Study to Evaluate the Efficacy, Safety, and Tolerability of Mirabegron in Older Adult Subjects With Overactive Bladder (OAB)

Inclusion Criteria assessed at Visit 1 (Screening):

• Subject is willing and able to complete the micturition diary and questionnaires correctly.
• Subject has symptoms of wet overactive bladder (OAB) (urinary frequency and urgency with incontinence) for greater than or equal to 3 months prior to Screening.
• Subject agrees not to participate in another interventional study from the time of screening until the final study visit.

Inclusion Criteria assessed after placebo run-in period at Visit 3 (Baseline):

• Subject continues to meet all inclusion criteria of Visit 1.
• Subjects must experience at least one incontinence episode in the placebo run-in period based on the 3-day micturition diary.
• Subject must experience at least 3 episodes of urgency (grade 3 or 4) based on the 3-day micturition diary.
• Subject must experience an average of greater than or equal to 8 micturitions/day based on the 3-day micturition diary.

Exclusion Criteria assessed at Visit 1 (Screening):

• Subject has ongoing symptoms suggestive of bladder outlet obstruction (BOO) or history of BOO that is currently not well controlled.
• Subject has Post-Void Residual Volume (PVR) greater than 150 mL.
• Subject has neurogenic bladder or neurological dysfunction or injury which could affect the lower urinary tract or nerve supply.
• Subject has significant stress incontinence or mixed stress/urgency incontinence where stress is the predominant factor as determined by the Investigator (for female subjects confirmed by a cough provocation test). Subjects with a history of stress incontinence that is currently treated (e.g. remote history of surgery for stress incontinence) may be included as long as they pass cough provocation test.
• Subject has an indwelling catheter or practices intermittent self-catheterization.
• Subject has evidence of Urinary Tract Infection (UTI). Urine culture and sensitivity will be performed for positive leukocytes, or nitrites, or turbidity, or at the investigator's discretion and will be confirmed with a culture greater than 100,000 cfu/mL. If a subject has a UTI at Screening (Visit 1), the subject can be rescreened after successful treatment of the UTI (confirmed by a laboratory result of negative urine culture).
• Subject has a chronic inflammatory condition such as interstitial cystitis, bladder stones, previous pelvic radiation therapy, or previous or current malignant disease of the pelvic organs (i.e., within the confines of the pelvis including the bladder and rectum in both sexes and the uterus, ovaries, and fallopian tubes in females; organs of the lower gastrointestinal tract are not necessarily considered pelvic organs as the distal ascending colon, the full transverse colon and proximal portion of the descending colon are in the abdomen).
• Subject resides in a nursing home.
• Subject is likely to enter a hospital or nursing home due to medical instability within the next 6 months in the opinion of the Investigator.
• Subject has received intravesical injection in the past 12 months with botulinum toxin, resiniferatoxin, or capsaicin.
• Subject has received electro-stimulation therapy for OAB (e.g. sacral nerve stimulation or Percutaneous Tibial Nerve Stimulation [PTNS]).
• Subject began or has changed a bladder training program or pelvic floor exercises less than 30 days prior to Screening.
• Subject has moderate or severe hepatic impairment defined as Child-Pugh Class B or C.
• Subject has severe renal impairment defined as estimated creatinine clearance less than 29 mL/min determined by Estimated Glomerular Filtration Rate (eGFR, Cockroft-Gault, or MDRD formulae). A subject with end stage renal disease or undergoing dialysis is also not a candidate for the study.
• Subject has severe uncontrolled hypertension, which is defined as a sitting systolic blood pressure greater than or equal to 180 mmHg and/or diastolic blood pressure greater than or equal to 110 mmHg.
• Subject has evidence of QT prolongation on elect