A CDK4/6 inhibitor for advanced breast cancer
Ribociclib
A targeted cancer tablet taken with hormone therapy to slow the growth of certain advanced breast cancers.
What is Ribociclib?
Ribociclib is a specialist cancer medicine used to treat certain types of advanced or secondary breast cancer that are hormone-receptor positive and HER2 negative. It is a CDK4/6 inhibitor, meaning it blocks proteins cancer cells use to divide, and it is taken by mouth alongside hormone therapy. A key safety point is that it can affect the heart's electrical rhythm (the QT interval), so heart tracing tests (ECGs) and blood tests are done before and during treatment. It also commonly lowers white blood cells, raising infection risk, and can affect the liver, so blood tests are needed. It can harm a developing baby, so reliable contraception is important.
Education and reference only. This is a plain-language guide to Ribociclib — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Ribociclib is a targeted cancer medicine used to treat advanced or secondary breast cancer that is hormone-receptor positive and HER2 negative. It belongs to the CDK4/6 inhibitor group, which interrupts the signals cancer cells use to grow and divide. It is taken by mouth as a tablet, in cycles, and is always combined with hormone therapy rather than used on its own. It is prescribed and closely supervised by a cancer specialist team, who check the heart's rhythm, blood counts and liver function during treatment.
How it works
Cancer cells multiply by repeatedly going through a cycle of division, helped by proteins called CDK4 and CDK6. Ribociclib blocks these proteins, stalling the cycle so the cancer cells stop dividing. Because the breast cancers it treats are also driven by hormones, it is paired with hormone therapy so the two work together for longer-lasting control. The same effect on dividing cells can lower white blood cells, which is why blood counts are monitored, and ribociclib can also affect the heart's electrical rhythm and the liver, which is why ECGs and liver tests are done.
Company & origin
Originated / developed by: Specialist manufacturer.
A specialist cancer medicine used in the UK to treat certain types of advanced or secondary breast cancer, taken alongside hormone therapy.
Practical use
How to take Ribociclib
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it by mouth once a day in the cycles your team sets, usually with a break each month to let blood counts recover.
- Swallow the tablets whole with water; take your hormone therapy as prescribed too, as it is used alongside it.
- Keep all your heart tracing (ECG), blood count and liver blood test appointments.
- Report a fever or other signs of infection, or yellowing of the skin or eyes, promptly.
- Tell your team about any heart-rhythm problems or medicines that affect it, and use reliable contraception during treatment.
Weighing it up
Advantages & disadvantages of Ribociclib
Advantages
- Can slow the growth of certain advanced breast cancers and help control them for longer when added to hormone therapy.
- Taken by mouth at home rather than as an infusion.
- A targeted treatment that works on the cancer's growth signals.
Disadvantages
- Can affect the heart's electrical rhythm (the QT interval), needing ECGs and blood tests.
- Commonly lowers white blood cells, raising the risk of infection.
- Can affect the liver and can harm a developing baby.
Practical use
Good to know
An important and distinctive point with ribociclib is that it can affect the heart's electrical rhythm, lengthening what is called the QT interval; because of this you will have heart tracing tests (ECGs) and blood tests, including salts such as potassium and magnesium, before starting and during the early part of treatment, and other medicines that affect the heart rhythm are reviewed. Like other medicines in its group, it commonly lowers white blood cells, raising the risk of infection, so report a fever or other signs of infection promptly and keep up with blood tests. It can also affect the liver, so liver blood tests are monitored and any yellowing of the skin or eyes should be reported. It is taken in cycles with a break each month. It can harm a developing baby, so reliable contraception is needed during treatment and for a time afterwards.
Who should not take it / use with caution
- People who have had a serious allergic reaction to ribociclib should not take it.
- It is used with caution, or avoided, in people with certain heart-rhythm problems or those on medicines that lengthen the QT interval.
- It is not used in pregnancy because it can harm a developing baby, and breastfeeding is avoided during treatment.
- It is used with caution in people with significant liver problems or a current serious infection, under specialist guidance.
Monitoring
- Heart tracing tests (ECGs) and salt blood tests before and during the early part of treatment.
- Regular blood counts and liver blood tests.
- Watching for signs of infection and reviewing how well the cancer is responding alongside hormone therapy.
Side effects
- A drop in white blood cells (neutropenia), which raises the risk of infection.
- Changes in the heart's rhythm (the QT interval) and in liver blood tests.
- Nausea, tiredness, diarrhoea, hair thinning or headache.
- Rarely but seriously, severe liver problems or serious skin reactions, which need urgent medical attention.
Key interactions
- Some medicines and grapefruit can raise ribociclib levels, increasing side effects, so tell your team everything you take.
- Other medicines can lower its levels and make it less effective, so these are reviewed by your team.
- Medicines that affect the heart's QT interval need careful review alongside ribociclib.
Available as: Tablets taken by mouth.
Answers
Ribociclib: frequently asked questions
What is ribociclib used for?
It is used to treat certain advanced or secondary breast cancers that are hormone-receptor positive and HER2 negative, taken by mouth alongside hormone therapy.
Why do I need heart tracing tests?
Ribociclib can affect the heart's electrical rhythm (the QT interval), so ECGs and blood tests before and during treatment help keep this safe.
Why are blood counts checked?
It commonly lowers white blood cells, which fight infection, so blood tests check these counts and guide the dose; report a fever promptly.
Why is it taken with hormone therapy?
The breast cancers it treats are fuelled by hormones, so ribociclib is combined with hormone therapy to control the cancer more effectively than either alone.
Is it safe in pregnancy?
No. Ribociclib can harm a developing baby, so reliable contraception is needed during treatment and for a time afterwards.
Authoritative sources
- BNF
- NICE CKS
Building a medicines information resource?
We create evidence-led, dose-free drug and formulary references for teams.