A JAK inhibitor tablet for myelofibrosis with anaemia
Momelotinib
A daily tablet used to treat myelofibrosis, especially helpful in people who also have anaemia.
What is Momelotinib?
Momelotinib is a specialist medicine used to treat myelofibrosis, a bone-marrow condition that can cause an enlarged spleen, troublesome symptoms and anaemia. It belongs to a group called JAK inhibitors, taken as a daily tablet, and a particular advantage is that it can help anaemia as well as easing spleen size and symptoms. Because it dampens the bone marrow and immune system, it can lower blood counts and increase the risk of infections, and it can reactivate hidden hepatitis B. It is prescribed and monitored closely by a blood specialist team.
Education and reference only. This is a plain-language guide to Momelotinib — 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
Momelotinib is a targeted treatment for myelofibrosis, a condition in which the bone marrow becomes scarred and cannot make blood cells properly. This often leads to an enlarged spleen, symptoms such as tiredness, night sweats and itching, and anaemia (a low level of red blood cells). It is one of a group of medicines called JAK inhibitors, which calm the overactive signalling that drives the condition. It is taken by mouth as a daily tablet and is particularly useful for people whose myelofibrosis is accompanied by anaemia. It is prescribed and supervised by a blood (haematology) specialist team.
How it works
In myelofibrosis, signals through pathways known as JAK pathways become overactive, driving the abnormal bone-marrow activity, the enlarged spleen and the troublesome symptoms. Momelotinib blocks these signals, which can shrink the spleen and ease symptoms. It also affects a separate pathway involved in how the body handles iron and red-blood-cell production, which is thought to be why it can improve anaemia and reduce the need for blood transfusions in some people. Because it dampens these signals and the immune response, it is taken daily with regular blood tests to balance benefit against the risk of low counts and infection.
Company & origin
Originated / developed by: Specialist manufacturer.
A specialist medicine used in the UK to treat myelofibrosis, particularly in people who also have anaemia.
Practical use
How to take Momelotinib
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take the tablet by mouth once a day as prescribed, with or without food, at about the same time each day.
- Attend all your blood tests, as the medicine can lower blood counts, particularly platelets.
- Report any signs of infection such as fever, chills or feeling generally unwell promptly.
- Tell your team about any unusual bruising or bleeding, or any tingling or numbness in your hands or feet.
- Do not stop taking it suddenly without specialist advice, as symptoms can rebound.
Weighing it up
Advantages & disadvantages of Momelotinib
Advantages
- Eases the enlarged spleen and symptoms of myelofibrosis while often improving anaemia.
- May reduce the need for blood transfusions in some people with anaemia.
- Taken as a convenient daily tablet under specialist care.
Disadvantages
- Can still lower blood counts, particularly platelets, needing regular blood tests.
- Dampens the immune system, increasing the risk of infections.
- Can reactivate hidden hepatitis B and can cause tingling or numbness in the hands and feet.
Practical use
Good to know
A useful feature of momelotinib is that, unlike some similar medicines, it may improve anaemia rather than worsen it, so it is often chosen for people with myelofibrosis who also have low red blood cells. Even so, it can still lower blood counts, particularly platelets, so regular blood tests are essential and any unusual bruising or bleeding should be reported. Because it dampens the immune system, it can make infections more likely or more serious, so signs such as fever, chills or feeling generally unwell need prompt attention. An important safety check is for hepatitis B: the virus can reactivate during treatment, so you are tested beforehand and monitored. It can also cause tingling or numbness in the hands and feet and dizziness. It is taken every day under specialist supervision, and should not be stopped suddenly without advice.
Who should not take it / use with caution
- People who have had a serious allergic reaction to momelotinib should not take it.
- It is used with particular care in people with active or untreated infections, including hepatitis B, under specialist guidance.
- It is generally avoided in pregnancy and breastfeeding unless a specialist judges it necessary.
Monitoring
- Regular blood counts, especially platelets, before and during treatment.
- Hepatitis B testing before starting and watching for reactivation during treatment.
- Watching for signs of infection and reviewing spleen size, symptoms and anaemia over time.
Side effects
- Low blood counts, particularly low platelets, which can cause bruising or bleeding.
- Infections, which can be more frequent or more serious, and tiredness or dizziness.
- Diarrhoea, nausea and tingling or numbness in the hands and feet.
- Less commonly, reactivation of hepatitis B and changes in liver blood tests.
Key interactions
- Other medicines that lower blood counts or weaken the immune system can add to these effects.
- Some medicines can change momelotinib levels, so tell your team about everything you take.
- Live vaccines are generally avoided while taking it, as the immune system is dampened.
Available as: Tablets taken by mouth.
Answers
Momelotinib: frequently asked questions
What is momelotinib used for?
It is used to treat myelofibrosis, a bone-marrow condition, easing the enlarged spleen and symptoms and being particularly helpful for people who also have anaemia.
How is it different from other JAK inhibitors?
A key feature is that it may improve anaemia rather than worsen it, so it is often chosen for people with myelofibrosis who have low red blood cells.
Why do I need regular blood tests?
It can lower blood counts, particularly platelets, so regular blood tests are used and any unusual bruising or bleeding should be reported.
Why am I tested for hepatitis B?
Hepatitis B can reactivate during treatment with this kind of medicine, so you are tested beforehand and monitored while taking it.
Can I stop it if I feel better?
No. Do not stop it suddenly without specialist advice, as symptoms can rebound; any changes should be guided by your team.
The wider class
About JAK inhibitor (myelofibrosis)
Momelotinib belongs to the jak inhibitor (myelofibrosis) class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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