Inclusion Criteria:

- Female ≥ 18 years

- ECOG performance status ≤ 2

- Histologically and/or cytologically confirmed diagnosis of breast cancer presenting
with metastatic disease (hormone receptor positive and HER2 negative)

- Known PI3K activation status (defined by PIK3CA (Phosphoinositide-3-kinase,
catalytic, alpha polypeptide) mutation and PTEN PTEN (Phosphatase and Tensin Homolog)
mutation/expression)

- Prior treatment with at least one prior line of endocrine therapy and at least two
and no more than three prior lines of chemotherapy for metastatic breast cancer

- Objective and radiologically confirmed progression of disease after prior treatment
and at least one measurable lesion as per RECIST

- Adequate bone marrow and organ function

Exclusion Criteria:

- Previous treatment with PI3K and/or mTOR inhibitors

- Symptomatic Central Nervous System (CNS) metastases

- Concurrent malignancy or malignancy in the last 5 years prior to start of study
treatment

- Wide field radiotherapy ≤ 28 days or limited field radiation for palliation ≤ 14 days
prior to starting study drug

- Active cardiac disease (e.g. Left Ventricular Ejection Fraction (LVEF) < 50%, QTcF >
480 msec on screening ECGelectrocardiogram (ECG), unstable angina pectoris,
ventricular, supraventricular or nodal arrhythmias)

- Inadequately controlled hypertension

- Impairment of gastrointestinal (GI) function or GI disease that may significantly
alter the absorption of BEZ235

- Treatment at start of study treatment with drugs with a known risk to induce Torsades
de Pointes, moderate and strong inhibitors or inducers of isoenzyme CYP3A4, warfarin
and coumadin analogues, LHRH agonists

- History of photosensitivity reactions to other drugs

- Pregnant or nursing (lactating) woman

Other protocol-defined inclusion/exclusion criteria may apply