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FDA Approves Gleevec to Treat Leukemia
Chronic 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
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 short 2½ 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 their diagnosis.
May 2001 Update
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