A Study of Multiple Immune and Disease Treatment Combinations in Participants With ER+HER2- Breast Cancer That Has Spread

Inclusion Criteria

• Histological and cytological confirmation of adenocarcinoma of the breast
• Documented HER2 negative and estrogen receptor (ER) positive status of primary or metastatic tumor tissue using the most recently assessed tumor specimen, according to the local laboratory parameters
• ER negativity is defined as < 1% of tumor cells expressing hormonal receptors via IHC analysis
• At least one measurable lesion, as per Response Evaluation Criteria in Solid Tumors version 1.1 [RECIST v1.1] that can be accurately assessed at baseline and is suitable for repeated assessment by computed tomography (CT) or magnetic resonance imaging (MRI)
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
• Women and Men must agree to follow specific methods of contraception, if applicable, while participating in the trial

Exclusion Criteria

• Allergy or hypersensitivity to any study drugs or their excipients
• Any other sound medical, psychiatric and/or social reason as determined by the investigator
• Active, known, or suspected autoimmune disease or immune-related diseases
• History of unstable or deteriorating cardiac disease within the previous 12 months prior to screening
• Prior therapy with anti-programmed death 1 (PD-1), anti-programmed death-ligand 1 (PD-L1) or anti-Cytotoxic T Lymphocyte Antigen 4 (CTLA-4) class antibody
• Any major surgery within 4 weeks of the first dose of study treatment Other protocol-defined inclusion/exclusion criteria apply