GTx, Inc. (Nasdaq: GTXI) has conducted a number of clinical trials using toremifene citrate in both the treatment of breast and prostate cancer. Older women and men as well as women and men being treated for both breast and prostate cancers are subject to bone loss leading to an increased risk of falls and fractures.

Androgen deprivation therapy (ADT) escalates the rate of bone loss in men as it “turns off” the production of testosterone. Toremifene is an experimental drug which is hoped will slow down the loss of bone mineral density. In an on-going phase III trial being conducted to evaluate toremifene’s ability to protect bones against loss, there has been an unexpected result. Perliminary results show that toremifene might have the ability to slow down PSA progression in men being treated for advanced prostate cancer.

Among men in the treatment population with a detectable PSA (PSA ? 1 ng/ml) at baseline (n=419), significantly fewer men treated with toremifene 80 mg had PSA progression over time compared to men taking placebo (27% versus 37%, respectively).

Additionally, “The new safety data is consistent with the mechanism of action observed in other studies evaluating toremifene, which have demonstrated inhibition of prostate growth in animal models, as well as in our Phase IIb clinical trial evaluating toremifene for the prevention of prostate cancer,” said Mitchell S. Steiner, MD, Chief Executive Officer of GTx., Dr. Steiner also said “It is encouraging to find that in our Phase III clinical trial in men with advanced prostate cancer on ADT, who have castrate levels of testosterone and estrogen, toremifene 80 mg treatment resulted in fewer men with detectable PSA at baseline demonstrating PSA progression over time when compared to placebo.”

This two year double-blind, placebo-controlled, randomized study of 1,389 ADT patients, was conducted at approximately 150 clinical sites in the United States and Mexico. The primary end points of the study did not include a PSA or survival analysis. If the positive PSA data continues on its current trend, there will need to be a new study of longer time duration looking specifically at PSA and survival curve data.

Joel T Nowak MA, MSW