eMonarcHER: A Randomized, Double Blind, Placebo-Controlled Phase 3 Study
eMonarcHER: A Randomized, Double Blind, Placebo-Controlled Phase 3 Study of Abemaciclib plus Standard Adjuvant Endocrine Therapy in Participants with High-Risk, Node-Positive, HR+, HER2+ Early Breast Cancer Who Have Completed Adjuvant HER2-Targeted TherapyeMonarcHER is a Phase 3 multicenter, randomized, double-blinded, placebo-controlled trial in participants with high-risk, node-positive, HR+, HER2+ early breast cancer who have completed adjuvant HER2-targeted therapy. Approximately 2450 participants will be enrolled in a 1:1 randomization. Participants will be assigned to blinded study drug (either the abemaciclib or placebo treatment arm) plus ET. Study intervention will be given for up to 26 cycles, approximately 2 years, or until evidence of disease recurrence or another discontinuation criterion is met, whichever occurs first.