A Study Evaluating the Efficacy and Safety of Multiple Treatment Combinations in Patients With Metastatic or Locally Advanced Breast Cancer

Inclusion Criteria

Patients must meet all of the following criteria to qualify for Stage 1 (all cohorts) and
to qualify for Stage 2 (2L CIT-naïve cohort):

   - Age >/= 18 years at the time of signing Informed Consent Form

   - ECOG Performance Status of 0 or 1

   - Able to comply with the study protocol, in the investigator's judgment

   - Metastatic or inoperable locally advanced breast cancer

   - Measurable disease (at least one target lesion) according to RECIST v1.1

   - Life expectancy >/= 3 months, as determined by the investigator

   - Tumor accessible for biopsy, unless archival tissue is available

   - Availability of a representative tumor specimen that is suitable for biomarker
   analysis via central testing

   - Adequate hematologic and end-organ function, defined by the following laboratory test
   results, obtained within 14 days prior to initiation of study treatment

   - For women of childbearing potential: agreement to remain abstinent (refrain from
   heterosexual intercourse) or use contraceptive measures and agreement to refrain from
   breastfeeding and donating eggs, as outlined for each specific treatment arm

   - For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use
   contraceptive measures, and agreement to refrain from donating sperm, as outlined for
   each specific treatment arm

Inclusion criteria for Cohort 1

   - Metastatic or inoperable locally advanced, histologically documented TNBC

   - No prior systemic treatment for metastatic or inoperable locally advanced TNBC

   - Positive PD-L1 expression, defined as >/= 1% of the tumor area occupied by PD
   L1-expressing tumor-infiltrating immune cells of any intensity, as determined through
   use of the U.S. Food and Drug Administration-approved or CE-marked Ventana PD-L1
   (SP142) Assay

Inclusion criteria for Cohort 2

   - Metastatic or inoperable locally advanced, histologically documented TNBC

   - Eligible for capecitabine monotherapy

   - Radiologic/objective evidence of recurrence or disease progression after 1L treatment
   with chemotherapy, for a total of one line of therapy for inoperable locally advanced
   or metastatic breast cancer

Inclusion criteria for Cohort 3

   - Metastatic or inoperable locally-advanced, histologically documented HR+ breast cancer
   who had previous lines of treatment for metastatic disease.

   - Fasting glucose < 126 mg/dL or < 7.0 mmol/L and HbA1c
   - Confirmation of PIK3CA mutation

   - Patients for whom ET (e.g., fulvestrant) is recommended and treatment with cytotoxic
   chemotherapy is not indicated at time of entry into the study, as per national or
   local treatments standards

   - Postmenopausal, or premenopausal/perimenopausal status and willing to undergo and
   maintain treatment with approved LHRH-agonist (also known as gonadotropin-releasing
   hormone-agonist) therapy for the duration of study

Inclusion criteria for Cohort 4

   - Left ventricular ejection fraction, measured by echocardiogram or radionucleotide
   ventriculography, greater than 50%

   - Confirmation of HER2+ or HER2-low status Fasting glucose < 126 mg/dL or < 7.0 mmol/L
   and HbA1c
   - Confirmation of PIK3CA mutation

Exclusion Criteria for Stage 1

   - Prior treatment with T-cell co-stimulating or immune checkpoint blockade therapies,
   including anti-CTLA-4, anti-PD-1, and anti-PD-L1 therapeutic antibodies, CD40 agonists
   or interleukin-2 (IL-2) or IL-2-like compounds

   - Treatment with investigational therapy within 28 days prior to initiation of study
   treatment

   - Biologic treatment (e.g., bevacizumab) within 2 weeks prior to initiation of study
   treatment, or other systemic treatment for TNBC within 2 weeks or 5 half-lives of the
   drug (whichever is longer) prior to initiation of study treatment

   - Adverse events from prior anti-cancer therapy that have not resolved to Grade    better with the exception of alopecia of any grade and Grade    neuropathy

   - Eligibility only for the control arm

Exclusion Criteria for Stage 1 (both cohorts) and Stage 2 (2L CIT-naïve cohort)

   - Uncontrolled pleural effusion, pericardial effusion, or ascites requiring recurrent
   drainage procedures (once monthly or more frequently)

   - Uncontrolled tumor-related pain

   - Symptomatic, untreated, or actively progressing central nervous system (CNS)
   metastases

   - History of leptomeningeal disease

   - Active or history of autoimmune disease or immune deficiency

   - History of idiopathic pulmonary fibrosis, organizing pneumonia (e.g., bronchiolitis
   obliterans), drug-induced pneumonitis, or idiopathic pneumonitis, or evidence of
   active pneumonitis on screening chest computed tomography (CT) scan. History of
   radiation pneumonitis in the radiation field (fibrosis) is permitted.

   - Active tuberculosis

   - Severe infection within 4 weeks prior to initiation of study treatment

   - Treatment with therapeutic oral or IV antibiotics within 2 weeks prior to initiation
   of study treatment

   - Significant cardiovascular disease

   - Prior allogeneic stem cell or solid organ transplantation

   - History of malignancy other than breast cancer within 2 years prior to screening, with
   the exception of those with a negligible risk of metastasis or death

   - Treatment with systemic immunosuppressive medication (including, but not limited to,
   corticosteroids, cyclophosphamide, azathioprine, methotrexate, thalidomide, and
   anti-tumor necrosis factor alpha agents) within 2 weeks prior to initiation of study
   treatment, or anticipation of need for systemic immunosuppressive medication during
   the course of the study

   - Pregnancy or breastfeeding, or intention of becoming pregnant during the study

Exclusion Criteria for the 2L CIT-naive cohort, Stage 1

   - Prior treatment with capecitabine,

   - Treatment with sorivudine or its chemically related analogues, such as brivudine

   - History of severe and unexpected reactions to fluoropyrimidine therapy

   - Known complete absence of dihydropyrimidine dehydrogenase activity

Exclusion Criteria for Stage 2

   - Inability to tolerate atezolizumab during Stage 1

   - For patients receiving eribulin: congenital long QT syndrome

Additional drug-specific exclusion criteria may apply to Stage 1 and 2.