Background: Prognosis of advanced/recurrent endometrial cancer (EC) is poor with median survival of 12-15 months for patients with measurable disease. Treatment options are limited, with primary management being chemotherapy with carboplatin and paclitaxel. EC is known to be one of the tumor types with highest mutational load. Ultra- and hyper-mutated EC, which harbor POLE and mismatch repair gene defects respectively, have shown peri-tumoral T cell infiltration and high expression of PD-1 and PD-L1 proteins, suggesting that immune regulation may enhance specific T cell responses and result in improved anti-tumour immunity. Preliminary data in EC patients have shown tumour control activity of the PD-L1 targeting agent atezolizumab. Methods: 550 patients with newly diagnosed, advanced stage III/IV or recurrent EC will be accrued during a period of 24 months with a 1:2 randomization ratio into two arms: i. control group receiving standard chemotherapy plus placebo IV every 21 days up to 6/8 cycles followed by placebo until progression; ii. experimental group receiving standard chemotherapy plus 1200 mg atezolizumab IV every 21 days up to 6/8 cycles followed by atezolizumab until progression. Standard chemotherapy will consist of 175 mg/m² paclitaxel plus AUC5/6 carboplatin. Stratification factors are: histology, disease stage, microsatellite status, country of experimental site. The study is planned to demonstrate a survival increase and is equally powered for PFS. Secondary endpoints include ORR, duration of response, PFS2, quality of life, adverse events and compliance. The study is sponsored by MaNGO group and will involve sites from ENGOT and GCIG networks across Europe, Japan, Australia and New Zealand. Currently, the trial is open in Italy and in Switzerland where a total of 6 patients have been enrolled. Clinical trial information: NCT03603184