FDA Approval: Imatinib (Gleevec) for Leukemia

Why 2001 still gets cited

Imatinib, sold as Gleevec, carries an Initial U.S. Approval date of 2001 on its FDA label. It is the drug most often named when people talk about targeted therapy arriving in the clinic.

The reason is not marketing. Chronic myeloid leukemia had a single, known molecular cause, and imatinib was built to block it. That match between a defect and a drug is the template the field has followed since.

NCI now lists imatinib as approved for a wide list. It includes Philadelphia chromosome positive chronic myeloid leukemia in adults and children, Philadelphia chromosome positive acute lymphoblastic leukemia, gastrointestinal stromal tumors that carry the KIT protein, dermatofibrosarcoma protuberans, certain myelodysplastic and myeloproliferative neoplasms with an abnormal PDGFR gene, chronic eosinophilic leukemia, hypereosinophilic syndrome, and aggressive systemic mastocytosis.

The defect the drug was built for

Most people with CML carry a change called the Philadelphia chromosome. Part of the DNA from one chromosome moves to another. NCI states the consequence directly: the bone marrow then makes a protein called tyrosine kinase, which drives too many stem cells to become white blood cells.

Two points people often get wrong. The Philadelphia chromosome is not inherited, and it is not passed from parent to child. And imatinib does not remove it. It blocks the protein the change produces.

Our overview of targeted therapy covers how this class works more broadly.

What CML looks like

CML is a slowly progressing disease of the blood and bone marrow. It usually appears during or after middle age and is rare in children.

Sometimes it causes no symptoms at all and turns up on a routine blood count.

When to get checked

NCI says to check with a doctor if you have:

• Fatigue, meaning feeling very tired.
• Weight loss for no known reason.
• Drenching night sweats.
• Fever.
• Pain or a feeling of fullness below the ribs on the left side.

That last one deserves attention. It usually reflects an enlarged spleen, which is a common finding in CML and not something to wait out.

There is no screening test for CML in people without symptoms.

How it is diagnosed

Blood and bone marrow tests make the diagnosis. A blood chemistry study measures substances released by organs into the blood. A bone marrow aspiration and biopsy removes marrow, blood, and a small piece of bone through a needle placed in the hipbone or breastbone, and a pathologist examines it.

Two tests then look for the Philadelphia chromosome itself. Cytogenetic analysis checks chromosomes for breaks, losses, rearrangements, or extras. FISH, short for fluorescence in situ hybridization, uses fluorescent DNA pieces that light up when they attach to specific genes or chromosome regions.

The same tests are used later to see how well treatment is working. That is a defining feature of CML care. Response is measured in the lab, not only on scans.

Phases, not stages

CML is classified by phase rather than stage, and the phase is defined by a number. Blast cells are immature blood cells.

• Chronic phase. Fewer than 10 percent of cells in blood and bone marrow are blasts.
• Accelerated phase. 10 to 19 percent are blasts.
• Blastic phase. 20 percent or more are blasts.

As blasts crowd the marrow, there is less room for healthy white cells, red cells, and platelets. That produces infections, anemia, easy bleeding, bone pain, and fullness below the ribs on the left.

A daily pill and a lab schedule

For chronic phase CML, NCI lists targeted therapy with asciminib, imatinib mesylate, nilotinib, dasatinib, or bosutinib, and allogeneic bone marrow or stem cell transplant. Allogeneic means the cells come from a donor.

For accelerated phase, NCI lists targeted therapy with bosutinib, or imatinib followed by allogeneic stem cell transplant.

Most people in chronic phase take a pill daily and have blood tests on a schedule to track the response. Our page on biomarker testing explains how those molecular results are read.

What the numbers look like now

These population figures describe a whole population and do not predict one person's course.

For chronic myeloid leukemia, NCI's SEER data put five-year relative survival at 71.1 percent for cases from 2016 to 2022, and the median age at diagnosis at 67. The American Cancer Society projects 9,650 new cases and 1,170 deaths for 2026.

CML is uncommon. It accounts for about 0.5 percent of new cancer cases and 0.2 percent of cancer deaths in the United States. That gap between incidence and mortality is the visible trace of what changed after 2001. Our page on leukemia sets CML alongside the other types.

What this approval cannot tell you

A 2001 approval does not mean the 2001 label. Indications were added over more than two decades, and dosing, monitoring, and the list of alternative drugs all changed with them.

It also does not mean every person with CML takes imatinib. Newer tyrosine kinase inhibitors exist, and choice depends on phase, other health conditions, side effects, and cost. Eligibility is defined by the current label, and whether it fits a particular person is a clinical decision.

Sources

• NCI, Imatinib Mesylate — https://www.cancer.gov/about-cancer/treatment/drugs/imatinibmesylate
• DailyMed, GLEEVEC (imatinib mesylate) label, Initial U.S. Approval 2001 — https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=211ef2da-2868-4a77-8055-1cb2cd78e24b
• NCI PDQ, Chronic Myeloid Leukemia Treatment (Patient Version) — https://www.cancer.gov/types/leukemia/patient/cml-treatment-pdq
• SEER Cancer Stat Facts, Chronic Myeloid Leukemia — https://seer.cancer.gov/statfacts/html/cmyl.html
• NCI, Leukemia — https://www.cancer.gov/types/leukemia

How this article was prepared

An AI-assisted editorial system helped prepare this page. No named medical reviewer has reviewed it unless one is listed.

The National Cancer Information Foundation publishes Cancer Explained. This page is for learning. It is not medical advice and does not suggest a test or treatment.

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