Safety and Pharmacokinetics of Atezolizumab Combination Treatments in Participants With HER2-Positive and HER2-Negative Breast Cancer

A Phase Ib, Open-Label Study Evaluating the Safety and Pharmacokinetics of Atezolizumab (Anti-PD-L1 Antibody) in Combination With Trastuzumab Emtansine or With Trastuzumab and Pertuzumab (With and Without Docetaxel) in Patients With HER2-Positive Breast Cancer and Atezolizumab With Doxorubicin and Cyclophosphamide in HER2-Negative Breast Cancer

This is a Phase Ib, open-label, two-stage study with two active regimens in each stage designed to evaluate the safety and tolerability of combination treatment with atezolizumab, trastuzumab, and pertuzumab (with and without docetaxel) or atezolizumab and trastuzumab emtansine in participants with human epidermal growth factor receptor 2 (HER2) positive metastatic breast cancer (MBC) and locally advanced early breast cancer (EBC), and atezolizumab with doxorubicin and cyclophosphamide in HER2-negative breast cancer.

Inclusion Criteria:

• Histologically documented HER2-positive and HER2-negative (cohort E only) breast cancer
• Metastatic breast cancer that is measurable (Stage 1) or early breast cancer with a primary tumor size greater than (>) 2 centimeter (cm) (Stage 2)
• Eastern cooperative oncology group (ECOG) performed status of 0, 1 or 2; 0 or 1 (cohort E only)
• Life expectancy of 12 or more weeks
• Adequate hematologic and end-organ function
• Left ventricular ejection fraction greater than or equal to (>=) 50 percentage (%); >=55% (cohort E only)

Exclusion Criteria:

• Known central nervous system (CNS) disease, except for treated asymptomatic CNS metastases
• Leptomeningeal disease
• Pregnancy or lactation
• History of autoimmune disease
• Prior allogeneic stem cell or solid organ transplantation
• Positive test for human immunodeficiency virus (HIV)
• Active hepatitis B or hepatitis C