Watson Pharmaceuticals Inc. said the Food and Drug Administration have asked for additional information on the company's new, long-term dose version of its prostate cancer drug, Trelstar, before the agency grants an approval.

In a so-called complete response letter, the FDA have requested clarification on clinical testing, chemistry, manufacturing and controls of the 24-week formulation of the testosterone-suppressing medicine. The company said they have also asked for additional information on Watson's third-party manufacturing of the injectable drug.

Trelstar, an injectable drug suppresses the production of testosterone and is used to treat prostate cancer patients whose condition has advanced. Currently available in four-week and 12-week doses, the drug is used in the cases of patients who are not candidates for surgery to remove the testicles, and for whom estrogen therapy is not feasible.

Watson had asked the FDA to approve a new, 22.5 milligram 24-week formulation of Trelstar, The new formulation suppresses testosterone production continuously for 24 weeks, lasting twice as long as Watson's current long-acting version of Trelstar.

Watson said it was working "expeditiously" to provide the requested information and hopes of earning approvals for the new, longer-formulation version of Trelstar.