A Study of Tobemstomig/RO7247669 Combined with Nab-Paclitaxel Compared with Pembrolizumab Combined with Nab-Paclitaxel in Participants with Previously Untreated, PD-L1-Positive, Locally-Advanced Unresectable or Metastatic Triple-Negative Breast Cancer

Prior treatment

• Major surgical procedure within 4 weeks prior to initiation of study treatment

Other illness

• History of malignancy within 5 years prior to consent
• History of leptomeningeal disease

Lab values

• Prior treatment with CD137 agonists or anti-cytotoxic T-lymphocyte-associated protein (CTLA) therapeutic antibodies or an anti-lymphocyte-activation gene 3 protein (LAG-3) agent

Other

• Poor venous access
• Symptomatic, untreated, or actively progressing central nervous system (CNS) metastases

• Metastatic or locally advanced unresectable, histologically documented TNBC [absence of human epidermal growth factor receptor 2 (HER2)-over-expression, estrogen receptor (ER), and progesterone receptor (PgR) expression by local assessment]
• Measurable disease per Response Evaluation Criteria in Solid Tumors, Version 1.1 (RECIST v1.1). If metastatic disease (Stage IV), measurable disease outside of the bone
• No prior systemic therapy for metastatic or locally advanced unresectable TNBC
• Tumor programmed death-ligand 1 (PD-L1) expression as documented through central testing of a representative tumor tissue specimen
• Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1
• Adequate hematologic and end-organ function, defined by protocol-specified laboratory test results, obtained within 14 days prior to initiation of study treatment