A phase II dose-ranging study of mirabegron in patients with overactive bladder.

INTRODUCTION AND HYPOTHESIS: Mirabegron is a potent and selective ß3-adrenoceptor agonist that may represent an alternative treatment option in place of antimuscarinics for patients with overactive bladder. METHODS: Patients completed a single-blinded, 2-week placebo run-in period followed by 12 weeks of randomized (n = 928) double-blinded treatment with mirabegron oral controlled absorption system (OCAS) 25, 50, 100, or 200 mg once-daily (QD), placebo or tolterodine extended release (ER) 4 mg QD. The primary endpoint was change from baseline to end-of-treatment in mean number of micturition episodes/24 h. Secondary endpoints included changes in mean volume voided per micturition; mean number of urinary incontinence, urgency urinary incontinence, and urgency episodes/24 h; severity of urgency; nocturia; and quality of life measures. Safety parameters included vital signs, adverse events, laboratory tests, electrocardiogram measurements and post-void residual volume. RESULTS: Mirabegron 25, 50, 100, and 200 mg resulted in dose-dependent reductions (improvements) from baseline to end-of-treatment in micturition frequency of 1.9, 2.1, 2.1, and 2.2 micturitions/24 h respectively, versus 1.4 micturitions/24 h with placebo (p ≤ 0.05 for the mirabegron 50-, 100-, and 200-mg comparisons). There was a statistically significant improvement with mirabegron compared with placebo for most secondary endpoints including quality of life variables. While there was a significant (p < 0.05) increase from baseline in pulse rate in the mirabegron 100-mg and 200-mg groups, this was not associated with an increased incidence of cardiovascular adverse events. CONCLUSIONS: The favorable efficacy and tolerability of mirabegron in this phase II dose-finding study has led to its successful advancement into a phase III clinical development program.

Mirabegron for the treatment of overactive bladder.

Overactive bladder (OAB) syndrome is defined as urinary urgency, usually accompanied by frequency and nocturia, with or without urge urinary incontinence, in the absence of urinary tract infection or other obvious pathology. Mirabegron (YM-178, Betanis®) is a novel, once-daily, orally active, first-in-class selective ß(3)-adrenoceptor agonist that improves symptoms associated with OAB by enhancing storage function and relaxing the urinary bladder. Mirabegron has been approved in Japan for the indication of urgency, urinary frequency and urge urinary incontinence associated with OAB, and was recently submitted for approval to U.S. and European authorities for the same indication. In phase III clinical trials performed in Europe, the U.S. and Australia, mirabegron at doses of 50 or 100 mg for 12 weeks significantly decreased the mean number of incontinence episodes and micturition episodes per 24 hours, and was safe and well tolerated. Mirabegron may be an alternative in patients with OAB who are poor responders to antimuscarinic agents or intolerant of their adverse effects.

Mirabegron, a ß3-adrenoceptor agonist for the potential treatment of urinary frequency, urinary incontinence or urgency associated with overactive bladder.

Mirabegron (YM-178), currently in development by Astellas Pharma Inc, is an orally active ß3-adrenoceptor (AR) agonist for the potential symptomatic treatment of overactive bladder (OAB). Mirabegron demonstrates nanomolar EC50 values against the human ß3-AR in biochemical assays with potent selectivity over the ß1- and ß2-ARs. Originally developed as a treatment for diabetes, the development of mirabegron was later refocused to OAB. Cystometric experiments in rats reported a reduction in resting intravesical pressure and contraction frequency in anesthetized rats, without any effect on the amplitude of micturition contraction. Mirabegron also reduced non-micturition bladder contractions in an awake rat model of bladder outlet obstruction. Top-line results from clinical trials to date indicate that mirabegron has been well tolerated with significant efficacy in reducing the number of incontinence episodes and mean micturition frequency in patients. Evidence of cytochrome P450 (CYP)2D6 inhibition in clinical trials highlighted a concern for pharmacokinetic interaction with other drugs that are CYP2D6 substrates, as confirmed by a rise in the pharmacokinetic parameters of desipramine with concomitant administration of mirabegron. Mirabegron exhibits a novel mode of action in targeting the ß3-AR for bladder relaxation, and the studies and trials conducted to date suggest mirabegron as a promising new treatment in the management of OAB symptoms, such as increased urinary urgency and frequency, and urgency incontinence.