Inclusion Criteria:

          -  Adult women (≥ 18 years of age) with metastatic or locally advanced breast cancer

          -  Histological or cytological confirmation of ER+ breast cancer in dose escalation and
             HR+ breast cancer in dose expansion

          -  A representative tumor specimen must be available for molecular testing.

          -  Postmenopausal women. Postmenopausal status is defined either by:

          -  Age ≥ 18 with prior bilateral oophorectomy

          -  Age ≥ 60 years

          -  Age <60 years with amenorrhea for at least 12 months and both follicle-stimulating
             hormone (FSH) and estradiol levels are in postmenopausal range (according to the local
             laboratory)

          -  Recurrence while on, or within 12 months of end of adjuvant treatment with letrozole
             or anastrozole, or

          -  Progression while on, or within one month of end of letrozole or anastrozole treatment
             for locally advanced or metastatic breast cancer.

          -  Patients must have:

               -  Measurable disease*: At least one lesion that can be accurately measured in at
                  least one dimension ≥ 20 mm with conventional imaging techniques or ≥ 10 mm with
                  spiral CT or MRI or

               -  Bone lesions: lytic or mixed (lytic + sclerotic) in the absence of measurable
                  disease as defined above.

          -  ECOG Performance Status 0-1.

          -  Fasting serum cholesterol ≤ 300 mg/dl or 7.75 mmol/L and fasting triglycerides ≤ 2.5 ×
             ULN. In case one or both of these thresholds are exceeded, the patient can only be
             included after initiation of statin therapy and when the above mentioned values have
             been achieved

          -  Standard 12-lead ECG values defined as the mean of the triplicate ECGs and assessed by
             the central laboratory.

               -  QTcF interval at screening < 450 msec (using Fridericia's correction).

               -  Resting heart rate 50-90 bpm

        Exclusion Criteria:

          -  HER2-overexpressing patients by local laboratory testing (IHC 3+ staining or in situ
             hybridization positive).

          -  Patients who received more than one chemotherapy line for advanced breast cancer.

          -  Previous treatment with exemestane or mTOR inhibitors* (Note:

        Patients with disease refractory to prior LEE011 are excluded for dose expansion Group 3
        only).

          -  History of brain or other CNS metastases.

          -  Clinically significant, uncontrolled heart disease and/or recent cardiac
             repolarization abnormality including any of the following:

          -  History of myocardial infarction (MI), angina pectoris, symptomatic pericarditis, or
             coronary artery bypass graft (CABG) within 6 months prior to study entry

          -  Documented cardiomyopathy

          -  Left ventricular ejection fraction (LVEF) < 50% as determined by Multiple Gated
             acquisition scan (MUGA) or echocardiogram (ECHO)

          -  Long QT syndrome or family history of idiopathic sudden death or congenital long QT
             syndrome, and etc.

          -  Clinically significant cardiac arrhythmias, complete left bundle branch block,
             high-grade AV block

          -  Systolic Blood Pressure (SBP) >160 or <90 mmHg

          -  Patients who are currently receiving treatment with agents that are known to cause QTc
             prolongation in humans

          -  Patients who are currently receiving treatment (within 7 days prior to starting study
             treatment) with strong and moderate inhibitors or inducers of CYP3A4/5, substrates of
             CYP3A4/5 with a narrow therapeutic index or Herbal preparations/medications (Refer to
             Section 6.4 and Appendix 3)

        Inclusion Criteria Exceptions for Phase Ib Dose Expansion patients:

        Dose Expansion part of the study has 3 groups, following are the Inclusion Criteria
        exceptions for these 3 groups

          1. Group 1 - Patients must not have received prior treatment with any CDK4/6 inhibitors

          2. Group 2 - Patients must have disease progression while on or within one month after
             CDK4/6 inhibitor based therapy

          3. Group 3 - Patients must have disease progression while on or within one month after
             CDK4/6 inhibitor based therapy (except those patients who received prior LEE011 based
             therapy).

        Other protocol-defined Inclusion/Exclusion may apply.