A Study to Evaluate the Safety and Efficacy of Ipatasertib in Combination With Atezolizumab and Paclitaxel or Nab-Paclitaxel in Participants With Locally Advanced or Metastatic Triple-Negative Breast Cancer

Inclusion Criteria:

General:

* Eastern Cooperative Oncology Group Performance Status of 0 or 1.
* Adequate hematologic and organ function.
* For Cohorts 1, 2 and 4: Life expectancy of at least 6 months.
* For men and women of child bearing potential: agreement to remain abstinent or use protocol defined contraceptive measures during the treatment period and for at least 28 days after the last dose of ipatasertib, 6 months after the last dose of paclitaxel, nab-paclitaxel, or doxorubicin, and 12 months after the last dose of cyclophosphamide, and 5 months after the last dose of atezolizumab, whichever occurs later along with refraining from donating sperm or eggs during this same period.

Disease-specific:

* For Cohorts 1, 2 and 4: histologically documented TNBC that is locally advanced or metastatic and is not amenable to resection with curative intent.
* For Cohort 2: disease progression following one or two lines of systemic therapy for inoperable locally advanced or metastatic TNBC.
* For Cohorts 1, 2 and 4: measurable disease according to RECIST v1.1 criteria.
* For Cohort 2: Treated brain or spinal cord metastases are allowed if participants have stable disease and are not on steroid treatment.
* For Cohort 3: histologically documented TNBC with a primary breast tumour size of \> 2 cm by at least one radiographic or clinical measurement and disease stage at presentation of cT2-4 cN0-3 cM0.
* For Cohort 3: participant agreement to undergo appropriate surgical management, including axillary lymph node surgery and partial or total mastectomy, after completion of neoadjuvant treatment.
* For Cohort 4: participants must have centrally confirmed PD-L1-positive tumour.

Exclusion Criteria:

General:

* History of malabsorption syndrome or other condition that would interfere with enteral absorption or results in the inability or unwillingness to swallow pills.
* Active infection requiring antibiotics.
* History of or current evidence of HIV infection.
* Known clinically significant history of liver disease.
* Major surgical procedure, open biopsy, or significant traumatic injury within 28 days prior to Day 1 of Cycle 1 or anticipation of need for a major surgical procedure (other than anticipated breast surgery for Cohort 3) during the course of the study.
* Pregnant or breastfeeding.
* New York Heart Association (NYHA) Class II, III, or IV heart failure; left ventricular ejection fraction \< 50%; or active ventricular arrhythmia requiring medication.
* Treatment with approved or investigational cancer therapy within 14 days prior to Day 1 of Cycle 1.
* Prior treatment with an Akt inhibitor.

Disease-specific:

* For Cohorts 1 and 4: history of or known presence of brain or spinal cord metastases.
* For Cohorts 1 and 4: participants who have received previous systemic therapy for inoperable locally advanced or metastatic TNBC, including chemotherapy, immune checkpoint inhibitors, or targeted agents.
* Unresolved, clinically significant toxicity from prior therapy, except for alopecia and Grade 1 peripheral neuropathy.
* Participants who have received palliative radiation treatment to peripheral sites (e.g., bone metastases) for pain control and whose last treatment was completed 14 days prior to Day 1 of Cycle 1 and have recovered from all acute, reversible effects.
* Uncontrolled pleural effusion, pericardial effusion, or ascites.
* Uncontrolled tumor related complications.
* Uncontrolled hypercalcaemia or symptomatic hypercalcaemia requiring continued use of bisphosphonate therapy.
* Malignancies other than breast cancer within 5 years prior to Day 1 of Cycle 1.
* For Cohort 3, participants with the following are excluded: \[1\] prior history of invasive breast cancer; \[2\] prior systemic therapy for treatment and/or prevention of invasive breast cancer; \[3\] previous therapy with anthracyclines or taxanes for any malignancy; \[4\] bilateral breast cancer; \[5\] undergone incisional and/or excisional biopsy of primary tumor and/or axillary lymph nodes; \[6\] undergone axillary lymph node dissection (ALND) prior to initiation of neoadjuvant therapy; \[6\] history of other malignancy within 5 years prior to screening; \[7\] history of cerebrovascular accident within 12 months prior to initiation of study treatment; \[8\] cardiopulmonary dysfunction; \[9\] known allergy or hypersensitivity to the components of cyclophosphamide/doxorubicin formulations and filgrastim or pegfilgrastim formulations; \[10\] severe infection within 4 weeks prior to initiation of study treatment; \[11\] treatment with therapeutic oral or IV (Intravenous) antibiotics within 2 weeks prior to initiation of study treatment and \[12\] prior treatment with CD137 agonists or immune checkpoint - blockade therapies.

Ipatasertib-specific:

* History of Type I or Type II diabetes mellitus requiring insulin.
* Grade \>= 2 uncontrolled or untreated hypercholesterolemia or hypertriglyceridemia.
* History of or active inflammatory bowel disease or active bowel inflammation.
* Clinically significant lung disease.
* Treatment with strong CYP3A inhibitors or strong CYP3A inducers.

Atezolizumab-specific:

* Active or history of autoimmune disease or immune deficiency.
* History of idiopathic pulmonary fibrosis, organizing pneumonia (e.g., bronchiolitis obliterans), drug-induced pneumonitis, idiopathic pneumonitis, or evidence of active pneumonitis on screening chest computed tomography (CT) scan.
* Prior allogeneic stem cell or solid organ transplantation.
* Treatment with a live, attenuated vaccine within 4 weeks prior to initiation of study treatment, or anticipation of need for such a vaccine during treatment with atezolizumab or within 5 months after the last dose of atezolizumab.
* History of hypersensitivity reactions to study drug or any component of the study drug formulation.
* Treatment with systemic immunostimulatory agents and immunosuppressive medication treatment, or anticipation of need for systemic immunosuppressive medication during the course of the study.

Paclitaxel-specific:

\- Grade \>= 2 peripheral neuropathy.