MONARCH 3; NCT02246621

Breast Cancer

CDK4 & 6 Inhibitor

A Randomized, Double-Blind, Placebo-Controlled, Phase 3 Study of Nonsteroidal Aromatase Inhibitors (Anastrozole or Letrozole) Plus LY2835219, a CDK4 & 6 Inhibitor, or Placebo in Postmenopausal Women With Hormone-Receptor-Positive, HER2-Negative Locoregionally Recurrent or Metastatic Breast Cancer With No Prior Systemic Therapy in This Disease Setting*

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Key Inclusion Criteria
  • Hormone-receptor-positive (HR+), HER2-negative breast cancer
  • Locoregionally recurrent disease not amenable to resection or radiation therapy with curative intent or metastatic disease
  • Adequate organ function
  • Postmenopausal status
  • Measurable disease or nonmeasurable bone-only disease
  • Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
  • Discontinuation of previous localized radiotherapy for palliative purposes or for lytic lesions at risk of fracture prior to randomization and recovery from the acute effects of therapy
  • Able to swallow capsules
Key Exclusion Criteria
  • Visceral crisis, lymphangitic spread, or leptomeningeal carcinomatosis
  • Inflammatory breast cancer
  • Clinical evidence or a history of central nervous system metastasis
  • Currently receiving or has previously received chemotherapy or endocrine therapy for locoregionally recurrent or metastatic breast cancer
  • Prior (neo)adjuvant endocrine therapy (eg, antiestrogens or aromatase inhibitors) with a disease-free interval ≤12 months from completion of treatment
  • Prior treatment with everolimus or any CDK4 & 6 inhibitor
  • Initiation of bisphosphonates or approved receptor activator of nuclear factor kappa-B ligand (RANK-L) targeted agents within 7 days of randomization 
  • Currently receiving an investigational drug in a clinical trial or participating in any other type of medical research judged not to be scientifically or medically compatible with this study
  • Treatment with a drug that has not received regulatory approval for any indication with 14 or 21 days of randomization for a nonmyelosuppressive or myelosuppressive agent, respectively
  • Major surgery within 14 days prior to randomization
This clinical trial is being conducted globally. 
Abemaciclib 150 mg or placebo equivalent is administered PO Q12H.
Anastrozole 1 mg is administered PO QD.
Letrozole 2.5 mg is administered PO QD.
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The safety and efficacy of the agents under investigation have not been established. There is no guarantee that the agents will receive regulatory approval and become commercially available for the uses being investigated.