Trastuzumab and Trastuzumab-MCC-DM1 Administered Intravenously and GDC-0941 Administered Orally to Patients With HER2-Positive Metastatic Breast Cancer Who Have Progressed on Previous Trastuzumab-Based Therapy

Inclusion Criteria:

* Histologically documented locally advanced or metastatic breast cancer that has progressed on at least one trastuzumab-based regimen in the metastatic or locally advanced setting
* HER2-positive disease documented by one of the following results using FDA-approved testing methods: FISH-positive, chromogenic in situ hybridization (CISH)-positive, or IHC 3 + by local laboratory assessment
* Life expectancy \>= 90 days
* Agreement to use an effective form of contraception for the duration of the study

Exclusion Criteria:

* History of Grade \>= 3 hypersensitivity reaction to trastuzumab, or Grade \>= 1 with the most recent trastuzumab infusion before study entry, or continued requirement for prolonged trastuzumab infusions to prevent hypersensitivity reactions
* History of intolerance to trastuzumab and/or adverse events related to trastuzumab that resulted in trastuzumab being permanently discontinued
* Prior anti-cancer therapy (e.g., biologic or other targeted therapy, chemotherapy, hormonal therapy) within 2 weeks prior to Day 1
* Prior investigational anti-cancer therapy within 4 weeks prior to Day 1
* Grade \>= 2 peripheral neuropathy
* History of Grade \>= 3 hyperglycemia (fasting)
* History of Type 1 or Type 2 diabetes requiring daily medication
* History of clinically significant cardiac or pulmonary dysfunction
* History of malabsorption syndrome or other condition that would interfere with enteral absorption
* Clinically significant history of liver disease, including cirrhosis, current alcohol abuse, or current known active infection with HIV, hepatitis B virus, or hepatitis C virus
* Any condition requiring anticoagulants, such as warfarin, heparin, or thrombolytic agents
* Any condition requiring \> 2 grams of acetaminophen daily
* Need for current chronic corticosteroid therapy
* Pregnancy, lactation, or breast-feeding
* Current severe, uncontrolled systemic disease (e.g., clinically significant cardiovascular, pulmonary, or metabolic disease)
* Major surgical procedure or significant traumatic injury within 28 days prior to Day 1, or anticipation of the need for major surgery during the course of study treatment
* Symptomatic hypercalcemia requiring continued use of bisphosphonate therapy
* Known brain metastases that are untreated, symptomatic, or require therapy to control symptoms