An Extension Study to Examine the Safety and Tolerability of a New Drug in Patients With Symptoms of Overactive Bladder (OAB).

Inclusion Criteria: 1. Has completed participation in study RVT-901-3003. 2. Has demonstrated ≥ 80% compliance with self-administration of Study Treatment in study RVT-901-3003. Exclusion Criteria: 1. Has a change in history or current evidence of any clinically significant condition, therapy, lab abnormality, or other circumstance that might, in the opinion of the Investigator, confound the results of the study, interfere with the participant's ability to comply with study procedures, or make participation in the study not in the participant's best interest. 2. Has coronary or neurovascular interventions planned during the duration of the study. 3. Has uncontrolled hyperglycemia (defined as fasting blood glucose \>150 mg/dL or 8.33 mmol/L and/or non-fasting blood glucose \>200 mg/dL or 11.1 mmol/L) based on most recent available lab results in study RVT-901-3003 or, if in the opinion of the Investigator, is uncontrolled. 4. Has uncontrolled hypertension (systolic blood pressure of ≥ 180 mm Hg and/or diastolic blood pressure of ≥ 100 mm Hg) or has a resting heart rate (by pulse) \> 100 beats per minute. 5. Has clinically significant ECG abnormality which, in the opinion of the Investigator, exposes the participant to risk by participating in the study 6. Has alanine aminotransferase or aspartate aminotransferase \> 2.0 times the upper limit of normal (ULN), or bilirubin (total bilirubin) \> 1.5 x ULN (or \> 2.0 x ULN if secondary to Gilbert syndrome or pattern consistent with Gilbert syndrome) based on most recent available lab results in study RVT-901-3003. 7. Has an estimated glomerular filtration rate (eGFR) \< 30mL/min/1.73 m2 based on most recent available lab results in study RVT-901-3003. 8. Use of any prohibited medications as detailed in Section 7.7.3. 9. Plans to initiate or change the dosing of any medications listed in Section 7.7.5 during the study that in the opinion of the investigator is assessed to be clinical significant. 10. Has an allergy, intolerance, or a history of a significant clinical or laboratory adverse experience associated with any of the active or inactive components of the vibegron formulation or tolterodine formulation. 11. Is currently participating or has participated in a study with an investigational compound or device within 28 days of signing informed consent, not including participation in study RVT-901-3003. 12. Has a history of significant drug or alcohol abuse/dependence within a year of informed consent, as assessed by the investigator. 13. Has a varying sleep schedule anticipated during times when the voiding diaries are to be completed.