Astellas says it expects to file for regulatory approval of the overactive bladder (OAB) therapy mirabegron in the EU and U.S. during the early second part of 2011 on the back of positive data from two Phase III clinical trials. A marketing authorization application for the drug was filed in Japan in June 2010.
Data from the two reported Phase III studies showed that in comparison with placebo, once-daily mirabegron therapy led to significant improvements in the co-primary endpoints of incontinence episodes per 24 hours, and micturitions per 24 hours. Improvements in both endpoints were also seen after four weeks of treatment, and benefits were observed in terms of volume of urine voided per micturition at the final visit. Astellas points out the Phase III data support those from smaller Phase II dose-finding trials.
Mirabegron is a beta-3 adrenoceptor (beta3-AR) agonist that acts to facilitate bladder filling and storage of urine, the firm notes. If approved, the drug will complement Astellas’ existing muscarinic antagonist OAB therapy, Vesicare (solifenacin), which was first launched in 2004. The firm reported Vesicare sales of Yen 82.3 billion in fiscal 2009.
Regulatory clearance of mirabegron would make the drug the first beta-3 adrenoceptor agonist to reach the market, notes Vik Khullar from St. Mary’s Hopsital, Imperial College, London, who acted as principal investigator for the European-Australian Phase III study. “Mirabegron would represent the first oral OAB drug treatment with a completely new mode of action since the launch of oxybutynin several decades ago.”
“By improving symptoms through its action on beta-3 receptors, mirabegron offers an entirely different approach to existing OAB management,” adds Victor Nitti, M.D., from NYU Langone Medical Center in New York, who was principal investigator for the North American Phase III study. This would represent “good news for the many patients who are unable to achieve the right balance of efficacy and tolerability from current available treatments for OAB.”