Phase 2 Durvalumab (Medi4736) for Bacillus Calmette-Guérin (BCG) Refactory Urothelial Carcinoma in Situ of the Bladder

Durvalumab will be given every 4 weeks at 1500 mg/kg IV for total of 12 months/13 doses.

Cystoscopy with biopsy and transurethral resection of the bladder tumor (TURBT) (if indicated) will be performed at baseline, month 3, 6, 9, 12, 18, and 24. The month 6 and 24 cystoscopy will be done in the operating room with mapping biopsy. Rest of the cystoscopic exam with biopsy will be performed in the out-patient office setting and if clinically indicated will be repeated in the operating room. Participants will be off study if any of the biopsies document muscle invasive (T2 or above) urothelial carcinoma. Participants will also be off study if their month 6, 9, 12, 18 biopsies show persistent (month 6) or recurrent CIS or invasive (T1 or above) urothelial carcinoma. Otherwise, participants will remain on study until after the month 24 mapping biopsy.