GTx Presents Bone Turnover Marker Data and Additional PSA Progression Safety Analysis for Toremifene 80 mg Phase III ADT Clinical Trial
Tuesday September 16, 12:30 pm ET
MONTREAL--(BUSINESS WIRE)--GTx, Inc. (Nasdaq: GTXI - News) today presented a safety analysis demonstrating that fewer men treated with toremifene 80 mg had PSA progression over time compared to placebo in the Phase III clinical trial evaluating toremifene 80 mg for the treatment of multiple serious side effects of androgen deprivation therapy (ADT) for advanced prostate cancer. These data, as well as an additional analysis of bone turnover markers and fracture risk, were presented at the 2008 Annual Meeting of the American Society for Bone and Mineral Research in Montreal, Canada.
Among men in the intent-to-treat 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; p < 0.05). This subgroup analysis is consistent with the recommendations of the Prostate Cancer Clinical Trials Working Group to measure prostate cancer progression in clinical studies. In another analysis among men with an undetectable PSA (PSA < 1 ng/ml) at baseline (n= 698), there was no difference in PSA progression in men treated with toremifene 80 mg compared to men taking placebo.
“These new safety data are 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.
“In men with advanced prostate cancer, PSA is a sensitive marker of progression and is followed closely by physicians and patients to monitor the underlying cancer,” Dr. Steiner continued. “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.”
Additional data from the study were also highlighted during the presentation. An efficacy analysis studied changes in three serum markers of bone turnover: C-telopeptides, bone specific alkaline phosphatase (bALP), and osteocalcin. Changes in the three markers were further evaluated among men in the trial who experienced a new morphometric vertebral fracture. The analysis of these data show:
* Increases in C-telopeptides serum levels were associated with a significantly greater risk for the development of a new morphometric vertebral fracture (p < 0.01).
* Increases in bALP serum levels were associated with risk for new morphometric vertebral fracture (p < 0.01).
* Changes in osteocalcin serum levels were similar to those observed for other serum markers, but did not reach statistical significance.
About the toremifene 80 mg Phase III ADT clinical trial
The 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 endpoint was new morphometric vertebral fractures. Other key secondary endpoints included bone mineral density, lipid changes, hot flashes, and gynecomastia.
Safety
Toremifene 80 mg was well tolerated. Among the most common adverse events that occurred in over 2% of study subjects were joint pain (treated 7.3%, placebo 11.8%), dizziness (treated 6.3%, placebo 5.0%), back pain (treated 5.9%, placebo 5.2%), and extremity pain (treated 5.0%, placebo 4.4%). Venous thromboembolic events (VTE), which included both deep venous thrombosis and pulmonary embolism, were 2.4% in the toremifene 80 mg treated group and 1.02% in the placebo group. The majority of VTEs occurred in men at high risk for a VTE including: age greater than 80 years, history of VTE, recent surgical procedure and immobilization. Excluding high risk patients over the age of 80 years and with a history of VTEs, the VTEs were 1.3% in the toremifene 80 mg treated group and 1.0% in the placebo group (p=0.38). There was no difference in strokes, myocardial infarctions, or deaths between the two groups.
About GTx
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