Benorterone

Benorterone (INN, USAN) (developmental code names SKF-7690, FC-612), also known as 17α-methyl-B-nortestosterone, is a steroidal, pure antiandrogen that was never marketed. Unlike other steroidal antiandrogens such as cyproterone acetate (CPA), it is not also a progestogen, instead acting as a selective androgen receptor antagonist similarly to non-steroidal antiandrogens such as bicalutamide. However, although it is described as not being a progestogen, benorterone was found to produce "a highly variable decrease in plasma testosterone levels" (the reasons for this are unclear, as other pure antiandrogens such as cyproterone (not CPA) and bicalutamide do not do this and instead produce consistent increases in testosterone levels).

Developed in the late 1950s and trialed in the 1960s, benorterone was the first antiandrogen to be studied in humans. The drug was found to be effective in the treatment of acne, seborrhea, and hirsutism in women, and unlike progestogenic antiandrogens such as CPA, seldom produced side effects in women, nor affected menstruation. However, in males, the drug produced gynecomastia (in 12 out of 13 young men), and upon the observance of this side effect, was soon withdrawn from clinical trials. Subsequently, CPA, which has a much reduced risk of gynecomastia by virtue of its concomitant progestogenic and antigonadotropic actions, was developed and introduced in 1973 instead.