Study of Efficacy of Ribociclib After Progression on CDK4/6 Inhibition in Patients With HR+ HER2- Advanced Breast Cancer

Inclusion Criteria

• Men or women at least 18 years of age with histologically or cytologically confirmed adenocarcinoma of the breast with unresectable or metastatic disease.
• Most recent tumor biopsy or surgical resection specimen must be either estrogen-receptor (ER) positive, progesterone receptors (PgR) positive, or both, as defined by immunohistochemistry (IHC) ≥1% (as per the American Society of Clinical Oncology (ASCO)-College of American Pathologists (CAP) guidelines).
• HER2-negative breast cancer defined as a negative in situ hybridization test or an immunohistochemistry (IHC) status of 0, 1+ or 2+. If IHC is 2+ (i.e. indeterminate), a negative in situ hybridization (Fluorescent in situ hybridization (FISH), Chromogenic in situ hybridization (CISH), or Silver-enhanced in situ hybridization (SISH)) test is required by local laboratory testing. (as per the ASCO-CAP guidelines).
• Postmenopausal status or receiving ovarian ablation with a GnRH agonist such as goserelin. Postmenopausal status ( is defined by any one of the following criteria:
• Prior bilateral oophorectomy.
• Age ≥60 years.
• Age 50 mL/min.
• In absence of liver metastases, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) should be below 2.5 × the upper limit of normal (ULN). If the patient has liver metastases, ALT and AST should be 160 or 450 msec (QT interval using Fridericia's correction) on screening electrocardiogram. If QTc prolongation is felt to be related to electrolyte imbalance, an EKG can be repeated after correction of electrolytes. Mean resting heart rate 50-100 bpm (determined from ECG).
• The presence of any other concurrent severe and/or uncontrolled medical condition that would, in the investigator or treating physician's judgment, cause unacceptable safety risks, contraindicate patient participation in the clinical study or compromise compliance with the protocol. This includes uncontrolled infections that could potentially be exacerbated by anti-neoplastic treatment, active untreated or uncontrolled fungal bacterial or viral infections, etc.
• Currently receiving treatment, including medications and herbal preparations, with known strong inducers or inhibitors of cytochrome p450 enzymes CYP3A4/5 medications that have a narrow therapeutic window and are predominately metabolized through CYP3A4/5 or herbal preparations/medications, dietary supplements, which cannot be discontinued prior to receiving investigational drug. Anti-retrovirals, anti-microbials, and anti-arrhythmics are the most common medications that interact with these enzyme. Please refer to Section 5: Pharmaceutical Information and Appendix B for more information and a list of drugs that should not be used concurrently with ribociclib.
• Patients who are receiving any other investigational agents concurrently or have received investigational agents within 14 days or 5 half-lives of the compound or active metabolites, whichever is longer before the first dose of the study treatment.

15 Patient is concurrently using hormone replacement therapy. 16. Subject is pregnant or nursing. Serum or urine Beta-Human chorionic gonadotropin (HCG) must be checked in all pre- and peri-menopausal patients. (Fulvestrant is pregnancy category D and CDK4/6 inhibitors have demonstrated teratogenicity/fetotoxicity in animal studies.)