Efficacy and Safety of Mirabegron versus Placebo Add-On Therapy in Men with Overactive Bladder Symptoms Receiving Tamsulosin for Underlying Benign Prostatic Hyperplasia: A Randomized, Phase 4 Study (PLUS)

Purpose: PLUS investigated the efficacy and safety of mirabegron add-on therapy in men with overactive bladder symptoms receiving tamsulosin for underlying lower urinary tract symptoms attributable to benign prostatic hyperplasia.

Materials and methods: In this phase 4 study a 4-week 0.4 mg tamsulosin run-in period was followed by a 12-week, randomized, double-blind, treatment period in which patients initially received 25 mg mirabegron or placebo add-on therapy. At 4 weeks doses were titrated to 50 mg mirabegron or placebo equivalent. Efficacy end points were changes from baseline to end of treatment in mean number of micturitions per day (primary), mean volume voided per micturition, number of urgency episodes per day, total urgency and frequency score, and total International Prostate Symptom Score (secondary). Safety assessments included treatment emergent adverse events, and post-void residual volume, and maximum urinary flow measurements.

Results: Of the 676 men most were 65 years old or older (380, 56.2%). Tamsulosin plus mirabegron was statistically superior to tamsulosin plus placebo in reducing the mean number of micturitions per day (-2.00 vs -1.62; adjusted difference -0.39; 95% CI -0.76, -0.02). Statistically superior results were noted for tamsulosin plus mirabegron in mean volume voided per micturition, urgency episodes per day, and total urgency and frequency score (not International Prostate Symptom Score). Higher overall treatment emergent adverse event rates were observed with tamsulosin plus placebo, although higher rates of drug related treatment emergent adverse events were noted with tamsulosin plus mirabegron. Urinary retention rates were higher in the tamsulosin plus mirabegron group. Post-void residual volume and maximum urinary flow results were not clinically meaningful.

Conclusions: The results of PLUS underscore the utility of mirabegron add-on therapy to treat men with overactive bladder symptoms receiving tamsulosin for benign prostatic hyperplasia.