Drug Holds Promise for Patients With a Type of Leukemia
Dec. 3, 1999 (Tuscaloosa, Ala) -- In a study described as a
"breakthrough" by a researcher at Oregon Health Sciences University,
investigators will report Sunday that 31 of 31 patients with chronic
myelogenous leukemia treated with an experimental pill went into total
Chronic myelogenous leukemia (CML) is a form of leukemia, or cancer of the
blood, that usually affects adults. It is treated with chemotherapy drugs and,
when possible, bone marrow transplantation. The chemotherapy agents work to
either kill the cancerous blood cells or keep them from multiplying. The
average survival after diagnosis is four years.
The new drug compound is known as STI-571. "Early clinical trials are
producing dramatic results with minimal side effects," Brian Druker, MD,
one of the researchers, tells WebMD. "Unlike chemotherapy, which kills both
normal and abnormal cells in an attempt to eradicate the cancer, the compound
STI-571 targets an enzyme found only in CML."
Druker, an associate professor of medicine at Oregon Health Sciences
University, points out that the enzyme is responsible for the overabundance of
white blood cells characteristic of chronic myelogenous leukemia and is present
in virtually all patients with CML.
The report, the results of collaboration with medical scientists at
University of Texas MD Anderson Cancer Center, the Jonsson Cancer Center at
UCLA, and Novartis Pharmaceuticals, is to be presented at the American Society
of Hematology annual meeting in New Orleans.
"It's sort of like a light switch that is stuck on," Druker
explains. "STI-571 targets that enzyme and inhibits its action."
The trial involved 31 CML patients who had failed to respond to standard
treatment for their leukemia. Once the STI-571 dosage of 300 mg or greater was
established, 31 of 31 patients had a complete normalization of their blood
"Even more remarkable, in some cases the molecular cause of the disease
seemed to disappear," Druker says.
The research may have implications for the treatment of other cancers.
"The potential significance of this research extends beyond
leukemia," says Druker. "One of the major goals of cancer research has
been to identify the differences between cancer cells and normal cells so that
these differences can be targeted with more effective and less toxic
treatments. That's exactly what we have been successfully doing in treating
Leading cancer experts characterized the results as "encouraging"
and "exciting," and as providing "new hope" for CML
"Their early data are very encouraging," says Richard Klausner, MD,
director of the National Cancer Institute (NCI). "While [it's] too soon to
evaluate the ultimate value of this agent for the standard clinical approach to
CML, I congratulate these investigators on pushing forward the field of
rationally targeted cancer therapy."
"The early evidence of effectiveness of agent STI-571 -- that is, the
specific inactivation of the cancer-causing protein in malignant cells --
heralds a new approach to leukemia therapy and perhaps that of other cancers as
well," says Marshall Lichtman, MD, executive vice president for research
and medical affairs of the Leukemia Society of America. "These preliminary
results should engender excitement for researchers and physicians battling
leukemia and new hope for affected patients."
The Leukemia Society of America helped support the research, as did Novartis
Pharmaceuticals and the NCI.
- In a small study on chronic myelogenous leukemia, all 31 patients went into
remission after taking a pill known as STI-571.
- The side effects of this drug are minimal, because it targets an enzyme
found only in CML and does not affect healthy cells.
- The implications of the study extend beyond leukemia, as many researchers
are trying to develop therapies that attack only cancerous cells.