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Approves Gleevec to Treat Leukemia
myelogenous leukemia (CML), one of four main types of leukemia,
strikes about 5,000 people every year. On average, patients
live 3-4 years after receiving a diagnosis of CML. Last week,
the FDA approved Gleevec (imatinib mesylate, also known as
STI 571) as an oral treatment for CML.
Gleevec has been shown to substantially reduce the level
of cancerous cells in the bone marrow and blood of treated
patients. In clinical trials, 90 percent of patients in
the first phase of CML went into remission within the first
six months of taking Gleevec. Of patients in the second
phase of CML, 63 percent went into remission with Gleevec.
The drug produced few side effects.
Additional studies need to be done to determine how long
the effects of this drug last, whether patients become
resistant to the drug, and, most importantly, whether Gleevec
can actually extend a patient's life.
Still, the results are promising. Currently, the only cure
for CML is a bone marrow transplant. Even if a patient
is lucky enough to find a marrow donor match, the procedure
is successful less than 2/3 of the time. Interferon, a
widely used treatment for CML, can extend a patient's life
for up to two years, but it has several serious side effects
and does not cure the disease. Gleevec may be used in patients
in the early stage of CML who do not respond to interferon
therapy, and in patients in the later stages of CML.
Most people with CML have a chromosomal abnormality, known
as the Philadelphia chromosome, in which portions of two
different chromosomes are switched. The result is the creation
of an abnormal protein that allows the uncontrolled production
of white blood cells, which can interfere with the function
of other organs in the body. Gleevec blocks a signal sent
out by the abnormal protein, thus blocking the rapid growth
of white blood cells.
The FDA's approval of the drug came after a surprisingly
months. Most drugs that, like Gleevec, are granted a priority
review, take six months to approve. The approval was based
on three separate studies that involved about 1,000 patients
with CML. The drug has generated enthusiasm in the medical
community because it targets a specific, cancer-causing
protein, without damaging other cells.
Scientists at an American Society of Clinical Oncology
meeting announced earlier this month that Gleevec had also
produced remission in 180 patients with advanced cases
of an intestinal cancer known as gastrointestinal stromal
tumor (GIST). Until now, GIST cancers have been incurable;
GIST patients normally die within one year of receiving
May 2001 Update