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FDA Approval: Ribociclib (Kisqali) for Breast Cancer
FDA approved Ribociclib (Kisqali), a CDK4/6 inhibitor, for certain people with breast cancer. What was approved, the evidence, and what it does and doesn't mean.
Original commentary from the Cancer Explained editorial team.
Please note: this page is educational only — it is not medical advice, and it does not speculate about anyone’s health beyond reliable public reporting. For questions about your own health, talk with your healthcare team.
The indication, word for word
On March 13, 2017, the FDA approved ribociclib, sold as Kisqali.
The indication is narrow, and every clause of it matters. Ribociclib was cleared for use with an aromatase inhibitor. It was cleared as initial endocrine-based therapy. And it was cleared only for postmenopausal women with hormone receptor positive, HER2 negative advanced or metastatic breast cancer.
So: not alone, not after other hormone treatment has been tried, and not for every breast cancer.
The FDA gave the application priority review and breakthrough therapy designation. Both speed up the agency's own timeline. Neither lowers the evidence bar.
What the eligibility words mean
Hormone receptor positive means the cancer cells carry receptors for estrogen, progesterone, or both. NCI says about 80% of breast cancers are hormone receptor positive. Doctors find out by testing tumor tissue removed during surgery.
HER2 negative means the cells do not overproduce a growth-signaling protein called HER2. Cancers that do are treated with a different set of drugs.
Aromatase inhibitors block an enzyme the body uses to make estrogen. NCI names three: anastrozole, letrozole, and exemestane. They are used mainly after menopause. Before menopause the ovaries make too much aromatase for the drugs to shut down.
Ribociclib itself is a CDK4/6 inhibitor. CDK4 and CDK6 are enzymes that push a cell past a checkpoint and into division. Blocking them stalls that cycle. The drug works alongside hormone therapy, not instead of it. That is why the approval covers a pair of drugs and not one.
Our overview of targeted therapy covers this class of drug more broadly.
The trial
Approval rested on MONALEESA-2, a randomized, double-blind, placebo-controlled international trial.
It enrolled 668 postmenopausal women. All had hormone receptor positive, HER2 negative advanced or metastatic breast cancer. None had been treated before for advanced disease. Half, 334 women, got ribociclib plus letrozole. The other 334 got placebo plus letrozole.
Ribociclib or placebo was taken by mouth once a day for 21 days, then 7 days off. Letrozole 2.5 mg was taken every day of the 28-day cycle. Treatment went on until the disease grew or the side effects became too much. Those were the trial amounts. Your prescription and your clinic calendar are what to work from.
A planned interim analysis showed longer progression-free survival in the ribociclib group. That measure is the time before the cancer grew again. The hazard ratio was 0.556, with a 95% confidence interval of 0.429 to 0.720.
A hazard ratio of 0.556 means one thing. Over the period measured, the rate of progression events in the ribociclib group was a little over half the rate in the placebo group.
What taking it involves
The starting dose is 600 mg by mouth once a day. That is three 200 mg tablets, with or without food. They are taken for 21 days in a row, then 7 days off.
Read that as the starting point on the label. Your oncologist decides your amount and will change it if your blood counts or heart tracing call for it.
Side effects reported by a fifth or more of people were neutropenia, nausea, fatigue, diarrhea, leukopenia, hair loss, vomiting, constipation, headache, and back pain. Neutropenia and leukopenia both mean low white blood cell counts. That raises the risk of infection.
The most common severe reactions were graded 3 or 4 and seen in more than 2% of people. They were neutropenia, leukopenia, abnormal liver tests, lymphopenia, and vomiting.
The FDA also flagged a heart issue. Ribociclib lengthens the QT interval, a measure of the heart's electrical recovery. The higher the drug level in the blood, the greater the effect. The label carries warnings and monitoring steps for it.
When to get checked
Screening is a separate matter from treatment. For people at average risk, the US Preventive Services Task Force advises a screening mammogram every 2 years between ages 40 and 74. Our guide to mammograms covers what that involves.
Most breast changes are not cancer. Even so, NCI says to check with a doctor about:
- A lump in or near the breast, or under the arm.
- A thick or firm area in the same places.
- A change in the size or shape of a breast.
- Fluid or discharge from the nipple that is not breast milk.
- A nipple that changes shape, points a new way, or flattens.
- Scaly or swollen skin on the breast, nipple, or areola.
- Redness or darkening of that skin, or itching or tingling.
- General swelling with no lump, a skin rash, or dimples and puckering.
Anyone taking ribociclib should also report a fever right away. Low white blood cell counts make an ordinary infection more dangerous.
The survival picture
About 321,910 new female breast cancer diagnoses and 42,140 deaths are projected in the United States for 2026. Those projections are the American Cancer Society's, republished by SEER, NCI's cancer surveillance program. Five-year relative survival across all stages was 91.9% for people diagnosed from 2016 through 2022.
Stage dominates that number. Over the same 2016 to 2022 period, SEER records 64% found while local, at 100.0%. Twenty-seven percent are found in nearby lymph nodes, at 87.5%. Six percent are found after spread to distant organs, at 33.8%. That last group is the one this approval was written for.
These are averages across a large population diagnosed in past years. They do not predict one person's course.
What this approval cannot tell you
The MONALEESA-2 result reported at approval was progression-free survival, not overall survival. Delaying growth on a scan and living longer are different measures. Only the first was in hand in March 2017.
The 2017 indication also left out several groups. It did not cover premenopausal women. It did not cover hormone receptor negative or HER2 positive disease. And it did not cover use after other endocrine therapy had been tried. Labels change over time, and the current prescribing information governs eligibility now.
Finally, a hazard ratio describes a trial population. Whether this pairing fits one person depends on their tumor's receptor status and on their heart and liver health. That is a conversation with an oncologist.
Sources
- FDA: Ribociclib (Kisqali) approval information
- NCI: Hormone Therapy for Breast Cancer
- NCI: Mammograms fact sheet
- NCI: Signs and Symptoms of Breast Cancer
- NCI SEER Cancer Stat Facts: Female Breast Cancer
How this article was prepared
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Put the story in context
Prevention, possible warning signs, screening, and diagnosis
This story relates to Breast cancer. The information below is general: it does not reveal anything else about a public person’s health, and not every point applies to every cancer. Personal advice depends on age, symptoms, family history, exposures, and medical history.
Prevention and risk reduction
Not every cancer can be prevented. Avoiding tobacco, protecting skin from ultraviolet radiation, limiting alcohol, staying active, and receiving recommended HPV or hepatitis B vaccination can lower the risk of certain cancers. A risk factor is not a prediction or a cause in one individual.
Symptoms and possible early signs
Possible signs vary and are often caused by conditions other than cancer. Changes worth discussing include a new lump, unexplained bleeding or weight loss, a persistent cough, lasting bowel or bladder changes, a changing skin spot, or symptoms that persist or worsen. Some early cancers cause no symptoms.
Screening and early detection
Screening looks for certain cancers before symptoms begin. Recommended tests exist only for some cancers and depend on age and risk. Screening can have benefits and harms; it is not the same as evaluating a new symptom, and there is no single routine scan or blood test that reliably screens for every cancer.
How cancer is diagnosed
Diagnosis may involve a history and exam, imaging, laboratory tests, and often a biopsy. Pathology can identify the cancer type and may test biomarkers that guide treatment. Symptoms, screening results, tumor markers, or online stories alone cannot confirm cancer.
Learn about this story’s cancer topic
A public story may encourage questions, but it should not be used to estimate your risk or choose testing. Contact a healthcare professional about a persistent or concerning change. Seek urgent care for severe or rapidly worsening symptoms.