Letrozole Plus Ribociclib or Placebo as Neo-adjuvant Therapy in ER-positive, HER2-negative Early Breast Cancer

Key Inclusion Criteria:

Pathologically confirmed invasive breast cancer by core needle biopsy
Female subjects, age ≥ 18 years
Only postmenopausal women will be eligible.
Performance Status: Eastern Cooperative Oncology Group (ECOG) score 0-2
Invasive breast cancer must be ER+ in ≥66 % of the cells or ER Allred score 6-8
Invasive breast cancer must be HER2 negative.
Clinical Stage II or III (by clinical measurement and/or breast imaging)

Key Exclusion Criteria:

Subjects meeting any of the exclusion criteria at baseline will be excluded from study participation.
Current use of other investigational agents
Inflammatory breast cancer defined as clinically significant erythema of the breast and/or documented dermal lymphatic invasion (not direct skin invasion by tumor or peau d'orange without erythema)
An excisional biopsy of this breast cancer
Surgical axillary staging procedure prior to study entry
Hormone replacement therapy of any type, megestrol acetate, or raloxifene within four weeks prior to first study treatment
Clinical or radiographic evidence of metastatic disease
Clinically significant, uncontrolled heart disease
Herbal preparations/medications as listed in Appendix B of the protocol