FDA approves overactive bladder agent with new mechanism of action

The FDA has approved the once-daily oral beta-3 adrenergic agonist mirabegron (Myrbetriq) for the treatment of overactive bladder with symptoms of urge urinary incontinence, urgency, and urinary frequency.

Mirabegron is the first oral OAB treatment with a distinct mechanism of action since the launch of anticholinergic drugs 30 years ago.

"OAB impacts each individual differently, so it is important to have a variety of treatment options available," said Victor Nitti, MD, of New York University Langone Medical Center, New York. "With Myrbetriq, U.S. physicians now have a new therapy option to offer many Americans living with overactive bladder."

Mirabegron relaxes the detrusor smooth muscle during the storage phase of the urinary bladder fill-void cycle by activation of beta-3 adrenergic receptors that increase bladder capacity.

The drug’s approval was based on safety and efficacy data from three placebo-controlled phase III studies, in which treatment with mirabegron, 25 mg and 50 mg, resulted in statistically significant improvement in efficacy parameters of incontinence episodes and number of urinations per 24 hours.

In treatment with mirabegron, 25 mg, incontinence episodes were reduced by 1.36 episodes from a baseline of 2.65, a statistically significant reduction of 0.40 versus placebo in 12 weeks. The number of urinations was reduced by 1.65 urinations from a baseline of 11.68, a statistically significant reduction of 0.47 versus placebo in 12 weeks.

With mirabegron, 50 mg, incontinence episodes were reduced by 1.49 episodes from a baseline of 2.71, a statistically significant reduction of 0.40 versus placebo in 12 weeks. Number of urinations was reduced by 1.65 urinations from a baseline of 11.68, a statistically significant reduction of 0.47 versus placebo in 12 weeks.

Mirabegron will be supplied in 25 mg and 50 mg extended-release tablets and is expected to be available in pharmacies in the fourth quarter of 2012.

Dr. Nitti has served as a consultant and investigator for Astellas Pharma.

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