Phase III, randomised, double-blind, placebo-controlled study of the β3-adrenoceptor agonist mirabegron, 50 mg once daily, in Japanese patients with overactive bladder.

OBJECTIVE

To evaluate the efficacy and safety of the β3-adrenoceptor agonist mirabegron, in a Japanese population with overactive bladder (OAB).

PATIENTS AND

METHODS

This randomised, double-blind, placebo-controlled phase III study enrolled adult patients experiencing OAB symptoms for ≥24 weeks. Patients with ≥ 8 micturitions/24 h and ≥1 urgency episode/24 h or ≥1 urgency incontinence episode/24 h were randomised to once-daily placebo, mirabegron 50 mg or tolterodine 4 mg (as an active comparator, without testing for non-inferiority of efficacy and safety) for 12 weeks. The primary endpoint was the change in the mean number of micturitions/24 h from baseline to final assessment. Secondary endpoints included micturition variables related to urgency and/or incontinence and quality-of-life domain scores on the King's Health Questionnaire. Safety assessments included adverse events (AEs), post-void residual urine volume, laboratory variables, vital signs and 12-lead electrocardiogram.

RESULTS

A total of 1139 patients were randomised to receive placebo (n = 381), mirabegron 50 mg (n = 380) or tolterodine 4 mg (n = 378). Demographic and baseline characteristics were similar among the treatment groups. At final assessment, mirabegron was significantly superior to placebo in terms of mean [sd] change from baseline in number of micturitions/24 h (-1.67 [2.212] vs -0.86 [2.354]; P < 0.001) and mean [sd] change from baseline in number of urgency episodes/24 h (-1.85 [2.555] vs -1.37 [3.191]; P = 0.025), incontinence episodes/24 h (-1.12 [1.475] vs -0.66 [1.861]; P = 0.003), urgency incontinence episodes/24 h (-1.01 [1.338] vs -0.60 [1.745]; P = 0.008), and volume voided/micturition (24.300 [35.4767] vs 9.715 [29.0864] mL; P < 0.001). The incidence of AEs in the mirabegron group was similar to that in the placebo group. Most AEs were mild and none were severe.

CONCLUSIONS

Mirabegron 50 mg once daily is an effective treatment for OAB symptoms, with a low occurrence of side effects in a Japanese population.