ERA-45 (original) (raw)

ERA-45 is a synthetic estrogen and a selective agonist of the ERα. It shows 286-fold selectivity for transactivation of the ERα over the ERβ, with EC50 values of 0.37 nM for the ERα (7-fold weaker than estradiol) and 13 nM for the ERβ (20,000-fold weaker than estradiol). However, another found only about 35-fold potency for transactivation of the ERα over the ERβ. The drug has no antagonistic activity at either receptor. ERA-45 induced prostate cancer development in preclinical models when it was given in combination with testosterone, whereas testosterone alone did not do so. In contrast, the selective ERβ agonist ERB-26 was protective against the development of prostate cancer produced by these two drugs. These findings suggest opposing roles of the ERα and ERβ in the prostate gland. The