Cardiovascular Safety of the β 3 -Adrenoceptor Agonist Mirabegron and the Antimuscarinic Agent Solifenacin in the SYNERGY Trial.

There have been concerns that treatment of overactive bladder with β3 -adrenoceptor agonists may potentially have detrimental cardiovascular (CV) side effects. We evaluated the CV safety of mirabegron, a β3 -adrenoceptor agonist, alone and in combination therapy with the antimuscarinic agent solifenacin. The SYNERGY trial was a multinational, multicenter, randomized, double-blind, parallel-group, placebo and active-controlled phase 3 trial. Patients were randomized to receive solifenacin 5 mg + mirabegron 50 mg (combination 5 + 50 mg), solifenacin 5 mg + mirabegron 25 mg (combination 5 + 25 mg), solifenacin 5 mg monotherapy, mirabegron 25 mg monotherapy, mirabegron 50 mg monotherapy, or placebo for a 12-week double-blind treatment period. A total of 3398 patients were included in the study. Mean changes from baseline to the end of therapy in ECG parameters were similar across treatment groups, although there was an increase in heart rate of 1 beat/minute in the mirabegron treatment groups. There were no clinically meaningful differences in change from baseline in QTcF between monotherapies and placebo and between monotherapies and combination therapy. There were very few major CV events: 1 of 853 (0.1%) with a nonfatal myocardial infarction in the combination 5 + 25 mg group, 2 of 848 (0.2%) with a nonfatal stroke in the combination 5 + 50 mg group, and no events in the other groups. This CV safety analysis of the combination of mirabegron and solifenacin showed rates of CV events comparable with those for monotherapy treatments based on assessments of vital signs, electrocardiograms, and adjudicated CV events.