This is a multicenter, single-arm, open-label Phase II study to evaluate the activity of GDC-0980 in patients with recurrent or persistent endometrial cancer. The safety, tolerability, and pharmacokinetics of GDC-0980 will also be evaluated.

Inclusion Criteria:

• Patients must have recurrent or persistent endometrial carcinoma that is refractory to curative therapy or established treatments
• Histologic confirmation of the original primary tumor is required
• Histologic or cytologic confirmation of the recurrent/progressive disease is desired
• Patients must have had at least one but no more than two prior chemotherapeutic regimens for management of endometrial carcinoma
• Disease that is measurable per RECIST v1.1
• No active infection requiring antibiotics
• Any hormonal therapy directed at the malignant tumor must be discontinued at least 2 weeks prior to first study treatment
• Any other prior therapy directed at the malignant tumor, including immunologic agents and radiotherapy, must be discontinued at least 2 weeks prior to first study treatment
• Adequate hematologic and end organ function

Exclusion Criteria:

• Type I diabetes or Type II diabetes requiring insulin
• Prior use of mTOR/PI3K inhibitor
• Current dyspnea at rest or any requirement for supplemental oxygen therapy to perform activities of daily living
• Previous diagnosis of pulmonary fibrosis of any cause
• History of myocardial infarction or unstable angina within 6 months prior to first study treatment
• Congestive heart failure
• History of malabsorption syndrome or other condition that would interfere with enteral absorption
• Clinically significant history of liver disease, including cirrhosis and current alcohol abuse
• Presence of positive test results for hepatitis B or hepatitis C
• Known HIV infection
• Active autoimmune disease that is not controlled by nonsteroidal anti inflammatory drugs
• Need for current chronic corticosteroid therapy
• Pregnancy, lactation, or breastfeeding
• Current severe, uncontrolled systemic 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
• Uncontrolled hypercalcemia
• Leptomeningeal disease as a manifestation of cancer
• Known untreated or active brain metastases
• Grade >=2 hypercholesterolemia or hypertriglyceridemia