CDK4/6 Inhibitors

What are CDK4/6 inhibitors?

Cyclin-dependent kinase 4 and 6 (CDK4 and CDK6) are enzymes important in cell division. CDK4/6 inhibitors are drugs designed to interrupt the growth of cancer cells.

CDK4/6 inhibitors are used in combination with hormone therapy to treat some breast cancers.

CDK4/6 inhibitors are pills.

Drug name

Brand name

Used to treat early or metastatic breast cancer?

Abemaciclib

Verzenio

Early and metastatic breast cancer

Palbociclib

Ibrance

Metastatic breast cancer

Ribociclib

Kisqali

Metastatic breast cancer

Learn about CDK4/6 inhibitors and metastatic breast cancer treatment.

Abemaciclib (Verzenio) and early breast cancer treatment

Abemaciclib (Verzenio) is a CDK4/6 inhibitor drug. Abemaciclib in combination with hormone therapy (tamoxifen or an aromatase inhibitor). Hormone therapy drugs are used to treat hormone receptor-positive breast cancers.

Abemaciclib in combination with hormone therapy is FDA-approved for the treatment of early breast cancers that are all of the following [282-283]:

Study findings show hormone therapy plus abemaciclib may reduce the risk of breast cancer recurrence better than hormone therapy alone in women with hormone receptor-positive, HER2-negative breast cancers at high risk of recurrence [68].

How is abemaciclib given?

Abemaciclib is a pill taken twice a day for two years. It is only given in combination with tamoxifen or an aromatase inhibitor.

You begin taking abemaciclib after breast cancer surgery.

Learn more about the hormone therapy drugs tamoxifen and aromatase inhibitors.

Side effects of abemaciclib

Some possible side effects of abemaciclib include diarrhea, low white blood cell counts, low white blood cell count, nausea, abdominal pain, fatigue, low red blood cell count (anemia), vomiting, hair loss and blood clots [283].

In some cases, abemaciclib can cause liver problems. Your liver function will be checked before treatment begins and throughout your treatment [283].

In rare cases, abemaciclib can cause lung inflammation, which can cause death. Tell your health care provider right away if you have shortness of breath or other breathing problems while taking abemaciclib [283].

CDK4/6 inhibitors and metastatic breast cancer treatment

The CDK4/6 inhibitors abemaciclib, palbociclib and ribociclib are FDA-approved for the treatment of some metastatic breast cancers.

Learn about CDK4/6 inhibitors and metastatic breast cancer treatment.

Under study

Palbociclib (Ibrance) and ribociclib (Kisqali)

The CDK4/6 inhibitors palbociclib and ribociclib are under study for the treatment of early breast cancer. They are FDA-approved for the treatment of metastatic breast cancer.

Neoadjuvant therapy

Abemaciclib is FDA-approved for the adjuvant treatment (given after surgery) of some early breast cancers. Abemaciclib and other CDK4/6 inhibitors are under study for use in the neoadjuvant treatment (before surgery) setting [67].

Learn more about emerging drug therapies for early breast cancer.

Updated 11/03/21