What is a tyrosine kinase inhibitor (TKI)?

If you have a type of acute lymphoblastic leukaemia (ALL) called Philadelphia positive ALL (Ph+ ALL), your treatment will include a drug called a tyrosine kinase inhibitor (TKI). Tyrosine kinase (TK) is a chemical messenger that tells cells when to develop and divide.

In Ph+ ALL, the leukaemia cells make high levels of tyrosine kinase. This makes the leukaemia cells grow and divide in an uncontrolled way. TKI drugs block (inhibit) how the TK signals work in leukaemia cells. This makes the cells die.


Imatinib is the most commonly used TKI drug. You take imatinib as tablets every day. You may take them:

  • with chemotherapy and other drugs as your first treatment for Ph+ ALL
  • as your main treatment if Ph+ ALL comes back (relapses).

Side effects of imatinib

Side effects of imatinib are usually mild and include:

  • feeling sick
  • diarrhoea
  • tiredness
  • leg aches or cramps
  • an itchy rash.

They are often more noticeable in the first 4 weeks of treatment. They then begin to get better.

Tell your nurse or doctor if you have any side effects. They can usually be treated.

Ponatinib is another TKI drug that is sometimes used if other treatments are not controlling Ph+ ALL.

About our information

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr Anne Parker, Consultant Haematologist.

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