Targeted therapies for CML
The main treatment for CML is with drugs known as targeted therapies. These work by ‘targeting’ specific proteins in the leukaemia cells.
There are different types of targeted therapy drugs. The type used in CML is called a tyrosine kinase (TK) inhibitor.
These drugs switch off (inhibit) the effects of the abnormal gene (BCR-ABL). This means that the leukaemia cells, or blast cells, will mature correctly and die.
The three TK inhibitor drugs currently used are imatinib (Glivec®), dasatinib (Sprycel®) and nilotinib (Tasigna®).
Newer drugs are also being developed.
Imatinib is the main targeted therapy used to treat CML. It can be used in the chronic phase and may also be used in the accelerated or blast crisis phases if it hasn’t been used before.
The National Institute for Health and Clinical Excellence (NICE), which gives guidance to doctors in England and Wales, has recommended imatinib as the first treatment for CML in the chronic phase. NICE also recommends that imatinib is considered for people in the accelerated or blast phases.
The Scottish Medicines Consortium (SMC), a similar organisation to NICE for the NHS in Scotland, has also recommended the use of imatinib in all phases of CML.
Imatinib is a tablet. You take it every day for as long as it’s working to control the leukaemia.
Dasatinib (Sprycel®) and nilotinib (Tasigna®)
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Dasatinib and nilotinib are newer types of TK inhibitors. They are used to treat newly diagnosed CML in the chronic or accelerated phases. Dasatinib is also used in the blast phase. These drugs may help people who can’t take imatinib because of severe side effects or because it isn’t working to control their CML.
Dasatinib and nilotinib are tablets. They are taken for as long as they are effective.
Dasatinib and nilotinib aren’t widely available across the UK. NICE has recommended nilotinib as a possible treatment on the NHS in England and Wales when imatinib is either no longer working or has severe side effects. NICE has not recommended the use of dasatinib.
The SMC recommends that both dasatinib and nilotinib should be available in Scotland for people who have CML in the chronic phase. Its guidance states that nilotinib should be an option for all people with newly diagnosed CML, but that dasatinib should only be available when imatinib isn’t working or it’s causing a lot of side effects.
We have information on what you can do if a treatment isn’t available.
Side effects of TK inhibitors
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These are usually mild and treatable. They are often more noticeable in the first four weeks of treatment and then begin to settle after this.
Side effects generally disappear when treatment is stopped, so if you have severe side effects your doctor may ask you to stop taking the drug for a few days. After a short break, you may be able to start taking it again without having the same problems. Occasionally, some people need to stop treatment because their side effects are too severe.
Always let your doctor know if you notice any new side effects or if your side effects get worse.
The side effects you may experience include the following:
Feeling sick (nausea)
This is usually mild. Your doctor may prescribe anti-sickness (anti-emetic) drugs to prevent or reduce this. Let them know if you still feel sick, as they can prescribe another anti-sickness drug that may work better for you.
This can usually be controlled with anti-diarrhoea medicine, but tell your doctor if it’s severe or continues. It’s important to drink plenty of fluids if you have diarrhoea.
Loss of appetite
A dietitian or specialist nurse at your hospital can give advice and tips on boosting your appetite, coping with eating difficulties and maintaining weight.
Let your doctor know if you have headaches, as they can advise you which painkillers to take.
Muscle, bone and joint pains
You may have muscle, joint or bone pain while having your treatment. Your doctor can prescribe painkillers to ease this.
This can affect different parts of your body. Most commonly, it causes swelling of the ankles or swelling around the eyes. Fluid retention often settles without treatment, but if it doesn’t, drugs that make you pass more urine (diuretics) can help to get rid of some of the fluid. A short course of steroids may also help.
Your skin may become dry and itchy or you may develop a mild skin rash. Making sure you drink enough fluids can help. Your doctor can also prescribe medicine or creams to help with this.
Tiredness and feeling weak
Tiredness is common but is usually mild. It’s important to give yourself plenty of time to rest.
Drinking plenty of fluids, eating a high-fibre diet and taking gentle exercise usually helps relieve constipation. Sometimes you may need to take medicines (laxatives) to stimulate your bowel. Your doctor can prescribe these.
Risk of infection
TK inhibitors can reduce the number of healthy white blood cells produced by the bone marrow, making you more prone to infection.
Contact your doctor straight away if:
your temperature goes above 38°C (100.4°F)
you suddenly feel unwell, even with a normal temperature.
You will have a blood test before each treatment to make sure your blood cells have recovered. Occasionally, your treatment may need to be delayed if the number of blood cells (blood count) is still low.
Bruising or bleeding
TK inhibitors can reduce the production of platelets, which help the blood to clot. Tell your doctor if you have any unexplained bruising or bleeding, such as nosebleeds, bleeding gums, blood spots or rashes on the skin. They will advise you about this and explain any precautions you should take.
Anaemia (low number of red blood cells)
You may become anaemic while having treatment with a TK inhibitor. This can make you feel tired and breathless. Tell your doctor or nurse if you have these symptoms. You may need to have a blood transfusions if the number of red blood cells becomes too low.
If your blood cell numbers fall too much, your doctor may stop your treatment for a few days to let them recover.
Or you may be prescribed injections of substances called growth factors. The growth factor G-CSF can stimulate your bone marrow to produce more healthy white blood cells, and erythropoietin can help with the production of red blood cells.
Contraception and fertility
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TK inhibitors are a newer type of drug, so there isn’t a lot of information about women becoming pregnant or men fathering children while taking them. There may be a slightly increased risk of damage to the developing baby, so it’s strongly recommended that you use contraception while being treated with a TK inhibitor.