['advanced or metastatic breast cancer']
['lee011', 'buparlisib', 'letrozole']

        Inclusion Criteria:

          1. Women with advanced (recurrent or metastatic) breast cancer who received no prior
             therapy for advanced disease.

          2. Patient is postmenopausal.

          3. Patient may have received ≤ 2 lines of chemotherapy for metastatic or recurrent breast
             cancer in the dose-escalation phase.

          4. Patient has a histologically and/or cytologically confirmed diagnosis of
             estrogen-receptor positive and/or progesterone receptor positive breast cancer by
             local laboratory.

          5. Patient has HER2-negative breast cancer defined as a negative in situ hybridization
             test or an IHC status of 0, 1+ or 2+. If IHC is 2+, a negative in situ hybridization
             (FISH, CISH, or SISH) test is required by local laboratory testing.

          6. Patient must have either:

               -  Measurable disease, i.e., at least one measurable lesion as per RECIST 1.1
                  criteria or at least one predominantly lytic bone lesion

        Exclusion Criteria:

          1. Patient who received any CDK4/6 or PI3K inhibitor.

          2. Patient has active cardiac disease or a history of cardiac dysfunction including any
             of the following:

               -  History of angina pectoris, symptomatic pericarditis, or myocardial infarction
                  within 12 months prior to study entry

               -  History of documented congestive heart failure (New York Heart Association
                  functional classification III-IV)

               -  Documented cardiomyopathy

               -  Patient has a Left Ventricular Ejection Fraction (LVEF) < 50% as determined by
                  Multiple Gated acquisition (MUGA) scan or echocardiogram (ECHO)

               -  History of any cardiac arrhythmias, e.g., ventricular, supraventricular, nodal
                  arrhythmias, or conduction abnormality in the previous 12 months.

               -  On screening, any of the following cardiac parameters: bradycardia (heart rate <
                  50 at rest), tachycardia (heart rate > 90 at rest), PR interval > 220 msec, QRS
                  interval >109 msec, or QTcF >450 msec.

             Systolic blood pressure >160 or <90 mmHg

          3. Patient is currently receiving any of the following medications:

               -  That are known strong inducers or inhibitors of CYP3A4.

               -  That have a known risk to prolong the QT interval or induce Torsades de Pointes.

               -  That have a narrow therapeutic window and are predominantly metabolized through
                  CYP3A4.

          4. Certain scores on an anxiety and depression mood questionnaires
      