A Study of PI3-Kinase Inhibitor GDC-0941 in Combination With Paclitaxel, With and Without Bevacizumab or Trastuzumab, and With Letrozole, in Participants With Locally Recurrent or Metastatic Breast Cancer

Inclusion Criteria:

* Confirmed adenocarcinoma of the breast with locally recurrent or metastatic disease
* Adequate organ and bone marrow function as assessed by laboratory tests
* Evaluable disease or disease measurable per RECIST
* Agreement to use an effective form of contraception for the duration of the study

Exclusion Criteria:

* History of malabsorption syndrome or other condition that would interfere with enteral absorption
* Any condition requiring full-dose anticoagulants, such as warfarin, heparin, or thrombolytic agents
* Prior anti-cancer therapy (e.g., chemotherapy, biologic therapy, radiotherapy, or hormonal therapy) within 4 weeks or 5 half-lives (whichever is shorter) of the first dose of study treatment
* Uncontrolled current illness
* Active small or large intestine inflammation (such as Crohn's disease or ulcerative colitis)
* Clinically significant history of liver disease, including cirrhosis, current alcohol abuse, or current known active infection with human immunodeficiency virus (HIV), hepatitis B virus, or hepatitis C virus
* Known HIV infection
* New York Heart Association (NYHA) Class II or greater congestive heart failure
* Active ventricular arrhythmia requiring medication
* Pregnancy, lactation, or breastfeeding
* Known significant hypersensitivity to study drugs or excipients
* History of arterial thromboembolic disease within 6 months of first study treatment
* No more than two prior chemotherapy regimens for metastatic disease