A Study of Atezolizumab With or Without Bevacizumab in Combination With Cisplatin Plus Gemcitabine in Patients With Untreated, Advanced Biliary Tract Cancer

Inclusion Criteria:

* Considered to be eligible to receive platinum-based chemotherapy, in the investigator's judgment
* Documentation of recurrent/metastatic or locally advanced unresectable disease based on computed tomography (CT) or magnetic resonance imaging (MRI) scans
* Histologically or cytologically confirmed diagnosis of iCCA, eCCA, or GBC
* No prior systemic therapy for advanced BTC
* At least one measurable untreated lesion (per RECIST v1.1)
* Adequate biliary drainage with no evidence of ongoing infection
* Eastern Cooperative Oncology Group Performance Status of 0 or 1
* Life expectancy of \> 3 months
* Adequate hematologic and end-organ function
* For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive methods, and agreement to refrain from donating eggs
* For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use a condom, and agreement to refrain from donating sperm

Exclusion Criteria:

* Recurrent disease \<=6 months after curative surgery or \<= 6 months after the completion of adjuvant therapy
* Prior local regional therapy such as radioembolization
* Combined or mixed hepatocellular/cholangiocarcinoma
* Clinically significant hepatic encephalopathy within the 12 months prior to Day 1 of Cycle 1
* National Cancer Institute Common Terminoogy Criteria for Adverse Events Grade \>= 2 peripheral neuropathy
* Prior bleeding event due to untreated or incompletely treated esophageal and/or gastric varices within 6 months prior to Day 1 of Cycle 1
* Pregnant or breastfeeding, or intending to become pregnant during the study or within 5 months after the final dose of atezolizumab or within 6 months after the final dose of bevacizumab, cisplatin or gemcitabine
* Active or history of autoimmune disease or immune deficiency
* History of idiopathic pulmonary fibrosis, organizing pneumonia, drug-induced pneumonitis, or idiopathic pneumonitis, or evidence of active pneumonitis on screening chest computed tomography scan
* History of malignancy other than BTC within 5 years prior to screening, with the exception of malignancies with a negligible risk of metastasis or death
* Symptomatic, untreated, or actively progressing CNS metastases
* For patients with lung metastases, if one of the following criteria applies: Large, centrally located pulmonary metastases; Clear tumor infiltration into the thoracic great vessels seen on imaging; Clear cavitation of pulmonary lesions seen on imaging
* Active tuberculosis
* Co-infection with HBV and HCV
* Treatment with systemic immunostimulatory agents or immunosuppressive medication
* Inadequately controlled arterial hypertension
* History of hypertensive crisis or hypertensive encephalopathy
* Significant vascular disease
* Evidence of bleeding diathesis or significant coagulopathy
* Serious, non-healing or dehiscing wound, active ulcer, or untreated bone fracture
* Chronic daily treatment with a non-steroidal anti-inflammatory drug (NSAID)
* Preexisting renal impairment, myelosuppression, or hearing impairment