Experimental Drug Effective for Chronic Myeloid Leukemia

Editor’s note: The US Food and Drug Administration(FDA) today approved ponatanib under the brand name Iclusig to tread adults with chronic myeloid leukemia (CML) and a certain type of lymphoblastic leukemia (ALL), 2 rare blood and bone marrow diseases.

A small study of the experimental drug ponatanib has shown it is effective in treating chronic myeloid leukemia (CML) after other treatments have stopped working. If future studies confirm these results, this drug could hold great promise for patients who now have few good treatment options.

Current Treatments Often Stop Working

The mainstay of modern CML treatment are drugs called tyrosine kinase inhibitors. These drugs block the action of a protein that causes CML cells to grow and reproduce out of control.

There are 4 tyrosine kinase inhibitors (TKIs) currently approved to treat CML. The trouble is that in some patients, the CML becomes resistant to the specific TKI being used. Often, this means switching to another TKI.

But the leukemia cells in some patients develop a new mutation that makes them resistant to all of the approved TKIs. When that happens, other types of treatments, often with more severe side effects, must be used.

Ponatinib Effective when Other Drugs Fail

Ponatanib is a TKI that so far appears to work even in patients with CML that is resistant to other TKIs, and even CML with the mutation that makes all the other TKIs not work.

The new study tested ponatinib in 43 patients with chronic phase CML whose leukemia had gotten worse on treatment with at least one other TKI. The drug normalized blood counts in almost all of the patients, and induced a major cytogenetic response in most of them. Ponatanib worked just as well In the 12 patients whose CML cells had the mutation that makes other TKIs not work.

The results were published in the New England Journal of Medicine.

The most common side effects were skin problems (such as a rash, dry skin, and acne), joint and muscle aches, fatigue, and abnormal lab tests. One potentially serious side effect was the development of pancreatitis, an inflammation of the pancreas that can cause severe abdominal pain, nausea, and vomiting. This was more common in patients taking a high dose of the drug, and caused 2 patients to stop taking it altogether.

Although ponatinib shows a great deal of promise, more studies enrolling more patients are needed before it becomes available outside of clinical trials.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Ponatinib in Refractory Philadelphia Chromosome–Positive Leukemias. Published November 2012 in the New England Journal of Medicine. First author: Jorge E. Cortes, MD, MD Anderson Cancer Center, Houston.

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