postMONARCH; NCT05169567

Breast Cancer

CDK4 & 6 Inhibitor

A Randomized, Double-Blind, Placebo-Controlled, Phase 3 Study to Compare the Efficacy of Abemaciclib Plus Fulvestrant to Placebo Plus Fulvestrant in Participants With HR+, HER2-, Advanced or Metastatic Breast Cancer Following Progression on a CDK4 & 6 Inhibitor and Endocrine Therapy*

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Key Inclusion Criteria
  • Hormone-receptor-positive (HR+), HER2-negative (HER2-) locally advanced or metastatic breast cancer
  • Radiologic evidence of disease progression or recurrence either:
    • On treatment with a CDK4 & 6 inhibitor with aromatase inhibitor (AI) as initial therapy for advanced disease, or
    • On/after treatment with a CDK4 & 6 inhibitor plus endocrine therapy (ET) administered as adjuvant therapy for early-stage breast cancer
  • Must be deemed appropriate for treatment with ET
  • If female, have a postmenopausal status by natural or surgical means or by ovarian function suppression
  • Measurable disease and/or nonmeasurable disease as defined by Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1
  • Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
  • Adequate renal, hematologic, and hepatic organ function
  • Able to swallow capsules/tablets
Key Exclusion Criteria
  • Visceral crisis, lymphangitic spread, or leptomeningeal carcinomatosis
  • Symptomatic or untreated central nervous system metastasis
  • Received any systemic therapy between disease recurrence/progression and study screening
  • Received more than one line of therapy for advanced or metastatic disease
  • Prior chemotherapy for metastatic breast cancer (MBC)
  • Prior treatment with fulvestrant, any investigational estrogen receptor (ER)-directed therapy (including selective ER degraders [SERDs] and non-SERDs), any PI3K, mTOR, or AKT inhibitor
This clinical trial is being conducted globally.
Abemaciclib or placebo equivalent is administered PO.
Fulvestrant is administered intramuscularly.
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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.