ATALANTE: Atezolizumab vs Placebo Phase III Study in Late Relapse Ovarian Cancer Treated With Chemotherapy+Bevacizumab

Approximately 600 patients will be randomized using an Interactive Voice Response System /Interactive web system (IVR/IWR system) in a 1:2 ratio to the treatments as specified below: A. Arm A: Placebo + bevacizumab \& platinum-based chemotherapy. The placebo arm will include one of 3 following regimens up to investigator choice (chosen prior to randomization) 1. Carboplatin (day1)combined with gemcitabine (day1 \& day8) and bevacizumab (day1) + placebo ( day1) x 6 cycles q3weeks followed by maintenance with bevacizumab ( day1) + placebo (day1) q3weeks until disease progression or 2. Carboplatin (d1) combined with paclitaxel (day1) and bevacizumab (day1) + placebo (d1) x 6 cycles every 3weeks followed by maintenance with bevacizumab (day1) + placebo (day1) q3weeks until disease progression or 3. Carboplatin (day1) combined with pegylated liposomal doxorubicin (PLD) (day1) and bevacizumab (day1 \& 15) + placebo ( day1\& 15) x 6 cycles every 4weeks followed by maintenance with bevacizumab (day1) + placebo (day1) q3weeks until disease progression. B. Arm B: Atezolizumab + bevacizumab \& platinum-based chemotherapy The atezolizumab arm will include one of 3 following regimens up to investigator choice (chosen prior to randomization) 1. Carboplatin (day1) combined with gemcitabine (day1 \& d8) and bevacizumab (day1) + atezolizumab ( day1) x 6 cycles q3weeks followed by maintenance with bevacizumab (day1) + atezolizumab (day1) q3w until disease progression or 2. Carboplatin (day1) combined with paclitaxel (day1) and bevacizumab ( day1) + atezolizumab (1200mg, d1) x 6 cycles every 3wk (day1) q3weeks until disease progression or 3. Carboplatin (day1) combined with pegylated liposomal doxorubicin (PLD) (day1) and bevacizumab (day1 \& 15) + atezolizumab (day1\& 15) x 6 cycles every 4weeks followed by maintenance with bevacizumab (day1) + atezolizumab ( day1) q3weeks until disease progression. Before randomization to the study: * A tumor biopsy should have been obtained and sent to the central laboratory * PD-L1 status should be determined