Inclusion Criteria:

          -  Adult men and women

          -  Patient has a confirmed diagnosis of estrogen-receptor positive and/or progesterone
             receptor positive breast cancer by local laboratory and has HER2-negative breast
             cancer

          -  Patient must have either measurable disease by RECIST 1.1 or bone lesions in absence
             of measurable disease.

          -  ECOG Performance Status 0 - 1

          -  Disease refractory to either, AI, tamoxifen or fulvestrant

          -  Previously treated on any CDK 4/6 inhibitor.

          -  Patient has adequate bone marrow and organ function.

        Exclusion Criteria:

          -  Patient with symptomatic visceral disease or any disease burden that makes the patient
             ineligible for endocrine therapy per the investigator's best judgment.

          -  Patient has received more than one line of chemotherapy for advanced disease.

          -  Previous treatment with mTOR inhibitors, or exemestane for advanced disease.

          -  Progressed on more than one CDK 4/6 inhibitor

          -  Patient with CNS involvement unless they are at least 4 weeks from prior therapy
             completion.

          -  Clinically significant, uncontrolled heart disease and/or recent cardiac events.