Watson Pharmaceuticals has received approval from the US Food and Drug Administration (FDA) for a new twice-yearly formulation of TRELSTAR, making the drug the only six-month intramuscular GnRH agonist available to treat prostate cancer.

Predicted for a May launch, the new, longer-acting six-month formulation is designed to provide patients and physicians with a more convenient therapeutic option that is well tolerated and as effective.

TRELSTAR is administered via the MIXJECT delivery system, which uses a thin (21-gauge) needle, offering easy administration with low incidence of injection site pain.

Watson Global Brands executive vice-president Fred Wilkinson said that the unique combination of convenience, reliable testosterone and PSA suppression, and injection site tolerability will provide an important treatment option.

“We plan to further evaluate and quantify the unique injection site tolerability this product offers compared to other commonly used GnRH agonists later this year,” Wilkinson said.

Approval is based on a 12-month (48-week) Phase II study over which TRELSTAR 22.5mg produced a mean testosterone serum level of 12.8ng/dL from month two to month 12, well below castration levels associated with androgen deprivation therapy.