New Breast Cancer Rx Class Gets Good Review

A new class of breast cancer medications appeared to have manageable side effects for most patients, according to a new study.

Most patients with hormone receptor-positive (HR+) metastatic breast cancer tolerated cyclin-dependent kinase (CDK) inhibitors well, this study found. 

The US Food and Drug Administration (FDA) approved the first CDK inhibitors for breast cancer treatment relatively recently. This study looked at palbociclib (brand name Ibrance), ribociclib (Kisqali) and abemaciclib. The third drug, abemaciclib, received FDA Breakthrough Therapy designation and is undergoing Phase III clinical trials.

CDK inhibitors work by blocking the activity of enzymes known as CDKs, particularly CDK 4 and CDK 6, and in turn, stop cell growth and division in breast cancer.

The authors of this study looked at all the available research on palbociclib, ribociclib and abemaciclib. A low white blood cell count (neutropenia) was the most common side effect of palbociclib and ribociclib. The study authors noted neutropenia is rapidly reversible and can be managed by dose adjustments when needed. 

Abemaciclib appeared to pose a lower risk of neutropenia, but it was more likely to cause tiredness and diarrhea. Other CDK inhibitor side effects this study identified included temporary hair loss and nausea.

This study was published in the journal The Oncologist.

Grants from the National Cancer Institute supported the study authors. The authors disclosed no potential conflicts of interest.