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.