How it is administered

Imatinib is taken by mouth as a tablet or oral solution. Tablets are available in 100 mg and 400 mg strengths, while the oral solution contains 80 mg per mL. It should always be taken with a meal and a large glass of water to help reduce stomach upset. Doses are typically taken once daily, but higher doses (such as 800 mg) are split into two doses per day. For patients who have difficulty swallowing tablets, they can be dispersed in water or apple juice. For the oral solution, use an accurate measuring device (not a household spoon) to ensure the correct dose.

How it works

Imatinib is a type of medication called a tyrosine kinase inhibitor. It works by blocking certain proteins (called tyrosine kinases) that signal cancer cells to grow. In aggressive systemic mastocytosis (ASM), imatinib targets the abnormal c-Kit protein (except when the D816V mutation is present), which is involved in the growth and survival of mast cells. By blocking this protein, imatinib can slow or stop the growth of abnormal mast cells.

Imatinib also inhibits other proteins, such as BCR-ABL (seen in chronic myeloid leukemia), PDGFR, and others, which are involved in the growth of various blood cancers. By targeting these proteins, imatinib helps control the overproduction of abnormal blood cells, reduces symptoms, and can improve survival in people with certain blood cancers, including ASM without the D816V mutation or with unknown mutation status.

Who Should take it

Imatinib is indicated for adults with aggressive systemic mastocytosis (ASM) who do not have the D816V c-Kit mutation or whose c-Kit mutation status is unknown. It may also be considered for patients with ASM not responding to other therapies if their mutation status is not available.

Imatinib is also used for other blood cancers, such as chronic myeloid leukemia (CML), Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL), myelodysplastic/myeloproliferative diseases with PDGFR gene rearrangements, hypereosinophilic syndrome, and certain solid tumors. For ASM, it is most effective in patients without the D816V mutation or with mutations in the juxtamembrane region of c-Kit. Your doctor may recommend genetic testing before starting imatinib to determine if it is likely to be effective.

Who should not take it

Imatinib should not be used in patients with ASM who have the D816V c-Kit mutation, as studies show it is not effective in this group. It is also not recommended for less aggressive forms of systemic mastocytosis, such as indolent or smoldering SM, mast cell leukemia, or mast cell sarcoma.

Imatinib is not recommended for use during pregnancy due to the risk of harm to the unborn baby. Women of childbearing potential should use effective contraception during treatment and for 14 days after stopping imatinib. People with severe liver or kidney impairment may need dose adjustments or should avoid imatinib if risks outweigh benefits. Always inform your doctor about all medical conditions and medications before starting imatinib.

Commonly used with

Imatinib is sometimes used in combination with chemotherapy for certain types of leukemia (such as Ph+ ALL in children). For ASM, it is typically used alone. Supportive medications, such as anti-nausea drugs or diuretics (for fluid retention), may be prescribed alongside imatinib to help manage side effects. Your healthcare team will discuss any additional medications you may need during treatment.

Commonly tested with

Imatinib is often studied with other tyrosine kinase inhibitors (such as nilotinib) in clinical trials for blood cancers. In pediatric ALL, it is tested in combination with multi-agent chemotherapy. For ASM, studies have compared imatinib’s effectiveness in patients with different c-Kit mutations, and sometimes with corticosteroids in cases of high eosinophil counts. Your doctor may order regular blood tests and genetic tests to monitor your response and check for mutations that affect treatment.