Watson Pharmaceuticals, Inc., a leading specialty pharmaceutical company, announced positive top-line data from two phase 3 studies of silodosin, the company's investigational drug being studied for the treatment of signs and symptoms of benign prostatic hyperplasia (BPH).
The primary objective of the trials was to demonstrate that 8mg silodosin given once daily for 12 weeks was superior to placebo for the relief of BPH symptoms, including both obstructive and irritative symptoms, as measured by a baseline-to-endpoint change in the total score of the International Prostate Symptom Score-1 (IPSS-1). Secondary endpoints included improvements in maximum urine flow (Qmax). Very rapid and statistically significant improvements were seen in both of these endpoints.
Silodosin was well tolerated in both studies. Cardiovascular and blood pressure related side effects, including dizziness and orthostasis, were low in both trials. As expected with highly uroselective alpha blockers, ejaculations with little or no semen were the most commonly reported side effect seen in the trials. The vast majority of these reports were mild to moderate in intensity and patient withdrawal from the trial was low. Results from these studies will be submitted for presentation at a medical meeting at a later date.
"We are extremely encouraged with the efficacy that was demonstrated in these trials, supporting the potential clinical utility of silodosin in treating BPH," said Dr. Charles Ebert, Watson's Senior Vice President, Research and Development. "Our ongoing one year safety study remains on track to be completed this fall and we expect to submit a New Drug Application to FDA in the first half of 2008."
"The completion of the silodosin phase 3 studies is an important milestone for Watson," continued Dr. Ebert. "As BPH is one of the most commonly treated disorders by urologists, silodosin is expected to greatly enhance our growing urology franchise."
BPH is characterized by a non-cancerous enlarged prostate that leads to obstructive and irritative urinary symptoms. In the United States (US) BPH affects more than half of men in their sixties and as many as 90 percent of men by the age of 85. Additionally, approximately $1.7 billion is spent annually on BPH prescription drug treatment.
Silodosin is a novel, highly uroselective alpha (1A)-adrenoceptor antagonist originally developed by Kissei Pharmaceutical Co., Ltd. in Japan and licensed to Watson for the US, Canada and Mexico markets. Silodosin preferentially binds to the alpha (1A) receptors in the prostate and bladder neck relative to cardiovascular associated receptors, thereby maximizing target organ activity while minimizing the potential for blood pressure effects. Urief (silodosin) 4mg, dosed twice daily, was launched in Japan in May 2006 and is marketed in cooperation with Daiichi Pharmaceutical Co., Ltd.