BCG in Combination With Durvalumab in Adult BCG-naïve, High-risk NMIBC Participants

Inclusion Criteria: * BCG-naïve (defined as participants not having received prior intravesical BCG or who previously received but stopped BCG more than 3 years before study entry). * Local histological confirmation (based on cytology and/or pathology report) of high-risk transitional cell carcinoma of the urothelium of the urinary bladder confined to the mucosa or submucosa. * Complete resection of all Ta/T1 papillary disease prior to enrollment, with the transurethral resection of bladder tumor (TURBT) removing high-risk NMIBC (non-muscle invasive bladder cancer) performed not more than 4 months before enrollment in the study. * No prior radiotherapy for bladder cancer. * A life expectancy of at least 12 weeks (90 days). * Adequate organ and marrow function * World Health Organization/Eastern Cooperative Oncology Group performance status of 0 or 1 at screening * No prior exposure to immune-mediated therapy of cancer * A candidate for BCG treatment. * Local histological confirmation (based on cytology and/or pathology report) of high-risk transitional cell carcinoma of the urothelium of the urinary bladder confined to the mucosa or submucosa. A high-risk tumor is defined as one of the following: T1 tumor; High-grade/G3 tumor; CIS. Exclusion Criteria: * Evidence of muscle-invasive, locally advanced, metastatic, and/or extra-vesical bladder cancer (ie, T2, T3, T4, and / or Stage IV). * Predominantly variant histology such as micropapillary, plasmacytoid, nested, sarcomatoid…