The schedule of assessments is updated with the following changes: • Physical examination is added to visit 5 (week 4). • Height and body weight measurement is added to visit 7 (week 12). • Clinical Laboratory Tests (Hematology and Biochemistry) footnote is removed from visit 5 (week 4) • Self-blood pressure measurement (SBPM) is added visit 2 (week -2) and removed from visit 8 (week 14). • Pregnancy tests are added to visit 3 (week 0), visit 5 (week 4) and visit 7 (week 12). • Additional text is added to footnote h to explain that the SBPM should be done during the weekend preceding the study visit. • Footnote i is revised to remove visit 5 (week 4). Footnote j is revised to clarify that urine pregnancy tests will be performed for females of childbearing potential at all on-site visits. • The minimum weight of subjects is changed from 11 kg to 13 kg. This is updated in the dose rationale and Inclusion Criterion #4. • A criterion (#11) that subjects must have a pulse of > 99th percentile for age at Screening is deleted • Text is added to allow the option that the subject is currently taking medication known to prolong the QT interval. • The criterion is updated to exclude subjects who use moderate or strong cytochrome CYP3A4/5 or P-gp inhibitors or inducers.

• The following secondary endpoint is removed: “mean number of nighttime incontinence episodes per 24 hours” • The following inclusion criterion is removed: “16 Subject must have at least 1 daytime incontinence episode (on average) per day, during the 7 day period before visit 3/baseline, as recorded in the bladder e diary.” • The following exclusion criteria are removed: “1. Subject has extraordinary daytime only urinary frequency according to the ICCS definition. o This applies to a toilet-trained child who has the frequent need to void that is associated with small micturition volumes solely during the day. o The daytime voiding frequency is at least once per hour with an average voided volume of < 50% of expected bladder capacity (EBC) (typically 10% to 15%). o Incontinence is rare and nocturia is absent.” “26. Subject has extraordinary daytime only urinary frequency according to the ICCS definition based on the bladder e diary.” • The following exclusion criteria are removed: “3. Subject has monosymptomatic enuresis.” “27. Subject has monosymptomatic enuresis confirmed by the bladder e-diary.” • Exclusion criterion no. 2 is updated to: “flow indices as a predictor” of pathology other than OAB • The following text is added to exclusion criteria nos. 7 and 32: “Note: subjects with microhematuria without gross proteinuria are eligible.” • The following new exclusion criteria at ‘Visit 1/Week -4 (Screening)’ are added after exclusion criterion no. 25: “36. Subject has a current or previous history of epilepsy. 37. Subject with neuropsychiatric diagnoses (e.g., ADHD, anxiety, severe depression, autism, bipolar disorder)” • Exclusion criterion no. 30 and footnote m in Table 1 is updated to: “> 30 mL (average of 2 lowest PVR volume results) as measured by a bladder ultrasound device that gives images in 3 planes.” • Text in Sections 1.3 (Table 1, Footnote m) and 7.2.5 is updated to: “a bladder ultrasound device that gives images in 3 planes.”

• The following text is updated from: “Subject with (systolic blood pressure ≥ 160 mm Hg or diastolic blood pressure ≥ 100 mmHg.” To: “Blood pressure at or above the stage II HTN threshold (≥ 95th percentile + 12 mmHg, or ≥ 140/90 mmHg [whichever is lower]) [Flynn et al, 2017]” • The interim analysis is updated from: “blinded” To: “comparative” • The uroflow assessment is removed from the screening visit and added to visit 3 (baseline). • The following text is added: • “Subjects with previously normal or pre HTN BPs will have a timely in-clinic visit, either scheduled or unscheduled, within 2 weeks of any home SBPM measurements that are at, or above, the stage l HTN threshold to measure, document and confirm BP increases. At this timely in person visit, BP measurements intended to confirm home SBPM measurements will be taken by trained healthcare personnel. • Subjects will have an expedited in-clinic visit, either scheduled or unscheduled, within 1 week of any home SBPM measurement that are at, or above, the stage II HTN threshold, and/or a pulse rate above the 99th percentile compared to age-related pulse rate norms and ≥ 15 bpm change from baseline, to measure, document and confirm BP and/or pulse rate increases. At this expedited in clinic visit, BP measurements will be taken by trained healthcare personnel.” • The statistical methodology is updated From: In general, all data will be summarized with descriptive statistics frequency and percentage for categorical data. Data will be summarized by age group, treatment group and visit unless otherwise stated. To: In general, continuous data will be summarized descriptively including the number of subjects (n), mean, standard deviation (SD), median, minimum and maximum. Categorical data will be summarized by frequencies and percentages.

• The following bolded text is added to the age group details for the analysis of vital signs: “Descriptive statistics will be used to summarize vital sign results and changes from baseline by treatment group and within treatment group and across age group. In addition to the presentation by age groups for 5 to < 12 years of age and 12 to < 18 years of age and overall, vital signs will also be presented for age groups 5 to < 8 years of age and 8 to < 12 years of age.”