Background: Atezolizumab is a standard of care in selected cisplatin-ineligible pts with advanced UC. VEGF targeted therapies have activity in advanced UC and may lead to immune synergy when combined with anti-PD-1/L1 therapy. This phase II study is investigating the combination of bevacizumab and atezolizumab in untreated cisplatin-ineligible pts with advanced UC. Methods: HCRN GU15-215 (NCT03272217) is a phase 2, multicenter single arm trial to evaluate the efficacy and safety of atezolizumab and bevacizumab in pts with advanced UC. Cisplatin-ineligible pts (defined as any of estimated CrCl < 60 cc/min, Grade ≥ 2 hearing loss or neuropathy, ECOG PS 2 or solitary kidney) with untreated, histologically confirmed locally advanced or metastatic UC irrespective of PD-L1 expression status and with sufficient pre-treatment tumor tissue available for biomarker analysis are eligible. Pts who have received perioperative chemotherapy are eligible, however prior treatment with a checkpoint inhibitor is excluded. Pts with NYHA Class II or greater heart failure, significant cerebrovascular or cardiac disease within 3 months, uncontrolled HTN, persistent gross hematuria, and GI obstruction or perforation within 6 months are excluded. 70 pts will receive treatment with atezolizumab 1200 mg IV plus bevacizumab 15 mg/kg IV every 21 days. All pts will undergo an on-treatment biopsy before cycle 2 if safe and feasible. Peripheral blood samples and stool samples will be collected before treatment and on-treatment for immune-relevant biomarker analyses. Cross-sectional imaging will be performed every 9 weeks on therapy for the first 12 months and then every 12 weeks thereafter to assess for response. Subjects will be eligible to continue treatment until RECIST v1.1 defined progression or unacceptable toxicity for up to 24 months. The primary endpoint is overall survival rate at 1 year and will be analyzed by the Kaplan Meier method. Key secondary endpoints include objective response rate, duration of response, disease control rate, progression-free survival and safety and toxicity as defined by CTCAE version 4.0. Clinical trial information: NCT03272217.