GTx Presents Preclinical Study Results Demonstrating That Capesaris™ (GTx-758) Chronic Treatment Does Not Cause Gynecomastia In Male Primates

Main Category: Prostate / Prostate Cancer
Also Included In: Urology / Nephrology
Article Date: 18 May 2011 - 9:00 PDT


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 (<50 ng/dL). Breast changes, including nipple enlargement, were noted within 2 weeks of treatment initiation for 100% of DES treated monkeys and continued throughout the study, whereas similar changes were not observed for monkeys treated with Capesaris.

"With a selective affinity for estrogen receptor alpha, Capesaris has the potential to achieve and maintain castrate levels of testosterone in men with advanced prostate cancer while avoiding estrogen deficiency side effects such as bone loss and hot flashes," said Dr. Ronald A. Morton, Jr., Chief Medical Officer of GTx. "These preclinical data provide encouragement that Capesaris, as a ER alpha agonist, may not cause gynecomastia."

GTx is planning to initiate this quarter an open label Phase IIb clinical trial evaluating Capesaris compared to Lupron Depot(R) (leuprolide acetate for depot suspension) in 156 men with advanced prostate cancer. The company expects to report data from the study in the fourth quarter.

Source:
GTx, Inc.

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