benorterone benorterone benorterone, also known by its developmental code name skf-7690 and as 17α-methyl-b-nortestosterone, is a steroidal antiandrogen which was studied for potential medical use but was never marketed. it was the first known antiandrogen to be studied in humans. it is taken by mouth or by application to skin. benorteroneclinical dataother namesskf-7690; fc-612; 17α-methyl-b-nortestosterone; 17α-methyl-b-norandrost-4-en-17β-ol-3-oneroutes ofadministrationby mouth, topicaldrug classsteroidal antiandrogenatc codenoneidentifiers iupac name (3s,3as,5as,5br,10ar,10bs)-3-hydroxy-3,3a,5b-trimethyl-1,2,4,5,5a,6,7,10,10a,10b-decahydrocyclopentafluoren-8-one cas number3570-10-3pubchem cid10039776chemspider8215340uniij339q7im54chemical and physical dataformulac19h28o2molar mass288.431 g·mol−13d model (jsmol)interactive image smiles cc12ccc(=o)c=c1cc3c2ccc4(c3ccc4(c)o)c inchi inchi=inchi=1s/c19h28o2/c1-17-7-4-13(20)10-12(17)11-14-15(17)5-8-18(2)16(14)6-9-19(18,3)21/h10,14-16,21h,4-9,11h2,1-3h3/t14-,15+,16+,17+,18+,19+/m1/s1key:rqetxcpbblhuib-ugczwrcosa-n pharmacology pharmacodynamics benorterone is an antiandrogen, or an antagonist of the androgen receptor (ar), the biological target of the androgen sex hormones testosterone and dihydrotestosterone. in one study, the affinity of benorterone for the ar was found to be about 5-fold greater than that of cyproterone acetate in rat prostate cytosol; the ki values were 0.7 nm for benorterone and 3.7 nm for cyproterone acetate, which were 243% and 46% of those of testosterone (ki = 1.7 nm), respectively. however, another study found that benorterone had only 11% of the affinity of dihydrotestosterone for the androgen receptor. although an antiandrogen, benorterone actually is a very weak partial agonist of the ar and has been reported to possess weak androgenic activity. the same is true for cyproterone acetate and other steroidal antiandrogens. unlike certain other steroidal antiandrogens such as cyproterone acetate, benorterone is not also a progestogen, instead being described as a selective and pure ar antagonist similarly to nonsteroidal antiandrogens such as flutamide and bicalutamide. however, although it is described as not being a progestogen, benorterone was found to produce "a highly variable decrease in plasma testosterone levels," indicating that it has weak antigonadotropic effects. the reasons for this are unclear, as other pure antiandrogens such as cyproterone (not cyproterone acetate) and flutamide do not do this and instead produce consistent increases in testosterone levels. however, it is notable that the anabolic steroid methyltestosterone, which benorterone differs from in chemical structure only by the removal of a carbon atom in the b ring, is aromatized into the estrogen methylestradiol and has potent estrogenic activity. estrogens are antigonadotropic similarly to androgens and progestogens and are likewise able to suppress testosterone levels. in accordance, the compound corresponding to what would be the aromatized form of benorterone, 17α-methyl-b-norestradiol, has been described and has been reported to possess estrogenic activity, although the aromatization of benorterone has not been assessed. a couple of studies found that prothrombin levels decreased by 50% in some patients treated with benorterone, although a causal relationship between this change and benorterone could not be shown. pharmacokinetics benorterone is active orally and topically and has been studied by both of these routes of administration. chemistry