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 unresectablelocally 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 ofstudy treatment.

• Patient has received Vinorelbine or any other vinca alkaloids previously immediatelyprior 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 tobrain metastases.

• Symptomatic hypercalcemia requiring treatment with bisphosphonates in the 14 daysprior 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 orhypersensitivity.

• Known hypersensitivity or allergy to biopharmaceuticals produced in Chinese hamsterovary 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, organizingpneumonia (i.e., bronchiolitis obliterans, cryptogenic organizing pneumonia), orevidence of active pneumonitis on screening chest CT scan. (Note: History ofradiation 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 antibodyor immune checkpoint targeting agents

• Treatment with systemic immunostimulatory agents (including but not limited tointerferons or interleukin [IL]-2) within 4 weeks or five half-lives of the drugprior to enrolment

• Treatment with systemic immunosuppressive medications within 2 weeks prior toenrolment, or anticipated requirement for systemic immunosuppressive medicationsduring the trial.