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Launching a ‘smart’ fight against leukemia: A new technology raises hope

Forty years ago, a leukemia diagnosis offered little room for hope. Only 14 percent of patients survived the disease five years after diagnosis. Today, nearly half of those who learn they have this cancer of the blood and bone marrow will survive at least five years. Although leukemia remains dire, the odds of beating the disease are constantly improving thanks to promising medical advances.

A closer look at leukemia

Leukemia occurs when the body overproduces white blood cells. Eventually, the white blood cells crowd the bone marrow, the body’s blood production center, and inhibit its ability to create healthy cells.

The two most common types of leukemia are myelogenous leukemia and lymphocytic leukemia. Both types may be acute or chronic. Fever, infections, weight loss and symptoms of anemia (fatigue, low exercise endurance, pallor) are symptoms common to all types of leukemia.

Treatment depends on the type of leukemia, but common options include chemotherapy, radiation, interferon (a drug that boosts the body’s immune system) and bone-marrow transplantation.

In 2001, researchers announced that a drug known as imatinib mesylate (Gleevec) appeared to have eliminated a form of myelogenous leukemia in two patients and led to unusually long remissions in others.

A medicinal ‘missile’

Termed a “smart bomb” because it attacks only leukemia cells and leaves normal cells unharmed, Gleevec emerged from decades of studying leukemia cells at their basic molecular level. By gaining knowledge and understanding of leukemia cells’ biological makeup, researchers were able to develop this missile-like drug. Specifically, they realized that blocking the action of tyrosine kinase, an abnormal enzyme responsible for the rapid reproduction of leukemia cells, could halt the disease’s progress. And because the drug spares healthy cells, it produces few side effects.

Chronic myelogenous leukemia (CML), a particularly fatal form of the disease, arises from a chromosomal defect that produces tyrosine kinase, not coincidentally the very enzyme Gleevec is designed to defuse. This drug, which is taken in capsule form, was initially used only to treat CML and a rare gastrointestinal tumor. But in late 2006, the U.S. Food and Drug Administration approved the use of Gleevec for five additional diseases, including four other cancers affecting blood cells. At the same time, the FDA noted that this medication has been linked to congestive heart failure in a few patients, so careful follow-up is essential.

Hopeful implications

The success of Gleevec affirms the path taken by many cancer researchers, and clinical trials are ongoing. In recent years, other researchers have been pursuing so-called “rational drug design,” which focuses on discovering how cancer cells differ from healthy cells and then developing drugs that attack those biological differences. As researchers strive to refine these smart technologies, the promise is that they can be adapted to conquer other types of leukemia as well as other devastating cancers.