GTx, Inc. (Nasdaq: GTXI) announced the presentation today of results of a preclinical study demonstrating that Capesaris™ (GTx-758) treatment achieved and maintained castration over the entire 9 month study without evidence of gynecomastia in male cynomolgus monkeys. The data were presented at the Annual Meeting of the American Urological Association.

Capesaris is a novel, orally available selective estrogen receptor alpha agonist small molecule which GTx is developing for first line treatment of advanced prostate cancer. Capesaris has the potential to achieve and maintain medical castration in men with advanced prostate cancer without causing estrogen deficiency side effects such as bone loss and hot flashes. Estrogen deficiency is an unintended consequence of androgen deprivation therapy (ADT) by LHRH agonist or antagonist treatment or by surgical castration, which are currently available first line hormonal treatments for advanced prostate cancer. Estrogen deficiency can result in bone loss and increased risk of fractures, hot flashes, adverse lipid changes and increased risk of cardiovascular disease, and loss of libido.

Gynecomastia, the enlargement of male breast tissue, is another common side effect of currently available ADT and also of bicalutamide monotherapy.

In the preclinical monkey study, Capesaris and diethylstilbestrol (DES), an orally available nonselective estrogen agent which has been used for ADT, each reduced serum testosterone to castrate levels (

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