To Evaluate the Safety, Tolerability, and Pharmacokinetics of GDC-0077 Single Agent in Participants With Solid Tumors and in Combination With Endocrine and Targeted Therapies in Participants With Breast Cancer

Inclusion Criteria:

- Evaluable or measurable disease per RECIST, Version 1.1

- Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

- Life expectancy of greater than or equal to (≥) 12 weeks

- Adequate hematologic and organ function, including blood counts, liver and kidney
function

Stage I Arm A (GDC-0077):

- Locally advanced, recurrent, or metastatic, PIK3CA mutant, incurable solid tumor
malignancy, including breast cancer

Stages I and II, Arms B and C, or Stage II Arm D:

- Postmenopausal female participants with locally advanced or metastatic PIK3CA-mutant
HR+/HER2- breast cancer

Stage II, Arms E or F:

- Female participants with locally advanced or metastatic PIK3CA-mutant HR+/HER2- breast
cancer

Stages I and II:

- All participants must provide tumor tissue from the primary or metastatic tumor site
obtained from a prior or new biopsy or surgical procedure for detection of PIK3CA
mutation by central laboratory test.

Exclusion Criteria:

- Inflammatory or metaplastic breast cancer

- History of leptomeningeal disease

- Type 1 or 2 diabetes requiring anti-hyperglycemic medication

- Inability or unwillingness to swallow pills

- Malabsorption syndrome or other condition that would interfere with enteral absorption

- Known and untreated, or active central nervous system metastases

- Uncontrolled pleural effusion or ascites

- History of other malignancy within 5 years, except for treated carcinoma in situ of
the cervix, non-melanoma skin carcinoma, or Stage I uterine cancer

- History of or active ventricular dysrhythmias or congestive heart failure requiring
medication or symptomatic coronary heart disease

- Congenital long QT syndrome, prolonged QT interval, or family history of sudden
unexplained death or long QT syndrome

Stage II:

- Stage II Arms B, C, D, and E only: Prior treatment with >1 chemotherapy regimen for
metastatic disease

- Prior treatment with PI3K inhibitor

- History of significant toxicity related to mTOR inhibitor requiring treatment
discontinuation

- Stage II Arms B and E only: prior CDK4/6 inhibitor treatment