A HER2-targeting tablet for HER2-positive breast cancer
Tucatinib
A targeted cancer tablet for HER2-positive breast cancer, used together with other cancer medicines.
What is Tucatinib?
Tucatinib is a specialist targeted cancer medicine used to treat HER2-positive breast cancer, a type where the cancer cells carry extra amounts of a protein called HER2 that drives growth. It is a tablet taken by mouth, usually combined with other cancer medicines. The most common problems are diarrhoea, which can be troublesome, and effects on the liver, so it needs monitoring. It can harm an unborn baby, so effective contraception is essential. It is prescribed and supervised by a cancer specialist.
Education and reference only. This is a plain-language guide to Tucatinib — 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
Tucatinib is a targeted cancer medicine known as a HER2 tyrosine kinase inhibitor. It is used to treat HER2-positive breast cancer, a type in which the cancer cells make too much of a protein called HER2 that fuels their growth, including when the cancer has spread. It is taken by mouth as a tablet and is usually given together with other cancer medicines as part of a treatment plan. It is only used when testing confirms the cancer is HER2-positive, and it is prescribed and supervised by a cancer specialist.
How it works
HER2-positive breast cancers carry extra amounts of the HER2 protein, which sends signals telling the cancer cells to grow and divide. Tucatinib blocks the part of HER2 that passes on this growth signal inside the cell, so the signal is switched down and the cancer is slowed. Because it works in a focused way on HER2, it is often combined with other HER2-targeting medicines and chemotherapy to attack the cancer in more than one way. It is taken every day to keep the signal dampened down.
Company & origin
Originated / developed by: Specialist manufacturer.
A specialist cancer medicine used in the UK to treat HER2-positive breast cancer, usually together with other cancer medicines.
Practical use
How to take Tucatinib
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it by mouth twice a day, at about the same times, as part of the treatment plan your team gives you.
- Start anti-diarrhoea treatment as advised and drink plenty of fluids; tell your team about frequent or severe diarrhoea.
- Use effective contraception during treatment and for the time afterwards your team advises, as it can harm an unborn baby.
- Report any yellowing of the skin or eyes, dark urine, or unusual tiredness, as these can signal liver problems.
- Give your team a full list of your other medicines, as tucatinib interacts with several of them.
Weighing it up
Advantages & disadvantages of Tucatinib
Advantages
- An effective targeted treatment for HER2-positive breast cancer, including when it has spread.
- Taken at home as a tablet rather than as a drip.
- Works alongside other cancer medicines to attack the cancer in more than one way.
Disadvantages
- Commonly causes diarrhoea, which can be troublesome and may need active management.
- Can affect the liver, so regular blood tests are needed.
- Can harm an unborn baby and interacts with several other medicines.
Practical use
Good to know
The most common and important day-to-day side effect is diarrhoea, which can be frequent or severe; your team will advise on anti-diarrhoea medicine, staying hydrated, and when to call for help, as bad diarrhoea sometimes means the dose needs adjusting. The other key safety point is that tucatinib can affect the liver, so blood tests are done regularly and any yellowing of the skin or eyes, dark urine or unusual tiredness should be reported. Because it can harm an unborn baby, effective contraception is essential during treatment and for a time afterwards, and it should not be used in pregnancy. It also interacts with several other medicines, so a full medicines list is important. It is taken with other cancer medicines as part of a planned course under specialist care.
Who should not take it / use with caution
- People who have had a serious allergic reaction to tucatinib should not take it.
- It should not be used in pregnancy, as it can harm an unborn baby.
- It is used with care in people with liver problems, under specialist supervision.
Monitoring
- Regular liver blood tests during treatment.
- Watching for and managing diarrhoea, including hydration.
- Reviewing how well the cancer responds and checking blood counts.
Side effects
- Diarrhoea, which can be frequent or severe and may need treatment.
- Changes in liver blood tests, sometimes with yellowing of the skin or eyes.
- Nausea, tiredness, sore mouth, rash or a fall in blood counts.
Key interactions
- It can raise or lower the levels of several other medicines, so a full medicines list is important.
- Some other medicines, supplements and grapefruit can affect how tucatinib works, so check before starting anything new.
- It is used together with other planned cancer medicines under specialist guidance.
Available as: Tablets taken by mouth.
Answers
Tucatinib: frequently asked questions
What is tucatinib used for?
It is a targeted medicine for HER2-positive breast cancer, a type where the cancer cells carry extra HER2 protein that drives growth, usually given with other cancer medicines.
Why does it cause diarrhoea?
Diarrhoea is the most common side effect of tucatinib; your team will advise on anti-diarrhoea medicine and staying hydrated, and on when the dose may need adjusting.
Does it affect the liver?
It can affect the liver, so regular blood tests are done; report any yellowing of the skin or eyes, dark urine or unusual tiredness.
Can I take it during pregnancy?
No. Tucatinib can harm an unborn baby, so effective contraception is essential during treatment and for the time afterwards your team advises.
Why does my team need my full medicines list?
Tucatinib interacts with several other medicines, affecting their levels or being affected by them, so a complete list helps keep treatment safe.
Authoritative sources
- BNF
- NICE CKS
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