A trial comparing combination treatment (solifenacin plus mirabegron) with one treatment alone (solifenacin)

1. Subject has symptoms of OAB (urinary frequency and urgency with urgency incontinence) for >= 3 months prior to the screening visit

2. Subject is willing and able to complete the micturition diary and questionnaires correctly, including collection and measurement of urine output for 3 days prior to each visit;

3. Subject has symptoms of "wet" OAB (urinary frequency and urgency with incontinence or mixed incontinence with predominant urgency

incontinence), and reports an average of at least 2 incontinence

episodes per day.

1. Subject experiences on average at least 1 episode of urgency (grade 3 or 4) with or without incontinence per 24-hour period during the 3-day micturition diary period.

2. Subject experiences on average at least 2 incontinence episodes per 24-hour period during the 3-day micturition diary period.

3. Subject experiences on average at least 8 micturitions (excluding incontinence episodes) per 24-hour period during the 3-day micturition diary period.

1. Subject experiences at least 1 incontinence episode during the 3-day micturition diary period and wishes to increase their treatment for OAB symptoms.

1. Subject in the opinion of the investigator has clinically significant Bladder Outlet Obstruction (BOO).

2. Subject has significant Post-void residual (PVR) volume (PVR > 150 ml).

3. Subject has significant stress incontinence or mixed stress/urgency incontinence where stress is the predominant factor as determined by the investigator

4. Subject has an indwelling catheter or practices intermittent self catheterization.

5. Subject has evidence of a UTI.

6. Subject has chronic inflammation such as interstitial cystitis, bladder stones, previous pelvic radiation therapy, or previous or current malignant disease of the pelvic organs

7. Subject has moderate to severe hepatic impairment

8. Subject has severe renal impairment or End Stage Renal disease

9. Subject has a clinically significant abnormal Electrocardiogram (ECG)

10. Subject has a concurrent malignancy or history of cancer (except noninvasive skin cancer) within the last 5 years prior to screening.

11. Subject has a QTcF interval > 450 ms for males or > 470 ms for

females or is at risk of QT prolongation (e.g., family history of long QT syndrome, hypokalaemia).

12. Subject has received intravesical treatment in the past 12 months with e.g., botulinum toxin, resiniferatoxin, capsaicin.

13. Subject has severe uncontrolled hypertension, which is defined as a sitting average systolic blood pressure ≥ 180 mmHg and/or average diastolic blood pressure ≥ 110 mmHg.

1. Subject has achieved 100% continence from Visit 2 to Visit 3

(no incontinence episodes are recorded in the 3 day diary administered for 3 days prior to Visit 3).

2. Subject does not desire an increase in study medication.

3. Subject has an average total daily urine volume > 3000ml as

recorded in the micturition diary.

4. Subject has severe uncontrolled hypertension, which is defined as a sitting average systolic blood pressure ≥ 180 mmHg and/or average diastolic blood pressure ≥ 110 mmHg.

5. Subject has a clinically significant abnormal ECG