Filipa Lynce, MD

Formal discussant of the MONARCH 1 trial and the MONALEESA-2 biomarker analysis, Filipa Lynce, MD, of Georgetown Lombardi Comprehensive Cancer Center, Washington, DC, noted that this is the first study to evaluate a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor in patients with progressive disease after two or more lines of prior chemotherapy.

“Abemaciclib has similar efficacy to chemotherapy with better tolerability after one or two chemotherapy regimens in the metastatic setting. A limitation of MONARCH 1 is that this is a phase II single-arm study. Also, we have no data on the drug’s efficacy after previous exposure to CDK4/6 inhibitors, which may limit the number of eligible patients,” she said.

“We need biomarkers to identify patients who will benefit and who will be nonresponders. Some patients will do well on endocrine therapy alone, with better tolerability and lower cost, avoiding the need for additional monitoring with CDK4/6 inhibitors,” Dr. Lynce said. ■

Disclosure: Dr. Lynce has received grant and research support from Genentech/Roche and Pfizer.