Study of Letrozole With or Without BYL719 or Buparlisib, for the Neoadjuvant Treatment of Postmenopausal Women

Inclusion Criteria:

Patient is an adult, female ≥ 18 years old at the time of informed consent
Patient has a histologically and/or cytologically confirmed diagnosis of breast cancer
Patient is postmenopausal.
Patient has T1c-T3, any N, M0, operable breast cancer
Patients must have measurable disease
Patient has diagnostic biopsy available for the analysis of PIK3CA mutation and Ki67 level.
Patient has estrogen-receptor and/or progesterone positive breast cancer as per local laboratory testing
Patient has HER2 negative breast cancer defined as a negative in situ hybridization test or an IHC status of 0 or 1+ as per local laboratory testing

Exclusion Criteria:

Patient has locally recurrent or metastatic disease
Patient has received any systemic therapy (e.g. chemotherapy, targeted therapy, immunotherapy) or radiotherapy for current breast cancer disease before randomization.
Patient with type 1 diabetes mellitus or not adequately controlled type 2 diabetes mellitus
History of acute pancreatitis within 1 year of study entry
Uncontrolled hypertension