Study With Atezolizumab in Combination With Trastuzumab and Vinorelbine in HER2-positive Advanced/Metastatic Breast Cancer

Inclusion Criteria: * Male or female (Premenopausal or postmenopausal women) * ECOG 0 to 2 * Histologically confirmed adenocarcinoma of the breast, metastatic or unresectable locally advanced. * All patients must have received at least trastuzumab and other anti-HER2 ADCs (including but not limited to T-DM1). * Measurable disease according to RECIST 1.1 criteria. * Adequate organ function * Baseline LVEF ≥50% * Participants with asymptomatic brain metastases are eligible. Exclusion Criteria: * Treatment with any investigational anticancer drug within 14 days of the start of study treatment. * Patient has received Vinorelbine or any other vinca alkaloids previously immediately prior to initiate study treatment. * History of other malignant tumors in the past 3 years * Known or suspected leptomeningeal disease (LMD)/ poorly controlled (\> 1/week) generalized or complex partial seizures, or manifest neurologic progression due to brain metastases. * Symptomatic hypercalcemia requiring treatment with bisphosphonates in the 14 days prior to inclusion * Cardiopulmonary dysfunction * Any other severe, uncontrolled * Major surgery in the 28 days prior to enrolment * Infection with HIV or active Hepatitis B and/or Hepatitis C. * History of trastuzumab intolerance, including grade 3-4 infusion reaction or hypersensitivity. * Known hypersensitivity or allergy to biopharmaceuticals produced in Chinese hamster ovary cells or any component of the atezolizumab formulation * History of autoimmune disease, * Prior allogeneic stem cell or solid organ transplantation * History of idiopathic pulmonary fibrosis, drug-induced pneumonitis, organizing pneumonia (i.e., bronchiolitis obliterans, cryptogenic organizing pneumonia), or evidence of active pneumonitis on screening chest CT scan. (Note: History of radiation pneumonitis in the radiation field \[fibrosis\] is permitted.) * Active tuberculosis * Receipt of a live, attenuated vaccine within 4 weeks prior to enrollment * Prior treatment with CD137 agonists, anti-PD-1, or anti-PD-L1 therapeutic antibody or immune checkpoint targeting agents * Treatment with systemic immunostimulatory agents (including but not limited to interferons or interleukin \[IL\]-2) within 4 weeks or five half-lives of the drug prior to enrolment * Treatment with systemic immunosuppressive medications within 2 weeks prior to enrolment, or anticipated requirement for systemic immunosuppressive medications during the trial.