The US Food and Drug Administration (FDA) approved abemaciclib with an aromatase inhibitor (AI) for first-line endocrine-based therapy in postmenopausal patients with hormone receptor (HR)-positive, HER2-negative advanced or metastatic breast cancer, according to a press release.1

Abemaciclib — a CDK 4/6 inhibitor — was previously approved for HR-positive, HER2-negative metastatic breast cancer in combination with fulvestrant following disease progression after endocrine therapy, and as monotherapy for HR-positive, HER2-negative advanced or metastatic breast cancer among patients who had failed endocrine and chemotherapy.

The FDA based its approval on findings from the phase 3 MONARCH trial ( Identifier: NCT02246621), for which researchers randomly assigned 493 postmenopausal women who had not received prior systemic therapy to abemaciclib 150 mg or placebo twice on a daily continuous schedule, plus anastrozole 1 mg or letrozole 2.5 mg daily.

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Abemaciclib plus AI significantly improved progression-free survival (PFS), nearly doubling PFS time compared with placebo and AI (28.2 months vs 14.8 months, respectively; hazard ratio [HR], 0.54; 95% CI, 0.418-0.698; P < .0001).

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Patients in the abemaciclib arm also had an objective response rate of 55.4% compared with 40.2% among patients treated with placebo, and the median duration of response was 27.4 months vs 17.5 months among patients treated with abemaciclib vs placebo, respectively.

The most frequently observed grade 3 to 4 adverse events included neutropenia, leukopenia, diarrhea, infections, fatigue, abdominal pain, anemia, nausea, and vomiting.2


  1. Lilly received additional FDA approval for Verzenio (abemaciclib) as initial treatment for advanced breast cancer [press release]. Indianapolis, IN: Eli Lilly and Company; February 26, 2017. Accessed February 27, 2018.
  2. FDA approves abemaciclib as initial therapy for HR-positive, HER2-negative metastatic breast cancer [news release]. Silver Spring, MD: US Food and Drug Administration; February 26, 2018. Accessed February 27, 2018.