Targeted therapy is the use of medicines that act on parts of cancer cells that make them different from normal cells. They target proteins that control how cancer cells grow, divide, and spread. They can damage the cancer cells without affecting most normal, healthy cells. These medicines are different from standard chemotherapy medicines. They often have less severe side effects.

The only type of targeted medicines used to treat chronic myeloid leukemia (CML) are called tyrosine kinase inhibitors (TKIs). TKIs block a protein called tyrosine kinase. This protein is made by an abnormal gene in CML cells. The abnormal tyrosine kinase makes CML cells reproduce uncontrollably.

Some of the TKIs used to treat CML include:

• Imatinib.
• Dasatinib.
• Nilotinib.
• Bosutinib.
• Ponatinib.
• Asciminib.

TKIs are the first treatment used for CML. These medicines work best when CML is in the chronic phase. They may also help in more advanced CML (accelerated or blast phases). TKIs often work well at keeping the CML under control for long periods of time. It's not yet clear if they can cure the leukemia. Your doctor will keep track of your CML with blood tests or other tests during treatment. If one of these medicines doesn't work or stops working over time, the dose might be increased or another TKI may be used.

The medicines are taken as pills or capsules, once or twice a day. Take them exactly as your health care team tells you. Taking the medicines as directed gives them the best chance to treat your leukemia. It's likely you'll need to take these pills for a very long time to keep the CML under control.

Tell your doctor about all other medicines you take. This includes over-the-counter medicines and supplements, such as herbs and vitamins. Some medicines and supplements can change the way targeted therapy medicines work.

The targeted therapy medicines may also interact with some foods such as grapefruits and pomegranates. Ask your health care team if you need to stay away from certain foods.

During treatment, blood tests will be done. This is to check for a decrease in your white or red blood cells or platelet levels. They'll be done more often at the start of treatment.

Side effects of TKIs depend on the medicine used, and may include:

• Bloating or swelling from fluid retention.
• Diarrhea.
• Itchy skin rashes.
• Joint or muscle pain.
• Nausea or vomiting.
• Severe tiredness (fatigue).
• Belly (abdominal) pain.
• Lower blood cell counts, which can increase your risk of infections, bleeding, and bruising.

Side effects from these medicines tend to be mild. But in some cases they can cause more severe side effects, such as:

• Fluid buildup around the heart or lungs, which can cause trouble breathing.
• Changes in heart rhythm.
• High blood pressure.
• Liver damage.

Ponatinib can also cause serious blood clots. This medicine may be used only if none of the other TKIs are working, or if the leukemia cells have a certain gene change (mutation).

It's important to know which medicines you're taking. Write down their names. Ask your health care team how they work, how to take them, and what side effects they might have.

Talk with your doctor about what side effects to watch out for, and when you should report them to your health care team. Make sure you know what number to call with problems or questions, even after office hours, on holidays, and weekends.

It may be helpful to keep a diary of your side effects. Write down any physical, thinking, and emotional changes. A written list will make it easier for you to remember your questions when you go to your appointments. It'll also make it easier for you to work with your medical team to make a plan to manage your side effects.