Ribociclib Named a Breakthrough Therapy by the FDA

Designation comes with quicker approval process
Breast Cancer News
February 19, 2018
Eric Fitzsimmons, Copy Editor and Content Coordinator
Reviewed By: 
Diana Lake, MD

The U.S. Food and Drug Administrationinfo-icon gave ribociclib (Kisqali) breakthrough therapy designation based on recent results in pre- and perimenopausalinfo-icon women with advanced-stageinfo-icon, hormone receptorinfo-icon-positive breast cancer.

The designation was announced by the medicineinfo-icon’s maker, Novartis, on January 3 and means the FDAinfo-icon will provide resources to consider the new use of ribociclib more quickly.


Ribociclib is a CDK 4/6 inhibitor, a targeted therapyinfo-icon that blocks the actions of two proteins, cyclin dependent kinases 4 and 6, that cause some breast cancers to grow. The FDA approved it in August 2017 to be given with the aromatase inhibitorinfo-icon letrozoleinfo-icon to women with hormone receptor-positive, HER2-negative metastaticinfo-icon breast cancer who have already been through menopauseinfo-icon. CDK 4/6 inhibitors are relatively new treatments – palbociclib (Ibrance) was the first of this type approved, in 2015 – and researchers are still studying new uses and combinations for these medicines.

The FDA's breakthrough therapyinfo-icon designation for ribociclib came in response to results from the phase III MONALEESA-7 trial. The full study has not been published but some results were presented at the San Antonio Breast Cancer Symposium in December. The MONALEESA-7 trial was designed to see if ribociclib would also improve results for women with advanced hormone receptor-positive breast cancer who were pre- or perimenopausal, meaning they still have menstrual periods regularly or on occasion.

The trial randomly assigned 672 women who had not been given previous treatment for advanced breast cancer to one of two groups:

  • 335 women were given ribociclib in combination with hormonal therapyinfo-icon
  • 337 women were given a placeboinfo-icon  in combination with hormonal therapy

The hormonal therapy was either tamoxifeninfo-icon or a nonsteroidal aromatase inhibitorinfo-icon and goserelininfo-icon (Zoladex), a medicine used to stop the function of the ovaries, including menstrual periods, while it is being taken.

Researchers found that, on average, the group taking ribociclib lived longer without signs of the cancer growing, called progression-free survivalinfo-icon. The medianinfo-icon progression-free survival in the MONALEESA-7 trial was

  • 23.8 months for women taking ribociclib
  • 13 months for women taking a placebo

The improvement was consistent whether the women took tamoxifen or an aromatase inhibitor.

Side effects were what researchers expected for ribociclib, the most common being neutropenia, a low count of certain white blood cells that was experienced by more than half the women taking ribociclib. But only 3.6 percent of women stopped taking ribociclib due to side effects, compared to 3 percent of women taking a placebo.

Breakthrough therapy designation is an FDA program to help medicines that seem to provide better treatment than what is available now move more quickly through the approval process. The FDA works more closely with the medicine’s maker to design studies to best answer the FDA's concerns and offers a rolling review process to approve parts of the application as they are finished.

What This Means for You

Ribociclib, if approved, will be the first CDK 4/6 inhibitor for women with breast cancer who have not been through menopause. Because its first approval in 2015 was only for use in women who already went through menopause, young women have not had the benefits of treatment with this class of medicines. This approval for use in premenopausalinfo-icon women could mean longer progression-free survival with fewer side effects for this group. If you are still getting your period, whether regularly or occasionally, the MONALEESA-7 trial showed ribociclib can work similarly for you as it does for postmenopausalinfo-icon women, though young women will have to pair it with ovarian suppressioninfo-icon.

Being able to stay on a treatment longer without cancer growing may be a benefit itself because it means more time without having to change to different medicines with different side effects. Ribociclib hasn’t been found to cause many side effects, and the most common ones are changing blood cellinfo-icon counts, something your doctor will watch and address but you won’t feel.

At the conference where the MONALEESA-7 results were presented, some doctors said the findings should change practice. Ribociclib was tested as a first treatment after diagnosisinfo-icon with metastatic breast cancer. It may be several months for FDA to make its final decision on this treatment, but if the new use is approved, it could benefit pre- and perimenopausal women with metastatic breast cancer in the future, as well as those taking hormonal therapy in this setting.  

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