A phase III, randomized, double-blind, parallel-group, placebo-controlled, multicentre study to assess the efficacy and safety of the β₃ adrenoceptor agonist, mirabegron, in patients with symptoms of overactive bladder.

Objective: To assess the efficacy and tolerability of mirabegron 25 mg and 50 mg once-daily vs placebo in patients with overactive bladder (OAB).

Materials And Methods: Patients ≥18 years with OAB symptoms were recruited to a 2-week, single-blind, placebo run-in. Those with ≥8 micturitions per 24 hours and ≥3 urgency episodes were randomized 1:1:1 to once-daily mirabegron 25 mg or 50 mg, or placebo for 12 weeks. Primary endpoints were changes to final visit in mean number of incontinence episodes and micturitions per 24 hours. Key secondary endpoints were changes to final visit in mean volume voided or micturition, change to week 4 in mean number of incontinence episodes and micturitions per 24 hours, changes to final visit in mean level of urgency, number of urgency incontinence episodes, and urgency (grade 3 or 4) episodes per 24 hours. Patient-reported outcomes were assessed using the OAB-questionnaire, Patient Perception of Bladder Condition, and Treatment-Satisfaction-Visual Analog Scale.

Results: Both mirabegron groups demonstrated statistically significant improvements in coprimary endpoints vs placebo. Mirabegron 50 mg demonstrated significantly greater improvements vs placebo in the following: change to final visit in mean volume voided per micturition and change to week 4 in mean number of incontinence episodes per 24 hours. Statistically significant improvements vs placebo were demonstrated by mirabegron 50 mg in all patient-reported outcome scales with no increase in the incidence of treatment-emergent adverse events vs placebo.

Conclusion: Mirabegron 25 mg and 50 mg were associated with significant improvements in efficacy measures of incontinence episodes and micturition frequency. Mirabegron was well tolerated vs placebo.