-  Have a diagnosis of ER+, HER2- locally advanced or metastatic breast cancer

          -  Have disease that has demonstrated progression on or after an aromatase inhibitor
             alone or in combination with a cyclin-dependent kinase (CDK)4/6 inhibitor.

          -  Must be deemed appropriate for treatment with endocrine therapy

          -  If female, have a postmenopausal status by natural or surgical means or by ovarian
             function suppression

          -  Have RECIST evaluable disease (measurable disease and/or nonmeasurable bone-only
             disease)

          -  Have a performance status of 0 or 1 on the Eastern Cooperative Oncology Group scale
             (Oken et al. 1982)

          -  Have adequate renal, hematologic, and hepatic organ function

          -  Must be able to swallow capsules/tablets

        Exclusion Criteria:

          -  Have received prior treatment with chemotherapy (except for neoadjuvant/ adjuvant
             chemotherapy), fulvestrant, or any investigational-ER-directed therapy (including
             SERDs and non-SERDs), any PI3K-, mTOR- or AKT- inhibitor

          -  Have visceral crisis, lymphangitic spread within the lung, or any evidence of
             leptomeningeal disease.

          -  Have symptomatic or untreated brain metastasis.

          -  Have serious preexisting medical conditions that, in the judgment of the investigator,
             would preclude participation in this study

          -  Known allergic reaction against any of the components of the study treatment