CDK4/6 Inhibitor
Abemaciclib
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Key Inclusion Criteria
- Unresectable, locally advanced recurrent or metastatic hormone-receptor-positive (HR+), HER2-positive breast cancer
- Availability of tumor tissue sample
- Measurable and/or nonmeasurable disease as defined by Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1
- Previous treatment with at least two HER2-directed therapies for advanced disease, and received trastuzumab emtansine and a taxane in any disease setting
- Postmenopausal status
- Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
- Adequate organ function
- Left ventricular ejection fraction of 50% or higher at baseline
- Negative serum pregnancy test within 14 days prior to randomization and must agree to use medically approved precautions to prevent pregnancy during the study and for 12 weeks following the last dose of abemaciclib if postmenopausal status is due to ovarian suppression due to a GnRH agonist or radiation
- Discontinuation of all previous therapies for cancer (including chemotherapy, radiotherapy, immunotherapy, and endocrine therapy), except trastuzumab, for at least 21 or 14 days for myelosuppressive or nonmyelosuppressive agents, respectively
- Discontinuation of previous localized radiotherapy for palliative purposes or for lytic lesions at risk of fracture at least 2 weeks prior to randomization
- Able to swallow capsules
Key Exclusion Criteria
- Visceral crisis
- Known central nervous system metastases that are untreated, symptomatic, or require steroids to control symptoms
- Prior treatment with any cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor
- Major surgery within 14 days prior to randomization
- Prior treatment with a drug that has not received regulatory approval for any indication within 14 to 21 days of randomization for a nonmyelosuppressive or myelosuppressive agent, respectively
- Serious preexisting medical conditions that would preclude participation in this study
- History within the last 6 months of symptomatic congestive heart failure, myocardial infarction, or unstable angina
- Syncope of cardiovascular etiology, ventricular tachycardia, ventricular fibrillation, or sudden cardiac arrest within the last 12 months
- History of any other cancer (except nonmelanoma skin cancer or carcinoma in situ of the cervix) unless in complete remission with no therapy for a minimum of 3 years
- Active bacterial, fungal, or viral infection
- Any live virus vaccination within 28 days prior to randomization
- Hypersensitivity to trastuzumab, murine proteins, fulvestrant, or any excipients