MONARCH 3: Abemaciclib As Initial Therapy for Advanced Breast Cancer

This RCT (n=493) reports addition of abemaciclib to a nonsteroidal aromatase inhibitor resulted in a significantly prolonged progression-free survival compared to placebo (median: not reached in the abemaciclib arm, 14.7 months in the placebo arm; HR 0.54, P = 0.000021).

Abemaciclib is a cyclin-dependent kinase 4 and 6 inhibitor. This study (MONARCH 3) is a double-blind, randomized phase III study of abemaciclib or placebo plus a nonsteroidal aromatase inhibitor in postmenopausal women with HR-positive, HER2-negative advanced breast cancer who had no prior systemic therapy in the advanced setting.

 

The US FDA has approved abemaciclib for the treatment of adults with hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced or metastatic breast cancer that has progressed after endocrine therapy.