Cyproterone acetate is an androgen receptor (AR) antagonist with IC50 of 7.1 nM, as well as a weak progesterone receptor agonist with weak pro-gestational and glucocorticoid activity.
Target: Androgen Receptor
Cyproterone acetate clearly shows antagonistic properties, while being a partial agonist also, showing agonism for the AR, with EC50 of 4.0 μM, at relatively high concentrations [1]. In the presence of 10 nM Testosterone, low concentrations of Cyproterone acetate inhibits T-stimulated transcription of 3XHRE-LUC, but at higher concentrations, transcription is stimulated. LH levels in Cyproterone acetate-treated rats do not dip below pretreatment levels, although they does not increase as much in the rats treated with 3.2 mg Cyproterone acetate/kg/day as in those which received 0.2 mg Cyproterone acetate/kg/day [2]. Cyproterone acetate exhibits direct negative effect on reproductive organs weight and significant reducing effect on sperm count and Ca2+ contents. SOD and GST activities significantly decrease in addition to significant increase in NO, MDA contents reflecting the oxidative status of testis in Cyproterone acetate treated rats [3].
 

17 alpha-propionate

17 alpha-propionate(CB-03-01) is a new topical and peripherally selective androgen antagonist.
IC50 value:
Target: Androgen Receptor
17 alpha-propionate (CB-03-01) is a new potent topical antiandrogen potentially useful in acne vulgaris. CB-03-01 1% cream was very well tolerated, and was significantly better than placebo regarding TLC (P = 0·0017), ILC (P = 0·0134) and ASI (P = 0·0090), and also clinically more effective than comparator. The product also induced a faster attainment of 50% improvement in all the above parameters.