FDA Approval Summary: Abemaciclib With Endocrine Therapy for High-Risk Early Breast Cancer.

Area of Science:

• Oncology
• Clinical Pharmacology
• Medical Treatment

Background:

• Hormone receptor-positive, human epidermal growth factor receptor 2-negative, node-positive early breast cancer (EBC) presents a significant risk of recurrence.
• Identifying patients with EBC at high risk of recurrence is crucial for optimizing adjuvant treatment strategies.

Purpose of the Study:

• To evaluate the efficacy and safety of abemaciclib in combination with endocrine therapy (ET) for the adjuvant treatment of adult patients with EBC.
• To determine the specific subgroup of EBC patients who benefit most from this combination therapy based on risk factors like Ki-67 score.

Main Methods:

• The monarchE trial, a phase III, open-label, multicenter study, randomly assigned 5,637 patients with EBC to receive either abemaciclib plus ET or ET alone.
• Abemaciclib was administered orally at 150 mg twice daily for a duration of 2 years.
• Key endpoints included invasive disease-free survival (IDFS) and overall survival (OS), with subgroup analyses based on Ki-67 scores.

Main Results:

• The combination of abemaciclib and ET demonstrated a statistically significant improvement in IDFS for patients with EBC at high risk of recurrence and a Ki-67 score ≥ 20% (HR, 0.643; P = .0042).
• No detriment in overall survival was observed in this subgroup (HR, 0.767).
• Higher rates of treatment-emergent adverse events were noted in the abemaciclib plus ET arm compared to ET alone.

Conclusions:

• Abemaciclib in combination with ET is approved for adjuvant treatment in adult patients with hormone receptor-positive, HER2-negative, node-positive EBC who have a high risk of recurrence and a Ki-67 score ≥ 20%.
• This targeted approval is based on a favorable benefit-risk profile, showing a significant IDFS advantage without compromising survival in the identified patient subgroup.