Gleevec (Imatinib Mesylate) Questions and Answers
What is Gleevec?
Gleevec is a new type of cancer drug – the first of its kind developed to fight cancer by turning off an enzyme that causes cells to become cancerous and multiply.
What is Gleevec used for?
Gleevec is approved to treat a rare cancer called Chronic Myeloid Leukemia (CML), which affects between 5,000 and 8,000 patients each year.
What is Leukemia?
Leukemia is a type of cancer in which the bone marrow produces an excessive number of abnormal (leukemic) white blood cells. These abnormal cells suppress the production of normal white blood cells, which act to protect the body against infection.
What are the symptoms of CML?
In the early stage, patients may only be diagnosed through routine blood tests that show an increase in white blood cells. In later stages, patients experience infections, bleeding, fever, chills, sweats, weakness, fatigue and headaches.
What is different about CML?
CML worsens as it progresses from the chronic phase to the accelerated phase and the final phase called the blast crisis. The three phases are characterized by steadily increasing numbers of abnormal cells within the bone marrow and by spread of abnormal cells to sites outside of the bone marrow.
The three phases are:
Chronic phase: This phase last for about 4 to 5 years. Initially, patients in this phase usually have minor symptoms and their cancer is usually detected by routine blood tests. Most patients receive Interferon therapy alone or with other drugs. Patients can also be treated with bone marrow transplants.
Accelerated phase: This phase lasts from 6 to 18 months. The white blood cell count increases and the disease is harder to control with conventional treatments.
Myeloid blast crisis: This phase is the final phase of the disease and lasts about three to six months.
Why is this approval important? And how does Gleevec work?
Gleevec is the first drug of its kind to treat cancer. Its action is different than other cancer drugs in that it specifically targets an enzyme that allows CML cells to grow.
What are the advantages of Gleevec treatment over other cancer therapies?
One advantage of Gleevec is that it can be given by mouth instead of by injection. A second advantage is that CML seems to respond relatively quickly (within one to three months) to the drug. This response can be measured by tests that show that the blood count returns to a normal range or tests that measure cancer cells in the bone marrow. It is hoped that Gleevec has fewer serious side effects than other cancer drugs.
What are the side effects of Gleevec and how serious are they?
Commonly reported side effects include nausea, vomiting, muscle and joint pains, skin rash, diarrhea, heartburn, headache, and water retention (edema.) Although some of the serious side effects occur less frequently, severe side effects include severe fluid retention (edema) liver toxicity, and the potential for bleeding (hemorrhage) especially in the elderly.
What do patients need to know about using Gleevec?
If patients experience swelling or weight gain from water retention, they should inform their doctor and should be closely monitored. Because Gleevec interacts with many other medications, including over-the-counter medications, patients should inform their doctors as to all medications that they are taking.
What other treatments have been used to treat CML?
Several drugs have been used to treat CML including cancer drugs such as busulfan, hydroxyurea, and cytosine arabinoside (ara-C). Current therapy for the chronic phase of CML generally includes alpha-interferon with or without other drugs. Bone marrow transplant may be an option for some patients.
Who can be treated with this new drug?
Patients who are diagnosed with CML in the three phases of disease are eligible for treatment. The diagnosis is established by blood and bone marrow examination and by physical examination to detect possible involvement of the liver and spleen. When the bone marrow is examined, special tests are performed to demonstrate the Philadelphia chromosome (the specific marker of CML)
Is this the first example of a drug that targets an intracellular signaling molecule in cancer therapy approved by FDA?
How is Gleevec be taken?
Dosage and administration recommendations: Therapy should be initiated by a doctor experienced in the treatment of patients with chronic myeloid leukemia.
Gleevec should be taken with food and a large glass of water to minimize the risk of stomach gastrointestinal irritation.
The recommended dosage of Gleevec is 400 mg per day for patients in chronic phase CML and 600 mg per day for patients in accelerated phase or blast crisis. The prescribed dose should be administered orally, once daily with a meal and a large glass of water.
Treatment should be continued as long as the patient continues to benefit.
I’ve heard that this drug was called STI571? What does that mean?
Gleevec was given the name STI571 when it was under early development. STI stands for Signal Transduction Inhibitor and represents the action of the drug to inhibit enzymes called tyrosine kinase inhibitors. This targeted kinase is the protein produced by a DNA translocation (the "Philadelphia chromosome") that appears central to the CML disease process.
What if I am taking other drugs?
Gleevec interacts with many other drugs. In some cases Gleevec increases blood levels of these drugs which may increase side effects. In other cases Gleevec decreases blood levels of the drugs which may decrease effectiveness of treatment. Similarly, Gleevec blood levels may be increased or decreased by other drugs. This might increase Gleevec side effects or decrease effectiveness. Because of these potential drug-drug interactions the patient must discuss all of their medications with their doctor.