Mirabegron (YM-178), currently in development by Astellas Pharma Inc, is an 
orally active β₃-adrenoceptor (AR) agonist for the potential symptomatic 
treatment of overactive bladder (OAB). Mirabegron demonstrates nanomolar EC50 
values against the human β₃-AR in biochemical assays with potent selectivity 
over the β₁- and β₂-ARs. Originally developed as a treatment for diabetes, the 
development of mirabegron was later refocused to OAB. Cystometric experiments in 
rats reported a reduction in resting intravesical pressure and contraction 
frequency in anesthetized rats, without any effect on the amplitude of 
micturition contraction. Mirabegron also reduced non-micturition bladder 
contractions in an awake rat model of bladder outlet obstruction. Top-line 
results from clinical trials to date indicate that mirabegron has been well 
tolerated with significant efficacy in reducing the number of incontinence 
episodes and mean micturition frequency in patients. Evidence of cytochrome P450 
(CYP)2D6 inhibition in clinical trials highlighted a concern for pharmacokinetic 
interaction with other drugs that are CYP2D6 substrates, as confirmed by a rise 
in the pharmacokinetic parameters of desipramine with concomitant administration 
of mirabegron. Mirabegron exhibits a novel mode of action in targeting the β₃-AR 
for bladder relaxation, and the studies and trials conducted to date suggest 
mirabegron as a promising new treatment in the management of OAB symptoms, such 
as increased urinary urgency and frequency, and urgency incontinence.