Drug offers hope in battle against leukemia, other cancers
October 26, 1999
Web posted at: 12:15 a.m. EDT (0415 GMT)
LOS ANGELES (CNN) -- An experimental drug designed to combat chronic myelogenous leukemia, a common form of the adult cancer, has produced dramatic results in early clinical trials, according to a preliminary report released Monday.
Unlike traditional, toxic chemotherapy remedies, which kill both cancerous and healthy cells, the drug STI-571 specifically targets an enzyme found only in leukemia cells, meaning patients suffer minimal side effects. Some experts think the new approach could work for other cancers as well.
"This is a real home run," said principal researcher Dr. Charles Sawyers of the Jonsson Cancer Center at the University of California in Los Angeles. "Six or eight months ago, I would never have believed this."
In fighting chronic myelogenous leukemia, STI-571 attacks the common adult cancer by altering abnormal cell structure and reducing the white blood cell count.
In the Phase I trial, CML patients with early stages of the disease who failed to respond to traditional interferon treatment received STI-571 in pill form once a day. Patients experienced little or no toxicity, and most of those receiving doses at 200 mg or higher had white blood counts come down to normal.
Leukemia patient Virginia Garner, who did not respond to interferon, is enthusiastic about the experimental treatment. "I just have a feeling about this new drug that it's going to turn out to be something that everyone is going to be amazed at," she said.
Her physician agrees. "With this new therapy, I've seen re-growth of healthy cells and that's the first step toward achieving remission," said Dr. Douglas Blayney of the Wilshire Oncology Medical Group.
Perhaps most remarkable, at doses of 300 mg or more, researchers have seen the molecular cause of CML begin to disappear. CML is linked to a particular fusion protein created when two chromosomes switch pieces with the other, Sawyer said. The chromosome responsible for the fusion protein was undetectable after several months of STI-571 treatment.
Some Phase I subjects are still being treated, and Phase 2 trials are underway for CML patients with more advanced phases of the disease.
Novartis Pharmaceuticals Corporation is supporting the trials. The drug manufacturer is waiting Phase 2 results before deciding whether to seek approval from the U.S. Food and Drug Administration.
Other medical experts are optimistic about the preliminary results. "It's rare to see a real response" in early trials, said Dr. Harmon Eyre, chief medical officer of the American Cancer Society. "In this case, seeing very good responses early on with minimal toxicity is very exciting."
Eyre thinks the new treatment could extend beyond leukemia: "The concept of specifically approaching the cancer cells compared to a normal cell is very important and will have applications to other cancers."
Sawyer, who presented his findings at the American Medical Association's annual Science Reporters Conference in Los Angeles, declined to provide details on the preliminary data. Yet he plans to present formal results of the STI-571 clinical trials in early December.
CML most often occurs among middle-aged men and women. In the chronic phase, usually from three to five years, patients have a high white blood cell count, but generally have few symptoms. Afterwards the disease advances to the accelerated phase, characterized by rapid white blood cell growth. The end stage of the disease, known as the blast crisis, can be fatal within several months.
Medical Correspondent Rhonda Rowland contributed this report, written by Richard Stenger.
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Cancer Treatment Centers of America
Leukemia Research Foundation
Adult Myelogenous Leukemia
Jonsson Comprehensive Cancer Center at UCLA
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