GTx, Inc. (NASDAQ: GTXI) announced today that new data from two Phase II studies on the effects of Capesaris ® (GTx-758), a selective estrogen receptor alpha agonist, for the treatment of advanced prostate cancer, will be detailed in presentations given by lead author, Evan Yu, MD, Associate Professor of Medicine, Fred Hutchinson Cancer Research Center, Seattle, Washington on February 14 and 15, at the 2013 American Society of Clinical Oncology (ASCO) Genitourinary (GU) Cancer Symposium in Orlando, Florida.
"These presentations highlight the significant and novel mechanistic findings of Capesaris," said Mitchell S. Steiner, MD, Chief Executive Officer of GTx. "The attributes demonstrated in these Phase II studies underscore the drug candidate’s potential to not only treat advanced prostate cancer by lowering testosterone in the microenvironment of prostate cancer cells, but also with fewer estrogen deficiency side effects relative to the standard of care for the treatment of advanced prostate cancer."
GTx-758 Significantly Reduced Free Testosterone and PSA Levels in Phase II Studies (Abstract #104)
In two Phase II clinical studies in men with advanced prostate cancer, patients receiving either 1000 mg or 2000 mg daily doses of GTx-758 demonstrated significant reductions in their serum free (unbound) testosterone (T) levels, with related reductions in their levels of serum prostatic specific antigen (PSA). One of the trials (705) compared the effects of 1000 mg and 2000 mg doses of GTx-758 in newly diagnosed advanced prostate cancer patients with a cohort of patients receiving leuprolide, an established androgen deprivation treatment (ADT). The primary endpoint of the trial was the proportion of men who achieved castration (i.e., a serum total T level less than 50 ng/dL) by Day 60. In hormone naïve advanced prostate cancer patients, 28 days of 1000 mg or 2000 mg daily GTx-758 or leuprolide therapy achieved castration in 49%, 56% and 94%, respectively. Although lesser reductions in serum total T were observed in men receiving either GTx-758 dose, larger decreases in serum free T were observed in these same men, as compared to leuprolide. Observed reductions in serum PSA at 28 days appear to be more strongly associated with the observed changes in free T, rather than total T, with PSA reductions of 84%, 73% and 56% from baseline for the 1000 mg and 2000 mg doses of GTx-758 and leuprolide, respectively. In men treated with GTx-758, sex hormone binding globulin (SHBG) levels increased approximately 400% and were associated with the decreases in serum free T and serum PSA.