Atezolizumab and BCG in High Risk BCG naïve Non-muscle Invasive Bladder Cancer (NMIBC) Patients (BladderGATE)

Inclusion Criteria: 1. Patients ≥ 18 years old. 2. Signed Informed Consent Form 3. Histologically confirmed diagnosis of high risk non-muscle-invasive (T1, high grade Ta - G3- and / or carcinoma in situ) transitional cell carcinoma of the bladder 4. Never treated with BCG or stopped \>3y ago 5. World Health Organization Performance Status (WHO PS) 0-1 6. No prior radiation to bladder 7. Life expectancy ≥ 5 years 8. Adequate hematologic and end-organ function 9. The time elapsed between the TURBT and the start of the study treatment will not be less than 4 weeks or more than 12 weeks 10. Women who are not postmenopausal or surgically sterile must have a negative serum pregnancy test result within 14 days prior to the first dose of study treatment. 11. For women of childbearing potential: agreement to remain abstinent or use contraceptive methods that result in a failure rate of \< 1% per year during the treatment period and for at least 150 days after the last dose of study drug. 12. Tumor tissue biopsy at study entry or availability of an archival specimen obtained within 2 months of study screening 13. Willingness to complete all study-related procedures including patient-reported questionnaires Exclusion Criteria: 1. Muscle-invasive, locally advanced non-resectable, or metastatic urothelial carcinoma (i.e., T2, T3, T4, and/or stage IV) 2. Previous BCG within a 3 years period 3. Life expectancy \<5 years 4. WHO PS 2, 3 or 4 5. Known additional malignancy that is progressing or requires active treatment 6. Active autoimmune disease that has required systemic treatment in the past 2 years 7. Evidence of interstitial lung disease or active non-infectious pneumonitis 8. Active infection requiring systemic therapy 9. Pregnant or breastfeeding, or expecting to conceive within the projected duration of the trial through 150 days after the last dose of study treatment. 10. Prior therapy with an anti-programmed cell death 1 (PD-1), anti-PD-ligand 2 (L2) agent, or with an agent directed to another co-inhibitory T-cell receptor 11. Known human immunodeficiency virus (HIV) 12. Known active Hepatitis B or C infection or tuberculosis 13. Received a live virus vaccine within 30 days of planned start of study treatment 14. Treatment with any approved anti-cancer therapy, including chemotherapy , radiation therapy , or hormonal therapy within 3 weeks prior to the first dose of study treatment 15. Treatment with any other investigational agent or participation in another clinical trial with therapeutic intent within 4 weeks prior to the first dose of study treatment 16. Allergy or hypersensitivity to components of the atezolizumab or BCG formulation 17. Prior allogeneic stem cell or solid organ transplantation 18. History of idiopathic pulmonary fibrosis, organizing pneumonia , drug-induced pneumonitis, idiopathic pneumonitis, or evidence of active pneumonitis on screening chest CT scan. 19. Serum albumin \< 2.5 g/dL 20. Severe infections within 4 weeks prior to the first dose of study treatment 21. Signs or symptoms of infection within 2 weeks prior to the first dose of study treatment 22. Treatment with therapeutic oral or IV antibiotics within 2 weeks prior to the first dose of study treatment 23. Significant cardiovascular disease, such as New York Heart Association cardiac disease (Class II or greater), myocardial infarction within the previous 3 months, unstable arrhythmias, or unstable angina 24. Major surgical procedure other than for diagnosis within 4 weeks prior to the first dose of study treatment, or anticipation of need for a major surgical procedure during the course of the study 25. Any other diseases, metabolic dysfunction, physical examination finding, or clinical laboratory finding giving reasonable suspicion of a disease or condition that contraindicates the use of an investigational drug or that may affect the interpretation of the results or render the patient at high risk from treatment complications 26. History of prior systemic BCG infection