Tyrosine kinase inhibitors (TKIs) are a type of targeted therapy. TKIs come as pills, taken orally. A targeted therapy identifies and attacks specific types of cancer cells while causing less damage to normal cells. In CML, TKIs target the abnormal BCR-ABL protein that causes uncontrolled CML cell growth and block its function, causing the CML cells to die.
Three TKI drugs are approved as initial therapy (first-line treatment) for chronic phase CML. These drugs are
- Imatinib mesylate (Gleevec®)
- Dasatinib (Sprycel®)
- Nilotinib (Tasigna®).
“Initial” treatment is the first therapy given for a disease. If the first treatment does not work because of intolerance (intolerable side effects) to a particular drug or drug resistance (CML is not responding to the drug) during therapy, a second treatment option is tried. If both the initial treatment and the subsequent treatment (second-line) fail to work, a third treatment option (third-line treatment) can be offered to the patient.
In the case of resistance to and/or intolerance to second-line treatments, other TKI options for treatment include
- Bosutinib (Bosulif®)
- Ponatinib (Iclusig®).
Patients with a history of cardiac disease or peripheral vascular disease need to be monitored carefully and frequently during TKI treatment. It is rare, but some patients who were treated with TKIs develop serious cardiac side effects including congestive heart failure and QT interval prolongation (changes in heartbeat rhythm). Many patients who develop adverse cardiac effects also have other health problems and risk factors including older age and a medical history of cardiac disease.
For information about the drugs mentioned on this page, visit Drug Listings.
Certain drugs, herbal supplements and even foods can affect the way TKIs work in the body. Corticosteroids, anti-seizure medication, antacids, and the herbal supplement St. John’s Wort can make some TKIs less effective. On the other hand, certain antibiotics and antifungal medication and grapefruit products may increase the levels of TKIs in the blood to high, unsafe levels.
TKIs can have serious or even deadly interactions with other prescription medications, over-the-counter medications, supplements and even certain foods. Patients should always provide their doctors with a list of any medications, herbal supplements and vitamins that they are taking to be certain that it is safe to take the products with their TKIs. And it is important to ask the doctor about any foods that should be avoided.
It is important for patients to take their TKIs as prescribed by their doctor. Adherence to an oral therapy means that a patient
- Takes the correct dose of medication
- Takes the medication at the correct time
- Never misses a dose
- Never takes an extra dose
- Does not take a dose with foods, liquids or other medications that are not allowed
In most patients, TKIs can control CML. Patients should not skip doses to try to reduce the side effects of the medication. Patients should tell their doctors about any side effects that they are experiencing. Doctors can provide supportive treatment to help patients manage these side effects.
Patients must take their medication as prescribed to get the best response. Poor adherence to the medication regimen is the main reason for inadequate response to the prescribed treatment. Patients should not stop taking their medication, nor should they take less than the amount prescribed, unless they are following their doctors’ instructions. Taking less than the amount prescribed can affect how well the medication works and may result in unfavorable treatment outcomes.