Evidence available on the use of the selective β3-adrenoceptor agonist mirabegron for the treatment of overactive bladder

CONTEXT

Mirabegron, the selective β3-adrenoceptor agonist, heralds the latest development for the treatment of overactive bladder (OAB).

OBJECTIVE

To present the evidence available on the efficacy and tolerability of mirabegron and to discuss this treatment's potential in our setting.

EVIDENCE ACQUISITION

We reviewed 11 studies conducted with mirabegron in patients with OAB (2 phase II, 9 phase III), all studies were compared to placebo with 6 studies also including tolterodine as an additional arm. Greater emphasis shall be given to the main phase III trials performed in Europe, the USA and Australia evaluating efficacy and safety after 12 weeks (NCT00662909, NCT00689104, NCT00912964) and safety after 12 months (NCT00688688). The combined analyses of these 12 week studies is also available, with emphasis on global efficacy (FAS), efficacy with regard to incontinence (FAS i) and safety (SAF). More than 50% of patients had previously discontinued anticholinergics medication for OAB, thus allowing us to obtain data on the effectiveness of mirabegron in patients already treated with anticholinergics.

EVIDENCE SYNTHESIS

Mirabegron is an efficacious drug which presents a statistically significant reduction in the number of incontinence episodes and in urinary frequency as of 4 weeks, with a higher percentage of dry patients and a higher percentage of patients with reduction ≥50% in the number of incontinence episodes than placebo. The efficacy of mirabegron 50 and 100mg in the reduction of incontinence episodes occurs in de novo patients and who have received antimuscarinics, with adjusted mean difference and improvement in urinary frequency greater in treated patients. Its tolerability is very similar to placebo particularly for the adverse effects of the antimuscarinics (dry mouth, constipation and blurred vision). A minimal, non-clinically significant change is observed in systolic and diastolic blood pressure and pulse. Its efficacy is long-term. Mirabegron at the doses of 50 and 100mg presents an improvement versus placebo in patient satisfaction, health-related quality of life (HRQoL), symptom bother and patient's perception of bladder condition (PPBC). In the 12 week Phase III European study tolterodine delivered a lesser degree of improvement than mirabegron versus placebo in patient satisfaction, HRQoL, symptom bother and PPBC.

CONCLUSIONS

Mirabegron is the first of a new class of compounds with a novel mechanism of action that is different to the antimuscarinics. It presents significant and clinically important efficacy in the treatment of the symptoms of OAB. It has advantages with regard to the results described by the patient in treatment satisfaction. Studies on its combined use with anticholinergics are ongoing.

Mirabegron for the treatment of overactive bladder: a prespecified pooled efficacy analysis and pooled safety analysis of three randomised, double-blind, placebo-controlled, phase III studies

INTRODUCTION

To examine pooled efficacy data from three, large phase III studies comparing mirabegron (50 and 100 mg) with placebo, and pooled safety data including additional mirabegron 25 mg and tolterodine extended release (ER) 4 mg results.

METHODS

This prespecified pooled analysis of three randomised, double-blind, placebo-controlled, 12-week studies, evaluated efficacy and safety of once-daily mirabegron 25 mg (safety analysis), 50 or 100 mg (efficacy and safety analyses) and tolterodine ER 4 mg (safety analysis) for the treatment of symptoms of overactive bladder (OAB). Co-primary efficacy measures were change from baseline to Final Visit in the mean number of incontinence episodes/24 h and mean number of micturitions/24 h. Key secondary efficacy end-points included mean number of urgency episodes/24 h and mean volume voided/micturitions, while other end-points included patient-reported outcomes according to the Treatment Satisfaction-Visual Analogue Scale (TS-VAS) and responder analyses [dry rate (posttreatment), ≥ 50% reduction in incontinence episodes/24 h, ≤ 8 micturitions/24 h (post hoc analysis)]. The safety analysis included adverse event (AE) reporting, laboratory assessments, ECG, postvoid residual volume and vital signs (blood pressure, pulse rate).

RESULTS

Mirabegron (50 and 100 mg once daily) demonstrated statistically significant improvements compared with placebo for the co-primary end-points, key secondary efficacy variables, TS-VAS and responder analyses (all comparisons p < 0.05). Mirabegron is well tolerated and demonstrates a good safety profile. The most common AEs (≥ 3%) included hypertension, nasopharyngitis and urinary tract infection (UTI); the incidence of hypertensive events and UTIs decreased with increasing dose. For mirabegron, the incidence of the bothersome antimuscarinic AE, dry mouth, was at placebo level and of a lesser magnitude than tolterodine.

CONCLUSION

The efficacy and safety of mirabegron are demonstrated in this large pooled clinical trial dataset in patients with OAB.