiestrogen, and through epitiostanol, binds directly to and antagonizes the estrogen receptor. A series of case reports have found it to be effective in the treatment of an estrogen receptor-dependent meningiomas. The drug shows a high rate of virilizing side effects such as acne, hirsutism, and voice changes in women. It was patented and described in the literature in 1968.