Bifluranol

Bifluranol (INN, BAN) (brand name Prostarex) (former developmental code name BX-341) is an non-steroidal estrogen of the stilbestrol group related to diethylstilbestrol that is used as an antiandrogen in the United Kingdom in the treatment of prostate cancer. It is a polyfluorinated biphenyl that is related to polybrominated and polychlorinated biphenyls and diethylstilbestrol. The drug is described as a weak estrogen, and possesses about one-eighth the potency of diethylstilbestrol. In addition to prostate cancer, bifluranol has also been studied in and found to possess effectiveness in the treatment of benign prostatic hyperplasia.

In spite of the fact that it is widely referred to as an antiandrogen in the literature, bifluranol is actually a pure estrogen and does not significantly bind to the androgen receptor or directly antagonize the action of androgens. It exerts functional antiandrogen effects by binding to and activating the estrogen receptor in the pituitary gland, suppressing the secretion of luteinizing hormone (and hence acting as an antigonadotropin) and consequently reducing gonadal androgen production and systemic androgen levels. Bifluranol has also been found to act as a 17α-hydroxylase/17,20 lyase inhibitor, though with less potency than ketoconazole, and this action may contribute to its efficacy in prostate cancer by further helping to lower androgen levels.

Related drugs include pentafluranol (BX-430) and terfluranol (BX-428), which are also estrogens.