A JAK2 inhibitor for myelofibrosis
Fedratinib
A targeted capsule used to treat myelofibrosis, helping to shrink an enlarged spleen and ease symptoms.
What is Fedratinib?
Fedratinib is a specialist targeted treatment for myelofibrosis, a bone-marrow condition that often causes an enlarged spleen, tiredness, night sweats and weight loss. It is a capsule that blocks an overactive signal called JAK2, which helps shrink the spleen and ease symptoms. Its most important risk is a serious and sometimes fatal brain condition (encephalopathy), including Wernicke's encephalopathy linked to low thiamine (vitamin B1), so thiamine is checked and replaced and any confusion, memory or balance problems must be reported urgently. It also lowers blood counts and commonly causes gut upset.
Education and reference only. This is a plain-language guide to Fedratinib — 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
Fedratinib is a targeted medicine used to treat myelofibrosis, a long-term condition in which the bone marrow becomes scarred and cannot make blood cells properly, often leading to an enlarged spleen and symptoms such as tiredness, night sweats, itching and weight loss. It is taken by mouth as a capsule and works by blocking an overactive signalling protein. It is prescribed and supervised by a specialist haematology team, who check thiamine levels and blood counts closely because of its particular and serious side effects.
How it works
In myelofibrosis, a signalling protein called JAK2 is overactive, driving the abnormal blood-cell production, the scarring of the marrow and many of the troublesome symptoms. Fedratinib blocks JAK2, calming this overactive signal, which helps shrink the enlarged spleen and reduce symptoms such as night sweats and tiredness. It does not cure the condition but can improve how a person feels day to day. Because it affects how the body handles vitamin B1 (thiamine) and how the marrow works, low thiamine and falling blood counts are key risks the team monitors.
Company & origin
Originated / developed by: Specialist manufacturer.
A specialist targeted treatment used for myelofibrosis, a bone-marrow condition that causes an enlarged spleen and troublesome symptoms.
Practical use
How to take Fedratinib
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take the capsule by mouth as prescribed, swallowing it whole; taking it with a high-fat meal can help reduce nausea.
- Have your thiamine (vitamin B1) checked before and during treatment, and take any thiamine replacement your team prescribes.
- Report any confusion, memory problems, unsteadiness or difficulty walking straight away, as these can signal a serious brain condition.
- Use the anti-sickness and anti-diarrhoea medicines your team provides, and report severe or lasting gut upset.
- Use reliable contraception during treatment and for the time afterwards that your team advises, and report any possible pregnancy promptly.
Weighing it up
Advantages & disadvantages of Fedratinib
Advantages
- A targeted treatment that can shrink an enlarged spleen and ease myelofibrosis symptoms such as night sweats and tiredness.
- An option for people who cannot take, or no longer respond to, other JAK inhibitors.
- Taken as a capsule at home rather than by injection or infusion.
Disadvantages
- Can cause a serious and sometimes fatal brain condition (encephalopathy), linked to low thiamine.
- Lowers blood counts, raising the risk of infection, bleeding and anaemia.
- Very commonly causes nausea, vomiting and diarrhoea, and can harm an unborn baby.
Practical use
Good to know
The single most important safety point with fedratinib is the risk of a serious brain condition called encephalopathy, including Wernicke's encephalopathy, which is linked to low levels of vitamin B1 (thiamine) and can be fatal if not treated quickly. Thiamine is checked before and during treatment and corrected if low, and treatment is not started if levels are low. Any confusion, memory problems, unsteadiness, difficulty walking or unusual eye movements must be reported urgently, as this is a medical emergency. Fedratinib also lowers blood counts, raising the risk of infection, bleeding and anaemia, and very commonly causes nausea, vomiting and diarrhoea, for which anti-sickness and anti-diarrhoea medicines are often given. It can also affect liver and kidney tests. Because it can harm an unborn baby, reliable contraception is important during treatment and for a time afterwards.
Who should not take it / use with caution
- People who have had a serious allergic reaction to fedratinib should not take it.
- It is not started in people with low thiamine (vitamin B1) levels until these have been corrected.
- It is not used in pregnancy or while breastfeeding, and is used with care in liver or kidney problems, under specialist judgement.
Monitoring
- Checking thiamine (vitamin B1) levels before and during treatment and replacing if low.
- Regular blood counts and liver and kidney tests throughout treatment.
- Watching for any confusion, memory or balance problems and reviewing spleen size and symptoms.
Side effects
- A serious brain condition (encephalopathy), including Wernicke's, with confusion, memory or balance problems, needing urgent care.
- Low blood counts, raising the risk of infection, bleeding and anaemia.
- Nausea, vomiting and diarrhoea, which are very common.
- Changes in liver and kidney blood tests, and tiredness.
Key interactions
- Some medicines can raise or lower fedratinib levels, so tell your team about all your medicines.
- Other medicines that lower blood counts can add to the effect and are combined carefully.
- Avoid starting new medicines, including over-the-counter products, without checking with your team.
Available as: Capsules taken by mouth.
Answers
Fedratinib: frequently asked questions
What is fedratinib used for?
It is a targeted capsule used to treat myelofibrosis, helping to shrink an enlarged spleen and ease symptoms such as night sweats, tiredness and weight loss.
Why is my vitamin B1 checked?
Fedratinib can cause a serious brain condition linked to low vitamin B1 (thiamine), so levels are checked and corrected before and during treatment to reduce this risk.
What brain symptoms should I watch for?
Report any confusion, memory problems, unsteadiness, difficulty walking or unusual eye movements urgently, as these can be signs of a serious and sometimes fatal brain condition.
Why does it upset my stomach?
Nausea, vomiting and diarrhoea are very common; taking it with a high-fat meal and using the anti-sickness and anti-diarrhoea medicines your team provides can help.
Do I need contraception?
Yes. Because it can harm an unborn baby, reliable contraception is important during treatment and for a time afterwards, as your team advises.
The wider class
About JAK2 inhibitor (targeted therapy for myelofibrosis)
Fedratinib belongs to the jak2 inhibitor (targeted therapy for 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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