TOKYO, March 21, 2011 /PRNewswire/ -- Astellas Pharma Inc. ( today announced the results of two pivotal phase III clinical trials for mirabegron, the first of a new class of compounds under development for the treatment of overactive bladder (OAB), show mirabegron significantly improves key OAB symptoms - urinary incontinence and frequency of micturition.(1,2) These data were presented for the first time this week at the 26th annual congress of the European Association of Urology, in Vienna, Austria, 18-22 March 2011.

After 12 weeks treatment with once daily mirabegron, significant improvements from baseline were seen in the co-primary endpoints, incontinence episodes/24 hours and micturitions/24 hours, compared with placebo (p<0.05)(1,2). Significant improvements were also recorded in the key secondary endpoints - incontinence episodes/24 hours and micturitions/24 hours at week 4 of treatment (p<0.05 vs placebo), and volume of urine voided/micturition at the final visit (p<0.05 vs placebo)(1,2). In both studies, mirabegron was well tolerated with low levels of adverse events(1,2).

"The findings of these studies are very exciting. Mirabegron would represent the first oral OAB drug treatment with a completely new mode of action since the launch of oxybutynin several decades ago, and, if approved, would represent the first beta-3 adrenoceptor agonist to ever come to the market. Unlike antimuscarinics, mirabegron works by improving the storage capacity of the bladder. As these two studies suggest mirabegron has the potential to provide an effective new treatment option for OAB patients who continue to suffer from the distressing symptoms of incontinence and frequent need to pass urine" said Mr. Vik Khullar, from St. Mary's Hospital, Imperial College, London, and principal investigator of the European-Australian Phase III trial.

Mirabegron is a potent and selective beta-3 adrenoceptor (Beta3-AR) agonist which activates Beta3-ARs on the detrusor muscle of the bladder to facilitate filling of the bladder and storage of urine(3,4). It is being developed by Astellas whose global drug, Vesicare(R) (solifenacin) is currently one of the most widely used treatments for OAB(5).

"Vesicare has brought health benefits to people with OAB around the world since it was first launched in 2004, while mirabegron, with its different mode of action, complements Vesicare and is an important addition to our urology portfolio" said Masafumi Nogimori, President and Chief Executive Officer of Astellas Pharma Inc.

The new Phase III data confirm and support findings from smaller Phase II, dose-finding studies in which significant improvements were seen in a broad range of OAB symptoms, including incontinence episodes and micturition frequency(6,7).

"By improving symptoms through its action on beta-3 receptors, mirabegron offers an entirely different approach to existing OAB management which may provide good news for the many patients who are unable to achieve the right balance of efficacy and tolerability from current available treatments for OAB," said Dr. Victor Nitti, from NYU Langone Medical Center, New York, USA, and principal investigator of the North American Phase III trial.

Astellas submitted a market authorization application for mirabegron in Japan in June 2010, and Astellas expects it will be submitted to FDA and EMA later this year (July to September 2011).