A Study of the Safety, Efficacy, and Pharmacokinetics of Tiragolumab in Combination With Atezolizumab and Chemotherapy in Participants With Triple-Negative Breast Cancer
A Study of the Safety, Efficacy, and Pharmacokinetics of Tiragolumab in Combination With Atezolizumab and Chemotherapy in Participants With Triple-Negative Breast Cancer
The purpose of this study is to evaluate the safety, efficacy, and pharmacokinetics of
 tiragolumab in combination with atezolizumab and chemotherapy in participants with metastatic
 and early triple-negative breast cancer (TNBC).
Inclusion Criteria

 Cohort A:

 -  Metastatic or locally advanced unresectable, histologically documented TNBC
 characterized by absence of human epidermal growth factor 2 (HER2), estrogen receptor
 (ER), and progesterone receptor (PR) expression

 -  Only patients with metastatic TNBC tumors that are centrally tested and found to be
 programmed death-ligand 1 (PD-L1) positive will be enrolled

 -  No prior chemotherapy or targeted systemic therapy for inoperable locally advanced or
 metastatic TNBC

 -  Eastern Cooperative Oncology Group performance status of 0 or 1

 -  Measurable disease, as assessed by the investigator according to RECIST v1.1

 -  Adequate hematologic and end-organ function

 Cohort B:

 -  Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

 -  Histologically documented TNBC (negative HER2, ER, and PR status)

 -  Confirmed tumor PD-L1 evaluation as documented through central testing of a
 representative tumor tissue specimen

 -  Primary breast tumor size of greater than (>) 2 centimeters (cm) by at least one
 radiographic or clinical measurement

 -  Stage at presentation: cT2-cT4, cN0-cN3, cM0

 -  Baseline left ventricular ejection fraction (LVEF) greater than or equal to (>/=) 53
 percent (%) measured by echocardiogram (ECHO) or multiple-gated acquisition (MUGA)
 scans

 -  Adequate hematologic and end-organ function

 Exclusion Criteria

 Cohort A:

 -  Formalin-fixed, paraffin-embedded (FFPE) tumor tissue that is PD-L1 negative, as
 determined on the SP142 PD-L1 immunohistochemistry assay, with positivity defined as
 immune cells greater than or equal to (>/=) 1%

 -  Spinal cord compression not definitively treated with surgery and/or radiation or
 previously diagnosed and treated spinal cord compression without evidence that disease
 has been clinically stable for >2 weeks prior to initiation of study treatment

 -  Known central nervous system (CNS) disease, except for treated asymptomatic CNS
 metastases

 -  Leptomeningeal disease

 Cohort B:

 -  History of invasive breast cancer

 -  Stage IV (metastatic) breast cancer

 -  Prior systemic therapy for treatment and prevention of breast cancer

 -  Previous therapy with anthracyclines, platinum, or taxanes for any malignancy

 -  Synchronous, bilateral invasive breast cancer

 -  Cardiopulmonary dysfunction