FDA Approves Ribociclib as a First Treatment Option for Metastatic Hormone Receptor-Positive Breast Cancer

This is only the second CDK 4/6 inhibitor, after palbociclib (Ibrance), to get FDA approval
Breast Cancer News
March 20, 2017
Erin Rowley, Writer and Content Coordinator
Reviewed By: 
Kathy D. Miller, MD

On March 13, the U.S. Food and Drug Administrationinfo-icon (FDAinfo-icon) approved ribociclib as a first treatment option for hormone receptorinfo-icon-positive, HER2-negative metastaticinfo-icon breast cancer, when given with an aromatase inhibitorinfo-icon. Ribociclib will be sold under the brand name Kisqali by the pharmaceutical company Novartis.


Ribociclib is a cyclin-dependent kinase (CDK) 4/6 inhibitor. Cyclin-dependent kinases 4 and 6 are two proteins that cause tumorinfo-icon cells in some breast cancers to grow. CDK 4/6 inhibitors like ribociclib work by blocking CDK 4 and 6 from telling cancer cells to multiply. This can slow the growth or spread of cancer cells.

Ribociclib is only the second CDK 4/6 inhibitor to be FDA-approved. The other is palbociclib (Ibrance).

Ribociclib was granted breakthrough therapy designation by the FDA in August 2016. This status can be given to medicines that are intended to treat a serious illness, like metastatic cancer, if early clinicalinfo-icon trials suggest the medicineinfo-icon works considerably better than existing therapies.

When a medicine gets breakthrough therapyinfo-icon designation, the FDA speeds up its normal review process. This way, if the medicine does get FDA approval, it can be made available to the public as soon as possible. 


Ribociclib was approved based on results from the phase III MONALEESA-2 trial, which LBBC reported on in November 2016. Researchers found that postmenopausalinfo-icon women who took ribociclib and the aromatase inhibitor letrozoleinfo-icon (Femarainfo-icon) had longer periods of progression-free survivalinfo-icon than those who took a placeboinfo-icon and letrozole. They found that 18 months after entering the study, the disease hadn’t progressed in

  • 63 percent of participants taking letrozole with ribociclib
  • 42 percent of participants taking letrozole with a placebo

Participants taking ribociclib did have more side effects though, including neutropenia, nausea and infections.

What This Means for You

Metastatic breast cancer is a disease you will have to treat for the rest of your life. Getting treatments to work longer means more time when the cancer isn’t growing and more time without having to switch to other medicines and experience new side effects.

Up until now, ribociclib has mostly only been available through clinical trials. Now that the FDA has approved it, ribociclib will be widely available.

Ribociclib and palbociclib seem quite similar, says Kathy D. Miller, MD, an associate professor and Sheila D. Ward Scholar at Indiana University and a member of LBBC’s Medical Advisory Board, but they haven’t been directly compared to each other in a trial. There is no reason for people who are doing well on palbociclib to switch to ribociclib, Dr. Miller says. Doctors don’t yet know if ribociclib will work if treatment with palbociclib stops working, or if palbociclib will work if treatment with ribociclib stops working.

Talk to your doctor about whether a CDK 4/6 inhibitor is a good treatment option for you, and about whether ribociclib or palbociclib would be best.

Additional Related Topics 
Hormone Receptor-Positive
Clinical Trials
Hormonal Therapy
Targeted Therapy
Nausea and Vomiting