A Study of Ipatasertib in Combination With Atezolizumab and Paclitaxel as a Treatment for Participants With Locally Advanced or Metastatic Triple-Negative Breast Cancer

Inclusion Criteria:

   1. Willingness and ability to complete all study-related assessments, including
   Participant-Reported Outcome (PRO) assessments, in the investigator's judgement.

   2. Adequate hematologic and organ function within 14 days before the first study
   treatment on Day 1 of Cycle 1.

   3. Life expectancy of at least 6 months.

   4. Measurable disease according to Response Evaluation Criteria in Solid Tumors, Version
   1.1 (RECIST v 1.1).

   5. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1.

   6. For women of childbearing potential: agreement to remain abstinent (refrain from
   heterosexual intercourse) or use contraception, and agreement to refrain from donating
   eggs.

   7. For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use
   contraceptive methods, and agreement to refrain from donating sperm.

   8. Appropriate candidate for paclitaxel monotherapy if tumor programmed death-ligand 1
   (PD-L1) status is unknown or non-positive; appropriate candidate for paclitaxel and
   atezolizumab if tumor PD-L1 status is positive.

   9. Histologically documented triple-negative adenocarcinoma of the breast that is locally
   advanced or metastatic and is not amenable to resection with curative intent.

Exclusion Criteria:

   1. Inability to comply with study and follow-up procedures.

   2. History of malabsorption syndrome or other condition that would interfere with enteral
   absorption or results in the inability or unwillingness to swallow pills.

   3. Severe infection within 4 weeks prior to initiation of study treatment (including, but
   not limited to, hospitalization for complications of infection, bacteremia, or severe
   pneumonia) as well as those who have received treatment with therapeutic oral or
   intravenous (IV) antibiotics within 2 weeks prior to initiation of study treatment.

   4. Known human immunodeficiency virus (HIV) infection (there must be a negative HIV test
   at screening).

   5. Known clinically significant history of liver disease consistent with Child-Pugh Class
   B or C.

   6. Current treatment with anti-viral therapy for hepatitis B virus (HBV).

   7. 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
   during the study.

   8. Pregnancy or breastfeeding, or intention to become pregnant during the study or within
   28 days after the final dose of ipatasertib or (/) placebo, 5 months after the final
   dose of atezolizumab/placebo, and 6 months after the final dose of paclitaxel
   whichever occurs later.

   9. New York Heart Association Class II, III, or IV heart failure, left ventricular
   ejection fraction less than (<) 50 percent (%), or active ventricular arrhythmia
   requiring medication.

10. Current unstable angina or history of myocardial infarction within 6 months prior to
   Day 1 of Cycle 1.

11. Congenital long QT syndrome or screening QT interval corrected through use
   Fridericia's formula (QTcF) greater than (>) 480 milliseconds (ms).

12. Current treatment with medications used at doses known to cause clinically relevant
   prolongation of QT/QTc interval.

13. History or presence of an abnormal ECG that is clinically significant in the
   investigator's opinion (including complete left bundle branch block, second- or
   third-degree heart block, or evidence of prior myocardial infarction).

14. Requirement for chronic corticosteroid therapy of > 10 mg of prednisone per day or an
   equivalent dose of other anti-inflammatory corticosteroids or immunosuppressant agents
   for a chronic disease.

15. Treatment with approved or investigational cancer therapy within 14 days prior to Day
   1 of Cycle 1.

16. Any other disease, metabolic dysfunction, physical examination finding, or clinical
   laboratory finding that, in the investigator's opinion, gives reasonable suspicion of
   a disease or condition that contraindicates the use of an investigational drug or that
   may affect the interpretation of the results or renders the participant at high risk
   from treatment complications.

17. History of or known presence of spinal cord metastases, as determined by computed
   tomography (CT) or magnetic resonance imaging (MRI) evaluation during screening or
   prior radiographic assessments.

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

19. Known germline breast cancer gene (BRCA)1/2 deleterious mutation, unless the
   participant is not an appropriate candidate for a poly adenosine diphosphate ribose
   polymerase (PARP)-inhibitor.

20. Any previous systemic therapy for inoperable locally advanced or metastatic
   triple-negative adenocarcinoma of the breast.

21. Unresolved, clinically significant toxicity from prior therapy, except for alopecia
   and Grade 1 peripheral neuropathy.

22. Participants who have received palliative radiotherapy 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 may be enrolled in the study if they have recovered from all acute,
   reversible effects (e.g., to Grade 1 or resolved by enrolment).

23. Uncontrolled pleural effusion, pericardial effusion or ascites.

24. Uncontrolled tumor-related pain.

25. Malignancies other than breast cancer within 5 years prior to Day 1 of Cycle 1, except
   for appropriately treated carcinoma in situ of the cervix, non-melanoma skin
   carcinoma, or Stage I uterine cancer.

26. Known hypersensitivity or contraindication to any component of the study treatments,
   including the paclitaxel excipient, macrogolglycerol ricinoleate.

27. Grade greater than or equal to (≥) 2 peripheral neuropathy.

28. History of Type I or Type II diabetes mellitus requiring insulin.

29. Grade ≥ 2 uncontrolled or untreated hypercholesterolemia or hypertriglyceridemia.

30. History of or active inflammatory bowel disease (e.g., Crohn disease and ulcerative
   colitis) or active bowel inflammation (e.g., diverticulitis).

31. Lung disease: pneumonitis, interstitial lung disease, idiopathic pulmonary fibrosis,
   cystic fibrosis, Aspergillosis, active tuberculosis, or history of opportunistic
   infections (pneumocystis pneumonia or cytomegalovirus pneumonia).

32. Treatment with strong Cytochrome P450 (CYP)3A inhibitors or strong CYP3A inducers
   within 2 weeks or 5 drug-elimination half-lives, whichever is longer, prior to
   initiation of study drug.

33. Prior treatment with an Protein kinase B (Akt) inhibitor.

34. Active or history of autoimmune disease or immune deficiency.

35. History of idiopathic pulmonary fibrosis, organizing pneumonia (e.g., bronchiolitis
   obliterans), drug-induced pneumonitis, idiopathic pneumonitis, or evidence of active
   pneumonitis on screening chest CT scan.

36. Prior allogeneic stem cell or solid organ transplantation.

37. 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 final dose of atezolizumab.

38. History of severe allergic anaphylactic reactions to chimeric or humanized antibodies
   or fusion proteins.

39. Known hypersensitivity to Chinese hamster ovary cell products or recombinant human
   antibodies.

40. Treatment with systemic immunostimulatory agents (including, but not limited to,
   interferon and interleukin-2) within 4 weeks or 5 half-lives of the drug (whichever is
   longer) prior to initiation of study treatment.

41. 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 study.