Watson Pharmaceuticals, best-known as a generics company, has received approval from US regulators for Rapaflo, a new alpha blocker for the treatment of enlarged prostate.

The US Food and Drug Administration has given the thumbs-up to Rapaflo (silodosin), which was licensed for the North American market from Japan’s Kissei Pharmaceutical Co, for benign prostatic hyperplasia. The approval is based in part data from two Phase III, 923-patient trials who were randomised to receive either Rapaflo 8mg once-daily or placebo.

Treatment with silodosin resulted in “significant and rapid relief of BPH symptoms”, compared with placebo, as measured by the International Prostate Symptom Score. That includes irritative (frequency, urgency and nocturia) and obstructive (hesitancy, incomplete emptying, intermittency and weak stream) symptoms.

Watson chief executive Paul Bisaro said that Rapaflo’s approval “is the most important milestone for the company's brand division thus far". He added that the drug provides an excellent long-term opportunity for Watson and will be the foundation for future growth of our urology franchise”.

The company noted that BPH is the number one reason patients visit urologists and the market in the USA “is growing and currently exceeds $2 billion annually”. Of that, $1.7 billion is attributed to alpha blockers. Watson is planning a launch in early 2009 for silodosin, which is already available in Japan where it is sold in a twice-daily version by Kissei and Daiichi Sankyo.

Mr Bisaro added that Watson’s New Drug Application for oxybutynin gel for overactive is under consideration at the FDA and the firm plans to submit a supplemental NDA for its six-month formulation of the prostate cancer drug, Trelstar (triptorelin). He concluded by saying that “Watson is in a unique position to introduce products within the next 12 to 18 months that treat the top three conditions in urology."