Quarterly LHRH agonist deters testosterone increase

November 1, 2005

Vancouver, British Columbia--A newer 3-month formulation of an LHRH agonist shows efficacy and safety similar to its 1-month counterpart. However, the 3-month version of the drug, triptorelin pamoate (Trelstar LA) provides a more convenient option preferred for maintaining compliance and quality of life in patients with stages C and D prostate cancer, researchers say.

"A 3-month formulation of triptorelin pamoate microgranules is as safe and efficacious as a monthly dose in men with advanced prostate cancer," said Michael Brawer, MD, director of the Northwest Prostate Institute in Seattle.

Dr. Brawer presented the results of a phase III study comparing the two formulations at the AUA Western Section annual meeting here. In a related study, Dr. Brawer and colleagues found that the 1-month formulation of triptorelin, 3.75, and leuprolide acetate (Lupron), 7.5 mg once every 28 days, were equivalent in achieving and maintaining castration levels at 9 months.

Adverse events were reported by 98% of patients in the 3-month group, but they did not result in any withdrawals from the study. The most common adverse events were hot flushes (73%), back pain (36%), headache (25%), and skeletal pain (24%). In addition, both groups of men reported an average 5 kg weight gain. The drug was well tolerated in both treatment groups. Bone pain and quality of life scores were unchanged from baseline to the endpoint, Dr. Brawer said.

T levels maintained

Desensitization of gonadotropin receptors and a sustained reduction in PSA levels were achieved by day 85 of the treatment in both groups, Dr. Brawer said. Serum PSA scores were <10.0 ng/mL by day 46 in both groups. Testosterone levels in 94% of patients in the 3-month formulation group were maintained at <1.735 nmol/L and in 95% of men in the 1-month group for 2 to 9 months.

Triptorelin did not accumulate in patients receiving the 3-month formulation.

In the second study, testosterone levels in 91.2% of patients receiving triptorelin and 99.3% of patients receiving leuprolide decreased to below castration values by day 29, and castration was achieved in 97.7% and 97.1% of patients, respectively, by day 57. Through month 9, castration was maintained in 96.2% of triptorelin patients and 91.2% of leuprolide patients, Dr. Brawer reported.

Dr. Brawer serves on the advisory board of Watson Pharmaceuticals.