Watson Pharmaceuticals announced that it has received approval from the FDA for its new six-month intramuscular formulation, Trelstar, a (triptorelin pamoate for injectable suspension) 22.5 mg. Trelstar 22.5 mg is a gonadotropin releasing hormone (GnRH) agonist used for the palliative treatment of advanced prostate cancer. It interrupts the production of testosterone to stem to growth of prostate cancer cells.

According to the information presented to the FDA, this new formulation maintains a mean testosterone levels similar those achieved with surgical castration. Trelstar 22.5 mg is expected to launch in this month according to representatives of Watson.

Trelstar 22.5 mg is designed to suppress testosterone for six months, it is now the only 6 month approved formulation. Trelstar was first approved in the United States in 2000 and is currently available in one-month (3.75 mg) and three-month (11.25 mg) formulations.

The approval is based on a 12-month phase III study. During the study, Trelstar 22.5 mg produced a mean testosterone serum level of 12.8 ng/dL from month 2 through month 12, well below castration levels associated with androgen deprivation therapy. They also reported that median PSA leve