Is Imatinib Chemotherapy? Pharmacist-Backed Answers to 6 Imatinib FAQs

Imatinib (Gleevec) is an oral targeted therapy medication. It’s used to treat cancers such as chronic myeloid leukemia (CML), acute lymphoblastic leukemia (ALL), and gastrointestinal stromal tumors (GIST) in adults. It's also used to treat certain types of CML and ALL in children and other blood disorders in adults.

Imatinib was FDA approved in the early 2000s. At the time of its approval, it was touted as a miracle drug to treat CML; it was able to specifically target CML cells while sparing healthy cells. Imatinib transformed the lives of people with CML and allowed them to live longer.

Imatinib isn’t actually a miracle drug, but it is effective overall. Imatinib works differently from chemotherapy and is often taken long term to prevent cancer from coming back. How long you take imatinib depends on the type of cancer being treated and possible side effects that can happen.

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Here, we’ll answer some of the most common questions about imatinib.

1. Is imatinib chemotherapy?

No, imatinib is not chemotherapy. It's a type of targeted therapy called a tyrosine kinase inhibitor (TKI). TKIs target and attack specific proteins on cancer cells. Targeting specific proteins in the body allows imatinib to slow cancer growth while sparing healthy cells. This strategic approach can help lessen side effects and may work better to fight cancer.

Traditional chemotherapy medications work by killing rapidly dividing cancer cells. But they can affect healthy cells, too. Because of this, traditional chemotherapy is often associated with more side effects than targeted therapy.

2. What is imatinib’s mechanism of action?

Imatinib is a TKI that works by blocking a specific tyrosine kinase: the BCR-ABL1 fusion gene. This is a protein that develops as a result of a genetic abnormality to two chromosomes in the body (chromosomes 9 and 22). This abnormality leads to uncontrolled cancer cell growth. By blocking BCR-ABL1, imatinib helps stop cancer cells from growing and multiplying uncontrollably.

Imatinib can also block the activity of a few other proteins, like KIT and PDGFRA, that are involved in the growth of GIST cancer cells. GIST is a rare cancer that starts in cells of the digestive tract.

Good to know: The BCR-ABL1 fusion gene is also known as the Philadelphia chromosome. The Philadelphia chromosome is commonly found in people with CML and some types of ALL.

3. How long does it take imatinib to work?

How long it takes for imatinib to work depends on the type of cancer being treated and how well you respond to imatinib. In general, it can take weeks to months to see its effects.

Imatinib can work relatively quickly in people who take it daily for CML. Many people have a hematologic response to treatment within 3 to 6 months. This means that the number of abnormal blood cells in the body returns to a normal range. A more significant lowering of abnormal blood cells — called a major molecular response  — can take around 12 to 18 months.

For GIST, imatinib can also work quickly to shrink tumor size and stop cancer from getting worse. Some people who take imatinib for GIST see effects within a few weeks. But the median time to see a response is about 3 months.

Not everyone who takes imatinib will have a response to treatment. Your oncologist should monitor your response to treatment with imatinib over time and adjust your treatment plan if necessary. This may include stopping imatinib altogether and trying something else.

4. How long do you need to take imatinib?

Many people take imatinib for a long time. In fact, some people take imatinib indefinitely or for several years — as long as it’s still working and they aren’t having intolerable side effects.

CML, for instance, is a chronic condition. It requires ongoing treatment to help prevent cancer from coming back. People with CML often take imatinib for multiple years.

For people with Philadelphia chromosome-positive (Ph+) ALL, a medication like imatinib is usually recommended throughout all stages of treatment. This includes upfront with induction chemotherapy (the first chemotherapy, which is used to kill as many ALL cells as possible), consolidation therapy, and maintenance therapy. 

These three stages typically take 2 years altogether, and imatinib is often continued even after this. If ALL comes back or doesn’t respond well to initial treatment, your oncologist may suggest switching to another therapy.

For GIST, how long you take imatinib may depend on the size and location of the tumor and your response to treatment. Some people take imatinib for several years and eventually stop if there are no signs of cancer. Others take it indefinitely to prevent GIST from coming back.

All that being said, you should continue to take imatinib until your oncologist tells you to stop. If you stop taking it too early, you may raise your risk of cancer coming back.

5. Is imatinib safe to take?

Overall, imatinib is a safe medication to take. But like all medications, it can still cause side effects.

Imatinib’s side effects often happen within the first 2 years of treatment, and some may get better over time. Some common imatinib side effects include:

• Tiredness

• Rash

• Swelling from fluid retention

• Belly pain

• Low blood counts

• Nausea and vomiting

• Bone pain

• Muscle cramps and pain

• Diarrhea

It's not recommended to take imatinib if you’re pregnant. You should only take it if your oncologist believes its potential benefits outweigh its risks to a developing fetus. Imatinib can cross the placenta and may cause harm to a fetus, including birth defects. Talk to your oncologist about the safety of taking imatinib while pregnant.

6. Are there any serious side effects of imatinib treatment?

While most imatinib side effects tend to be relatively mild and manageable, some rare and serious side effects can happen.

More serious side effects that can happen with imatinib may include:

• Heart problems, including heart failure

• Low levels of phosphate in the blood

• Underactive thyroid

• Immune system dysfunction (hypogammaglobulinemia)

• Skin changes

• Liver problems

• Lung inflammation

Side effects like these are infrequent and usually occur in less than 1% of people who take the medication. Speak to your oncologist if you have concerns about side effects of treatment with imatinib.

How to save on imatinib

There are ways to save on imatinib, which is available as both a brand-name and generic medication.

• Save with GoodRx. Generic imatinib’s price at certain pharmacies is as low as $44.00 with a free GoodRx discount. By comparison, the average cash price is about $7985.91.

• Save with a copay savings card. If you have commercial insurance, you may be eligible to pay as little as $25 for brand-name Gleevec using a savings card from the manufacturer. You may also be able to pay as little as $0 for generic imatinib from Teva.

Why trust our experts?

Written by:

Sonja Jacobsen, PharmD, BCPS, BCOP

Sonja Jacobsen, PharmD, BCPS, BCOP,  is a clinical oncology pharmacy specialist currently practicing in Seattle. She has been practicing as a pharmacist since 2015 and is licensed to practice in Washington state and North Carolina.

Edited by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Reviewed by:

Vanessa Carranza, PharmD

Vanessa Carranza, PharmD, is a pharmacist who has dedicated her career to the advancement of medical education for healthcare providers, patients, and caregivers, most notably in the oncology space.

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